Pub Date : 2026-01-01DOI: 10.1016/j.fishres.2026.107649
Sónia Seixas , Alexandra Baeta , João C. Marques
This study explores the feeding ecology of Octopus vulgaris in the Cascais region through a combined approach of long-term prey monitoring and stable isotope analysis. Over several months, we worked with local fishermen to observe and record prey items found in octopus pots and those carried by octopuses at the time of capture. These field observations enabled the identification of key prey species, which were subsequently analysed isotopically to estimate their contribution to the octopus diet. The results show that Atrina fragilis is the main prey, making up about 70 %, followed by Polybius henslowii (18 %), with Cymbium olla and Cepola macrophthalma contributing smaller amounts. Our findings highlight the limitations of traditional stomach content analysis, which often underestimates soft-bodied or highly digested prey, and emphasise the importance of isotopic methods to provide a more comprehensive and long-term view of trophic interactions. This integrated approach enhances our understanding of O. vulgaris feeding strategies and has significant implications for ecological research and the sustainable management of fisheries in the region.
{"title":"Integrating prey monitoring and stable isotope analysis to assess the diet of Octopus vulgaris in Portuguese coastal waters","authors":"Sónia Seixas , Alexandra Baeta , João C. Marques","doi":"10.1016/j.fishres.2026.107649","DOIUrl":"10.1016/j.fishres.2026.107649","url":null,"abstract":"<div><div>This study explores the feeding ecology of <em>Octopus vulgaris</em> in the Cascais region through a combined approach of long-term prey monitoring and stable isotope analysis. Over several months, we worked with local fishermen to observe and record prey items found in octopus pots and those carried by octopuses at the time of capture. These field observations enabled the identification of key prey species, which were subsequently analysed isotopically to estimate their contribution to the octopus diet. The results show that Atrina fragilis is the main prey, making up about 70 %, followed by <em>Polybius henslowii</em> (18 %), with <em>Cymbium olla</em> and <em>Cepola macrophthalma</em> contributing smaller amounts. Our findings highlight the limitations of traditional stomach content analysis, which often underestimates soft-bodied or highly digested prey, and emphasise the importance of isotopic methods to provide a more comprehensive and long-term view of trophic interactions. This integrated approach enhances our understanding of O. vulgaris feeding strategies and has significant implications for ecological research and the sustainable management of fisheries in the region.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107649"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976623","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 : 2026-01-01DOI: 10.1016/j.fishres.2026.107648
Topi K. Lehtonen , Lari Veneranta , Oliver Bitz , Daniel Fischer , Miika Tapio , Tuomas Leinonen
Fisheries management units—i.e. ’stocks’—frequently match poorly with biological variation. This mismatch poses a management challenge particularly when within-species units differ in their resilience to harvesting. It is therefore essential to both identify the distinct biological units and adjust fishing pressure accordingly. In the northern Baltic Sea, the European whitefish (Coregonus lavaretus) has two ecotypes, anadromous and sea-spawning, harvested primarily with gillnets. The former is endangered due to river connectivity issues and fishing pressure, while the latter is faring better. However, the key elements of effective management, accurate stock component identification and stock-component-specific fishing pressure adjustment, have not been assessed in this mixed-stock fishery. To address this knowledge gap, we compared ecotype identification methods and examined how fishing depth, season, and gillnet mesh size influence the whitefish catch composition. First, we assessed how well the ecotypes could be identified using phenotypic traits (gill rakers and growth) and genetic data (SNP genotyping). While both approaches were useful, many individuals exhibited intermediate characteristics and were not reliably identified, with phenotypic and genetic identification approaches agreeing only moderately. The prevalence of individuals with intermediate traits may reflect past stocking practices, habitat degradation, or inherently inconsistent homing behaviour. Nevertheless, we caught a higher share of sea-spawner-like individuals from deeper waters, earlier in the season, and with gillnets of smaller mesh size. The fact that it was possible to markedly affect the catch composition suggests that spatial and temporal fishing regulations have potential in the management of whitefish mixed-stock fisheries.
{"title":"Challenges in mixed-stock fishery management: The case of the European whitefish in Kvarken, northern Baltic Sea","authors":"Topi K. Lehtonen , Lari Veneranta , Oliver Bitz , Daniel Fischer , Miika Tapio , Tuomas Leinonen","doi":"10.1016/j.fishres.2026.107648","DOIUrl":"10.1016/j.fishres.2026.107648","url":null,"abstract":"<div><div>Fisheries management units—i.e. ’stocks’—frequently match poorly with biological variation. This mismatch poses a management challenge particularly when within-species units differ in their resilience to harvesting. It is therefore essential to both identify the distinct biological units and adjust fishing pressure accordingly. In the northern Baltic Sea, the European whitefish (<em>Coregonus lavaretus</em>) has two ecotypes, anadromous and sea-spawning, harvested primarily with gillnets. The former is endangered due to river connectivity issues and fishing pressure, while the latter is faring better. However, the key elements of effective management, accurate stock component identification and stock-component-specific fishing pressure adjustment, have not been assessed in this mixed-stock fishery. To address this knowledge gap, we compared ecotype identification methods and examined how fishing depth, season, and gillnet mesh size influence the whitefish catch composition. First, we assessed how well the ecotypes could be identified using phenotypic traits (gill rakers and growth) and genetic data (SNP genotyping). While both approaches were useful, many individuals exhibited intermediate characteristics and were not reliably identified, with phenotypic and genetic identification approaches agreeing only moderately. The prevalence of individuals with intermediate traits may reflect past stocking practices, habitat degradation, or inherently inconsistent homing behaviour. Nevertheless, we caught a higher share of sea-spawner-like individuals from deeper waters, earlier in the season, and with gillnets of smaller mesh size. The fact that it was possible to markedly affect the catch composition suggests that spatial and temporal fishing regulations have potential in the management of whitefish mixed-stock fisheries.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107648"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925289","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}
Monitoring the survival rates of stocked fish is important for the success of stocking programs. Stocked fish reared in artificial environments may exhibit reduced performance until they adapt to the natural environment, potentially leading to a high loss rate immediately after stocking. In this study, we conducted high-frequency tracking of farmed Japanese eels Anguilla japonica stocked into the Fukada River (small size, no previous stocking) and the Amikake River (larger size, previous stocking) in Japan, starting from the first day after stocking using a mobile Radio Frequency Identification system. Apparent survival rates of stocked eels including mortality and emigration was estimated using the Cormack–Jolly–Seber (CJS) model with state-space formulations. The CJS model showed that apparent survival rates of stocked eels were lowest during the initial detection survey after stocking (i.e., on the first day in the Fukada River and during the first four days in the Amikake River), and then the rates gradually increased over time. These results suggest that stocked eels experience significant depletion within the initial days following stocking. Emigration and predation were inferred as potential causes of the high loss rate in the initial phase following stocking. Furthermore, the CJS model also showed that smaller stocked eels with high condition factors exhibited higher apparent survival rates. This study highlighted that identifying effective stocking methods to improve post-release survival is essential for enhancing the local catch and population of Japanese eels.
{"title":"Rapid loss rates of farmed Japanese eels stocked into two different rivers","authors":"Kota Takeuchi , Hikaru Itakura , Tatsuhiko Maeda , Seishi Hagihara , Shingo Kimura , Kazuhiko Anraku , Tomonari Kotani , Ryoshiro Wakiya","doi":"10.1016/j.fishres.2025.107647","DOIUrl":"10.1016/j.fishres.2025.107647","url":null,"abstract":"<div><div>Monitoring the survival rates of stocked fish is important for the success of stocking programs. Stocked fish reared in artificial environments may exhibit reduced performance until they adapt to the natural environment, potentially leading to a high loss rate immediately after stocking. In this study, we conducted high-frequency tracking of farmed Japanese eels <em>Anguilla japonica</em> stocked into the Fukada River (small size, no previous stocking) and the Amikake River (larger size, previous stocking) in Japan, starting from the first day after stocking using a mobile Radio Frequency Identification system. Apparent survival rates of stocked eels including mortality and emigration was estimated using the Cormack–Jolly–Seber (CJS) model with state-space formulations. The CJS model showed that apparent survival rates of stocked eels were lowest during the initial detection survey after stocking (i.e., on the first day in the Fukada River and during the first four days in the Amikake River), and then the rates gradually increased over time. These results suggest that stocked eels experience significant depletion within the initial days following stocking. Emigration and predation were inferred as potential causes of the high loss rate in the initial phase following stocking. Furthermore, the CJS model also showed that smaller stocked eels with high condition factors exhibited higher apparent survival rates. This study highlighted that identifying effective stocking methods to improve post-release survival is essential for enhancing the local catch and population of Japanese eels.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107647"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925357","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 : 2026-01-01DOI: 10.1016/j.fishres.2026.107653
J.H. Colonello, F. Cortés, C.D. Álvarez, M.C. Risoli, M.A. Pérez
In response to growing global concern, various international committees and national and regional action plans have emphasized the need for research focused on the conservation and sustainable use of the porbeagle shark. In the Southwest Atlantic, this species is incidentally caught by commercial longline and trawl fleets, with varying intensities depending on the area and type of fishery. This study is based on data collected by scientific observers onboard Argentine trawl freezer and factory vessels operating south of 51°S between 2006 and 2021. It had three main objectives: to estimate the annual bycatch of porbeagle shark; to estimate standardized catch per unit effort as a proxy for regional species density in the Southwest Atlantic Ocean; and to update the annual standardized bycatch index originally developed for the surimi fleet. Porbeagle shark occurrence frequency increased with depth, showing two distinct peaks around 500 and 1200 m. Higher frequencies were recorded east of 64ºW and south of 54ºS, with monthly peaks during the first half of the year, although interannual variation was observed. Occurrence was higher in surimi vessels, particularly when using semi-pelagic gear. The regional standardized porbeagle shark density index fluctuated over the study period without a clear trend, although notable peaks occurred in certain years. Notwithstanding its limitations, this study provides indicators that represent a useful starting point for assessing the status of porbeagle shark populations in the Southwest Atlantic and for contributing to future stock assessments. This information is particularly relevant because it originates from latitudes located farther south within the porbeagle shark’s distribution than those encompassed by other Atlantic datasets. The study area also holds ecological importance as a feeding ground, particularly for mature, pregnant females that remain in the region during summer and autumn before migrating to mid-latitudes.
{"title":"Annual bycatch and regional density of the porbeagle shark Lamna nasus in the austral Southwest Atlantic Ocean","authors":"J.H. Colonello, F. Cortés, C.D. Álvarez, M.C. Risoli, M.A. Pérez","doi":"10.1016/j.fishres.2026.107653","DOIUrl":"10.1016/j.fishres.2026.107653","url":null,"abstract":"<div><div>In response to growing global concern, various international committees and national and regional action plans have emphasized the need for research focused on the conservation and sustainable use of the porbeagle shark. In the Southwest Atlantic, this species is incidentally caught by commercial longline and trawl fleets, with varying intensities depending on the area and type of fishery. This study is based on data collected by scientific observers onboard Argentine trawl freezer and factory vessels operating south of 51°S between 2006 and 2021. It had three main objectives: to estimate the annual bycatch of porbeagle shark; to estimate standardized catch per unit effort as a proxy for regional species density in the Southwest Atlantic Ocean; and to update the annual standardized bycatch index originally developed for the surimi fleet. Porbeagle shark occurrence frequency increased with depth, showing two distinct peaks around 500 and 1200 m. Higher frequencies were recorded east of 64ºW and south of 54ºS, with monthly peaks during the first half of the year, although interannual variation was observed. Occurrence was higher in surimi vessels, particularly when using semi-pelagic gear. The regional standardized porbeagle shark density index fluctuated over the study period without a clear trend, although notable peaks occurred in certain years. Notwithstanding its limitations, this study provides indicators that represent a useful starting point for assessing the status of porbeagle shark populations in the Southwest Atlantic and for contributing to future stock assessments. This information is particularly relevant because it originates from latitudes located farther south within the porbeagle shark’s distribution than those encompassed by other Atlantic datasets. The study area also holds ecological importance as a feeding ground, particularly for mature, pregnant females that remain in the region during summer and autumn before migrating to mid-latitudes.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107653"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925290","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 : 2026-01-01DOI: 10.1016/j.fishres.2025.107623
{"title":"Erratum to Letter to the Editor re: Abass et al. (2024) “The mahseer: The tiger of water-an angler's delight in the Himalayas and the undisputed king of sport fishing” [Fish. Res. 279, 107147]","authors":"","doi":"10.1016/j.fishres.2025.107623","DOIUrl":"10.1016/j.fishres.2025.107623","url":null,"abstract":"","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107623"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022498","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 : 2026-01-01DOI: 10.1016/j.fishres.2025.107646
Andy Manuel Escalante-Domínguez , Ximena Renán , Gabriela Galindo-Cortes , Teresa Colás-Marrufo , Thierry Brulé
Obtaining data on the population structure of Lutjanus analis is crucial, as species with low to moderate growth tend to decline faster with fishing pressure. Even though Lutjanus analis is an economically important species in the southern Gulf of Mexico, age-based life history parameters and the selection of the optimal growth model from three possible (von Bertalanffy, Gompertz, and logistic) were acquired for the first time. Collections were done by the semi-industrial and artisanal fishing fleets from January 2018 to July 2023 (n = 433; FL = 19.0 – 79.3 cm, TW = 0.13 – 9.10 kg). Marginal increment analysis confirmed annulus formation from March to June. Age ranged from 0+ to 28 years, with the most frequent ages between 4 – 5 years. The von Bertalanffy growth model was the most efficient to describe growth (L∞ = 76.08 cm, K = 0.17 yr−1, t0 = −1.57). Estimated lifespan was 16.07 years. There were no statistical differences in growth trajectories between sexes. Nevertheless, age at sexual maturity did differed between males (<1 year) and females (1.6 years). Estimated natural mortality was 0.35 yr−1 decreasing exponentially with age. The results indicate that this species from the southern Gulf of Mexico has moderate growth, long-lived, and early maturity. These factors should be taken into account in stock assessment models, considering time-variable natural mortality.
{"title":"Age-based life history of Lutjanus analis from the southern Gulf of Mexico","authors":"Andy Manuel Escalante-Domínguez , Ximena Renán , Gabriela Galindo-Cortes , Teresa Colás-Marrufo , Thierry Brulé","doi":"10.1016/j.fishres.2025.107646","DOIUrl":"10.1016/j.fishres.2025.107646","url":null,"abstract":"<div><div>Obtaining data on the population structure of <em>Lutjanus analis</em> is crucial, as species with low to moderate growth tend to decline faster with fishing pressure. Even though <em>Lutjanus analis</em> is an economically important species in the southern Gulf of Mexico, age-based life history parameters and the selection of the optimal growth model from three possible (von Bertalanffy, Gompertz, and logistic) were acquired for the first time. Collections were done by the semi-industrial and artisanal fishing fleets from January 2018 to July 2023 (n = 433; FL = 19.0 – 79.3 cm, TW = 0.13 – 9.10 kg). Marginal increment analysis confirmed annulus formation from March to June. Age ranged from 0<sup>+</sup> to 28 years, with the most frequent ages between 4 – 5 years. The von Bertalanffy growth model was the most efficient to describe growth (L<sub>∞</sub> = 76.08 cm, K = 0.17 yr<sup>−1</sup>, t<sub>0</sub> = −1.57). Estimated lifespan was 16.07 years. There were no statistical differences in growth trajectories between sexes. Nevertheless, age at sexual maturity did differed between males (<1 year) and females (1.6 years). Estimated natural mortality was 0.35 yr<sup>−1</sup> decreasing exponentially with age. The results indicate that this species from the southern Gulf of Mexico has moderate growth, long-lived, and early maturity. These factors should be taken into account in stock assessment models, considering time-variable natural mortality.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107646"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925287","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 : 2026-01-01DOI: 10.1016/j.fishres.2025.107610
{"title":"Erratum to Letter to the Editor re: Ryznar, E.R., & Litzow, M.A. (2024): “Predicting the distribution of red king crab bycatch in Bering Sea flatfish trawl fisheries” [Fish. Res. 279. 107158]","authors":"","doi":"10.1016/j.fishres.2025.107610","DOIUrl":"10.1016/j.fishres.2025.107610","url":null,"abstract":"","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107610"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022497","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}
The biological traits of largehead hairtail (Trichiurus japonicus) in the China Seas have undergone pronounced changes, such as smaller body length at age and earlier maturation, which may be attributed to environmental shifts. Consequently, clarifying which environmental variables play a decisive role in the early growth stages of largehead hairtail, along with their impacts, is indispensable for understanding the early life history of this species, and it also holds significant ecological and socio-economic value. To comprehend the variations in early growth of largehead hairtail, we investigated the temporal-scale influences of environmental changes on its early growth. In this study, based on the samples from the East China Sea from 2017 to 2021, the specific relationships between early growth and environmental variables were analyzed by otolith microstructure. Our investigation revealed a notable interannual variability in the early growth of the population. Notably, the sea water temperatures during March and April of 2018 were anomalously lower compared to other years, which corresponded with better growth performance, aided by the reduced Mixed Layer Depth (MLD) during this period. Post-2019, the growth conditions in May were predominantly more conducive for the early growth than in April, leading to a shift in the occurrence of growth peaks to the month of May. This research will provide a foundational understanding of the adaptability of largehead hairtail in the East China Sea in the face of climate change, offering theoretical support for the scientific management of fishery resources.
{"title":"Effects of environmental variables on the interannual variability of early growth of Trichiurus japonicus in the East China Sea","authors":"Fengming Lv, Peng Sun, Guankui Liu, Wenbo Deng, Congxian Chen, Jianchao Li, Yongjun Tian","doi":"10.1016/j.fishres.2026.107652","DOIUrl":"10.1016/j.fishres.2026.107652","url":null,"abstract":"<div><div>The biological traits of largehead hairtail (<em>Trichiurus japonicus</em>) in the China Seas have undergone pronounced changes, such as smaller body length at age and earlier maturation, which may be attributed to environmental shifts. Consequently, clarifying which environmental variables play a decisive role in the early growth stages of largehead hairtail, along with their impacts, is indispensable for understanding the early life history of this species, and it also holds significant ecological and socio-economic value. To comprehend the variations in early growth of largehead hairtail, we investigated the temporal-scale influences of environmental changes on its early growth. In this study, based on the samples from the East China Sea from 2017 to 2021, the specific relationships between early growth and environmental variables were analyzed by otolith microstructure. Our investigation revealed a notable interannual variability in the early growth of the population. Notably, the sea water temperatures during March and April of 2018 were anomalously lower compared to other years, which corresponded with better growth performance, aided by the reduced Mixed Layer Depth (MLD) during this period. Post-2019, the growth conditions in May were predominantly more conducive for the early growth than in April, leading to a shift in the occurrence of growth peaks to the month of May. This research will provide a foundational understanding of the adaptability of largehead hairtail in the East China Sea in the face of climate change, offering theoretical support for the scientific management of fishery resources.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107652"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976621","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 : 2026-01-01DOI: 10.1016/j.fishres.2025.107644
Sekineh Asadi Amiri , Mohammadsam Andi , Abdolali Movahedinia
Fish gender identification plays a vital role in fisheries management, breeding programs, and maintaining population balance. Traditional methods for gender classification are often manual, time-consuming, and dependent on expert knowledge, which limits their accuracy and scalability. Despite major advancements in deep learning, automated fish gender classification has not been widely explored until now. This study introduces a deep learning-based framework for automated fish gender classification for the first time. The proposed architecture is built upon a modified DenseNet121, enhanced with an attention mechanism specifically, a Squeeze-and-Excitation (SE) block to recalibrate feature maps and help the model focus on the most relevant gender-specific features. Additionally, Global Average Pooling (GAP) and two fully connected (Dense) layers are incorporated to improve feature representation and classification performance. Transfer learning with pre-trained ImageNet weights is also employed to fine-tune the model on a dataset of male and female fish images. The attention-augmented DenseNet121 model achieves a classification accuracy of 94.44 %, significantly outperforming conventional methods. This research demonstrates that integrating attention mechanisms with deep neural networks provides a more accurate, efficient, and scalable solution for fish gender classification, supporting both ecological studies and modern fisheries management.
鱼类性别识别在渔业管理、繁殖计划和维持种群平衡中起着至关重要的作用。传统的性别分类方法往往是手工的、耗时的，并且依赖于专家知识，这限制了它们的准确性和可扩展性。尽管深度学习取得了重大进展，但迄今为止，鱼类性别自动分类尚未得到广泛探索。本研究首次引入了一种基于深度学习的鱼类性别自动分类框架。所提出的架构是建立在改进的DenseNet121之上的，特别增强了一个注意机制，一个挤压和激励（SE）块来重新校准特征图，并帮助模型专注于最相关的性别特征。此外，还结合了Global Average Pooling （GAP）和两个完全连接的（Dense）层来提高特征表示和分类性能。使用预训练ImageNet权重的迁移学习也被用于在雄性和雌性鱼图像数据集上微调模型。注意增强的DenseNet121模型实现了94.44 %的分类准确率，显著优于传统方法。该研究表明，将注意力机制与深度神经网络相结合，为鱼类性别分类提供了更准确、高效和可扩展的解决方案，为生态学研究和现代渔业管理提供了支持。
{"title":"Automated fish gender classification from images using an attention-enhanced DenseNet121 model","authors":"Sekineh Asadi Amiri , Mohammadsam Andi , Abdolali Movahedinia","doi":"10.1016/j.fishres.2025.107644","DOIUrl":"10.1016/j.fishres.2025.107644","url":null,"abstract":"<div><div>Fish gender identification plays a vital role in fisheries management, breeding programs, and maintaining population balance. Traditional methods for gender classification are often manual, time-consuming, and dependent on expert knowledge, which limits their accuracy and scalability. Despite major advancements in deep learning, automated fish gender classification has not been widely explored until now. This study introduces a deep learning-based framework for automated fish gender classification for the first time. The proposed architecture is built upon a modified DenseNet121, enhanced with an attention mechanism specifically, a Squeeze-and-Excitation (SE) block to recalibrate feature maps and help the model focus on the most relevant gender-specific features. Additionally, Global Average Pooling (GAP) and two fully connected (Dense) layers are incorporated to improve feature representation and classification performance. Transfer learning with pre-trained ImageNet weights is also employed to fine-tune the model on a dataset of male and female fish images. The attention-augmented DenseNet121 model achieves a classification accuracy of 94.44 %, significantly outperforming conventional methods. This research demonstrates that integrating attention mechanisms with deep neural networks provides a more accurate, efficient, and scalable solution for fish gender classification, supporting both ecological studies and modern fisheries management.</div></div>","PeriodicalId":50443,"journal":{"name":"Fisheries Research","volume":"293 ","pages":"Article 107644"},"PeriodicalIF":2.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884474","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 : 2026-01-01DOI: 10.1016/j.fishres.2025.107641
Eric J. Ward , Melissa A. Head , Kotaro Ono , Kelli F. Johnson , Kristin N. Marshall
Effective monitoring of fish populations is critical for understanding life-history traits such as maturation or growth, which directly impact population dynamics and fisheries management. Long-term monitoring efforts around the world are faced with rising survey costs and a more uncertain future, as environmental variability is projected to increase. Together, these pressures necessitate more efficient sampling designs. In this study, we use information theory (Fisher Information) to evaluate and optimize life-history sampling, focusing on how variation in fish growth or maturation can guide more informed sampling decisions. Fisher Information is closely related to variance, in that samples with higher information result in greater precision. Using life-history parameters from eight commercially important groundfish species assessed on the U.S. West Coast, we develop three case studies illustrating how sampling strategies can be improved using Fisher Information. The first example focuses on estimating maturity ogives in the absence of spatial and temporal variability; our second case study incorporates spatial and temporal variation; and the third adds a second life-history trait (growth) to jointly optimize sampling for maturity. Our results indicate that for informing maturity ogives, Fisher Information is maximized at lengths near the inflection point, and that the range of most informative lengths can shift across space and time due to habitat or environmental variation. When both growth and maturation are considered, optimal sampling windows broaden for some species but remain narrow for others. Our simulation results also show that sampling fish in proportion to Fisher Information, rather than random sampling, can reduce sampling effort by more than 50 % while maintaining or improving the precision of parameter estimates. While the benefits of using Fisher Information are species specific, these findings suggest that adaptive sampling based on Fisher Information can substantially increase the efficiency and effectiveness of monitoring programs, especially under budgetary or logistical constraints.
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