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Scale- and Context-Dependent Selection of Recreational Harvest Estimation Methods: The Australasian Experience a
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Bruce W. Hartill , Martin Cryer , Jeremy M. Lyle , Eugene B. Rees , Karina L. Ryan , e
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Aldo S. Steffe , Stephen M. Taylor , Laurie West & Brent S. Wise
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National Institute of Water and Atmospheric Research, Private Bag 99940, Auckland, 1149, New Zealand b
New Zealand Ministry of Fisheries, Post Office Box 1020, Wellington, 6140, New Zealand
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Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, Tasmania, 7000, Australia d
Fisheries and Marine Research Laboratories, Department of Fisheries Western Australia, Post Office Box 20, North Beach, Western Australia, 6920, Australia e
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To cite this article: Bruce W. Hartill, Martin Cryer, Jeremy M. Lyle, Eugene B. Rees, Karina L. Ryan, Aldo S. Steffe, Stephen M. Taylor, Laurie West & Brent S. Wise (2012): Scale- and Context-Dependent Selection of Recreational Harvest Estimation Methods: The Australasian Experience, North American Journal of Fisheries Management, 32:1, 109-123 To link to this article: http://dx.doi.org/10.1080/02755947.2012.661387
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North American Journal of Fisheries Management 32:109–123, 2012 C American Fisheries Society 2012 ISSN: 0275-5947 print / 1548-8675 online DOI: 10.1080/02755947.2012.661387
ARTICLE
Scale- and Context-Dependent Selection of Recreational Harvest Estimation Methods: The Australasian Experience Bruce W. Hartill* National Institute of Water and Atmospheric Research, Private Bag 99940, Auckland 1149, New Zealand
Martin Cryer New Zealand Ministry of Fisheries, Post Office Box 1020, Wellington 6140, New Zealand
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Jeremy M. Lyle Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, Tasmania 7000, Australia
Eugene B. Rees New Zealand Ministry of Fisheries, Post Office Box 1020, Wellington 6140, New Zealand
Karina L. Ryan Fisheries and Marine Research Laboratories, Department of Fisheries, Western Australia, Post Office Box 20, North Beach, Western Australia 6920, Australia
Aldo S. Steffe Department of Industry and Investment, New South Wales, Cronulla Fisheries Research Centre, 202 Nicholson Parade, Cronulla, New South Wales 2230, Australia
Stephen M. Taylor Department of Employment, Economic Development and Innovation, Level 2, 80 Ann Street, Brisbane, Queensland 4001, Australia
Laurie West Kewagama Research, 1/11 Russell Street, Noosaville, Queensland 4566, Australia
Brent S.Wise Fisheries and Marine Research Laboratories, Department of Fisheries, Western Australia, Post Office Box 20, North Beach, Western Australia 6920, Australia
Abstract Fisheries managers are becoming increasingly aware of the need to quantify all forms of harvest, including that by recreational fishers. This need has been driven by both a growing recognition of the potential impact that noncommercial fishers can have on exploited resources and the requirement to allocate catch limits between different sectors of the wider fishing community in many jurisdictions. Marine recreational fishers are rarely required to report any of their activity, and some form of survey technique is usually required to estimate levels of recreational catch and effort. In this review, we describe and discuss studies that have attempted to estimate the nature and extent of recreational harvests of marine fishes in New Zealand and Australia over the past 20 years. We compare studies
*Corresponding author:
[email protected] Received February 8, 2011; accepted October 13, 2011
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by method to show how circumstances dictate their application and to highlight recent developments that other researchers may find of use. Although there has been some convergence of approach, we suggest that context is an important consideration, and many of the techniques discussed here have been adapted to suit local conditions and to address recognized sources of bias. Much of this experience, along with novel improvements to existing approaches, have been reported only in “gray” literature because of an emphasis on providing estimates for immediate management purposes. This paper brings much of that work together for the first time, and we discuss how others might benefit from our experience.
Fisheries managers in developed nations are becoming increasingly aware of the need to accurately quantify marine recreational harvests, as inshore fish stocks come under increasing and widespread pressure from both commercial and noncommercial sectors of the fishing community, and as stakeholders become more organized, adversarial, and vociferous (Coleman et al. 2004; Ihde et al. 2011). This interest has lead to a growing scrutiny of both recreational harvest estimates and the means by which they are obtained. The resulting ongoing development of survey methods that has resulted from this scrutiny has benefited greatly from local and international experience. Over the past 30 years, researchers in Australasia (Australia and New Zealand; Figure 1) have employed a wide range of methods to estimate recreational harvests. In some cases Australasian researchers have closely followed methods developed elsewhere (such as in the United States of America and Canada), but the iterative and ongoing pursuit of more cost-effective, precise, and unbiased harvest estimation methods has resulted in innovations that may benefit others elsewhere. The process of developing and adapting survey methods has been strongly influenced by local circumstances that vary between, and within, Australia and New Zealand. Recreational fishing occurs along almost all of Australia’s 35,877-km-long coastline, but the intensity and nature of this effort varies considerably. Over 70% of Australia’s population lives on the southeast coast of this continental land mass, centred on the large cities of Adelaide, Melbourne, Sydney, and Brisbane. Most fishing effort occurs in nearby coastal waters. Substantial localized recreational fisheries are also found in other parts of Australia, such as around Tasmania and close to the city of Perth in Western Australia. Vast stretches of the northern, western, and southern coast are very sparsely populated, however, and the low intensity of fishing effort that does take place in these areas is undertaken by a mix of local residents, highly avid anglers who are prepared to travel to less-frequented fishing sites, and retired transient visitors from other states (Henry and Lyle 2003). Most of Australia’s recreational fisheries are managed independently at the state or territory (hereafter, “state”) level, although most fisheries occurring between 3 and 200 nautical miles offshore fall under federal jurisdiction. This means that most recreational surveys have been undertaken by agencies from a single state, yet many fish stocks inhabit the waters of more than one state. Only a small number of recreational
fisheries are subject to any form of angler licensing, but the incidence of this form of management regime is increasing. The range of fisheries and diversity of catch observed within a state can vary considerably, as Australia’s coastline passes through tropical, subtropical, and temperate waters (latitudes range from 10◦ S to 44◦ S). The annual recreational harvest of all marine finfish species was estimated in 2000–2001 to be ∼27,000 metric tons (Henry and Lyle 2003). The situation in New Zealand is less complex. All of New Zealand’s fisheries are managed by a single agency (Ministry of Fisheries), and fisheries assessments generally consider whole fish stocks, regardless of their spatial extent. New Zealand’s 13,020-km coastline falls between the temperate latitudes of 34◦ S and 47◦ S, and although recreationally fished stocks tend to be more productive than in Australia, fewer species are caught by recreational fishers. Most of the recreational harvest is taken off the northeast coast of the North Island, but substantial catches are landed from the exposed west coast of the North Island and on the north and east coasts of the South Island. The annual recreational harvest of all marine finfish species in New Zealand is thought to be ∼8,000 metric tons. Although local circumstances have influenced method choice, in most cases the spatial extent of a fishery has largely determined the methods that can be used to assess it. Small-scale fisheries are best assessed using on-site observational methods, whereas interviewer-assisted, self-reported off-site methods usually offer the most viable means of estimating harvests at the state or national scale (Pollock et al. 1994). Many of these methods have been employed by more than one agency, to varying degrees of success. In some cases, lessons learned from one survey have influenced the design of others, but there have been instances where opportunities to learn from experience elsewhere have been missed because of limited exchanges of researcher experience. This review attempts to share the experiences of Australasian researchers with those elsewhere who face the challenging task of estimating recreational harvests from a diversity of fisheries at a range of spatial and temporal scales. In the following sections, we describe how various survey methods have been used to measure the harvest taken by recreational fishers in New Zealand and Australia. Most of these methods were described in some detail by Pollock et al. (1994), and we urge interested readers to consult this excellent reference as well as the source literature when considering survey options. This review is the direct result of a series of workshops
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FIGURE 1.
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Australian states and territories, and New Zealand.
on assessing recreational fisheries held in Sydney, Brisbane, and Perth, Australia, and in Wellington, New Zealand. OFF-SITE SURVEY METHODS Overview.—Most large-scale surveys of recreational fisheries conducted in Australia and New Zealand have been based on some form of off-site approach (Table 1). The survey designs employed have varied considerably, but all have combined an estimate of the number of fishers participating in a fishery with some form of diary-based estimate of the average annual catch per fisher. Most studies have also included a concurrent creel survey component to provide estimates of the mean weight of commonly caught species and other ancillary information. These mean weight estimates have been used convert estimates of numbers of fish caught by recreation fishers into total harvest weight estimates, which can be directly compared with commercial catch statistics that usually are given in terms of tonnage. The choice of method used to estimate the number of fishers in a population has largely been determined by the nature of available sample frames. Estimates of fishing population size
have been based on either general population surveys using telephone directory listings (Teirney et al. 1997; Bradford 1998; Coleman 1998; Henry and Lyle 2003; McInnes 2008; Jones 2009; R. O. Boyd and J. L. Reilly, Kingett Mitchell and Associates, Ltd., unpublished data), face-to-face surveys of dwelling residents (R. O. Boyd, L. Gowing, and J. L. Reilly, Kingett Mitchell and Associates, Ltd., unpublished data), telephone surveys of recreational fishing license holders (Lyle 1999; McGlennon 1999; Venema et al. 2003; Lyle et al. 2005; Currie et al. 2006; Caputi et al. 2008), or mail surveys (Melville-Smith and Anderton 2000). Most of these surveys also have been used to recruit fishers into diarist programs from which detailed catchand-effort information is obtained. Telephone diary surveys of the general population.—The earliest telephone diary surveys of recreational fishers in Australasia were conducted in New Zealand. Although the telephone diary approach used in New Zealand to date is no longer considered reliable, the experience gained from these surveys is still informative. The method used in New Zealand employed a two-phase design. The first phase was a telephone survey of households with listed phone numbers, which was used to estimate the
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TABLE 1. Telephone diary and license diary surveys conducted in Australia and New Zealand (NZ) to date.
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Year
Country or state
Estimate of fisher population size
Diarist Diarist data recruitment collection
Reference
Annually since 1986–1987 Western Australia
License (lobster)
Mail
Mail
1991–1994
NZ regions
Telephone
Diary
1995
Northern territories
Telephone
Telephone
Coleman (1998)
1996
NZ national
Telephone
Diary
Bradford (1998)
1996–1998 1996, 1998, 2001, 2004
Tasmania Queensland
Telephone Telephone
Telephone Diary
Lyle (1999) McInnes (2008)
1998–1999, 2001–2002, 2004–2005
South Australia
Telephone (individual) Telephone (household) Telephone (individual) License (various) Telephone (individual) License (lobster)
Melville-Smith and Anderton (2000) Teirney et al. (1997)
Telephone
Telephone
1999–2000
NZ national
Telephone
Diary
2000–2001
NZ national
Telephone
Diary
McGlennon (1999); Venema et al. (2003); Currie et al. (2006) Boyd and Reilly (unpublished) Boyd et al. (unpublished)
2000–2001
Australian, all states
Telephone
Telephone
Henry and Lyle (2003)
2000–2001, 2001–2002, annually since 2004–2005 Biennially since 2000–2001 2007–2008
Western Australia
Telephone
Telephone
Caputi et al. (2008)
Telephone
Telephone
Lyle et al. (2005)
Telephone
Telephone
Jones (2009)
Tasmania Tasmania and South Australia
Telephone (individual) Face-to-face (individual) Telephone (household) License (lobster)
License (lobster and abalone) Telephone (household)
fishing participation rate in the general population. Extensive use was made of national census data and demographic information collected during telephone interviews in an attempt to correct for nonrepresentative sampling and nonresponse bias. Diarists were also recruited during the telephone survey for a second phase. These diarists were asked to complete and return fishing diaries over the following 12 months. Diarists who failed to return their logbooks at the end of each quarter were contacted and reminded to submit their diaries, but any recording of information on fishing activity over the previous 3 months was entirely selfmanaged by the diarists. Estimates of average diarist catch were scaled up by the estimated number of fishers in the population to obtain estimates of total catch by fish stock. Comparison of length frequency data provided by diarists with measurements made during boat ramp interviews in 1992– 1993 suggested that diarists tended to overestimate the average size of the fish they caught (M. P. Ryan and A. R. Kilner, Ministry of Agriculture and Forest Fisheries New Zealand, unpublished data). Creel surveys have since been used to provide mean weight estimates by fish stock.
A direct comparison was made between estimates provided by a regional telephone diary survey and a concurrent aerialaccess survey of the fishery for western Hauraki Gulf snapper Pagrus auratus over a 17-week period in 1994 (T. Sylvester, New Zealand Ministry of Fisheries, unpublished data). The broad similarity of the estimates obtained from these two independent surveys led to continued support for the use of the telephone diary method in New Zealand. The first national telephone diary survey of recreational fisheries was undertaken in 1996 (Bradford 1998) using the methods employed in earlier regional surveys (Teirney et al. 1997). Pilot survey testing in preparation for a second national survey in 2000, however, led to a closer examination of the methods used to estimate the number of recreational fishers. Seemingly minor changes to questionnaire formats in pilot surveys led to large shifts in estimates of participation in the fishery (J. L. Reilly, Statistical Insights, Ltd., unpublished data). Comparative trials suggested a previously unconsidered soft refusal bias. Soft refusal bias leads to an underestimation of the participation rate and a nonrepresentative sample of diarists, when a fisher
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politely but intentionally deceives the interviewer by indicating that they do not fish to avoid a protracted interview. Concerns about soft refusal and the incomplete coverage of the telephone directory (“White Pages”) sample frame led to the decision to use face-to-face survey techniques to determine the prevalence of putative fishers in the general population (Boyd et al., unpublished; Boyd and Reilly, unpublished). A monthly sampling regime was used to monitor changes in fisher participation throughout the year. The results of these interviews suggested that members of the public were less likely to have claimed to have fished in the previous 12 months if they were interviewed during the winter (Reilly, unpublished). Although the methods used in the 1999–2000 face-to-face prevalence survey were thought to be more reliable than those used in previous telephone-based surveys, the estimated number of fishers in New Zealand and associated harvest estimates were three times higher than previously estimated. These estimates are thought to be implausibly high, and they have not been accepted by fisheries managers. Comparisons of catches reported by diarists and more direct observations made during concurrent creel surveys further reduced confidence in the telephone diary approach used in New Zealand. Diarists in both 1996 and 2000 reported a far lower incidence of unsuccessful trips than that directly observed in creel surveys. Many diarists also reported catches that were multiples of the daily legal bag limit, suggesting that they often reported the catch of co-fishers despite being requested not to do so. Diarists may have intentionally misreported their catch for prestige, or unintentionally exaggerated their catch when recalling and recording their activity at the end of each fishing quarter. A more-rigorous telephone diary approach has been developed in Australia, where off-site survey methods offer the only viable means of estimating harvest taken over vast spatial scales. The telephone diary approach used in Australia has been applied in a national and several statewide surveys (Coleman 1998; Henry and Lyle 2003; Jones 2009; Lyle et al. 2009). The main distinction between the New Zealand and Australian approaches lies in the management of the diary phase. A brief description of this approach is discussed below (for more details see Lyle et al. 2002). A screening survey is initially conducted by telephone to profile and estimate the number of fishers who intend to fish in the coming year, and to recruit diarist households. The primary sampling unit in these surveys is the household rather than the individual fisher. Household cluster sampling is considered to be advantageous, as it inherently addresses the nonindependent likelihood of two or more fishers living in the same household, while allowing for the potentially cost-effective collection of data from more than one fisher from a given interview. Not all households are listed in the White Pages (an estimated 19% of dwellings were unlisted in 2001), but the demographics of households contactable through the White Pages closely matched those of national, census-based profiles of the general population in 2001 (Henry and Lyle 2003). Catch rates of
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listed and unlisted dwellings were compared in South Australia in 2008 and in Queensland in 2010 (McInnes 2008), and were found to be broadly similar. The response rates achieved in these initial screening surveys have routinely exceeded 80%, which is double the rate achieved in the New Zealand surveys (Table 2), reducing uncertainty surrounding nonrespondents. High response rates have been attributed to: the skill and persistence of the interviewers, the brevity of the questionnaires (especially for nonfishing households), and the fact that surveys were conducted by government agencies rather than by commercial market research companies. Members of some households will always refuse to cooperate or remain unavailable despite repeated attempts to make contact. Nonresponse adjustments are made to participation rate estimates based on nonresponse follow-up calls, by using information derived from partial responders (i.e., respondents who at least answered the question about previous fishing activity), or both. Adjustments for unexpected fishing activity by households that, at screening, indicated no intention to go fishing are also made by recontacting a random sample of “nonintending” households and establishing whether or not they fished during the diary period. The diary phase differs from conventional angler diary surveys in two important ways: the diary is used more as a “memory jogger” rather than as a formal logbook, and responsibility for data collection rests with survey interviewers and not with the diarists. Data collection is undertaken by brief telephone interviews during which trained interviewers recorded details of any fishing that has occurred since the last contact. The level of fishing activity determines the contact frequency, but as a general rule, respondents are called at least once a month even if no fishing is planned. The use of survey interviewers in this way has several advantages over other long-term, self-reporting regimes, such as the quarterly diary approach used in New Zealand. First, the frequent collection of data and the use of the memory jogger diary reduces the potential for recall bias, which is a significant issue that should be considered with any form of self-reporting survey. Second, the responsibility of recording the data are passed to the interviewer, thereby reducing the burden on the respondent and leading to higher levels of survey completion and more comprehensive levels of reporting. Third, the interview-based process allows the interviewer to progressively query and clarify atypical information and inconsistencies, such as the tendency for fishers to report their co-fishers catch or to not report zero-catch trips. Interviewers are aware of and try to actively discourage prestige reporting by reassuring the diarist that low or nil catches are common. Researchers in Tasmania have recently developed an analytical package in R (R Development Core Team 2008) that can be used to generate harvest estimates and associated estimates of variance from data collected through surveys following the Australian telephone diary approach (Lyle et al. 2010). This module
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TABLE 2. Screening and diary response for Australian surveys based on the telephone diary methodology. Asterisks indicate 2000–2001 National Fishing Survey.
Screening survey
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State
Diary survey
Survey timing
Net sample
Response (%)
Northern Territory Northern Territory Tasmania Tasmania South Australia South Australia Victoria New South Wales Western Australia Queensland
1994–1996 2000–2001* 2000–2001* 2007–2008 2000–2001* 2007–2008 2000–2001* 2000–2001* 2000–2001* 2000–2001*
3,776 1,640 3,392 4,065 4,422 6,232 7,957 7,797 4,407 6,665
General population survey 86 90 82 94 81 83 85 87 86 90 90 93 76 89 81 92 83 89 78 89
98 85 97 96 93 96 91 91 95 94
Coleman (1998) Henry and Lyle (2003) Henry and Lyle (2003) Lyle et al. (2009) Henry and Lyle (2003) Jones (2009) Henry and Lyle (2003) Henry and Lyle (2003) Henry and Lyle (2003) Henry and Lyle (2003)
Tasmania Tasmania Tasmania Tasmania Tasmania South Australia South Australia South Australia
1996–1998 2000–2001 2002–2003 2004–2005 2006–2007 1998–1999 2001–2002 2004–2005
1,865 526 735 711 694 330 2,000 2,077
Licensed fishing activities 96 97 92 96 90 92 94 94 86 94 89 98 87 99 71 81
96 98 97 94 93 97 96 98
Lyle (2000) Forward and Lyle (2002) Lyle and Morton (2004) Lyle and Morton (2006) Lyle (2008) McGlennon (1999) Venema et al. (2003) Currie et al. (2006)
can also be used to analyze telephone diary data collected from surveys based on a license database sample frame, as discussed in the following section. Telephone diary surveys of licensed fisheries.—The second most commonly used sample frame employed in off-site surveys has been some form of license database. License databases readily provide estimates of the number of fishers involved in a fishery at any point or period in time, providing there is a high level of compliance, a low level of exemption, and timely entry of data for licenses issued. The use of a license-based sample frame also means that all of those contacted will either hold or have held a license, greatly increasing the efficiency of any sampling regime at the initial screening stage. This form of off-site survey approach has been used routinely to assess the harvest from a small number of licensed fisheries in Australia. Mail surveys have been used to survey rock lobster (southern rock lobster Jasus edwardsii, western rock lobster Panulirus cygnus, ornate rock lobster P. ornatus, painted rock lobster P. versicolor, and two-spined rock lobster P. penicillatus) license holders annually in Western Australia since the 1986– 1987 rock lobster season (Melville-Smith and Anderton 2000). Initially, questionnaire forms were dispatched with license renewal forms, but no incentive was offered to encourage returns. The return rates achieved were only 30–35%, but the introduction of prize draws lifted this rate to around 60% in subsequent surveys. Licensed recreational fishers in Western Australia were
Uptake (%)
Completion (%)
Source
also recruited and interviewed by telephone in 2000–2001 and 2001–2002, and annually since 2004–2005 (Caputi et al. 2008). Annual daily catch rate estimates obtained from telephone diary surveys were generally higher than reported by mail, but the harvest tonnages estimated from the mail surveys were about twice those obtained from the concurrent telephone diary surveys. The mail survey harvest estimates are thought to be overestimates because of recall bias (despite there being several mail outs over the 7.5-month season) and nonresponse bias (the 40–60% of fishers who responded are thought to be generally more avid and hence potentially more successful than nonrespondents). The methods currently used in the Western Australian telephone diary surveys of recreational fishers were based on an approach developed in 1996–1997 and 1997–1998 to estimate the harvest taken from the licensed Tasmanian southern rock lobster, abalone (blacklip abalone Haliotis rubra and greenlip abalone H. laevigata), and set net fisheries (Lyle 1999). A random sample of licensees from the previous year are contacted and asked if they intend to go fishing in the coming 12 months. “Intending” fishers are asked to keep fishing diaries for the next 12 months. The sole purpose of these diaries is to act as a memory jogger rather than as a formal means of recording data on their fishing activity. Diarists were interviewed regularly by phone over the following 12 months, the contact frequency for each fisher being tailored to their fishing avidity. In 1997–1998, a second independent, random sample of licensees were asked
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at the end of a 6-month period to recall their fishing activity over that period, and their results were compared with those reported by diarists (Lyle 1999). Differences between these two data sets were attributed to recall bias, as nonresponse rates were negligible. This comparison demonstrates the extent to which memory jogger diaries and frequent contact can reduce recall bias in studies of this nature. These methods have been used biennially since 2000–2001 to estimate harvests from the Tasmanian southern rock lobster and abalone fisheries (Lyle et al. 2005) and to estimate southern rock lobster harvests in South Australia in 1998–1999 (McGlennon 1999), 2001–2002 (Venema et al. 2003), and 2004–2005 (Currie et al. 2006). The advantages of basing a telephone diary survey on a license database were evaluated during a survey of recreational fishing license holders in the state of Victoria in 2006–2007 (Ryan et al. 2009). The use of a specific list of anglers as a sampling frame reduced the costs of the initial screening survey, contributed toward high response rates (reducing nonresponse bias), and guided the development of an optimal survey design. A stratum of avid fishers was oversampled, effectively increasing the number of fishing events in the sample and improving precision; harvest estimates at regional scales in this survey were consistently more precise than those obtained in the statewide National Recreational Fishing Survey in 2001. The Victorian license has several exemption categories, and bias from exempt fishers was investigated with a concurrent boat ramp survey. The magnitude of snapper harvest by exempt anglers was estimated to be about 13% of that taken by licensed fishers, similar to the standard error of the harvest estimate for licensed fishers. Charter boat logbook programs.—Charter boat operations often account for a disproportionate share of the recreational harvest of some species because of the intensity of the fishing that can take place and the specialist, guided nature of this activity. Although probabilistic survey methods can be used to assess levels of harvesting from charter boats, all Australian states (except Victoria) have introduced either mandatory or voluntary reporting systems for charter boats. New Zealand has recently introduced a mandatory logbook regime (MFish 2010). The success of any logbook reporting regime depends on its coverage, design, implementation, and ongoing management. Although the coverage of a mandatory reporting regime is usually assumed to be complete, this assumption is valid only if a complete and up-to-date list of charter vessel operators is available, such as that potentially provided by a license holder database or registry. The viability of the charter boat reporting system in several Australian states has been undermined by poor implementation and lack of maintenance. A mandatory charter boat logbook system was implemented and is coordinated by fisheries managers in New South Wales. Since its inception in 2000, there has been no study to validate the data provided by charter boat operators. An examination of their logbook data shows a high level of noncompliance by many operators to provide any information and that the data provided by many compliant operators contains
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many biases. Consequently, these data are regarded by fisheries scientists to be inaccurate and nonrepresentative, and they are not used any of the stock assessments routinely undertaken for important finfish stocks.
ON-SITE SURVEY METHODS Overview.—Off-site methods are not usually cost-effective at smaller spatial scales because a large sample of diarists or license holders is usually required to adequately describe processes occurring at a high spatial resolution. On-site methods, however, provide greater resolution at smaller spatial scales, where they are most cost-effective. The relative merits of onsite and off-site methods become less clear as the scale and diversity of the assessed fishery broadens, given that relative accuracy and precision are also important considerations. Onsite surveys usually employ fishery-independent observers who collect data according to a structured design that can be used to facilitate the detection and quantification of sources of bias. Onsite methods used throughout Australasia are discussed below, in order of diminishing spatial scale (Table 3). Harvest estimates derived from tagging programs.—In New Zealand, many of the earliest recreational harvest estimates were derived incidentally (from tagging programs primarily undertaken to provide biomass estimates for New Zealand’s largest snapper fish stocks) between 1984 and 1991 (Baird and McKoy 1988; Kirk et al. 1988; G. G. Baird and J. L. McKoy, New Zealand Ministry of Agriculture and Fisheries, unpublished data; J. McKenzie, National Institute of Water and Atmospheric Research, unpublished data). Visible dart tags were used and highly publicized rewards were offered for their return. The relative rates of return from the recreational and commercial sectors (usually expressed as tags per metric ton of catch) were used to estimate the recreational harvest, given the reported weight of fish landed by commercial fishers. This method has faced criticism because it was assumed that tagged fish were equally available to both sectors and that all fishers were equally likely to return tags. The low number of tag recaptures meant that data quality was of paramount importance, yet very little attention was paid to data provided by recreational fishers, as the primary purpose of these programs was to collect returns from the commercial sector. There is good evidence to suggest, however, that commercial fishers often misrepresented themselves as recreational fishers when returning tags. It was widely known at the time that each tag returned from the commercial sector would reduce the estimate of current biomass for snapper, and some reasoned that this could lead to reductions in their future catch entitlements. A recent informal review of returns provided by “recreational” fishers in 1991 found that almost all cases of multiple returns from a single fisher (24% of all recreational returns) were probably attributable to commercial catches rather than those taken by recreational anglers. Aerial-access surveys.—Aerial-access methods offer the most viable on-site means of directly and cost effectively
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TABLE 3. On-site surveys conducted in Australia and New Zealand to date.
Method Tagging programs Aerial-access surveys Maximum count
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Random count
Bus route surveys
Roving surveys
Traditional access point surveys
Scope or coastline length (km) Fish stock Fish stock 2,000 + 2,000 + 500 + 500 + 300 + 100 + 100 + 100 + 1,000 + 1,000 + 900 + 100 +
