Trade-offs in fishery management objectives when allowing catch limit carry-over between years

2020 ◽  
Author(s):  
John R Wiedenmann ◽  
Daniel S Holland
Keyword(s):  
Life Histories ◽  
Fishery Management ◽  
Risk Measures ◽  
Stock Assessment ◽  
Total Allowable Catch ◽  
Management Objectives ◽  
Strategy Evaluation ◽  
Trade Offs ◽  
Stock Biomass ◽  
Carry Over

Abstract Fisheries managed with explicit annual catch limits often have realized catches below the total allowable catch. Carry-over provisions allowing aggregate or individual carry-forward of catch underages are included in many fishery management systems, but the ramifications of these provisions on different fishery management objectives such as average catch, variability in catch, and probability and degree of overfishing are not well understood. We developed a management strategy evaluation simulation to explore performance of alternative carry-over policies assuming different life histories and under different causes of catch underages. We evaluated the impacts of the carry-overs across common management objectives to understand the trade-offs associated with different amounts of allowable carry-over. We find that carry-overs can increase yield to the fishery but can also increase the risks of overfishing, low stock biomass, low catch, and the interannual variability in catch. All of these risk measures increase with the amount of carry-over allowed in most cases, but for cases of low stock productivity or positively biased stock assessment estimates, larger carry-over allowances resulted in similar or lower yield compared to smaller allowances. The analysis suggests that some benefits of carry-over can be maintained and risks can be limited by restricting the maximum carry-over allowed.

Lessons learned from data-limited evaluations of data-rich reef fish species in the Gulf of Mexico: implications for providing fisheries management advice for data-poor stocks

2019 ◽  
Vol 76 (9) ◽  
pp. 1624-1639 ◽  
Author(s):  
Skyler R. Sagarese ◽  
William J. Harford ◽  
John F. Walter ◽  
Meaghan D. Bryan ◽  
J. Jeffery Isely ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Reef Fish ◽  
Fish Species ◽  
Stock Assessment ◽  
Lessons Learned ◽  
Management Objectives ◽  
Trade Offs ◽  
Data Limitations ◽  
Management Procedures ◽  
Reef Fish Species

Specifying annual catch limits for artisanal fisheries, low economic value stocks, or bycatch species is problematic due to data limitations. Many empirical management procedures (MPs) have been developed that provide catch advice based on achieving a stable catch or a historical target (i.e., instead of maximum sustainable yield). However, a thorough comparison of derived yield streams between empirical MPs and stock assessment models has not been explored. We first evaluate trade-offs in conservation and yield metrics for data-limited approaches through management strategy evaluation (MSE) of seven data-rich reef fish species in the Gulf of Mexico. We then apply data-limited approaches for each species and compare how catch advice differs from current age-based assessment models. MSEs identified empirical MPs (e.g., using relative abundance) as a compromise between data requirements and the ability to consistently achieve management objectives (e.g., prevent overfishing). Catch advice differed greatly among data-limited approaches and current assessments, likely due to data inputs and assumptions. Adaptive MPs become clearly viable options that can achieve management objectives while incorporating auxiliary data beyond catch-only approaches.

scholarly journals Time-varying natural mortality in fisheries stock assessment models: identifying a default approach

2014 ◽  
Vol 72 (1) ◽  
pp. 137-150 ◽  
Author(s):  
Kelli F. Johnson ◽  
Cole C. Monnahan ◽  
Carey R. McGilliard ◽  
Katyana A. Vert-pre ◽  
Sean C. Anderson ◽  
...  
Keyword(s):  
Stock Assessment ◽  
Assessment Method ◽  
Reference Points ◽  
Natural Mortality ◽  
Time Varying ◽  
Fishing Mortality ◽  
Total Allowable Catch ◽  
Robust Approach ◽  
Structured Population Models ◽  
Trade Offs

Abstract A typical assumption used in most fishery stock assessments is that natural mortality (M) is constant across time and age. However, M is rarely constant in reality as a result of the combined impacts of exploitation history, predation, environmental factors, and physiological trade-offs. Misspecification or poor estimation of M can lead to bias in quantities estimated using stock assessment methods, potentially resulting in biased estimates of fishery reference points and catch limits, with the magnitude of bias being influenced by life history and trends in fishing mortality. Monte Carlo simulations were used to evaluate the ability of statistical age-structured population models to estimate spawning-stock biomass, fishing mortality, and total allowable catch when the true M was age-invariant, but time-varying. Configurations of the stock assessment method, implemented in Stock Synthesis, included a single age- and time-invariant M parameter, specified at one of the three levels (high, medium, and low) or an estimated M. The min–max (i.e. most robust) approach to specifying M when it is thought to vary across time was to estimate M. The least robust approach for most scenarios examined was to fix M at a high value, suggesting that the consequences of misspecifying M are asymmetric.

scholarly journals Designing tools to evaluate fishery management strategies: can the scientific community deliver?

2007 ◽  
Vol 64 (6) ◽  
pp. 1077-1084 ◽  
Author(s):  
Jon T. Schnute ◽  
Mark N. Maunder ◽  
James N. Ianelli
Keyword(s):  
Programming Languages ◽  
Scientific Community ◽  
Fishery Management ◽  
Stock Assessment ◽  
Management Strategies ◽  
Academic Disciplines ◽  
Strategy Evaluation ◽  
Management Procedures ◽  
Human Skills ◽  
Testing Management

Abstract Schnute, J. T., Maunder, M. N., and Ianelli, J. N. 2007. Designing tools to evaluate fishery management strategies: can the scientific community deliver? – ICES Journal of Marine Science, 64: 1077–1084. Techniques for quantitative fishery management have evolved rapidly during a period when computers, programming languages, and computational algorithms have also changed dramatically. Despite these advances, many stock assessment methods remain untested. A process of management strategy evaluation (MSE) could potentially rectify this problem, but it would require a framework in which to conduct systematic tests. We survey the tools currently used for stock assessments and discuss the development of new standards for testing management procedures. A successful project would depend on human skills scattered among various nations, organizations, and academic disciplines. Analogies from civil engineering illustrate the discipline and collaboration required for an effective outcome. If the world community of fishery scientists could design, build, and support such a project, it would revolutionize the theory, teaching, and practice of scientific fishery management.

scholarly journals Ecological Reference Points for Atlantic Menhaden Established Using an Ecosystem Model of Intermediate Complexity

2020 ◽  
Vol 7 ◽  
Author(s):  
David Chagaris ◽  
Katie Drew ◽  
Amy Schueller ◽  
Matt Cieri ◽  
Joana Brito ◽  
...  
Keyword(s):  
Striped Bass ◽  
Fishery Management ◽  
Stock Assessment ◽  
Reference Points ◽  
Atlantic Menhaden ◽  
Assessment Model ◽  
Total Allowable Catch ◽  
Important Species ◽  
Ecosystem Impacts ◽  
Intermediate Complexity

Atlantic menhaden (Brevoortia tyrannus) are an important forage fish for many predators, and they also support the largest commercial fishery by weight on the U.S. East Coast. Menhaden management has been working toward ecological reference points (ERPs) that account for menhaden’s role in the ecosystem. The goal of this work was to develop menhaden ERPs using ecosystem models. An existing Ecopath with Ecosim model of the Northwest Atlantic Continental Shelf (NWACS) was reduced in complexity from 61 to 17 species/functional groups. The new NWACS model of intermediate complexity for ecosystems (NWACS-MICE) serves to link the dynamics of menhaden with key managed predators. Striped bass (Morone saxatilis) were determined to be most sensitive to menhaden harvest and therefore served as an indicator of ecosystem impacts. ERPs were based on the tradeoff relationship between the equilibrium biomass of striped bass and menhaden fishing mortality (F). The ERPs were defined as the menhaden F rates that maintain striped bass at their biomass target and threshold when striped bass are fished at their Ftarget, and all other modeled species were fished at status quo levels. These correspond to an ERP Ftarget of 0.19 and an ERP Fthreshold of 0.57, which are lower than the single species reference points by 30–40%, but higher than current (2017) menhaden F. The ERPs were then fed back into the age-structured stock assessment model projections to provide information on total allowable catch. The ERPs developed in this study were adopted by the Atlantic menhaden Management Board, marking a shift toward ecosystem-based fishery management for this economically and ecologically important species.

Does fisheries science serve the needs of managers of small stocks in developing countries

1997 ◽  
Vol 54 (9) ◽  
pp. 2207-2213 ◽  
Author(s):  
R Mahon
Keyword(s):  
Developing Countries ◽  
Fishery Management ◽  
Stock Assessment ◽  
International Programs ◽  
Total Revenue ◽  
Fisheries Science ◽  
Management Objectives ◽  
Fishery Science ◽  
Methodological Approaches ◽  
Critical Components

Despite the prevalence and socioeconomic importance of small, low total-revenue stocks, predominantly in tropical, developing countries, most of the world's fishery science effort has been devoted to large stocks. Methods for assessing and managing large stocks, though applicable to small ones, are seldom feasible for them. Minimal attention has been paid to approaches that are specifically for small stocks. The tendency for managers of fisheries on small stocks in developing countries to believe that stock assessment is essential for successful fishery management, often leads to disproportionate allocation of resources to stock assessment rather than other critical components of management. This has been reinforced by several agencies that have made stock assessment methods and software available for use in developing countries, while paying little attention to other dimensions of fishery assessment and management. Hence, management efforts for small stocks are often stock assessment driven (SAD), rather than management objective driven (MOD), as they should be. The sequence of actions typical of these two approaches is contrasted. Managers of small stocks in developing countries need international programs that will develop and promote formal methodological approaches with broad emphasis on management objectives and process.

scholarly journals Analysis of Optimal Harvest and Management of Capture Fishery of Lake Ziway, Central Ethiopia

2021 ◽  
Author(s):  
Kindineh Sisay
Keyword(s):  
Public Good ◽  
Fish Species ◽  
Fishery Management ◽  
Management Practices ◽  
Stock Assessment ◽  
Free Access ◽  
Fishing Gear ◽  
Total Allowable Catch ◽  
Individual Transferable Quotas ◽  
Near Future

Abstract Even if there is fluctuation in fish species diversity and relative abundance of the species, Lake Ziway provides numerous environmental and/or ecosystem services. Despite to its importance, the Lake faces numerous threats because of its public good characteristics. Following the exponentially increased demand for fishes and the resource being public good, magnificent number of individuals are participated in capture fisheries in order to secure their livelihood. Free access to the fisheries, illegal fishing gears and environmental degradation are among the main reasons of decline in fish species and degradation of the Lake. From the current stock assessment survey, the study showed decline in biomass of fish over time. These negative trends in the Lake Ziway fisheries and poor water quality led to loss of livelihoods of many households who are directly or indirectly dependent on the Lake. Therefore, management of Lake Ziway fishery becomes very essential to manage the resource efficiently in a way that maximize fishers present and future benefits otherwise, the fish resource will disappear in the near future. Concerning management practices, most of the fishery regulations in this Lake put emphasis on the restriction of fishing gear, but the application of this instrument with its restrictions is almost zero. Moreover, Individual Transferable Quotas (ITQs) foster greater transparency and accountability for the management and enhancement of fishery resources by quota owners. In this regard, since it generates a sense of ownership and its versatility in providing a stable and productive market, ITQs are more effective than gear restrictions and in fact, it has major social benefits by controlling overharvesting. Due to this, to ensure the nutritional and food security of the country currently and in the near future, there is a need to enforce fishing gear restriction and set ITQs. Furthermore, there must be strong effort on studying the current stock of fish, and numbers of legal and illegal fishers to set Individual Transferable Quotas (ITQs) and Total Allowable Catch (TAC) for sustainable fishery management of Lake Ziway.

scholarly journals Multi-Indicator Harvest Strategies for Data-Limited Fisheries: A Practitioner Guide to Learning and Design

2021 ◽  
Vol 8 ◽  
Author(s):  
William J. Harford ◽  
Ricardo Amoroso ◽  
Richard J. Bell ◽  
Matias Caillaux ◽  
Jason Marc Cope ◽  
...  
Keyword(s):  
Fishery Management ◽  
Wide Spectrum ◽  
Critical Evaluation ◽  
World Population ◽  
Fishery Resource ◽  
Strategy Evaluation ◽  
Stock Biomass ◽  
Stock Assessments ◽  
Insight Into ◽  
Indicator Frameworks

As the world population grows, fisheries practitioners will be under increased pressure to address global challenges in data-limited fisheries management. With a focus on addressing localized and case-specific management needs, we provide a practical guide to the design and development of multi-indicator frameworks for fishery management. In a data-limited context, indicators are observations or estimates of the state of the fishery resource that are typically proxies for variables of interest, rather than quantities such as stock biomass estimated from data-rich stock assessments. Indicator frameworks structure the integration and interpretation of indicators to guide tactical fishery decision-making, often when the application of more formal analytical assessments is not feasible, yet where indicators in combination provide insight into stock status. With a focus on multi-indicator frameworks, we describe a pragmatic approach for their development via a set of organizational steps, considering a wide spectrum of types and severity of information limitations. We highlight where multi-indicator frameworks can be insightful and informative in relation to single indicator approaches but also point to potential pitfalls, with emphasis on critical evaluation and detection of performance flaws during the design phase using methods such as management strategy evaluation.

Review of progress in the introduction of management strategy evaluation (MSE) approaches in Australia's South East Fishery

2001 ◽  
Vol 52 (4) ◽  
pp. 719 ◽  
Author(s):  
André E. Punt ◽  
Anthony D. M. Smith ◽  
Gurong Cui
Keyword(s):  
Performance Indicators ◽  
Management Strategy ◽  
Stock Assessment ◽  
Management Strategy Evaluation ◽  
Management Objectives ◽  
Strategy Evaluation ◽  
Simulation Based ◽  
Stock Assessments ◽  
Research Programmes ◽  
Different Levels

The MSE approach provides a simulation-based framework within which harvest strategies, stock assessment methods, performance indicators and research programmes can be compared. This approach has been used in the Australian South East Fishery (SEF) to assess harvest strategies for the over-exploited eastern gemfish resource and to compare different levels of discard monitoring for blue grenadier. The main challenges to use of the MSE approach in the SEF are poorly specified management objectives and the lack of quantitative stock assessments on which to build operating models for many of the species.

Use and abuse of fishery models

2001 ◽  
Vol 58 (1) ◽  
pp. 10-17 ◽  
Author(s):  
Jon T Schnute ◽  
Laura J Richards
Keyword(s):  
World Literature ◽  
Fishery Management ◽  
Stock Assessment ◽  
Management Practice ◽  
Fish Stock ◽  
Fish Stocks ◽  
Creative Thought ◽  
Modeling Process ◽  
Stock Biomass ◽  
Fish Stock Assessment

Recent failures of important fish stocks give mathematical models a poor reputation as tools for fishery management. This paper examines the role of models in fish stock assessment and identifies reasons why they can fail. Starting with laws of arithmetic, models attempt to relate observed data to unknown quantities, such as the stock biomass and abundance. Typically, the number of unknowns greatly exceeds the number of observations, and models must impose hypothetical constraints to give useful estimates. We use the word "fishmetic" (rhymes with arithmetic) to represent uncertainty in the conversion of arithmetic to practical fishery models. Arbitrary assumptions cannot be avoided, even though different choices can greatly influence the outcome of the analysis. We compare the modeling process in fisheries with that in other sciences. World literature also offers useful analogies. Potential reasons for failure suggest possible improvements to the application of fishery models. We recommend that modelers remain skeptical, expand their knowledge base, apply common sense, and implement robust strategies for fishery management. Particularly creative thought must be applied to the problem of translating scientific knowledge into management practice. Comparisons between fish stocks and financial stocks illustrate some possibilities.

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