ICES Journal of Marine Science (2011), 68(8), 1679–1688. doi:10.1093/icesjms/fsr101
Using fishery-dependent data to inform the development and operation of a co-management initiative to reduce cod mortality and cut discards S. J. Holmes 1 *, N. Bailey 1, N. Campbell 1, R. Catarino 1, K. Barratt 2, A. Gibb 2, and P. G. Fernandes 1 1
Marine Scotland Science, Marine Laboratory, PO Box 101, 375 Victoria Road, Aberdeen AB11 9DB, UK Marine Scotland Science, Pentland House, 47 Robb’s Loan, Edinburgh EH14 1TY, Scotland, UK
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*Corresponding Author: tel: +44 1224 295507; fax: +44 1224 295511; e-mail:
[email protected] Holmes, S. J., Bailey, N., Campbell, N., Catarino, R., Barratt, K., and Gibb, A., and Fernandes, P. G. 2011. Using fishery-dependent data to inform the development and operation of a co-management initiative to reduce cod mortality and cut discards. – ICES Journal of Marine Science, 68: 1679 –1688. Received 14 October 2010; accepted 18 April 2011; advance access publication 8 July 2011.
The Scottish conservation credits scheme is a voluntary programme introduced in 2008, designed to reduce mortality and discarding of cod in line with EU Common Fisheries Policy management objectives. The scheme was expanded in 2009, building on the initial elements of real-time closures (RTCs) and gear requirements. Various measures were agreed in a co-management framework involving fishers, non-governmental organizations, government officials, and scientists. The main objective was to encourage cod avoidance and the reduction of cod discards using spatial tools such as RTCs and seasonal closures, along with gear options that reduce cod capture. The scheme was incentivized by rewarding participation with additional days at sea. Real-time monitoring was carried out with extensive use of fishery-dependent information, allowing management to be adapted as required and to address emerging problems. The use of vessel monitoring system data, logbook records, fishers’ knowledge, and observer data is described in terms of implementing and assessing the scheme. Compliance with the closure elements of the scheme was judged to have been good, and estimated catch rates by the Scottish fleet met target criteria, but the assessed catch savings of cod from RTCs were less than predicted. Modifications to the scheme were introduced for 2010, reflecting improved knowledge and experience. Keywords: cod, conservation credits, discards, real-time closures, VMS data.
Introduction The Scottish conservation credits (SCC) scheme is a voluntary programme introduced in 2008, designed to reduce mortality and discarding of cod, in line with the management objectives of the Common Fisheries Policy of the European Union (EU). It was based on gear requirements and real-time closures (RTCs), conceived to discourage vessels from operating in areas of high cod abundance. RTCs applied to areas closed for 21 d when catch rates of cod, detected by the marinemonitoring and enforcement agency (Marine Scotland Compliance), exceeded a trigger level. The scheme was incentivized by rewarding participating skippers with additional days at sea. A new long-term management plan for cod was introduced for 2009 (CEC, 2008), in which the means of controlling fishing effort changed considerably (CEC, 2009). Fishing gears are categorized into effort groups according to gear design, and are allocated, mesh size. Based on historical records for national fleets, annual effort quotas in terms of vessel kW-days are allocated to EU Member States. Depending on the assessed state of the cod stocks relative to reference biomass levels, the management plan specifies the reduction in fishing mortality to be achieved in the # Crown
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following year through adjusted total allowable catches (TACs) and, for effort groups most significant in catching cod, corresponding effort adjustments. If effort reductions are imposed, the cod long-term plan permits the fishing effort in a group to be increased up to the level allocated the previous year, if the fleet participates in a cod-avoidance or discard-reduction plan expected to deliver at least as great a reduction in mortality as anticipated from the effort cut. The 2009 target of the management plan was a 25% reduction in fishing mortality (F ) compared with 2008. The SCC scheme aimed to achieve the reduction in cod mortality through the measures described below.
Compulsory RTCs for Scottish vessels Analysis of 2008 data from a vessel monitoring system (VMS) identified vessels that had been fishing in RTC areas immediately before closure. Comparing the landed cod weights before and during closures provided estimates of “saved landings” per RTC and, after applying a discard rate estimated from observed trips, “saved catch” per RTC. The target number of RTCs was increased to the level considered capable of delivering an 11% reduction in cod fishing mortality.
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The governing principles of the RTC element of the scheme were: (i) A maximum of 12 closures in place at any one time. Each closure area was equivalent in size to a square 7.5 × 7.5 nautical miles, or 1/16th of an ICES statistical rectangle at North Sea latitudes. Closure shapes, however, were only restricted to having six or fewer vertices. (ii) Closures applied for 21 d and then were automatically reopened. (iii) The seas around Scotland were divided into four zones by lines of latitude (588N in the west; 58830′ N in the east) and longitude (48W; Figure 1). The purpose of the zones was to prevent the impact of closures affecting vessels operating from any one port disproportionately. (iv) In general, there would always be at least one closure in each zone. (v) Within any “commercial impact zone” (CIZ, up to 25 nautical miles around a closure), no more than three closures could be adopted at any one time. (vi) Closures within 12 miles of the coast could be smaller and of different shape, taking account of geography, community needs, and fleet structure. They were always based on at-sea physical inspections. (vii) Closure triggers were: (a) Physical inspections of catches revealing more than 40 cod per hour of fishing. This preset trigger level was expected to cause ten closures over a year, based on a frequency distribution of observed catch rates from the previous year. (b) Analysis of landings and VMS data identifying, for each RTC zone, 25 areas of RTC size with the highest landings per unit effort (lpue) in that zone. Each VMS analysis
would be assessed by Marine Scotland Compliance, who could recommend up to ten closures at a time in total, bearing in mind principles (i) –(vi). The limit of ten closures was to allow for those triggered through at-sea inspections.
Seasonal closures and amber areas Seasonal closures were non-permanent but intended to be in place longer than RTCs. They were identified through a combination of fishers’ knowledge and analysis of VMS data. Amber areas were zones with high cod abundance but below the level that would trigger an RTC. Their definitions were updated quarterly based on data from the same period the previous year. Vessel avoidance of these areas was voluntary but incentivized by awarding additional days at sea.
Technical gear measures Fishers could adopt various gear options designed to reduce the catchability of cod. They were voluntary and incentivized by additional days at sea. The design, appraisal, and modification of the SCC scheme were undertaken by the Conservation Credits Steering Group (CCSG), which met monthly during 2009. It comprised fishery managers, fishery scientists, officers from Marine Scotland Compliance, fisher representatives, and non-governmental organizations. Vessels choosing not to adopt voluntary measures were allocated less effort to ensure that the overall 25% reduction in cod mortality could be achieved. There were various administrative penalties to ensure compliance, including a deduction of 5 d from the effort allocation for fishing within an RTC, and loss of any extra award days if found fishing within an amber area. The compulsory elements of the scheme were only legally binding on vessels registered in Scotland, but administrations from other countries were informed of all closures and asked to encourage their vessels to avoid those areas. This paper describes the use of fishery-dependent data to define and evaluate the success of seasonal, amber, and RTCs, and the overall SCC scheme in reducing cod mortality, particularly through reduction of discards.
Use of fishery data in the SCC scheme Defining RTCs using VMS and logbook data To help maintain 12 active RTCs at any one time, a combined VMS and logbook analysis was conducted as closures became due for reopening. Data were taken from a 14-d period leading up to the time of analysis. To allow consideration by Marine Scotland Compliance, there was usually a 1- or 2-d gap between the 14-d period used for lpue analysis and the implementation of new RTCs.
Data availability and filtering
Figure 1. Map showing the determination of amber areas (polygons) for management period 2 (May – July) in 2009. Highlighted squares are the top 15% in terms of cod lpue values for the same months in 2008. Also shown is the permanent closure known as the windsock (hatched area). Dashed lines indicate the borders of the four zones over which lpue results were calculated.
VMS data were available from the Scottish Government’s Fisheries Information Network (FIN) database for all UK vessels fishing in Scottish waters and all voyages landing into Scotland. Logbook data were taken for all voyages using whitefish or Nephrops trawls from a separate FIN table. Linked VMS/logbook data (cross-referenced using the vessel RSS number) were limited to Scottish vessels and boats 15 m or longer landing into Scotland. Data were filtered to include only cod. For each trip, daily totals of recorded cod landings and VMS pings were determined. Pings
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Landings per unit effort Each VMS ping was assigned to a rectangle defined by dividing standard ICES rectangles into 16 equal parts. The ping interval was generally 2 h but did vary; in Norwegian waters, it was 1 h. Fishing pings were weighted by the time since the last ping, with the first one of a voyage having a default weight of 2 h. To avoid distortions arising from very large or small weights, those over 2 h 9 min were allocated the same weight as the nearest accepted ping, and the minimum weight was set to 1 h. The physical weight of cod recorded in the logbook for each day of a trip was allocated to each VMS ping for that date according to the statistical weight of each fishing ping. Therefore, the cod landings, Lt,s, of a particular trip t, from square s, were calculated from Lt,s =
lt,d Pt,d,s Pt,d
,
(1)
where lt,d is the landings recorded in the voyage logbook for day d of trip t, Pt,d the total weights of the fishing pings for that voyage on that day, and Pt,d,s the corresponding total for those pings in square s. Over the 14-d evaluation period, cod weights and ping weights were aggregated over all voyages within each square. A measure of the lpue for each square was then calculated as Lt,s lpues = t , P t t,s
(2)
where Pt,s = d Pt,d,s . Within each of the four RTC zones, the squares were ranked according to lpue, and the top 25 in each zone were notified to Marine Scotland Compliance to make final proposals for closures. Squares with only one ping were excluded to avoid distortion effects. The final areas chosen were not necessarily the same shape as the squares. For example, oil pipelines have been identified as locations where cod congregate, and a closed area could be defined to reflect this.
Amber areas Amber areas were updated quarterly using VMS-derived lpue values obtained from the same months in the previous year. Within each zone, squares were ranked by lpue, with the top 15% highlighted as potential amber areas (Figure 1). Defined amber area polygons were chosen according to the following criteria: (i) encompassed the highest lpue values; (ii) minimized the complexity of the polygon, with a minimal set of latitudes and longitudes, so areas could therefore include white space (low lpue) once the vertices were joined; (iii) combined contiguous squares to produce fewer, large areas in preference to many small ones; each area consisted of more than four squares.
In common with many fishery-management measures updated yearly, the SCC scheme runs from 1 February to 31 January. Therefore, the management periods of the amber areas did not match calendar quarters, but were rather displaced by 1 month.
Seasonal closures Seasonal closures were introduced to make use of fisher knowledge and to provide protection to known aggregations of cod. Initially, the industry proposed the location, size, shape, and duration of such closures, but they were finally decided upon after analysis of VMS fishing pings around the proposed closure dates in the previous year, and dialogue between scientists and fishers. Initially, a single closure in the area known as the Long Hole was applied from 1 December 2008 (Figure 2). Information from industry suggested that closure of the Long Hole fishing grounds could reduce bycatches of cod while still allowing relatively unrestricted access to surrounding Nephrops stocks; observer data collected by Marine Scotland Science (MSS) supported this. The closure was initially set until 31 March 2009, although reopening depended on a test haul conducted by a commercial vessel and observed by MSS scientists. If a catch per unit effort (cpue) threshold of 200 cod per hour was exceeded, the closure would be extended by a month and the sampling haul repeated. A further three seasonal closures were identified to protect predictable but temporary aggregations of cod. Unlike the Long Hole, those areas were automatically reopened.
Use of fishery data to assess the efficacy of the scheme Assessment of the SCC closures can be considered in terms of vessels avoiding RTCs, seasonal closures, and amber areas (avoidance), and their effect on the fishing mortality of cod (effectiveness). The avoidance of RTCs was assessed by comparing VMS fishing pings, and the number of associated vessels, before, during, and after each closure. Analysis of 14-d periods before and after a closure was chosen to match the number of days used by the VMS –lpue method to define areas for possible closure. Seasonal closures were considered in a similar manner. Avoidance of amber areas was voluntary. Vessels opting to avoid them may, of course, not normally fish there. The likely impact of amber areas can be judged by comparing the proportion of cod landings associated with vessels inside and outside the scheme. VMS data when available were used to compare the fishing activity in 2009 and 2008 for Scottish vessels inside the scheme. The appropriateness of each amber area was considered by overlaying onto the amber areas the top 15% of lpue rectangles identified from 2009 data. The temporal stability of high-lpue squares was considered by comparing (i) adjacent management periods (intra-annual stability), and (ii) the same months in adjacent years (interannual stability). In addition, the average VMS-derived lpue of cod from inside all amber areas was compared with the average lpue from outside the areas. A simple measure of the RTC contribution to cod avoidance is given by comparing the landings from vessels operating in areas which subsequently became RTCs with those once the RTC was in place and the vessels had moved away. Assuming a constant lpue if they had continued fishing in the RTC, and a consistent ratio between landings and discards, then savings accrue if the vessel moves to areas where the catch rate is lower. The greater
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Figure 2. Map showing seasonal closures (filled black areas) and amber areas implemented in 2009. The colour of amber area borders indicate the management period (Q1– Q4): red, Q1; yellow, Q2; blue, Q3; green, Q4. Coincident boundaries have been slightly displaced for visual clarity. The straight grey lines show zonal boundaries of the RTC scheme.
Figure 3. Map showing RTCs implemented in 2009 as shaded boxes indicating the method that triggered the closure: black, VMS and logbook lpue analysis; white, positive sample from at-sea inspection (.40 cod per hour of fishing); hatched, combination of lpue analysis and positive sample. The straight grey lines show zonal boundaries of the RTC scheme.
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Reducing cod mortality the differential between the catch rate in the RTC and the new location, the greater the saving. Whether through RTCs, seasonal closures, amber areas, or technical measures, the SCC scheme was required to ensure that the cod catch of the Scottish fleet matched the recommendations in the ICES annual stock assessments, as modified by the national quota share, i.e. to deliver the anticipated partial F for the fleet. The catch trajectory of Scottish vessels compared with the annual target was considered as an overall test of the SCC scheme. This was limited to the North Sea, because of uncertainties in the west of Scotland (ICES Division VIa) cod assessment and the sparse observer coverage in the west of Scotland. Landings totals for the gear categories TR1 (bottom trawls and seines of mesh ≥100 mm) and TR2 (bottom trawls and seines of mesh ≥70 and ,100 mm), as defined in CEC (2008), were compiled monthly for 2008 and 2009. Observer data were used to produce a quarterly discard rate for each category.
Results from 2009 Location of RTCs and amber areas In all, 144 RTCs were implemented in 2009; Figure 3 shows the cumulative total of RTCs. The locations of seasonal closures and
amber areas are shown in Figure 2. No closures were deemed appropriate in the SW zone because of the very low lpue values there. The concurrent closure limit (12) was reached briefly on two occasions; the greatest number was in the NE zone. Details of all closures to date, maps of current RTCs and their associated CIZs, amber areas, and a link to the results from at-sea observer sampling of cod have been made available on the Internet at http:/www.scotland.gov.uk/Topics/Fisheries/Sea-Fisheries/ COMPLIANCE/closures/.
Compliance with RTCs, and take-up of amber area avoidance In all, the VMS dataset contained nearly 720 000 fishing pings from 625 vessels. From the 144 RTCs in 2009, the number of closures with zero pings appears small (38% of closures), but instances of only one or two pings during a closure were recorded for another 21 areas. Vessels were generally given a short period of grace once a new RTC was established. Thereafter, they could be asked informally when found in an RTC to encourage compliance, although penalties were enforced if such incursions persisted. Figure 4 presents histograms of the effort changes associated with RTCs. There was less fishing activity during almost all closures compared with the 14-d periods immediately before and
Figure 4. Histograms showing changes in fishing effort associated with RTCs. Number of fishing pings (top panels) and vessels (bottom panels) within RTCs when comparing the periods before and during closure (left panels), and during and after closure (right panels).
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after them. Most closures reduced the fishing pings by around 10 or 20 (equivalent to 10 –40 h trawling), but for some the reduction was well over 100. The converse occurred when areas reopened. Vessel reductions during closures compared with pre-closure were mostly between 1 and 6. Usually, the number of vessels active in an area increased again upon reopening, suggesting that there would have been more fishing had the RTC not been in place. Of the seasonal closures, only the Coral Edge implementation resulted in significantly reduced activity (Table 1). Of the 104 fishing pings recorded during the Papa Bank closure (0.01% of total pings), 100 were from a vessel not required to adhere to the closure, being registered outside Scotland. As a result of the test hauls conducted, the Long Hole remained closed all year. In 2009, a total of 65 vessels notified intention to avoid amber areas. At any one time, between 55 and 60 vessels were participating in the scheme, roughly 10% of those eligible. The proportion of cod landings attributable to VMS-equipped vessels participating or not participating in the scheme changed little between 2008 and 2009 (Figure 5a). Little evidence of altered fishing patterns by participating vessels was seen in VMS maps (not shown).
Table 1. Summary of seasonal closures, with a comparison of fishing activity before, during, and after the closures. Number of fishing pings (vessels) Closure area Long Hole Papa Bank Stanhope Ground Coral Edge
Duration of closure (d) 365 60 69
Pre-closure n/a 15 (4) 21 (3)
During closure 100 (17) 104 (2) 13 (4)
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127 (8)
12 (3)
Post-closure n/a 18 (1) 2 (1) 2 (1)
Durations of the pre- and post-closure periods are 14 d, and n/a indicates not relevant because the closure was in place for the whole of 2009.
Cod landings Estimated catch savings attributable to vessels moving away from RTC areas are greatest in the North Sea where most closures were called (Table 2). Overall, the savings were 430 t of cod landings which, when raised by the discard rate, amount to 707 t of catch.
Location of amber areas Given the low uptake of amber area avoidance, the VMS and lpue data from 2009 provide a qualitative test of the appropriateness of amber area locations. Management period 2 (May –July) highlights a common problem. Some squares with high lpue using data for May–July 2009 (yellow boxes) fell within the amber Table 2. Landings and catch savings (t) arising from Scottish vessels shown by VMS data to move away from RTCs in 2009. Landings Area and pre-RTC quarter (t) North Sea Q1 492 Q2 502 Q3 631 Q4 170 Annual 1 795 West of Scotland Q1 34 Q2 141 Q3 135 Q4 23 Annual 333 Both areas Q1 526 Q2 643 Q3 766 Q4 193 Annual 2 128
Landings during RTC (t)
Landings difference (t)
“Catch” difference (t)
359 496 384 177 1 416
133 6 247 27 379
218 10 405 212 622
54 64 147 17 282
220 77 212 6 51
232 126 219 11 86
413 560 531 194 1 698
113 83 235 21 430
186 135 386 21 707
Figure 5. Scottish vessels equipped with VMS. (a) Proportion of cod landings attributable to vessels participating in the amber area scheme (filled squares) and not participating (open triangles); solid lines, 2009; dashed lines, 2008. (b) lpue values in 2009 from inside (filled squares) and outside (open triangles) amber areas derived from vessels regardless of participation. The average lpue over all trips is shown by filled diamonds. MP, management period.
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Reducing cod mortality area polygons (defined using data from the same months in 2008), but most did not (Figure 6a). The 2009 data result in high-lpue squares that are completely removed from the amber areas defined for that period, e.g. to north and northwest of Shetland. Figure 6b shows 2009 data from February to April, again overlaid on the amber areas implemented in management period
2. Comparing the two panels, the locations of high-lpue squares show little consistency between these adjacent management periods, so defining amber areas for May–July 2009 using data from February to April of the same year (instead of May–July the previous year) would not appear to improve their appropriateness. These results show that the highest lpue values can occur in areas with relatively few fishing pings. Figure 5b, however, demonstrates consistently higher lpue from within amber areas (combined) than elsewhere.
Discard rates and cod-catch trajectory
Figure 6. Maps showing VMS fishing pings (black dots), and the top 15% of squares ranked by lpue (yellow boxes) for (a) May – July 2009, and (b) February– April 2009, overlaid on amber areas (polygons outlined in red) implemented in May–July 2009. The hatched area is a permanent closure, known as the windsock.
Using data from observer trips, discard estimates as a percentage of catch for the TR2 gear type vary (Table 3). This may reflect less sampling coverage of vessels not targeting finfish. Better observer coverage of, and more consistent discarding behaviour within, the TR1 fleet resulted in more-reliable estimates from that fleet (which took the bulk of the cod landings). In 2008, the TR1 discard rate was consistent over the first two quarters, then rose, possibly because of quota restrictions towards year end; this pattern continued in 2009. However, the point estimates for 2009 were lower than any from 2008. In Figure 7, trajectories of North Sea cod landings by Scottish vessels in 2008 and 2009 (solid black lines) are compared with a Scottish “landings quota”, i.e. the sum of allocations to Scottish Producer Organizations (POs). The latter rises during each year because the POs benefit from quota exchanges between countries as each season progresses. Applying discard rates from Table 3 to their respective fleet landings, the resulting cumulative catch (upper boundary of the hatched area) can be contrasted with a hypothetical cumulative catch (upper boundary of pale grey area) based on the 2008 and 2009 discard rates calculated for the international fleet by the ICES assessment working group (ICES, 2009) and a Scottish “catch quota” derived using the same ICES discard rates (44% in 2008, 37% in 2009). In 2008, the empirical discard rate for the Scottish fleet was greater than the estimated international rate. Consequently, the total catch is estimated to have considerably exceeded the 2008 Scottish catch quota although landings were consistent with the landings quota (Figure 7a). In 2009, the empirical discard rate was lower than the international one until the third quarter; although by year end, the estimated cod catch was marginally higher than the Scottish catch quota (Figure 7b). A final comparison is between the realized Scottish catch and a Scottish quota share predicted by ICES to match the EU codmanagement plans (Figure 7, dot –dashed line). These plans called for year-on-year F reductions of 10% and 25% in 2008 and 2009, respectively (ICES, 2008, 2009). The total catch in 2008 did approximately match the required F reduction, although the total weight of cod discarded was greater than that landed. The cod catch in 2009 was well below that consistent with a 25% reduction in mean F compared with 2008.
Table 3. Estimates of cod discards as a percentage of catch from observer trips on Scottish vessels in the North Sea. 2008 2009 Gear type Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 TR1 53.8 (22.2 –73.4) 53.8 (41.1–58.6) 65.5 (47.2–76.6) 80.1 (57.8 –94.0) 25.5 (6.4–49.6) 12.1 (5.3 –22.6) 39.6 (25.4 –62.4) 50.0 (46.5–61.7) TR2 100.0 (100 –100) 36.8 (18.6–100) 64.0 (26.1–100) 72.0 (44.4 –100) 36.0 (19.3–74.8) 70.0 (32.5–91.9) 81.6 (73.7 –93.7) 91.1 (78.6–97.8) TR1, bottom trawls and seines of mesh ≥100 mm; TR2, bottom trawls and seines of mesh ≥70 and ,100 mm. Numbers in parenthesis give 95% confidence intervals after bootstrapping (1000 repetitions).
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Figure 7. Cumulative Scottish landings and discards of North Sea cod in (a) 2008 and (b) 2009. Discard estimates are raised from Scottish observer data for all sizes of fish. Solid black line, cumulative landings, the top of the hatched area representing the cumulative catch (using raised discard estimates); overlaid grey area, cumulative catch assuming annual international discard rates estimated by ICES (2009). Broken lines represent annual limits for (moving from lowest to highest): landings quota, landings assigned to Scottish POs, i.e. the quota share of international TAC (dashed); catch quota, landings quota plus discards calculated by applying the annual discard rate for the international fleet (ICES, 2009; dotted); F ¼ 0.9 × F07 quota and F ¼ 0.75 × F08 quota, Scottish quota share of the cod removals in 2008 and 2009, respectively, predicted by ICES to deliver a 10 and 25% reduction in F compared with the previous year (dot– dashed line). The value of all three quotas can change during the year as a consequence of landings quota exchanges between countries.
Discussion The SCC scheme is ambitious, particularly the RTC element. The pattern of closure instigation and reopening depends on at-sea inspections as well as each round of VMS analysis. It is therefore more dynamic than if 12 closures had been set in place every 21 d. Speedy and reliable dissemination of information to fishers is crucial for compliance. The analysis presented here shows evidence that, among UK vessels landing into Scotland at least, RTCs are being avoided. Although a low percentage of RTCs had zero fishing pings, some recorded only one or two over the 21-d closure. A better summary of compliance would be to consider the number of areas where fishing activity dropped during a closure period, and the extent of the decrease in activity. A review by STECF considered that “the level of implementation of the scheme has been quite high” (STECF, 2010). Of the seasonal closures, only the Coral Edge implementation resulted in significantly reduced activity, but it can be argued that if the timing and duration of these closures were chosen correctly, concentrations of cod (and the desire to fish them) should not be present before or after the closures. Aspects of the SCC scheme, e.g. the duration of RTC closures, RTC zones, and use of CIZs, were decided as a compromise between what was considered most effective for conservation
and what was most equitable for the fleet components within Scotland. Also, initially, the knowledge needed to inform the design of the scheme was limited. Amber areas have now been dropped from the SCC scheme. Analysis of fishery data showed mixed results in terms of the suitability of their locations, but the likely impact on cod mortality was minor. This was because of the very limited voluntary participation by eligible vessels. Further, the fishing patterns of participating vessels did not change significantly, suggesting that their previous activities had little impact on cod, so the amber area avoidance was ineffective. Feedback to the CCSG suggested that fishers catching significant quantities of cod regarded the days-at-sea incentives as insufficient. There was a gap between what managers could offer as incentives and what fishers considered as necessary to outweigh the loss of operational flexibility and catch opportunities that participation might involve. As the SCC scheme continues, such socio-economic issues are becoming better understood. The analysis of catch savings provides some evidence of cod avoidance. However, the estimated catch savings from RTCs were less than predicted. Going forwards, further reductions in fishing mortality were sought for 2010. Analysis of cod-tagging data has provided estimates of the proportion of cod expected to
Reducing cod mortality remain within a given distance of a starting point after a given time (P. Wright, pers. comm.). Combining this knowledge with the new target for cod-catch reduction in 2010, and a desire to maintain the 21-d closure duration, led to the RTCs being increased fourfold in size (to 15 × 15 nautical miles) for the NE and SE zones. The target for the 2010 management year was set at 107 closures. The nature of some management measures being considered, e.g. excluding vessels from an area at short notice, made it difficult to assess their effect. The catch savings calculation could not estimate any catch changes resulting from fishers revising plans for new trips because of closures known to be in place. The dynamic nature of fish stocks and the fleets that exploit them may mean that it is impossible to be sure how the vessel behaviour, landings, and discards would have been different had any given closed area not been implemented. The results presented here are, however, useful information for fishery managers and the CCSG. This in turn helped facilitate a key aspect of the SCC, namely regular review and adjustment of measures as necessary. Changes in addition to the larger RTCs introduced for 2010 included having only three RTC zones, by combining the two western zones, in response to the consistently very low lpue values recorded from the SW zone. There is now a requirement for at least one closure at all times west of Scotland and no minimum number of closures in the NE and SE zones, and the number of high-lpue squares used to define new RTCs within each zone has been increased from 25 to 50 in each zone. New metrics for the effectiveness of management measures are also evolving. An example is work comparing the activity of individual vessels (using VMS data) with a map of cod densities derived from landings-independent data. Movements of individual vessels to areas of lesser (or greater) relative abundance of cod are aggregated to form a histogram, the mean of which indicates the overall movement in terms of its significance for cod (Needle and Catarino, 2011). The efficacy of the method for locating closures depends on the accuracy of logbook records and the reliability and interpretation of VMS data. To prevent a highly smoothed and potentially uninformative lpue history resulting from whole-trip landings being assigned evenly across all VMS fishing pings, the lpue values are assigned to pings for each day within a voyage. For trips covering large distances, it must be emphasized that logbook records give the correct day when landed cod were caught. Errors may lead to closures being sited where cod abundance is low, while areas producing the greatest lpue are overlooked. In future, this aspect of data reliability could be tested through cross-checks between logbook information, observer records, and VMS data. We determined fishing pings using a simple vessel-speed criterion. Subsequent research based on CCTV systems that record vessel speed, heading, and fishing activity has confirmed that our fishing-speed range is appropriate (N. Campbell, pers. obs.). Linking VMS data to observer logbooks in the Irish trawl fishery showed that most fishing and non-fishing activities were correctly identified using a fishing-speed range of 0.5 to 4 knots; attempts to apply more complex algorithms did not lead to any significant improvement (Gerritsen and Lordan, 2011). Bastardie et al. (2010) showed that such improvements would be more likely if ping frequency were to be increased. Some 3 and 14% of VMS ping intervals were rounded down and rounded up, respectively. Work is ongoing on how best to deal with short ping intervals. During 2009, it was noticed that in some deep-water rectangles, the very low fishing effort
1687 coupled with modest cod landings could result in very high values of lpue. Consequently, it was decided to restrict potential RTCs to the region within the 400-m depth contour. The VMS methodology is currently restricted to vessels ≥15 m long. Cod landings by smaller vessels constituted ,1% of the Scottish total. Also, VMS is to be extended to vessels ≥12 m from the beginning of 2012. However, on-board sampling as an additional means of identifying closures is still regarded as important, and it measures catch rates directly. The final outcome sought from the SCC scheme is an annual catch that achieves the mortality reductions required by the cod long-term management plan. Using quarterly summaries of discard rates obtained from observer programmes, we can provide estimated catch trajectories relative to annual targets throughout the year. This allows midyear adjustment of the scheme if necessary. Observers only cover a small proportion of the fleet, and aggregating results over quarters rather than annually increases the risk of bias in the estimates. The catch trajectories for the North Sea are considered robust, however, and indicate that the mortality-reduction objective was achieved by the Scottish fleet in 2009. The picture is not so clearcut west of Scotland. The raising method has used cod landings as the auxiliary variable, leading to problems because the observed cod-discard rate in the TR2 fleet has been 100% in quarters for which non-observed TR2 vessels have landed cod from the west of Scotland. MSS is currently investigating whether there is a better means of raising discards that is both robust and sufficiently precise for end-uses such as annual stock assessment, DCF reporting, and general fisherymanagement purposes. We attempted to infer a partial F for North Sea cod taken by the Scottish fleet in 2009 (STECF, 2010). However, this was unsuccessful for two reasons: first, there were incomplete data on landings and/or discards from other nations; second, in the assessment of North Sea cod, if trends in stock biomass and mean F over reference age groups differed between including and excluding commercial data, the mean F was calculated using survey data only. Therefore, partial F values could only be calculated from fishery-independent data and assuming discard rates for other nations based on Scottish data. Progress in this area requires more complete sharing of fishery-dependent information across nations. In September 2009, the EU and Norway implemented a similar RTC scheme in the North Sea and Skagerrak, with the aim of protecting juvenile cod, haddock, saithe, and whiting. Fish below the minimum landing size (MLS), which is lower in the Skagerrak than in the North Sea for all these species, are regarded as juveniles. Closures are decided by the percentage by weight of the juvenile catch. As no fish smaller than the MLS should be landed, lpue analysis using VMS and landings data is not appropriate for any species. Therefore the EU–Norway scheme relies entirely on inspections at sea, unlike the Scottish SCC. With a large RTC element and extensive use of fishery data, the SCC is a pioneering scheme within the EU, and it has required many practical issues to be resolved to allow it to operate smoothly. Fresh thinking has also been required for the analysis of data to provide measures describing how well the scheme is working. As experience is gained, there will be adjustments to the way it is configured, but the measures so far identified to indicate the performance of the scheme in delivering reductions in cod discards and the associated mortality are encouraging.
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Acknowledgements We thank Ian Hepburn and Greig Chalmers from Marine Scotland Compliance for providing information used in this paper, and two anonymous referees whose comments and corrections greatly improved the manuscript.
References Bastardie, F., Nielsen, J. R., Ulrich, C., Egekvist, J., and Degel, H. 2010. Detailed mapping of fishing effort and landings by coupling fishing logbooks with satellite-recorded vessel geo-location. Fisheries Research, 106: 41– 53. CEC. 2008. Council Regulation (EC) 1342/2008 on establishing a long-term plan for cod stocks and the fisheries exploiting those stocks and repealing Regulation (EC) No 423/2004. Official Journal of the European Union, L 348: 20– 33. CEC. 2009. Council Regulation (EC) 43/2009 on fixing for 2009 the fishing opportunities and associated conditions for certain fish stocks and groups of fish stocks, applicable in Community waters
S. J. Holmes et al. and, for Community vessels, in waters where catch limitations are required. Official Journal of the European Union, L 22: 1 – 205. Gerritsen, H., and Lordan, C. 2011. Integrating vessel monitoring systems (VMS) data with daily catch data from logbooks to explore the spatial distribution of catch and effort at high resolution. ICES Journal of Marine Science, 68: 245– 252. ICES. 2008. Report of the Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak—Spring and Autumn (WGNSSK). ICES Document CM 2008/ACOM: 09. 921 pp. ICES. 2009. Report of the Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK). ICES Document CM 2009/ACOM: 10. 993 pp. Needle, C., and Catarino, R, 2011. Evaluating the effect of realtime closures on cod targeting. ICES Journal of Marine Science, 68: 1647– 1655. STECF. 2010. 34th Plenary Meeting Report of the Scientific, Technical and Economic Committee for Fisheries (PLEN-10-02), 12 – 16 July 2010, Copenhagen. JRC 59822, EUR 24527 EN. Publications Office of the EU, Luxembourg. 162 pp.
