The status of sea cucumbers in the Kingdom of Tonga ...

The status of sea cucumbers in the Kingdom of Tonga in 2016

Brad Moore, Pauline Bosserelle, Sione Mailau, Siaosi Vi, Siaosi Fonua, Tevita Havea, and Siola’a Malimali


Brad Moore Pauline Bosserelle Coastal Fisheries Programme, Pacific Community (SPC)

Sione Mailau, Siaosi Vi Siaosi Fonua, Tevita Havea, and Siola’a Malimali Ministry of Fisheries, Government of Tonga

Noumea, New Caledonia, 2017


i

© Pacific Community (SPC), and Ministry of Fisheries, Government of Tonga, 2017 All rights for commercial/for profit reproduction or translation, in any form, reserved. Permission to reproduce the document and/or translate in whole, in any form, whether for commercial/for profit or non-profit purposes, must be requested in writing. Original artwork may not be altered or separately published without permission.

Original text: English Pacific Community Cataloguing-in-publication data

Moore, Bradley The status of sea cucumbers in the Kingdom of Tonga in 2016 / Brad Moore, Pauline Bosserelle, Sione Mailau, Siaosi Vi, Siaosi Fonua, Tevita Havea and Siola’a Malimali

1. Sea cucumbers — Tonga. 2. Trepang fisheries — Tonga. 3. Holothurian populations — Tonga.

I. Moore, Bradley II. Bosserelle, Pauline III. Siaosi Vi, Mailau IV. Fonua, Siaosi V. Havea, Tevita VI. Malimali, Siola’a VII. Title VIII. Pacific Community IX. Tonga. Ministry of Fisheries

593.96099612

AACR2

ISBN: 978-982-00-1080-2

Prepared for publication and printed at SPC’s headquarters, B.P. D5, 98848 Nouméa Cedex, New Caledonia, 2017 www.spc.int

ii


Contents Acknowledgements

iv

Summary

1

Introduction

2

Sea cucumber resources

2

Sea cucumber fisheries in Tonga

3

Management of sea cucumbers in Tonga

5

This report

5

Methodology

6

Export production and value

6

In-water resource assessments

6

Data analysis and reporting

8

Results

9

Trends in export production and income for 2008–2014

9

In-water resource assessments

15

Discussion

42

Recommendations for management and monitoring

42

References

49

Appendix 1. Pacific regional reference densities for healtwhy stocks (from Pakoa et al. 2014).

50

Appendix 2. Comparison of survey coverage among the 2016 and previous surveys.

50

Appendix 3. Densities of sea cucumber species observed during manta tow surveys.

51

Appendix 4. Densities of sea cucumber species observed during reef benthos transects.

53

Appendix 5. Mean lengths of sea cucumber species observed at each site.

54

Appendix 6. A simplified approach to calculating harvestable stock estimates

56


iii

Acknowledgements The authors thank Tonga’s Ministry of Fisheries and the Australia’s Department of Foreign Affairs and Trade for their financial support during fieldwork and data analysis. Latu ‘Aisea, Tracy ‘Aisea, Poasi Ngaluafe, Sosefina Vili and Silika Ngahe provided much appreciated assistance with logistics in Tongatapu, Ha’apai and Vava’u. Lavinia Vaipuna, Poasi Ngaluafe, Mele Atuekaho and Tevita ‘Ahoafi provided trade data and useful discussions on Tonga’s sea cucumber fishery. Navneel Singh (Pacific Islander Junior Professional, SPC) assisted with the visualisation of trade data. Ian Bertram (Coastal Fisheries Science and Management Advisor, SPC) provided useful comments on an earlier draft of the report. We are grateful to Publication section for organising editing, publishing and printing services; to Kim Des Rochers for editing; the Information section including Constance Odiardo for the layout work.

Members of the survey team at Tongatapu (Photo: Brad Moore).

iv


Summary Sea cucumbers (mokohunu in Tongan) represent an important source of livelihood for the people of Tonga, yet the fishery has been one of ‘boom-and-bust’, characterised by a few years of heavy fishing pressure and relatively large harvests, and followed by years of very poor harvests and long-term moratoria to allow depleted stocks to recover. Most recently, a moratorium on harvesting and exporting sea cucumbers was imposed in October 2015 for a period of five years due to concerns over their current status, and to allow stocks to re-build. At the same time, Cabinet approved a decision to assign exclusive legal ownership and the right to farm, harvest, process and market sea cucumber resources to coastal communities that own special management areas, in close collaboration with the National Fisheries Council and the Government (Cabinet Decision No. 1159). This report presents information on the status of sea cucumber stocks shortly after the October 2015 moratorium went into effect, and is intended to serve as a baseline to assess the moratorium’s effectiveness and provide an update on the status of the fishery prior to implementing the moratorium. Information on the quantity of sea cucumbers exported, prices paid to fishers, and number of sea cucumber export licences issued for Vava’u, Ha’apai and Tongatapu for the period 2008–2014 was provided by the Ministry of Fisheries to facilitate an assessment of recent trends in the export fishery from these island groups. An examination of export data suggests that the sea cucumber fishery in Tonga went through its second boom-and-bust cycle in the period 2009–2013, with large exports in 2009 (367 t dried weight) and 2010 (313 t dried weight), and comparably smaller exports in 2011 (79 t dried weight), 2012 (68 t dried weight) and 2013 (56 t dried weight). Exports increased in 2014 (143 t dried weight) relative to the two previous years, likely as a result of fishers harvesting large amounts of sea cucumber in anticipation of the 2015 moratorium. Changes in catch composition were also observed in 2008–2013, with declines in the proportion of medium-value species, and increases in the proportion of lowvalue species, evident in total exports at each of the three island groups. Based on information on the average prices paid to fishers for each exported species, total earnings of sea cucumber fishers over the period 2008–2014 were estimated to be around Tonga pa’anga (TOP) 90 million, ranging from TOP 3.1 million in 2008 to TOP 31.9 million in 2009. In-water surveys were conducted at Vava’u, Ha’apai and Tongatapu in October–November 2016 to assess the status of sea cucumber stocks. In total, 264 stations, covering approximately 436 km2, were surveyed during the 2016 assessment. Assessments were conducted in areas open to fishing (‘open’ areas) and within special management areas (SMAs). Four survey methods were used in the 2016 survey, including two ‘primary’ survey approaches (manta tow and reef benthos transects), which were used to provide data on species presence, relative abundance, density (individuals per hectare) and length; and two ‘secondary’ approaches (sea cucumber day searches, which are timed scuba dives conducted during daylight hours) and reef front searches (timed swims conducted in daylight hours), which were used to provide data on species presence and length. In-water assessments revealed sea cucumber populations at each of the three island groups to be in a poor state. At each island group, sea cucumber assemblages were dominated by low-value lollyfish (Holothuria atra) and, to a lesser extent, greenfish (Stichopus chloronotus), pinkfish (Holothuria edulis), snakefish (Holothuria coluber), curryfish (Stichopus herrmanni) and brown sandfish (Bohadschia vitiensis). High-value and very high-value species were rarely encountered. Densities of individual species were generally well below regional reference densities for healthy stocks for both manta tow and reef benthos transect assessment techniques at each site. In contrast to community perceptions, SMAs were found to have little overall positive benefit on sea cucumber densities, with few differences observed in overall density or densities of individual species between stations in open areas and SMAs. The mean lengths of a number of species had declined since previous surveys, likely resulting from recent heavy fishing pressure and the removal of larger, more valuable specimens for the export trade. The current state of sea cucumber stocks and large quota over-runs suggest that the management strategies in the Tonga National Sea Cucumber Fishery Management and Development Plan, or at least their implementation, failed to maintain harvests to a sustainable level and should thus be reviewed. In addition, ongoing monitoring is required to assess the effect of the most recent (2015) moratorium and determine if stocks have recovered sufficiently to sustain further harvests. A comprehensive survey should be conducted towards the end of the current five-year closure at each island group. To allow for a comparison over time without spatial, temporal or methodological bias, survey stations, the timing of the survey and survey methodologies should match those of the 2016 assessment. In addition, efforts should be made by the Ministry of Fisheries to monitor illegal harvests and exports of sea cucumber resources during the current moratorium.


1

Introduction Sea cucumber resources The Kingdom of Tonga (hereafter referred to as Tonga) is a Polynesian archipelago consisting of 36 inhabited and 134 uninhabited islands. Tonga has an estimated land area of 749 km2 and an exclusive economic zone of 676,401 km2. The country consists of three main island groups – Vava’u, Ha’apai and Tongatapu – that extend in a roughly north–south direction (Fig. 1). Tonga is home to approximately 103,252 people, with the majority of people (around 73% of the total population) living on Tongatapu, the location of the nation’s capital Nuku’alofa (Tonga Department of Statistics 2015).

Figure 1. The three main island groups of Tonga.

Sea cucumbers (Echinodermata: Holothuroidea) represent an important source of food and livelihood for the people of Tonga. Sea cucumbers are found in tropical to polar regions across the globe, from intertidal waters to deep ocean areas. Approximately 1,200 species have been described worldwide to date, with new species being described each year. Sea cucumber biology is complex, and can vary dramatically among species. Some species are fast-growing, such as sandfish (Holothuria scabra), which can reach reproductive size at around two years of age at 160 mm (Conand and Sloan 1989). However, most species are relatively slow-growing and long-lived. For example, black teatfish (Holothuria whitmaei), white teatfish (H. fuscogilva) and prickly redfish (Thelenota ananas) can reportedly live for around 10–15 years (Plagányi et al. 2015). Sea cucumbers reproduce by sexual means (spawning and egg fertilisation), although some species can also reproduce by asexual means (vegetative regeneration by splitting; Conand 2004). Most species are dioecious (i.e. they have separate sexes). Spawning of species in the Pacific Islands region typically occurs in the summer months, although some species (e.g. Holothuria whitmaei) have

2


an extended spawning season that includes winter months (Conand 1993; Shiell and Uthicke 2006). Successful egg fertilisation relies on having a good aggregation of adults in close proximity to each other. Fertilised eggs hatch and planktonic larval stages can spend several weeks in the open ocean before settling on suitable habitat. Recent genetic studies for some species suggest that dispersal is quite limited, meaning population replenishment is reliant on having good local numbers of mature individuals (Purcell 2010). Most sea cucumbers are deposit feeders, feeding by ingesting sand and detritus and digesting the bacteria and fungi attached to the sediment (Purcell 2010). Through this action they help turn over sediment and recycle nutrients locked in organic matter, thus decreasing organic matter content and reducing the potential for algal blooms (MacTavish et al. 2012). Many species also exhibit burrowing behaviour, thereby playing a key role in bioturbation and oxygenation of sediments (MacTavish et al. 2012).

Sea cucumber fisheries in Tonga Of the approximately 1,200 species of sea cucumber that have been described globally, 23 species have been previously recorded in Tonga (Table 1). In Tonga, sea cucumbers are harvested by three sectors: 1) the subsistence fishery for home consumption, 2) the domestic commercial fishery for sale at local markets and roadside stalls, and 3) the commercial export fishery to supply the beche-de-mer trade. Tonga is one of the few Pacific Island nations where sea cucumbers are consumed locally (Pakoa et al. 2013a). The body wall and viscera of a number of species are consumed, including lollyfish, snakefish, brown sandfish, chalkfish, curryfish and dragonfish. The harvest and sale of sea cucumbers for the domestic market is an increasing source of income for women fishers who glean sea cucumbers from shallow intertidal and subtidal areas (Pakoa et al. 2013a).

Table 1. Sea cucumber species reported from Tonga (adapted from Pakoa et al. 2013a). Common name

Scientific name

Tongan name

Amberfish

Thelenota anax

Mokohunu saianiti

Black teatfish

Holothuria whitmaei

Huhuvalu ‘uli’uli

Brown curryfish

Stichopus vastus

Lomu

Brown sandfish

Bohadschia vitiensis

Mula

Chalkfish

Bohadschia marmorata

Finemotua

Curryfish

Stichopus herrmanni

Lomu

Deepwater redfish

Actinopyga echinites

Telehea loloto

Deepwater spiky redfish

Actinopyga sp. affn. flammea

Telehea loloto

Dragonfish

Stichopus horrens

Lomu

Elephant trunkfish

Holothuria fuscopunctata

Elefanite

Golden sandfish

Holothuria lessoni

Nga’ito

Greenfish

Stichopus chloronotus

Holomumu

Hairy blackfish

Actinopyga miliaris

Lolo fulufulu

Lollyfish

Holothuria atra

Loli

Pinkfish

Holothuria edulis

Loli pingiki

Prickly redfish

Thelenota ananas

Pulukalia

Snakefish

Holothuria coluber

Te’epupulu

Stonefish

Actinopyga lecanora

Telehea maka

Surf redfish

Actinopyga mauritiana

Telehea kula

Tigerfish

Bohadschia argus

Matamata

White snakefish

Holothuria leucospilota

Te’epupulu

White teatfish

Holothuria fuscogilva

Huhuvalu hinehina

1

As reviewed by Pakoa et al. (2013a), the sea cucumber export fishery in Tonga in 2011 showed the familiar pattern of boom-and-bust, In this survey we consider that Holothuria lessoni, commonly referred to as golden sandfish, includes the following species: Holothuria lessoni, H. scabra var. versicolor and H. versicolor.

1


3

which is typical of overexploited fisheries and ineffective management. Historically, many sea cucumber fishers in Tonga would dry-process their products and sell directly to exporters, although this resulted in poor or inconsistent product quality. Accordingly, in recent times, the majority of sea cucumbers harvested for export in Tonga are sold unprocessed by fishers to licensed processors for processing into a fully dried product (Pakoa et al. 2013a). Harvest records of the export fishery began in the 1980s, although it is likely that sea cucumbers were harvested for export purposes well before this time. Between 1984 to 1990, Tonga recorded few sea cucumber exports, with total reported exports for this period equating to 8.9 metric tonnes (t), and average annual reported exports over this period of 1.3 t, with a peak export of 5 t in 1986 (Fig. 2). Reported exports increased substantially from 1991 to 1995, after an assessment in 1990 found that a commercial fishery was viable (Preston and Lokani 1990). Total reported exports for the 1991–1995 period equated to 250 t, with an average annual reported export over this period of 50 t and a peak export of 70 t in 1995 (Fig. 2). No data were recorded for 1996. A resource assessment conducted in 1996 (Lokani et al. 1996) recommended a 10-year moratorium on the sea cucumber fishery in Tonga because stocks were found to have declined dramatically from 1990 levels. This recommendation was approved by Cabinet and the fishery was officially closed in the last quarter of 1997. Approximately 10 t were exported in 1997 prior to the implementation of the first moratorium in 1997. As reported by Pakoa et al. (2013a), this represented the first boom-and-bust period for the sea cucumber fishery in Tonga. The fishery re-opened in 2008, with reported exports of 14.8 t occurring in this year. A detailed assessment of current trends in sea cucumber production and value over the period 2008 to 2014 is presented in the Results section of this report. Briefly, exports hit a record high of approximately 370 t in 2009, with slightly lower exports of 312 t in 2010, although harvests in both 2009 and 2010 greatly exceeded the quota imposed by the Ministry of Fisheries for these years (204 t and 212 t, respectively). These numbers are indicative of both heavy harvest pressure on re-establishing populations and a lack of monitoring and enforcement of the quota system. Following these large harvests, exports dropped significantly to 80 t in 2011, 68 t in 2012, and 56 t in 2013 (Fig. 2). In-water surveys conducted by staff from the Ministry of Fisheries and the Pacific Community (SPC) in Tongatapu and Vava’u in 2010 (Pakoa et al. 2013a), and the Ha’apai group in 2014 (Pakoa et al. unpublished data) revealed densities of most species to be extremely low, and well below regional reference densities for healthy stocks (Pakoa et al. 2014), likely due to both heavy recent harvests and inadequate re-building of stocks during the first moratorium (Pakoa et al. 2013a). Based on these results, it was recommended that the sea cucumber fishery be closed for a further five years to allow stocks to re-build (Bertram et al. 2015). This recommendation was approved by Cabinet and the sea cucumber fishery was officially closed for the second time in October 2015. In the year before the moratorium (2014), harvests increased to around 143 t (Fig. 2).

400 350 300 Quantity (t)

250 200 150 100

0

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

50

Year Figure 2. Trends in total reported sea cucumber exports from Vava’u, Ha’apai and Tongatapu (combined), 1984–2014.

4


Management of sea cucumbers in Tonga As with many other Pacific Island countries and territories, few formal management arrangements were in place for the sea cucumber fishery in Tonga prior to 1998. Although strongly discouraged by several authors (e.g. Preston and Lokani 1990), the use of scuba was not restricted in the early days of the fishery and many fishers used it to target deepwater species (Pakoa et al. 2013a). The Tonga National Sea Cucumber Fishery Management and Development Plan (hereafter the Plan) was developed in 2007, prior to the end of the first moratorium. Several measures were included in the Plan in order to ensure the sustainable management of the sea cucumber fishery in Tonga. These measures included establishing a six-month closed season (1 October–31 March) to encompass the spawning season for most species; species and island group export quotas; species-specific size limits; restrictions on harvest methods, including a ban on using underwater breathing apparatus (including scuba and hookah) for fishing; and a limit on the number of export licences issued. In addition, under the Plan, fishers must have registered with the Fisheries Division (now the Ministry of Fisheries) in order to harvest sea cucumbers for commercial gain. At the same time as approving the 2015 moratorium, Cabinet approved a recommendation to implement several alternate options for the management of the sea cucumber fishery in Tonga, including for the Ministry of Fisheries to cooperate with the Office of the Attorney General to cancel the existing system of registration of sea cucumber processors for export and, at the same time, to amend the legislation and regulations on the sea cucumber fishery to: 1) assign exclusive legal ownership of sea cucumbers that inhabit the country’s coastal waters to coastal communities that own special management areas; 2) assign exclusive legal right to develop and manage sea cucumber resources to coastal communities that own special management area in close collaboration with the Government; and 3) assign exclusive legal right to farm, harvest, process and market sea cucumber resources to coastal communities that own special management areas in close collaboration with the National Fisheries Council and the Government. The Cabinet decision further states that the Ministry of Fisheries should undertake a stock survey during the third year of the moratorium, and, if it is revealed that sea cucumber stocks have recovered sufficiently to absorb sustainable harvesting, that Cabinet shall be informed to declare the early termination of the moratorium and re-open the fishery.

This report In this report, we provide an update on the status of sea cucumber stocks in Vava’u, Ha’apai and Tongatapu. We build on the trade analysis conducted by Pakoa et al. (2013a), compiling updated trade information for 2008 to 2014 for the three island groups. We present the current status of sea cucumber populations based on results of in-water assessments conducted at each of the three island groups in October and November 2016, one year after the moratorium came into effect, to provide a baseline from which to assess the effectiveness of the moratorium. Finally, we provide recommendations for improved management and monitoring of Tonga’s sea cucumber resources in light of the recent Cabinet Decision No. 1159.


5

Methodology Export production and value Trade data collected by the Ministry of Fisheries includes export quantity (dry weight, in kg) by species and island group, price paid to fishers, and the number of export licences issued. Export data, collated by sea cucumber processors and exporters as a requirement of their licencing conditions, were entered into the Ministry of Fisheries’ sea cucumber exports database. Data for 2008–2014 were extracted to facilitate an assessment of production by the three island groups. Data were examined in terms of total exports, exports by value category (Table 2) and export of individual species. To determine income to fishing communities, export data for processed sea cucumber were first converted to wet weight for each species using published conversion ratios (Table 2). These wet weights were then multiplied by average price paid to fishers2 per species using information supplied by the Ministry of Fisheries to calculate the income generated through sea cucumber harvesting (Table 2). Table 2. Value categories3, weight conversion factors and average prices paid to fishers for sea cucumber species exported from Tonga in 2008–2014. TOP = Tongan pa’anga Value category

Weight wet-dry weight conversion factor

Average price paid to fishers (TOP)

M

0.05

2.13

Black teatfish

H

0.10

16.88

Brown sandfish

M

0.04

1.88

Chalkfish

M

0.06

4.08

Curryfish

M

0.04

2.50

Deepwater redfish

H

0.105

3.50

Dragonfish

M

0.04

0.92*

Elephant trunkfish

L

0.13

2.38

Flowerfish

M

0.04

4.08

Golden sandfish

VH

0.08

48.13

Greenfish

H

0.03

10.25

Species Amberfish

Hairy blackfish

M

0.06

4.08

Lollyfish

L

0.05

0.78*

Pinkfish

M

0.04

0.78*

Prickly redfish

H

0.07

9.88

Snakefish

M

0.04

1.94*

Stonefish

M

0.05

10.25

Surf redfish

H

0.06

4.00

Tigerfish

M

0.04

3.63

White teatfish

VH

0.09

48.13

* Denotes species sold by the bucket. An average bucket was deemed to be 22.5 kg in weight.

In-water resource assessments In-water surveys were conducted at Vava’u, Ha’apai and Tongatapu between 26 October and 30 November 2016 to provide an indication of the current status of sea cucumber stocks. The survey used standardised SPC methodologies (see Pakoa et al. 2014), and generally matched the methodology and locations of surveys by Pakoa et al. (2013a; for surveys in Vava’u and Tongatapu in 2010–2011) and Pakoa et al. (unpublished; for surveys in Ha’apai in 2014), where appropriate. In addition, survey stations were established in both areas of open access to fishing (open areas) and within special management areas (SMAs) to assess the performance of SMAs on sea cucumber stocks. The survey involved both broad- and fine-scale assessment techniques, described below, covering different habitats and providing different degrees of precision and information. Prices paid to fishers for chalkfish, flowerfish, golden sandfish, greenfish and hairy blackfish were unknown. For chalkfish, flowerfish and hairy blackfish, the average price of the medium-value category of species sold individually was used (TOP 4.08). For golden sandfish, the average price of the very high-value category of species sold individually was used (TOP 48.13). For greenfish, the average price of the high-value category of species sold individually was used (TOP 10.25). 3 From Pakoa et al. (2013a; 2013b); L = Low, M = Medium, H = High, VH = Very high. 2

6


Manta tow surveys Manta tows were used to provide a broad-scale assessment of species presence, abundance and density over relatively large areas within a short timeframe. This survey method used a snorkeler who was towed behind a boat on a manta board at an average speed of approximately 4 km/hour. Each tow replicate was 300 m in length with a 2-m observation belt, and was calibrated using the odometer function within the trip computer option of a Garmin 76Map GPS. A single manta tow station consisted of six 300 m x 2 m replicate transects (Fig. 3), with the start and end GPS positions of each transect recorded to an accuracy of < 5 m. All large, sedentary invertebrates observed within each transect were identified to species level and enumerated.

Sea cucumber day search Sea cucumber day searches were used to provide information on the presence and size (length) of sea cucumbers and other large sedentary invertebrates in deeper waters (typically 7–30 m). Stations were surveyed by two scuba divers swimming parallel to one another, and consisted of six replicate transects of 5 minutes search duration (Fig. 3). All large, sedentary invertebrates observed within the 5-minute search period for each replicate were identified to species level and enumerated.

Reef front timed swims Reef front timed swims were used to provide information on the presence of sea cucumbers and other large, sedentary invertebrates in shallow water reef slopes where manta tows were unsuitable (e.g. due to limitation in the lengths of reefs). Each station consisted of six parallel replicate transects of 5 minutes search duration along the reef edge. Stations were surveyed by two snorkelers swimming parallel to one another (Fig. 3). All large, sedentary invertebrate species encountered were identified to species level and enumerated.

Reef benthos transects Reef benthos transects were done to provide information on presence, abundance, density and size (length) of invertebrate species at fine spatial scales. Each station consisted of six parallel 40 m x 1 m replicate transects. Stations were surveyed by two snorkelers swimming parallel to one another (Fig. 3). All large, sedentary invertebrate species encountered were identified to species level, enumerated and measured.

Figure 3. Diagrammatic representation of the four invertebrate survey methods used during in-water assessments in Tonga: manta tow (top left), sea cucumber day search (top right), reef front swims (bottom left) and reef benthos transects (bottom right). Source: Pakoa et al. 2014.


7

Data analysis and reporting In-water assessment data were processed and analysed using SPC’s Reef Fisheries Integrated Databased (RFID). Training for Ministry of Fisheries staff in RFID took place at the completion of the field survey to build staff capacity in data entry, extraction and analysis. In this report, assessments of the status of sea cucumber resources has been based on fishery status indicators described in Friedman et al. (2008) and Pakoa et al. (2014): 1) species richness – the number species observed at each island group; 2) relative abundance – how abundant a species is relative to other species; 3) cumulative density – the sum of all sea cucumbers observed at a stations, irrespective of species; 4) mean density per station (ind/ha) ± standard error (SE) for individual species; 5) mean length (±SE); 6) length frequency of key species. Where possible, data were compared between management regimes (i.e. areas open to fishing vs. SMAs), and against that from previous assessments (e.g. Pakoa et al. 2013a for Vava’u and Tongatapu; Pakoa et al. unpublished data, and Lokani et al. 1996 for Ha’apai). Because the small areas of individual SMAs limited the number of stations that could be established in each SMA, data for SMAs were pooled. Density data were additionally compared with reference densities for healthy sea cucumber stocks developed by SPC (Pakoa et al. 2014, Appendix 1). These reference densities were calculated from the upper 25% of mean densities from survey work by SPC at 90 sites across the Pacific Islands region (Pakoa et al. 2014). Mean lengths were compared against those obtained in previous surveys (Pakoa et al. 2013a) for Vava’u and Tongatapu, and Pakoa et al. (unpublished data) for Ha’apai, regional common lengths, and Tongan minimum legal harvest lengths (where imposed). Length frequencies of key indicator species were evaluated with respect to minimum legal harvest lengths. Length frequencies of lollyfish, for which good numbers of measurements were obtained, were compared between open areas and SMAs at each island group.

8


Results Trends in export production and income for 2008–2014 Export licences and Government revenue The number of export licences allocated per fishing season was capped at nine in the Tonga National Sea Cucumber Fishery Management and Development Plan. In 2008, eight licences were issued at an annual licence fee of TOP 2,910 per licence. Export licences increased to 24 in 2009 and 22 in 2010, and dropped to 12 in 2011, 9 in 2013 and 8 in 2014 (Table 3). Annual licence fees were raised in 2010 to TOP 29,451, with the intention of forcing a reduction in the number of exporters by limiting licences to those who could afford the high fees. The increased licence fee disadvantaged some companies, particularly those owned by Tongan nationals, because they could not afford the higher licence fee (Poasi Ngaluafe, Principal Fisheries Officer, Ministry of Fisheries, pers. comm.). Export operators were then dominated by foreigners who could afford higher licence fees, mainly Chinese nationals, and many of these individuals are in joint venture arrangements with local partners (Poasi Ngaluafe, Principal Fisheries Officer, Ministry of Fisheries, pers. comm.). Income generated by the Government through licencing fines ranged from TOP 23,280 to TOP 647,922 (Table 3). Table 3. Sea cucumber licence fees, number of licences issued and estimated value of sea cucumber exports from Tonga, 2008–2014. Year

Licence fee (TOP)

No. of export licences issued

Total fees (TOP)

2008

2,910

8

23,280

2009

2,910

24

69,840

2010

29,451

22

647,922

2011

29,451

12

353,412

2012

29,451

10

294,510

2013

29,451

9

265,059

2014

29,451

8

235,608

Production Quota amounts and actual total export quantities (in tonnes) from the period 2008–2014 are presented in Figure 4 and Figure 5. Exports were modest in 2008, with only 15 t harvested. These low harvests likely reflect the short time frame of the harvest season in this year (between one and two months) (Pakoa et al. 2013a), and a lack of knowledge of the opening of the fishery following the moratorium. Harvests increased significantly in 2009–2010, with exports of 367 t reported for 2009 (representing a quota over-run of 163 t dry weight) and exports of 313 t reported for 2010 (over-run of 101 t dry weight) (Fig. 4). In 2009, the harvest from Tongatapu alone (200 t) almost exceeded the national quota (204 t) (Fig. 5). Harvests then dropped significantly in 2011–2013, with exports failing to meet the reduced quotas in both 2011 and 2012 (Fig. 4). Harvests increased in 2014, particularly at Ha’apai and Tongatapu, with a total harvest of 143 t achieved in this year. This increase was likely due to fishers anticipating the closure and increasing their fishing effort during the open season, rather than a result of an increase in stock sizes. According to Ministry of Fisheries staff, there were no exports of sea cucumbers in 2015 prior to the moratorium coming into effect in October of that year (Lavinia Vaipuna, Head of ICT Section, Ministry of Fisheries, pers. comm.). 400

Total quota

350

Amount exported

Exports (in t)

300 250 200 150 100 50 0

2008

2009

2010

2011

2012

2013

2014

Year

Figure 4. Sea cucumber export quotas and actual exports per year (dry weight, in t) from Tonga, 2008–2014. Note: No quota was in place for the 2013 and 2014 harvest seasons. The status of sea cucumbers in the Kingdom of Tonga in 2016

9

400 350

Tongatapu

Ha'apai

Vava'u

2013

2014

Exports (in t)

300 250 200 150 100 50 0

2008

2009

2010

2011

2012

Year Figure 5. Sea cucumber exports by island group per year, 2008–2014 (dry weight, in t).

Changes over time in the composition of species harvested are common in multi-species sea cucumber fisheries. Typically, very high-, high- and medium-value species are targeted in the early years of exploitation, followed by lower-value species as higher-value species become depleted. Often, higher-value species occur at lower relative densities than species of lower value, leading to rapid reductions in density across fishing grounds. While a lack of data from the early years of the fishery (i.e. up to 1997) precludes a detailed examination of these trends, catch compositions from Vava’u, Ha’apai and Tongatapu for the period 2008–2014 generally follow this pattern, with declines in the proportion of medium-value species, and increases in the proportion of low-value species, evident in total exports at each of the three island groups (Fig. 6).

10


Island group Ha'apai

Tongatapu

2011 2012 2013 2014

Year

2010

2009

2008

Vava'u

Low Low

Medium Medium

High High

Very Very High high

Figure 6. Annual trends in export composition (proportion of dry weight) by value category for each island group.


11

Value to fishers Due to the lack of export price information, the value of the sea cucumber fishery to the country is difficult to estimate. However, average prices paid to fishers for fresh unprocessed sea cucumbers are available (Table 2) and these were used to provide an estimate of the income fishers derived from this fishery. Based on average price information, the total earnings by sea cucumber fishers over the period 2008–2014 were estimated at approximately TOP 90 million, ranging from TOP 3.1 million in 2008 to TOP 31.9 million in 2009 (Fig. 7). A breakdown of the estimated earnings of fishing communities, by island group and value category, and based on average price information provided by the Ministry of Fisheries, is provided in Figure 8. A considerable increase in exports and earnings was evident in Ha’apai and Tongatapu in 2014 relative to previous years (Fig. 5 and Fig. 8), largely resulting from increased targeting of the very high-value white teatfish; high-value black teatfish, greenfish, prickly redfish and surf redfish; medium-value amberfish, stonefish and hairy blackfish; and low-value elephant trunkfish and lollyfish at these locations (Fig. 9).

Estimated earnings (TOP)

35 000 000 30 000 000 25 000 000 20 000 000 15 000 000 10 000 000 5 000 000 0

2008

2009

2010

2011

2012

2013

2014

Year Figure 7. Estimated total earnings per year for sea cucumber fishers in Vava’u, Ha’apai and Tongatapu combined. TOP = Tongan pa’anga

12


Estimated Estimated earnings Estimated earnings (TOP) earnings (TOP) (TOP)

20 000 000 20 000 000 15 000 000 20 000 000 15 000 000 10 000 000 15 000 000


Medium value

High value Low value

Very highvalue value Medium

Low High value value

Medium Very highvalue value

High value

Very high value

10 000 000 5 000 000 10 000 000 5 000 000 0 5 000 000 0 0 20 000 000 20 000 000 15 000 000 20 000 000 15 000 000 10 000 000 15 000 000

2008

2009

2010

2011

2012

2013

2014

2008

2009

2010

Year 2011

2012

2013

2014

2009

2010

b) Ha'apai

Year 2011 2012 Low value Year High value Low value

b) Ha'apai



High value

Very high value

2008 b) Ha'apai

2013 2014 Medium value Very highvalue value Medium

10 000 000 5 000 000 10 000 000 5 000 000 0 5 000 000 0 0 20 000 000


Low value

20 000 000 15 000 000 20 000 000 15 000 000 10 000 000 15 000 000

2008

2009

2010

2011

2012

2013

2014

2008

2009

2010

Year 2011

2012

2013

2014

2008 2009 c) Tongatapu

2010

Year 2011 2012 Low value Year

2013 2014 Medium value

c) Tongatapu

High value Low value

Very highvalue value Medium

c) Tongatapu



High value

Very high value

10 000 000 5 000 000 10 000 000 5 000 000 0 5 000 000 0 0

2008

2009

2010

2011

2012

2013

2014

2008

2009

2010

Year 2011

2012

2013

2014

2008

2009

2010

Year 2011

2012

2013

2014

Year Figure 8. Estimated earnings of sea cucumber fishers in a) Vava’u, b) Ha’apai and c) Tongatapu, 2008–2014. TOP = Tongan pa’anga


13

8000 7000

Ha'apai

6000

Tongatapu

5000 4000 3000

b) Black teatfish

Vava'u Ha'apai

5000

Quantity (kg)

Quantity (kg)

6000

Vava'u

a) Amberfish

Tongatapu

4000 3000 2000

2000 1000

1000 0

12000

2008

2009

2010

2011 Year

2012

2013

c) Elephant trunkfish

5000

Vava'u Ha'apai

10000 8000 6000 4000

4000

2008

2009

2010

2011 Year

2012

2013

e) Hairy blackfish

Ha'apai Tongatapu

2008

2009

2010

2011 Year

2013

f) Lollyfish

2014

Vava'u

Tongatapu

20000 15000 10000 5000

2008

2009

2010

2011 Year

2012

2013

g) Prickly redfish

0

2014

10000

Vava'u Ha'apai

2000

Quantity (kg)

1500 1000

2008

2009

2010

2011 Year

2012

2013

h) Stonefish

2014

Vava'u Ha'apai

8000

Tongatapu

Tongatapu

6000 4000 2000

500

2008

2009

2010

2011 Year

2012

2013

i) Surf redfish

0

2014

12000

Vava'u Ha'apai

10000

Tongatapu

8000 6000

2008

2009

2010

2011 Year

2012

2013

j) White teatfish

2014

Vava'u Ha'apai

10000

Quantity (kg)

12000

4000

Tongatapu

8000 6000 4000 2000

2000

2008

2009

2010

2011 Year

2012

2013

2014

0

2008

2009

2010

2011 Year

Figure 9. Exports (in kg) of key sea cucumber species by island group, 2008–2014.

14

2012

25000

500

Quantity (kg)

Vava'u

Ha'apai

1000

Quantity (kg)

d) Greenfish

2014

Tongatapu

1500

0

2013

30000

2000

14000

2012

Ha'apai

2500

0

2011 Year

2000

35000

Quantity (kg)

Quantity (kg)

3000

2500

2010

3000

0

2014

Vava'u

3500

0

2009

1000

2000 0

2008

4000

Tongatapu Quantity (kg)

Quantity (kg)

0

2014


2012

2013

2014

In-water resource assessments Survey coverage In total, 264 survey stations, covering approximately 436 km2, were surveyed during the 2016 assessment (all methods combined) (Figs. 10, 11, 12, 13). A breakdown of the number of stations and area surveyed, by survey method, is presented as Table 4. There were 62 manta tow stations (19 stations surveyed in Vava’u, 28 surveyed in Ha’apai and 15 surveyed in Tongatapu), 61 sea cucumber day search (dive) stations (19 in Vava’u, 21 in Ha’apai and 21 in Tongatapu), 20 reef front search stations (15 in Vava’u and 5 in Tongatapu) and 121 reef benthos transect stations (30 in Vava’u, 43 in Ha’apai and 48 in Tongatapu) (Table 4). The number of stations surveyed in 2016 represents a slight increase from the previous surveys of Pakoa et al. (2013a) and Pakoa et al. (unpublished) in order to extend data collection in each island group and to cover a range of habitat types, thus facilitating the detection of less common species (see Appendix 2 for a comparison of coverage among these surveys).

Table 4. The number of survey stations and area surveyed for each method during the 2016 assessment. Method

Vava’u Open

Ha’apai SMA

Open

Tongatapu SMA

Open

SMA

Manta tow No. stations Area surveyed

16

3

57,000 m

2

17

11

13

2

10,800 m

61,200 m

39,600 m

46,800 m

7,200 m2

15

13

8

16

5

2

2

2

2

Sea cucumber day search (SCDS)* No. stations Area surveyed

4 7,776 m

2

29,160 m

25,272 m

15,552 m

31,104 m

9,720 m2

10

0

0

2

3

2

2

2

2

Reef front search (RFS)** No. stations Area surveyed

5 16,440 m

2

32,880 m

2

0m

2

0m

2

2

6,576 m

9,864 m2

Reef benthos transects (RBt) No. stations Area surveyed Total area surveyed per site Total area surveyed per island group

18

12

26

17

34

14

4,320 m2

2,880 m2

6,240 m2

4,080 m2

8,160 m2

3,360 m2

85,536 m2

75,720 m2

92,712 m2

59,232 m2

92,640 m2

30,144 m2

161,256 m2

151,944 m2

122,784 m2

* SCDS: mean transect size used for density calculations = 81 m long x 4 m wide ** Reef front search: mean transect size used for density calculations = 137 m long x 4m wide


15

Taunga SMA

Zoomed area for density map

Ovaka SMA

Taunga SMA

Figure 10. Location of survey stations for all survey methods in Vava’u, 2016. Blue polygons represent special management areas (SMAs); green polygons inside the SMAs represent fish habitat reserves (FHRs).

16



Ovaka SMA

Kotu SMA

Ha’afeva SMA

Felemea SMA

O’ua SMA

Kotu SMA

Ha’afeva SMA

Felemea SMA

O’ua SMA

Figure 11. Location of survey stations for all survey methods in Ha’apai north, 2016. Blue polygons represent special management areas (SMAs); green polygons inside the SMAs represent fish habitat reserves (FHRs).


17

Nomuka SMA

Kelefesia SMA

Figure 12. Location of survey stations for all survey methods in Ha’apai south, 2016. Blue polygons represent special management areas (SMAs); green polygons inside the SMAs represent fish habitat reserves (FHRs).

18


Fafa SMA Kolonga SMA

‘Eueiki SMA

Fafa SMA Kolonga SMA

‘Eueiki SMA


‘Atata SMA


‘Atata SMA

Figure 13. Location of survey stations for all survey methods in Tongatapu, 2016. Blue polygons represent special management areas (SMAs); green polygons inside the SMAs represent fish habitat reserves (FHRs).


19

Species presence Twenty-three species were recorded during the 2016 survey in Tonga (Table 5). In addition, two sea cucumbers observed within the Ha’apai SMAs were not identified to species level. One individual was identified as Bohadschia sp. due to its unusual colour pattern. It is likely that this species was either Bohadschia argus or Bohadschia similis. Another sea cucumber species was only identified to genus level (Synapta sp.), although based on the description provided by the recorder, it is likely to be Synapta maculata. The total number of species observed differed by island group and by management regime (i.e. whether the station was in an open area or in an SMA; see Table 5). In Vava’u, 19 species of sea cucumbers were recorded, with 18 species observed in open areas and 12 within SMAs. In Ha’apai, 19 species were recorded, with slightly more species observed in SMAs (n=18) than in open areas (n=13). In Tongatapu, 21 species were recorded, with few differences among SMAs, where 17 species were encountered, and open areas, where 19 species were encountered (Table 5). Differences in species present among island groups and management regimes likely results from several factors, including the type of habitats represented (and surveyed), the small size of SMAs and the habitats they encompass, and the level of fishing effort at each site. Table 5. Sea cucumbers observed in each site during the 2016 assessment. Common name

Scientific name

Deepwater redfish


Stonefish

Actinopyga lecanora

Surf redfish

Open

Ha’apai

SMA

Open

Tongatapu

SMA

+

Open

SMA

+ +

+


+

+

Hairy blackfish

Actinopyga miliaris

+

+

Deepwater blackfish

Actinopyga palauensis

Tigerfish

Bohadschia argus

Chalkfish

Bohadschia similis

Brown sandfish


+

+

+

+

+

+

Lollyfish

Holothuria atra

+

+

+

+

+

+

Snakefish

Holothuria coluber

+

+

+

+

+

+

Pinkfish

Holothuria edulis

+

+

+

+

+

+

White teatfish


+

+

+

+

+

+

Elephant trunkfish


+

+

+

+

+

+

Tiger-tail sea cucumber

Holothuria hilla

+

+

+

Golden sandfish

Holothuria lessoni

+

+

+

+

Black teatfish

Holothuria whitmaei

+

+

+

+

Flowerfish

Pearsonothuria graeffei

Greenfish


+

+

+

+

+

Curryfish

Stichopus herrmanni

+

+

+

+

+

Dragonfish

Stichopus horrens

+

+

+

Spotted-worm sea cucumber Synapta maculata

+

Prickly redfish

Thelenota ananas

+

+

+

Amberfish

Thelenota anax

+

+

+

18

12

13

Total number of verified species

20

Vava’u


+

+ +

+

+

+

+ +

+

+

+ + + +

+

+

+

+

+

+

+

+

18

19

17

Species of conservation significance Of the 23 sea cucumber species observed during the 2016 assessment, several are listed under the International Union for Conservation of Nature (IUCN) ‘Red List’: -

Black teatfish (Holothuria lessoni), white teatfish (Holothuria whitmaei) and prickly redfish (Thelenota ananas) are classified as ‘endangered’;

-

Deepwater redfish (Actinopyga echinites), surf redfish (Actinopyga mauritiana), hairy blackfish (Actinopyga miliaris), white teatfish (Holothuria fuscogilva) and curryfish (Stichopus herrmanni) are classified as ‘vulnerable’;

-

Deepwater blackfish (Actinopyga palauensis), tigerfish (Bohadschia argus), lollyfish (Holothuria atra), snakefish (Holothuria coluber), pinkfish (Holothuria edulis), elephant trunkfish (Holothuria fuscopunctata), tiger-tail sea cucumber (Holothuria hilla), flowerfish (Pearsonothuria graeffei) and greenfish (Stichopus chloronotus) are classified as ‘least concern’;

-

Stonefish (Actinopyga lecanora), chalkfish (Bohadschia similis), brown sandfish (Bohadschia vitiensis), dragonfish (Stichopus horrens) and amberfish (Thelenota anax) are classified as ‘data deficient’; and

-

Spotted-worm sea cucumber (Synapta maculata) has not yet been evaluated.

Comparison of species presence with previous surveys Several differences were observed with respect to species presence among the 2016 assessment and previous surveys of Pakoa et al. (2013a) and Pakoa et al. (unpublished) (Fig. 14). The main differences among the surveys were: -

Overall, slightly more species were observed during the 2016 assessment (n=23) than during surveys of Pakoa et al. (2013a) and Pakoa et al. (unpublished) (n=19), and at each island group (Fig. 14), likely resulting from greater survey effort and more complete habitat coverage in the 2016 assessment;

-

Deepwater blackfish (Actinopyga palauensis) was recoded in Ha’apai and Tongatapu in 2016 but was not reported in previous surveys;

-

Flowerfish (Pearsonothuria graeffei) was recorded in Ha’apai in 2016 but was not reported in previous surveys.

-

Tiger-tail sea cucumber (Holothuria hilla) and spotted worm sea cucumber (Synapta maculata) were both recorded in Vava’u and Tongatapu in 2016 but were not reported in previous surveys.

Number of species recorded

25

2016 assessment

Previous surveys

20

15

10

5

0

Vava'u

Ha'apai

Tongatapu

Island group Figure 14. Comparison of the numbers of sea cucumber species recorded during the 2016 assessment and previous surveys of Pakoa et al. (2013a, for Vava’u and Tongatapu) and Pakoa et al. (unpublished, for Ha’apai).

Species abundance In total, 30,252 individual sea cucumbers were counted during the 2016 assessment. Overall, lollyfish was by far the most commonly encountered species, constituting 77% of all individuals observed (Table 6). High-value and very high-value species were rare. For example, only 17 prickly redfish (representing 0.06% of all sea cucumbers recorded) and 16 white teatfish (0.05% of all sea cucumbers recorded) were observed in the 436 km2 surveyed (Table 6).


21

Table 6.Total counts of sea cucumbers, by species, from each island group and site during the 2016 assessment (excluding those species not identified to species level). Total counts, and the relative composition of each species to the total number of individuals observed, are provided in the right-hand columns. Common name

Vava’u

Ha’apai

Tongatapu

Total

Open

SMA

Open

SMA

Open

SMA

n

%

Lollyfish

7,399

2,890

1,105

5,473

6,336

234

23,437

77.48

Pinkfish

1,440

98

7

74

897

136

2,652

8.77

Greenfish

616

345

471

268

246

292

2,238

7.40

Brown sandfish

223

257

6

52

85

3

626

2.07

Snakefish

304

13

4

36

71

19

447

1.48

Tigerfish

90

26

31

21

43

8

219

0.72

Curryfish

64

7

0

3

59

40

173

0.57

Amberfish

49

15

42

3

21

11

141

0.47

Elephant trunkfish

29

6

14

9

32

12

102

0.34

Tiger-tail sea cucumber

21

0

0

0

12

14

47

0.16

Golden sandfish

9

0

0

4

30

1

44

0.15

Dragonfish

25

0

1

2

4

0

32

0.11

Surf redfish

14

0

0

1

0

5

20

0.07

Prickly redfish

3

2

6

2

2

2

17

0.06

White teatfish

1

1

3

3

4

4

16

0.05

Black teatfish

7

0

1

4

3

1

16

0.05

Deepwater redfish

0

3

0

0

2

0

5

0.02

Deepwater blackfish

0

0

0

1

0

4

5

0.02

Spotted-worm sea cucumber

2

0

0

0

2

1

5

0.02

Stonefish

0

0

0

1

2

0

3

0.01

Hairy blackfish

2

0

0

1

0

0

3

0.01

Chalkfish

0

0

0

0

1

0

1

5 individuals measured are displayed. Sample sizes of measured individuals are provided below species names. See Appendix 5 for mean lengths of all observed species, by site. The status of sea cucumbers in the Kingdom of Tonga in 2016

35

Lollyfish (Holothuria atra) Length frequency analysis revealed that the population of lollyfish in Vava’u generally consisted of small individuals, with few individuals greater than 300 mm in length (Fig. 25). The modal (most common) length class of lollyfish in Vava’u was 141–150 mm, while the mean length was 147.7 ± 1.9 mm, below minimum legal capture length for Tonga (165 mm live length), and below the mean length observed by Pakoa et al. (2013a) for lollyfish in Vava’u of 166 ± 2.4 mm. Of the 458 individual lollyfish measured in Vava’u, 28% were above the minimum legal length for harvest (165 mm). Few differences were evident in length frequencies of lollyfish between stations within open areas and SMAs of Vava’u (Fig. 26). In contrast to Vava’u, relatively higher numbers of large lollyfish were observed in Ha’apai (Fig. 25). The modal length class of lollyfish in Ha’apai was 151–160 mm, while the mean length was 188.7 ± 4.1 mm. Approximately 48% of the measured lollyfish in Ha’apai were above the minimum legal length for harvest (Fig. 25). Few differences were evident in length frequencies of lollyfish between stations within open areas and SMAs of Ha’apai (Fig. 26). The Tongatapu lollyfish population exhibited the largest length range of the three island groups surveyed, with a long righthand tail indicating the presence of breeding-sized adults (Fig. 25). The modal length class of lollyfish in Tongatapu was small, at 111–120 mm, while the mean length was 173.1 ± 2.2 mm, slightly above the minimum legal length for harvest, but well below the mean length observed by Pakoa et al. (2013a) for lollyfish in Tongatapu (196 ± 8.0 mm). Approximately 53% of the measured lollyfish in Tongatapu were above the minimum legal length for harvest (Fig. 25). Length frequencies of lollyfish appeared slightly different between open areas and SMAs, with SMAs supporting a greater proportion of larger lollyfish than open areas (Fig. 26). 100

a) Vava'u (n=770)

Frequency (n)

80 60 40 20

1-10 21-30 41-50 61-70 81-90 101-110 121-130 141-150 161-170 181-190 201-210 221-230 241-250 261-270 281-290 301-310 321-330 341-350 361-370 381-390 401-410 421-430 441-450 461-470 481-490 501-510 521-530 541-550 561-570 581-590

0

Length class (mm) 100

b) Ha'apai (n=373)

Frequency (n)

80 60 40 20

1-10 21-30 41-50 61-70 81-90 101-110 121-130 141-150 161-170 181-190 201-210 221-230 241-250 261-270 281-290 301-310 321-330 341-350 361-370 381-390 401-410 421-430 441-450 461-470 481-490 501-510 521-530 541-550 561-570 581-590

0

Length class (mm)

100

c) Tongatapu (n=915)

Frequency (n)

80 60 40 20

1-10 21-30 41-50 61-70 81-90 101-110 121-130 141-150 161-170 181-190 201-210 221-230 241-250 261-270 281-290 301-310 321-330 341-350 361-370 381-390 401-410 421-430 441-450 461-470 481-490 501-510 521-530 541-550 561-570 581-590

0

Length class (mm)

36


Figure 25. Length frequencies of lollyfish (Holothuria atra) recorded at a) Vava’u, b) Ha’apai and c) Tongatapu during the 2016 assessment. Red dashed line indicates the minimum legal live length for harvest of lollyfish in Tonga (165 mm).

14

12

0

12

0 1-10 21-30 41-50 61-70 81-90 101-110 121-130 141-150 161-170 181-190 201-210 221-230 241-250 261-270 281-290 301-310 321-330 341-350 361-370 381-390 401-410 421-430 441-450 461-470 481-490 501-510 521-530 541-550 561-570 581-590

Frequency (%)

1-10 21-30 41-50 61-70 81-90 101-110 121-130 141-150 161-170 181-190 201-210 221-230 241-250 261-270 281-290 301-310 321-330 341-350 361-370 381-390 401-410 421-430 441-450 461-470 481-490 501-510 521-530 541-550 561-570 581-590

0

1-10 21-30 41-50 61-70 81-90 101-110 121-130 141-150 161-170 181-190 201-210 221-230 241-250 261-270 281-290 301-310 321-330 341-350 361-370 381-390 401-410 421-430 441-450 461-470 481-490 501-510 521-530 541-550 561-570 581-590

Frequency (%)

Frequency (%) 14

a) Vava’u

12

Vava'u Open

10

Vava'u SMAs

8

6

4

2

Length class (mm)

b) Ha'apai Ha'apai Open

10 Ha'apai SMAs

8

6

4

2

Length class (mm)

10 c) Tongatapu Tongatapu Open

Tongatapu SMAs

8

6

4

2

Length class (mm)

Figure 26. Comparison of length frequencies of lollyfish (Holothuria atra) recorded from open areas and SMAs at a) Vava’u, b) Ha’apai and c) Tongatapu during the 2016 assessment.


37

Pinkfish (Holothuria edulis) Length frequency analysis revealed that populations of pinkfish in both Vava’u and Ha’apai generally consisted of small- to medium-sized individuals in the range of 81–300 mm (Vava’u) and 101–230 mm (Ha’apai) (Fig. 27). The modal length class of pinkfish in Vava’u was 171–180 mm, while the mean length was 184.8 ± 3.0 mm, slightly larger than the mean length observed by Pakoa et al. (2013a) for pinkfish in Vava’u (163 ± 5.8 mm). In Ha’apai, the modal length class of pinkfish was 161–170 mm, while the mean length was 175.7 ± 5.6 mm. Of the three island groups, the largest numbers of pinkfish measured were in Tongatapu. Here, observed length classes ranged from 31–40 mm to 331–340 mm (Fig. 27). The modal length class was 111–120 mm, while the mean length was 170.6 ± 2.9 mm. This represents a large decrease in mean length to that observed by Pakoa et al. (2013a) for pinkfish in Tongatapu (198 ± 6.0 mm), and is likely the result of harvesting larger, more valuable specimens from the population for the export trade. There is currently no minimum legal length for harvest for pinkfish in Tonga. Greenfish (Stichopus chloronotus) Length frequencies of greenfish were generally similar across the three island groups, although the largest numbers of greenfish were measured in Vava’u (n=313). Here, the population ranged in length classes from 51–60 mm to 281–290 mm, with a modal length class of 171–180 mm (Fig. 28). The mean length of greenfish in Vava’u was 159.1 ± 2.5 mm, representing a slight increase from that observed in the previous survey of Pakoa et al. (2013a) (144 ± 3.0 mm). In Ha’apai, the greenfish population ranged from length classes of 41–50 mm to 271–280 mm. The majority of individuals were relatively small, however, with most individuals occurring in the 111–120 mm to 161–170 mm length classes (Fig. 28). The modal length class was 141–150 mm, and the mean length of greenfish in Ha’apai was 157.2 ± 3.5 mm. In total, 167 greenfish were measured in Tongatapu during the 2016 study. Observed length classes ranged from 31–40 mm to 261–270 mm, with a modal length class of 111–120 mm (Fig. 28). The mean length of greenfish in Tongatapu during the 2016 assessment was 161.3 ± 3.8 mm, which is slightly larger than that observed by Pakoa et al. (2013a) (155 ± 6 mm). Amberfish (Thelenota anax) In total, 80 amberfish were measured during the 2016 assessment (out of 141 individuals observed). While the number of amberfish observed was low, the length frequency revealed the population contained both new recruits and large breeding adults (Fig. 29). Observed length classes ranged from 151–200 mm to 810–850 mm, with a relatively large modal length class of 601–650 mm. Overall, 86% of the amberfish population across the island groups was above the minimum legal harvest length of 400 mm (Fig. 29). The mean length of amberfish (across all sites and island groups) was 567.4 ± 14.4 mm (Fig. 24), representing a slight increase from that observed by Pakoa et al. (2013a) of 524 ± 30.6 mm in Vava’u (n = 14) and 458 ± 32 mm in Tongatapu (n=23) . Tigerfish (Bohadschia argus) During the 2016 assessment, 72 tigerfish were measured, including 31 individuals from Vava’u, 18 from Ha’apai and 23 from Tongatapu. As with amberfish, while the total number of tigerfish observed was low, the length frequency revealed the population contained relatively both new recruits and large breeding adults (Fig. 29). Observed length classes ranged from 161–180 mm to 541–560 mm, with a modal length class of 341–360 mm (Fig. 29). The mean length of tigerfish (across all sites and island groups) was 338.3 ± 9.0 mm (Fig. 24), representing a slight increase from that observed by Pakoa et al. (2013a) of 274 ± 12 mm in Vava’u (n=47) and 303 ± 16 mm in Tongatapu (n=23) . Elephant trunkfish (Holothuria fuscopunctata) During the 2016 assessment, 60 elephant trunkfish (out of 102 individuals observed) were measured, including 16 from Vava’u, 15 from Ha’apai and 29 from Tongatapu. Observed length classes ranged from 101–150 mm to 651–700 mm, with a modal length class of 401–450 mm. The mean length of elephant trunkfish (all sites and islands combined) was 376.9 ± 13.3 mm. Approximately 55% of measured individuals were above the minimum legal harvest length in Tonga (350 mm). White teatfish (Holothuria fuscogilva) Of the 16 white teatfish recorded during the 2016 assessment, 12 were measured, including 1 individual from Vava’u, 3 individuals from Ha’apai, and 8 individuals from Tongatapu. The mean length of these 12 individuals was 260.0 ± 17.5 mm. This represents a large decrease from that observed by Pakoa et al. (2013a), who observed mean lengths of 317 ± 11 mm and 368 ± 31 mm in Vava’u (n=14) and Tongatapu (n=13), respectively. Again, this decrease in mean length is likely the result of recent heavy fishing pressure and the harvest of larger, more valuable specimens for the export trade. Of the 12 white teatfish measured, only 2 (17% of measured individuals) were above the minimum legal harvest length in effect in Tonga (320 mm).

38


0

381-390

361-370

341-350

321-330

301-310

281-290

261-270

241-250

221-230

201-210

181-190

161-170

141-150

121-130

101-110

35

81-90

40

61-70

0

10

5 301-310

281-290

261-270

241-250

221-230

201-210

181-190

161-170

141-150

121-130

101-110

81-90

61-70

41-50

381-390

381-390

15

361-370

20 361-370

25

341-350

30 341-350

b) Ha'apai (n=43)

321-330

b) Ha’apai (n=43) 321-330

Length class (mm)

301-310

281-290

261-270

241-250

221-230

201-210

181-190

161-170

141-150

121-130

101-110

81-90

61-70

41-50

35

41-50

40 21-30

1-10

0

21-30

1-10

Frequency (n) Frequency (n) 35

21-30

1-10

Frequency (n) 40

a) Vava’u (n=313)

30

25

20

15

10

5

Length class (mm)

c) (n=432) c)Tongatapu Tongatapu (n=342)

30

25

20

15

10

5

Length class (mm)

Figure 27. Length frequencies of pinkfish (Holothuria edulis) recorded at a) Vava’u, b) Ha’apai and c) Tongatapu during the 2016 assessment.


39

40

10 55 050

0

121-130 121-130 121-130

Length Length class class (mm) (mm)


Length class class (mm) (mm) 281-290 281-290 281-290 301-310 301-310 301-310 321-330 321-330 321-330 341-350 341-350 341-350 361-370 361-370 361-370 381-390 381-390 381-390

281-290 281-290 281-290

301-310 301-310 301-310

321-330 321-330 321-330

341-350 341-350 341-350

361-370 361-370 361-370

381-390 381-390 381-390

15 20 15 10 15 10 261-270 261-270 261-270

25 30 25 20 25 20

261-270 261-270 261-270

c) Tongatapu (n=167) c) Tongatapu (n=167) 241-250 241-250 241-250

c)c)Tongatapu (n=167) Tongatapu (n=167)

241-250 241-250 241-250

Length class (mm) 221-230 221-230 221-230

201-210 201-210 201-210

181-190 181-190 181-190

161-170 161-170 161-170

141-150 141-150 141-150

121-130 121-130 121-130

101-110 101-110 101-110

81-90 81-90 81-90

61-70 61-70 61-70

381-390 381-390 381-390

361-370 361-370 361-370

341-350 341-350 341-350

321-330 321-330 321-330

301-310 301-310 301-310

281-290 281-290 281-290

261-270 261-270 261-270

241-250 241-250 241-250

221-230 221-230 221-230

201-210 201-210 201-210

181-190 181-190 181-190

161-170 161-170 161-170

141-150 141-150 141-150

121-130 121-130 121-130

101-110 101-110 101-110

81-9081-90 81-90

61-7061-70 61-70

41-50 41-5041-50

21-30 21-3021-30

Length class class (mm) (mm)

221-230 221-230 221-230

201-210 201-210 201-210

181-190 181-190 181-190

161-170 161-170 161-170

141-150 141-150 141-150

35 40 35 30 35 30

101-110 101-110 101-110

40 40

81-90 81-90 81-90

0

61-70 61-70 61-70

050

41-50 41-50 41-50

30 30 35

41-50 41-50 41-50

35 35 40

21-30 21-30 21-30

40 40

21-30 21-30 21-30

0

1-10 1-10 1-10

050

1-101-10 1-10

Frequency Frequency (n) (n)

Frequency (n) Frequency (n) (n) Frequency 30 30 35 25 25 30

1-101-10 1-10

Frequency Frequency (n) (n) Frequency (n)

40 40 35 35 40

a) a) Vava'u Vava'u (n=313) (n=313)

a) Vava’u (n=313)

a) Vava'u (n=313)

20 20 25 15 15 20

10 10 15 55 10

Length class (mm)

b) Ha’apai (n=138)

b) Ha'apai (n=138)

b) Ha'apai (n=138)

25 25 30

20 20 25

15 15 20

10 10 15

55 10

Length class (mm) Figure 28. Length frequencies of greenfish (Stichopus chloronotus) recorded at a) Vava’u, b) Ha’apai and c) Tongatapu during the 2016 assessment. The red dashed line indicates the current minimum legal live length for harvesting greenfish in Tonga (130 mm).

a) Amberfish (n=80)

801-850

751-800

701-750

651-700

601-650

551-600

501-550

451-500

401-450

351-400

301-350

201-250

151-200

101-150

51-100

a) Amberfish (n=80)

1-50

Frequency (n)

20 18 16 14 12 10 8 6 4 2 0

20 18 16 14 12 10 8 6 4 2 0

b) Tigerfish (n=72)

541-560

521-540

501-520

481-500

461-480

441-460

421-440

401-420

381-400

361-380

341-360

321-340

301-320

281-300

261-280

241-260

221-240

201-220

181-200

161-180

141-160

121-140

101-120

81-100

61-80

41-60

1-20

b) Tigerfish (n=72)

21-40

Frequency (n)

Length class (mm)

651-700

601-650

551-600

501-550

451-500

401-450

351-400

301-350

251-300

201-250

151-200

101-150

c) c) Elephant Elephant trunkfish trunkfish(n=60) (n=60)

51-100

20 18 16 14 12 10 8 6 4 2 0

1-50

Frequency (n)

Length class (mm)

Length class (mm) Figure 29. Length frequencies of a) amberfish (Thelenota anax), b) tigerfish (Bohadschia argus) and c) elephant trunkfish (Holothuria fuscopunctata) recorded during the 2016 assessment (all sites and island groups combined). The red dashed line indicates the current minimum legal live length for harvesting a) amberfish (400 mm), b) tigerfish (270 mm) and c) elephant trunkfish (350 mm) in Tonga.


41

Discussion Results of the 2016 survey indicate that sea cucumber stocks in Tonga are in a poor state. In-water assessments revealed that individual species’ densities were low across all sites and island groups, and for some species, were critically low. For some species, including the high-value black teatfish and prickly redfish, very high-value white teatfish, and low-value elephant trunkfish, observed mean densities were well below those reported in 1996, at least at Ha’apai (Lokani et al. 1996), when the stock was considered on the verge of total collapse. These observed densities are worrying, particularly given that successful reproduction among sea cucumbers depends on having males and females in sufficient densities to allow them to spawn in close proximity so that eggs and sperm come into contact. Purcell et al. (2009) suggested that populations fail to repopulate effectively at densities below 30 ind/ha. Given that the majority of species in each of the island groups were found at densities lower than 30 ind/ha (see Results, Appendix 3, Appendix 4), populations in Tonga may be slow to re-build, even in the absence of fishing pressure. In addition to declines in densities over time, declines in length and average size were evident in the 2016 assessment and the surveys of Pakoa et al. (2013a) for a number of species. In a study on trade, value and market preference of Pacific Island beche-de-mer in the Hong Kong market, Purcell (2014) reported that prices reached for individual species were positively correlated with body size, with larger bodied individual reaching far greater prices than smaller bodied individuals of the same species. Size-selective fishing, such as that achieved when fishers are collecting sea cucumbers by hand to maximise economic returns, often results in overall declines in length (and age) structures and declines in mean length of harvested organisms, with subsequent alterations in maturity profiles and overall reproductive potential (Ricker 1981; Chuwen et al. 2011; Moore et al. 2017). Accordingly, the observed declines in length and average size are likely to be the result of heavy harvest pressure in recent years. While the small sizes of SMAs prevented an assessment of their performance on an individual basis, few differences were observed in the 2016 survey in terms of densities of individual sea cucumber species and overall cumulative densities at stations in areas open to fishing and within SMAs (including the no-take fish habitat reserves). For the Ovaka SMA in Vava’u and Felemea SMA in Ha’apai, these results are contrary to community perceptions, with community members asserting that densities have improved since the creation of these SMAs in 2008 (Gillett 2017). The reasons for such a discrepancy in perception vs quantitative data are unclear, but on a positive note, reflect the positive mindset of the communities in the role that SMAs play in reducing fishing pressure and conserving stocks.

Recommendations for management and monitoring The poor state of sea cucumber populations and large quota over-runs indicate that the management strategies in the Tonga National Sea Cucumber Fishery Management and Development Plan, or at least their implementation, have been largely ineffective at maintaining harvest pressure at a sustainable level. In light of the October 2015 Cabinet decision to assign exclusive legal ownership of sea cucumber resources to coastal communities that own SMAs, and exclusive legal right to develop and manage sea cucumber resources to those communities, new management strategies will need to be developed. It is noted that the recommendation approved by Cabinet does not necessarily specify that SMA communities will have exclusive legal ownership or have exclusive legal right to develop, manage, farm, harvest, process or market sea cucumber resources within their own SMA per se, but leaves it open for interpretation that they will have these rights for sea cucumber resources that inhabit the country’s coastal waters. This decision is a bold move that will require considerable stakeholder input for its successful implementation, and one that raises many questions. For example, how will the Ministry of Fisheries and/or SMA communities determine whether sea cucumber stocks can sustain a harvest, and how will harvests will be determined, managed and monitored? If harvests are managed using a quota system, how will this be divided among SMA communities to ensure that benefits of the fishery are shared equitably? How will non-SMA communities be affected? Will there be strategies to ensure their inclusion in the fishery, or mitigate their losses if they are to be excluded? Should SMA communities be able to fish and sell sea cucumbers to non-SMA communities? While a thorough examination of the management issues resulting from the October 2015 Cabinet decision is beyond the scope of this report, below we provide a discussion on the key points for management, using lessons learned from the implementation of the Tonga National Sea Cucumber Fishery Management and Development Plan, and a preliminary assessment of the pros and cons of this decision. 1. Harvest strategies and prescribed species. At the time of writing, it was unclear how potential harvests by SMA communities will be determined and managed. Exports (and, presumably, harvests) of sea cucumbers in Tonga were historically ‘capped’ using a quota system. Section 3.1 of the Tonga National Sea Cucumber Fishery Management and Development Plan describes quotas for the harvesting of sea cucumber resources. The Plan states that ‘separate quotas are assigned for each species and for each island groups’. Prescribed quotas are provided in Table 2 of the Plan, and equate to 157.5 t dry weight (74.6 t from Tongatapu, 49.7 t from Ha’apai and 33.2 t from Vava’u). According to senior Ministry of Fisheries staff, these prescribed quotas were for 2008 only (Poasi Ngaluafe, Principal Fisheries Officer, Ministry of Fisheries, pers. comm.). These quotas were slightly changed in 2009–2014 but not based on any stock size estimate. For 2009–2014, there were no species- or island-specific quotas, which is in direct disagreement with the terms of the Plan (Poasi Ngaluafe, Principal Fisheries Officer, Ministry of Fisheries, pers. comm.)

42


While quotas have been used to manage sea cucumber and other invertebrate fisheries in numerous Pacific Island countries and territories, there are few long-term successful examples of the use of quota systems in the management of marine resources in the region, largely because the high costs (especially staff time) involved with monitoring harvests successfully are often beyond the capacity of the resource-poor fisheries agencies in the region. In recent years, Vanuatu has had large quota over-runs in its sea cucumber fisheries, which is jeopardising the sustainability of the fishery (Christopher Arthur, Vanuatu Fisheries Department, pers. comm.). In Papua New Guinea, the catch quota for the fishery was exceeded in several years because the reporting was insufficient and there were so many individual fishers that it was impossible to communicate to fishers when the quotas were reached (Kinch et al. 2008). In an assessment of the sea cucumber fishery in New Caledonia, Purcell et al. (2009) strongly advised against the use of quotas, even for the country’s relatively resource-rich fishery. Accordingly, it is recommended that when designing the new management strategy, the Ministry of Fisheries and stakeholders review the existing harvest strategy, and in particular explore alternate harvest strategies to the current quota system. To start this discussion, an exploration of different quota or no-quota based systems, and key questions to address for each system wen developing a management plan, is provided in Table 13. If a quota system is maintained under the new management strategy, quotas for future harvests should be calculated based on scientific evidence. In-water surveys should be conducted to determine individual species’ densities within areas of interest, and estimated stock sizes calculated from these density estimates and the area of suitable habitat. Only species observed in densities greater than the regional reference densities of Pakoa et al. (2014) should be made available for harvest. Quotas should be determined based on a small proportion of the stock over the length at maturity and minimum legal size, using the example provided in Pakoa et al. (2014; see Appendix 6). This process is deemed to be a conservative method for determining species quotas in that: a.

Only species with densities over regional reference densities should be considered for harvest;

b.

The lower 95% confidence interval of the individual species’ density estimates should be for stock extrapolations;

c.

Stock size estimates should be based on areas of suitable habitat (excluding protected areas such as no-take fish habitat reserves). It may be that there are individuals of a species in areas outside of these suitable habitats. These individuals are not factored into stock size estimations, meaning estimates likely represent an underestimation of total stock size;

d.

Habitat areas are reduced by 20% (i.e. to 80% of total habitat area) to provide a more conservative stock size estimate);

e.

Only individuals over a prescribed length (e.g. length at first maturity or minimum legal harvest lengths) should be available for harvest, thereby giving most individuals the opportunity to reproduce at least once in their life history); and

f.

Only a small proportion of adults (e.g. maximum 30%) should be considered for harvest, ensuring that a large proportion of the breeding stock remains unharvested.

2)

Size limits. Minimum size limits for the harvest of certain sea cucumber species in Tonga are prescribed in either Schedule 8 of the Fisheries (Conservation and Management) Regulations 1994 or the Tonga National Sea Cucumber Fishery Management and Development Plan (Table 14). Where imposed, many of these size limits are well below ‘common’ lengths observed in the region and are too small to offer protection to juvenile and sub-adult components of the stock and to allow individuals the opportunity to reproduce at least once before harvest. Moreover, for the majority of species harvested for the beche-de-mer trade, there are no size limits, meaning that all components of the stock of these species, including juveniles, are available for harvest. New minimum sizes for all species harvested for the beche-de-mer trade are proposed in Table 14. Given that export values of sea cucumbers are often positively correlated with body size (Purcell 2014), introducing minimum harvest sizes would also help to maximise economic benefits of the fishery.

3)

Number of fishing licences. Section 3.3 of the Tonga National Sea Cucumber Fishery Management and Development Plan states that ‘The only persons who may allow to fish for sea cucumbers for commercial gain or sale are those who have registered to fish for sea cucumbers with the Fisheries Division’ (now Ministry of Fisheries). At the time of writing this report, it was unknown how many fishers are currently registered to fish commercially for sea cucumbers (or how many typically do when the fishery is open), although it is understood that this there is no cap on the number of fishers that can register. However, discussions with fishers at landing sites during the Ministry of Fisheries creel survey programme suggests that most fishers feel there are too many fishers in the fishery (Ministry of Fisheries, unpublished data). Reducing the numbers of fishers who can fish for sea cucumbers may assist in reducing fishing effort, and may make monitoring of harvests more manageable. While considerable thought is needed to ensure that there is equitable distribution of benefits in the adoption of a limited entry fishery (i.e. how and to whom should the limited number of licences be awarded?), it is recommended that each fisher participating in the fishery should be required to


43

have a licence, and not just boat captains or boat owners. In this way, each fisher can be contacted about fishery rules and regulations, while those fishers without a boat are not prevented from entering the fishery. It also helps to limit the number of fishers; in a scenario where only boat captains or owners are licenced, boats may be loaded with numerous fishers, diminishing the control on effort (Purcell et al. 2009). 4)

Number of export licences. Section 3.3 of the Tonga National Sea Cucumber Fishery Management and Development Plan states that ‘there shall be a maximum of three Bech-de-mer (sic) licences for each of the island group (Tongatapu, Ha’apai and Vava’u)’. However, according to data held by the Ministry of Fisheries, this provision was rarely adhered to for the period 2008–2014, with as many as 24 export licences issued in 2009. With the cancellation of the existing system of registration of sea cucumber fishers for export under the October 2015 Cabinet decision) a new system of registration and licencing of exporters will need to be developed. At the time of writing, it was unclear what form a new licencing system would take; i.e. whether exporting operations would be operated by the Government, by private enterprise, or in a cooperation of SMA communities, government and private enterprise. If private enterprise, under this new system, and in order to monitor harvests effectively, it is recommended that the number of export licences for each island group be strictly limited to a maximum of two per island group.

5)

Harvest seasons. Under the Tonga National Sea Cucumber Fishery Management and Development Plan, a closed season is imposed from 1 October through to 31 March every year (Section 3.1. of the Plan), encompassing the spawning season of the majority of species found in Tonga’s waters. While the adoption of a closed season is highly commended, monitoring harvests of individual fishers or fishing communities over a six-month open season is extremely difficult and likely beyond the resource capacity of the Ministry of Fisheries. We recommend that should the fishery re-open, a shorter harvest season (e.g. three months maximum) be imposed.

6)

Stakeholder consultation and awareness. Stakeholder engagement, education and awareness raising is critical for successful management of sea cucumber fisheries. Stakeholder engagement and consultation should be undertaken at all steps of the development of any new management plan. This should include all stakeholders in the fishery, including fishers, processors, exporters, and local and national fisheries staff. In addition, an education and awareness plan should be developed by the Ministry of Fisheries (in collaboration with regional agencies, such as SPC, to ensure that fishers are aware of the fishery regulations and the October 2015 Cabinet Decision regarding sea cucumber ownership, and so that fishers receive some face-to-face education about sea cucumbers, the fishery, and the status of stocks. This later component should involve discussions between fisheries managers and fishers about the growth, reproductive biology and ecology of the species in non-scientific terms. The education programme should ensure that fishers understand the current status of stocks, how old the animals are that they are fishing, the sizes at which animals become mature, and how stocks replenish themselves after being fished. It is hoped that through this understanding, fishers will gain an appreciation for the need for size limits and other fisheries regulations and be prepared to respect them. All stakeholders should be educated to understand why fishery regulations are in place and how each regulation acts to improve the benefits for all stakeholders.

Due to the observed low stock densities, and low population replenishment rates of many sea cucumber species, it is unlikely that stocks of all species will rebuild during the five-year moratorium, let alone within the third year of the moratorium as specified by the Cabinet decision in which the Ministry of Fisheries is required to undertake another assessment. Survey work by SPC and the Ministry of Fisheries in Ha’apai in 2004 revealed that stocks of black teatfish were still at depleted levels seven years after a moratorium was imposed in 1997 (Friedman et al. 2011). Given that densities of this species in 1997 were higher than those observed in the 2016 survey, and failed to recover in seven years, it is unlikely that stocks of black teatfish, and other low-recovery species (e.g. golden sandfish, prickly redfish, white teatfish) will recover in the current five-year closure. Ongoing monitoring will be required to assess the effectiveness of the current moratorium and determine whether stocks have recovered sufficiently at the completion of the moratorium to sustain further harvests. A comprehensive survey should be conducted towards the end of the current five-year closure (i.e. before October 2019) at each island group. Survey stations and methods should match those of the 2016 assessment to allow for a comparison over time without spatial or methodological bias. In the event that observed densities are lower than the regional reference densities, we recommend that the moratorium be extended for an additional five years to provide further time for stocks to rebuild. In addition to in-water monitoring, efforts should be made by the Ministry of Fisheries to monitor illegal harvests and exports of sea cucumber resources in Tonga. This should include ‘spot’ checks at landing sites and known sea cucumber processing and export facilities, and export gateways. Heavy penalties should be imposed on anyone found contravening the moratorium. The total ban on harvests and exports of sea cucumber from Tonga in October 2015 was a significant first step by the Ministry of Fisheries to prevent further collapse of the fishery and to rebuild stocks to ensure sea cucumber resources are available for future generations of Tongans. The challenge is to ensure that appropriate management measures are put in place so that the mistakes of the past are not repeated. Table 13. Summary of the potential broad-scale harvest strategies for sea cucumbers in Tonga, and key questions to address for

44



45

Description

Total export /harvest quota and individual species export /harvest quota established for each export permit holder. Onus placed on exporter to ensure quota is adhered to.

Approach

Export quota / total harvest quota

management.

• High costs (staff time) associated with export monitoring and enforcement of exports.

• As value increases with size, quotas can be an incentive to avoid the harvest, purchase or export of smaller, less valuable individuals.

• Requires additional data input and information management capability.

• Amount harvested may exceed amount exported (stockpiling may occur).

• Difficulties associated with equal or equitable division of total harvest quota among individual fishers or communities (may result in unequal distribution of benefits among community members).

• May result in harvested sea cucumbers being discarded (if in excess to export quota or due to high-grading (where smaller harvested individuals are subsequent discarded in favour of larger individuals).

• May create ‘race-to-fish’ among individual fishers or communities.

• How will export quotas be calculated (i.e. will they be based on survey results or historical export records)?

• High costs associated with surveys to determine harvestable quotas.

• Creates theoretical maximum export / harvest amount.

• Will there be a trigger level for a notification to individual fishers, communities and/or exporters, beyond which additional management measures and monitoring is required? What form will these take?

• What happens when an individual species export quota is reached/exceeded (e.g. should quota over-runs be deducted from the following harvest?)?

• How will quotas be monitored?

• Will the licence and quota be linked (i.e. a licence comes with x quota for y species), or will they be separate (i.e. an exporter has to buy a licence and separately purchases quota)?

• How will export quotas be divided among individual fishers and communities to ensure equitable benefit (and avoid ‘race-to-fish’)?

• How often should quotas be allocated (e.g. every year, every second year etc.), and for what period?

• At what spatial level (e.g. national or island group) will export quotas be established?

Key questions for management

Disadvantages

Advantages

46

The status of sea cucumbers in the Kingdom of Tonga in 2016 • Requires additional data input and information management capability.

• May result in harvested sea cucumbers being discarded (if in excess to harvest quota or due to high-grading (where smaller harvested individuals are subsequent discarded in favour of larger individuals).

• Difficulties associated with equal or equitable division of total harvest quota among individual communities or fishers.

• Up-to-date monitoring required to ensure communities and/or fishers know where their harvested amounts are in relation to their quota.

• High costs (staff time) associated with harvest monitoring and enforcement of harvests and exports.

• Harvest quotas for individual fishers may prevent ‘race to fish’ as each fisher has their own specified portion of the total quota. • May promote equal distribution of benefits among community members.

• How will individual harvest quotas be calculated (i.e. will they be based on survey results or historical export records)?

• High costs associated with surveys to determine harvestable quotas.

• Creates theoretical maximum harvest amount.

Individual fisher or community harvest quota established. Individual species harvest quotas per fisher or community should also be established. Onus placed on both fisher and exporter to ensure quotas are adhered to. Monitoring of exports will be required to ensure exported number or weight matches harvested number or weight to prevent acceptance of illegal (over-quota) harvests.

Individual fisher or community harvest quota

• Will there be a trigger level for a notification to individual fishers, communities or exporters beyond which additional management measures and monitoring is required? What form will these take?

• Can individual fisher or community quotas be traded, transferred or leased?

• What happens when an individual species export quota is reached (e.g. should quota over-runs be deducted from the following harvest?)?

• Will there be monitoring of exports in addition to harvests (to prevent illegal harvest)?

• How will individual harvest quotas be monitored (e.g. will there be fisher catch logs or designated catch inspection sites and times)?

• Will the licence and quota be linked (i.e. a licence comes with x quota for y species), or will they be separate (i.e. a fisher or community has to buy a licence and separately purchases quota)?

• How often should quotas be allocated (e.g. every year, every second year, and so on), and for what period should they be viable?

• How will harvest quotas be divided among individual fishers or communities?


Disadvantages

Advantages

Description

Approach


47

• Still requires heavy investment in monitoring, control and surveillance of input and output controls.

• May exclude some communities (e.g. non-SMA or landlocked communities). • May result in unequal distribution of benefits among community members.

• Reduced risk of harvested sea cucumbers being wasted through ‘high-grading’ practices.

• Self-regulation may reduce costs on regulation, monitoring and control. • Reduced costs associated with in-water surveys, stock size estimation and quota allocation.

Individual resource users or specific user groups (e.g. SMA communities), are allocated exclusive right to fish in a geographically limited area (i.e. within tier SMAs). Catches and fishing effort are decided upon by the individual fisher or user group (in conjunction with other input and/or output controls such as gear restrictions, harvest seasons and size limits).

Allocated fishing rights (territorial use rights)

• Reduced risk of harvested sea cucumbers being wasted through ‘high-grading’ practices.

• May result in unequal distribution of benefits among community members.

• Reduced costs associated with in-water surveys, stock size estimation and quota allocation.

Management of fishery and limits on harvest are controlled via alternate input controls (e.g. limiting the number of fishing licences, limiting gear used to harvest sea cucumber to free-diving, or limiting the harvest season) or output controls (size limits).

No-quota: use of input and output controls

Disadvantages

Advantages

Description

Approach

• How will catches be monitored (e.g. will there be fisher or community catch logs or designated inspection sites or times)?

• Can individual community and/or fisher allocated rights be traded, transferred or leased?

• How to geographically divide fishing areas to ensure an equitable division among communities or fishers (to the benefit of both SMA and non-SMA communities, and noting differing export values of species in different habitats)?

• How will catches be monitored (e.g. will there be fisher or community catch logs or designated inspection sites or times)?

• Can individual fisher licences (if imposed) be traded, transferred or leased?


Table 14. Current minimum size limits for sea cucumber species in Tonga, and proposed new size limits.

1 2

48

Current minimum Proposed new Proposed new size (wet) minimum sizes (wet) minimum sizes (dry)

Common name

Scientific name

Amberfish

Thelenota anax

400 mm1

400 mm

200 mm

Black teatfish

Holothuria whitmaei

260 mm2

350 mm

200 mm

Brown curryfish

Stichopus vastus

300 mm

150 mm

Brown sandfish


300 mm

150 mm

Chalkfish

Bohadschia marmorata

200 mm

100 mm

Curryfish

Stichopus herrmanni

260 mm1

350 mm

150 mm

Deepwater redfish


120 mm2

200 mm

100 mm

Deepwater spiky redfish

Actinopyga sp. affn. flammea

250 mm

100 mm

Dragonfish

Stichopus horrens

200 mm

Elephant trunkfish


Flowerfish


Golden sandfish

Holothuria lessoni

Greenfish

240 mm

1

400 mm

200 mm

300 mm

150 mm

160 mm

250 mm

100 mm


1

130 mm

200 mm

100 mm

Hairy blackfish

Actinopyga miliaris

190 mm1

200 mm

100 mm

Lollyfish

Holothuria atra

165 mm2

300 mm

Pinkfish

Holothuria edulis

Prickly redfish

Thelenota ananas

Snakefish

350 mm2

250 mm

150 mm

400 mm

150 mm

Holothuria coluber

400 mm

200 mm

Stonefish

Actinopyga lecanora

200 mm

100 mm

Surf redfish


250 mm

100 mm

Tigerfish / Leopardfish

Bohadschia argus

300 mm

150 mm

White snakefish

Holothuria leucospilota

400 mm

200 mm

White teatfish


350 mm

200 mm

300 mm

270 mm

1

320 mm2

Listed in the Tonga National Sea Cucumber Fishery Management and Development Plan. Listed in the Fisheries (Conservation and Management) Regulations 1994.


References Bertram I., Moore B. and Malimali S. 2015. Tonga sea cucumber fishery advisory note. Secretariat of the Pacific Community, Noumea, New Caledonia, and Fisheries Division, Ministry of Agriculture and Food, Forests and Fisheries, Government of Tonga.

Pakoa K.M., Ngaluafe P.V., Lotoahea T., Matoto S.V. and Bertram I. 2013a. The status of Tonga’s sea cucumber fishery, including an update on Vava’u and Tongatapu. Secretariat of the Pacific Community, Noumea, New Caledonia.

Chuwen B.M., Potter I.C., Hall N.G., Hoeksema S.D. and Laurenson L.J.B. 2011. Changes in catch rates and length and age at maturity but not growth, of an estuarine plotosid (Cnidoglanis microcephalus) after heavy fishing. Fisheries Bulletin 109:247–260.

Pakoa K., Saladrau W., Lalavanua W., Valotu D., Tuinasavusavu I., Sharp M. and Bertram I. 2013b. The status of sea cucumber resources and fisheries management in Fiji. Secretariat of the Pacific Community, Noumea, New Caledonia.

Conand C. 1993. Reproductive biology of the holothurians from the major communities of the New Caledonia Lagoon. Marine Biology 116:439–450.

Pakoa K., Friedman K., Moore B., Tardy E. and Bertram I. 2014. Assessing tropical marine invertebrates: A manual for Pacific Island resource managers. Secretariat of the Pacific Community, Noumea, New Caledonia.

Conand C. 2004. Sexual cycle of three commercially important holothurian species (Echinodermata) from the lagoon of New Caledonia. Bulletin of Marine Science 31:523–543. Conand C. and Sloan N.A. 1989. World fisheries for echinoderms. p 647–663. In: Marine invertebrate fisheries: Their assessment and management. Caddy J.F. (ed). John Wiley & Sons, New York.

Plagányi E.E., Skewes T, Murphy N, Pascual R, and Fischer M. 2015. Crop rotations in the sea: Increasing returns and reducing risk of collapse in sea cucumber fisheries. PNAS 112: 6760–6765. Preston G.L. and Lokani P. 1990. Report of a survey of the sea cucumber resources of Ha’apai, Tonga June 1990. South Pacific Commission, Noumea, New Caledonia.

Friedman K., Purcell S., Bell J. and Hair C. 2008. Sea cucumber fisheries: A manager’s toolbox. Australian Centre for International Agricultural Research. Canberra, Australia.

Purcell S.W. 2010. Managing sea cucumber fisheries with an ecosystem approach. Lovatelli A, Vasconcellos M and Ye Y (eds.). FAO Fisheries and Aquaculture Technical Paper 520. FAO, Rome.

Friedman K., Eriksson H., Tardy E. and Pakoa K. 2011. Management of sea cucumber stocks: Patterns of vulnerability and recovery of sea cucumber stocks impacted by fishing. Fish and Fisheries 12:75–93.

Purcell S.W. 2014. Processing sea cucumbers into bechede-mer: A manual for Pacific Island fishers. Southern Cross University (Lismore, NSW, Australia) and the Secretariat of the Pacific Community (Noumea, New Caledonia).

Gillett R. 2017. A review of the special management areas in Tonga. FAO Fisheries and Aquaculture Circular No. 1137. FAO, Apia, Samoa. Kinch J., Purcell S., Uthicke S. and Friedman K. 2008. Papua New Guinea: A hot spot of sea cucumber fisheries in the Western Central Pacific: In: Sea cucumbers: A global review of fisheries and trade. Toral-Granda V., Lovatelli A. and Vasconcellos M. (eds). FAO Technical Paper. No. 516:57–77. Lokani P., Matoto S.V. and Ledua E. 1996. Survey of sea cucumber resources at Ha’apai, Tonga, May/June 1996. South Pacific Commission, Noumea, New Caledonia. MacTavish T., Stenton-Dozey J., Vopel K. and Savage C. 2012. Deposit-feeding sea cucumbers enhance mineralization and nutrient cycling in organically enriched coastal sediments. PLOS One 7: e50031. Moore B.R., Stapley J.M., Williams A.J. and Welch D.J. 2017. Overexploitation causes profound demographic changes to the protandrous hermaphrodite king threadfin (Polydactylus macrochir) in Queensland’s Gulf of Carpentaria, Australia. Fisheries Research 187:199–208.

Purcell S.W., Gossiun H. and Agudo N.N. 2009. Status and management of the sea cucumber fishery of la Grande Terre, New Caledonia. Programme ZoNéCo. WorldFish Center Studies and Review No. 1901. The WorldFish Center, Penang, Malaysia. Ricker W.E. 1981. Changes in the average size and average age of Pacific salmon. Canadian Journal of Fisheries and Aquatic Sciences 38:1636–1656. Shiell G.R. and Uthicke S. 2006. Reproduction of the commercial sea cucumber Holothuria whitmaei (Holothuroidea: Aspidochirotida) in the Indian and Pacific Ocean regions of Australia. Marine Biology 148:973–986. Tonga Department of Statistics. 2015. Tonga Statistics at a Glance. http://tonga.prism.spc.int/#population-statistics-including-administrative-information-and-statistical-tabulation-of-the-2011. Last accessed 1 August 2017.


49

Appendix 1. Pacific regional reference densities for healthy stocks (from Pakoa et al. 2014). Reference densities (ind/ha) Manta RBt; SBt

Common name

Scientific name

Lollyfish

Holothuria atra

2,400

5,600*

Greenfish


1,000

3,500**

Chalkfish

Bohadschia similis

-

1,400***

Snakefish

Holothuria coluber

350

1,100*

Sandfish

Holothuria scabra

-

700***

Pinkfish

Holothuria edulis

250

260*

Surf redfish


20

200**

Brown sandfish


160

100*

Hairy blackfish

Actinopyga miliaris

-

150***

Curryfish

Stichopus herrmanni

130

100*

Tigerfish / Leopardfish

Bohadschia argus

50

120**

Flowerfish


50

100**

Black teatfish

Holothuria whitmaei

10

50*

Prickly redfish

Thelenota ananas

10

30**

Amberfish

Thelenota anax

20

-

White teatfish


Elephant trunkfish


Stonefish

Actinopyga lecanora

-

20*

10

10*

-

10*

RBt = reef benthos transect; SBt = soft benthos transect * = RBt and SBt combined; ** = RBt only; ***= SBt only.

Appendix 2. Comparison of survey coverage among the 2016 survey and previous surveys. Comparison of coverage of the 2016 survey and previous surveys by Pakoa et al. (2013) for Vava’u and Tongatapu in 2010–2011 and Pakoa et al. (unpublished) for Ha’apai in 2014. (Open refers to areas open to fishing; SMA refers to special management areas (including fish habitat reserves).

Vava’u Manta tow 1 station = 3,600 m2

Sea cucumber day survey (SCDS) 1 station* = 1,944 m2 Reef front search (RFS) 1 station* = 3,288 m2 Reef benthos transect(RBt) 1 station = 240 m2

Ha’apai

Tongatapu

2010–20111

2016

20142

2016

2010–2011

2016

No. stations: 16

No. stations: 19 -Open: 16 -SMA: 3



No. stations: 10


Area surveyed: 57,600 m2






No. stations: 15


No. stations: 0


No. stations: 14




Area surveyed: 0 m2




No. stations: 12


No. stations: 0

No. stations: 0

No. stations: 23




Area surveyed: 0 m2

Area surveyed: 0 m2



No. stations: 28




No. stations: 0






Area surveyed: 0 m2


*RFS: mean transect size used for density calculations = 137 m long x 4 m wide; SCDS: mean transect size used for density calculations = 81 m long x 4 m wide. 1 Pakoa et al. (2013) 2 Pakoa et al. (unpublished data)

50


Appendix 3. Densities of sea cucumber species observed during manta tow surveys. Site

Species common name

Overall mean density (ind/ha)

SE

n

Present mean density (ind/ha)

Vava’u Open

Amberfish

2.26

1.67

16

18.06

Vava’u Open

Black teatfish

0.17

0.17

16

2.78

SE_P 6.94

n_P

%_P

2

13

1

6

Vava’u Open

Brown sandfish

35.07

12.31

16

37.41

12.92

15

94

Vava’u Open

Curryfish

6.94

2.08

16

10.10

2.49

11

69

Vava’u Open

Dragonfish

4.34

4.34

16

69.44

1

6

Vava’u Open

Elephant trunkfish

Vava’u Open

Greenfish

1.22

0.57

16

4.86

0.69

4

25

63.89

18.11

16

73.02

19.53

14

88

Vava’u Open

Hairy blackfish

0.35

0.35

16

5.56

1

6

Vava’u Open

Lollyfish

1048.26

411.11

16

1118.15

433.10

15

94

173.44

68.78

16

308.33

102.82

9

56

47.22

18.58

16

68.69

24.61

11

69

Vava’u Open

Pinkfish

Vava’u Open

Snakefish

Vava’u Open


0.35

0.35

16

5.56

1

6

Vava’u Open

Surf redfish

0.17

0.17

16

2.78

1

6

Vava’u Open

Tiger-tail

0.17

0.17

16

2.78

1

6

Vava’u Open

Tigerfish

11.81

3.08

16

14.53

13

81

Vava’u Open

White teatfish

Vava’u SMA

Brown sandfish

Vava’u SMA

Curryfish

3.36

0.17

0.17

16

2.78

1

6

219.44

110.22

3

329.17

18.06

2

67

4.63

2.45

3

6.94

1.39

2

67

Vava’u SMA

Elephant trunkfish

1.85

1.85

3

5.56

1

33

Vava’u SMA

Greenfish

8.33

8.33

3

25.00

1

33

Vava’u SMA

Lollyfish

2184.26

1350.55

3

2184.26

1350.55

3

100

15.80

Vava’u SMA

Pinkfish

27.78

15.80

3

27.78

Vava’u SMA

Snakefish

2.78

2.78

3

8.33

Vava’u SMA

Tigerfish

3.70

2.45

3

5.56

Ha’apai Open

Amberfish

3.63

1.99

17

12.33

Ha’apai Open

Black teatfish

0.16

0.16

17

2.78

Ha’apai Open

Brown sandfish

0.98

0.67

17

5.56

Ha’apai Open

Dragonfish

0.16

0.16

17

2.78

3

100

1

33

2.78

2

67

5.19

5

29

1

6

2.78

3

18

1

6

Ha’apai Open

Elephant trunkfish

0.49

0.26

17

2.78

0.00

3

18

Ha’apai Open

Greenfish

67.06

46.95

17

142.49

95.77

8

47

Ha’apai Open

Lollyfish

151.47

98.69

17

257.50

162.48

10

59

0.69

Ha’apai Open

Prickly redfish

0.82

0.40

17

3.47

Ha’apai Open

Snakefish

0.49

0.49

17

8.33

Ha’apai Open

Tigerfish

2.78

0.92

17

5.90

Ha’apai Open

White teatfish

0.33

0.22

17

2.78

4

24

1

6

1.22

8

47

0.00

2

12


51

Site

Species common name

Ha’apai SMA

Black teatfish

Ha’apai SMA

Brown sandfish

Ha’apai SMA

Curryfish

Ha’apai SMA

Elephant trunkfish

Ha’apai SMA

Greenfish

Ha’apai SMA

Lollyfish


SE

n


SE_P

n_P

%_P

1.01

0.77

11

5.56

2.78

2

18

11.62

7.48

11

31.94

17.22

4

36

0.25

0.25

11

2.78

1

9

1.26

1.02

11

6.94

4.17

2

18

48.74

20.22

11

107.22

26.11

5

45

1250.76

819.81

11

1375.83

895.73

10

91

Ha’apai SMA

Pinkfish

8.08

6.32

11

29.63

20.31

3

27

Ha’apai SMA

Snakefish

8.59

5.17

11

31.48

11.38

3

27

Ha’apai SMA

Surf redfish

0.25

0.25

11

2.78

1

9

Ha’apai SMA

Tigerfish

4.04

2.49

11

8.89

Ha’apai SMA

White teatfish

0.25

0.25

11

2.78

Tongatapu Open

Amberfish

0.85

0.49

13

3.70

Tongatapu Open

Black teatfish

Tongatapu Open

Brown sandfish

Tongatapu Open

Chalkfish

4.84 0.93

5

45

1

9

3

23

0.43

0.29

13

2.78

0.00

2

15

10.68

3.76

13

13.89

4.42

10

77

0.21

0.21

13

2.78

1

8

Tongatapu Open

Curryfish

8.97

4.36

13

19.44

Tongatapu Open

Deepwater redfish

0.21

0.21

13

2.78

Tongatapu Open

Elephant trunkfish

2.14

1.22

13

9.26

Tongatapu Open

Golden sandfish

6.41

5.55

13

41.67

7.62

6

46

1

8

2.45

3

23

30.56

2

15

Tongatapu Open

Greenfish

29.49

9.65

13

34.85

10.64

11

85

Tongatapu Open

Lollyfish

1121.37

512.97

13

1325.25

588.35

11

85

Tongatapu Open

Pinkfish

125.64

57.67

13

181.48

77.06

9

69

Tongatapu Open

Snakefish

5.13

2.24

13

13.33

3.45

5

38

Tongatapu Open


0.43

0.29

13

2.78

0.00

2

15

Tongatapu Open

Tigerfish

5.34

2.54

13

11.57

4.39

6

46

0.00

Tongatapu SMA

Brown sandfish

Tongatapu SMA

Curryfish

Tongatapu SMA

Deepwater blackfish

2.78

0.00

2

2.78

2

100

38.89

38.89

2

77.78

1

50

5.56

5.56

2

11.11

1

50

Tongatapu SMA

Elephant trunkfish

5.56

5.56

2

11.11

1

50

Tongatapu SMA

Greenfish

181.94

168.06

2

181.94

168.06

2

100

Tongatapu SMA

Lollyfish

72.22

30.56

2

72.22

30.56

2

100

33.33

Tongatapu SMA

Pinkfish

72.22

33.33

2

72.22

2

100

Tongatapu SMA

Snakefish

6.94

6.94

2

13.89

1

50

Tongatapu SMA


1.39

1.39

2

2.78

1

50

Tongatapu SMA

Tigerfish

4.17

4.17

2

8.33

1

50

n = number of stations; Present mean density = mean density for stations where species is present; SE_P = standard error for stations where species is present; n_P = number of stations were species is present; %_P = percentage of stations where species is present.

52


Appendix 4. Densities of sea cucumber species observed during reef benthos transects. Site

Species common name


SE

n


SE_P

n_P

%_P

Vava’u Open

Greenfish

284.72

190.65

18

465.91

304.42

11

61

Vava’u Open

Lollyfish

3111.11

1388.64

18

3111.11

1388.64

18

100

Vava’u Open

Pinkfish

39.35

25.54

18

236.11

100.15

3

17

Vava’u Open

Snakefish

16.20

7.64

18

58.33

16.67

5

28

Vava’u Open

Surf redfish

4.63

4.63

18

83.33

1

6

Vava’u Open

Tigerfish

2

11

Vava’u SMA

Deepwater redfish

1

8

Vava’u SMA Vava’u SMA

9.26

7.19

18

83.33

10.42

10.42

12

125.00

41.67

Greenfish

774.31

386.38

12

1327.38

588.93

7

58

Lollyfish

1583.33

716.35

12

1583.33

716.35

12

100

Vava’u SMA

Pinkfish

13.89

7.83

12

55.56

13.89

3

25

Vava’u SMA

Prickly redfish

3.47

3.47

12

41.67

1

8

Vava’u SMA

Snakefish

24.31

14.01

12

97.22

27.78

3

25

Vava’u SMA

Tigerfish

24.31

6.19

12

41.67

0.00

7

58

Ha’apai Open

Elephant trunkfish

1.60

1.60

26

41.67

1

4

Ha’apai Open

Greenfish

97.76

53.16

26

363.10

166.35

7

27

Ha’apai Open

Lollyfish

250.00

102.95

26

406.25

156.44

16

62

Ha’apai Open

Prickly redfish

1.60

1.60

26

41.67

1

4

Ha’apai Open

Snakefish

1.60

1.60

26

41.67

1

4

Ha’apai Open

Tigerfish

4.81

2.66

26

41.67

3

12

Ha’apai SMA

Brown sandfish

4.90

4.90

17

83.33

1

6

Ha’apai SMA

Dragonfish

4.90

4.90

17

83.33

1

6

Ha’apai SMA

Greenfish

166.67

80.53

17

566.67

177.56

5

29

0.00

Ha’apai SMA

Lollyfish

1210.78

603.18

17

2058.33

951.69

10

59

Ha’apai SMA

Pinkfish

66.18

40.90

17

375.00

133.94

3

18

Ha’apai SMA

Snakefish

4.90

3.36

17

41.67

0.00

2

12

Ha’apai SMA

Tigerfish

2.45

2.45

17

41.67

1

6

Tongatapu Open

Brown sandfish

3.68

2.06

34

41.67

0.00

3

9

41.67

Tongatapu Open

Curryfish

4.90

3.84

34

83.33

2

6

Tongatapu Open

Deepwater redfish

1.23

1.23

34

41.67

1

3

Tongatapu Open

Dragonfish

1.23

1.23

34

41.67

1

3

Tongatapu Open

Elephant trunkfish

1.23

1.23

34

41.67

1

3

Tongatapu Open

Greenfish

120.10

39.13

34

240.20

67.18

17

50

Tongatapu Open

Lollyfish

1267.16

303.08

34

1595.68

355.89

27

79

Tongatapu Open

Pinkfish

198.53

83.11

34

450.00

169.77

15

44

Tongatapu Open

Prickly redfish

1.23

1.23

34

41.67

1

3

Tongatapu Open

Snakefish

40.44

20.02

34

114.58

12

35

Tongatapu Open

Stonefish

1.23

1.23

34

41.67

1

3

Tongatapu Open

Tiger-tail

14.71

6.31

34

83.33

18.63

6

18

Tongatapu Open

Tigerfish

8.58

2.93

34

41.67

0.00

7

21

Tongatapu SMA

Curryfish

32.74

21.92

14

152.78

73.49

3

21

51.32

Tongatapu SMA

Golden sandfish

2.98

2.98

14

41.67

1

7

Tongatapu SMA

Greenfish

214.29

84.57

14

333.33

114.53

9

64

Tongatapu SMA

Lollyfish

452.38

202.80

14

487.18

215.81

13

93

Tongatapu SMA

Pinkfish

148.81

72.53

14

297.62

124.15

7

50

13.89

Tongatapu SMA

Snakefish

11.90

6.81

14

55.56

3

21

Tongatapu SMA

Tiger-tail

41.67

41.67

14

583.33

1

7

Tongatapu SMA

Tigerfish

2.98

2.98

14

41.67

1

7

n = number of stations; Present mean density = mean density for stations where species is present; SE_P = standard error for stations where species is present; n_P = number of stations were species is present; %_P = percentage of stations where species is present. The status of sea cucumbers in the Kingdom of Tonga in 2016

53

Appendix 5. Mean lengths of sea cucumber species observed at each site.

54

Site

Species common name

Mean length (mm)

Vava’u Open

Amberfish

583

20

20

49

Vava’u Open

Black teatfish

275

53

4

7

Vava’u Open

Brown sandfish

236

6

12

223

Vava’u Open

Curryfish

327

10

19

64

Vava’u Open

Elephant trunkfish

426

40

14

29

Vava’u Open

Golden sandfish

308

19

5

9

Vava’u Open

Greenfish

168

4

123

616

Vava’u Open

Lollyfish

146

3

458

7399

Vava’u Open

Pinkfish

184

3

294

1440

Vava’u Open

Prickly redfish

300

1

3

Vava’u Open

Snakefish

300

1

304

Vava’u Open

Surf redfish

185

16

4

14

Vava’u Open

Tiger-tail

135

11

6

21

Vava’u Open

Tigerfish

354

18

16

90

Vava’u SMA

Amberfish

542

32

10

15

Vava’u SMA

Brown sandfish

258

13

15

257

Vava’u SMA

Curryfish

350

1

7

Vava’u SMA

Deepwater redfish

182

7

3

3

Vava’u SMA

Elephant trunkfish

430

20

2

6

Vava’u SMA

Greenfish

153

3

190

345

Vava’u SMA

Lollyfish

150

3

312

2890

Vava’u SMA

Pinkfish

190

13

19

98

Vava’u SMA

Prickly redfish

440

1

2

Vava’u SMA

Tigerfish

339

15

26

Vava’u SMA

White teatfish

250

1

1

Ha’apai Open

Amberfish

654

12

20

42

Ha’apai Open

Elephant trunkfish

424

27

11

14

Ha’apai Open

Flowerfish

420

1

1

Ha’apai Open

Greenfish

161

5

63

471

Ha’apai Open

Lollyfish

209

7

161

1105

11

Ha’apai Open

Pinkfish

202

Ha’apai Open

Prickly redfish

330

Ha’apai Open

Tigerfish

341

SE (mm)

20

No. specimens measured

Total no. specimens observed

7

7

1

6

24

13

31

Ha’apai Open

White teatfish

190

1

3

Ha’apai SMA

Amberfish

360

10

2

3

Ha’apai SMA

Brown sandfish

248

27

6

52

Ha’apai SMA

Curryfish

270

1

3

Ha’apai SMA

Deepwater blackfish

340

1

1

Ha’apai SMA

Dragonfish

110

2

2


40

Site

Species common name

Mean length (mm)

SE (mm)

No. specimens measured

Total no. specimens observed

Ha’apai SMA

Elephant trunkfish

281

29

4

9

Ha’apai SMA

Golden sandfish

313

13

4

4

Ha’apai SMA

Greenfish

154

5

75

268

Ha’apai SMA

Lollyfish

173

5

212

5473

Ha’apai SMA

Pinkfish

171

6

36

74

Ha’apai SMA

Prickly redfish

330

30

2

2

Ha’apai SMA

Stonefish

160

1

1

Ha’apai SMA

Tigerfish

319

32

5

21

Ha’apai SMA

White teatfish

290

10

2

3

Tongatapu Open

Amberfish

563

36

17

21

Tongatapu Open

Black teatfish

255

1

3

Tongatapu Open

Brown sandfish

251

7

33

85

Tongatapu Open

Curryfish

292

16

17

59

Tongatapu Open

Deepwater redfish

160

1

2

Tongatapu Open

Dragonfish

153

27

3

4

Tongatapu Open

Elephant trunkfish

351

12

21

32

Tongatapu Open

Greenfish

163

5

95

246

Tongatapu Open

Lollyfish

165

2

768

6336

Tongatapu Open

Pinkfish

172

3

263

897

15

Tongatapu Open

Prickly redfish

395

Tongatapu Open

Stonefish

175

2

2

1

2

Tongatapu Open

Tiger-tail

127

12

3

12

Tongatapu Open

Tigerfish

Tongatapu Open

White teatfish

332

21

18

43

313

29

4

4

Tongatapu SMA

Amberfish

449

46

11

11

Tongatapu SMA

Black teatfish

160

1

1

Tongatapu SMA

Brown sandfish

170

1

3

Tongatapu SMA

Curryfish

256

20

12

40

Tongatapu SMA

Elephant trunkfish

330

32

8

12

Tongatapu SMA

Golden sandfish

350

1

1

Tongatapu SMA

Greenfish

159

5

72

292

Tongatapu SMA

Lollyfish

217

7

147

234

Tongatapu SMA

Pinkfish

166

6

79

136

Tongatapu SMA

Prickly redfish

270

1

2

Tongatapu SMA

Snakefish

680

1

19

Tongatapu SMA

Surf redfish

240

1

5

Tongatapu SMA

Tigerfish

318

15

5

8

Tongatapu SMA

Tiger-tail

155

8

14

14

Tongatapu SMA

White teatfish

213

17

4

4


55

Appendix 6.

A simplified approach to calculating harvestable stock estimates (amended from Pakoa et al. 2014).

This example provides information on total and harvestable stock size calculations for sea cucumber species by suitable habitat area. For the purposes of this example, the following figures have been used: Average density estimate for Species A

= 1,000±200 ind/ha

Regional reference density for Species A

= 500 in/ha

Standard deviation for Species A

= 217.12

Number of stations surveyed

=8

Area of habitat for Species A

= 102 ha

Proportion of population over legal length

= 0.55 (55% of individuals)

Step 1:

Undertake a survey to determine population density for individual species. Surveys should be stratified according to habitat type. Calculate average density for Species A from the densities observed at each of the survey stations.

Step 2:

Compare species’ average densities with regional reference densities provided in Pakoa et al (2014). Because the average density of Species A is above regional reference densities, for purposes of this example it is considered suitable for harvest. Species observed in densities below regional reference densities should not be considered for harvest.

Step 3:

Determine lower 95% confidence interval (CI) of the average density estimate using the formula =confidence(alpha, standard_ dev, size) (where alpha = the significance level you wish to use to calculate the confidence level [in this case alpha = 0.05], standard_dev = standard deviation of individual station density estimates, size = number of stations surveyed). Subtract this value from the average density estimate.

Step 4:

95% CI for Species A Lower density estimate

= = = =

confidence(0.05, 217.12, 8) 150.46 1000 – 150.46 849.54

Determine area of suitable habitat (using GIS). Multiply this area by 0.8 to get 80% of total area.

Step 5:

80% of habitat

= 102 x 0.8 = 81.6 ha

Multiply the 80% of habitat area estimate by the species’ lower 95% CI average density estimate to get estimated stock size.

Step 6:

Estimate stock size

= 81.6 x 849.54 = 69,323

Determine the harvestable stock estimate by multiplying the estimate stock size by the proportion of the population that is mature or over legal size to get adult (or legal) stock size.

Step 7:

Legal stock size

= 69,323 x 0.55 = 38,128

Multiply the adult (or legal) stock size estimate by desired harvestable proportion (e.g. 30%) to get harvestable stock size. Harvestable stock size

= 38,128 x 0.3 = 11,438 individuals

Total quotas could then be divided among fishers and fishing communities if individual quotas are desired.

56
