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Over one third of sharks, rays and chimaeras (chondrichthyans) are threatened with extinction globally. In the Mediterranean Sea, more than half of chondrichthyan species face this risk, although a variety of international, regional, and national rules and regulations apply directly and indirectly targeting management and conservation for these species. In this work, we provide an overview of relevant legislation and policies in the region, which regulate, inter alia, commercial fisheries, while highlighting through cases studies how implementation in practice at national level looks like. Horizontal gaps and inconsistencies that hinder chondrichthyan management in the region are also illustrated. Furthermore, we present recommendations for improvement and additional tools that can be used, even if not originally or explicitly targeting chondrichthyans, for improving the management of these taxa in the Mediterranean. [ABSTRACT FROM AUTHOR]

Wetlands are characterized by flow and environmental dispersion, which are necessary in the water management system. Contaminant transport in wetlands has a significant effect in the field of biology and environmental fluid dynamics for the conservation of fish and wildlife species, erosion prevention, and mainly recreation. When an instantaneous contaminant is released into a wetland, both boundary absorptions and wind have a significant impact on the contaminant dispersion process. The present study highlights the wind effects and boundary absorption on environmental dispersion and stream-wise mean concentration in a width-dominated flow for a shallow wetland. A multi-scale time period is considered to determine the dispersion model, which illustrates the contaminant transport process greatly affected by different ecological parameters like dispersion time, boundary absorption, tortuosity and vegetation drag. It is noted that the stream-wise concentration distribution is almost identical to the transversal concentration distribution due to tortuosity and bottom vegetation effect. It is noticed that the stream-wise concentration of contaminant gradually decreases due to the increase of vegetation parameters and tortuosity. The distribution of flow velocity is derived analytically from the momentum equation for different wind strengths. The effect of boundary absorption strength on stream-wise and mean concentration are discussed. Also, it is evident that the distribution of concentration is complex for boundary absorption under the effects of wind. [ABSTRACT FROM AUTHOR]

Objective: Increasing reliance on numerical simulation models to help inform management and restoration choices benefits from careful consideration of critical early steps in model development. Along the northern coast of the Gulf of Mexico, the eastern oyster Crassostrea virginica fulfills important ecological and economic roles. Using the eastern oyster as an example, we draw on several recent frameworks outlining best practices for model development and application for restoration, conservation, and management. Methods: We identify priority model questions, outline a conceptual ecological model (CEM) to guide numerical model development, and use this framework to identify uncertainties and research needs. Result: The CEM uses a nested design, identifying explicit vital rates, processes, attributes, and outcomes for the species (oysters), population, and metapopulation (i.e., network of populations) levels in response to drivers of species, population, and metapopulation changes and changing environmental factors. Most management actions related to oyster restoration and harvest affect population attributes directly, but many coastal management actions and changes (i.e., climate change and coastal and water resource engineering) impact environmental factors that alter vital rates and attributes of oysters, populations, and metapopulations. Conclusion: Investment in studies targeting individual oyster‐ and population‐level multi‐stressor responses (filtration, respiration, growth, and reproduction) and improving hydrodynamic and environmental models targeting drivers that influence metapopulation vital rates and attributes (i.e., connectivity and substrate persistence) would contribute to reducing uncertainties. Development of numerical models covering the entire oyster life cycle and connectivity of populations using hydrodynamic models of current and predicted conditions to provide key abiotic and biotic factors influencing larval movement, recruitment, and on‐reef oyster vital rates would assist in balancing the goals of conservation, restoration, and fisheries management of this foundational estuarine species. Impact statementManaging fisheries species of conservation, production, and habitat value relies increasingly on the development of numerical models. We develop a tiered conceptual ecosystem model to guide model development for the eastern oyster and to highlight key uncertainties in vital rates and outcomes. This tiered approach provides a flexible framework to guide numerical model development, and highlight key uncertainties influencing modeled outputs. [ABSTRACT FROM AUTHOR]

Large-bodied animals, such as the Mekong giant catfish (Pangasianodon gigas), may modify prey communities and affect their potential competitors for food resources by consuming large quantities of prey. The Mekong giant catfish is a key representative of freshwater megafauna and is stocked in reservoirs in Thailand for species conservation and fishery stock enhancement. However, their biological interactions with other sympatric animals remain unclear. Here, we aimed to investigate the trophic niche of the Mekong giant catfish in a Thai reservoir by comparing stable carbon and nitrogen isotope ratios (δ13C and δ15N, respectively) and fatty acid (FA) composition with those of five other sympatric fish species. The δ13C value of the Mekong giant catfish was –24.4 ± 1.0‰ (mean ± SD), the second highest among the sympatric fish species, suggesting relatively weak reliance on phytoplankton-based food chains. The δ15N value of the Mekong giant catfish was 10.7 ± 0.4‰, intermediate between those of herbivorous and carnivorous fishes, indicating that it is not a primary consumer. The FA composition of the Mekong giant catfish significantly differed from those of the other fish species and was characterized by a large proportion of long-chain FA, including 22:6n-3, 20:5n-3, and 20:1n-9. The δ13C, δ15N, and FA signatures suggest that the Mekong giant catfish occupy distinct trophic niches in food webs. Our results highlight that it is necessary to monitor the ecological impacts of released Mekong giant catfish on lower-level consumers through their foraging in receiving reservoirs. [ABSTRACT FROM AUTHOR]

Fishes exhibit a diverse range of traits encompassing life‐history strategies, feeding behaviours and spawning behaviours. These traits mediate fish population responses to changing environmental conditions such as those caused by anthropogenic stressors. The Conasauga River, located in northwestern Georgia and southeastern Tennessee, USA, hosts a diverse assemblage of over 75 species of freshwater fish, some of which are locally or regionally endemic, and many of which are imperilled. Annual monitoring data have shown population declines in multiple fish species of conservation concern in the Conasauga River since at least the 1990s, raising the possibility that other taxa could be declining as well. We quantified temporal changes in fish communities at six shoal sites sampled annually in most years from 1996 to 2022, and asked whether species traits hypothesized to underlie population vulnerability to environmental alteration were correlated with species‐specific trends for 32 taxa. We estimated that total counts of fish in annual samples declined by ~2% per year, although declines were uneven among species and generally greater for less abundant taxa. Tests for species traits corresponding to temporal population trends provided evidence that crevice‐spawning minnows and smaller‐bodied taxa had steeper declines compared with broadcast spawners and larger, longer‐lived, more fecund taxa. Lower abundance, reliance on a particular habitat feature, and life‐history traits that may limit population resilience to disturbance may all prove useful for identifying riverine fishes at particular risk of future population decline. [ABSTRACT FROM AUTHOR]

Aim: Rare species make substantial contributions to coastal ecosystem functions. Functional rarity (FR) and phylogenetic rarity (PR) are important features for biodiversity conservation. This work aimed to discuss the necessity and reasonableness of conserving fish FR and PR in coastal seas. Location: China. Methods: By compiling historical fish investigation data, joint species distribution modelling (JSDM) was applied to model fish communities in coastal China Seas. Biogeographic patterns of FR and PR were explored, and the effectiveness of current MPA networks in terms of match/mismatch with the hotspots of rarity was assessed. Results: A total of 44 functionally rare species and 22 phylogenetically rare species were identified. Six of these species were both functionally and phylogenetically rare, and only one was listed as endangered on the Red List of the International Union for Conservation of Nature (IUCN). Functional rarity hotspots covered 10.27% of the coastal areas, which geographically converged in the southern and eastern coast of Taiwan, the Yangtze River Estuary and the Yellow River Estuary. Phylogenetic rarity hotspots only covered 3.06% of the coastal areas, which were sporadically distributed in the coastal East China Sea, the Bohai Sea and the northern Yellow Sea. Current marine‐protected areas (MPAs) only represented 16.16% of the FR hotspots and 20.48% of the PR hotspots, indicating substantial mismatched areas between the MPAs and the hotspots of FR and PR. Main Conclusions: Only considering threatened species in conservation practices will omit functionally and phylogenetically rare species because FR and PR are not necessarily correlated with species threat status on the IUCN Red List. Functional rarity hotspots do not necessarily overlap with PR hotspots, and current MPAs mismatch the majority of these areas. We therefore advocate that conservation prioritization and expansion of MPA networks should account for FR and PR both at the species and site levels. [ABSTRACT FROM AUTHOR]

Conservation practices from the perspective of functional diversity (FD) and conservation prioritization need to account for the impacts of exotic species in freshwater ecosystems. This work first simulated the influence of exotic species on the values of FD in a schemed mechanistic model, and then a practical case study of conservation prioritization was performed in the Min River, the largest river in southeastern China, to discuss whether including exotic species alters prioritization. The mechanistic model revealed that exotic species significantly altered the expected FD if the number of exotic species occupied 2% of the community. Joint species distribution modelling indicated that the highest FD occurred in the west, northwest and north upstreams of the Min River. Values of FD in 64.69% of the basin decreased after the exotic species were removed from calculation. Conservation prioritization with the Zonation software proved that if first the habitats of exotic species were removed during prioritization, 62.75% of the highest prioritized areas were shifted, average species representation of the endemic species was improved and mean conservation efficiency was increased by 7.53%. Existence of exotic species will significantly alter the metrics of biodiversity and the solution for conservation prioritization, and negatively weighting exotic species in the scope of conservation prioritization is suggested to better protect endemic species. This work advocates a thorough estimate of the impacts of exotic species on FD and conservation prioritization, providing complementary evidence for conservation biology and valuable implications for local freshwater fish conservation. [ABSTRACT FROM AUTHOR]

Objective: Natural dispersal or unauthorized introductions of nonnative predatory sport fish can undermine native species conservation and other fisheries management objectives. The use of reproductively sterile triploid fish may provide a lower risk stocking option (i.e., genetic and reproductive containment) for diversifying angling opportunities while possibly reducing angler motivation to illegally transplant fish. Management interest in triploid Walleye Sander vitreus is growing, and these fish are currently stocked by several fisheries agencies. However, little is known about the poststocking growth, body condition, and survival of triploid Walleye—information that is important for calibrating expectations and guiding policy regarding their use. Methods: We compared the age‐specific size, body condition, and survival of subadult (i.e., ages 0–3) triploid Walleye to those of normal diploid conspecifics in two eastern Colorado reservoirs. Paired stockings of triploid and diploid Walleye occurred over 3 years. Both fry and fingerlings were stocked each year. Result: Triploids were generally smaller in length (6.6% smaller on average) and weight (20.6% smaller) compared to diploids across all age‐classes. Despite being smaller, triploids had similar body condition relative to diploids. On average, the survival of triploids from spring stocking to their first fall was 6.3× lower than that of diploids, but no differences in survival were observed beyond this early life stage. This pattern was consistent across cohorts and reservoirs. Conclusion: The present work provides a foundation for future studies that are designed to clarify patterns of survival from spring to the first fall by accounting for size at stocking and natural‐origin fish and studies that are planned to assess the poststocking performance of triploid Walleye independent of diploids. Impact statementBalancing recreational fisheries management with native species conservation efforts can be challenging, especially in cases where anglers highly value nonnative predators. The practice of stocking sterile fish is an emerging management approach aimed at addressing concerns about introducing or maintaining existing populations of predatory fish outside of their native range. While artificially induced triploidy is among the most common methods for producing sterile fish, little is known about how triploid fish grow and survive in the wild, information that is crucial for decision making regarding their use. In this study, we provide some of the first information regarding the size, body condition, and survival of triploid Walleye relative to normal, diploid Walleye in the wild. Our findings will aid managers in making decisions regarding the use of triploid Walleyes in their programs. [ABSTRACT FROM AUTHOR]

Aquatic wildlife health assessment is critically important for aquatic wildlife conservation. However, the health assessment of aquatic wildlife (especially aquatic wild animals) is difficult and often accompanied by invasive survey activities and delayed observability. As there is growing evidence that aquatic environmental microbiota could impact the health status of aquatic animals by influencing their symbiotic microbiota, we propose a non-invasive method to monitor the health status of wild aquatic animals using the environmental microbiota health index (microHI). However, it is unknown whether this method is effective for different ecotype groups of aquatic wild animals. To answer this question, we took a case study in the middle Yangtze River and studied the water environmental microbiota and fish gut microbiota at the fish community level, population level, and ecotype level. The results showed that the gut microHI of the healthy group was higher than that of the unhealthy group at the community and population levels, and the overall gut microHI was positively correlated with the water environmental microHI, whereas the baseline gut microHI was species-specific. Integrating these variations in four ecotype groups (filterfeeding, scraper-feeding, omnivorous, and carnivorous), only the gut microHI of the carnivorous group positively correlated with water environmental microHI. Alcaligenaceae, Enterobacteriaceae, and Achromobacter were the most abundant groups with health-negative-impacting phenotypes, had high positive correlations between gut sample group and environment sample group, and had significantly higher abundance in unhealthy groups than in healthy groups of carnivorous, filter-feeding, and scraper-feeding ecotypes. Therefore, using water environmental microHI to indicate the health status of wild fish is effective at the community level, is effective just for carnivorous fish at the ecotype level. In the middle Yangtze River, Alcaligenaceae, Enterobacteriaceae (family level), and Achromobacter (genus level) were the key water environmental microbial groups that potentially impacted wild fish health status. Of course, more data and research that test the current hypothesis and conclusion are encouraged. [ABSTRACT FROM AUTHOR]

It's essential to identify the priority conservation species in the habitat restoration and biodiversity conservation. Generally, people select the valuable fishes or the commercial fishes as target species in basins, according to experts' experience rather than the scientific evaluation. With the influence of urban development, construction of water conservancy facilities and human activities, the river habitat of the Shaying River (Xuchang section) is poor. Fish conservation studies play an important part in the habitat restoration of this river section. Thus, we studied the evaluation method for the priority protection of fishes based on multiple ecological dimensions. The method including six multidimensional indicators, namely, habitat suitability, ecological stability, species endangerment criteria, intensity of human interference, genetic value, and species value. Then, we determined the indicator weights by the analytic hierarchy process (AHP), and assessed the protection priority of fishes based on various assessment criteria and comprehensive qualitative or quantitative analyses. The result shows that Ctenopharyngodon idellus, Opsariichthys bidens, and Culter alburnus Basilewsky have priority for protection, coinciding with the status in the basin. Overall, this study complements the existing indicator species selection methods, and is more scientific and comprehensive, providing an effective method for priority protection species and river habitat restoration projects. [ABSTRACT FROM AUTHOR]

Medicinal leeches are known to primarily inhabit shallow parts of wetlands, which have unique physical, chemical, and biological properties that differ from the main bodies of water in these areas. However, limited research has been conducted on fish diversity and abundance in these habitats. This study aimed to investigate the fish diversity and abundance in the wetlands surrounding Lake Eğirdir (Turkey), where medicinal leeches are known to be present, and discuss the importance of conserving these habitats. Common diversity indices were used to estimate species richness, abundance, and biomass. A total of 416 fish from six species (Aphanius anatoliae, Carassius gibelio, Gambusia holbrooki, Pseudophoxinus egridiri, Pseudorasbora parva, and Seminemacheilus ispartensis) were sampled. The results showed that the species richness was lower in the studied wetlands (six species) compared to the lake itself (13 species), with the dominant species in terms of abundance and biomass being G. holbrooki (44.95%) and C. gibelio (33.46%). The presence of invasive and endemic species plays an important role in shaping the diversity and abundance of the fish community. The study found that there is compatibility between fish diversity and medicinal leeches in wetlands, and that fish species and their sizes provide feeding opportunities in favor of medicinal leeches. The wetlands also provide a protected area for the conservation of two IUCN red-listed fish species (P. egridiri and A. anatoliae). Thus, the study highlights the importance of conserving these habitats for maintaining the ecological unity, harmony, and sustainability of both medicinal leeches and fish populations. [ABSTRACT FROM AUTHOR]

Swordtip squid (Uroteuthis edulis), which is sometimes eaten alive (lively squid) in northwest Kyushu, Japan, is an economically important fish species in the region. However, the total catch of this species in Japan has declined by more than 80% in the last three decades. To understand and predict the spatio‐temporal distribution of fish species, we developed a one‐dimensional ecosystem (NPZD) model and a habitat suitability index (HSI) model for southwest Iki Island, northwest Kyushu, Japan. Subsequently, we conducted three numerical experiments with the HSI model, with and without the NPZD model data (with the NPZD model data: phytoplankton or zooplankton concentrations, without the NPZD model data: only the physical data of the ocean). In the HSI model with zooplankton concentrations, we found a stronger positive relationship between the HSI model values and the daily fisheries catch data of U. edulis than that using only the physical variables of the ocean as the environmental parameters. Our study thus indicates that the performance of the fishing ground prediction model will improve by utilizing the lower trophic ecosystem model such as zooplankton concentrations. Furthermore, our results would provide important implications for the efficiency of fishing operations and the conservation and management of this species. [ABSTRACT FROM AUTHOR]

Global warming affects the metabolism of ectothermic aquatic breathers forcing them to migrate and undergo high‐latitudinal distribution shifts to circumvent the temperature‐induced mismatch between increased metabolic demand and reduced water oxygen availability. Here the authors examined the effects of temperature on oxygen consumption rates in an Arctic stenotherm, the Greenland halibut Reinhardtius hippoglossoides, and calculated the optimal temperature for maximum aerobic scope, AS(Topt,AS), which was found to be 2.44°C. They also investigated cardiac performance as limiting the oxygen transport chain at high temperatures by measuring maximum heart rate (fHmax) over acute temperature increases and found various metrics related to fHmax to be at least 3.2°C higher than Topt,AS. The authors' measured Topt,AS closely reflected in situ temperature occurrences of Greenland halibut from long‐term tagging studies, showing that AS of the species is adapted to its habitat temperature, and is thus a good proxy for the species' sensitivity to environmental warming. The authors did not find a close connection between fHmax and Topt,AS, suggesting that cardiac performance is not limiting for the oxygen transport chain at high temperatures in this particular Arctic stenotherm. The authors' estimate of the thermal envelope for AS of Greenland halibut was from −1.89 to 8.07°C, which is exceptionally narrow compared to most other species of fish. As ocean temperatures increase most rapidly in the Arctic in response to climate change, and species in these areas have limited possibility for further poleward‐range shifts, these results suggest potential severe effects of global warming on Arctic stenotherms, such as the Greenland halibut. The considerable economic importance of the species raises concerns for future fisheries and species conservation of Arctic stenotherms in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

Freshwater fish populations are in steep decline, prompting conservation measures and a need for their evaluation. Fish are increasingly monitored with passive integrated transponders (PIT), although the suitability of this tagging technique has not yet been validated for most European target species of conservation. Consequently, this study tested the effect of commonly used 12 mm full-duplex (FDX) PIT tags implanted into the abdominal cavity of common nase (Chondrostoma nasus L.) and European barbel (Barbus barbus L.). A controlled laboratory setup was used to compare survival, growth (both length and weight) and tag retention for two different size classes of sub-adults over 61 days. Survival in the treatment groups was high (96.7–100%) and not statistically different from the control groups (97.5–100%). Highest mortality occurred in small tagged barbel (n = 4; 96.7% survival), while no mortality occurred in large tagged nase. Mean growth rates for tagged fish (2.28 mm, 3.26 g) were similar to those of control fish (2.77 mm, 3.59 g). Overall tag retention rate was 99.0% and tag loss only occurred in nase. The results of this study demonstrate the suitability of PIT injection in the body cavity of nase and barbel > 100 mm TL, which is of high methodological importance given the increasing role these species play in PIT tag-based assessments of freshwater fish conservation in European rivers. [ABSTRACT FROM AUTHOR]

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Copyright of Acta Zoologica Lilloana is the property of Fundacion Miguel Lillo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lumpfish are a commercially significant marine fish that are harvested in roe fisheries and used as cleaner fish in salmon farming, however, little is known of the environmental factors shaping the ecological niche of the species at global scale. As captive reared lumpfish are sensitive to warm water, the geographic distribution of wild populations may change as sea temperatures rise under expected climate change. After investigating the ecological niche of the lumpfish using Species Distribution Models, we found that nitrate concentration, ice cover, diffuse attenuation, and temperature predicted the probability of lumpfish occurrence. Through modelling distribution under expected climate change forecasts within a realistic scenario, we found reduced probability of lumpfish occurrence in areas which currently support roe harvest and cleaner fish industry. Future conservation of the species and fisheries management should account for changes in lumpfish distribution as the range shifts northward. [ABSTRACT FROM AUTHOR]

Atlantic Goliath Grouper, Epinephelus itajara, the largest grouper in the western North Atlantic, exhibits life history characteristics (e.g., it is slow-growing, long-lived, and late-maturing) that make it particularly susceptible to fishing pressure. Otoliths, the structure typically processed for age determination, are usually collected as part of fishery monitoring, but otoliths are not available from Goliath Grouper due to a harvest moratorium enacted in 1990 for United States waters. Alternative structures—such as dorsal fin rays or spines—can be acquired for ageing via nonlethal sampling and may provide reliable age estimates. Since 2006, the Florida Fish and Wildlife Conservation Commission (FWC) has been collecting incidental Goliath Grouper samples from mortality events including those from cold kills and red tides. Corresponding otolith, dorsal fin ray and dorsal fin spine samples were compared to determine the accuracy and precision of the external ageing structures. Marginal increment analyses indicated that annulus (translucent zone) deposition occurred primarily in March–June on spines and in April–June on rays. While ages determined from both rays and spines exhibited high precision, the accuracy compared to otolith ages was low as a result of systematic underageing of both external structures, particularly at the oldest age classes. A correction factor was applied to rays and spines that remedied the underageing, but the correction factor was more successful for spines. An analysis of ray and spine section accuracy based on nonlethal structure removal from the fish (i.e., comparing ages from sections at the base of the structure within the body to those sectioned from the external surface of the body) determined that spines can be accurately aged when sampled distal of the base of the structure, but that rays cannot. Nonlethal sampling and ageing of Goliath Grouper spines facilitated by public participation could address management goals and help determine the offshore population age structure. Simultaneously, it could contribute critical data needed for a traditional stock assessment, should such a path be warranted by the recovery or management of the species. [ABSTRACT FROM AUTHOR]

There are many syntheses on the role of animal behavior in understanding and mitigating conservation threats for wildlife. That body of work has inspired the development of a new discipline called conservation behavior. Yet, the majority of those synthetic papers focus on non-fish taxa such as birds and mammals. Many fish populations are subject to intensive exploitation and management and for decades researchers have used concepts and knowledge from animal behavior to support management and conservation actions. Dr. David L. G. Noakes is an influential ethologist who did much foundational work related to illustrating how behavior was relevant to the management and conservation of wild fish. We pay tribute to the late Dr. Noakes by summarizing the relevance of animal behavior to fisheries management and conservation. To do so, we first consider what behavior has revealed about how fish respond to key threats such as habitat alteration and loss, invasive species, climate change, pollution, and exploitation. We then consider how behavior has informed the application of common management interventions such as protected areas and spatial planning, stock enhancement, and restoration of habitat and connectivity. Our synthesis focuses on the totality of the field but includes reflections on the specific contributions of Dr. Noakes. Themes emerging from his approach include the value of fundamental research, management-scale experiments, and bridging behavior, physiology, and ecology. Animal behavior plays a key role in understanding and mitigating threats to wild fish populations and will become more important with the increasing pressures facing aquatic ecosystems. Fortunately, the toolbox for studying behavior is expanding, with technological and analytical advances revolutionizing our understanding of wild fish and generating new knowledge for fisheries managers and conservation practitioners. [ABSTRACT FROM AUTHOR]

This study provides the first socio-ecological overview of the Seriola dumerili fishery occurring in the Balearic Islands. This pelagic top-predator is among the five most valued fish resources of the Balearic community. Despite its ecological importance and potential vulnerability to aggregation fishing, few studies address the ecology of this large Carangidae species. Shining a light on its ecology is vital to ensure adequate species conservation and the sustainable and effective management of the fishery. Historical catches from 1950–1999, alongside detailed landing data for the last 21 years, were analysed to identify potential patterns in ecological and socio-economic factors. Significant inter-annual variability among the years was found in historical catches of greater amberjack, while catches and mean prices of the different size categories revealed significant results between seasons and months, respectively. Additionally, the purse seine fleet accounted for the highest percentage of S. dumerili catches. CPUE did not appear to change greatly between months and years after the annual 8-month fishing ban imposed in 2011 and therefore a re-evaluation of the closure was intended. Overall, this study suggests seasonality influences the S. dumerili fishery in the Balearic Islands, within which ecological influences show a higher regulating power than socio-economic factors. [ABSTRACT FROM AUTHOR]

Inland fishing is an essential activity for the livelihood and food security the Colombian population. The knowledge and evaluation of exploited fish stocks is a priority to develop sustainable management and conservation strategies of the fisheries. To optimize the management processes of fishery resources and conservation of species, it is necessary to evaluate the population structure and identification of stocks. Geometric morphometrics analysis have shown useful in the evaluation of fish stocks. This study focuses on the species Plagioscion magdalenae, commonly called "Pacora", corvinata, or river croaker, which belongs to the family Sciaenidae, a family characterized as an important fishery resource. With the aim of generating a baseline about the state of the P. magdalenae population structure, samples were collected along the marshy complex of the Dique channel, Colombia, between December 2020 and October 2021. In this study, the existence of morphometric variability between individuals of Plagioscion magdalenae was found across sampling sites, Ciénaga de Capote and Ciénaga del Jobo; shape differences between location suggest the action of environmental pressures and the existence of anthropogenic pressures, such as unsustainable artisanal fishing. [ABSTRACT FROM AUTHOR]

Florida promotes itself as the fishing capital of the world, and fishing is one of the state's most popular recreational activities. As the state faces increasing anthropogenic and natural environmental stressors, effective resource management is of paramount importance in sustaining healthy fisheries. The Fisheries Independent Monitoring (FIM) program of the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute regularly monitors relative abundance of various size and age classes of multiple sport fish species (e.g., Centropomus undecimalis common snook, Sciaenops ocellatus red drum, Cynoscion nebulosus spotted seatrout) to provide timely data to fisheries managers. The FIM program samples seven major Florida estuaries, including four that the National Estuary Program has designated as estuaries of national significance (Tampa Bay, Sarasota Bay, Coastal and Heartland, and Indian River Lagoon). Although the FIM program sampling design is consistent and results are comparable among estuaries, the environmental perturbations, available habitats, habitat use by resource species, and recruitment dynamics vary, which can result in different abundance trends among estuaries. The goal of this study was to assess the role of early life stages as refuges for adult populations for two inshore sport fish species and examine their potential in forecasting relative abundance of fishery stocks. We present long-term abundance trends and assess lagged regressions among size or age classes to reveal the importance of size class refuges and identify preferred habitats that are estuary- and age class-specific, providing tools for better managing fishery stocks and habitats. [ABSTRACT FROM AUTHOR]

Physical and hydrologic connectivity among river–reservoir ecosystem (RRE) segments, including the river, river–reservoir interface (RRI), and reservoir, requires consideration of management at larger spatial scales. Multiple objectives (e.g., ecosystem function, sport fisheries, and maximizing fish diversity) seem well suited to this broad spatial scale; however, data limitations regarding the distribution of taxa within RREs currently hamper such an approach. We quantified the fish assemblage of the Trinity River–Lake Livingston ecosystem in Texas, USA, using a stratified approach to determine the contribution of individual segments to the overall fish assemblage. In general, fish assemblages varied along a continuum from the river to the reservoir; however, fish assemblages in several river backwaters did not follow this gradient, thus adding diversity to the overall RRE. Variability in fish assemblages among ecosystem segments was the result of both species composition and relative abundance. Species richness (N = 58 total) was highest in the river segment (N = 49) followed by the RRI (N = 46) and was much lower in the reservoir (N = 36). In contrast, average catch per standardized unit of sampling effort (all species combined) was greatest in the RRI, about 25% lower in the reservoir, and about 50% lower in the river. Across the ecosystem, 26 species (45%) were considered common, while 32 species (55%) were considered rare. Notably, species of conservation need were not always most abundant in river habitats, and species supporting recreational fisheries were not always most dominant in the reservoir. These findings suggest that the RRE can serve as an appropriate spatial scale for both conservation and recreational fishery management actions. [ABSTRACT FROM AUTHOR]

Simple Summary: In recent decades, societies, states and local authorities have become increasingly aware that for effective long-term management and protection of aquatic ecosystems and populations, it is necessary to take into account the genetic changes occurring in these populations. One type of high-resolution molecular marker suitable for studying the neutral and adaptive genetic diversity of populations is single nucleotide polymorphism (SNP). This review is an attempt to show the benefits of using SNPs to recognize natural populations of aquatic animals and detect the threats to them from accidentally or intentionally released farm animals, fishery and global climate changes. It is postulated that conservation actions should protect not only pristine natural populations that are endangered or overfished, but also protect populations of non-threatened species from unnecessarily released semi-domesticated animals. The enhancement of natural populations with farmed material usually reduces their genetic diversity. Experimental size-selective catches of artificially created populations have caused evolutionary changes in the life cycles of fishes. However, fishery-induced evolution in natural populations is difficult to observe. The negative measurable effects on populations can be expected when the number of breeding individuals is reduced below 100, which occurs very rarely in the sea and more often in fragmented freshwater streams, ponds and seasonal rivers. An increasing number of aquatic species have been studied for genetic polymorphism, which extends the knowledge on their natural populations. One type of high-resolution molecular marker suitable for studying the genetic diversity of large numbers of individuals is single nucleotide polymorphism (SNP). This review is an attempt to show the range of applications of SNPs in studies of natural populations of aquatic animals. In recent years, SNPs have been used in the genetic analysis of wild and enhanced fish and invertebrate populations in natural habitats, exploited migratory species in the oceans, migratory anadromous and freshwater fish and demersal species. SNPs have been used for the identification of species and their hybrids in natural environments, to study the genetic consequences of restocking for conservation purposes and the negative effects on natural populations of fish accidentally escaping from culture. SNPs are very useful for identifying genomic regions correlated with phenotypic variants relevant for wildlife protection, management and aquaculture. Experimental size-selective catches of populations created in tanks have caused evolutionary changes in life cycles of fishes. The research results have been discussed to clarify whether the fish populations in natural conditions can undergo changes due to selective harvesting targeting the fastest-growing fishes. [ABSTRACT FROM AUTHOR]

Simple Summary: The whitemouth croaker Micropogonias furnieri is an important fishery resource on the southwest Atlantic coast. Despite being heavily exploited, there are a few uncertainties regarding the population structure in the transition area between the tropical and warm temperate zones (South Brazilian Bight). In the State of Rio de Janeiro (the northern part of this area), local environmental conditions, such as an upwelling phenomena and large estuarine bays, together with contributions of continental drainage and anthropogenic activities, could determine different croaker populations. The aim of this study was to assess the fine-scale population structure of this species in three localities in Rio de Janeiro State (Brazil) and to compare it with previous studies that used different approaches. Through the combined use of genetic markers (nuclear microsatellites) and otolith signatures (morphometry and chemistry), two genotypic (North + Center/South) and three phenotypic (North + Center + South) populations were found. These results could contribute to a better understanding of the M. furnieri population dynamics and allow a rational management of this important fishing resource. The inshore area of the Southwestern Atlantic between 22 °S and 29 °S (South Brazilian Bight) is a transitional climatic zone, where the tropical and warm temperate provinces mix. In its northern part, i.e., in the coastal waters of Rio de Janeiro, Brazil, local oceanographic conditions, such as upwelling in the north, and great bays with different degrees of anthropogenic influences in the center and south can determine the population structure of several fish stocks. The Whitemouth croaker (Micropogonias furnieri) is one the most heavily exploited fishing resources in this area, but there are still some doubts about its population structure. In this study, through combined analyses using nuclear genetic markers and morphological and geochemical signatures of otoliths, a divergence of individuals between two populations was identified using microsatellites, while a finer spatial structure with three populations (north, center and south, respectively) was found based on otolith shapes and elemental signatures. This regional population structure may have direct implications for rational fisheries management and conservation of the species. [ABSTRACT FROM AUTHOR]

Major international agreements governing the shared use of transboundary waters rarely deal explicitly with species conservation, yet they often have major implications for aquatic, avian, and terrestrial species. To meet conservation objectives, it may be necessary to find flexibility, or "adaptive capacity" within these agreements to enable conservation measures. This study applies incident analysis to assess the adaptive capacity of the Canada–US Columbia River Treaty (CRT) to respond to evolving species conservation needs. Like many other transboundary agreements, the terms of the CRT cover power production, flood protection and irrigation, but not species conservation. We analyze the discourses and normative expectations of politically relevant actors regarding an international conflict with Canada over the use of flow modifications by US agencies to conserve an endangered species of sturgeon. Four distinct discourse coalitions formed around the issue, each with its own interpretation of the problem, normative expectations about the rules that should apply, and power to shape decision making. The incident highlights how domestic conservation laws can directly impinge upon an international transboundary water treaty, and how flexibility can be found within existing institutional arrangements for conservation purposes. However, new norms for fish conservation were not fully incorporated into the CRT and decision-making authority for conservation-related disputes became more entrenched in the Treaty's implementing agencies, potentially further excluding actors who might support fish conservation, such as environmental organizations and Indigenous governments. We recommend strategies to increase the adaptive capacity of the CRT and similar international agreements to enable species conservation. [ABSTRACT FROM AUTHOR]

Human-bear (Ursus spp.) interactions (HBI) commonly occur in residential areas throughout North America. Negative HBI can be alleviated by using bear-resistant garbage cans (BRC) and by securing other bear attractants (e.g., bird feeders). Since the early 2000s, human and Florida black bear (U. americanus floridanus) densities have increased substantially throughout Florida, USA, concurrently producing an increase in HBI. In central Florida, an area with high densities of humans and black bears, we surveyed 2 neighborhoods that occurred in an urban ordinance zone established in 2016 that required residents to secure anthropogenic food sources. Residents were supplied with BRC in 2017, and our surveys in 2017 and 2018 assessed the changes in HBI in the year before and after receiving BRC as well as the attitudes of residents toward ordinance measures and the perceived effectiveness of BRC. We found that a combination of preventive measures practiced by residents along with use of BRC effectively reduced HBI by 54%, especially bears eating garbage (reduced to 0%). Consequently, residents spent more time outdoors in their neighborhoods and experienced an elevated quality of life because fear of HBI lessened. We also analyzed public calls to the Florida Fish and Wildlife Conservation Commission concerning HBI. Public calls declined during the 5 years after the ordinance was established compared to 5 years prior. A reduction in HBI (especially conflicts) and public acceptance of using BRC is a long-term goal for management of black bears in Florida. [ABSTRACT FROM AUTHOR]

Diet plasticity is a common behavior exhibited by piscivores to sustain predator biomass when preferred prey biomass is reduced. Invasive piscivore diet plasticity could complicate suppression success; thus, understanding invasive predator consumption is insightful to meeting conservation targets. Here, we determine if diet plasticity exists in an invasive apex piscivore and whether plasticity could influence native species recovery benchmarks and invasive species suppression goals. We compared diet and stable isotope signatures of invasive lake trout and native Yellowstone cutthroat trout (cutthroat trout) from Yellowstone Lake, Wyoming, U.S.A. as a function of no, low-, moderate-, and high-lake trout density states. Lake trout exhibited plasticity in relation to their density; consumption of cutthroat trout decreased 5-fold (diet proportion from 0.89 to 0.18) from low- to high-density state. During the high-density state, lake trout switched to amphipods, which were also consumed by cutthroat trout, resulting in high diet overlap (Schoener's index value, D = 0.68) between the species. As suppression reduced lake trout densities (moderate-density state), more cutthroat trout were consumed (proportion of cutthroat trout = 0.42), and diet overlap was released between the species (D = 0.30). A shift in lake trout δ13C signatures from the high- to the moderate-density state also corroborated increased consumption of cutthroat trout and lake trout diet plasticity. Observed declines in lake trout are not commensurate with expected cutthroat trout recovery due to lake trout diet plasticity. The abundance of the native species in need of conservation may take longer to recover due to the diet plasticity of the invasive species. The changes observed in diet, diet overlap, and isotopes associated with predator suppression provides more insight into conservation and suppression dynamics than using predator and prey biomass alone. By understanding these dynamics, we can better prepare conservation programs for potential feedbacks caused by invasive species suppression. [ABSTRACT FROM AUTHOR]

Understanding the scale of fish movements is essential to establish appropriate fisheries management boundaries. In Florida (USA), Permit (Trachinotus falcatus) is a valued recreational species as a sportfish and as table fare. The Permit fishery in Florida occurs in two geographic sectors: (1) in the Florida Keys and in Biscayne Bay, most anglers value Permit as a sportfish and generally practice catch and release; (2) north of the Florida Keys and Biscayne Bay, where a higher proportion of anglers are harvest oriented. In 2011, the Florida Fish and Wildlife Conservation Commission (FWC) established a Special Permit Zone (SPZ) in the Florida Keys and Biscayne Bay to reduce harvest and to improve the shallow water flats fishery, but maintained regulations friendly to the harvest fishery in the remainder of the state. To determine the extent to which the SPZ is an effective spatial management tool to protect the South Florida sportfish fishery, we used a state-wide mark-recapture program and acoustic telemetry focused on tracking the northern fishery. Between March 2010 and August 2019, anglers dart tagged 1488 Permit, and we acoustically tagged 17 Permit. Only 28 dart-tagged fish were recaptured during the study period and just two of those had moved across the SPZ boundary; in addition, only one of the 17 telemetered fish migrated southward and was detected 3 km south of the SPZ boundary. These results corroborate previous research of Permit movements in the SPZ which also showed infrequent movement across the SPZ border. Thus, it appears that the current spatial approach to management of Permit in south Florida is appropriate. [ABSTRACT FROM AUTHOR]

Anthropogenic habitat alteration is a threat to biodiversity globally. Challenges to conservation are often related to lack of data and public awareness of conservation importance. In terrestrial conservation, these challenges have predominately been addressed using surrogate species. This includes umbrella species, whose ecological needs are known and encompass the needs of many other species that depend on the same habitats. Lack of public support for conservation has been addressed using flagship species, which are selected based on non-biological characteristics to promote public awareness of conservation needs and increase support for habitat conservation. Mangroves are the most threatened coastal habitats. Here, we test the hypothesis that the fish common snook (Centropomus undecimalis), an obligate user of mangrove creeks and other transitional coastal habitats as juveniles, is an appropriate umbrella species for habitat conservation. We examined data spanning 16 years across 27 mangrove creeks and show that protecting habitat use by juvenile snook protects an ecologically important fish assemblage of more than 55 native species, further adding value to mangrove habitats. In addition, because snook support an economically important recreational fishery with a high public profile comprised of fishers with increasing interests in conservation, snook is also an appropriate flagship species that will help leverage collaboration between the recreational fishery stakeholders and the agencies tasked with fishery management. [ABSTRACT FROM AUTHOR]

Wild fish populations are unceasingly diminishing in the rivers, ox‐bow lakes and floodplains in the Southwestern region of Bangladesh. Investigating the population status of vulnerable wild fish species are vital for the management and conservation of that species. This study aimed to identify the intra‐specific morphological variation and determine the population status of Lepidocephalichthys annandalei, in two rivers, the Nabaganga River in Jhenaidah (NRJ) and the Bhairab River in Jashore (BRJ) as well as a flood plain, the Dhakuria Beel in Jashore (DBJ) from Southwestern Bangladesh. Significant differences were observed in seven conventional and five truss‐based characters in univariate statistics. Conventional and truss‐network results from principal component analysis and CVA exhibited that populations were entirely intermixed, creating a compact cluster within intra‐population stages. Four principal components explained 51.93% of the variation in conventional morphometric characters and truss‐based characters. A UPGMA dendrogram was independently developed based on conventional and truss‐based morphometric characters. Among the individuals of NRJ and BRJ populations confirmed the presence of out‐group rather than the DBJ based on morphometric (conventional and truss) features. These notable isolations of populations of this species were supposed to be geographic disconnection and abiotic parameters. The evidence ensuing from the present study would be valuable for genetic studies as well as for in situ management. [ABSTRACT FROM AUTHOR]

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Recreational shark fisheries have been the subject of recent public attention because of the possible impacts on shark populations and conflicts between stakeholders.A case study is presented based on discussions that took place in summer 2018 about potential changes to policies regulating recreational land‐based shark fishing in Florida. Comments from public meetings and workshops (totalling 15.8 hours) and online comments (1,050) submitted to the Florida Fish and Wildlife Conservation Commission (FWC) were analysed using the lens of actor–network theory.The case study explores the intersection of conflicting stakeholder interests and types of knowledge, including how stakeholders variously defined the problem of user conflict in a coastal public space, and how they aligned themselves in relation to the problem and to each other. It further illustrates how shifting values and norms can intersect with changing technologies and environmental realities to produce new or increasing conflicts between natural resource user groups.This study underlines the importance and potential benefits of regulatory agencies explicitly and transparently engaging with value trade‐offs when managing conflicts among users of natural resources. [ABSTRACT FROM AUTHOR]

The Tonle Sap Lake in Cambodia supports several species of threatened megafish and contains one of the largest networks of freshwater fish reserves in the world. Despite these traits, this system remains understudied in terms of its utility for endangered fish conservation and restoration. This study was the first of a series of planned fish releases designed to test the effectiveness of conservation supplementation programs in the Tonle Sap Lake. In March 2022 (during the dry season), 1582 captive-reared fishes, including 1538 striped catfish Pangasianodon hypopthalmus, 42 giant barb Catlocarpio siamensis, and two Mekong giant catfish Pangasianodon gigas, were tagged and released into a 986-hectare fish reserve to assess post-release dispersal and survival. Brightly colored external tags with unique identification numbers were used to facilitate tag returns. A high-profile release event was held to raise awareness about the activity, bringing attention to the importance of fish reserves and endangered species conservation, and disseminating information about the research and tag return and reward program. This, in concert with other efforts, served to be an important education and outreach tool and increased tag return rates. We found that mortality from fishing was rapid and very high. Nineteen percent of released fishes were recaptured in the first 2 days after the fish release, and 46% were recaptured by day 83 after the release, indicating intense fishing pressure on the Tonle Sap Lake fisheries. Eighty percent of recaptured fishes were caught in stationary gill nets, most within 10 km of the release site. Fishing mortality rates were independent of fish size or source (pond-reared or cage-reared). Environmental DNA (eDNA) was found to be capable of detecting each of these species' presence in the water at the release site and could prove to be a useful tool for endangered species monitoring and restoration. Future research should explore alternative release timing, release location, and other methods of increasing post-release survival. Ultimately, underlying sources of mortality, especially fishing, will need to be addressed for conservation supplementation programs to succeed in the Tonle Sap Lake. Conservation supplementation should not be viewed as a substitute for more fundamental conservation measures, such as maintenance of environmental flows, preservation of ecological connectivity, and science-based fisheries management. [ABSTRACT FROM AUTHOR]

Hydrological variations affect habitat characteristics and fish distribution in floodplain lakes. Assessing the contributions of the local community (i.e., LCBD, community uniqueness) and species to overall β diversity (i.e., SCBD, species uniqueness) of fish assemblages is valuable for habitat and species conservation planning, particularly from functional and phylogenetic perspectives. We examined the changes in multifaceted LCBD and SCBD of fish across different hydrological periods in the Poyang Lake, China, and analyzed their responsive mechanisms using regression models, based on which the conservation priorities of habitats and species were evaluated. The findings revealed that taxonomic, functional, and phylogenetic LCBD and SCBD were lowest during the wet season compared to the normal and dry seasons, emphasizing the regulatory effects of hydrological regimes on fish assemblages. Taxonomic and functional LCBD were significantly impacted by the mean abundance of migratory fish, highlighting the importance of specific species combinations on community uniqueness. Taxonomic and functional SCBD exhibited positive correlations primarily with mean abundance, suggesting the potential uniqueness of certain common species. Additionally, we identified the river-lake junction (Hukou station) and natural reserve (Xingzi and Nanjishan stations) with high overall community uniqueness as critical habitats. We also emphasized the necessity for increased conservation efforts for species having high overall species uniqueness during different hydrological periods, including Coilia brachygnathus , Ctenopharyngodon idella , Coilia nasus , Saurogobio dabryi , Hypophthalmichthys molitrix , Megalobrama amblycephala , and Parabramis pekinensis. This research underscores the significance of integrating multiple ecological perspectives to manage biodiversity changes and maintain ecological conservation values effectively. • Hydrological changes regulated the multifaceted community and species uniqueness. • Taxonomic and functional community uniqueness positively responded to biotic factor. • The dominant species displayed high taxonomic and functional species uniqueness. • The multifaceted LCBD and SCBD helps prioritize conserving key areas and species. [ABSTRACT FROM AUTHOR]

Trophic ecology studies on predator–prey interactions reveal insights into ecological communities and help understand a species' role in the food web by contributing to improved fisheries management and conservation capabilities. Understanding the ecological role of overexploited and endangered predators is essential to deciphering how their feeding behaviour influences food web dynamics. In this study, the authors investigated the feeding behaviour of the common and IUCN‐listed Near Threatened (NT) thornback ray Raja clavata, using carbon and nitrogen stable isotope and stomach content analysis (SCA). It has recently suffered an 87% decline in reported catches from the Sea of Marmara within the last decade. These results show that thornback ray mainly feeds on teleost species, except in summer, with both methods showing this species changes its diet ontogenetically by SCA. This ontogenetic diet shift was at lengths 40–50 cm by changing group preferences from Crustacea to Teleostei. MixSIAR results showed that both adult and juvenile individuals of R. clavata feed mainly on the crustaceans, but the contribution of teleosts represented by Trachurus sp. was very low (<15%). The trophic position increased total length and was higher than other batoid species in the Sea of Marmara. [ABSTRACT FROM AUTHOR]

Actinopyga echinites are among the commercially exploited sea cucumbers; however, limited studies hinder the management interventions for the sustainability of the resource. This study investigates the density and size distribution of A. echinites populations in Cabgan Island, Barobo, Surigao del Sur from March-August 2021 with two stations (shallow seagrass beds as Station 1 and algal flats as Station 2) having three plots (100 m²) laid as monitoring stations. The results revealed the population density of A. echinites ranged from 567-2,567 ind/ha with a mean of 1,572 ± 225 ind/ha in Station 1 and 733-2,400 ind/ha and a mean of 1,389 ± 178 ind/ha in Station 2. Significant differences were only observed across months in each station (P = 0.00) and their interaction between months and stations (P = 0.01). A. echinites had a mean length of 7.58 ± 0.26 cm and weight of 31.39 ± 1.62 g for Station 1 and 7.84 ± 0.47 cm and 39.01 ± 3.91 g for Station 2. Specimens in Station 2 had a greater length and significantly heavier weight than in Station 1 (P = 0.00). Across months, significant differences were recorded for the specimen's length in Station 1 and weight for both stations. The length of A. echinites ranged from 4-12 cm and 4-13.5 cm in Stations 1 and 2, respectively, and weight of 5-129 g in both stations. The highest frequencies were recorded at 7 cm in both stations and shifted to 9 cm. Weight distributions showed the highest frequencies in 35 g in the two stations. The present study shows that the population is still abundant and is more influenced by the sampling months than the stations. The species are smaller compared to other studies and might exhibit habitat preferences. Weight size distribution varied across months and could be related to their reproduction. The study provides significant insights needed for this species' conservation and fishery management. [ABSTRACT FROM AUTHOR]

The queen conch (Aliger gigas) is a culturally and economically important molluskan fishery resource in the Caribbean region showing increasing signs of over harvest. Shallow-water distribution and large size facilitate capture, and internal fertilization and density-dependent reproduction make managing for reproductive biology critical to stock rehabilitation. In fact, the natural lifetime fecundity of conch is very high but most fisheries in the region harvest conch before even a small fraction of that reproductive potential can be attained. The goal of this review is to provide an up-to-date synthesis of the vast research literature on queen conch biology (spanning >60 years) and to discuss how knowledge of reproduction in conch can help to guide field surveys, fishery management decisions, and stock recovery projects. The review covers the subjects of anatomy, maturation and fecundity as they relate to conch age and size, reproductive behavior including migrations, seasonality, mating, and egg-laying, and the influences of both environmental and demographic variables on reproductive potential. Successes and failures under different forms of management practice are discussed as they relate to reproductive biology and recommendations are made for future research and fishery management alternatives. Successful management will require multiple regulatory approaches. [ABSTRACT FROM AUTHOR]

Understanding the effects of hydrology on fish populations is essential to managing for native fish conservation. However, despite decades of research illustrating streamflow influences on fish habitat, reproduction, and survival, biologists remain challenged when tasked with predicting how fish populations will respond to changes in flow regimes. This uncertainty stems from insufficient understanding of the context‐dependent mechanisms underlying fish responses to, for example, periods of reduced flow or altered frequency of high‐flow events. We aim to address this gap by drawing on previous research to hypothesize mechanisms by which low and high flows influence fish populations and communities, identifying challenges that stem from data limitations and ecological complexity, and outlining research directions that can advance an empirical basis for prediction. Focusing flow ecology research on testing and refining mechanistic hypotheses can help narrow management uncertainties and better support species conservation in changing flow regimes. [ABSTRACT FROM AUTHOR]

Aquatic food‐web studies involving fish and using stable isotope analysis typically sample fish white muscle, which generally requires the fish to be euthanised. Alternatively, fin tissue can be sampled non‐lethally, avoiding the need to euthanise an animal to obtain what is usually a relatively small tissue sample. We set out to develop equations for converting δ13C and δ15N values from derived non‐lethally sampled fin tissue to equivalent white muscle tissue, for use in food‐web studies. We explored δ13C and δ15N values of paired fin‐clips and white muscle from two species of anguillid fishes, the endemic longfin eel (Anguilla dieffenbachii), and the Australasian shortfin eel (A. australis), sourced from multiple studies spread throughout New Zealand. We also examined the effect of lipid extraction on δ13C and δ15N, which reduced variability of δ13C when compared to untreated samples. We were also able to estimate δ13C values of equivalent lipid‐extracted muscle samples directly from untreated fin. For δ15N, paired untreated fin and muscle values were not statistically different so fin δ15N can be used as a direct estimate of muscle δ15N. Solvent lipid extraction with a methanol–chloroform mixture, however, altered δ15N values and increased variability, so should be avoided. We present equations to estimate lipid‐corrected δ13C values of muscle tissue for use in stable isotope studies of freshwater anguillids, avoiding euthanasia. Our results demonstrate that δ13C and δ15N values can be accurately derived from non‐lethally obtained fin clips, reducing unnecessary mortality in fish species of conservation concern. [ABSTRACT FROM AUTHOR]

The article discusses the Great Goliath Grouper Count (GGGC), a program initiated in 2010 by Florida Sea Grant and the Florida Fish and Wildlife Conservation Commission (FWC) to collect data on the Atlantic goliath grouper. The goliath grouper is a large reef species that was overfished and experienced population declines in the past. The GGGC utilizes trained divers who follow standardized protocols to report data on the number, size, and location of goliath groupers observed during underwater surveys. The program has expanded to include the entire state of Florida and has provided valuable data for stock assessments and fisheries management. [Extracted from the article]

A lack of an updated checklist of freshwater fish species from Lake Dongting is a great hindrance to further biodiversity analysis. A seasonal survey of fishes in the lake was conducted from October 2017 to January 2019. Based on the data obtained during the field survey and coupled with known literature and the latest taxonomic development of relevant taxa, the species checklist of fishes from Lake Dongting was updated. A total of 130 species from 12 orders, 30 families and 76 genera has been documented, containing 126 native species and four alien species. Its fish fauna is dominated by the Xenocyprididae that has the highest number of included species (30), followed by the Gobionidae (25) and Acheilognathidae (11). This checklist comprises 20 species undergoing nomenclatural changes and 11 new records, eight of which are native and three exotic. It excludes 20 species, which have been reported in error in historical works, due to synonyms, erroneous records, taxonomic changes and unconfirmed records. Unsampled in this survey were 34 species that are ecologically specialised: migratory, rheophilic, predatory, shellfish-dependent or pelagic-egg-spawning. While some of these species eluded capture likely due to the paucity of population, others may have been extirpated in Lake Dongting perhaps owing to human perturbations, such as river damming across affluents or the Chang-Jiang mainstem, sand dredging, overfishing or water pollution. The updated checklist lays a sound foundation for biodiversity conservation of fishes in Lake Dongting. [ABSTRACT FROM AUTHOR]

Globally, policies aiming for conservation of species, free‐flowing rivers, and promotion of hydroelectricity as renewable energy and as a means to decarbonize energy systems generate trade‐offs between protecting freshwater fauna and development of hydropower. Hydroelectric turbines put fish at risk of severe injury during passage. Therefore, comprehensive, reliable analyses of turbine‐induced fish mortality are pivotal to support an informed debate on the sustainability of hydropower (i.e., how much a society is willing to pay in terms of costs incurred on rivers and their biota). We compiled and examined a comprehensive, global data set of turbine fish‐mortality assessments involving >275,000 individual fish of 75 species to estimate mortality across turbine types and fish species. Average fish mortality from hydroelectric turbines was 22.3% (95% CI 17.5–26.7%) when accounting for common uncertainties related to empirical estimates (e.g., handling‐ or catch‐related effects). Mortality estimates were highly variable among and within different turbine types, study methods, and taxa. Technical configurations of hydroelectric turbines that successfully reduce fish mortality and fish‐protective hydropower operation as a global standard could balance the need for renewable energy with protection of fish biodiversity. [ABSTRACT FROM AUTHOR]