Skin coloration is a major determinant of perceived quality and husbandry value in farmed and ornamental fishes. Across animals, color change also supports communication, defense, and environmental adaptation. Seahorses (Syngnathidae), renowned for camouflage and mimicry, exhibit gradual and stable background-dependent color transformation. Lined seahorses (Hippocampus erectus) altered their body color over several days when exposed to different environments, whereas no detectable color change was observed following the eye-cover procedure during the shorter observation period. This result is compatible with a possible contribution of visual input to background-associated color change, but it does not establish a causal role for visual perception. Integrating comparative genomics and convergence tests across seahorses, reptiles and amphibians, we identify an overlap of convergent, positively selected or rapidly evolving genes. Genes involved in visual circuits, synaptic transmission, and adhesion-dependent cytoskeletal control are prominent in this shared set, with representative loci such as etv1, sv2b, and itgb1bp1, suggesting that these pathways form a conserved regulatory backbone for color modulation. During color change, the eye upregulates visual perception genes, the brain shows shifts in circadian and neural regulatory pathways, and the skin displays reduced melanogenesis alongside signatures of altered pigment transport; yet gene expression profiles among colored morphs remain broadly similar, consistent with a mechanism based on redistribution of existing pigment granules rather than morph-specific synthesis. Together, these results are consistent with a proposed visual–neural–skin framework through which environmental cues may be linked to pigment-cell dynamics, clarify the mechanistic and evolutionary basis of seahorse color plasticity, and suggest that in captivity, carefully designed colored substrates and background structures could be used to steer body coloration in a predictable and welfare-compatible manner.
The expansion of no-take marine reserves (NTMRs) aims to mitigate fisheries declines and support biodiversity. While the effects of NTMRs on biodiversity are clear, the contribution of NTMR data to fisheries models that can inform management remains understudied. Here we conducted a systematic review to (1) synthesise current knowledge on using NTMR data in strategic and tactical fisheries models, (2) highlight knowledge gaps and opportunities for using NTMR data in fisheries modelling, and (3) create a bridge between NTMR monitoring and fisheries modelling. We identify four main opportunities: (1) fish abundances and biomass measured in NTMRs can be used as a reference for unfished populations; (2) data collected inside NTMRs many reduce bias in life history parameter estimates when reserves represent unfished conditions; (3) measuring the export of adult biomass and larvae to fished areas assists in modelling NTMR impacts on fisheries; and (4) data from NTMRs can reveal insights into fish behaviour that has implications for estimating catchability. There are constraints to using NTMR data in fisheries models, including limited application to mobile species, poaching, a lack of older, well-designed, -enforced and -monitored NTMRs, and the costs of maintaining surveys inside NTMRs. Despite these caveats, we find there are many opportunities to use NTMR data in fisheries models. We recommend prioritising research that (1) integrates growth and reproductive life history data into fisheries models, (2) quantifies the effects of predator–prey dynamics on fisheries models; and (3) takes advantage of opportunities to inform catchability estimates from studies of fish behaviour.
Globally, anadromous fish populations are threatened with extinction due to multiple factors, including river impoundments that block migration, widespread alteration of physical habitat, temperature, and flow regimes, commercial and recreational harvest, changes in biological communities, and long-term climate trends. In this synthesis, we describe how physical and biological factors, policy and law, and public resource allocation affect management of spring-run Chinook Salmon (Oncorhynchus tshawytscha) in the Upper Willamette River (UWR), Oregon, USA. Efforts to restore salmon populations often involve trade-offs, for example, water management decisions must account for flood control, agricultural and municipal water use, and management of other species. UWR Chinook Salmon recovery efforts are also governed by multiple laws, policies, and action agencies that in some cases have incongruent objectives. Competing and conflicting objectives, combined with uncertainty regarding the outcomes of proposed management actions, create significant challenges for decision makers. Resource limitations, regulatory constraints, and incongruent objectives have created challenges for managers in the UWR, but opportunities exist for improved adaptive management and collaboration, which could build trust and engagement among stakeholders and ultimately support the successful implementation of decision tools. A suite of decision support tools that have been used in the Willamette River basin and elsewhere across the range of Pacific salmon have the potential to enhance decision processes. These tools can be effective when decision makers and stakeholders commit to long-term, collaborative utilization of the tools for decision making, and when available resources and regulatory environments are conducive to implementation and adaptive refinement of both the decision-support tools and management plans. The general biological and institutional principles discussed for UWR Chinook Salmon in this work apply more generally to populations of anadromous fishes across their range, especially to populations in highly regulated river systems.
Squids, invaluable organisms for humanity’s protein supply and marine ecosystems, face significant challenges due to climate-induced disturbances in their oceanic habitats. Our understanding of the intricate interplay between the potential positive and negative effects of climate change on such opportunists’ population dynamics has been spatially and temporally limited. Here we constructed a suite of species distribution models to generate scenario-based projections of these relationships across four geographically distinct squid stocks in the Pacific Ocean and the Atlantic Ocean spanning from 1900 to 2100 under five socio-economic emission scenarios. Our results indicate that the impact of oceanic physical and biological factors varies by species, which may be attributed to their unique abilities to swim both vertically and horizontally. Based on our historical hindcasts, the modeled CPUE (as a relative abundance index) appears to have maintained stability despite annual fluctuations. Our models suggest that such trends might persist under scenarios of mild climate change in the future. However, under moderate to severe climate scenarios, both poleward migrations and fluctuations in this relative abundance index are expected to intensify, which could be driven by the dynamics of suitable habitats. The modeled manifestations of climate change underscore the imperative to proactively manage squid resources, with a focus on open ocean ecosystem dynamics and global seafood security.
The oceans host indispensable ecosystem processes and services, playing a crucial role in climate regulation and food provision. In addition to well-documented threats such as overexploitation, habitat loss, and pollution, climate change is emerging as a major driver of biodiversity loss in the oceans. Expected impacts include shifts in species distributions, altering marine biodiversity patterns, and affecting regions highly dependent on fisheries. Here, using a systematic literature review and linear mixed models, we examined 1,600 risk projections for 497 commercially exploited marine species to assess the potential of climate mitigation strategies to safeguard fisheries sustainability. We provide the projected changes for all species analyzed. While most species targeted by fisheries are not projected to experience substantial reductions in range size, severe range shifts are expected. A poleward shift was found in 92
The silky shark (Carcharhinus falciformis) is a vulnerable pelagic shark species frequently caught as bycatch in tuna and billfish fisheries worldwide. Due to data limitations, conventional stock assessments are generally not feasible, hindering the evaluation of their population status and the effectiveness of potential conservation and management measures (CMMs). In this study, we applied the Ecological Assessment of Sustainable Impacts of Fisheries (EASI-Fish) approach to quantify the cumulative impact of multiple fisheries on the vulnerability status of the Atlantic silky shark and to evaluate the potential effectiveness of 28 alternative CMMs across major fisheries managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Results showed high uncertainty in the vulnerability status, ranging from “increasingly vulnerable” under uncertainty-explicit assumptions, to “most vulnerable” under precautionary conditions. Industrial longline fisheries contributed most to cumulative fishing mortality, due to their high spatial overlap with the species’ distribution, while other fisheries (purse seine, gillnet, handline) played smaller, but non-negligible roles. Among the CMMs evaluated, avoidance measures (e.g., static temporal closures) produced the largest reductions in vulnerability. Minimization and remediation measures, such as prohibiting wire-leaders in longliners and implementing best handling and release practices in purse seiners, provided additional but more moderate improvements, particularly when combined, supporting a hierarchical and complementary mitigation approach. The analysis identified critical data gaps, particularly in effort, gear efficiency, and selectivity, where targeted research would most improve future assessments, and demonstrated how a spatially explicit multi-fishery framework can support evidence-based conservation advice for the silky shark in the Atlantic Ocean under uncertainty.
Fishery No-Take Zones (FNTZs) are increasingly being used as a spatial management tool to promote marine habitat recovery and enhance the sustainable use of fishery resources. To evaluate their effectiveness in shelf edge and upper continental slope habitats, a characterization of sessile and motile fauna within eleven FNTZs implemented along the Catalan margin was conducted. Surveys were conducted between 2023 and 2024 using Remote Operated Vehicle (ROV) video-transects across two depth ranges (100–300 m and > 300 m), covering both protected and adjacent Control areas. Sessile and motile fauna were analyzed separately, to assess the different responses in organisms with different life strategies. Results revealed that the effects of protection varied across depths and locations. Sessile fauna exhibited significantly higher densities, and diversity in several FNTZs, especially at the shelf edge, while motile fauna displayed less consistent trends. Community analyses showed differences between protected and control sites, with FNTZs hosting more habitat-forming species opposed to motile species which were more represented in Control areas. Despite initial signs of structural differentiation, results indicate that ecological recovery in soft-sediment at this depth remains slow and spatially variable, likely restricted by the habitat physical degradation consequence of decades of trawling. This research provides the first regional-scale, non-destructive assessment of FNTZs effectiveness on Mediterranean soft sediments and establishes critical reference data for future monitoring.
Limited data can challenge assessing fish vulnerability to overfishing. In response to this challenge, risk assessment methods such as Productivity-Susceptibility Analysis (PSA) are commonly used tools to assess fish vulnerability. PSA measures vulnerability based on life-history traits, catchability and current management of species. This method has been applied in fisheries throughout the world using various forms of parametrization. Traditionally, the intrinsic growth rate of populations (r) is a notable productivity attribute as it theoretically integrates many of the other life-history attributes, yet it is often used alongside the other attributes instead of replacing them. This study assesses species vulnerability based on alternative assumptions regarding the use of r. To do this, we employ a novel PSA approach using meta-analytical attribute estimates to score productivity probabilistically based on prediction densities to account for uncertainty. This approach was used to estimate fish vulnerability across 185 species in three cases of artisanal bottom-set gillnetting in Brazil. Including or excluding r while using other attributes resulted in no difference in vulnerability outcomes. Using r alone as productivity resulted in slightly higher contrast in vulnerability scores compared to using other attributes, with regression R2 between study areas varying from 0.64 to 0.82. In all cases, most species were classified as low vulnerability (50
Marine protected areas (MPAs) are vital for conserving marine biodiversity and managing fishery resources. Ecological connectivity, defined as the interconnection between populations, communities, ecosystems, or habitats through the exchange of genes, organisms, nutrients, and energy, is a key consideration in MPA evaluation and design. Focusing on three commercially and ecologically important migratory fish species with contrasting life histories—the estuarine-dependent Coilia mystus, the nearshore Harpadon nehereus, and the long-distance migratory Larimichthys crocea, we assessed climate-change impacts on ecological connectivity in MPAs of the Yangtze River estuary and adjacent waters using habitat suitability, corridor resistance, electric current density, and pinch-point metrics. We predicted the current and future suitable habitats of the target species and then transformed these projections into resistance surfaces to identify least-cost ecological corridors and key migration pinch points under current and future scenarios. The results show that C. mystus is projected to experience the most severe habitat loss, consistent with its strong dependence on estuarine mixing zones and narrow tolerance to physicochemical changes. In contrast, L. crocea is projected to expand overall, driven by warming temperatures broadening thermally suitable habitat northward. H. nehereus shows an intermediate response, with expanding suitable area but declining habitat quality. Under future climate scenarios, electric current density between MPAs is expected to decrease for C. mystus but increase for H. nehereus and L. crocea. Corridor resistance is projected to increase for C. mystus under most future scenarios, indicating greater migration difficulty, whereas H. nehereus and L. crocea generally show reduced resistance and improved connectivity, particularly in the northern Yangtze River estuary, although H. nehereus shows a slight increase under SSP126-2100. Pinch-point areas are expected to decrease for L. crocea, remain stable for H. nehereus, and increase for C. mystus. Overall, climate change is projected to reshape MPA connectivity in a species-specific manner, reducing connectivity for C. mystus but generally enhancing connectivity for H. nehereus and L. crocea. These findings reveal that the current MPA network may provide declining protection for estuarine-dependent species while offering increasing coverage for thermally responsive offshore species, highlighting the need for adaptive, connectivity-informed MPA network redesign that prioritizes persistent multi-species bottleneck corridors and anticipates climate-driven northward habitat shifts.
The spatiotemporal distribution of interactions with industrial fisheries remains poorly understood for many incidentally caught species, largely due to data limitations such as sparse observer coverage and biases associated with zero-inflation. Here, we analyze 18 years (2002–2019) of Japanese longline observer data to identify seasonal high likelihood areas for turtle bycatch, using a zero-inflated negative binomial model based on stochastic partial differential equations (SPDE) combined with hotspot analysis. This framework allows us to extract meaningful patterns from the first and fourth quarters of each year to generate spatially explicit estimates of relative leatherback density and potential bycatch interactions. Our results reveal that bycatch hotspots occur predominantly near the African coast in the first quarter and extend from the African coast across the North Atlantic, reaching as far west as Central America in the fourth quarter. Seasonal differences in estimated densities were more pronounced than interannual fluctuations, aligning with known migratory behaviors of leatherbacks. These findings underscore the importance of season-specific conservation strategies such as time-area closures or dynamic bycatch avoidance measures, providing actionable spatial and seasonal hotspot maps that could inform the design and timing of mitigation measures. More broadly, although our approach was not able to generate statically robust results for situations of extreme data paucity (quarters 2 and 3 in the Japan data), it offers a practical solution and additional tool for robust analyses under most data-limited conditions and enhances evidence-based conservation planning in marine ecosystems.
Parasites play a critical yet understudied role in Arctic ecosystems, particularly within key subsistence species such as Arctic char (Salvelinus alpinus). As the Arctic undergoes rapid climate-driven change, establishing baseline parasite biodiversity is essential for monitoring ecological shifts and anticipating emerging health and conservation concerns. This study provides the most comprehensive assessment to date of Arctic char parasites in the North American Arctic by integrating a systematic literature review with new empirical data from 378 Arctic char collected across five Nunavut areas (2020–2024). The literature review (30 studies, 1956–2024) documented 67 parasite taxa—48 identified to species—with helminths (nematodes, cestodes, trematodes, acanthocephalans) dominant. Overall, 82
In many intensively managed fisheries, hatchery stocks are initially derived from wild populations, and even after multiple generations of aquaculture breeding, the degree of divergence is often insufficient to result in clearly defined genetic boundaries. Under such conditions, large-scale stock enhancement and frequent escape of cultured individuals create substantial challenges for fisheries assessment by obscuring individual origin in natural catches. Here, we present a streamlined genetic framework for identifying hatchery-origin individuals within natural-catch Larimichthys crocea, a species that has experienced extensive aquaculture development and long-term enhancement releases. The framework integrates a small panel of highly informative SNPs with a multilocus, genotype-based classification strategy that explicitly accounts for incomplete genetic differentiation. Individuals are grouped into high-confidence hatchery-origin, high-confidence wild, and an intermediate genotype class with quantified residual uncertainty, which can be further refined using mitochondrial haplotypes. Validation using individuals of known genetic background demonstrated full concordance for high-confidence genotype classes, while intermediate genotypes showed partial overlap between hatchery and wild backgrounds. Because intermediate genotypes occurred at low frequency in natural populations, the expected misclassification probability for randomly sampled individuals was therefore approximately 0.46
Seasonal variation in environmental conditions profoundly influences host-microbe interactions and nutrient dynamics in marine invertebrates. This study investigated the seasonal changes in body wall nutritional components and gut microbiota of the sea cucumber Apostichopus japonicus in a marine ranching system. Significant seasonal fluctuations were observed in crude protein, lipid content, and key fatty acid and amino acid profiles, with autumn identified as a peak phase for nutrient accumulation. High-throughput 16S rRNA sequencing revealed pronounced shifts in gut microbiota diversity and community composition across seasons, with Proteobacteria and Bacteroidetes as dominant phyla. Co-occurrence network and neutral model analyses indicated that microbial community assembly was primarily governed by stochastic processes, particularly ecological drift and dispersal limitation. Strong correlations between specific microbial taxa and host fatty acids or amino acids suggest that gut microbes actively participate in host metabolic regulation, especially under thermal and nutritional stress. These findings provide new insights into host-microbiota interactions and ecological adaptation mechanisms in sea cucumbers, with implications for sustainable aquaculture management.
Migratory marine species are vital to ecosystem health and fisheries stability, yet their effective conservation is hindered by a mismatch between static protected areas and their dynamic migrations, as well as by anthropogenic pressure. Even advanced systematic conservation planning often relies on averaged data, overlooking spatiotemporal variations in habitat connectivity and risk. Here, we develop a generalizable framework integrating dynamic habitat connectivity with the spatiotemporal heterogeneity of fishing pressure, shifting focus from static locations to ecological processes. The framework combines machine-learning biomass predictions, circuit-theory connectivity modeling, and Bayesian spatiotemporal analysis of human pressure. Applied to the small yellow croaker (Larimichthys polyactis) in the Southern Yellow Sea and East China Sea, the framework captured seasonal migrations, revealing critical connectivity areas that shift from the nearshore waters of the Yangtze River Estuary in spring to offshore feeding and overwintering grounds. Fishing pressure was consistently elevated nearshore and increased over the study period in the Southern Yellow Sea. There was a pronounced spatiotemporal mismatch between the coverage of existing protected areas and areas at high risk of connectivity loss. In spring and winter, coverage of high-risk areas by existing protected areas was only 52.0
Understanding early life-history dynamics is essential for identifying spawning and nursery habitats, estimating larval survival, and improving recruitment predictions in fisheries management. We synthesized Pacific studies of larval istiophorid billfishes to examine spatial structure, habitat associations, feeding constraints, and early survival using individual participant data (IPD). Ten studies met stringent inclusion criteria—spatially disaggregated sampling with capture dates and larval length or age estimates—yielding IPD for approximately 900 larvae, most collected between 1928 and 1970. Numerous additional studies reported thousands of larvae but lacked sufficient spatial or biological resolution for quantitative analysis. Spatial analyses were consistent with non-random larval associations with localized, ephemeral habitats rather than basin-wide uniformity. Environmental data indicated relatively narrow temperature and salinity ranges associated with larval occurrence, consistent with habitat filtering during early development. Length–age relationships were used to estimate larval age and infer candidate spawning regions, including areas associated with seamounts and island systems. A mechanistic suction-feeding framework linking larval morphology to ambient current velocity indicated size-dependent hydrodynamic constraints likely to influence feeding success and survival during ontogeny. Catch-curve analysis generated exploratory estimates of larval survivorship, constraining early-life mortality relevant to recruitment dynamics. Despite limitations inherent to historical datasets—including uncertainty in species identification, measurement precision, and sampling heterogeneity—this synthesis establishes a quantitative baseline for evaluating putative spawning-habitat quality, developing larval-based indices of adult abundance, and guiding future sampling, conservation, and management of Pacific istiophorid billfishes.
Inland recreational fishing (IRF) is crucial for creating economic value, employment opportunities and nutritional supplementation. Globally, research on IRF suffers from data scarcity and insufficient attention to spatial differentiation. Elucidating such spatial patterns is essential for identifying ecological pressure hotspots and informing spatially targeted management strategies. This study integrates enterprise business registration data, geographic point-of-interest data, and angling app data, using spatial statistical models to analyze the spatial differentiation of IRF in China. The analysis focuses on the characteristics and spatial distribution of fishing sites, stocked fish species, angling activity levels, and associated leisure services. Key findings reveal: (1) IRF sites exhibits an “east-dense, west-sparse, multi-core clustering” pattern, with 92.99
Investigating the patterns and drivers of different diversity facets enhances our understanding of species distributions and has the potential to inform conservation strategies. However, only a few studies have explored how phylogenetic diversity relates to multiple ecogeographical processes at broad scales, especially in freshwater ecosystems. Here, we used a comprehensive freshwater fish dataset covering 165 hydrological units spanning four major zoogeographical regions in China and adjacent areas to examine how energy-availability, history, area-heterogeneity and spatial factors drive fish phylogenetic alpha and beta diversity within and among study regions. Our results showed that phylogenetic alpha and beta diversity were generally higher in the climatically more benign and low-altitude East and South Asia regions. In contrast, high-altitude HUs of Central Asia exhibited the lowest phylogenetic alpha diversity but comparatively high beta diversity, whereas the Palearctic region showed the highest phylogenetic alpha diversity and the lowest beta diversity. Moreover, we found higher deviation between taxonomic and phylogenetic beta diversity in Central Asia and Palearctic regions compared to other regions, indicating that lineage turnover within these zoogeographical regions predominantly involves closely related taxa. Hierarchical partitioning suggested that present-day phylogenetic diversity patterns of freshwater fish across China and adjacent areas were strongly influenced by climatic and geologic history, while spatial processes became increasingly important in shaping phylogenetic beta diversity at regional scales, where hydrological units experienced similar environmental and historical contexts. These findings highlight the persistent imprint of historical contingencies and spatial structuring on the evolutionary diversity of freshwater fish faunas, emphasizing the need for integrating explicit phylogenetic information into regional conservation and management planning.
The effective monitoring of small-scale fisheries footprint is critical for fisheries management and marine conservation. Yet, this remains challenging due to limited vessel tracking requirements for small boats under 12 m. This study presents the first attempt to combine Multi-Criteria Spatial Analysis (MCSA) and Sentinel-2 remote sensing approaches for mapping small-scale fisheries (SSF) footprint, using Sicily as a case study. The MCSA combined a habitat suitability index, informed by interviews with small-scale fishers across multiple Sicilian ports, with an activity index based on fleet characteristics and distance from the nearest ports. Sentinel-2 remote sensing data provided direct vessel detections using optical imagery processed by Global Fishing Watch, used for the first time in this study to map SSF vessels. A direct comparison between MCSA and Sentinel-2 datasets revealed a significant positive correlation (Spearman’s ρ: 0.43, p < 0.001). Both approaches consistently identified fishing hotspots and coldspots and showed stronger agreement for fishing hotspots (62
Different life history strategies determine how organisms respond to environmental disturbances and may shape the stability and resilience of river ecosystems. To recover fish resources in the Yangtze River, a Ten-Year Fishing Ban has been implemented across the entire basin since 2021. It is under great concern how this ban may impact the life history composition of fish community there. In this study, we collected fish samples from the Yangtze River during 2014–2023 to analyze the variation in life history strategy composition. Our findings revealed that fishes showed the equilibrium-periodic-opportunistic triangular continuum model. From upper to middle reaches, the abundance of periodic strategists increased, whereas equilibrium strategists decreased. In the tributary Chishui River and the affiliated lake Poyang Lake, fish tended to exhibit an opportunistic strategy. It was found that before the fishing ban, opportunistic fish dominated under high fishing pressure due to their rapid reproduction and short lifespans; after the fishing ban, as fishing pressure was removed, species with longer lifespans, higher fecundity, and parental care behaviors began to recover, with the relative abundance of opportunistic fish decreasing from 19.7–70.9
