scholarly journals Data-poor stock assessment of fish stocks co-exploited by commercial and recreational fisheries: applications to pike (Esox lucius) in the western Baltic Sea

2021 ◽  
Author(s):  
Rob van Gemert ◽  
Dieter Koemle ◽  
Helmut Winkler ◽  
Robert Arlinghaus
Keyword(s):  
Stock Assessment ◽  
Recreational Fishing ◽  
Recreational Fisheries ◽  
Fish Stocks ◽  
Explanatory Variables ◽  
Recreational Angling ◽  
Mixed Use ◽  
Stock Assessments ◽  
The Status

AbstractInformation on catch and effort of recreational angling in mixed-use fisheries (co-exploited by commercial and recreational fishers) is often scarce, preventing the application of data-rich stock assessments typically performed for industrialized commercial fisheries. Here, we show how data-poor stock assessment methods developed for marine fisheries, particularly a class of models labelled as “catch-only” models (COMs), offer a possible solution. As a case study, we use COMs to assess a northern pike stock around the German Baltic island of Rügen. We fit multiple COMs to a time-series of total pike removals, and use their outputs as explanatory variables in superensemble models. We conclude that the stock is fully exploited and currently declining. Our study highlights the potential for using COMs to determine status of previously-unassessed coastal and freshwater stocks facing recreational fishing pressure, and demonstrates how incorporating recreational removals is crucial for achieving reliable insights into the status of mixed-use stocks.

scholarly journals Modeling Discards in Stock Assessments: Red Grouper Epinephelus morio in the U.S. Gulf of Mexico

Fishes ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 7
Author(s):  
Kyle W. Shertzer ◽  
Erik H. Williams ◽  
Skyler R. Sagarese
Keyword(s):  
Gulf Of Mexico ◽  
Stock Assessment ◽  
Time Varying ◽  
Discard Mortality ◽  
Stock Assessments ◽  
Epinephelus Morio ◽  
Red Grouper ◽  
Management Advice ◽  
The U.S

To be as accurate as possible, stock assessments should account for discard mortality in fisheries if it occurs. Three common approaches to modeling discards in assessments are to lump dead discards with landings, treat dead discards as their own fleet, or link them conversely with landings through use of a retention function. The first approach (lumping) implicitly assumes that the selectivity of landings applies also to discards. In many cases, that assumption is false, for example, if discards comprise smaller fish than do landings. The latter two approaches avoid the assumption by modeling discards explicitly with their own selectivity pattern. Here, we examine these approaches to modeling discards. Using a simulation study, we demonstrate that the two approaches to modeling discards explicitly can provide identical results under both static and time-varying conditions. Then, using a stock assessment case study of red grouper Epinephelus morio in the U.S. Gulf of Mexico, we demonstrate that in practice the approaches to modeling discards can provide different outcomes, with implications for the resultant management advice. We conclude by comparing and contrasting the different approaches, calling for more research to elucidate which approach is most suitable under various sources of error typically encountered in discard data.

scholarly journals Reflections on the success of traditional fisheries management

2014 ◽  
Vol 71 (5) ◽  
pp. 1040-1046 ◽  
Author(s):  
Ray Hilborn ◽  
Daniel Ovando
Keyword(s):  
Fisheries Management ◽  
Statistical Models ◽  
Management Systems ◽  
Marine Resources ◽  
Fish Stocks ◽  
Stock Assessments ◽  
The World ◽  
The Status ◽  
Management Approaches ◽  
Precautionary Management

Abstract The argument persists that the continued overexploitation by many fisheries around the world is evidence that current approaches to fisheries management are failing, and that more precautionary management approaches are needed. We review the available estimates of the status of fish stocks from three sources: the FAO's “State of Marine Resources”, a database on scientific stock assessments, and recent estimates from statistical models designed to determine the status of unassessed fish stocks. The two key results are (i) that stocks that are scientifically assessed are in better shape and indeed are not typically declining but rebuilding, and (ii) that large stocks appear to be in better shape than small stocks. These results support the view that stocks that are managed are improving, while stocks that are not managed are not. Large stocks receive far more management attention than small stocks in jurisdictions that have active fisheries management systems, and most unassessed stocks are simply not managed. We assert that fisheries management as currently practised can (and often does) lead to sustainable fisheries, and what is needed is to actively manage the unassessed fisheries of the world. More precautionary management is not necessarily needed to ensure the sustainability of managed fisheries.

Recreational angling intensity correlates with alteration of vulnerability to fishing in a carnivorous coastal fish species

2015 ◽  
Vol 72 (2) ◽  
pp. 217-225 ◽  
Author(s):  
Josep Alós ◽  
Miquel Palmer ◽  
Pedro Trías ◽  
Carlos Díaz-Gil ◽  
Robert Arlinghaus
Keyword(s):  
Fish Species ◽  
Empirical Support ◽  
Coastal Fish ◽  
Fish Stocks ◽  
Recreational Angling ◽  
The Status ◽  
Catch Rates ◽  
Multiple Species ◽  
Study Species

Increased timidity is a behavioral response to exploitation caused by a combination of learning and fisheries-induced selection favoring shy fish. In our study, the potential for angling-induced change in fish behavior was examined in two marine coastal fishes exploited by boat recreational fishing in the Mediterranean (Mallorca, Spain). It was expected that the mean vulnerability to capture of surviving individuals would differ across a gradient of previous exposure to recreational angling and that this effect would be present in multiple species. The prediction received partial empirical support. Recreational angling intensity was correlated with enhanced gear-avoidance behavior in only one of the two study species, the carnivorous painted comber (Serranus scriba). By contrast, the omnivorous fish species in our study, the annular seabream (Diplodus annularis), did not differ in its behavior towards hooks in exploited compared with unexploited sites. These results suggest that recreational angling may contribute to patterns of hyperdepletion in catch rates because of increased timidity and associated reduced vulnerability to fishing gear in some exploited species. Such effects would lead to erroneous interpretations about the status of the fish stocks when assessed by fishery-dependent data and would negatively affect catch rates and quality of the fishery in the affected species.

scholarly journals Length-Based Stock Assessment of Smith's Barb, Puntioplites proctozystron (Bleeker, 1865) (Cyprinidae) and Asian Redtail Catfish, Hemibagrus nemurus, (Valenciennes, 1840), (Bagridae) in a Multipurpose Reservoir in Thailand

2021 ◽  
Vol 34 (2) ◽  
Author(s):  
KAJITPAN CHARERNNATE ◽  
PAVAROT NORANARTTRAGOON ◽  
TUANTONG JUTAGATE ◽  
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Relative Yield ◽  
Mesh Size ◽  
Fish Stock ◽  
Fish Stocks ◽  
The Status ◽  
Curvature Parameter ◽  
Spawning Potential Ratio ◽  
Fish Stock Assessment

Catches from inland fisheries in Thailand are about 200,000 tonnes annually and plays an important role in food security and subsidiary income. However, fish stocks are seldom assessed because of the lack of catch and effort data. In this study, two fish stock assessment models, viz., relative yield per recruit and length-based spawning potential ratio, were used to evaluate the status of two species as well as to highlight their applications to datalimited situation in Thailand. The study was conducted at Kangkrajan Reservoir, Thailand, for two targeted species, viz., Smith's barb, Puntioplites proctozystron (Bleeker, 1865) and Asian redtail catfish, Hemibagrus nemurus (Valenciennes, 1840) using length frequency data. The data were collected throughout 2019. Both species showed isometric growth. Von Bertalanffy growth parameters were estimated. Asymptotic length, curvature parameter and theoretical age at length zero were 36.2 cm TL, 0.39 yr-1 and -0.28 yr for P. proctozystron, respectively, and 63.2 cm TL, 0.37 yr-1 and -0.32 yr for H. nemurus. The exploitation rates reveal that both species are slightly overfished. Sizes at 50 % maturity and 50 % selectivities were 17.8 and 23.5 cm TL for P. proctozystron, respectively, and 15.6 and 20.8 cm TL for H. nemurus. Considering both parameters, the size at first capture to sustain the fisheries of P. proctozystron and H. nemurus should be >18 cm and >30 cm, respectively, which can be achieved by mesh-size regulations.

The Angler in the Environment: Social, Economic, Biological, and Ethical Dimensions

2011 ◽  
Keyword(s):  
Fisheries Management ◽  
Animal Rights ◽  
Research Priorities ◽  
Human Dimensions ◽  
Fish Stock ◽  
Recreational Fishing ◽  
Commercial Fishing ◽  
Recreational Fisheries ◽  
Recreational Angling ◽  
Fisheries Sustainability

<i>Abstract</i> .—There is a need to better understand the perspectives of various recreational fishing stakeholder groups regarding key issues related to fisheries sustainability. To provide a first snapshot and to inform future human dimension studies in this area, we distributed a Web-based open-access survey to fisheries researchers, fisheries managers, and anglers in North America. Attitudes of these respondents towards issues such as overharvest, impacts of catch and release, recreational fisheries management, and research priorities for the future were assessed. We found similar opinions and perspectives by the responding recreational anglers, managers, and researchers on a number of issues, such as the perceived impact of commercial fishing contributing to fish stock declines, the perceived importance of using and promoting gear that minimizes stress and injury to individual fish when fish are to be released, and the belief that conflicts among stakeholders is growing as is the global anti-fishing movement based on animal rights thinking. Differences among responding groups included that researchers tended to be more concerned than anglers and managers with the potential of recreational angling contributing to fish stock declines. Responding anglers were also less content with their involvement in the fisheries management process than were responding managers and researchers, and these anglers also indicated a greater desire for more human dimensions research on understanding angler attitudes and behavior than was evident for responding managers and researchers. This preliminary survey revealed some variation in attitudes among recreational fisheries stakeholders. However, due to lack of random sampling, the study results cannot be extrapolated to the population level. We nevertheless conclude that improved communication and better understanding about the different perspectives among fisheries researchers, managers, and anglers and intrasectorally among different angling groups are needed, particularly when addressing contentious issues of relevance for the entire recreational fishing sector.

Overcoming long Bayesian run times in integrated fisheries stock assessments

2019 ◽  
Vol 76 (6) ◽  
pp. 1477-1488 ◽  
Author(s):  
Cole C Monnahan ◽  
Trevor A Branch ◽  
James T Thorson ◽  
Ian J Stewart ◽  
Cody S Szuwalski
Keyword(s):  
Parallel Computation ◽  
Stock Assessment ◽  
Likelihood Estimation ◽  
R Package ◽  
Complex Model ◽  
Bayesian Algorithm ◽  
Fish Stocks ◽  
Model Builder ◽  
Long Run ◽  
Stock Assessments

Abstract Bayesian inference is an appealing alternative to maximum likelihood estimation, but estimation can be prohibitively long for integrated fisheries stock assessments. Here, we investigated potential causes of long run times including high dimensionality, complex model structure, and inefficient Bayesian algorithms for four US assessments written in AD Model Builder (ADMB), both custom built and Stock Synthesis models. The biggest culprit for long run times was overparameterization and they were reduced from months to days by adding priors and turning off estimation for poorly-informed parameters (i.e. regularization), especially for selectivity parameters. Thus, regularization is a necessary step in converting assessments from frequentist to Bayesian frameworks. We also tested the usefulness of the no-U-turn sampler (NUTS), a Bayesian algorithm recently added to ADMB, and the R package adnuts that allows for easy implementation of NUTS and parallel computation. These additions further reduced run times and better sampled posterior distributions than existing Bayesian algorithms in ADMB, and for both of these reasons we recommend using NUTS for inference. Between regularization, a faster algorithm, and parallel computation, we expect models to run 50–50 000 times faster for most current stock assessment models, opening the door to routine usage of Bayesian methods for management of fish stocks.

Comparative performance of data-poor CMSY and data-moderate SPiCT stock assessment methods when applied to data-rich, real-world stocks

2020 ◽  
Author(s):  
Paul Bouch ◽  
Cóilín Minto ◽  
Dave G Reid
Keyword(s):  
Stock Assessment ◽  
Assessment Methods ◽  
Production Model ◽  
Fishing Mortality ◽  
Comparative Performance ◽  
Fish Stocks ◽  
Surplus Production ◽  
Stock Biomass ◽  
Surplus Production Model ◽  
The Status

Abstract All fish stocks should be managed sustainably, yet for the majority of stocks, data are often limited and different stock assessment methods are required. Two popular and widely used methods are Catch-MSY (CMSY) and Surplus Production Model in Continuous Time (SPiCT). We apply these methods to 17 data-rich stocks and compare the status estimates to the accepted International Council for the Exploration of the Sea (ICES) age-based assessments. Comparison statistics and receiver operator analysis showed that both methods often differed considerably from the ICES assessment, with CMSY showing a tendency to overestimate relative fishing mortality and underestimate relative stock biomass, whilst SPiCT showed the opposite. CMSY assessments were poor when the default depletion prior ranges differed from the ICES assessments, particularly towards the end of the time series, where some stocks showed signs of recovery. SPiCT assessments showed better correlation with the ICES assessment but often failed to correctly estimate the scale of either F/FMSY of B/BMSY, with the indices lacking the contrast to be informative about catchability and either the intrinsic growth rate or carrying capacity. Results highlight the importance of understanding model tendencies relative to data-rich approaches and warrant caution when adopting these models.

scholarly journals A multi-stock harvest control rule based on “pretty good yield” ranges to support mixed-fisheries management

2019 ◽  
Author(s):  
Dorleta Garcia ◽  
Paul J Dolder ◽  
Ane Iriondo ◽  
Claire Moore ◽  
Raúl Prellezo ◽  
...  
Keyword(s):  
Fisheries Management ◽  
Stock Assessment ◽  
Holistic Approach ◽  
Fishing Mortality ◽  
Fish Stocks ◽  
Control Rule ◽  
Harvest Control Rule ◽  
The Impact ◽  
Ecosystem Based Fisheries Management

Abstract Advice for commercially exploited fish stocks is usually given on a stock-by-stock basis. In light of the ecosystem-based fisheries management, the need to move towards a holistic approach has been largely acknowledged. In addition, the discard bans in some countries requires consistent catch advice among stocks to mitigate choke species limiting fisheries activity. In this context, in 2015, the European Commission proposed the use of fishing mortality ranges around fishing mortality targets to give flexibility to the catch advice system and improve the use of fishing opportunities in mixed-fisheries. We present a multi-stock harvest control rule (HCR) that uses single stock assessment results and fishing mortality ranges to generate a consistent catch advice among stocks. We tested the performance of the HCR in two different case studies. An artificial case study with three stocks exploited simultaneously by a single fleet and the demersal mixed-fishery operating in Bay of Biscay and Celtic Sea. The HCR produced consistent catch advice among stocks when there was only a single fleet exploiting them. Even more, the HCR removed the impact of the discard ban. However, in a multi-fleet framework the performance of the HCR varied depending on the characteristics of the fleets.

scholarly journals The efficiency assessment of food safety in China’s agriculture: a case study of the rice sector

2008 ◽  
Vol 54 (No. 11) ◽  
pp. 521-528 ◽  
Author(s):  
Zhang Tao
Keyword(s):  
Food Safety ◽  
Stochastic Frontier ◽  
Analytical Framework ◽  
Environmental Efficiency ◽  
Negative Effects ◽  
Managerial Efficiency ◽  
Explanatory Variables ◽  
The Status ◽  
The Impact

Rice is the main food in China’s home consumption and plays an important role in its food security. But, how is the status of food safety and environmental efficiency in China’s agriculture? Obviously, an incorrect manner of pesticide application will hold negative effects on human health and environment. In this article, we develop an analytical framework based on the Luenberger DEA method to calculate the output technical efficiency and input environmental efficiency simultaneously. In the second-stage analysis, the stochastic frontier model is used to estimate the impact of explanatory variables and managerial efficiency on efficiency. We apply the methodology in the empirical case study of China’s rice production for measuring the food safety performance of China’s rice sector.

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