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Estuaries include some of the most productive yet anthropogenically impacted marine ecosystems on the planet, and provide critical habitat to many ecologically and economically important marine species. In order to elucidate ecological function in estuaries, we must understand what factors drive community dynamics. Delaware Bay is the third largest estuary in the United States and hosts over 200 species of migrant and resident fishes and invertebrates. The Delaware Division of Fish and Wildlife has conducted two long-term trawl surveys at monthly intervals in Delaware Bay since 1966. The two surveys collect data on environmental conditions, species composition, and number of fishes and macroinvertebrates across different size classes and life histories. Using a suite of multivariate approaches including hierarchical cluster analysis, canonical correlation analysis, and permutational multivariate analysis of variance, we characterized the fish and macroinvertebrate community in Delaware Bay and found that community composition and environmental conditions varied across spatial and seasonal scales. We identified four distinct biogeographic regions, based on environmental conditions and community composition, which were consistent across surveys. We found that the community was driven primarily by gradients in temperature and salinity and that abundant, frequently occurring species in the Bay have well-defined environmental associations. Our work represents the first attempt to use an existing historical survey to better understand how environmental parameters influence diversity and distribution of macrofauna within Delaware Bay, providing insight into how abiotic variables, influenced by climate, may impact the Delaware Bay ecosystem and similar estuarine ecosystems worldwide.

ABSTRACT The size spectrum represents a powerful approach for quantifying the effects of environmental changes from individuals to communities in aquatic ecosystems. However, our understanding of its temporal stability in freshwater ecosystems is still limited. In the present study, we used a size spectrum approach to investigate the responses of 126 lake fish communities to changes in the intensity of three common anthropogenic stressors (i.e., global warming, nutrient loading and biological invasions) in French natural lakes and reservoirs over an average 5‐year time period. Using a backward selection on a full model including all possible effects of stressors on the size spectrum slope, we demonstrated that (i) increasing summer temperature shifted fish abundance towards the largest size classes, resulting in a flatter size spectrum slope and (ii) nutrient loading and biological invasions were associated with a shift towards smaller size classes in natural lakes, while the opposite effect was observed in reservoirs. In addition, these two stressors interacted in determining changes in the size structure of fish communities, complicating what the size spectrum can reveal about changes in stressor intensity during monitoring programs. All predictors accounted for a limited part of the observed changes in size spectra, and further investigations are needed to fully apprehend the interplay between natural and human‐induced drivers of the temporal changes in size spectra in contrasting environmental conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT Environmental temperature shapes the ontogeny of ectotherms by influencing rates of growth and development which can be key determinants of survival. Whereas the escalating impacts of water management on freshwater ecosystems is well documented, the effects of cold‐water releases from dams—which can alter downstream temperatures—remains relatively underexplored but may present novel challenges to endemic ectotherms. Specifically, little is known about how thermal depressions reshape phenotypic and genetic patterns during larval metamorphosis for fishes that evolved in warmwater systems. We assessed the effects of thermal shifts on larval ontogeny of the endangered razorback sucker (Xyrauchen texanus), which evolved in the warm waters of the Colorado River Basin, USA. We hypothesised that development is more sensitive to cold‐water influences than growth and that temperature would influence patterns in gene expression related to development. Our results supported these hypotheses and showed that both wild and laboratory‐reared larvae in slightly cooler temperatures exhibited delayed development, but similar growth compared to larvae reared in warmer conditions. These findings suggest growth and development in early ectotherm life stages can be decoupled, which follows patterns more like the temperature‐size rule than allometric scaling of development by size. We also observed transcriptional differences related to genes associated with stress responses and development in our laboratory‐reared fish; here, gene expression of fish from the coldest conditions at the end of the experiment was more similar to fish reared in warmer temperatures at the midpoint. Our findings suggest that modest temperature reductions can delay ontogeny and alter the transcriptional landscape while not necessarily limiting growth. This finding highlights the need for conservation practitioners to consider cascading impacts that even small temperature reductions can cause in riverine ecosystems. [ABSTRACT FROM AUTHOR]

ABSTRACT Fishes inhabiting the mesopelagic zone of the world's oceans are estimated to account for the majority of the world's fish biomass. They have recently attracted new attention because they are part of the biological carbon pump and have been reconsidered as a contribution to food security. Hence, there is an urgent need to understand how environmental conditions and species interactions shape their assemblages, and how they contribute to the functioning of marine ecosystems. Trait‐based approaches are valuable for addressing these types of questions. However, the biology and ecology of mesopelagic fishes are understudied compared to fishes in shallow and epipelagic waters. Here, we synthesise existing knowledge of traits of mesopelagic fishes and relate them to their role in survival, feeding and growth and reproduction, the key functions that contribute to fitness. Vertical migrations, specialised vision and the use of bioluminescence are among the most striking adaptations to the conditions in the mesopelagic realm. Many traits are interrelated as a result of trade‐offs, which may help to understand selection pressures. While morphological traits are straightforward to observe, major knowledge gaps exist for traits that require frequent sampling, assessment under experimental conditions or age determination. The unique adaptations of mesopelagic fishes need to be included in management strategies as well as fundamental research of the habitat. [ABSTRACT FROM AUTHOR]

Streams provide an array of habitat niches that may act as environmental filters for fish communities. The tropical island of Sulawesi in Indonesia is located in the Wallacea, a region isolated by marine barriers from the Asian and Australian faunas. Primary freshwater fishes are naturally absent in the Wallacea, including Sulawesi's numerous coastal streams. Diadromous species are in contrast species‐rich in the area. The knowledge available on stream fishes in the Wallacea is largely restricted to taxonomic work and studies targeting single species groups, whereas baseline data on fish ecology remain extremely scarce. Such data and a deeper understanding of stream fish ecology are, however, urgently required for purposes such as informed management. We assumed that the stream fish assemblages are dominated by recruitment from the sea and are structured by macro‐ and microhabitat diversity. To test this hypothesis, we quantified the occurrence of individual fishes by point abundance electrofishing at 33 streams across Sulawesi. The 4632 fishes obtained represent 58 species out of 24 families. The native fishes recorded are mainly amphidromous (34 species), euryhaline (five species), and catadromous (five species). Gobiiformes make up the vast majority of records, dominated by Oxudercidae (22 species) and Eleotridae (five species). Only two of the species recorded are endemic to Sulawesi, including a single species strictly confined to freshwaters. Ten species, making up 6% of the fishes caught, are not native to Sulawesi. The outlying mean index (OMI) and BIOENV analyses suggest that effects on the scale of macro‐ and microhabitat shape fish assemblage composition, ranging from pH, conductivity, and temperature to current velocity, substrate, canopy cover, and elevation. Habitat niche use of species along the first two OMI axes is complementary and fine‐scaled, covering a wide range of the available habitat space. Juvenile and adult conspecifics share similar habitat niches in most of the cases. Niche breadths overlap, but niche specialization is significant in most of the species. Non‐native fishes link into the assemblages at the margins of habitat space, with substantial niche overlaps to native species. The present findings show that the native fish communities in coastal streams of Sulawesi are largely composed of species depending on access to the sea, highlighting the importance of connectivity down to the estuaries and sea. The ichthyofauna shows a rich diversity in habitat use, and the availability of alternative habitats along the altitudinal gradient provides plausible filters for species establishment. Non‐native fishes are locally abundant, pose substantial potential for changing communities, but are still stocked intentionally. We stress the need for incorporating the need for connectivity and maintained habitat quality into management decisions, and a critical evaluation of stocking activities. [ABSTRACT FROM AUTHOR]

Introduction: The morphological characteristics of eyes in fishes are highly diverse and have evolved to meet the specific visual requirements as per their habitats. These morphological features of eyes are important for researchers and ecologists. The dusky spinefoot (Siganus luridus) is a tropical teleost fish with a laterally flattened body which lives in the Mediterranean Sea. Currently, there are no histological data relating to the Siganus luridus eye. Methods: In this study, the morphology of the Siganus luridus eye was examined to enhance our understanding of its structure and its relationship to fish ecology. Detailed gross and microscopic features were recorded using light and scanning microscopy. Results: The key observations describe the main structural features of the eye of Siganus luridus, specifically, the diameter of the orbit, architecture of three tunics of eye and detailed lens description. The choroid was divided into four layers, and had a rete mirabile, consisting of numerous small blood vessels in the choroidal gland. The tapetum lucidum was observed, which is interesting since Siganus luridus is herbivore and herbivores typically lack a tapetum lucidum. Discussion: These observations shed new light on the intricate eye structure of Siganus luridus and provide valuable insights into its visual abilities and adaptations to the aquatic environment and feeding behavior. [ABSTRACT FROM AUTHOR]

Telemetry techniques are important tools in freshwater fish ecology but are limited by the size of the fish in relation to the size of the electronic tags. The emergence of very small PIT tags (8 mm, mini PIT tags) opens the door to study the individual movement and behavior of small-sized fish species and life stages previously outside the scope of fish telemetry. Although high survival from mini PIT tags have been shown in some groups of fish, suitability assessments are lacking for many taxa, and potential behavioral effects have rarely been evaluated. Here, we evaluate the survival tagging effects in small-sized (35–76 mm) Padanian goby (Padogobius bonelli) implanted with mini PIT tags. PIT-tagging was associated with high survival and tag retention in the tagged fish. No effects of PIT-tagging on volitional swimming activity nor on maximum swimming speed were found. Similar results were obtained implanting larger tags (12 mm) in gobies down to 50 mm in length. Our results indicate that PIT telemetry—using mini PIT tags—is applicable for the study of behavior and movement in small-sized gobies. [ABSTRACT FROM AUTHOR]

Evaluating and integrating local ecological knowledge held by fishers into decision-making processes has the potential to significantly enhance fisheries management. The present study aimed to collect information on fishery practices and to assess the ecological knowledge of local professional fishers through interviews, evaluating its importance in managerial design. As a case study, Polyphytos Reservoir in Greece, which supports substantial fisheries, was selected. During the summer of 2023, thirty-seven interviews were conducted to document fishing efforts, methods, catches, biological information, and fishers' perspectives on lake management, and economic/demographic details. In addition to gathering data on fishing activities, the study seeks to understand fishers' perspectives on managerial deficiencies and necessities, thereby revealing their valuable ecological knowledge. The integration of this knowledge into decision-making processes can empower stakeholders and enhance local participation in fishery management. Ultimately, this approach has the potential to address long-standing conflicts, foster inclusive processes, and ensure better collective outcomes. [ABSTRACT FROM AUTHOR]

Environmental DNA metabarcoding (eDNA metaB) is fundamental for monitoring marine biodiversity and its spread in coastal ecosystems. We applied eDNA metaB to seawater samples to investigate the spatiotemporal variability of plankton and small pelagic fish, comparing sites with different environmental conditions across a coast-to-offshore gradient at river mouths along the Campania coast (Italy) over 2 years (2020–2021). We found a marked seasonality in the planktonic community at the regional scale, likely owing to the hydrodynamic connection among sampling sites, which was derived from numerical simulations. Nonetheless, spatial variability among plankton communities was detected during summer. Overall, slight changes in plankton and fish composition resulted in the potential reorganization of the pelagic food web at the local scale. This work supports the utility of eDNA metaB in combination with hydrodynamic modelling to study marine biodiversity in the water column of coastal systems. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'. [ABSTRACT FROM AUTHOR]

Identification of fish larvae based on morphology is typically limited to higher taxonomic ranks (e.g., family or order), as larvae possess few morphological diagnostic characters for precise discrimination to species. When many samples are presented at any one time, the use of morphology to identify such specimens can be laborious and time‐consuming. Using a reverse workflow for specimen sorting and identification leveraging high‐throughput DNA sequencing, thousands of fish larvae can be DNA barcoded and sorted into molecular operational taxonomic units (mOTUs) in a single sequencing run with the nanopore sequencing technology (e.g., MinION). This process reduces the time and financial costs of morphology‐based sorting and instead deploys experienced taxonomists for species taxonomic work where they are needed most. In this study, a total of 3022 fish larval specimens from plankton tows across four sites in Singapore were collected and sorted based on this workflow. Eye tissue from individual samples was used for DNA extraction and sequencing of cytochrome c oxidase subunit I. We generated a total of 2746 barcodes after quality filtering (90.9% barcoding success), identified 2067 DNA barcodes (75.3% identification success), and delimited 256 mOTUs (146 genera, 52 families). Our analyses identified specific challenges to species assignment, such as the potential misidentification of publicly available sequences used as reference barcodes. We highlighted how the conservative application and comparison of a local sequence database can help resolve identification conflicts. Overall, this proposed approach enables and expedites taxonomic identification of fish larvae, contributing to the enhancement of reference barcode databases and potentially better understanding of fish connectivity. [ABSTRACT FROM AUTHOR]

Deep‐pelagic fishes are among the most abundant vertebrates on Earth. They play a critical role in sequestering carbon, providing prey for harvestable fishing stocks and linking oceanic layers and trophic levels. However, knowledge of these fishes is scarce and fragmented, hampering the ability of both the scientific community and stakeholders to address them effectively. While modelling approaches incorporating these organisms have advanced, they often oversimplify their functional and ecological diversity, potentially leading to misconceptions. To address these gaps, this synthesis examines the biodiversity and ecology of global deep‐pelagic fishes. We review pelagic ecosystem classifications and propose a new semantic framework for deep‐pelagic fishes. We evaluate different sampling methods, detailing their strengths, limitations and complementarities. We provide an assessment of the world's deep‐pelagic fishes comprising 1554 species, highlighting major groups and discussing regional variability. By describing their morphological, behavioural and ecological diversity, we show that these organisms are far from homogeneous. Building on this, we call for a more realistic approach to the ecology of deep‐pelagic fishes transitioning between very different ecological niches during diel vertical migrations. To facilitate this, we introduce the concept of 'diel‐modulated realised niche' and propose a conceptual model synthesising the multiple drivers responsible for such transitions. [ABSTRACT FROM AUTHOR]

The Amazon basin, spanning approximately 540,000 km2, exhibits distinct fluviometric surfaces that differentiate between the dry and rainy seasons. This seasonality, along with hydrological connectivity and the creation of new habitats during the rainy season, significantly promotes the migration, reproduction, and feeding of potamodromous fishes. To estimate the realized niches of species, species distribution models (SDMs) employ the extrapolation of environmental predictors and species occurrence data. Our objective was to compare the spatial distribution of migratory fish species in the Amazon basin using SDMs based on variables characterizing the dry season, rainy season, and a combination of both. All evaluated treatments demonstrated high performance and exhibited different distribution ranges in the applied SDMs, particularly when combining environmental variables with occurrence data during the rainy season. These findings support the hypothesis that spatial distribution is influenced by seasonality. The increased fluviometric surface and enhanced connectivity of the rainy season favor both longitudinal and lateral migrations of Amazonian migratory catfishes. Moreover, the spatial distribution reveals four critical spatial overlap (CSO) regions with higher population densities regardless of the season. These CSOs primarily coincide with the Amazon alluvial plain, which exhibits the highest rates of endemism, species richness, and abundance of organisms. Considering the discontinuous and heterogeneous nature of fluviometry when performing niche modeling processes is pivotal, although SDMs applied in the Amazon generally ignore such regional seasonality. [ABSTRACT FROM AUTHOR]

Fish biologists have long assumed a link between intestinal length and diet, and relative gut length or Zihler's index are often used to classify species into trophic groups. This has been done for specific fish taxa or specific ecosystems, but not for a global fish dataset. Here, we assess these relationships across a dataset of 468 fish species (254 marine, 191 freshwater, and 23 that occupy both habitats) in relation to body mass and fish length. Herbivores had significantly relatively stouter bodies and longer intestines than omni- and faunivores. Among faunivores, corallivores had longer intestines than invertivores, with piscivores having the shortest. There were no detectable differences between herbivore groups, possibly due to insufficient understanding of herbivorous fish diets. We propose that reasons for long intestines in fish include (i) difficult-to-digest items that require a symbiotic microbiome, and (ii) the dilution of easily digestible compounds with indigestible material (e.g., sand, wood, exoskeleton). Intestinal indices differed significantly between dietary groups, but there was substantial group overlap. Counter-intuitively, in the largest dataset, marine species had significantly shorter intestines than freshwater fish. These results put fish together with mammals as vertebrate taxa with clear convergence in intestine length in association with trophic level, in contrast to reptiles and birds, even if the peculiar feeding ecology of herbivorous fish is probably more varied than that of mammalian herbivores. [ABSTRACT FROM AUTHOR]

Channel constructions significantly impact river hydrodynamics, subsequently influencing river ecosystems. To mitigate the negative influence of channel construction and protect fish habitat, it is essential to evaluate fish habitat suitability through the integration of hydrodynamic and habitat models. This study models channel constructions on both the left and right riverbanks to evaluate habitat suitability for Four Major Chinese Carps and the Chinese sturgeon. Initially, flow velocity, water depth and grain size are simulated, followed by an assessment of habitat conditions using the Habitat Suitability Index (HSI) for three distinct construction strategies. Results reveal that constructing channels on the left bank mitigates adverse effects on fish habitat, while constructions on the right bank and both riverbanks lead to habitat degradation. Long‐term effects on riverbed elevation and fish habitat suitability post‐construction were also investigated. Notably, the Four Major Chinese Carps consistently demonstrate greater suitability for the studied river, regardless of flow rate or construction strategies, in comparison to the Chinese sturgeon. These findings underscore diverse responses to channel construction, providing valuable insights for identifying critical habitat areas for endemic fish conservation. This research presents a robust framework for assessing fish ecology in river systems, offering support for conservation decision‐makers. [ABSTRACT FROM AUTHOR]

Purpose: In this study, 143 lutjanid fishes representing four different species from the Northeast coast off Brazil were analyzed for parasites. The aim of the present study is to provide a detailed redescription of R. (I.) vicentei, collected from lutjanid fishes in Brazil, including the first observation of the species using scanning electron microscopy (SEM). Methods: Nematodes found clarified in a crescent glycerin series, were photographed and measured (in mm), and some specimens destined for SEM. The Illustrations were made using an optical microscope with a drawing tube. Results: Nematodes found were identified as Raphidascaris (Ichthyascaris) vicentei, infecting 6.29% of the examined fish. Detailed morphological analysis revealed the following characteristics observed for the first time in this species: labial papillae, narrow lateral alae and the detailed structure of male spicules. These contributions help filling the gaps in the literature and expand the knowledge of this parasite morphology. Conclusions: The presence of R. (I.) vicentei in four lutjanid species may indicates low host specificity, highlighting its adaptability to different hosts. Furthermore, new host records are given. This research provides the most comprehensive morphological description of R. (I.) vicentei to date, generating crucial insights for a better understanding of the parasitic biodiversity off the Brazilian Northeastern coast of Brazil, as well as establishing foundation for future investigations on the ecology and impacts of these parasites in fish populations from this region. [ABSTRACT FROM AUTHOR]

The understanding of the role of fishes in the trophic functioning of estuaries has increased in stages over many decades. It began with qualitative and quantitative dietary studies, mainly from the 1970s onwards, and progressed to more sophisticated stable isotope work towards the end of the 20th Century and into the present. Building on an initial wide array of predominantly single species rather than community dietary studies, our global knowledge of the food and feeding ecology of fishes in estuaries has now progressed to a stage where we can begin to discern patterns and make generalised statements on the nature and role of fish assemblages in the trophic functioning of these systems. In this review we summarize the dominant aspects relating to the trophic ecology of fishes in estuaries, including ontogenetic changes in fish diet and food provision for the nursery function of estuaries, detritus as a direct and indirect driver of the food web, the influence of latitude and habitat type on trophic structuring, predator prey relationships with an emphasis on the importance of invertebrates in fish food chains, the role of stable isotopes in combination with dietary analyses in understanding trophic functioning, and the effects of environmental change and fishing and other human activities on fish food webs in estuaries. Apart from providing an overview of information on the current status of our knowledge on fish trophic ecology in estuaries, this review also identifies important research gaps that need to be filled. [ABSTRACT FROM AUTHOR]

Abstract Restoration methods that seed juvenile corals show promise as scalable interventions to promote population persistence through anthropogenic warming. However, challenges including predation by fishes can threaten coral survival. Coral-seeding devices with refugia from fishes offer potential solutions to limit predation-driven mortality. In an 8-month field study, we assessed the efficacy of such devices for increasing the survival of captive-reared Acropora digitifera (spat and microfragments) over control devices (featureless and caged). Devices with fish-exclusion features demonstrated a twofold increase in coral survival, while most corals seeded without protection suffered mortality within 48 h. Overall, spat faced more grazing and higher mortality compared to microfragments, and upward-facing corals were more vulnerable than side-facing corals. Grazing-induced mortality varied by site, with lower activity in locations abundant in mat-forming cyanobacteria or Scleractinian corals. Many scraping parrotfish were found feeding on or near the seeded corals; however, bites by Scarus globiceps explained the most site-related variation in grazing. Cyanobacteria may be preferred over corals as a nutritional resource for scraping parrotfish—advancing our understanding of their foraging ecology. Incorporating side-facing refugia in seeding devices and deploying to sites with nutrient-rich food sources for fish are potential strategies to enhance coral survival in restoration programs.

Diets of fish larvae may vary within populations and among species and are affected by larval prey availability and foraging capacity. We aimed to describe the diet of fish larvae based on empirical field observations, emphasizing the interaction and organization of the predator–prey network using Auchenipterus osteomystax as a species model. The network showed few interactions (low connectance and modularity) but a nested structure (some items that had fewer records tended to occur together with the most frequent ones), low complementary specialization (the proportions of ingested items tended to be equivalent) and a pattern of segregation (some items tended not to be consumed together) in the use of resources among individuals. Robustness was low when the removal of prey with a higher consumption frequency occurred. The correlation between morphological variables and network attributes was significant and positive for abundance and strength, while the correlation with nested rank was negative. The availability of suitable dietary resources is likely to be the key factor for success and survival in the early stages of development. With changes in morphology during larval development, A. osteomystax showed a generalist position in the network as its predation capacity increased. A new approach to trophic ecology studies of fish larvae incorporating network analysis may help explain the individual characteristics of larvae and assess the pattern of interactions in the population. [ABSTRACT FROM AUTHOR]

The Malaysian Straits, a region of significant ecological and economic importance, face growing challenges due to climate change and human activities. This study aimed to assess fish diversity in the Pulai River, situated within the Malaysian Straits, and examine the impact of urbanization and climate change on these fish populations. Rapid industrialization, urbanization, and agricultural runoff have contributed to habitat degradation and water pollution, exacerbating stressors on marine ecosystems. The objective of this study was to evaluate the current status of fish diversity and understand how environmental changes affect fish diversity. Field surveys were conducted to identify fish species in the Pulai River, with specimens collected and categorized into families. The study identified representatives from families such as Latidae, Serranidae, Lutjanidae, Polynemidae, Sciaenidae, Scombridae, and Carangidae, with Carangidae emerging as the dominant family, accounting for 163 individuals out of a total of 380 fish observed. Diversity indices for the marine fish community were calculated, yielding a diversity index (H′) of 2.02143, a species richness index (R′) of 2.474168, and an evenness index (E′) of 0.877896. The analysis revealed a positive allometric growth pattern (b = 1.73), indicating that as fish length increases, their weight decreases disproportionately. These findings highlight the complex responses of fish populations to environmental stressors such as water quality deterioration and habitat alteration. This study provides valuable insights into the fish ecology of the Malaysian Straits, particularly regarding the impacts of urbanization and climate change on fish diversity. The research supports informed conservation efforts aimed at preserving biodiversity in this ecologically significant region. Recommendations for future studies include ongoing monitoring of fish populations, assessment of specific pollutants and habitat changes, and the implementation of targeted conservation strategies to mitigate the impacts of urbanization and climate change on marine ecosystems in the Malaysian Straits. [ABSTRACT FROM AUTHOR]

Invasive fish species pose several threats to aquatic biodiversity and health, necessitating a good understanding of their biology and ecology. This study aims to understand the biology of invasive fish species collected from a Langat River tributary, Selangor, focusing on their growth, reproduction, and feeding habits. Fish and water samples were collected between March and August 2022. A total of 171 specimens were recorded, including 71, 55, and 45 individuals of Pterygoplichthys disjunctivus, P. pardalis, and Oreochromis sp. The b values for length-weight relationships of P. disjunctivus, P. pardalis, and Oreochromis sp. were 2.79, 2.92, and 2.89, respectively. The mean condition factor for Oreochromis sp. was significantly (p < 0.05) higher than that of the other two species. There were no significant differences between the observed and expected number of males and females for all three species. The females had higher mean gonadosomatic index values compared to males. The mean fecundity for P. disjunctivus, P. pardalis, and Oreochromis sp. were 973 ± 596, 10562 ± 830, and 1052 ± 1068, respectively. The most important stomach contents of the three species were detritus, mineral particles, and diatoms, with a higher proportion of mineral particles found in the diets of P. disjunctivus and P. pardalis. The information on growth patterns, reproductive strategies, and dietary preferences provides valuable insights for controlling their invasion of local rivers. [ABSTRACT FROM AUTHOR]

Yellow-phase Japanese eel Anguilla japonica (Temminck & Schlegel, 1846) utilize a variety of anthropogenically impacted habitats. An extensive understanding of the trophic ecology and habitat use is necessary for the conservation of this endangered species. In this study, we analysed the trophic ecology and feeding habitat of Japanese eels in two small rivers, the Akugawa River and Takase River in Wakayama Prefecture, Japan, dominated by an urban landscape and agricultural land use, respectively. The main goals were to assess the dietary diversity and trophic niche width for eels of two size classes (small eels: ≤ 240 mm total length, large eels: > 240 mm total length) in both habitats. The suitability of both rivers as a feeding habitat for eels was also evaluated. The trophic ecology of eels was inferred based on analysis of carbon and nitrogen stable isotopes, as well as stomach contents. Our results indicated that both rivers are suitable habitats to accommodate this eel, but to varying degrees. The dietary diversity of small eels and trophic niche width differed between rivers, indicating limiting factors, such as insufficient food sources and unfavourable abiotic habitat requirements for small eels in urban rivers. Also, the body condition of eels was found to be lower in the urban Akugawa River than in the Takase River. [ABSTRACT FROM AUTHOR]

It has long been recognized that presence–absence, localisation, size, number and shape of fish scales can be important taxonomic features. Although there are some notes on the relationship between scale morphology and ecological needs, in the absence of a sufficiently large and detailed database, the morphological variability of fish scales and the factors responsible for this variability have not yet been explored in detail. For this reason, a database—which contains the shape and relative size data of 193 freshwater fish taxa of 14 orders, originated from five biogeographic realms—has been built. Database analyses showed that both the scale shape and relative size are proper taxonomic indicators. They can be used to separate higher taxonomic categories (e.g., orders), and by the simultaneous analysis of shape and size scale morphology, we showed increased sensitivity for species‐level detachments. Our results suggest that while both the shape and the size of the fish scales are genetically determined, they are also useful descriptors of the niche segregation (habitat use, flow preference) of close relative species. Scale morphology is a promising additional tool to specify the environmental preferences of lesser known or close relative recent and extinct fish species. And also can be of great help in such cases when only the scales are available for taxonomic identification, for example, in the research field of archaeology and palaeontology. [ABSTRACT FROM AUTHOR]

Dr. Tetsuo Kuwamura, a renowned researcher in fish behavioral ecology, passed away in January 2024. He made significant contributions to the field, particularly in the areas of mating systems, sex change in hermaphroditic fishes, and parental care in reef fishes. Dr. Kuwamura was actively involved in various academic societies and served on the editorial boards of scientific journals. His research on individual identification of fish species and his groundbreaking studies on bidirectional sex change in coral-dwelling gobies and cleaner wrasse have had a lasting impact. Dr. Kuwamura's dedication to sharing his research extended to mentoring students and organizing symposia. His legacy will continue to inspire future generations of researchers. [Extracted from the article]

Scientists increasingly draw on fishers' ecological knowledge (FEK) to gain a better understanding of fish biology and ecology, and inform options for fisheries management. We report on a study of FEK among fishers along the Lower Ucayali River in Peru, a region of exceptional productivity and diversity, which is also a major supplier of fish to the largest city in the Peruvian Amazon. Given a lack of available scientific information on stock status, we sought to identify temporal changes in the composition and size of exploited species by interviewing fishers from 18 communities who vary in years of fishing experience since the mid‐1950s. We develop four FEK‐based indicators to assess changes in the fish assemblage and compare findings with landings data. We find an intensification of fishing gear deployed over time and spatiotemporal shifts in the fish assemblage and reported declines in species weight, which point to a fishing‐down process with declines across multiple species. This finding is reflected in a shifting baseline among our participants, whereby younger generations of fishers have different expectations regarding the distribution and size of species. Our study points to the importance of spillover effects from the nearby Pacaya‐Samira National Reserve and community initiatives to support the regional fishery. Reference to fishers' knowledge also suggests that species decline is likely underreported in aggregated landings data. Despite the dynamism and diversity of Amazonian floodplain fisheries, simple FEK‐based indicators can provide useful information for understanding fishing‐induced changes in the fish assemblage. Fishers hold valuable knowledge for fishery management and conservation initiatives in the region. [ABSTRACT FROM AUTHOR]

The franciscana, Pontoporia blainvillei, is an endemic dolphin off the east coast of South America and is considered the most endangered cetacean in the western South Atlantic. In the present study, we analyzed the muscle tissue of 24 franciscana dolphins found on the coast of Espírito Santo (ES) between 2010 and 2019 to investigate trophic ecology using carbon and nitrogen stable isotope analysis. In addition, 127 prey were analyzed to identify the preferred prey. The most important prey species in the diet of the franciscana dolphins were Trichiurus lepturus, Chirocentrodon bleekerianus, and Pellona harroweri. The franciscana dolphins were grouped into three subareas according to where they were collected throughout the distribution: 1 (North), 2 (Center), and 3 (South). In subarea 1, the preferred prey were Stellifer spp., Isopisthus parvipinnis, and P. harroweri, while in subareas 2 and 3, the prey were similar, changing the order of preference among them (Stellifer spp., T. lepturus, and C. bleekerianus). Finally, we identify two possible ecological groups of franciscana dolphins on the coast of ES, influenced by different carbon sources. Our results improve our understanding of the franciscana dolphin's trophic ecology and habitat use, providing new information and guidelines for species conservation in the region. [ABSTRACT FROM AUTHOR]

Notacanthid fishes constitute a common part of benthopelagic deep‐sea fish communities on seamounts and continental slopes around the world. However, their highly conserved morphology and the usual lack of information on deep‐water organisms make it difficult to appropriately address their biodiversity. A multidisciplinary approach combining morphological data with a DNA‐based species delimitation analyses was used to explore the taxonomy of Notacanthus species. For this purpose, morphological and molecular data were obtained from 43 individuals, and the resulting information was combined with the available data. The results showed the occurrence of Notacanthus arrontei n. sp. from the Iberian Peninsula and highlighted several taxonomic conundrums regarding the Notacanthus genus. For instance, no significant differences were found between Notacanthus indicus and the recently described Notacanthus laccadiviensis, questioning its taxonomic status. Similarly, the result of the species delimitation molecular analysis coincided with previous DNA barcoding studies supporting the snubnosed spiny eel Notacanthus chemnitzii as a species complex that requires further research. Moreover, two unidentified records from the Indian Ocean were confirmed to belong to an unknown species pending formal description, and barcoding data show for the first time the occurrence of the shortfin spiny eel Notacanthus bonaparte in the Australia‐New Zealand area. This research confirms the existence of important gaps in the knowledge of notacanthid fishes and represents a step forward toward a better understanding of their biological diversity. [ABSTRACT FROM AUTHOR]

Recent work has revealed the importance of contemporary evolution in shaping ecological outcomes. In particular, rapid evolutionary divergence between populations has been shown to impact the ecology of populations, communities, and ecosystems. While studies have focused largely on the role of adaptive divergence in generating ecologically important variation among populations, much less is known about the role of gene flow in shaping ecological outcomes. After divergence, populations may continue to interact through gene flow, which may influence evolutionary and ecological processes. Here, we investigate the role of gene flow in shaping the contemporary evolution and ecology of recently diverged populations of anadromous steelhead and resident rainbow trout (Oncorhynchus mykiss). Results show that resident rainbow trout introduced above waterfalls have diverged evolutionarily from downstream anadromous steelhead, which were the source of introductions. However, the movement of fish from above to below the waterfalls has facilitated gene flow, which has reshaped genetic and phenotypic variation in the anadromous source population. In particular, gene flow has led to an increased frequency of residency, which in turn has altered population density, size structure, and sex ratio. This result establishes gene flow as a contemporary evolutionary process that can have important ecological outcomes. From a management perspective, anadromous steelhead are generally regarded as a higher conservation priority than resident rainbow trout, even when found within the same watershed. Our results show that anadromous and resident O. mykiss populations may be connected via gene flow, with important ecological consequences. Such eco‐evolutionary processes should be considered when managing recently diverged populations connected by gene flow. [ABSTRACT FROM AUTHOR]

Understanding the spatiotemporal dynamics of fish species is a central concern in fish ecology and crucial for guiding management and conservation efforts. We constructed a joint species distribution model (JSDM) to simultaneously estimate the spatiotemporal distributions and densities for 21 reef fish species in the southeastern United States (SEUS). The model separately estimates encounter probability and positive density, and accounts for unobserved spatial and spatiotemporal variation using latent factors, where the correlations among species are induced. We applied the model to video data collected from a large‐scale, fishery independent survey. A clustering method was applied to the results of the JSDM to group species based on spatial and spatiotemporal synchrony in encounter probability and positive density. We found strong spatial associations among most of the reef fish species. However, species did exhibit differences in occupied habitat that varied with latitude and/or depth. Within their area of occupied habitat, almost all the species share similar spatial pattern of average density. However, for some species, annual distributions were less correlated with their expected average distributions perhaps due to differing responses to underlying spatiotemporal drivers. Some species show significant declines in abundance, for example, black sea bass, red porgy, and blueline tilefish, while a small number of species showed evidence of shifts in distribution, for example, black sea bass. The findings suggest that spatiotemporal management strategies may be of limited utility for reducing bycatch in these highly mixed reef fisheries due to high spatial correlations in occupied habitat and spatial patterns in density. Species‐specific responses to environmental change may also influence the spatiotemporal structure of reef assemblages. This work suggests management attention is needed for some of the lesser known species as they are showing declining trends in abundance. [ABSTRACT FROM AUTHOR]

Seagrass meadows provide important ecosystem services including carbon sequestration, coastal protection from erosion, and sustained biodiversity and fisheries thereby improving the wellbeing and livelihoods of coastal communities. The erosion of millenary deposits of intertwined roots and rhizomes of Posidonia results in the formation of three-dimensional structures named escarpments that constitute a biogenic reef habitat. However, the natural history of seagrass escarpments including their formation processes and their role as habitat for reef fauna and flora remains poorly understood. This research located and characterized Posidonia oceanica escarpments in Menorca (Balearic Islands) and compared structural complexity and fish assemblages among seagrass escarpments, seagrass meadows, rocky substrates and bare sand with emphasis on its role as habitat and shelter for typical rocky fish. Fish abundance and biomass were similar between seagrass escarpments and rocky substrates (P > 0.05), but significantly lower in seagrass meadows (P < 0.001). The large number of caves found along seagrass escarpments provide shelter to fish, including species only associated to rocky substrates. Seagrass meadows form a rather homogenous habitat within their canopy, but the presence of seagrass escarpments enhances habitat heterogeneity and structural complexity along with fish abundance and biomass at the seascape level. This study enhances understanding on the ecological importance of seagrass escarpments. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) is a promising tool for the continuous monitoring of fish ecology and diversity. However, its potential for describing the phenological activity of fish has rarely been examined. This study aimed to elucidate a linkage between the spatiotemporal distribution of eDNA and the phenology of an amphidromous fish, ayu Plecoglossus altivelis altivelis, in a river in Hokkaido, Japan, which is its northernmost distributional area. A significant positive correlation between eDNA concentration and catch per unit effort of P. a. altivelis in the river confirmed the use of eDNA as a surrogate for the abundance of P. a. altivelis. eDNA of P. a. altivelis was first detected in late April on a sandy beach adjacent to the river mouth. Subsequent to its first detection at the lowest site in the river in early May, eDNA spread throughout the river, indicating the upstream migration of P. a. altivelis. Spawning activity was also represented by a rapid increase in eDNA concentration and its surge at night in the lowest reaches of the river during September and October. These results suggest that upstream migration and spawning primarily commenced when the water temperature reached 10°C and decreased below 20°C, respectively. This observation is consistent with the behavioral responses observed in P. a. altivelis populations from other regions of Japan. Consequently, this study demonstrated that eDNA distribution was closely linked to the phenological activity of P. a. altivelis and that eDNA is a powerful tool for studying the phenology of migratory fishes. [ABSTRACT FROM AUTHOR]

Fisheries science and practice are challenging and require learning, thinking, and sharing across boundaries. The idea of boundary crossing can be described as some form of multiple disciplinarity (e.g. interdisciplinarity, transdisciplinarity), yet that inherently implies that the boundaries crossed are purely disciplinary in nature. After working across various other boundaries (i.e. realms, regions, disciplines, sectors, domains, and knowledge systems) for most of our educational journeys and professional careers, we reflect on our lived experiences with a focus on identifying the benefits and challenges of engaging in different types of boundary crossing. We submit that our personal and professional lives have been enriched by stepping outside of our immediate comfort zones and expertise (i.e. fish ecology) and engaging in active listening and learning with colleagues in other disciplines (i.e. various social sciences) and with stakeholders and policymakers. We have learned much from working across boundaries and encourage others, especially early career professionals, to do the same. What may superficially appear to be a bridge too far may in fact provide novel ways of thinking about a given issue or topic that generates actionable science for sustainable fisheries management and conservation. Many of the projects that we consider to be our greatest successes represent ones that involved boundary crossing, examples of which we provide in this essay. There is a need to prepare the next generation of problem solvers for engaging in boundary crossing and celebrating examples of where such efforts have led to meaningful advances in fisheries science and practice. Ensuring that institutional and cultural barriers that may constrain boundary crossing are addressed while also supporting those doing such work will be key to address the many fisheries and aquatic science challenges of today and tomorrow in both marine and freshwater systems. [ABSTRACT FROM AUTHOR]

Measurements of individual body length at different life stages are critical in understanding fish ecology and evolution. Such data can be obtained via back-calculation from measurements of fish scales or by using the size of the scale as a direct proxy for body length. Using data from Atlantic salmon, we test key assumptions associated with each approach and their implications for investigating how variation in growth earlier in life is associated with age at maturity. The scaling of scale size approximated isometry and was similar among individuals who matured at different ages—validating a key assumption of back-calculation. However, we observed that individuals genetically predisposed to delay maturation have smaller scales for their body size—challenging a key assumption of the "direct scale-size" approach. Depending on the method of body length estimation, the relationship between body length growth earlier in life and age at maturity was observed to differ. Thus, when using scale material to study the relationship between growth and maturation in salmon, we recommend back-calculation and an assumed allometric scaling coefficient. [ABSTRACT FROM AUTHOR]

Bioluminescence is the ability of organisms to emit their own light which can be self-produced in light organs by photogenic cells (photocytes) or symbiotically by bearing cultures of luminous bacteria. Luminous animals are mainly comprised in the ocean, nocturnal coastal shallow-water species or, as the majority of species, inhabiting deep-sea where dim light conditions are optimal for communication by luminous signals. Due to difficult access to species, fisheries of bioluminescent fishes worldwide are rare, mostly for traditional cuisine and fishing bait. Fishes are the only bioluminescent vertebrates and thus their light organs present an astonishing level of complexity for light modulation to adequate light signals for specific ecological roles. Fishes control the output of light intensity using different mechanisms which can be categorized as being under control of hormonal or neuronal pathways. Usually, neural control allows fast and direct response to the photocytes while endocrinal systems allow to control the light produced by bacteria, via manipulation of individual melanophores. In some species, mechanical movement of melanophore-filled tissues by muscular action is under neuronal or hormonal control. Sexual dimorphism of light organs, driven by hormonal regulation during ontogeny, takes a crucial role in communication and reproductive success of these species. [ABSTRACT FROM AUTHOR]

Myctophid fishes represent an important trophic link between zooplankton and higher trophic level predators in the oceanic ecosystems of the Southern Ocean. The Antarctic lanternfish (Electrona antarctica) is one of the most abundant myctophids in the Southern Ocean; however, information on their feeding habits is sparse, representing a key area of uncertainty in efforts to model Southern Ocean food web dynamics. Using a classification tree approach based on stomach content data, we explored the feeding strategy of E. antarctica in the Amundsen and Cosmonaut Seas during January and March 2021, as well as its variation in relation to ontogenetic stage and sampling area. An ontogenetic shift in the feeding preference of E. antarctica was identified in the Cosmonaut Sea: Fish smaller than 48 mm fed on ostracods and copepods, while larger fish (SL > 62 mm) relied primarily on krill. Conversely, there was no ontogenetic shift in the diet of E. antarctica in the Amundsen Sea, and this species feeds almost exclusively on Themisto gaudichaudii. The diet composition of E. antarctica presented spatial differences: Copepods (48% IRI) and krill (24% IRI) were consumed more in the Cosmonaut Sea, while amphipods (91% IRI) were consumed more in the Amundsen Sea. The spatial differences in the prey of E. antarctica are related to the oceanographic environment and the variety of plankton prey in different regions. We determined that the size of E. antarctica, sea surface temperature (SST), latitude, and chlorophyll-a concentration (Chl) were the most important variables associated with dietary differences. When the fish size is larger than 55 mm and the krill abundance is high, E. antarctica mainly preys on krill. Since E. antarctica occupies a key position in the mesopelagic fish community, increased knowledge of the trophic ecology of this fish would contribute to a comprehensive understanding of its response to environmental changes. [ABSTRACT FROM AUTHOR]

The present study is aimed to document the movement and habitat use of golden mahseers (Tor putitora) inhabiting the Himalayan waters in India. A total of nine adult golden mahseers (two males and seven females) fitted with a VHF radio tag were monitored between pre-monsoon and post-monsoon periods. The individuals were found dispersed with the maximum recorded distance of 4231.23 and 6119.11 m in the Kosi and Kolhu rivers respectively. Home ranges for males (0.0245 sq. km) and larger individuals (0.0697 sq. km) exhibited released side fidelity, whereas females (0.361 sq. km) and smaller individuals (0.459 sq. km) moved long distances. The results of this study identify the movements and spatial ecology knowledge of golden mahseer to conserve fish habitats. [ABSTRACT FROM AUTHOR]

Evaluation of the ecological health of rivers requires a focused examination of how biological indicators respond to chemical stressors to offer key insights for effective conservation strategies. We examined the influence of stressors on aquatic ecosystems by analyzing various ecological entities and biotic integrity metrics of fish communities. A nonmetric multidimensional scaling (NMDS) approach was applied to determine scores based on 19 fish ecological entities (FEs) and a fish-based multi-metric index of biotic integrity (mIBI-F). The composition of fish communities in reference clusters differed from the disturbed clusters due to instream chemical stressors. These chemical stressors, including high levels of nutrients, organic matter, and ionic/suspended solids, were linked to variation in the key indicator FEs, whose guild identities were closely associated with instream chemical degradation. The scores of FEs (abundance weighted) and mIBI-F metrics in the first NMDS axis (NMDS1) were significantly linked with chemical health indicators (p < 0.001), such as total phosphorus (R2 = 0.67 and 0.47), electrical conductivity (R2 = 0.59 and 0.49), and chlorophyll-a (R2 = 0.48 and 0.25). These NMDS1 scores showed better accuracy than the conventional mIBI-F score in capturing river ecological health linked with chemical health status as determined by a multi-metric index of water pollution. Our study suggests that based on the ordination approach, the biological integrity of these systems reflected the chemical health. [ABSTRACT FROM AUTHOR]

Natural environmental change, anthropogenic development, and inter-annual variability can affect the ecology of estuarine fish and invertebrates. Yaquina Bay, Oregon, a well-studied estuary, has undergone intense development, as well as deep-draft dredging during the latter half of the 20th century, resulting in the alteration of ~45% of the lower estuary's natural shoreline. In 1967, the United States Environmental Protection Agency (USEPA) conducted a 21-month survey of Yaquina Bay to characterize the demersal fishes and epibenthic crustaceans that occupy the bay. From 2003 to 2005, we conducted a 25-month survey to replicate that work and provide a comparative snapshot of the demersal fish and epibenthic crustacean community in the bay. A comparison of the trawl survey datasets reveals a 91% decline in total catch per unit effort (CPUE) between surveys, as well as a decline in multiple measures of biodiversity. Furthermore, the fishes and crustaceans of Yaquina Bay have experienced a shift in species dominance from demersal fishes in the late 1960s to epibenthic crustaceans in the 2000s, marked most notably by a nine-fold increase in the Dungeness crab CPUE. While this work does not establish a causal relationship between changes in the demersal communities of this West Coast estuary and human or natural events, it does document substantial changes in both the diversity and total abundance of animals in that community over a three-plus decade period of development and environmental variability. Hence, this forms a second baseline for continued long-term monitoring. [ABSTRACT FROM AUTHOR]

Ecological aspects are essential for testing hypotheses about the characteristics, evolutionary processes and behaviour patterns of different taxa. However, for many neotropical lizards, like Gymnodactylus darwinii, such information is scant in the literature. This lizard is endemic to the Atlantic rainforest, occurring from Rio Grande do Norte to São Paulo. Herein, the aspects of trophic ecology, microenvironmental specificity and sexual dimorphism were analysed from 65 collected individuals and 15 sighted individuals in two conservation units: Camucim and Tapacurá, located in São Lourenço da Mata, north‐eastern region of Brazil. The data found classify G. darwinii as a saxicolous lizard, with a preference for rocky outcrops, without sexual dimorphism. According to its trophic ecology, the species is considered a generalist and sit–wait forager. Arthropods, especially Orthoptera and Araneae, dominate the lizard's diet. Neither of these aspects differed between seasons. The present study also shows the importance of the domain conservation, with the aim to provide resources for many vertebrates, especially endemic species. [ABSTRACT FROM AUTHOR]

The trophic ecology of fishes in the genus Rhamdia remains poorly reported. Here, we aim to describe the diet composition and infer the trophic levels, niche breadth, and niche overlap between Rhamdia guatemalensis and Rhamdia laticauda in northeast Oaxaca, Mexico. Fishes were sampled using an electrofishing device between 2016 and 2017. We calculated the Quotient index and the diet composition was analyzed using the percentage of the Index of Relative Importance (%IRI) to analyze possible ontogenetic and sexual differences on feeding ecology. We then calculated the trophic niche breadth using the Levins´ standardized index (BA). Trophic levels (TLk) of each species were calculated using the trophic index and trophic niche overlap using Pianka´s index (Ojk). The results indicate that both species are carnivorous and tend to prey on aquatic insects, with R. guatemalensis feeding on nine different orders of animals and R. laticauda displaying a broader diet spectrum, encompassing 19 orders. Our data showed ontogeny and sex differences in the trophic ecology of R. guatemalensis. They were secondary consumers (TLk > 3) and showed a specialized diet (BA < 0.4). We found evidence of trophic niche partitioning between adults (Ojk = 0.40) and females (Ojk = 0.42). Our results highlight the fundamental role of this species in the area as a carnivorous/insectivorous, predatory fishes, secondary consumers, and biological control for Diptera, Ephemeroptera, and Megaloptera. Both species minimize the trophic overlap through food resource partitioning mediated by fish body size. Additionally, adults and females consume different prey, which allows the coexistence of closely related species. Our findings regarding trophic ecology could be crucial for devising conservation and management plans for these particular Rhamdia species. [ABSTRACT FROM AUTHOR]

The study of diet is one of the mechanisms by which competition for resources between species that cohabit in the same ecosystem can be inferred. Therefore, the relationships of the indices that measure specialization in the diet of fish species are necessary to characterize the nutritional quality of these populations and the ecosystem's environmental health. Three species of catfish were selected: one invasive (Clarias gariepinus) and two natives (Trachelyopterus striatulus and Rhamdia quelen), with similar distribution along the Guapi‐Macacu River, in the Guapimirim Protection Area (Rio de Janeiro). Fifty‐nine catfish of the three species were collected in total, along 32 collection points in the Guapi‐Macacu River in two periods (dry and rainy) in 2018. Non‐parametric statistics showed the partition of resources between species and the influence of abiotic factors (temperature, pH, transparency, and dissolved oxygen) contributing to the selection of available resources in the environment. Diet‐related indices—repletion index (RI), condition factor (K), niche width, and trophic position (TP) of the specimens collected—contributed to measuring the nutritional status of each of these catfish species, showing that R. quelen has a relationship between RI and K, tending to absorb and metabolize nutrients faster than other species. In addition, the invasive species occupies a wide range of TPs compared to native species, confirming its feeding plasticity. On the contrary, T. striatulus needs large amounts of terrestrial insects to maintain its poor condition factor. Also, the RI showed direct influences of abiotic variables, with the temperature being the most prominent. Our results suggest that the invasive species can benefit from this environment that shows signs of environmental degradation. [ABSTRACT FROM AUTHOR]

Knowledge of fish movement ecology contributes to the improvement of fishery resource management actions. We investigated the horizontal movement of the black sea bream Acanthopagrus schlegelii around the natural coast of Nishinoumishima Island in Hiroshima Bay, using active acoustic tracking. Six adult fish equipped with depth transmitters were tracked for a total of 54 days in the bay. Five tagged fish were fully tracked for 9–10 consecutive days after release. Tagged fish were found in the intertidal zone and adjacent subtidal zones, which were shallower than 12 m, and within 170 m off the coastline. The mean daily movement distance and 95% kernel utilized density of tagged fish were 191 ± 272 m and 60,207 ± 99,437 m2, respectively. The swimming depth of the tagged fish was 1–4 m above the seafloor. We opine that the littoral area (< 12 m in depth), which includes the intertidal zone and adjacent subtidal zone, is an important habitat for black sea bream. [ABSTRACT FROM AUTHOR]

As urbanization expands, it is becoming increasingly important to understand how anthropogenic activity is affecting ecological and evolutionary processes. Few studies have examined how human social patterns within cities can modify eco‐evolutionary dynamics. We tested how socioeconomic variation corresponds with changes in trophic interactions and natural selection on prey phenotypes using the classic interaction between goldenrod gall flies (Eurosta solidaginis) and their natural enemies: birds, beetles, and parasitoid wasps. We sampled galls from 84 sites across neighbourhoods with varying socioeconomic levels, and quantified the frequency of predation/parasitism on flies and natural selection by each enemy. We found that bird predation was higher in the highest income neighbourhoods, increasing the strength of selection for smaller galls. Wasp and beetle attack, but not their strength of selection, increased in lower income neighbourhoods. We show that socioeconomic variation in cities can have strong unintended consequences for the ecology and evolution of trophic interactions. [ABSTRACT FROM AUTHOR]

To study the morphological differences between and the evolutionary mechanisms driving the differentiation of geographically distinct populations of Gymnodiptychus dybowskii, 158 fish were collected from the Turks River and the Manas River in Xinjiang from 2020 to 2021 with the approval of the Academic Ethics Committee. The morphological characteristics of the fish were assessed using classical fish ecology methods such as traditional morphometric measurements and the framework approach. The results showed that the morphological characteristics of the populations in the Turks River and Manas River were significantly different; a one-way ANOVA revealed 22 highly significant differences (p < 0.01) and 1 significant difference (p < 0.05) among the 33 morphological traits of the observed populations, and a principal component analysis revealed that there was no overlap between the two populations of G. dybowskii. The main characteristics associated with principle component 1 were the terminus of the dorsal fin to the ventral origin of the caudal fin (D—F), the dorsal origin of the caudal fin to the origin of the anal fin (E—H), and the insertion of the pectoral fin to the terminus of the pectoral fin (J—K); the main factors associated with principal component 2 were the body height (BD), the terminus of the dorsal fin to the insertion of the pelvic fin (D—I), the caudal peduncle height (CPH), and the tip of the snout to the last end of the frontal maxilla (A—B); and the main traits associated with principle component 3 were the terminus of the anal fin to the origin of the anal fin (G—H), the body width (BW), the insertion of the pelvic fin to the terminus of the pelvic (I—L), the insertion of the pectoral fin to the terminus of the pectoral fin (J—K), and the insertion of the pelvic fin to the insertion of the pectoral fin (I—J). An OPLS-DA revealed that the two populations could be wholly separated and that the intergroup growth traits of the Manas River population were different and significantly greater than those of the Turks River population. The discriminant functions of the Turks River and Manas River populations of G. dybowskii were as follows: YT = −432.033 + 1787.748X1 + 826.517X2 + 249.002X3 + 1183.050X4 + 554.934X5 + 999.296X6 + 627.428X7; YM = −569.819 + 2041.044X1 + 344.942X2 + 333.737X3 + 940.512X4 + 348.222X5 + 1167.770X6 + 1015.904X7. According to a coefficient of variation analysis, a total of nine traits, namely, EI/BL, C-D/BL, E-F/BL, F-H/BL, H-I/BL, C-J/BL, D-I/BL, D-H/BL, and D-F/BL, had a CD > 1.28, indicating that the differences in these nine traits had reached the subspecies level. The results showed that G. dybowskii significantly differed between the two geographically distinct populations in the Turks River and the Manas River and have differentiated to the subspecies level. This study provides a basis for a better investigation of the population structure of highland endemic fishes and the mechanisms by which they diverged and lays a foundation for developing and utilizing germplasm resources from endemic fishes in Xinjiang. [ABSTRACT FROM AUTHOR]

The rupture of the Fundão dam is considered the largest mining failure in history, which had a particularly detrimental impact on fish populations, as the mud from the ore tailings significantly altered the water quality and habitat of Doce River basin. This study aimed to assess the trophic structure of fish communities in areas impacted and not impacted by the dam rupture in the Doce River basin. To evaluate the food web structure, community-wide trophic niche, and trophic positions of fish, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were utilized across ten sites (seven impacted and three control). In general, fish appeared to assimilate resources such as invertebrates, algae, and periphyton, although the importance of each resource varied among sites. The site closest to the dam rupture exhibited a more simplified trophic structure compared to the control sites and those nearer the river mouth. In this site, most fish species occupied a similar trophic position. Trophic niches also exhibited the greatest dissimilarity between the site closest to the dam failure and those farther away from it, with an expansion of trophic niche breadth observed with an increase in the distance from the dam rupture. Our study provided valuable insights into the trophic structure of fish communities within the Doce River basin, shedding light on the trophic ecology of the 59 fish species investigated. We also emphasize the importance of our study for future assessments of ore tailings dam failure disasters and evaluating the effectiveness of mitigation measures for Doce River basin recovery. [ABSTRACT FROM AUTHOR]

Evaluating and integrating local ecological knowledge held by fishers into decision-making processes has the potential to significantly enhance fisheries management. The present study aimed to collect information on fishery practices and to assess the ecological knowledge of local professional fishers through interviews, evaluating its importance in managerial design. As a case study, Polyphytos Reservoir in Greece, which supports substantial fisheries, was selected. During the summer of 2023, thirty-seven interviews were conducted to document fishing efforts, methods, catches, biological information, and fishers’ perspectives on lake management, and economic/demographic details. In addition to gathering data on fishing activities, the study seeks to understand fishers’ perspectives on managerial deficiencies and necessities, thereby revealing their valuable ecological knowledge. The integration of this knowledge into decision-making processes can empower stakeholders and enhance local participation in fishery management. Ultimately, this approach has the potential to address long-standing conflicts, foster inclusive processes, and ensure better collective outcomes.

Despite supporting a disproportionately large fraction of the global biodiversity, freshwater ecosystems are ranked as the most highly threatened habitats ahead of both terrestrial and marine ecosystems. Furthermore, many regions are still characterized by limited knowledge on taxonomy and ecology of freshwater fishes. The need for ecological information in understudied regions is important particularly where there are recent discoveries of new species and unique lineages and for threatened and endangered taxa that require conservation management.This study evaluated the trophic ecology of two freshwater fish species Sandelia bainsii and Amatolacypris trevelyani that are both classified as endangered in the International Union for Conservation of Nature (IUCN) Red List. These two species, which are narrow‐range endemics in the Eastern Cape, South Africa, comprise allopatric lineages whose ecology is poorly known. This study used stable isotope analysis to evaluate the food web patterns, explore the trophic niche dynamics and estimate the prey source contributions for the two species in different headwater habitats.The fishes isotopic niche sizes were spatially variable, suggesting the likely importance of stochastic variation in resource availability and probable interspecific interactions. The three lineages within S. bainsii exhibited low isotopic niche overlap onto those of sympatric fishes in most habitats. Isotopic mixing model revealed that these lineages' diets were mostly dominated by gatherers/collectors. In comparison, the two lineages within A. trevelyani exhibited high niche overlap with other species and generally had variable diets.Despite the low and high niche overlap patterns of S. bainsii and A. trevelyani, respectively, the isotopic niche overlap patterns of co‐occurring species onto those of the former suggest the likely lack of competitive hierarchies. The trophic niche patterns of these two endangered species helped to shed some light on the potential invasion risks by non‐piscivorous fishes with opportunistic feeding habits, which could exert competitive interspecific interactions. [ABSTRACT FROM AUTHOR]

Climate-driven species redistributions are facilitated by niche modifications that increase a species's chances of establishment in novel communities. It is well understood how range-extending species adjust individual niche traits when entering novel environments, yet whether modification of ecological niche traits collectively alters the pace of range extensions or contractions remains unknown. We quantified habitat niche, abundance, physiological performance and cellular defence/damage of range-extending coral reef fishes and coexisting local temperate fishes along a 2000 km latitudinal gradient. We also assessed their dietary and behavioural niches, and establishment potential, to understand whether ecological generalism facilitates successful range extension of coral reef fishes. The coral reef fish that increased all ecological niches, showed stronger establishment, increased physiological performance and cellular damage, but decreased cellular defence at their cold-range edge, whereas tropical species that showed unmodified ecological niches showed lower establishment. One temperate species showed decreased abundance, habitat niche width and body condition, but increased cellular defence, cellular damage and energy reserves at their warm-trailing range, while other temperate species showed contrasting responses. Therefore, ecological generalists might be more successful than ecological specialists during the initial stages of climate change, with increasing future warming strengthening this pattern by physiologically benefitting tropical generalists but disadvantaging temperate specialists. [ABSTRACT FROM AUTHOR]

Although otoliths are widely used as archives to infer life‐history traits and habitat use in fishes, their biomineralization process remains poorly understood. This lack of knowledge is problematic as it can lead to misinterpretation of the different types of signals (e.g., optical or chemical) that provide basic data for research in fish ecology, fisheries management, and species conservation. Otolith calcification relies on a complex system involving a pericrystalline fluid, the endolymph, whose organic and inorganic compositions are spatially heterogeneous for some constituents. This property stems from the particular structure of the calcifying saccular epithelium. In this study, we explored the spatial heterogeneity of elemental incorporation in otoliths for two species of high economic interest, European hake Merluccius merluccius (L. 1758) and European sea bass Dicentrarchus labrax (L. 1758). Two‐dimensional mappings of chemical elements were obtained using UV high‐repetition‐rate femtosecond laser ablation (fs‐LA) system coupled to a high‐resolution inductively coupled plasma sector field mass spectrometer analyses on transverse sections of sagittae. Results highlighted a clear asymmetry between proximal (sulcus) and distal (antisulcus) concentrations for elements such as magnesium (Mg), phosphorus (P), manganese (Mn), and potassium (K) with concentration gradient directions that varied depending on the element. Strontium (Sr) and barium (Ba) did not show a proximo‐distal gradient. These results are discussed in light of current knowledge on the endolymph composition and the mechanisms that lead to its compartmentalization, highlighting the need for further research on otolith biomineralization. Operational implications for studies based on otolith chemical composition are also discussed with emphasis on advice for sampling strategies to avoid analytical biases and the need for in‐depth analyses of analytical settings before comparing otolith signatures between species or geographical areas. [ABSTRACT FROM AUTHOR]

Elasmobranch population declines due to human impacts have been documented at a global scale, having impacts on the functioning and structure of marine ecosystems. This situation leads to an international focus on the conservation of their populations and a key step in the management and conservation of elasmobranch populations is to understand their trophic ecology. Here, by using stable isotopes analysis, we investigated the trophic relationships, trophic niche breadth, and trophic redundancy among 21 batoids and 12 sharks inhabiting the Persian Gulf and Gulf of Oman, two productive areas of the Arabian Sea considered global elasmobranch hotspots. Isotopic results revealed differences in the trophic niche and trophic position among the elasmobranch sampled at species and at family level. For example, the batoids of the family Torpedinidae and the sharks of the family Triakidae occupied higher trophic positions and the family Glaucostegidae showed a lower trophic niche width, whereas the batoids of the family Myliobatidae or Gymnuridae, in overall, showed lower higher trophic niche width, reflecting the trophic habits described for most of the sampled species. We also provided some insights into the ecology of poorly known species, especially relevant for those that are endangered at a global or regional scale. In conclusion, we provide new information about the trophic ecology among batoids and sharks inhabiting the Persian Gulf and Gulf of Oman. This information is highly useful to study the consequences of future changes on their feeding preferences due to natural or human-related factors. [ABSTRACT FROM AUTHOR]