Article

A scientific alternative to moratoria for rebuilding depleted international tuna stocks

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  • CSIRO Oceans And Atmospheric Research
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Abstract

There is considerable international concern and scientific debate about the current state and future of tuna stocks worldwide and the capacity of Regional Fisheries Management Organisations to manage the associated fisheries effectively. In some cases, this concern has extended to predictions of imminent collapse with minimal chances of recovery, even under a commercial catch moratorium. As a viable alternative to a full fishery closure, the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) has adopted a scientifically tested, adaptive rebuilding strategy for the depleted southern bluefin tuna (Thunnus maccoyii) stock. The management procedure (MP) adopted involves a harvest control rule that fully specifies the total allowable catch as a function of key indicators of stock status, adjusting future harvest levels every three years so as to meet the rebuilding targets agreed by CCSBT. It was chosen from a subset of candidate MPs selected following extensive simulation testing. This involved first selecting a wide range of plausible scenarios for stock status and input data, ranging from pessimistic to optimistic, against which the alternative candidate MPs were tested to ensure that they were robust to important uncertainties. This is the first time that a comprehensively evaluated MP has been adopted for an internationally managed tuna stock. Both the process and the outcomes have broad applicability to other internationally managed stocks.

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... Continued research to address potential bias associated with analyzing CKMR data (e.g., due to spatial sampling limitations and the need for additional demographic information; Conn et al. 2020;Trenkel et al. 2022) should be a high priority, because there is an undeniable utility of CKMR data for supporting fisheries management (e.g. Hillary et al. 2016Hillary et al. , 2019. ...
... While many MSEs are used to develop and implement a management strategy for a specific fishery (e.g. Geromont et al. 1999;Plaganyi et al. 2007;Hillary et al. 2016) or to identify generic management strategies that are applicable to an array of fisheries (e.g., for data-limited fisheries; Geromont and Butterworth 2015;Fischer et al. 2020), 'desktop MSEs' can also be used to explore research questions (e.g., the value of information and the relative economic return under different classes of a management regime; McGarvey et al. 2015). Similarly, the development of short-cuts to MSE, which simplify aspects of the simulated system or management strategy (e.g., by replacing a full stock assessment with random error around the true population status), leads to a framework that differs from the standard definition of MSE (ICES 2020). ...
... Therefore, it is envisioned that MSE applications will help pioneer tangible steps towards implementation of EBFM and more thorough evaluation of the ability of management strategies to achieve socioeconomic objectives (Table 3). Moreover, there is likely to be an increasing trend towards simultaneous evaluation of empirical and modelbased (i.e., assessment-based) management strategies Hillary et al. 2016) as well as hybrid management strategies (e.g., that incorporate absolute abundance estimates from CKMR; Hillary et al. 2019;Trenkel et al. 2022), through MSE. As generic MSE software packages and associated digital tools continue to become more sophisticated, development of MSE applications will gain efficiency enabling increased usage worldwide. ...
Article
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Marine population modeling, which underpins the scientific advice to support fisheries interventions, is an active research field with recent advancements to address modern challenges (e.g., climate change) and enduring issues (e.g., data limitations). Based on discussions during the 'Land of Plenty' session at the 2021 World Fisheries Congress, we synthesize current challenges, recent advances, and interdisciplinary developments in biological fisheries models (i.e., data-limited, stock assessment, spatial, ecosystem, and climate), management strategy evaluation, and the scientific advice that bridges the science-policy interface. Our review demonstrates that proliferation of interdisciplinary research teams and enhanced data collection protocols have enabled increased integration of spatiotemporal, ecosystem, and socioeconomic dimensions in many fisheries models. However, not all management systems have the resources to implement model-based advice, while protocols for sharing confidential data are lacking and impeding research advances. We recommend that management and modeling frameworks continue to adopt participatory co-management approaches that emphasize wider inclusion of local knowledge and stakeholder input to fill knowledge gaps and promote information sharing. Moreover, fisheries management, by which we mean the end-to-end process of data collection, scientific analysis, and implementation of evidence-informed management actions, must integrate improved communication, engagement, and capacity building, while incorporating feedback loops at each stage. Increasing application of management strategy evaluation is viewed as a critical unifying component, which will bridge fisheries modeling disciplines, aid management decision-making, and better incorporate the array of stakeholders, thereby leading to a more proactive, pragmatic, transparent, and inclusive management framework-ensuring better informed decisions in an uncertain world. Supplementary information: The online version contains supplementary material available at 10.1007/s11160-022-09726-7.
... The precautionary approach is regarded as an integral part of sciencebased fisheries management [9,10]. If, on one side, the adaptive management (or feedback control) can rely on the preventive approach and the corrective approach when the uncertainty of scientific information useful for taking actions is low, on the other side, the precautionary approach becomes apt when scientific information is scant or the uncertainty 26 February 2020); ICCAT http://www.fao.org/geonetwork/srv/ en/main.home?uuid=fao-rfb-map-iccat (accessed on 26 February 2020); CCSBT http://www.fao.org/geonetwork/srv/en/ ...
... As an example, in research done by Hillary and colleagues [26], they discuss the pressing international concern and extensive scientific debate about the current state and future of tuna stocks worldwide and the capacity of RFMOs to manage corresponding fisheries effectively. ...
... Certain situations include predictions of imminent collapse with minimal chances of recovery despite the commercial catch moratorium. Taking the CCSBT as a case study, instead of full fishery closure for the depleted Southern bluefin tuna (Thunnus maccovii) stock, the RFMO had alternatively adopted a viable, scientifically tested, adaptive rebuilding strategy wherein the management procedure (MP) adopted involves a harvest control rule that fully specifies the total allowable catch as a function of key indicators of stock status, determines the recommended level of catch or effort based on the specified data and analysis, and adjusting future harvest levels every three years so as to meet the rebuilding targets agreed by CCSBT [26]. The selection of the optimal MP from a subset of candidate MPs that were developed 'was derived from extensive simulation testing, and involved first selecting a wide range of plausible scenarios for stock status and input data, ranging from pessimistic to optimistic, against which the alternative candidate MPs were tested and evaluated to ensure that they were robust to important uncertainties' [26]. ...
Article
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The sustainable management of the ocean as a global food source has been prominent in recent debates due to the disproportionate rate of human consumption, depletion of fish stocks and shortcomings in conservation efforts. Criticisms from various sectors on the effectiveness of Regional Fisheries Management Organizations (RFMO) in relation to their mandates have prompted performance reviews (PRs) to evaluate their efforts in fisheries management. Among concerns are slow implementation of comprehensive harvest strategies which use science-based indicators and management principles. Moreover, RFMOs are expected to apply the precautionary approach, in the hopes of anticipating, monitoring, preventing and mitigating potential threats. The emergent themes are revealed through content analysis pertaining to cooperation and compliance being essential to fisheries management activities in conjunction with choosing the right operational approaches and the proper implementation of various fisheries regulations. Government mandates and stakeholder’s recommendations support fisheries management organizations to function more effectively. This article discusses the role of coercive, normative and mimetic pressures in RFMOs activities, as described in recent performance reviews. It then analyses how RFMOs have implemented the precautionary approach together with science-based stock management and compliance measures, utilizing recent PRs to assess progress on relevant recommendations.
... small pelagics sardine (Sardinops sagax, Clupeidae) and anchovies (Engraulis encrasicolus, Engraulidae), hake (Merluccius capensis, Merluccius paradoxus, Merlucciidae) and rock lobster (Jasus lalandii, Palinuridae) (Bergh & Butterworth, 1987;De Oliveira & Butterworth, 2004;Geromont, De Oliveira, Johnston, & Cunningham, 1999)), Australia (Queensland spanner crab (Chionoecetes bairdi, Oregonidae) fishery (Dichmont & Brown, 2010) and the Northern Prawn Fishery (Pandalus borealis, Pandalidae) (Dichmont, Deng, & Punt, 2008;Dichmont, Ellis, & Bustamante, 2013)), and other fisheries across the globe (Goethel et al., 2019;ICES, 2019). Recently, the five tuna Regional Fisheries Management Organisations (tRFMOs) have begun developing recovery and long-term management plans for a range of stocks using MSE and have already implemented MPs in a few cases (Hillary et al., 2016;Preece, Davies, & Hillary, 2018). Each tRFMO includes a number of member states, generally coastal states that adjoin the oceans which the regional organization covers (Chang, 2014) could cater for the uncertainties associated with assessments. ...
... fish_MSE_Vis/) a large cryptic biomass that becomes a lot lower when we use asymptotic selectivity (Butterworth, Rademeyer, Brandao, Geromont, & Johnston, 2014). A similar issue was detected in CCSBT and corrected in the plausible OMs chosen (Hillary et al., 2016). ...
... An MSE was completed for southern bluefin tuna in 2011 (having begun in 2001), resulting in the Commission adopting a fully specified MP called the "Bali Procedure" (Hillary et al., 2016). The ...
Article
The five Regional Fishery Management Organizations dedicated to tunas (tRFMOs) are all either developing or implementing Management Strategy Evaluations (MSEs) to provide advice for the stocks under their competencies. Providing a comparative overview will help tRFMOs to learn from one another and to collaborate on common solutions and may also help to more clearly define the challenges of building decision support tools in contexts of large scientific uncertainty and where management requires cooperation across multiple stakeholders characterized by unequal power and divergent interests. For example, our overview showed that in most cases, a grid‐based design with an emphasis on structural uncertainty has been adopted. However, uncertainties such as sampling errors and non‐stationarity of important ecological processes, which are of potentially equal significance for demonstrating robustness of management procedures, were not considered. This paper identifies key issues for operating model (OM) design that challenges the tRFMOs, compares how these challenges are being met, summarizes what lessons have been learned and suggests a way forward. Although the current approach of using assessment models as the basis for OM design is a reasonable starting point, improvements should be made to the conditioning of OMs, especially with respect to enabling the inclusion of other important processes and uncertainties that are difficult to account for in stock assessments but that can crucially affect the robustness of advice. Attempts should also be made to improve documentation and communication of uncertainties that are included and those that are excluded from consideration in the process.
... The paradigm must reflect the non-equilibrium nature of marine systems and give greater importance to resource continuity in the face of regime shifts (Caddy and Seijo 2005). Feedback control is considered as an effective tool for such adaptive management (e.g., Tanaka 1980;Hilborn and Walters 1992;Geromont et al. 1999), and developing effective harvest control rules (HCRs) incorporating feedback control could be a key factor in coping with the fluctuations and uncertainties associated with utilizing fisheries resources. Thus, many fisheries scientists and management organizations worldwide have worked on the development of HCRs (e.g., Deroba and Bence 2008;Froese et al. 2011;Restrepo and Powers 1999). ...
... These rules are generally referred to as HCRs or MPs (Australian Government, Department of Agriculture, Fishery and Forestry 2007). Hilborn and Walters (1992) reported that a harvest strategy is a plan that states how the catch taken from the stock will be adjusted from year to year depending upon the size of stock, the economic or social conditions of the fishery, conditions of other stocks, and perhaps the state of uncertainty regarding the biological knowledge of the stock. ...
... Normally, harvest strategies implicitly involve major decisions about trade-offs between average yield and year-to-year variability and between robustness of stock size and maximization of catch size (Hilborn and Walters 1992). Those trade-offs are related to the HCRs, but there is no single rule that covers all of these objectives. ...
Chapter
Harvest control rules (HCRs) and management procedures (MPs) are used after stock assessment to determine the desirable amount of catch to achieve specified management objectives. These rules play a core role in linking the scientific stock assessment and practical fisheries management activities. Robust HCRs with respect to uncertainties are required for sustainable resource management, especially in light of the uncertainties inherent with fluctuating environmental conditions and climate systems. HCRs have to be evaluated to ensure that they maintain optimal biological production, stock size, and economic efficiency, but these objectives are not always compatible. Recently, a management strategy evaluation (MSE) framework for fisheries resource management has been developed that creates operating models (OMs) to simulate virtual population dynamics and evaluates the performance of the HCRs based on different strategies. We discuss feedback HCRs, which are one of the most effective strategies to manage fluctuating fisheries stocks. Feedback HCRs are empirical approaches to adjusting fishing intensity by sequentially updating information through the continuous monitoring of the state of the target stocks in response to present management activities. We also show a case study to test the performance of feedback HCRs with the aim of applying them to manage Japanese fish stocks and recommend allowable biological catches (ABCs).
... In addition, a scientific aerial survey is conducted each year in the GAB from January through March in which spotters search for surface schools of SBT (Eveson and Farley, 2016). The data collected are used to estimate an index of relative abundance of juvenile SBT, which forms a key input to the model used by the international organisation responsible for the management of SBT to set a global catch limit (Hillary et al., 2016). Having a reliable index of juvenile abundance in the model increases the probability of management meeting its rebuilding target, which is critical given the highly depleted level of the stock (Hillary et al., 2016). ...
... The data collected are used to estimate an index of relative abundance of juvenile SBT, which forms a key input to the model used by the international organisation responsible for the management of SBT to set a global catch limit (Hillary et al., 2016). Having a reliable index of juvenile abundance in the model increases the probability of management meeting its rebuilding target, which is critical given the highly depleted level of the stock (Hillary et al., 2016). Both the purse-seine fishery and the aerial survey rely on the availability of SBT in surface waters, and could benefit from a better https://doi.org/10. ...
Article
Large numbers of juvenile southern bluefin tuna (SBT; Thunnus maccoyii) migrate into the warm shelf waters of the Great Australian Bight (GAB) each austral summer. Whilst in the GAB, they aggregate in schools that spend substantial periods in the surface layer of the water column. In this study we investigate biological, temporal and environmental factors influencing this surfacing phenomena using an extensive archival tagging dataset collected between 1998 and 2011. High frequency data on the vertical movement of SBT collected by these tags were used to calculate the proportion of time fish spent in the shallowest 20 m during each day and night period. Estimates of fish location derived from light sensor data on the tags allowed us to investigate the influence that local environmental conditions had on a fish's surfacing behaviour. Although there is high variability in surfacing behaviour within and between individuals, some general patterns emerge. There are clear diel differences in surfacing, with the proportion of time fish spend at the surface tending to be high during most days and either very high (>90%) or very low (<10%) during most nights. Complex relationships were found between surfacing behaviour and the environmental variables considered (sea surface temperature, chlorophyll, salinity and wind speed). The results from this study have relevance to the commercial purse-seine fishery targeting surface schools of SBT in the GAB during the austral summer, as well as the scientific aerial survey conducted each summer that collects data on sightings of surface schools of SBT in order to derive a relative abundance index used directly in management.
... The SBT stock has been depleted by fishing with the spawning biomass (adults contributing to the population) estimated to have been decreased as low as 3-8% of its original size (CCSBT, 2011;Hillary et al., 2012). In response to this depletion, a formal management procedure (MP) was adopted by the CCSBT in 2011 and forms a central component of the rebuilding plan for the stock (Hillary et al., 2012(Hillary et al., , 2015. The current MP uses an index of abundance of 2-4 year old SBT derived from a scientific aerial survey conducted each summer in the GAB in which spotters search for surface schools of SBT (Eveson and Farley, 2016;Hillary et al., 2015). ...
... In response to this depletion, a formal management procedure (MP) was adopted by the CCSBT in 2011 and forms a central component of the rebuilding plan for the stock (Hillary et al., 2012(Hillary et al., , 2015. The current MP uses an index of abundance of 2-4 year old SBT derived from a scientific aerial survey conducted each summer in the GAB in which spotters search for surface schools of SBT (Eveson and Farley, 2016;Hillary et al., 2015). Success of the aerial survey relies on the availability of SBT in surface waters. ...
Article
Large numbers of juvenile southern bluefin tuna (SBT; Thunnus maccoyii) migrate into the warm shelf waters of the Great Australian Bight (GAB) each austral summer. Whilst in the GAB, they are the focus of a commercially important Australian fishery. Recent expansion of activities associated with oil and gas exploration in the GAB over the last five years has raised concerns that noise associated with geophysical surveys and exploratory drilling activities may impact on the migration and behaviour of SBT, with potential flow-on effects on the commercial fishery and current monitoring of the population for management purposes. As a first step in identifying the potential impacts of expansion of oil and gas exploration activities in the GAB on SBT, we establish the historical extent of these activities in the GAB with a primary focus on geophysical surveys. Potential overlap with the distribution of juvenile SBT in the GAB determined from an archival tag dataset (1998–2011) was then explored. Geophysical surveys have occurred throughout the vast majority of the region since 1960, with the size of energy sources used in surveys and the extent of areas surveyed increasing through time. The use of more complex, higher density 3D surveys has increased gradually since 2000. The timing and distribution of exploration activity has had varying degrees of overlap with SBT occurrence and distribution as described by tagged fish. Determining robust measures of the responses to surveys however, is difficult due to a paucity of data on the hearing capabilities of SBT, uncertainties in the true extent of spatial overlap of activities and tagged fish resulting from geolocation methods used for position estimation from archival tag data, complexities in the drivers of behaviour in SBT, and limitations with using observational data to determine cause-and-effect relationships. These difficulties are typical not just of SBT and the GAB region, but apply to investigations of the responses of marine animals to geophysical surveys more broadly. The data presented in this study, however, represent a first step towards understanding oil and gas exploration within a defined region of the Australian marine environment, and provide important context for exploring the potential impact of such activities on a commercially important top order predator of the GAB ecosystem.
... Scientific REPoRTS | (2018) 8:14553 | DOI: 10.1038/s41598-018-32949-3 juvenile SBT to: characterize movement rates conditional on behavioural state (resident or migrating); quantify the extent and synchronicity of the migrations of individuals to and from the GAB; and determine key areas of residency and, by association, potentially important habitat. The GAB supports a valuable large-scale fishery for SBT, as well as a number of scientific research programs designed to monitor SBT for international management purposes (Hillary et al. 18 ). Thus, understanding SBT migration to and from the area is of high importance to an international fishery, and more broadly, it contributes to a better understanding of the entire region, which is one of Australia's most valuable marine ecosystems 19 . ...
Article
Full-text available
Large scale migrations are a key component of the life history of many marine species. We quantified the annual migration cycle of juvenile southern bluefin tuna (Thunnus maccoyii; SBT) and spatiotemporal variability in this cycle, based on a multi-decadal electronic tagging dataset. Behaviour-switching models allowed for the identification of cohesive areas of residency and classified the temporal sequence of movements within a migration cycle from austral summer foraging grounds in the Great Australian Bight (GAB) to winter foraging grounds in the Indian Ocean and Tasman Sea and back to the GAB. Although specific regions within the Indian Ocean were frequented, individuals did not always return to the same area in consecutive years. Outward migrations from the GAB were typically longer than return migrations back to the GAB. The timing of individual arrivals to the GAB, which may be driven by seasonality in prey availability, was more cohesive than the timing of departures from the GAB, which may be subject to the physiological condition of SBT. A valuable fishery for SBT operates in the GAB, as do a number of scientific research programs designed to monitor SBT for management purposes; thus, understanding SBT migration to and from the area is of high importance to a number of stakeholders.
... To date only one tRFMO has completed an MSE and implemented a fully specified MP. The Commission for the Conservation of Southern Bluefin Tuna (CCSBT) adopted an MP for southern bluefin tuna (Thunnus maccoyii) in 2011 (Hillary et al. 2016), which has been used to set the global total allowable catch (TAC) from 2012 to 2020. The CCSBT has recently commenced development of a revised MP (given imminent changes to some of the key sources of input data) to be used for setting the TAC from 2021 (CCSBT 2017a(CCSBT , 2017b. ...
Article
Full-text available
The use of management strategy evaluation (MSE) to design and test candidate fisheries management approaches is expanding globally. Participation of managers, scientists, and stakeholders should be an integral component of the MSE process. Open and effective communication among these groups is essential for the success of the MSE and the adoption of the management approach based on it. The highly technical nature of MSE and newness of the approach to many audiences present considerable communication challenges and have, unfortunately, slowed progress in some cases. We draw on diverse experiences with MSE to identify two areas in which the implementation of MSE in multinational fora may be improved: (i) the use of formally constituted “intermediary groups” as a forum for exchange at the management–science interface and (ii) the development of engaging, yet uncomplicated, visual communication tools for conveying key results to different audiences at each stage. While our focus is the MSE processes underway in the regional fisheries management organizations for tunas and tuna-like species, the advice provided is also pertinent for other fisheries, international and domestic alike, pursuing MSE.
... By comparing the simulated outcomes among alternative management strategies, that study quantified the effectiveness of the effort management as implemented using day closures. The quantitative evaluation of the fisheries management outcomes under diverse management objectives and strategies using computer simulation is becoming important for the success of fisheries management (Edwards & Dankel 2016, Hillary et al. 2016. ...
Article
Proper fisheries management is difficult in fisheries targeting small pelagic fish that are subject to climate-induced oceanic regime shifts. A favourable regime tends to induce capa - city investments, but the results of these investments turn out to be irreducible overcapacity under the next unfavourable regime. The Japanese purse seine fishery studied here, which targets small pelagic fish, is a typical example of such overcapacity. However, we demonstrate that this fishery represents a best practice of properly designed effort management in recent years through its quantitative evaluation. Generalized liner mixed models (GLMMs) applied to daily logbook data revealed that effort restrictions on daily purse seine operations (in terms of the duration and the total number of operations per ship and day) significantly reduced total fishing efforts on chub mackerel. Stochastic simulations based on the parameters estimated in GLMMs quantified the extent of the potential catch reduction by the effort reductions at approximately 20%. Combined with the effect of another concurrently implemented management measure, i.e. day closures, the net effects of the effort management on the total catch reduction were estimated at 30%. Because the quota uptake percentages in this fishery were 60-80% during the study period, we conclude that the effort management helped avoid overshooting of the quota and consequent seasonal closures.
... The development of a spatially explicit integrated stock assessment for SBT has been previously proposed (e.g., Hillary et al., 2016). ...
Article
Full-text available
Archival tagging studies of southern bluefin tuna (SBT, Thunnus maccoyii) have revealed that juveniles residing in the Great Australian Bight (GAB) over the austral summer undertake seasonal cyclic migrations to the southeast Indian Ocean and the Tasman Sea during winter. However, there remains disagreement about the extent of mixing between juvenile SBT regularly caught by longline fleets south of Africa and those observed in the GAB. Some researchers have argued that archival tag recoveries indicate most juveniles reside in the GAB over the austral summer. Others have suggested that recoveries of conventional and archival tags are better explained by a juvenile population consisting of separate groups on the eastern and western sides of the Indian Ocean with limited intermixing. We present analyses of catch and tag recovery data and re-examine archival tagging studies. The evidence provided strongly favors the hypothesis of separate juvenile subgroups, or contingents, with limited intermixing. We draw some tentative conclusions about the nature of the putative contingents and discuss some implications of these findings for the interpretation of existing datasets and future research priorities. We also provide the first evidence that the migration choices of juveniles that summer in the GAB are influenced by fidelity to winter feeding grounds and suggest this helps explain the collapse of the surface fishery off New South Wales in the 1980s.
... The International Commission for the Conservation of Atlantic Tunas (ICCAT), the RFMO charged with management and science of Atlantic tunas and associated species, has agreed to adopt harvest control rules (HCRs) for eight priority stocks by 2020 (ICCAT 2015). The ICCAT MSE initiatives stem from guidance provided in the United Nations Fish Stocks Agreement and has been motivated by the success of an MSE-based management procedure for southern bluefin tuna (Thunnus maccoyii; Hillary et al. 2016), which helped address similar management challenges in that fishery. ...
Article
Full-text available
Management strategy evaluation (MSE) is a simulation-based approach to examine the efficacy of management options in achieving fishery-, ecosystem-, and socioeconomic-related objectives while integrating over system uncertainties. As a form of structured decision analysis, MSE is amenable to stakeholder involvement, which can reduce implementation barriers associated with non-transparent decision-making procedures. Based on analysis of three MSE processes (Atlantic tunas, Atlantic herring, and eastern oysters), we provide suggestions for improving stakeholder engagement in MSE. By assembling a workgroup and modeling team with diverse backgrounds, including professional facilitators, communication liaisons, and social scientists, dialogue can be improved and an atmosphere of mutual learning fostered. Communication further benefits from clearly defining roles, responsibilities, and terms of engagement for all involved; explicitly and transparently identifying goals and objectives of the MSE before modeling has begun; and, when appropriate, revisiting goals and objectives throughout the MSE process. Although MSEs are not without limitations, the participatory modeling framework, wherein stakeholders are actively engaged at each stage of MSE development, provides a useful mechanism to support fisheries management.
... We undertake a comparative evaluation of the impact of size imputation relative to typical axes of uncertainty in stock assessments. The hypothesis is evaluated that variability among CAS imputations leads to a greater degree of variability in estimates of man-agement reference points than traditional axes of uncertainty, such as natural mortality rate and choice of relative abundance index (e.g., Hillary et al. 2016). ...
Article
Full-text available
Virtual population analysis (VPA) is used in many stock assessment settings and requires a total catch-at-age data set where an age is assigned to each fish that has been caught. These data sets are typically constructed using ad hoc methods that rely on numerous assumptions. Although approaches are available to account for observation error in these data, no statistically rigorous methods have been developed to account for uncertainty from data processing. To address this, we investigated a Bayesian multiple imputation approach to filling missing size data. Using Atlantic yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus) as case studies, we evaluated the hypothesis that data processing is as important in determining management reference points in stock assessments as conventional sources of uncertainty. Size imputation models accounting for location, season, and year provided good predictive capacity. Uncertainty from data processing could be large; however, the circumstances for this were unpredictable and varied depending on the stock. These results indicate that VPA assessments should attempt to account for uncertainty in data processing to avoid potentially large compression of uncertainty in assessment results.
... Management of the international commercial fishery is overseen by the Commission for the Conservation of Southern Bluefin Tuna, with global total allowable catches for the species determined by a management procedure since 2011 ( Hillary et al. 2015). The management procedure is designed to recover the spawning biomass to 20 per cent of the pre-fishing biomass by 2035 (CCSBT 2014; Figure MAR30). ...
... It ranges across the four oceans of the southern hemisphere, with a single spawning ground south of Indonesia in austral summer, and juvenile summer feeding grounds in the Great Australian Bight 3,24-26 . SBT has been harvested by coastal and international fleets since the early 1950s, leaving the spawning stock depleted to below 10% of estimated pre-exploitation levels 27 , although the exact level is uncertain. The main current fisheries target juveniles (ages 1-4) by purseseine in the Great Australian Bight, and subadults (ages 3-10) by longline on the high seas and coastal waters of Australia, New Zealand and South Africa. ...
Article
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Southern bluefin tuna is a highly valuable, severely depleted species, whose abundance and productivity have been difficult to assess with conventional fishery data. Here we use large-scale genotyping to look for parent–offspring pairs among 14,000 tissue samples of juvenile and adult tuna collected from the fisheries, finding 45 pairs in total. Using a modified mark-recapture framework where 'recaptures' are kin rather than individuals, we can estimate adult abundance and other demographic parameters such as survival, without needing to use contentious fishery catch or effort data. Our abundance estimates are substantially higher and more precise than previously thought, indicating a somewhat less-depleted and more productive stock. More broadly, this technique of 'close-kin mark-recapture' has widespread utility in fisheries and wildlife conservation. It estimates a key parameter for management— the absolute abundance of adults—while avoiding the expense of independent surveys or tag-release programmes, and the interpretational problems of fishery catch rates.
... However, in 2011, the CCSBT implemented a management procedure that was an adaptive rebuilding strategy to set a catch limit. The management procedure was fully tested in advance through simulations using a wide range of uncertainties in stock dynamics, with the goal of helping the species' stock reach the interim rebuilding target of 20% of the original spawning stock biomass (Hillary et al. 2015). A slight recovery of the spawning stock has recently been observed (CCSBT 2015). ...
Article
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We investigated the foraging ecology of southern bluefin tuna Thunnus maccoyii in open-ocean habitats of temperate waters in the southern hemisphere by analyzing their stomach contents. Samples were collected from longline vessels over 15 yr (n = 4649). Of the prey, 51% by weight were cephalopods and 46% were teleosts. These values differ from those in the literature for other top predators in the open oceans, for which teleosts compose the largest portion of prey. The dominance of cephalopods also differs from the pattern for juveniles in previous studies in their coastal habitat, where most of the prey are teleosts. Thus, a distinct shift of prey occurs along with the habitat shift due to ontogenetic development. By weight, important prey were ommastrephid (18%), lycoteuthid (12%), and argonautid (1%) cephalopods and nomeid (8%, mainly Cubiceps caeruleus), paralepidid (7%), bramid (6%), and alepisaurid (6%) teleosts. The prey composition was relatively consistent among tuna sizes, sea surface temperatures, and years; changes in prey composition were due largely to differences in the cephalopod prey. Cephalopods belonging to the families Lycoteuthidae and Argonautidae contributed to the prey only off the southern coast of Africa and near Tasmania, respectively. Lycoteuthids occurred at lower sea surface temperatures than ommastrephids off the southern coast of Africa. Small ommastrephids were dominant in smaller tuna in the southeastern Indian Ocean. Our data provide basic information that will improve our understanding of the oceanic food webs in southern temperate waters.
... We undertake a comparative evaluation of the impact of size imputation relative to typical axes of uncertainty in stock assessments. The hypothesis is evaluated that variability among CAS imputations leads to a greater degree of variability in estimates of man-agement reference points than traditional axes of uncertainty, such as natural mortality rate and choice of relative abundance index (e.g., Hillary et al. 2016). ...
... In turn, in reality, the assumption of perfect implementation of any rebuilding plan is unlikely [26], and corrections needed to achieve recovery within the desired timeline will be necessary. Ideally, this would be through a formalised 'management procedure' such as that agreed in order to recover southern bluefin tuna, which can be tested for robustness against uncertainty [8]. ...
Article
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South Pacific albacore is a species of primary importance in the longline fishery of a number of Small Island Developing States in the Western and Central Pacific Ocean. Despite the fact that the stock is assessed as not being subject to overfishing and not overfished, economic returns have declined significantly over the past decade. This has led to calls for management intervention. Given stated biological and economic objectives for the fishery, members of the Pacific Islands Forum Fisheries Agency proposed an interim stock target reference point to the Western and Central Pacific Fisheries Commission that would imply a larger stock size, higher catch rates and a more profitable fishery (FFA Members, 2015). The purpose of this study is to examine the biological and economic consequences along the trajectories of two distinct longline effort reduction regimes that achieve the proposed target reference point within 20 years and review the trade-offs in terms of forgone catch or effort and forgone revenue. The two effort regimes examined are a one-off reduction implemented immediately, and a phased reduction under which effort is reduced by a fixed percent each year. The results are discussed in the light of wider Pacific Island objectives for fishery production and fleet profitability and highlights the importance of moving beyond a purely biological stock-based focus when providing management advice.
... As part of the rebuilding process for SBT, a management procedure-a predefined rule used to deter- mine the catch level required to meet a specific rebuilding target [5]-was recently adopted by the Commission for the Conservation of Southern Bluefin Tuna [6]. The aerial survey esti- mates form one of two key data inputs to the management procedure (the other being longline catch-per-unit-effort data on sub-adult and adult fish), and are the only fishery-independent input [7]. ...
Article
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Southern bluefin tuna (SBT) is a valuable species that has been subject to high exploitation rates since the 1950s. In 2011, the spawning stock biomass was estimated to be at a historically low level, at only 5% of pre-fished biomass. A key component for managing and rebuilding the stock is having reliable, fishery-independent estimates of juvenile abundance. This paper describes how such estimates have been constructed from aerial surveys of juvenile (age 2–4) SBT conducted annually in the Great Australian Bight from 1993–2000 and 2005–2009. During these surveys, observers flew along pre-set transect lines searching for surface schools of SBT. Data were collected on the location and biomass of SBT sightings, and on the environmental conditions present during the survey. Sea surface temperature (SST) was found to correlate with the size (biomass) of schools, and several environmental variables, SST and wind speed in particular, were found to correlate with the number of sightings (presumably by affecting the ability of observers to see surface schools as well as whether fish were present at the surface). In addition, observers changed over time and differed in their aptitude for spotting tuna. Thus, generalized linear mixed models (GLMMs) were used to standardize the sightings and biomass data to a common set of observers and environmental conditions in order to produce an annual time series of relative abundance estimates. These estimates, which form one of two key inputs to the management procedure used by the international Commission for the Conservation of Southern Bluefin Tuna to set the global catch quota, suggest juvenile abundance was highest in the first years of the survey (1993–1996), after which it declined and fluctuated around a level about four times lower.
... Our results may provide insight into the general public's preference for managing other fisheries unless Japanese consumers possess a unique preference for tuna species that they do not share for other fish. Fishery closures are often implemented to conserve heavily overexploited fish stocks, which economic theory supports as optimal under very limited circumstances (Clark & Munro, 2017;Hillary et al., 2017). This study showed that such a measure is similarly not supported by the public. ...
Article
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Many tuna stocks are being depleted, and the bluefin tuna stock is of particular concern because it has been designated endangered or severely overexploited. Japan's actions are pivotal in protecting bluefin tuna stocks because high volumes are caught for sushi/sashimi. However, the efforts of the Japanese government to conserve these valuable stocks have been limited or even counterproductive, as the government currently seems to prioritise the short-term interests of the domestic fishing industry. In this study, public preferences are revealed, potentially affecting the position of the Japanese government in the long run by quantifying the extent to which public support could be generated with changes in specific features of the international agreement on the conservation and management of tuna resources. With a choice experiment that focused on the catch limits, target species, and parties who would be responsible for the expenses of monitoring, this paper finds that a fishery closure is the scenario least likely to inspire public support for tuna conservation. Japanese consumers favour a prompt management response to the overfishing of tuna fisheries beginning immediately when the exploitation of the stocks reaches an unsustainable level. Atlantic/Pacific bluefin tuna, compared to other tuna species, is a top conservation priority for Japanese consumers. These results indicate that although the current movement towards conserving bluefin tuna is publicly supported, conservation actions should have been initiated sufficiently early to avoid a drastic catch reduction before the stock was overfished or the population became endangered.
... An MP may be either modelbased, where a stock assessment is used to estimate stock status and set management measures (e.g. Kell et al., 2005), or empirical where a trend in an indicator is used to set the catch (Hillary et al., 2016). MSEs for data-limited purposes are somewhat rarer, although there are notable studies. ...
Article
Worldwide, the majorities of fish stocks are data-limited and lack fully quantitative stock assessments. Within ICES, such data-limited stocks are currently managed by setting total allowable catch without the use of target reference points. To ensure that such advice is precautionary, we used management strategy evaluation to evaluate an empirical rule that bases catch advice on recent catches, information from a biomass survey index, catch length frequencies, and MSY reference point proxies. Twenty-nine fish stocks were simulated covering a wide range of life histories. The performance of the rule varied substantially between stocks, and the risk of breaching limit reference points was inversely correlated to the von Bertalanffy growth parameter k. Stocks with k>0.32 year−1 had a high probability of stock collapse. A time series cluster analysis revealed four types of dynamics, i.e. groups with similar terminal spawning stock biomass (collapsed, BMSY, 2BMSY, 3BMSY). It was shown that a single generic catch rule cannot be applied across all life histories, and management should instead be linked to life-history traits, and in particular, the nature of the time series of stock metrics. The lessons learnt can help future work to shape scientific research into data-limited fisheries management and to ensure that fisheries are MSY compliant and precautionary.
... Over the past decade, there has been a notable increase in MSEs being undertaken globally (e.g. ICES, 2020ICES, , 2022Hillary et al., 2016;Deroba et al., 2019). There has also been an increase in cases within SA, where MPs have been temporarily set aside and not used to provide management advice. ...
Article
South Africa is well known for being one of the first countries to implement management procedures that had been fully tested using Management Strategy Evaluation (MSE). Beginning in the early 1990s, Operational Management Procedures (OMPs) have been developed and implemented for the fisheries for seven important commercial species. Barring a few teething problems, for the first two decades, South Africa's track record of OMP implementation, with OMP-recommended catch limits being signed off by the responsible Minister without change, was exemplary. The sustainable management of some fisheries using OMPs continues without mishap, with regular reviews. However, the past decade has resulted in a number of deviations of decisions from OMP outputs following the declaration of “Exceptional Circumstances” (ECs). This occurred when a resource moved outside the range of scenarios tested at the time the OMP was developed. The reasons why ECs were declared, the methods used to recommend catch limits during ECs and whether ECs might have been avoided are reviewed. The experience gained over three decades of managing fisheries using MSE provides a basis to assess whether the highly time-intensive task of developing these OMPs has been worth the expected benefits, and to provide recommendations related to lessons learned.
... It is recognized that it isn't possible to design a harvest control rule that accounts for all possible contingencies (Butterworth, 2008). This highlights the need for further development of preagreed "exceptional circumstances" rules to handle events that are outside the bounds considered in the testing phase, or that provide new information that underscores the need to review the original performance of the HCR (Hillary et al., 2016). ...
Article
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The Torres Strait tropical rock lobster Panulirus ornatus (TRL) fishery is of immense social, cultural and economic importance to the region’s Indigenous fishers from both Australia and Papua New Guinea (PNG). During 2020, the COVID-19 pandemic indirectly impacted this fishery as well as a number of other fisheries reliant on international export markets. The TRL fishery is managed using an empirical (data-based) Harvest Control Rule (eHCR) to rapidly provide a recommended biological catch (RBC), based on catch, fishery-independent survey indices and catch-per-unit-effort (CPUE). Here, we summarize the impacts of COVID-19 on each of these critical data inputs and discuss whether the eHCR was considered adequately resilient to this unprecedented disruption to the system. Next, we use a quantitative supply chain index to analyze the impact of disruptions to the supply chain, and inform on potential adaptation strategies. The catch and CPUE data were impacted to varying degrees by external constraints influencing fishing effort, but the fishery-independent survey wasn’t affected and hence there remains an unbroken survey time-series for the fishery extending back to 1989. The eHCR was shown to be reasonably robust because it incorporates longer-term trends over a 5-year period, and accords substantially more weighting (80%) to the fishery-independent survey rather than CPUE data which can be affected by trade and other disruptions. Despite the eHCR not having been tested for scenarios such as a global pandemic, this robustness is a positive given the types of disruptions we will likely face in future climate. The weak links identified in the supply chain were the same as those previously highlighted as sensitive to climate change disruptions. Our supply chain analysis quantifies the impact on system resilience of alternative paths connecting producers to consumers and reinforces that supply chains may be particularly vulnerable to external disruptions if they are not sufficiently diverse.
... They can also be of value in the process of developing Management Strategy Evaluation (MSE) frameworks, where integrated models are commonly used for conditioning Operating Models (OMs) to evaluate the performance of harvest control rules (Butterworth and Punt, 1999;Punt et al., 2015;Sharma et al., 2020). This often involves modelling the resource dynamics by fitting integrated assessment models to the available data based on some statistical criterion, such as a maximum likelihood (Hillary et al., 2015). The aim of conditioning is to discard OMs that do not fit the data satisfactorily and are consequently inconsistent with the observations and, therefore, implausible . ...
Article
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Integrated analysis has increasingly been the preferred approach for conducting stock assessments and providing the basis for management advice for fish and invertebrate stocks around the world. Many decisions are required when developing integrated stock assessments. For example, the analyst needs to decide whether the model fits the data, if the optimization was successful, if estimates are consistent retrospectively, and if the model is suitable to predict future stock responses to fishing. This study provides practical guidelines for implementing selected diagnostic tools that can assist analysts in identifying problems with model specifications and alternatives that can be explored to minimize or eliminate such problems. Emphasis is placed on reviewing the implementation and interpretation of contemporary model diagnostic tools. We first describe each diagnostic approach and its utility. We then proceed by providing a "cookbook recipe" on how to implement each of the diagnostics, together with an interpretation of the results, using two worked examples of integrated stock assessments with Stock Synthesis. Further, we provide a conceptual flow chart that lays out a generic process of model development and selection using the presented model diagnostics. Based on this, we propose the following four properties as objective criteria for evaluating the plausibility of a model: (1) model convergence, (2) fit to the data, (3) model consistency, and (4) prediction skill. It would greatly benefit the stock assessment community if the next generation of stock assessment models could include the diagnostic tests presented in this study as a set of open source tools.
... The five tuna RFMOs have carried out some type of MSE work, including consultation on management objectives, characterization of uncertainty of stocks' dynamics and observation, and evaluation of HSs [22]. The CCSBT has pioneered the adoption of HSs for tunas: From 2002 to 2011, the CCSBT conducted extensive work to develop an HS known as the "Bali procedure" that was adopted to help rebuild Southern bluefin by setting catch limits periodically [50]. The development of this work was initiated by a technical group of experts through specific workshops. ...
Article
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Tunas sustain important fisheries that face sustainability challenges worldwide, including the uncertainty inherent to natural systems. The Kobe process aims at harmonizing the scientific advice and management recommendations in tuna regional fisheries management organizations (RFMOs) toward supporting the sustainable exploitation of tunas globally. In this context, we review the similarities and differences among tuna RFMOs, focusing on stock assessment methodologies, use of information, characterization of uncertainty and communication of advice. Also, under the Kobe process, tuna RFMOs have committed to a path of adopting harvest strategies (HSs), also known as management procedures (MPs), which are the series of actions undertaken to monitor the stock, make management decisions, and implement the management measures. The adoption of HSs for tuna stocks is supported by Management Strategy Evaluation (MSE), which is considered the most appropriate way to assess the consequences of uncertainty for achieving fisheries management goals. Overall, notable progress has been made in achieving some of the Kobe objectives, but there are still some aspects that are inconsistent and need to be agreed upon, due to their management implications. First, not all RFMOs report on stock status based on maximum sustainable yield (MSY) as a reference. Instead, some use depletion level to represent the available fish biomass. Also, the definition of overexploited is not common in all oceans. Finally, very few stock assessments characterize all major sources of uncertainty inherent to fisheries. With regards to HSs, two different approaches are being followed: One is designed to adopt an automatic decision rule once the stock status and management quantities have been agreed upon (harvest control rules (HCRs), not strictly an HS) and the other aims at adopting all the components of HSs (data, use of information and decision rule).
... Apart from rebuilding plans, other stock-level and national-level measures contributed to regulating fishing pressure and rebuilding biomass. Notably, when multiple measures were implemented together to strengthen overall management intensity, the need for rebuilding plans was avoided (because the modelled stock at equilibrium was never overfished), consistent with previous suggestions for avoiding strict fishing moratoria 24,28 . The effect on stock status was particularly strong from enacting either the UNCA or the UNFSA ( Supplementary Fig. 5). ...
Article
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Which management actions work best to prevent or halt overfishing and to rebuild depleted populations? A comprehensive evaluation of multiple, co-occurring management actions on the sustainability status of marine populations has been lacking. Here, we compiled detailed management histories for 288 assessed fisheries from around the world (accounting for 45% of those with formal stock assessments) and used hierarchical time series analyses to estimate effects of different management interventions on trends in stock status. Rebuilding plans, applied less commonly than other management measures (implemented at some point historically for 43% of stocks), rapidly lowered fishing pressure toward target levels and emerged as the most important factor enabling overfished populations to recover. Additionally, the ratification of international fishing agreements, and harvest control rules specifying how catch limits should vary with population biomass, helped to reduce overfishing and rebuild biomass. Notably, we found that benefits of management actions are cumulative—as more are implemented, stock status improves and predicted long-term catches increase. Thus, a broad suite of management measures at all levels appears to be key to sustaining fish populations and food production.
... It is now becoming common for MSE to be used to test the harvest control rules that are based on model-based stock assessments, but it is less common to use MSE to test the combination of the assessment method and the harvest control rules (the management strategies developed by IWC (2012), Hillary et al. (2016) and ICES (2019a) being among the exceptions in this regard, although the population models underlying some of those management strategies are quite simple). The assessment used to provide the inputs for the harvest control rule is developed on a regular basis (possibly annual) taking into account the latest information to ensure that management decisions are based on the 'best available science' regarding the size, productivity and status of the stock. ...
Article
Model-based stock assessments form a key component of the management advice for fish and invertebrate stocks worldwide. It is important for such assessments to be peer-reviewed and to pass scientific scrutiny before they can be used to inform management decision making. While it is desirable for management decisions to be based on quantitative assessments that use as much of the available data as possible, this is not always the case. A proposed assessment may be found to be unsatisfactory during the peer-review process (even if it utilizes all of the available data), leading to decisions being made using simpler approaches. This paper provides a synthesis across seven jurisdictions of the types of diagnostic statistics and plots that can be used to evaluate whether a proposed assessment is ‘best available science’, summarizes several cases where a proposed assessment was not accepted for use in management, and how jurisdictions are able to provide management advice when a stock assessment is ‘rejected.’ The paper concludes with recommended general practices for reducing subjectivity when deciding whether to accept an assessment and how to provide advice when a proposed assessment is rejected.
... They have been used to develop criteria to delist endangered species, such as sea otters (Enhydra lutris nereis), from the U.S. Endangered Species Act (Ralls et al., 1996). They have also been used to, for example, estimate absolute population size to implement harvest control rules for southern bluefin tuna (Thunnus maccoyii) (Hillary et al., 2016) and to estimate breeding population size to model population size changes for white shark (Carcharodon carcharias) in Western Australia (Braccini et al., 2017;Ovenden et al., 2016). Genetic methods rely on obtaining tissue samples from individuals for DNA extraction. ...
Chapter
Carefully designed studies involving thousands of SNP loci can provide new insight into existing questions of evolution and ecology with increased precision and accuracy (Andrews and Luikart, 2014). Determining causal relationships among genomic variation, phenotypes, and the environment allows a better understanding of the genetic basis of adaptive genetic variation and speciation (Bernatchez, 2016; Nielsen et al., 2009). However, despite the potential for genomics to improve management and conservation practices through improved understanding, it is perceived as difficult to make the transition from theory to practice (McMahon et al., 2014; Shafer et al., 2015). In part, this chapter addresses the transition for elasmobranch species. It begins with the practical aspects of generating genomic data, then focuses on how genomics and existing methods of population genetics are actively being used to address knowledge gaps that are important for conservation and management, such as population structure, population size, and reproductive biology. We review the strengths and weaknesses of genomics and genetics methods to provide insight and realistic expectations for workers involved in theoretical and applied research on elasmobranchs. Details of other applications of DNA technology to elasmobranch species, such as assaying DNA from the environment (eDNA; see Chapter 14 in this volume) and studying hybridization (Marino et al., 2015; Morgan et al., 2012), can be found elsewhere.
... We undertake a comparative evaluation of the impact of size imputation relative to typical axes of uncertainty in stock assessments. The hypothesis is evaluated that variability among CAS imputations leads to a greater degree of variability in estimates of man-agement reference points than traditional axes of uncertainty, such as natural mortality rate and choice of relative abundance index (e.g., Hillary et al. 2016). ...
... They can also be of value in the process of developing Management Strategy Evaluation (MSE) frameworks, where integrated models are commonly used for conditioning Operating Models (OMs) to evaluate the performance of harvest control rules (Butterworth and Punt, 1999;Punt et al., 2015;Sharma et al., 2020). This often involves modelling the resource dynamics by fitting integrated assessment models to the available data based on some statistical criterion, such as a maximum likelihood (Hillary et al., 2015). The aim of conditioning is to discard OMs that do not fit the data satisfactorily and are consequently inconsistent with the observations and, therefore, implausible . ...
... The Operating Model (OM) was conditioning on turbot life-history characteristics and the HCR was based on that used by the Commission for the Conservation of Southern Bluefin Tuna (CCSBT). The HCR has several parameters that require tuning (Hillary et al., 2016). When tuning an HCR the parameters are found by choosing values that best meet the objectives of asset and stakeholders; i.e. optimises the outcomes modelled as a reward function. ...
Technical Report
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The Workshop on the Development of Quantitative Assessment Methodologies based on Life-history traits, exploitation characteristics, and other relevant parameters for data-limited stocks (WKLIFE) focuses on the provision of sound advice rules for data-limited stock (DLS) assess-ments that are within the ICES MSY framework. This ninth workshop was convened to further address the challenges to the evidence base for the provision of ICES advice with specific refer-ence to DLS. The reviewers’ report of WKLIFE VIII (ICES, 2018) was used as the basis to draft ICES technical guidance on advice rules for stocks in Categories 3 and 4 following the meeting in 2018. The draft document reflected the conclusions of the WKLIFE VIII meeting report but in order to provide a good guidance document to the ICES community, some of the text and steps identified required further elaboration. The intersessional work undertaken ahead of this WKLIFE IX meeting provided a basis to revise the draft and during this WKLIFE IX meeting, the draft technical guidance was revised and updated. The draft report of, and recommendations from, the ICES workshop on data-limited stocks of short-lived species (WKDLSSLS) was re-viewed and additional simulation studies undertaken during WKLIFE IX, and the need for spe-cific advice rules for these stocks examined. Annex 3 to this report contains the revised and agreed text by the participants at WKLIFE IX. Specifically, the draft ICES technical guidance was revised and amended based on the work presented at WKLIFE IX and its previous workshops with respect to short-term forecasts utilising a surplus production model (SPiCT – Stochastic Production model in Continuous Time), and harvest control rules for length-based approaches, for short-lived species, and for bycatch elasmobranch stocks.
Article
Large pelagic fishes are assessed and managed by tuna Regional Fisheries Management Organizations (tRFMOs). These organizations have been criticized for not meeting conservation objectives, which may relate to aspects of governance and management. No previous studies have systematically evaluated why management performance differs among tRFMOs and among stocks within each tRFMO. In this study, we collected data on the nature of research, management, enforcement and socioeconomics of management systems in the five principal tRFMOs of the world's oceans. We quantified influences of economic and fishery-related factors on these management characteristics and examined how these factors vary among tRFMOs. We found that tRFMOs with a greater number of member countries, a greater economic dependency on tuna resources, a lower mean per capita gross domestic product, a greater number of fishing vessels and smaller vessels were associated with less intensive research, management and enforcement in these tuna fisheries. We also quantified the influence of specific management attributes and of biological, economic and fishery-related factors on the trends and current status of large pelagic fish stocks in these regions. The most important factors correlated with trends and current stock status were external to the management systems, and included stock size, age at maturity, ex-vessel price and economic dependency of countries on tuna fisheries. To improve the overall status of large pelagic fish stocks in the global high seas, more intensive data collection, research and management are needed in certain areas, especially in the Indian Ocean, and for certain stocks, especially non-target species.
Article
Biological aspects of butterfly kingfish Gasterochisma melampus were examined using Japanese longline fishery data and research data collected for over 20 years. Butterfly kingfish were distributed in a continuous band around the circumpolar region between 35°S and 45°S. The southern limit of distribution corresponded with the sub-Antarctic front. The estimated global total annual catch for butterfly kingfish ranged from 613 to 3699 t (mean 1859 t) with Japan taking the largest proportion of the total catch. Large, adult butterfly kingfish spawn in the south-eastern Pacific, whereas smaller, immature fish are distributed in feeding grounds in the area extending across the Atlantic and Indian Oceans to the south-western Pacific Ocean. Catch per unit effort (CPUE) data for fish in the feeding grounds from 1993 to 2016 were compared with the CPUE value from 1970. These data indicate that the stock is currently not likely to be depleted.
Article
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シミュレーションモデルを用いて様々な資源管理の方策を評価するmanagement strategy evaluation(MSE)は,水産資源や野生生物の管理を主な目的の一つとする水産資源学や応用生態学において重要なツールとなりつつある.ここでは,マサバの努力量管理のMSEにおいて統計モデルが用いられた一つの研究例を紹介する.この研究は,漁獲努力量(操業日数)と漁獲量の関係を確率モデルで表し,管理によって獲り控えられた漁獲分が個体群動態を通してその後の資源回復にどれだけ寄与したかをシミュレーションにより評価したものである.結果として,日々の漁獲量と出漁隻数を表す時系列データに潜む自己相関構造と,資源の増減に反応した漁業者の努力量の変化が努力量管理の効果に大きな影響を与えていることが明らかになった.通常のMSEでは努力量と漁獲量の関係(漁業動態)が単純な線形関係で表現されることが多いが,本研究の成果は漁業動態を実データに即した統計モデルで表現することの重要性を示している.今後,資源管理の分野の中で統計モデルが積極的に使われ,より実際的な管理方策の評価に繋がることを期待する.
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水産資源学は,生態学とは異なる側面を持っている.実験が難しく,主要なデータが漁業からのものであるという点で,不確実性が大きく,バイアスの混入もしばしば見られる.そのような問題に対処するため,古くから統計モデルの活用が積極的に進められてきた.水産資源学は,大きく分けて,資源評価と資源管理からなる.資源評価,資源管理で使われる統計モデルの概要を紹介する.生態学と水産資源学で使われる統計モデルには多くの共通点があり,統計モデルを媒介として,水産資源学と生態学の協調・融合が進むことを期待する.
Article
Indonesia is a member of three tuna Regional Fisheries Management Organisations (RFMOs), but currently has limited capacity to operationally manage its tuna fisheries to maximise benefits and minimise risks of overfishing. In 2014, the Government of Indonesia initiated discussions on the potential to develop formal harvest strategies for the management of tuna resources within its archipelagic waters. This article summarizes the development of potential empirical tuna harvest strategies for use in Indonesian archipelagic waters (Fisheries Management Areas 713, 714 and 715), using skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) as demonstration case studies. The outputs of area-specific components of Western Central Pacific Ocean stock assessment were used to condition prototype operating models for testing preliminary harvest strategies by management strategy evaluation. The case studies demonstrate the utility of scientific monitoring data to track trends in abundance of adult fish, without requiring complex stock assessment models. They also demonstrate the use of relatively simple, empirical harvest control rules to adjust the levels of fishing intensity of the Indonesian fleet to achieve specific management objectives for archipelagic waters in the context of wider regional management. The approach has a broad applicability to developing coastal nations with multi-gear fisheries and relatively limited data that harvest tuna, as well as participating in RFMOs for internationally managed stocks.
Thesis
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The extent of mixing of juveniles is an aspect of southern bluefin tuna (SBT) ecology that continues to be debated. Juvenile SBT are found either side of the Indian Ocean, south of Africa and off southern Australia. By the 1980s it was generally accepted that some juveniles migrated directly from waters off Western Australia as far west as the south eastern Atlantic Ocean. Although little was known about the movements of these individuals, they were assumed to remain mostly separate from juveniles off southern Australia. However, the introduction of electronic archival tags in the 1990s has strongly influenced theories of juvenile migration of SBT. Some researchers have claimed the archival tag recoveries suggest the great majority of juveniles summer in the Great Australian Bight, while others argue that conventional and archival tag recoveries are better described by juveniles either side of the Indian Ocean remaining separate. I provide a synthesis of historical catch and archival tag recovery data to assess the relative support for the two alternative theories. I develop a generalised linear mixed modelling approach that allows more comprehensive assessment of evidence of incomplete mixing in conventional tag recovery data. My analysis supports the hypothesis of juvenile subgroups remaining mostly separate either side of the Indian Ocean. Specifically, I describe evidence of a juvenile population consisting of contingents with distinct migratory behaviour. Recoveries of tags released from longline vessels provide evidence of fidelity to overwintering grounds. I argue the tag recovery data are consistent with contingents governed by the “entrainment” mechanism. The updated model of juvenile spatial dynamics that I describe reconciles archival tag recoveries with catch and conventional tag recovery data. The spatial dynamics I propose have important implications for the interpretation of existing datasets and for future priorities regarding SBT. Contingents governed by entrainment would influence how the population responds to fishing. I argue the entrainment mechanism contributed to the collapse of a commercial fishery for SBT off New South Wales during the 1980s. Additional findings from analyses of tag shedding and growth that were undertaken as part of my PhD studies are included as appendices.
Article
Bluefin tunas are iconic trans-ocean species; both their management and their science attract much attention. While outside input to the management of these species can advance international fisheries discussions, misleading criticism of management process can confuse already complex discussions. The focus lately has been on Pacific bluefin tuna (Thunnus orientalis, PBF) as stocks of the other two bluefin tunas are apparently recovering. Recently, the International Union for Conservation of Nature (IUCN) cast doubts on the scientific process behind scientific advice concerning PBF. In response, this study was designed to evaluate and compare factors contributing to the quality of scientific recommendations by international bodies conducting stock assessments of bluefin tunas, including the transparency issue highlighted by the IUCN. The relationship between the underlying factors and the indicators of the quality of scientific recommendations was also investigated. The results show comparable transparency in the scientific processes for the three bluefin tunas, whereas other factors vary. Overall, the scientific processes for all the three bluefin tunas are not problematic, but can be improved. In addition, transparency appears unrelated to the indicators of the quality of scientific recommendations studied here. The issue of transparency of scientific processes in tuna regional fisheries management organizations (RFMOs) and their scientific recommendations should therefore be discussed separately, although transparency is important for ensuring outside confidence in the management process. The objective comparisons presented here will hopefully improve scientific processes in tuna RFMOs by promoting further transparency.
Technical Report
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The main objective of the workshop was to review the recommendations of WKREF1 and consider how these might feed into a new reference points framework and guidelines for ICES. There were a number of presentations on the wider issues of best practice for reference points, the Allee effect, density dependence and the WKIRISH approach. The starting point was to try and develop a set of simplified and harmonised guidelines based on the WKREF1 report rather than evolving the current guidelines to include the WKREF1 conclusions. A key aspect of the meeting was to allow for discussions in order to build a shared understanding of the strengths and weakness of the current framework and of the new framework emerging from WKREF1.
Thesis
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In 2012, ICES set out a tier-based system to define the Management Plan (MP) for a specific stock, based on the data available (ICES, 2012). Due to the distinctive life history (Holden, 1974 & 1977; Camhi et al., 1998) and the high number of data-limited stocks (ICES, 2019a), that characterise elasmobranchs in the North-East Atlantic, this paper aims to investigate if the current data-limited ICES MP is effective compared to feasible alternatives. This was done using the North Sea Raja clavata stock. A data-limited Management Strategy Evaluation (MSE) framework was used to simulate the stock under 34 MPs, this was tested under 2 recruitment models and 3 observational scenarios. Currently, an index of vulnerable abundance is used to calculate the Harvest Control Rule for the ICES MP, the MSE simulation conducted, suggested that by switching to an index of spawning abundance, the yields could be improved with minimal increase in conservation risk to the stock. A future alternative could be the MP based on a Delay-Difference model; however, this would require fine-tuning. Sensitivity analysis suggested error in the Index and the risk of hyperstability to the index were to areas to ensure the reliability of data in the future.
Article
International fisheries organisations are moving away from reactionary management to proactive harvest strategies management. However, unresolved discussions on allocation complicate the transition away from the status quo, with member states unable to assess just how big their slice of the pie will be. The question is therefore posed: Can harvest strategies (or management procedures) be adopted without first agreeing on an allocation process? This paper investigates this question and presents an argument that even without an agreed allocation process, there are significant benefits to be gained in the adoption of a harvest strategy for stock management, including by facilitating allocation discussions since future total catches will be more predictable.
Article
A major uncertainty in stock assessment is the difference between models and reality. The validation of model prediction is difficult, however, as fish stocks can rarely be observed and counted. We therefore show how hindcasting and model-free validation can be used to evaluate multiple measures of prediction skill. In a hindcast a model is fitted to the first part of a time series and then projected over the period omitted in the original fit. Prediction skill can then be evaluated by comparing the predictions from the projection with the observations. We show that uncertainty increased when different datasets and hypotheses were considered, especially as time-series of model-derived parameters were sensitive to model assumptions. Using hindcasting and model-free validation to evaluate prediction skill is an objective way to evaluate risk, i.e., to identify the uncertainties that matter. A hindcast is also a pragmatic alternative to hindsight, without the associated risks. While the use of multiple measures helps in evaluating prediction skill and to focus research onto the data and the processes that generated them.
Article
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Rademeyer, R. A., Plagányi, É. E., and Butterworth, D. S. 2007. Tips and tricks in designing management procedures. – ICES Journal of Marine Science, 64: 618–625. Management procedures (MPs) are becoming widely used in fisheries management, but guidelines to assist in their construction, evaluation, and implementation are few. We provide simple guidelines by drawing on experience from developing and applying MPs in southern Africa and internationally. Suggestions are provided on how to choose between candidate MPs and on key trade-offs in selecting between data-based (empirical) and model-based formulations. Assistance is also provided in dealing with different sources of uncertainty, such as deciding which operating models should be included in a reference set used for primary simulation testing and tuning (in contrast to robustness or sensitivity tests), and on how weights for the associated alternative hypotheses are most practically assigned. Finally, some guidelines are given for presenting the results effectively, which is one of the key challenges of a successful implementation process.
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Punt, A. E. and Donovan, G. P. 2007. Developing management procedures that are robust to uncertainty: lessons from the International Whaling Commission. – ICES Journal of Marine Science, 64: 603–612. Traditionally, fisheries management advice has been based on stock assessments that considered merely the “best” set of assumptions while uncertainty arising only from observation and process error was quantified, if considered at all. Unfortunately, uncertainty attributable to lack of understanding of the true underlying system and to ineffective implementation may dominate the sources of error that must be accounted for if management is to be successful. The management procedure approach is advocated as the appropriate way to develop management advice for renewable resources. This approach, pioneered by the International Whaling Commission (IWC) Scientific Committee, takes politically agreed management objectives and incorporates all scientific aspects of management including data collection and analysis, development of robust harvest control laws or effort regulations, and monitoring. A primary feature is that uncertainty (including that arising from sources conventionally ignored) is taken into account explicitly through population simulations for a variety of scenarios. The nature of the management procedures developed for commercial and aboriginal subsistence whaling and the processes by which they have been developed is highlighted. We also identify lessons that have been learned from two decades of IWC experience and suggest how these can be applied to other fishery situations.
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The first standardized, global assessment of these fishes, using Red List criteria, reveals threatened species needing protection.
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Serious concerns have been raised about the ecological effects of industrialized fishing, spurring a United Nations resolution on restoring fisheries and marine ecosystems to healthy levels. However, a prerequisite for restoration is a general understanding of the composition and abundance of unexploited fish communities, relative to contemporary ones. We constructed trajectories of community biomass and composition of large predatory fishes in four continental shelf and nine oceanic systems, using all available data from the beginning of exploitation. Industrialized fisheries typically reduced community biomass by 80% within 15 years of exploitation. Compensatory increases in fast-growing species were observed, but often reversed within a decade. Using a meta-analytic approach, we estimate that large predatory fish biomass today is only about 10% of pre-industrial levels. We conclude that declines of large predators in coastal regions have extended throughout the global ocean, with potentially serious consequences for ecosystems. Our analysis suggests that management based on recent data alone may be misleading, and provides minimum estimates for unexploited communities, which could serve as the 'missing baseline' needed for future restoration efforts.
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Extends earlier simulation studies on management procedures by examining the performance of the revised procedure (RMP) with biased estimates of absolute abundance. This leads to a failure in achieving management goals. Treating the absolute abundance data as an index of relative abundance overcomes this problem without leading to the problem which arises in the catch-effort case of failing to realise the potential of the stocks. A preliminary investigation is made of a modification to the RMP which adjusts the catch limits according to the uncertainty in parameter estimates. -from Author
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We present a process-based approach to estimate residency and behavior from uncertain and temporally correlated movement data collected with electronic tags. The estimation problem is formulated as a hidden Markov model (HMM) on a spatial grid in continuous time, which allows straightforward implementation of barriers to movement. Using the grid to explicitly resolve space, location estimation can be supplemented by or based entirely on environmental data (e.g. temperature, daylight). The HMM method can therefore analyze any type of electronic tag data. The HMM computes the joint posterior probability distribution of location and behavior at each point in time. With this, the behavioral state of the animal can be associated to regions in space, thus revealing migration corridors and residence areas. We demonstrate the inferential potential of the method by analyzing satellite-linked archival tag data from a southern bluefin tuna Thunnus maccoyii where longitudinal coordinates inferred from daylight are supplemented by latitudinal information in recorded sea surface temperatures.
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Fisheries management is characterized by multiple and conflicting objectives, multiple stakeholders with divergent interests and high levels of uncertainty about the dynamics of the resources being managed. This conjunction of issues can result in high levels of contention and poor outcomes in the management process. Management strategy evaluation (MSE) can assist in the resolution of these issues. MSE involves assessing the consequences of a range of management options and laying bare the trade-offs in performance across a range of management objectives. Key steps in the approach involve turning broad objectives into specific and quantifiable performance indicators, identifying and incorporating key uncertainties in the evaluation, and communicating the results effectively to client groups and decision-makers. At a technical level, the framework facilitates dealing with multiple objectives and uncertainties in prediction. At the implementation level, it fails if it cannot accommodate effective stakeholder participation and acceptance. MSE shares many features with approaches such as adaptive management and development of management procedures. The principles for implementing the MSE approach are reviewed and practical aspects of its implementation under the Australian Fisheries Management Authority (AFMA) partnership model to fisheries management are discussed. The model stresses stakeholder involvement in all key areas of fisheries management, from stock assessment and setting research priorities, to enforcement and decision-making. Stakeholder involvement, including industry, science, and conservation, extends from membership of the AFMA Board, through Management Advisory Committees to Fisheries Assessment Groups. The benefits and limitations of the AFMA partnership approach are reviewed, both for MSE, and, in a wider sense, in the development of an effective fisheries management system.
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Suspected historic changes in juvenile southern bluefin tuna Thunnus maccoyii growth rates were investigated using otolith increment width data. Four hundred and ninety otoliths were selected from fish estimated to be between 1 and 41 years-old. The distance between the first five annuli were measured on the otoliths, giving estimates of otolith growth for age classes 1+ to 4+ years for fish spawned from the early 1960s to mid 1990s. The data showed that growth rates of juveniles (age 1+ and 2+ years) started to increase at around 1979–1980, and that growth continued to increase throughout the 1980s and early 1990s. Lee’s phenomenon was not observed in the data. Correlation tests did not reveal clear relationships between annual otolith growth and regional environmental variables such as sea surface temperature or Southern Oscillation Index. The increase in otolith growth, however, was consistent with juvenile growth estimates obtained from other sources, and correlated with large-scale trends in population size and environmental conditions.
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The abundance of bluefin tuna, Thunnus thynnus, in the east Atlantic and Mediterranean has declined in recent decades. The International Commission for the Conservation of Atlantic Tunas (ICCAT), the regional bluefin tuna management authority, has developed a plan to promote recovery by 2022, while still permitting fishing to continue during the period 2008–2010. Here we predict that the adult population in 2011 will likely be 75% lower relative to 2005 and that quotas in some intervening years will allow the fishery to capture legally all of the adult fish. Population demographics (proportion of older fish and repeat spawners in population) indicate that buffering capacity against years of poor reproduction has been reduced. This population is at risk of collapse (90% decline in adult biomass within three generations, the criterion used by the IUCN for defining populations as Critically Endangered), even under the currently agreed recovery plan, unless new conservation measures are implemented in the next few years.
Article
Fisheries management is conducted to achieve sustainable use of fishery resources, mainly through regulation of fishing activities. For almost a decade, the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) struggled to reach agreement on a total allowable catch (TAC) for southern bluefin tuna (SBT) because of stock assessment uncertainties. To address this, in 2002 the CCSBT commenced development of a management procedure (MP), a pre-agreed set of rules to determine how the TAC will be adjusted as new monitoring data become available. The CCSBT Scientific Committee tested various candidate MPs using operating models which simulate fish population and fishery dynamics as well as incorporate process, observation, and model uncertainties. Candidate MPs were evaluated using performance measures related to the following management objectives: maximize catches, avoid stock collapse, and minimize interannual catch variation. Of the MPs explored, some relied solely on empirical data [i.e., adjusted TAC based on catch per unit effort (CPUE) trends], whereas others were more complicated, based on population models. In 2005, the CCSBT adopted a model-based MP that realized a moderate catch with low variability and avoided stock collapse. This MP struck a compromise between the risk-prone and risk-averse standpoints of the different stakeholders. However, despite this concerted scientific effort, the MP was not implemented because, shortly after its adoption, it became evident that historical catches may have been substantially underreported. This complication necessitates returning to near the beginning of the development process. MP approaches have various advantages and challenges to be explored further. However, it is essential to lessen human-introduced uncertainty (such as catch misreporting) by enhanced enforcement, and to increase management robustness to biological uncertainties by implementing MPs.
Article
Southern Bluefin Tuna (SBT) is a depleted stock with a rebuilding target and timeframe defined by the responsible management body (CCSBT). All recent stock assessments have found that the stock is depleted but large differences exist in estimates of recovery probabilities under current catches. In 1996, CCSBT adopted a set of principles and a process for considering experimental fishing, which are fundamentally consistent with an actively adaptive management policy. Substantial efforts to develop a program in line with these principles did not succeed, partially due to the lack of a decision-making framework. In 1998 and 1999, Japan conducted unilateral experimental fishing arguing that the additional substantial catches could reduce uncertainty in stock assessments and thus were justified. This led to international legal proceedings under UNCLOS, in which preliminary measures were issued preventing further unilateral experimental fishing (these were later rescinded when an UNCLOS arbitral tribunal found that it lacked jurisdiction in the dispute). This decision has been cited as a possible manifestation of industry's “worst fear with the implementation of the precautionary approach”. This paper examines the SBT dispute in relationship to adaptive management and the precautionary approach, Results of recent stock assessments indicate that the Japanese experimental fishing, even if successful, was unlikely to resolve the disparity in estimates of the recovery probabilities or provide an improved basis for management decision making. In this context, it is the absence of a management framework, rather than a fundamental problem with adaptive management, that challenges the compatibility of these experimental fishing catches and the precautionary approach. The real issue in the SBT situation is the standards and burden of proof required if experimental fishing is to be considered.
Article
Regional fisheries management organizations (RFMOs) collectively manage the largest distinct area of the world, the high seas, but their effectiveness in conserving the fish stocks therein has been questioned lately, as many stocks have declined. This study quantitatively assesses the effectiveness of the world's 18 RFMOs, based on a two-tiered approach, concentrating first on their performance ‘on paper’ and secondly, in practice. The former was determined by assessing how well RFMOs scored against 26 criteria that together reflect current RFMO best practices. The latter assessment referenced the current state of the stocks RFMOs manage, through biomass and fishing mortality reference points and biomass trends through time. Results show low performance of RFMOs for both assessments, i.e., average scores of 57% and 49%, respectively. The latter result is emphasized by findings that reflect two-thirds of stocks fished on the high seas and under RFMO management are either depleted or overexploited. Findings also indicate that there is no connection between the two sets of scores, suggesting a disparity between organization intent and action.
Article
Otolith-based age estimates were obtained for 2769 southern bluefin tuna (SBT) (Thunnus maccoyii) caught on feeding grounds in the southern oceans and their spawning ground in the north-east Indian Ocean between 1985 and 1998. Ages ranged from 0 to 41 years, and males were on average larger at age than females after age 6 for fish sampled in the southern oceans. This sexual dimorphism in growth contributed to the sex ratio being biased toward males for length classes ≥170 cm FL. The estimated age composition of catches, derived from age-length keys applied to length frequency data, showed clear differences between fisheries and fishing grounds that are consistent with seasonal and ontogenetic changes in migration patterns. Specific information that can be gained on the distribution and migration of juveniles from their relative abundance in catches is limited because of unknown targeting or discarding practices on some fishing grounds. However, the occurrence of 2–4-year-old SBT on opposite sides of the Indian Ocean during the austral summer confirms that juveniles are not restricted to the southern coastal waters of Australia, and that a divergent migration path must exist possibly near the southern west coast of Australia. During the winter months, SBT aged 2–4 years were caught on all fishing grounds south of the spawning ground, confirming that they are capable of extensive migrations. By age 5, SBT were rarely caught north of about 35°S, except in waters adjacent to Australia's west coast where adults were caught migrating to/from the spawning ground. The commercial catch of SBT in the southern oceans was dominated by juveniles and sub-adults on most fishing grounds examined. Off north-east New Zealand, however, the majority of fish caught were of spawning age (61% were >10-year old) suggesting that the Tasman Sea may form the eastern boundary for juvenile migration. SBT caught on the spawning ground ranged in age from 8 to 34 years with the majority being between 15- and 25-years old.
Article
Butterworth, D. S. 2007. Why a management procedure approach? Some positives and negatives. – ICES Journal of Marine Science, 64: 613–617. The origin of the management procedure (MP) approach (sometimes termed management strategy evaluation), with its simulation testing of feedback-control algorithms as a necessary and structured basis for dealing with the inevitable uncertainties associated with fisheries assessments, is briefly reviewed. Also discussed are the advantages that overcome some of the difficulties of the “traditional” approach of coupling an annual “best” assessment to some harvest control rule, such as a failure to consider longer-term trade-offs properly. The MP approach does, however, also have disadvantages, such as the length of time typically required for its development and an argued inflexibility after implementation. Solutions that have been developed to overcome some of these difficulties are discussed.
Article
A simple two-stage biomass random effects population dynamics model is presented for carrying out fish stock assessments based on survey indices using no commercial catch information. Recruitment and biomass growth are modelled as random effects, reducing the number of model parameters while maintaining model flexibility. No assumptions regarding natural mortality rates are required. The performance of the method was evaluated using simulated data with emphasis on identifying parameter redundancy, which showed that the variance of the biomass growth random effect might only be estimable if large (> 0.2). The full and two nested models were fitted to European anchovy (Engraulis encrasicolus) in the Bay of Biscay using two survey series. The best-fitting model had fixed biomass growth and random recruitment following a lognormal distribution.
Greenland halibut MSE results for updated SCAA reference case and robustness test operating models
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