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24 pages, 3755 KB

Open AccessArticle

Annual and Spatial Variation in the Diet of Juvenile Pacific Cod in Mutsu Bay, Japan

by Anran Dong, Tetsuya Takatsu, Tomoya Ishikawa, Kenta Sasaki and Mitsuhiro Nakaya

Fishes 2026, 11(5), 302; https://doi.org/10.3390/fishes11050302 - 19 May 2026

To evaluate Mutsu Bay as a nursery habitat for Pacific cod (Gadus macrocephalus Tilesius, 1810), we analyzed settled age-0 juveniles collected with a small bottom otter trawl over 10 years. The three stations with the highest juvenile densities were targeted, and prey-specific [...] Read more.

To evaluate Mutsu Bay as a nursery habitat for Pacific cod (Gadus macrocephalus Tilesius, 1810), we analyzed settled age-0 juveniles collected with a small bottom otter trawl over 10 years. The three stations with the highest juvenile densities were targeted, and prey-specific feeding intensity (SCIi), its sum (SCI), and the relative condition factor (Kn) were quantified, followed by examining their relationships with juvenile attributes and environmental variables. Diets varied among stations and shifted ontogenetically from small-sized calanoid copepods to larger planktonic and benthic prey. SCI was highest at stations where juveniles consumed medium-sized plankton (0.1–1.0 mg ind⁻¹), including Calanus pacificus, Mesocalanus tenuicornis, Metridia pacifica, Anomura zoeae, and Euphausiacea furciliae, and lower where other prey dominated. High-SCI individuals were rarely observed, likely reflecting enhanced digestion at high temperatures near the upper habitat limit (~12 °C) and consistently low prey density independent of temperature. Kn increased with body size and SCI and tended to be higher in cooler water and closer to the bay mouth, suggesting coupled environmental and physiological constraints. These results suggest that after late May, juveniles may benefit from moving toward the bay mouth, where prey encounter rates are likely higher, including relatively larger prey, which may improve feeding opportunities and condition. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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20 pages, 2315 KB

Open AccessArticle

Age and Growth of Pacific Sardine (Sardinops sagax) off the U.S. Pacific Coast, 2012–2021

by Kelsey C. James, Jonathan M. Walker, Brittany D. Schwartzkopf, Emmanis Dorval and Brad E. Erisman

Fishes 2026, 11(5), 290; https://doi.org/10.3390/fishes11050290 - 14 May 2026

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Abstract

Pacific sardine (Sardinops sagax) are an economically important forage fish in the Northeast Pacific Ocean that undergo large changes in abundance over decadal scales and exhibit high individual variation in somatic growth. Past studies have suggested that somatic growth in Pacific [...] Read more.

Pacific sardine (Sardinops sagax) are an economically important forage fish in the Northeast Pacific Ocean that undergo large changes in abundance over decadal scales and exhibit high individual variation in somatic growth. Past studies have suggested that somatic growth in Pacific sardine may be density-dependent and vary regionally in response to environmental conditions. We analyzed somatic growth in Pacific sardine off the U.S. Pacific Coast during the recent period of low abundance (2012–2021) and compared the results to those of previous studies to evaluate evidence of spatial or temporal variation in growth. Sampled fish (n = 3228) ranged in length from 30 to 291 mm SL and in age from 0 to 9 years and displayed high individual variation in length-at-age and age-at-length. Length-at-age data were best explained by the von Bertalanffy growth model, and sample distribution simulations showed the dataset to be robust and unbiased. Estimated growth parameters (L_∞ = 243, K = 0.795, t₀ = −0.638) were consistent with an opportunistic life history strategy characterized by rapid growth, early maturation, and a short lifespan. While the estimated growth rate (K) was higher than in a previous study conducted during a period of high abundance and indicated that growth may be density-dependent, the parameter estimates from the previous study were influenced by sample distribution bias. Similarly, differences in study region, season, collection method, aging methods, and other factors precluded any definitive conclusions on the source of reported differences in growth patterns among studies. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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22 pages, 1000 KB

Open AccessArticle

Overexploitation of the Atlantic Sharpnose Shark (Rhizoprionodon terraenovae) in Marine Priority Regions of Tamaulipas, Mexico: Implications for Wetland Conservation and Data-Limited Fisheries Management

by Jorge Homero Rodríguez-Castro, Sandra Edith Olmeda-de la Fuente, Jorge Alejandro Rodríguez-Olmeda, Ulises de Jesús Balderas-Mancilla, Juventino Tovar-Ortíz, Jose Antonio Rangel-Lucio and Luis Antonio Vázquez-Ochoa

Fishes 2026, 11(5), 268; https://doi.org/10.3390/fishes11050268 - 30 Apr 2026

Viewed by 505

Abstract

Artisanal fisheries in Mexico frequently operate with limited data, lacking historical catch and effort series. In this context, the population status of the dogfish (Rhizoprionodon terraenovae) was evaluated for the first time in Priority Marine Regions 45–46 and the area of [...] Read more.

Artisanal fisheries in Mexico frequently operate with limited data, lacking historical catch and effort series. In this context, the population status of the dogfish (Rhizoprionodon terraenovae) was evaluated for the first time in Priority Marine Regions 45–46 and the area of influence of the Wetland of International Importance Playa Tortuguera Rancho Nuevo, Tamaulipas, using methods based on size frequencies. Between November 2018 and February 2020, 541 artisanal fishing organisms were analyzed in La Barra del Tordo using FISAT II. The von Bertalanffy growth parameters for combined sexes were: L∞ = 105 cm, k = 0.59 years⁻¹, t₀ = −0.195 years. Total (Z), natural (M) and fishing (F) mortalities were 4.13, 0.467 and 3.22 years⁻¹, respectively. The average exploitation rate (E = F/Z) was 0.78 (95% CI: 0.745–0.805), exceeding the reference point of 0.5 (G) indicating severe overexploitation. The parameters showed biological consistency (Ø′ = 3.81; M/k = 0.79), and natural mortality was within the range reported for the species. This finding, in a priority region for conservation under the regime of the Conservation Sector of the Marine Ecological Management Program, shows the urgent need to implement fisheries management with an ecosystem approach that guarantees the sustainability of the fishery and the integrity of the coastal ecosystem. The study demonstrates that, even with limited data, it is possible to obtain robust estimates to inform management decisions in natural protected areas Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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23 pages, 1231 KB

Open AccessArticle

Synergistic Effects of Multiple Non-Native Species and Phenotypic Plasticity Facilitate the Establishment of Yellow Catfish (Pelteobagrus fulvidraco) in Lake Erhai, a Subtropical Plateau Lake: Trophic Expansion and Robust Body Condition

by Chuanyan Zhong, Zhuanxing Shao, Weile Chu, Jimeng Feng, Jian Shen, Xinze Wang and Xiaowen Long

Fishes 2026, 11(3), 155; https://doi.org/10.3390/fishes11030155 - 8 Mar 2026

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Abstract

The successful establishment of non-native fish often relies on life-history plasticity and opportunistic trophic strategies. This study elucidates the invasion mechanisms of the non-native yellow catfish (Pelteobagrus fulvidraco) in Lake Erhai, a plateau lake in China, by integrating morphometrics, stable isotope [...] Read more.

The successful establishment of non-native fish often relies on life-history plasticity and opportunistic trophic strategies. This study elucidates the invasion mechanisms of the non-native yellow catfish (Pelteobagrus fulvidraco) in Lake Erhai, a plateau lake in China, by integrating morphometrics, stable isotope analysis, and DNA metabarcoding. Our results reveal a “triple mechanism” driving this invasion success. First, the population exhibits significant phenotypic plasticity, manifesting as enhanced somatic growth and superior body condition (mean condition factor: 1.92) and sexually dimorphic growth favoring males. Second, DNA metabarcoding confirms a broad trophic niche dominated by zooplankton (31.70%) and, critically, other non-native fishes (Hypomesus nipponensis and Neosalanx taihuensis), providing strong empirical support for the synergistic effects of multiple non-native species. This predation on high-energy forage fish likely fuels the observed somatic growth and high reproductive output, counteracting the typical size-reduction trade-offs often seen in biological invasions. Third, reproductive assessment indicates a protracted spawning period (spanning at least from spring through summer) and an absolute fecundity (mean: 8471 ± 2194 eggs) consistent with its strategy of producing larger, high-quality eggs, significantly exceeding that of native riverine populations. These findings suggest that P. fulvidraco effectively exploits altered food webs—specifically pre-existing invasive prey—to maximize somatic growth and reproductive output, thereby establishing dominance in the plateau lake ecosystem. Therefore, effective management strategies must go beyond single-species control and prioritize controlling pre-existing invasive forage fish to disrupt the facilitation pathway driven by ecosystem alteration by invasive species. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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18 pages, 1938 KB

Open AccessEditor’s ChoiceArticle

Reproductive Dynamics of the Blonde Ray (Raja brachyura) in Portuguese Waters: Timing, Maturity and Fecundity

by Catarina Maia, Ivone Figueiredo, Bárbara Serra-Pereira, Neide Lagarto, Inês Farias and Teresa Moura

Fishes 2026, 11(1), 61; https://doi.org/10.3390/fishes11010061 - 17 Jan 2026

Viewed by 610

Abstract

Within the Rajidae family, the blonde ray (Raja brachyura) is considered one of the less resilient species to fishing pressure and other anthropogenic pressures, primarily due to its late maturity and large maximum size, which can exceed 120 cm total length. [...] Read more.

Within the Rajidae family, the blonde ray (Raja brachyura) is considered one of the less resilient species to fishing pressure and other anthropogenic pressures, primarily due to its late maturity and large maximum size, which can exceed 120 cm total length. This is the first study to provide comprehensive insights into the reproductive biology of Raja brachyura in the continental waters of Portugal, with insights into its timing, maturity, and fecundity. It was determined that egg-laying occurs from February to November, with a peak observed between April and September. Males were reproductively active throughout the year, with highest proportions of active males observed between January and May. The length at first maturity was estimated at 95.2 cm for females and 90.0 cm for males, corresponding to 85% of the maximum observed length in each sex. The potential fecundity was estimated at 115 follicles per female per year, and evidence suggests that the species has a determinate fecundity. The findings reinforce the appropriateness of current management measures in Portuguese continental waters, namely seasonal closure when overlapping with the peak of the reproductive season (May and June), and provide valuable scientific support for future conservation and management measures. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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18 pages, 2041 KB

Open AccessArticle

Seasonal and Size-Related Variation in Diet Composition and Feeding Strategies of the Robustus Tonguefish, Cynoglossus robustus in the Yeosu Coast, Korea

by Seung Jo Han and Seong Yong Moon

Fishes 2026, 11(1), 50; https://doi.org/10.3390/fishes11010050 - 14 Jan 2026

Viewed by 597

Abstract

This study examined the seasonal and size-related variations in the diet composition and feeding strategies of the robust tonguefish Cynoglossus robustus collected in the Yeosu Coast, Korea, from January to December 2024. Stomach content analysis identified amphipods, polychaetes, and brachyurans as the dominant [...] Read more.

This study examined the seasonal and size-related variations in the diet composition and feeding strategies of the robust tonguefish Cynoglossus robustus collected in the Yeosu Coast, Korea, from January to December 2024. Stomach content analysis identified amphipods, polychaetes, and brachyurans as the dominant prey items. Ontogenetic dietary shifts were evident, with individuals < 25 cm TL feeding mainly on amphipods, whereas larger individuals consumed more polychaetes and brachyurans, indicating a shift toward larger and more energy-efficient prey with growth. Amphipods, with Ampelisca sp. being predominant, were predominant in spring and summer, whereas crabs and polychaetes increased in autumn and winter, respectively. Seasonal variation was attributed to environmental factors and post-spawning feeding recovery. The estimated trophic level (3.22) suggests that C. robustus functions as a mesopredator consuming benthic invertebrates and plays an essential role in energy transfer within the coastal benthic ecosystem. These findings provide fundamental ecological insights into the trophic structure of the coastal ecosystem in the southern sea of Korea and serve as a scientific basis for sustainable fisheries resource management. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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20 pages, 4676 KB

Open AccessArticle

Direct Ageing of South Atlantic Swordfish (Xiphias gladius)

by Pablo Quelle, Isabel Chapela, Paula Pérez-Casal, Arancha Carroceda, María Jaranay, Óscar Gutiérrez, Begoña García, Ana Ramos-Cartelle, Enrique Rodríguez-Marín and Jaime Mejuto

Fishes 2026, 11(1), 37; https://doi.org/10.3390/fishes11010037 - 8 Jan 2026

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Abstract

Studies of swordfish growth provide essential biological parameters for stock assessment and fisheries management, informing both conventional population models and the evaluation of different management strategies. The present study aims to provide insight into the dynamics of the South Atlantic Ocean stock growth [...] Read more.

Studies of swordfish growth provide essential biological parameters for stock assessment and fisheries management, informing both conventional population models and the evaluation of different management strategies. The present study aims to provide insight into the dynamics of the South Atlantic Ocean stock growth patterns. The sampling is the most complete to date in the literature, with a wide geographical distribution and in every month of the year. The analysis included 788 anal fins. Biometric relationships between different anal fin spine measurements and fish size were found. Some variation in the size of annulus one and vascularisation hiding some internal bands was found in larger specimens. Marginal increment ratio (MIR) and edge type analyses showed an annual band formation in the austral winter (July to September), thereby confirming the hypothesis of one annulus formation per year. Growth parameters were calculated using different growth models. The Gompertz model yielded the most reliable parameters (L_∞ = 341 cm LJFL, k = 0.13 yr⁻¹, T = 2.83 yr). The tagging and recapture data corroborated the selected model. Results were compared with other growth curves published. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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28 pages, 4215 KB

Open AccessArticle

Age and Growth of Greater Amberjack (Seriola dumerili) in the Gulf of America

by Debra J. Murie, Daryl C. Parkyn, Geoffrey H. Smith, Jr., Edward Leonard, Amanda Croteau, Robert Allman, Ashley Pacicco, Jessica L. Carroll, Brett J. Falterman and Nicole Smith

Fishes 2025, 10(12), 620; https://doi.org/10.3390/fishes10120620 - 4 Dec 2025

Viewed by 2759

Abstract

Greater amberjack (Seriola dumerili) are large reef fish important in fisheries in the southeastern USA, with the Gulf of America stock unsustainably harvested over most of the past two decades. Its age-based stock assessment and recovery plan depend on age and [...] Read more.

Greater amberjack (Seriola dumerili) are large reef fish important in fisheries in the southeastern USA, with the Gulf of America stock unsustainably harvested over most of the past two decades. Its age-based stock assessment and recovery plan depend on age and growth information. In this study, 7658 greater amberjack were sampled from the west coast of Florida and off Alabama, Mississippi, and Louisiana in the Gulf from 1991 to 2018. Fish were aged using cross-sectioned sagittal otoliths, with accompanying data on their length, sex, location (state), and type of fishery. Overall, the greater amberjack that were landed in the recreational and commercial fisheries were between 2 and 19 years of age, with the majority between 3 and 5 years old (>80%), and were primarily caught using hook-and-line gear (95%). Sex- and state-specific growth differences were evident based on von Bertalanffy growth models, with females significantly larger at age than males in both Florida and Louisiana (which included Mississippi and Alabama due to low sample size), and females in Louisiana larger at age than females in Florida. Sex ratios in the recreational catches of Florida and Louisiana were skewed towards females (>1.5 female per male), especially for fish ≥1000 mm fork length (>2.3 female per male). Accounting for sex-specific and region-specific growth differences may, in part, help to explain the notably high variability in the overall growth model for greater amberjack in the Gulf. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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