Chase C. Lamborn, Jan Ohlberger, Timothy E. Walsworth, Peter A. H. Westley, Curry J. Cunningham, Sam Wynsma, Jordan W. Smith
Across Alaska, there have been synchronous declines in the abundance, mean age, and size of Chinook salmon (Oncorhynchus tshawytscha, Salmonidae), a species with immense social and ecological importance. The decline of Chinook salmon, and regulations addressing declines, have drastically impacted people who rely on Alaska's fisheries. Despite their importance, the drivers causing Chinook salmon declines are still not well understood. Therefore, to improve our understanding of the likely drivers of these large‐scale synchronous declines, we synthesised the peer‐reviewed Chinook salmon literature published between 2010 and 2024 using a weight‐of‐evidence approach. We identified 94 variables used to explain the trends in abundance and demographics of Chinook salmon. Each variable's association with trends in Chinook salmon was individually assessed and integrated using a standardised method. Results of this synthesis suggest the drivers for large‐scale synchronous declines have occurred in the North Pacific Ocean. Specifically, we found marine predation, size selective harvest, and pink salmon (Oncorhynchus gorbuscha) abundance are the factors most strongly associated with reduced size and age. Results also suggest ocean productivity–specifically winter sea surface temperature and the North Pacific Gyre Oscillation–are the most frequently identified predictors of regional Chinook salmon abundance. In addition to addressing freshwater factors like adult heat stress and juvenile predation, we suggest research, policy, and management focus on how to better understand and address the interactions between ocean productivity, marine predation, size selective harvest, and pink salmon abundance to improve the condition of Chinook salmon, and the people and ecosystems benefiting from them.
{"title":"A Synthesis of Factors Related to Trends in Abundance and Demography of Alaska Chinook Salmon (Oncorhynchus tshawytscha, Salmonidae): Implications for Research, Management, and Policy","authors":"Chase C. Lamborn, Jan Ohlberger, Timothy E. Walsworth, Peter A. H. Westley, Curry J. Cunningham, Sam Wynsma, Jordan W. Smith","doi":"10.1111/faf.12895","DOIUrl":"https://doi.org/10.1111/faf.12895","url":null,"abstract":"Across Alaska, there have been synchronous declines in the abundance, mean age, and size of Chinook salmon (<jats:styled-content style=\"fixed-case\"><jats:italic>Oncorhynchus tshawytscha</jats:italic></jats:styled-content>, Salmonidae), a species with immense social and ecological importance. The decline of Chinook salmon, and regulations addressing declines, have drastically impacted people who rely on Alaska's fisheries. Despite their importance, the drivers causing Chinook salmon declines are still not well understood. Therefore, to improve our understanding of the likely drivers of these large‐scale synchronous declines, we synthesised the peer‐reviewed Chinook salmon literature published between 2010 and 2024 using a weight‐of‐evidence approach. We identified 94 variables used to explain the trends in abundance and demographics of Chinook salmon. Each variable's association with trends in Chinook salmon was individually assessed and integrated using a standardised method. Results of this synthesis suggest the drivers for large‐scale synchronous declines have occurred in the North Pacific Ocean. Specifically, we found marine predation, size selective harvest, and pink salmon (<jats:styled-content style=\"fixed-case\"><jats:italic>Oncorhynchus gorbuscha</jats:italic></jats:styled-content>) abundance are the factors most strongly associated with reduced size and age. Results also suggest ocean productivity–specifically winter sea surface temperature and the North Pacific Gyre Oscillation–are the most frequently identified predictors of regional Chinook salmon abundance. In addition to addressing freshwater factors like adult heat stress and juvenile predation, we suggest research, policy, and management focus on how to better understand and address the interactions between ocean productivity, marine predation, size selective harvest, and pink salmon abundance to improve the condition of Chinook salmon, and the people and ecosystems benefiting from them.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"29 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Freddie J. Heather, Shane A. Richards, Nils C. Krueck, Rick D. Stuart‐Smith, Simon J. Brandl, Jordan M. Casey, Graham J. Edgar, Neville Barrett, Valeriano Parravicini, Asta Audzijonyte
Animal body size distributions result from interactions of growth, mortality and recruitment. In ecology and fisheries science, theoretical models of fish body size distributions are widely used but rely on life‐history parameters—growth coefficient (K) and natural mortality rate (M)—that remain unknown for most species and are challenging to estimate. Analysing data from underwater visual surveys and exhaustive sampling, representing 3068 populations across 797 species of shallow‐water, mostly unfished marine fishes, we demonstrate that post‐recruitment body length distributions exhibit a consistent unimodal shape across species and populations. When scaled to the mean body length, these distributions are strikingly similar across all teleost and elasmobranch species, with diverse life histories and maximum body sizes ranging from 1 cm to 3 m. Observed size structure can be approximated by a truncated normal distribution with a coefficient of variation of ~0.34 (SE = 0.002). Such consistent observed body size distributions could be aligned with Beverton–Holt population dynamics theory, if assuming an M/K ratio of ~1.5 and logistic observational selectivity with 50% detectability at ~40% of maximum body length. Alternatively, observed distributions could reflect deviations from theoretical expectations, and reconciling the unimodal distributions with theory may require relaxing some model assumptions, such as continuous recruitment, constant density‐independent growth or constant natural mortality. Overall, the consistency of population‐ and species‐level body length distributions means that unfished size structure could be predicted from a single body size parameter. It also suggests evolutionary convergence of diverse growth and mortality processes towards a narrow range of viable outcomes.
{"title":"Consistent Unimodal Body Length Distributions in Hundreds of Reef Fishes Across Diverse Life Histories","authors":"Freddie J. Heather, Shane A. Richards, Nils C. Krueck, Rick D. Stuart‐Smith, Simon J. Brandl, Jordan M. Casey, Graham J. Edgar, Neville Barrett, Valeriano Parravicini, Asta Audzijonyte","doi":"10.1111/faf.12896","DOIUrl":"https://doi.org/10.1111/faf.12896","url":null,"abstract":"Animal body size distributions result from interactions of growth, mortality and recruitment. In ecology and fisheries science, theoretical models of fish body size distributions are widely used but rely on life‐history parameters—growth coefficient (K) and natural mortality rate (M)—that remain unknown for most species and are challenging to estimate. Analysing data from underwater visual surveys and exhaustive sampling, representing 3068 populations across 797 species of shallow‐water, mostly unfished marine fishes, we demonstrate that post‐recruitment body length distributions exhibit a consistent unimodal shape across species and populations. When scaled to the mean body length, these distributions are strikingly similar across all teleost and elasmobranch species, with diverse life histories and maximum body sizes ranging from 1 cm to 3 m. Observed size structure can be approximated by a truncated normal distribution with a coefficient of variation of ~0.34 (SE = 0.002). Such consistent observed body size distributions could be aligned with Beverton–Holt population dynamics theory, if assuming an M/K ratio of ~1.5 and logistic observational selectivity with 50% detectability at ~40% of maximum body length. Alternatively, observed distributions could reflect deviations from theoretical expectations, and reconciling the unimodal distributions with theory may require relaxing some model assumptions, such as continuous recruitment, constant density‐independent growth or constant natural mortality. Overall, the consistency of population‐ and species‐level body length distributions means that unfished size structure could be predicted from a single body size parameter. It also suggests evolutionary convergence of diverse growth and mortality processes towards a narrow range of viable outcomes.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"103 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143744964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
David Righton, Pieterjan Verhelst, Håkan Westerberg
The life cycle of the European eel (Anguilla anguilla) is inherently risky because it relies on the successful migration of larvae and adults across thousands of kilometres of the Atlantic Ocean. In between these migrations, eels need to grow and develop to maximise their potential for successful reproduction. Eels have a number of life‐history characteristics at each life stage that minimise mortality, starvation and predation risks and maximise opportunities for growth. In the larval and silver eel phases, eels select specific habitats and adopt efficient swimming behaviours to minimise predation and migration failure risks. In the glass and yellow eel phase, the opposite is the case, and plasticity and adaptability enable occupation of a broad ecological niche that maximises growth opportunities and enables a continent‐wide distribution. Under natural conditions, these characteristics enable enough individuals to survive, grow and reproduce so that the population is resilient to natural risks. However, there is increasing evidence of impacts of anthropogenic activities that eels may be particularly sensitive to, resulting in a declining population with reduced resilience. Climate‐linked oceanic risk factors are likely to have a significant influence on the recruitment of eels but are not well understood and cannot be easily modified. However, interventions to mitigate known impacts in the growth environment offer hope for population recovery. A greater understanding of the plasticity of the growth phase and the impacts of risks during the oceanic phase is essential to enable management interventions in the Anthropocene to be fully effective.
{"title":"The Blueprint of the European Eel Life Cycle: Does Life‐History Strategy Undermine or Provide Hope for Population Recovery?","authors":"David Righton, Pieterjan Verhelst, Håkan Westerberg","doi":"10.1111/faf.12894","DOIUrl":"https://doi.org/10.1111/faf.12894","url":null,"abstract":"The life cycle of the European eel (<jats:styled-content style=\"fixed-case\"><jats:italic>Anguilla anguilla</jats:italic></jats:styled-content>) is inherently risky because it relies on the successful migration of larvae and adults across thousands of kilometres of the Atlantic Ocean. In between these migrations, eels need to grow and develop to maximise their potential for successful reproduction. Eels have a number of life‐history characteristics at each life stage that minimise mortality, starvation and predation risks and maximise opportunities for growth. In the larval and silver eel phases, eels select specific habitats and adopt efficient swimming behaviours to minimise predation and migration failure risks. In the glass and yellow eel phase, the opposite is the case, and plasticity and adaptability enable occupation of a broad ecological niche that maximises growth opportunities and enables a continent‐wide distribution. Under natural conditions, these characteristics enable enough individuals to survive, grow and reproduce so that the population is resilient to natural risks. However, there is increasing evidence of impacts of anthropogenic activities that eels may be particularly sensitive to, resulting in a declining population with reduced resilience. Climate‐linked oceanic risk factors are likely to have a significant influence on the recruitment of eels but are not well understood and cannot be easily modified. However, interventions to mitigate known impacts in the growth environment offer hope for population recovery. A greater understanding of the plasticity of the growth phase and the impacts of risks during the oceanic phase is essential to enable management interventions in the Anthropocene to be fully effective.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"401 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
David M. Benoit, Daniel P. Zielinski, Reid G. Swanson, Donald A. Jackson, Robert L. McLaughlin, Theodore R. Castro‐Santos, R. Andrew Goodwin, Thomas C. Pratt, Andrew M. Muir
The importance of connectivity for freshwater organisms is widely recognised, yet in‐stream barriers associated with population declines and increased risk of extinction remain globally ubiquitous. Despite their negative consequences, these barriers can protect aquatic communities by limiting the spread of invasive species, leading to conflicting management goals in some regions. Selective fish passage is a solution for the conflicting goals of passing native, desirable species while restricting the spread of invasives. Approaches that can target groups of species sharing similar attributes (i.e. guilds) are likely to be more efficient than those that target species individually, particularly in taxonomically diverse systems. We explored the guild structure of 220 Great Lakes freshwater fishes based on morphological, phenological, physiological and behavioural attributes associated with passage and movement. We identified five distinct guilds as well as the attributes most important for defining these groupings: maximum total length, trophic level, relative eye size, spawning temperature, spawning season, presence/absence of ampullary electroreceptors and the presence/absence of hearing specialisations. The approaches outlined in this work can be generalised to enhance selective fish passage in aquatic ecosystems worldwide.
{"title":"Designing Sortable Guilds for Multispecies Selective Fish Passage","authors":"David M. Benoit, Daniel P. Zielinski, Reid G. Swanson, Donald A. Jackson, Robert L. McLaughlin, Theodore R. Castro‐Santos, R. Andrew Goodwin, Thomas C. Pratt, Andrew M. Muir","doi":"10.1111/faf.12888","DOIUrl":"https://doi.org/10.1111/faf.12888","url":null,"abstract":"The importance of connectivity for freshwater organisms is widely recognised, yet in‐stream barriers associated with population declines and increased risk of extinction remain globally ubiquitous. Despite their negative consequences, these barriers can protect aquatic communities by limiting the spread of invasive species, leading to conflicting management goals in some regions. Selective fish passage is a solution for the conflicting goals of passing native, desirable species while restricting the spread of invasives. Approaches that can target groups of species sharing similar attributes (i.e. guilds) are likely to be more efficient than those that target species individually, particularly in taxonomically diverse systems. We explored the guild structure of 220 Great Lakes freshwater fishes based on morphological, phenological, physiological and behavioural attributes associated with passage and movement. We identified five distinct guilds as well as the attributes most important for defining these groupings: maximum total length, trophic level, relative eye size, spawning temperature, spawning season, presence/absence of ampullary electroreceptors and the presence/absence of hearing specialisations. The approaches outlined in this work can be generalised to enhance selective fish passage in aquatic ecosystems worldwide.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"26 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mollie Rickwood, Chris Kerry, Ole R. Eigaard, Antonello Sala, Ciarán McLaverty, Callum M. Roberts, Brendan J. Godley, Kristian Metcalfe
Fishing with active bottom‐contacting gears (here collectively described as 'bottom trawling') is considered the greatest source of anthropogenic disturbance to marine sediments. However, uncertainties are apparent in studies evaluating the severity of their impacts from fishing with these gears at the global scale. A major uncertainty is the estimation of the area of seabed disturbed by applying European‐based vessel size to gear footprint (i.e., gear width) relationships to the global fleet, thereby assuming these relations hold worldwide. To test the strength of this assumption, we conducted a structured review to understand global variation in fishing gear parameters and, thus, footprint of bottom trawling gears. While we find a European bias in the primary literature, we find that the relationship between vessel size and gear footprint differs significantly among FAO Major Fishing Areas, suggesting that European‐based relationships are not representative of fleets worldwide. For example, otter trawler footprints in the Mediterranean and the Black Sea increase by 10.2 m for every meter increase in overall vessel length compared to just 3.3 m for otter trawlers in the Northwest Atlantic. These findings challenge the reliability of previous estimates of the global footprint of bottom trawling gears, thus highlighting the urgent need for improved availability of commercial data to create a globally representative data set that can address uncertainties in the quantification of anthropogenic disturbance of the benthic environment and the consequential impacts on biodiversity, ecosystem integrity and carbon losses.
{"title":"Regional Variation in Active Bottom‐Contacting Gear Footprints","authors":"Mollie Rickwood, Chris Kerry, Ole R. Eigaard, Antonello Sala, Ciarán McLaverty, Callum M. Roberts, Brendan J. Godley, Kristian Metcalfe","doi":"10.1111/faf.12893","DOIUrl":"https://doi.org/10.1111/faf.12893","url":null,"abstract":"Fishing with active bottom‐contacting gears (here collectively described as 'bottom trawling') is considered the greatest source of anthropogenic disturbance to marine sediments. However, uncertainties are apparent in studies evaluating the severity of their impacts from fishing with these gears at the global scale. A major uncertainty is the estimation of the area of seabed disturbed by applying European‐based vessel size to gear footprint (i.e., gear width) relationships to the global fleet, thereby assuming these relations hold worldwide. To test the strength of this assumption, we conducted a structured review to understand global variation in fishing gear parameters and, thus, footprint of bottom trawling gears. While we find a European bias in the primary literature, we find that the relationship between vessel size and gear footprint differs significantly among FAO Major Fishing Areas, suggesting that European‐based relationships are not representative of fleets worldwide. For example, otter trawler footprints in the Mediterranean and the Black Sea increase by 10.2 m for every meter increase in overall vessel length compared to just 3.3 m for otter trawlers in the Northwest Atlantic. These findings challenge the reliability of previous estimates of the global footprint of bottom trawling gears, thus highlighting the urgent need for improved availability of commercial data to create a globally representative data set that can address uncertainties in the quantification of anthropogenic disturbance of the benthic environment and the consequential impacts on biodiversity, ecosystem integrity and carbon losses.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"183 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matthew L. H. Cheng, Daniel R. Goethel, Peter‐John F. Hulson, Michael J. Wilberg, Craig Marsh, Curry J. Cunningham
Sex‐specific variation in population demography and life‐history traits (e.g., growth, natural mortality) is common in many fish populations. Differences in these processes by sex can dictate population dynamics and influence how harvesters interact with the resource. Across various fisheries management systems, stock assessment models (SAMs), which mathematically represent population age and/or size structure, are widely utilised to estimate fish population status and provide sustainable harvest recommendations. However, few studies have examined the implications of alternative modelling assumptions when incorporating sex‐specific dynamics in SAMs. For instance, the impacts of simultaneously ignoring sex‐specific variations in growth, selectivity, and natural mortality on SAM performance have not been explored. In this study, a simulation‐estimation framework was developed for a sexually dimorphic fish population to: (1) assess the consequences of ignoring sexual dimorphism (i.e., growth, natural mortality, and selectivity) and the benefits of using sex‐specific catch data to inform the estimation of these processes, (2) evaluate the implications of incorrect modelling assumptions regarding sex ratio at birth, and (3) develop advice for parameterising observation likelihoods to describe sex‐specific composition data. Correctly parameterising sex‐specific variation in life‐history traits led to more robust population estimates and catch advice. Conversely, SAMs ignoring these variations yielded biased estimates of biomass and harvest recommendations. Collectively, our results underscore that oversimplified assumptions about sex‐specific variations in SAMs can lead to poor management advice. Moreover, results emphasise the need for routine collection of sex‐specific data to support the development of biologically realistic models.
{"title":"Misspecifying Sex‐Structured Dynamics in Stock Assessment Models","authors":"Matthew L. H. Cheng, Daniel R. Goethel, Peter‐John F. Hulson, Michael J. Wilberg, Craig Marsh, Curry J. Cunningham","doi":"10.1111/faf.12891","DOIUrl":"https://doi.org/10.1111/faf.12891","url":null,"abstract":"Sex‐specific variation in population demography and life‐history traits (e.g., growth, natural mortality) is common in many fish populations. Differences in these processes by sex can dictate population dynamics and influence how harvesters interact with the resource. Across various fisheries management systems, stock assessment models (SAMs), which mathematically represent population age and/or size structure, are widely utilised to estimate fish population status and provide sustainable harvest recommendations. However, few studies have examined the implications of alternative modelling assumptions when incorporating sex‐specific dynamics in SAMs. For instance, the impacts of simultaneously ignoring sex‐specific variations in growth, selectivity, and natural mortality on SAM performance have not been explored. In this study, a simulation‐estimation framework was developed for a sexually dimorphic fish population to: (1) assess the consequences of ignoring sexual dimorphism (i.e., growth, natural mortality, and selectivity) and the benefits of using sex‐specific catch data to inform the estimation of these processes, (2) evaluate the implications of incorrect modelling assumptions regarding sex ratio at birth, and (3) develop advice for parameterising observation likelihoods to describe sex‐specific composition data. Correctly parameterising sex‐specific variation in life‐history traits led to more robust population estimates and catch advice. Conversely, SAMs ignoring these variations yielded biased estimates of biomass and harvest recommendations. Collectively, our results underscore that oversimplified assumptions about sex‐specific variations in SAMs can lead to poor management advice. Moreover, results emphasise the need for routine collection of sex‐specific data to support the development of biologically realistic models.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"19 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143608041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Leonardo Manir Feitosa, Alicia M. Caughman, Nidhi G. D'Costa, Sara Orofino, Echelle S. Burns, Laurenne Schiller, Boris Worm, Darcy Bradley
Sharks are among the most threatened groups of exploited fishes, comprising common bycatch across many fisheries. Management efforts intended to safeguard threatened species have increasingly focused on retention bans to reduce bycatch mortality. However, the population effects of such measures remain unevaluated across species. We combined available data from 160 studies providing estimates of at‐vessel or post‐release mortality for 147 taxa caught by different fishing gears to create random‐forest regression models and predict mortality rates for 341 shark species incidentally captured by longlines or gillnets. Smaller‐bodied species inhabiting shallow waters were more likely to suffer at‐vessel mortality compared to their deep‐water counterparts, for which post‐release mortality was more likely to occur. We then used results for longlines to simulate the effect of retention bans in reducing fishing mortality to sustainable levels. Our metric consists of the ratio between the proportion of each species' population caught and discarded (PMAX) under a retention ban divided by the fishing mortality (F) predicted to achieve maximum sustainable yield (FMSY). Our calculations show that a retention ban yielded an average ~ three‐fold higher PMAX compared to FMSY, with 18% of the species having PMAX/FMSY < 2, 72.3% having 2 < PMAX/FMSY < 5, and 9.7% having PMAX/FMSY > 5. For threatened species, median PMAX/FMSY = 2.28 and non‐threatened ones had median PMAX/FMSY = 2.77. Our study shows that retention bans could reduce shark mortality, but must be combined with additional measures to stop overfishing, especially for low‐productivity species.
{"title":"Retention Bans Are Beneficial but Insufficient to Stop Shark Overfishing","authors":"Leonardo Manir Feitosa, Alicia M. Caughman, Nidhi G. D'Costa, Sara Orofino, Echelle S. Burns, Laurenne Schiller, Boris Worm, Darcy Bradley","doi":"10.1111/faf.12892","DOIUrl":"https://doi.org/10.1111/faf.12892","url":null,"abstract":"Sharks are among the most threatened groups of exploited fishes, comprising common bycatch across many fisheries. Management efforts intended to safeguard threatened species have increasingly focused on retention bans to reduce bycatch mortality. However, the population effects of such measures remain unevaluated across species. We combined available data from 160 studies providing estimates of at‐vessel or post‐release mortality for 147 taxa caught by different fishing gears to create random‐forest regression models and predict mortality rates for 341 shark species incidentally captured by longlines or gillnets. Smaller‐bodied species inhabiting shallow waters were more likely to suffer at‐vessel mortality compared to their deep‐water counterparts, for which post‐release mortality was more likely to occur. We then used results for longlines to simulate the effect of retention bans in reducing fishing mortality to sustainable levels. Our metric consists of the ratio between the proportion of each species' population caught and discarded (<jats:italic>P</jats:italic><jats:sub>MAX</jats:sub>) under a retention ban divided by the fishing mortality (<jats:italic>F</jats:italic>) predicted to achieve maximum sustainable yield (<jats:italic>F</jats:italic><jats:sub>MSY</jats:sub>). Our calculations show that a retention ban yielded an average ~ three‐fold higher <jats:italic>P</jats:italic><jats:sub>MAX</jats:sub> compared to <jats:italic>F</jats:italic><jats:sub><jats:italic>MSY</jats:italic></jats:sub>, with 18% of the species having <jats:italic>P</jats:italic><jats:sub>MAX</jats:sub><jats:italic>/F</jats:italic><jats:sub>MSY</jats:sub> < 2, 72.3% having 2 < <jats:italic>P</jats:italic><jats:sub>MAX</jats:sub><jats:italic>/F</jats:italic><jats:sub>MSY</jats:sub> < 5, and 9.7% having <jats:italic>P</jats:italic><jats:sub>MAX</jats:sub><jats:italic>/F</jats:italic><jats:sub>MSY</jats:sub> > 5. For threatened species, median <jats:italic>P</jats:italic><jats:sub>MAX</jats:sub><jats:italic>/F</jats:italic><jats:sub>MSY</jats:sub> = 2.28 and non‐threatened ones had median <jats:italic>P</jats:italic><jats:sub>MAX</jats:sub><jats:italic>/F</jats:italic><jats:sub>MSY</jats:sub> = 2.77. Our study shows that retention bans could reduce shark mortality, but must be combined with additional measures to stop overfishing, especially for low‐productivity species.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"4 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143599832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jan Ohlberger, Eric R. Buhle, Thomas W. Buehrens, Neala W. Kendall, Toby Harbison, Andrew M. Claiborne, James P. Losee, Jennifer Whitney, Mark D. Scheuerell
Species with complex life cycles, such as anadromous fish that perform spawning migrations between freshwater and the ocean, may be particularly sensitive to global change because freshwater and marine habitats experience distinct shifts in climate and ecosystem dynamics. Abundances of wild steelhead trout (Oncorhynchus mykiss) have declined across most of their range over the past 40–50 years. We examined whether declines in steelhead survival can be linked to changing climate conditions and species interactions. A novel hierarchical integrated population model that accounts for the species' complex life history was fitted to data from multiple wild steelhead populations on the Washington coast, U.S.A. The model estimates recruitment residuals and kelt survival rates as time‐varying processes, which reflect annual variation in survival before and after first maturation. We found that survival rates of immature steelhead (recruits) and adult steelhead (kelts) have declined over time and that survival trends across populations were strongly associated with climate and ecosystem change, specifically summer sea surface temperature and pink salmon abundance in the North Pacific Ocean, the NPGO index and river flows. Including these drivers in the model reduced unexplained annual variation in shared recruitment and kelt survival anomalies and largely accounted for their negative long‐term trends. Our findings provide evidence that rising temperatures and increased interspecific competition at sea have contributed to declines in steelhead survival over the last five decades. Considering projected warming and high pink salmon abundances in the ocean, steelhead will likely continue to experience low marine survival rates.
{"title":"Declining Marine Survival of Steelhead Trout Linked to Climate and Ecosystem Change","authors":"Jan Ohlberger, Eric R. Buhle, Thomas W. Buehrens, Neala W. Kendall, Toby Harbison, Andrew M. Claiborne, James P. Losee, Jennifer Whitney, Mark D. Scheuerell","doi":"10.1111/faf.12878","DOIUrl":"https://doi.org/10.1111/faf.12878","url":null,"abstract":"Species with complex life cycles, such as anadromous fish that perform spawning migrations between freshwater and the ocean, may be particularly sensitive to global change because freshwater and marine habitats experience distinct shifts in climate and ecosystem dynamics. Abundances of wild steelhead trout (<jats:styled-content style=\"fixed-case\"><jats:italic>Oncorhynchus mykiss</jats:italic></jats:styled-content>) have declined across most of their range over the past 40–50 years. We examined whether declines in steelhead survival can be linked to changing climate conditions and species interactions. A novel hierarchical integrated population model that accounts for the species' complex life history was fitted to data from multiple wild steelhead populations on the Washington coast, U.S.A. The model estimates recruitment residuals and kelt survival rates as time‐varying processes, which reflect annual variation in survival before and after first maturation. We found that survival rates of immature steelhead (recruits) and adult steelhead (kelts) have declined over time and that survival trends across populations were strongly associated with climate and ecosystem change, specifically summer sea surface temperature and pink salmon abundance in the North Pacific Ocean, the NPGO index and river flows. Including these drivers in the model reduced unexplained annual variation in shared recruitment and kelt survival anomalies and largely accounted for their negative long‐term trends. Our findings provide evidence that rising temperatures and increased interspecific competition at sea have contributed to declines in steelhead survival over the last five decades. Considering projected warming and high pink salmon abundances in the ocean, steelhead will likely continue to experience low marine survival rates.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"21 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143599836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tom Gammage, Georgina G. Gurney, Amy Diedrich, Rayhan Dudayev
Small‐scale fisheries (SSF) are commonly governed through co‐management, a widely advocated approach for promoting equitable governance. However, evidence suggests that this governance approach can sometimes exacerbate power imbalances, facilitate elite capture and intensify conflicts. To foster co‐management that successfully enhances equity in SSF governance, it is crucial to understand when and why it leads to positive or negative equity outcomes. To this end, we undertook a scoping review to identify empirical research on the relationship between SSF co‐management and equity outcomes. We identified 30 empirical studies that assessed equity outcomes in SSF co‐management initiatives. Our analysis revealed four key findings: (1) distributional and procedural equity received approximately equal levels of attention, largely without an explicit equity lens; (2) co‐management had mixed impacts on equity, with the most prevalent outcome being improvement to equity; (3) delegated and cooperative co‐management types were more often associated with improved equity outcomes, while consultative co‐management was more often associated with reductions or no change; and (4) inclusive participation, strong social capital and secure property rights were most often associated with improved equity outcomes, while weak social capital, institutional design and management oversight were most often associated with reduced equity outcomes. However, the evidence supporting our findings was limited, with only seven studies robustly documenting the role of inclusive participation in enhancing equity. Our review offers valuable insights into the complex interplay between SSF co‐management and equity, informing future research and practice and policy interventions aimed at achieving social goals through co‐management governance approaches.
{"title":"Equity Through Co‐Management in Small‐Scale Fisheries—A Review","authors":"Tom Gammage, Georgina G. Gurney, Amy Diedrich, Rayhan Dudayev","doi":"10.1111/faf.12889","DOIUrl":"https://doi.org/10.1111/faf.12889","url":null,"abstract":"Small‐scale fisheries (SSF) are commonly governed through co‐management, a widely advocated approach for promoting equitable governance. However, evidence suggests that this governance approach can sometimes exacerbate power imbalances, facilitate elite capture and intensify conflicts. To foster co‐management that successfully enhances equity in SSF governance, it is crucial to understand when and why it leads to positive or negative equity outcomes. To this end, we undertook a scoping review to identify empirical research on the relationship between SSF co‐management and equity outcomes. We identified 30 empirical studies that assessed equity outcomes in SSF co‐management initiatives. Our analysis revealed four key findings: (1) distributional and procedural equity received approximately equal levels of attention, largely without an explicit equity lens; (2) co‐management had mixed impacts on equity, with the most prevalent outcome being improvement to equity; (3) delegated and cooperative co‐management types were more often associated with improved equity outcomes, while consultative co‐management was more often associated with reductions or no change; and (4) inclusive participation, strong social capital and secure property rights were most often associated with improved equity outcomes, while weak social capital, institutional design and management oversight were most often associated with reduced equity outcomes. However, the evidence supporting our findings was limited, with only seven studies robustly documenting the role of inclusive participation in enhancing equity. Our review offers valuable insights into the complex interplay between SSF co‐management and equity, informing future research and practice and policy interventions aimed at achieving social goals through co‐management governance approaches.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"31 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143582978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Paul J. Dolder, Jan Jaap Poos, Michael A. Spence, Dorleta García, Cóilín Minto
Scientific advice for fisheries management rarely takes into account how fishers react to regulations, which can lead to unexpected results and unrealistic expectations of the effectiveness of the management measures. Short‐term decisions about when and where to fish are one of the greatest sources of uncertainty in predicting management outcomes. Several models have been developed to predict how fishers allocate effort in space and time, including mechanistic methods such as gravity and dynamic state variable models, and statistical methods such as random utility and Markov models. These have been individually used to predict effort allocation for various fisheries, but there is no comparative synthesis of their structure and characteristics. We demonstrate strong theoretical links between utility and choice in gravity, random utility, Markov and dynamic state variable models. Using an advanced event‐based simulation framework, we find that mechanistic models bias effort allocation to certain areas when applying commonly used strong assumptions about drivers of effort allocation; and conversely, statistical models accurately predict the distribution of fishing effort under business as usual. However, predictive performance degrades with previously unobserved dynamics, such as a spatial closure. Mechanistic models were less suited to general application under business as usual but provide a useful framework for testing hypotheses about a fishery system in response to policy change. Comparison of simple model formulations yielded significant insight into the characteristics of the models and how they could be used to evaluate alternative management approaches for mixed fisheries.
{"title":"A Comparison of Fleet Dynamics Models for Predicting Fisher Location Choice","authors":"Paul J. Dolder, Jan Jaap Poos, Michael A. Spence, Dorleta García, Cóilín Minto","doi":"10.1111/faf.12886","DOIUrl":"https://doi.org/10.1111/faf.12886","url":null,"abstract":"Scientific advice for fisheries management rarely takes into account how fishers react to regulations, which can lead to unexpected results and unrealistic expectations of the effectiveness of the management measures. Short‐term decisions about when and where to fish are one of the greatest sources of uncertainty in predicting management outcomes. Several models have been developed to predict how fishers allocate effort in space and time, including mechanistic methods such as gravity and dynamic state variable models, and statistical methods such as random utility and Markov models. These have been individually used to predict effort allocation for various fisheries, but there is no comparative synthesis of their structure and characteristics. We demonstrate strong theoretical links between utility and choice in gravity, random utility, Markov and dynamic state variable models. Using an advanced event‐based simulation framework, we find that mechanistic models bias effort allocation to certain areas when applying commonly used strong assumptions about drivers of effort allocation; and conversely, statistical models accurately predict the distribution of fishing effort under business as usual. However, predictive performance degrades with previously unobserved dynamics, such as a spatial closure. Mechanistic models were less suited to general application under business as usual but provide a useful framework for testing hypotheses about a fishery system in response to policy change. Comparison of simple model formulations yielded significant insight into the characteristics of the models and how they could be used to evaluate alternative management approaches for mixed fisheries.","PeriodicalId":169,"journal":{"name":"Fish and Fisheries","volume":"239 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143507101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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