Pub Date : 2025-12-22DOI: 10.1016/j.fishres.2025.107636
Guillermo Boyra, Udane Martinez
In multibeam sonar systems, beam overlap introduces distortion in across-beam size measurements, leading to overestimation of target dimensions. A previously developed method estimated beam overlap by comparing along-beam and across-beam measurements of fish schools during purse seine maneuvers, demonstrating the presence of overlap and proposing a metric for its quantification. However, this approach required substantial effort and had limited precision on vertical swaths. In this study, we present a simplified and reproducible method for estimating beam overlap using standard calibration spheres commonly employed in fisheries acoustics. The procedure involves placing a sphere of known diameter at the center of a sonar beam. Provided the range is sufficient for the beam to fully encompass the target, the degree of overlap is estimated by counting the number of beams that detect the sphere. This method yielded results similar to the previous approach, while requiring considerably less effort. It can be performed nearshore in a few hours, and allows for overlap estimation in both horizontal and vertical planes with similar accuracy. The proposed technique offers a practical and efficient alternative for beam overlap calibration, facilitating its integration into standard acoustic calibration protocols.
{"title":"A simple method to measure beam overlap in multibeam sonars using calibration spheres","authors":"Guillermo Boyra, Udane Martinez","doi":"10.1016/j.fishres.2025.107636","DOIUrl":"10.1016/j.fishres.2025.107636","url":null,"abstract":"<div><div>In multibeam sonar systems, beam overlap introduces distortion in across-beam size measurements, leading to overestimation of target dimensions. A previously developed method estimated beam overlap by comparing along-beam and across-beam measurements of fish schools during purse seine maneuvers, demonstrating the presence of overlap and proposing a metric for its quantification. However, this approach required substantial effort and had limited precision on vertical swaths. In this study, we present a simplified and reproducible method for estimating beam overlap using standard calibration spheres commonly employed in fisheries acoustics. The procedure involves placing a sphere of known diameter at the center of a sonar beam. Provided the range is sufficient for the beam to fully encompass the target, the degree of overlap is estimated by counting the number of beams that detect the sphere. This method yielded results similar to the previous approach, while requiring considerably less effort. It can be performed nearshore in a few hours, and allows for overlap estimation in both horizontal and vertical planes with similar accuracy. The proposed technique offers a practical and efficient alternative for beam overlap calibration, facilitating its integration into standard acoustic calibration protocols.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107636"},"PeriodicalIF":2.3,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-20DOI: 10.1016/j.fishres.2025.107638
Fortunata Donato , Federico Calì , Carlotta Mazzoldi , Alberto Santojanni , Mario La Mesa
This study investigates some biological traits of the blackbellied anglerfish (Lophius budegassa) in the central Adriatic Sea, an area characterised by intense bottom trawling activity and high ecological importance. Reproductive parameters of the local population, such as sex ratio, gonado-somatic index, sexual maturity and fecundity were assessed by macroscopic and histological analyses of gonads, whereas age and somatic growth were estimated using illicium sections. The results revealed pronounced differences in size, growth, and maturation between sexes. Females attained significantly larger sizes and older ages than males, with asymptotic sizes of 73.0 cm and 43.2 cm and maximum ages of 15 and 6 years, respectively. Growth was negatively allometric for both sexes, whereas the condition factor was significantly higher in females, likely reflecting differing reproductive strategies and energy allocation patterns. Consistent with the marked dimorphism in size, size at first sexual maturity was markedly higher in females than in males. Histological and gonado-somatic analyses confirmed an extended spawning season from autumn through late spring, with peak reproductive activity of females in May and October. Females exhibited synchronous oocyte development, with total fecundity ranging from 82247 to 276332 oocytes/female and relative fecundity between 33–91 oocytes/g. These findings provide novel insights into the life history of L. budegassa in the central Adriatic Sea and contribute to a better understanding of its population structure and reproductive strategies. The information obtained is relevant for future stock assessments and the development of science-based management measures aimed at the sustainable exploitation of this commercially and ecologically important species.
{"title":"Biological traits of blackbellied angler (Lophius budegassa Spinola, 1807) in the central Adriatic Sea","authors":"Fortunata Donato , Federico Calì , Carlotta Mazzoldi , Alberto Santojanni , Mario La Mesa","doi":"10.1016/j.fishres.2025.107638","DOIUrl":"10.1016/j.fishres.2025.107638","url":null,"abstract":"<div><div>This study investigates some biological traits of the blackbellied anglerfish (<em>Lophius budegassa</em>) in the central Adriatic Sea, an area characterised by intense bottom trawling activity and high ecological importance. Reproductive parameters of the local population, such as sex ratio, gonado-somatic index, sexual maturity and fecundity were assessed by macroscopic and histological analyses of gonads, whereas age and somatic growth were estimated using illicium sections. The results revealed pronounced differences in size, growth, and maturation between sexes. Females attained significantly larger sizes and older ages than males, with asymptotic sizes of 73.0 cm and 43.2 cm and maximum ages of 15 and 6 years, respectively. Growth was negatively allometric for both sexes, whereas the condition factor was significantly higher in females, likely reflecting differing reproductive strategies and energy allocation patterns. Consistent with the marked dimorphism in size, size at first sexual maturity was markedly higher in females than in males. Histological and gonado-somatic analyses confirmed an extended spawning season from autumn through late spring, with peak reproductive activity of females in May and October. Females exhibited synchronous oocyte development, with total fecundity ranging from 82247 to 276332 oocytes/female and relative fecundity between 33–91 oocytes/g. These findings provide novel insights into the life history of <em>L. budegassa</em> in the central Adriatic Sea and contribute to a better understanding of its population structure and reproductive strategies. The information obtained is relevant for future stock assessments and the development of science-based management measures aimed at the sustainable exploitation of this commercially and ecologically important species.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107638"},"PeriodicalIF":2.3,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-20DOI: 10.1016/j.fishres.2025.107637
Kaitlyn R. Zinn , Stephen D. Johnston , Quin V.A. Johnston , Arthur L. Bass , Lance A. Weber , Scott G. Hinch
Capture and release (CR) is a management strategy increasingly employed in Pacific salmon (Oncorhynchus spp.) recreational fisheries to help balance management objectives of stock conservation and sustainable harvest. Although sustainability is contingent upon low post-release mortality, CR post-release mortality in marine recreational salmon fisheries has rarely been estimated and the underlying mechanisms are not well understood. We angled Chinook salmon (O. tshawytscha) using approaches typical for the fishery, then transported fish to ocean-side tanks for 10-day observations. Angling treatments included hook type (barbless; single vs. treble), lure type (bait vs. artificial), in-line flasher use (yes vs. no), and release approach (gaff-release vs. no gaff-release). Treble hooks were associated with poor survival in small fish (37 % survival for fish < 60 cm). Immediate mortality (< 2 h after capture) occurred in 8.4 % of Chinook salmon, and was associated with bleeding, sea surface temperature, fork length, transfer time, and the inner mouth hook location. There was little mortality until day-3, then mortality increased to day-5, and was associated with high levels of bleeding, fin damage, vessel transfer, scale loss, fork length, gill impairment, and sex. Fish with minor injuries had 74 % higher survival to the end of the holding period than those with high levels of bleeding, scale loss, and fin damage. Post-release mortality of Chinook salmon in the marine recreational fishery can be minimized through improved fish handling and release practices, specifically by not using treble hooks, avoiding small fish, and releasing fish at the water line without the use of a net.
{"title":"Influence of gear type, release method, and injury on immediate and delayed mortality of Chinook salmon (Oncorhynchus tshawytscha) captured and released from a marine recreational fishery","authors":"Kaitlyn R. Zinn , Stephen D. Johnston , Quin V.A. Johnston , Arthur L. Bass , Lance A. Weber , Scott G. Hinch","doi":"10.1016/j.fishres.2025.107637","DOIUrl":"10.1016/j.fishres.2025.107637","url":null,"abstract":"<div><div>Capture and release (CR) is a management strategy increasingly employed in Pacific salmon (<em>Oncorhynchus</em> spp.<em>)</em> recreational fisheries to help balance management objectives of stock conservation and sustainable harvest. Although sustainability is contingent upon low post-release mortality, CR post-release mortality in marine recreational salmon fisheries has rarely been estimated and the underlying mechanisms are not well understood. We angled Chinook salmon (<em>O. tshawytscha)</em> using approaches typical for the fishery, then transported fish to ocean-side tanks for 10-day observations. Angling treatments included hook type (barbless; single vs. treble), lure type (bait vs. artificial), in-line flasher use (yes vs. no), and release approach (gaff-release vs. no gaff-release). Treble hooks were associated with poor survival in small fish (37 % survival for fish < 60 cm). Immediate mortality (< 2 h after capture) occurred in 8.4 % of Chinook salmon, and was associated with bleeding, sea surface temperature, fork length, transfer time, and the inner mouth hook location. There was little mortality until day-3, then mortality increased to day-5, and was associated with high levels of bleeding, fin damage, vessel transfer, scale loss, fork length, gill impairment, and sex. Fish with minor injuries had 74 % higher survival to the end of the holding period than those with high levels of bleeding, scale loss, and fin damage. Post-release mortality of Chinook salmon in the marine recreational fishery can be minimized through improved fish handling and release practices, specifically by not using treble hooks, avoiding small fish, and releasing fish at the water line without the use of a net.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107637"},"PeriodicalIF":2.3,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-18DOI: 10.1016/j.fishres.2025.107635
Jessica A. McCordic , Rochelle M. Gordon , Logan R. Kline , Natalie K. Rivero , Sofie M. Van Parijs
Managers of marine protected areas rely on monitoring to effectively combat noncompliance. National Park Zones (NPZs) within Australian Marine Parks prohibit fishing and other extractive activities, but some are located in remote areas and present a variety of challenges to monitoring, including increased time and costs to maintain regular patrols. In this study, passive acoustic recorders were deployed in nine NPZs for between 19 and 84 days, providing a record of vessel presence within each NPZ. Models of acoustic transmission loss were estimated for each NPZ to determine the likelihood of acoustically detected vessels occurring within NPZ boundaries. Vessels determined to occur within the NPZs were further classified by acoustic characteristics to identify maneuvering vessels potentially exhibiting noncompliant behaviors. NPZs farther offshore showed lower presence overall and less consistent temporal patterns in activity. For NPZs closer to shore, daily presence was higher on weekdays later in the week, and hourly presence peaked during daylight hours, consistent with recreational boating activity. Inshore NPZs generally showed higher proportions of maneuvering vessels compared to NPZs that were farther offshore, but the detection of maneuvering vessels in offshore NPZs indicates the value of acoustic monitoring to capture infrequently occurring events indicative of noncompliance. The results from this observational study highlight the benefits of using passive acoustic monitoring to provide managers with an improved understanding of compliance across NPZs, allowing them to understand human use patterns and target enforcement efforts with increased efficiency.
{"title":"A sound check on compliance: Acoustically detected vessel presence indicates variation in behavior across marine protected areas","authors":"Jessica A. McCordic , Rochelle M. Gordon , Logan R. Kline , Natalie K. Rivero , Sofie M. Van Parijs","doi":"10.1016/j.fishres.2025.107635","DOIUrl":"10.1016/j.fishres.2025.107635","url":null,"abstract":"<div><div>Managers of marine protected areas rely on monitoring to effectively combat noncompliance. National Park Zones (NPZs) within Australian Marine Parks prohibit fishing and other extractive activities, but some are located in remote areas and present a variety of challenges to monitoring, including increased time and costs to maintain regular patrols. In this study, passive acoustic recorders were deployed in nine NPZs for between 19 and 84 days, providing a record of vessel presence within each NPZ. Models of acoustic transmission loss were estimated for each NPZ to determine the likelihood of acoustically detected vessels occurring within NPZ boundaries. Vessels determined to occur within the NPZs were further classified by acoustic characteristics to identify maneuvering vessels potentially exhibiting noncompliant behaviors. NPZs farther offshore showed lower presence overall and less consistent temporal patterns in activity. For NPZs closer to shore, daily presence was higher on weekdays later in the week, and hourly presence peaked during daylight hours, consistent with recreational boating activity. Inshore NPZs generally showed higher proportions of maneuvering vessels compared to NPZs that were farther offshore, but the detection of maneuvering vessels in offshore NPZs indicates the value of acoustic monitoring to capture infrequently occurring events indicative of noncompliance. The results from this observational study highlight the benefits of using passive acoustic monitoring to provide managers with an improved understanding of compliance across NPZs, allowing them to understand human use patterns and target enforcement efforts with increased efficiency.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107635"},"PeriodicalIF":2.3,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-16DOI: 10.1016/j.fishres.2025.107632
Emily A. Fisher , S. Alex Hesp , Peter G. Coulson , Jeffrey V. Norriss , David V. Fairclough , Gary Jackson
Spatial variation in life history characteristics of fish species with extensive geographic ranges needs consideration for stock assessment and management. Additionally, traditional growth models can provide biased parameter estimates if fishing-related effects on length and age samples are not accounted for. This study of the commercially and recreationally important berycid Centroberyx gerrardi in southern Australia explored implications, for growth estimation, of selectivity and fishing mortality effects across three regions in Western Australia. Using length-at-age data derived from commercial line catches, taken from a large depth range and comprising a wide age range (5–84 years), traditional von Bertalanffy growth models indicated regional differences in growth. These estimated regional differences became reduced when von Bertalanffy growth models were fitted using informative priors to constrain some growth parameters to feasible values. In contrast, a length and age-based catch curve model (LACC) that simultaneously estimates growth, selectivity and fishing mortality indicated no regional growth differences. A simulation study confirmed that, among the three alternative growth models, the LACC is most reliable for estimating growth of C. gerrardi when data for small and young fish are limited. The lengths at which C. gerrardi become selected by commercial line fishing differed among regions, potentially reflecting a size-related, westward movement of fish along the south coast to important spawning areas. Different potential conclusions regarding growth and connectivity for C. gerrardi, depending on which growth model was applied, highlight the importance of considering fishing-related effects when estimating growth of exploited fish species.
{"title":"Accounting for selectivity is important when using fishery-dependent data to compare growth of Bight redfish (Centroberyx gerrardi) throughout its distribution in south-western Australia","authors":"Emily A. Fisher , S. Alex Hesp , Peter G. Coulson , Jeffrey V. Norriss , David V. Fairclough , Gary Jackson","doi":"10.1016/j.fishres.2025.107632","DOIUrl":"10.1016/j.fishres.2025.107632","url":null,"abstract":"<div><div>Spatial variation in life history characteristics of fish species with extensive geographic ranges needs consideration for stock assessment and management. Additionally, traditional growth models can provide biased parameter estimates if fishing-related effects on length and age samples are not accounted for. This study of the commercially and recreationally important berycid <em>Centroberyx gerrardi</em> in southern Australia explored implications, for growth estimation, of selectivity and fishing mortality effects across three regions in Western Australia. Using length-at-age data derived from commercial line catches, taken from a large depth range and comprising a wide age range (5–84 years), traditional von Bertalanffy growth models indicated regional differences in growth. These estimated regional differences became reduced when von Bertalanffy growth models were fitted using informative priors to constrain some growth parameters to feasible values. In contrast, a length and age-based catch curve model (LACC) that simultaneously estimates growth, selectivity and fishing mortality indicated no regional growth differences. A simulation study confirmed that, among the three alternative growth models, the LACC is most reliable for estimating growth of <em>C. gerrardi</em> when data for small and young fish are limited. The lengths at which <em>C. gerrardi</em> become selected by commercial line fishing differed among regions, potentially reflecting a size-related, westward movement of fish along the south coast to important spawning areas. Different potential conclusions regarding growth and connectivity for <em>C. gerrardi</em>, depending on which growth model was applied, highlight the importance of considering fishing-related effects when estimating growth of exploited fish species.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107632"},"PeriodicalIF":2.3,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-16DOI: 10.1016/j.fishres.2025.107627
Edward V. Camp , William Pine , William R. Casola , Emilee D. Benjamin , Chad Palmer , Kotryna Klizentyte , Kai Lorenzen
The Eastern oyster (Crassostrea virginica) creates reef structures that provide recruitment habitat for many animals, including juvenile oysters. Oyster declines motivate increased habitat restoration and harvest management changes, while infrequent recovery from these declines raises concerns of depensatory dynamics in oyster recruitment. Here we follow a proof-of-concept approach by combining previously published models into a simple simulation to assess alternative assumptions of oyster recruitment and their implications for population collapse, habitat restoration, and fishery management. We found four key results. First, oyster recruitment relationships that are consistent with observations and literature on oyster resilience, collapse potential, and restoration benefits imply depensation. Second, strong depensation may exist but be difficult to detect until population collapse. Third, recovery from collapse requires sufficient habitat restoration. Finally, our results showed that sustaining a robust oyster fishery following collapse and recovery is possible but likely would require full recovery to pre-collapse conditions, and more constrained harvest relative to pre-collapse. Overall, our findings align with a recent and growing literature suggesting depensation may exist in populations of habitat-forming organisms like oysters and provide practical advice for altering restoration and management.
{"title":"Implications of depensation on oyster recruitment, population collapse, restoration, and sustainable fisheries management","authors":"Edward V. Camp , William Pine , William R. Casola , Emilee D. Benjamin , Chad Palmer , Kotryna Klizentyte , Kai Lorenzen","doi":"10.1016/j.fishres.2025.107627","DOIUrl":"10.1016/j.fishres.2025.107627","url":null,"abstract":"<div><div>The Eastern oyster (<em>Crassostrea virginica</em>) creates reef structures that provide recruitment habitat for many animals, including juvenile oysters. Oyster declines motivate increased habitat restoration and harvest management changes, while infrequent recovery from these declines raises concerns of depensatory dynamics in oyster recruitment. Here we follow a proof-of-concept approach by combining previously published models into a simple simulation to assess alternative assumptions of oyster recruitment and their implications for population collapse, habitat restoration, and fishery management. We found four key results. First, oyster recruitment relationships that are consistent with observations and literature on oyster resilience, collapse potential, and restoration benefits imply depensation. Second, strong depensation may exist but be difficult to detect until population collapse. Third, recovery from collapse requires sufficient habitat restoration. Finally, our results showed that sustaining a robust oyster fishery following collapse and recovery is possible but likely would require full recovery to pre-collapse conditions, and more constrained harvest relative to pre-collapse. Overall, our findings align with a recent and growing literature suggesting depensation may exist in populations of habitat-forming organisms like oysters and provide practical advice for altering restoration and management.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107627"},"PeriodicalIF":2.3,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-16DOI: 10.1016/j.fishres.2025.107634
Lucy Coyle, Gaya Gnanalingam
Understanding reproductive parameters such as size at maturity (SAM) and fecundity is critical for the management of fished species as they are direct indicators of reproductive potential and therefore stock health. Rock lobster, Jasus edwardsii, support one of New Zealand’s most valuable inshore fisheries with commercial, recreational and customary significance. Reproduction in J. edwardsii is characterised by size-dependent fecundity, external brooding, and extended larval development, with regional variability in the timing of the reproductive period. This study assessed SAM and fecundity in female J. edwardsii from southern New Zealand, using fisheries-independent field data collected via standardised potting methods between 2021 and 2024. We found a 20 % decline in SAM compared to estimates from 1969. Also, while fecundity was higher across most sizes in 2024, the relationship between size and fecundity has changed since last measured in 1984. Our fecundity estimates utilised a traditional gravimetric approach, however we also trialled a non-invasive method for estimating fecundity and found no significant difference between the methods, supporting its utility for future monitoring with reduced impact on individuals. Results presented suggest that there has been a shift in key reproductive indicators over a 50-year period, which may have been driven by fishing pressure in a region where the commercial minimum legal size has remained low. These findings highlight the importance of shifting management strategies toward rebuilding reproductive capacity and population structure in a valuable fishery to ensure long-term persistence and enhance stock resilience into the future.
{"title":"Changes in fecundity and size at maturity of rock lobster Jasus edwardsii in southern New Zealand – A cause for concern in the face of environmental change","authors":"Lucy Coyle, Gaya Gnanalingam","doi":"10.1016/j.fishres.2025.107634","DOIUrl":"10.1016/j.fishres.2025.107634","url":null,"abstract":"<div><div>Understanding reproductive parameters such as size at maturity (SAM) and fecundity is critical for the management of fished species as they are direct indicators of reproductive potential and therefore stock health. Rock lobster, <em>Jasus edwardsii,</em> support one of New Zealand’s most valuable inshore fisheries with commercial, recreational and customary significance. Reproduction in <em>J. edwardsii</em> is characterised by size-dependent fecundity, external brooding, and extended larval development, with regional variability in the timing of the reproductive period. This study assessed SAM and fecundity in female <em>J. edwardsii</em> from southern New Zealand, using fisheries-independent field data collected via standardised potting methods between 2021 and 2024. We found a 20 % decline in SAM compared to estimates from 1969. Also, while fecundity was higher across most sizes in 2024, the relationship between size and fecundity has changed since last measured in 1984. Our fecundity estimates utilised a traditional gravimetric approach, however we also trialled a non-invasive method for estimating fecundity and found no significant difference between the methods, supporting its utility for future monitoring with reduced impact on individuals. Results presented suggest that there has been a shift in key reproductive indicators over a 50-year period, which may have been driven by fishing pressure in a region where the commercial minimum legal size has remained low. These findings highlight the importance of shifting management strategies toward rebuilding reproductive capacity and population structure in a valuable fishery to ensure long-term persistence and enhance stock resilience into the future.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107634"},"PeriodicalIF":2.3,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-15DOI: 10.1016/j.fishres.2025.107628
An V. Vu , John Conallin , Zau Lunn , Nyein Chan , Maung Maung Lwin , Nyi Nyi Tun , Ian G. Cowx , Lee J. Baumgartner , Cameron M. Kewish , Michael Akester , Karin E. Limburg
Hilsa shad (Tenualosa ilisha) is an ecologically and economically important fish species in the Indo-Pacific region, yet its migration and spawning behaviour remains poorly in Myanmar. This study investigates hilsa migration and spawning strategies in the Ayeyarwady River using otolith chemistry, including elemental ratios (Sr:Ca, Ba:Ca, Mg:Ca, Mn:Ca) and 87Sr:86Sr isotope signatures. Otoliths from 101 juvenile and adult hilsa collected across the Ayeyarwady River Basin showed that 94 % of hilsa exhibited life histories consistent with anadromy (spawning in freshwater rivers but growing up in the ocean). However, a small subset (6 %) displayed alternative reproductive strategies, likely spawning in higher salinity environments (such as estuarine or coastal areas) without entering rivers. Additionally, hilsa may migrate over 1500 km to the Upper Ayeyarwady from the sea. Additionally, otoliths of juvenile hilsa collected in the Chindwin River, exhibited consistently low Sr:Ca ratios along the core-to-edge profiles, indicating prolonged freshwater residency post-hatching (up to six months). Findings from this study illustrate the predominance of an anadromous life history and the existence of an alternative reproductive strategy, which are essential for adaptive management and conservation of hilsa in Myanmar. Given the species’ trans-boundary distribution and importance in the Indo-Pacific region, effective fishery management requires strengthening regional cooperation to promote sustainable hilsa fisheries in the region.
{"title":"Migration and spawning strategies of hilsa shad (Tenualosa ilisha, Clupeidae) in the Ayeyarwady River revealed by otolith chemistry","authors":"An V. Vu , John Conallin , Zau Lunn , Nyein Chan , Maung Maung Lwin , Nyi Nyi Tun , Ian G. Cowx , Lee J. Baumgartner , Cameron M. Kewish , Michael Akester , Karin E. Limburg","doi":"10.1016/j.fishres.2025.107628","DOIUrl":"10.1016/j.fishres.2025.107628","url":null,"abstract":"<div><div>Hilsa shad (<em>Tenualosa ilisha</em>) is an ecologically and economically important fish species in the Indo-Pacific region, yet its migration and spawning behaviour remains poorly in Myanmar. This study investigates hilsa migration and spawning strategies in the Ayeyarwady River using otolith chemistry, including elemental ratios (Sr:Ca, Ba:Ca, Mg:Ca, Mn:Ca) and <sup>87</sup>Sr:<sup>86</sup>Sr isotope signatures. Otoliths from 101 juvenile and adult hilsa collected across the Ayeyarwady River Basin showed that 94 % of hilsa exhibited life histories consistent with anadromy (spawning in freshwater rivers but growing up in the ocean). However, a small subset (6 %) displayed alternative reproductive strategies, likely spawning in higher salinity environments (such as estuarine or coastal areas) without entering rivers. Additionally, hilsa may migrate over 1500 km to the Upper Ayeyarwady from the sea. Additionally, otoliths of juvenile hilsa collected in the Chindwin River, exhibited consistently low Sr:Ca ratios along the core-to-edge profiles, indicating prolonged freshwater residency post-hatching (up to six months). Findings from this study illustrate the predominance of an anadromous life history and the existence of an alternative reproductive strategy, which are essential for adaptive management and conservation of hilsa in Myanmar. Given the species’ trans-boundary distribution and importance in the Indo-Pacific region, effective fishery management requires strengthening regional cooperation to promote sustainable hilsa fisheries in the region.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107628"},"PeriodicalIF":2.3,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.fishres.2025.107631
Andre E. Punt , Paul Burch , Kristin M. Privitera-Johnson , Pia Bessell-Browne , Geoffrey N. Tuck
Natural mortality (M) is a key parameter in age- and size-structured methods of fish stock assessment because estimates of biomass in absolute terms and relative to reference points are sensitive to its value. M can be pre-specified based on “indirect” methods, estimated with a prior, or estimated without a prior. However, there is an absence of best practice guidelines for how to treat M within stock assessments. Five alternative broad categories of methods for treating M in stock assessments (unconstrained estimation, estimation with a prior, the “lowest plausible” and “highest plausible” values based on indirect methods, and the results of the Hamel-Amax indirect method) are compared for ten stocks in Australia’s Southern and Eastern Scalefish and Shark Fishery using likelihood profiles, retrospective analyses and hindcast skill. There is no method that performs best in all cases. However, the results support a proposed best practice where estimation with a prior should be the default unless evidence such as diagnostics suggests that the population dynamics or the observation model is clearly and substantially mis-specified (e.g., an estimate of M that differs markedly from the mean of a prior based on longevity information) such that estimates of management-related quantities will likely be appreciably in error. It is also appropriate to conduct sensitivity analyses and use decision tables to highlight the effects of incorrectly assumed values of M when substantial mis-specification appears to be present and M is pre-specified using a longevity-based method.
{"title":"Comparison of treatments of natural mortality in integrated assessment models, with reference to fish stocks off southeast Australia: Towards best practices for estimation","authors":"Andre E. Punt , Paul Burch , Kristin M. Privitera-Johnson , Pia Bessell-Browne , Geoffrey N. Tuck","doi":"10.1016/j.fishres.2025.107631","DOIUrl":"10.1016/j.fishres.2025.107631","url":null,"abstract":"<div><div>Natural mortality (<em>M</em>) is a key parameter in age- and size-structured methods of fish stock assessment because estimates of biomass in absolute terms and relative to reference points are sensitive to its value. <em>M</em> can be pre-specified based on “indirect” methods, estimated with a prior, or estimated without a prior. However, there is an absence of best practice guidelines for how to treat <em>M</em> within stock assessments. Five alternative broad categories of methods for treating <em>M</em> in stock assessments (unconstrained estimation, estimation with a prior, the “lowest plausible” and “highest plausible” values based on indirect methods, and the results of the Hamel-Amax indirect method) are compared for ten stocks in Australia’s Southern and Eastern Scalefish and Shark Fishery using likelihood profiles, retrospective analyses and hindcast skill. There is no method that performs best in all cases. However, the results support a proposed best practice where estimation with a prior should be the default unless evidence such as diagnostics suggests that the population dynamics or the observation model is clearly and substantially mis-specified (e.g., an estimate of <em>M</em> that differs markedly from the mean of a prior based on longevity information) such that estimates of management-related quantities will likely be appreciably in error. It is also appropriate to conduct sensitivity analyses and use decision tables to highlight the effects of incorrectly assumed values of <em>M</em> when substantial mis-specification appears to be present and <em>M</em> is pre-specified using a longevity-based method.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107631"},"PeriodicalIF":2.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-12DOI: 10.1016/j.fishres.2025.107626
Michael A. Spence, Thomas I.J. Bartos, Michael J. Thomson, Robert B. Thorpe
Many jurisdictions have a legal requirement to manage fish stocks at maximum sustainable yield (MSY), while following the precautionary approach (PA). Generally, MSY is calculated on a single-species basis; however, due to species interactions, there is no guarantee that fishing multiple stocks at their precautionary single-species MSY level will lead to all stocks being precautionary or even at fished MSY. This suggests the necessity of a multispecies MSY (MMSY). Although there are several definitions of MMSY, there is no agreed best definition. At least two approaches have been suggested, firstly a community maximum yield, either with or without integrated risk measures designed to prevent stock-depletion, and secondly, defining MMSY in terms of a set of simultaneous single-species MSYs. Here we adopt the second interpretation which allows for the implementation of MMSY without requiring new concepts when combined with multispecies PA to safeguard stock structure. We extend single-species definitions of MSY and PA to give two potential definitions of precautionary MMSY. In the first we constrain the search for MMSY to fishing mortalities that follow the multispecies PA and in the second we find the closest fishing mortality that follows the multispecies PA to the unconstrained MMSY. We demonstrate these definitions using a case study of 9 stocks in the North Sea and compare them with single-species and non-precautionary equivalents. We propose that the second definition be precautionary MMSY as it is more robust than the first.
{"title":"Extending single-species maximum sustainable yield and precautionary approaches to account for species interactions","authors":"Michael A. Spence, Thomas I.J. Bartos, Michael J. Thomson, Robert B. Thorpe","doi":"10.1016/j.fishres.2025.107626","DOIUrl":"10.1016/j.fishres.2025.107626","url":null,"abstract":"<div><div>Many jurisdictions have a legal requirement to manage fish stocks at maximum sustainable yield (MSY), while following the precautionary approach (PA). Generally, MSY is calculated on a single-species basis; however, due to species interactions, there is no guarantee that fishing multiple stocks at their precautionary single-species MSY level will lead to all stocks being precautionary or even at fished MSY. This suggests the necessity of a multispecies MSY (MMSY). Although there are several definitions of MMSY, there is no agreed best definition. At least two approaches have been suggested, firstly a community maximum yield, either with or without integrated risk measures designed to prevent stock-depletion, and secondly, defining MMSY in terms of a set of simultaneous single-species MSYs. Here we adopt the second interpretation which allows for the implementation of MMSY without requiring new concepts when combined with multispecies PA to safeguard stock structure. We extend single-species definitions of MSY and PA to give two potential definitions of precautionary MMSY. In the first we constrain the search for MMSY to fishing mortalities that follow the multispecies PA and in the second we find the closest fishing mortality that follows the multispecies PA to the unconstrained MMSY. We demonstrate these definitions using a case study of 9 stocks in the North Sea and compare them with single-species and non-precautionary equivalents. We propose that the second definition be precautionary MMSY as it is more robust than the first.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107626"},"PeriodicalIF":2.3,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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