Fish Populations Research Articles

Temporal declines in fecundity: A study of southern Gulf of St. Lawrence Atlantic herring (Clupea harengus) and implications for potential reproductive output.

Individuals must reproduce to survive and thrive from generation to generation. In fish, the fecundity of individuals and estimates of total reproductive output are critical for evaluating reproductive success and understanding population dynamics. Estimating fecundity is an onerous task; therefore, many populations lack contemporary estimates of fecundity and size-fecundity relationships. However, reproductive dynamics are not static in time; therefore, it is important to develop contemporary fecundity estimates to better inform conservation and management action. To highlight the importance of contemporary fecundity estimates, we examined the fecundity of southern Gulf of St. Lawrence (sGSL) spring and fall spawning Atlantic herring in 2022, developed size-fecundity models, and compared these to historical fecundity estimates and models. Our results suggest that the average fecundity of sGSL spring and fall herring has undergone a substantial temporal decline of approximately 47% and 58%, respectively, since the 1970s and 1980s. The size-fecundity relationships for fall spawning herring have shifted, with fish of a given size exhibiting lower fecundity in 2022 compared to the 1970s. Alternatively, the size-fecundity relationships for spring spawning herring have remained relatively static. Furthermore, simulations highlighted a substantial reduction in potential reproductive output in 2022 compared to 1970 of approximately 32% and 68% for spring and fall spawners, respectively, based on a fixed number of mature females, which may have negative implications for stock rebuilding. Overall, our study provides support for periodic estimates of fecundity in fish populations to better understand temporal changes in reproductive and population dynamics.

A comprehensive study of spatial spread and multiple time delay in an eco-epidemiological model with infected prey

This paper studies the dynamics of interacting Tilapia fish and Pelican bird population in the Salton Sea. We assume that the diseases spread in Tilapia fish follows the Holling type II response function, and the interaction between Tilapia and Pelican follows the Beddington–DeAngelis response function. The dynamics of diffusive and delayed system are discussed separately. Analytically, all the feasible equilibria and their stability are discussed. The criterion for Turing instability is derived. Based on the normal form theory and center manifold arguments, the existence of stability criterion and the direction of Hopf bifurcation are obtained. Numerical simulation shows the occurrence Hopf bifurcation, double Hopf bifurcation and transcritical bifurcation scenarios. The snap shot shows the spot, spot-strip mix patterns in the whole domain. Further, the stability switching phenomena is observed in the delayed system. Our comprehensive study highlights the effect of different parameters, multiple time delay and extinction in Pelican populations.

Density estimation of the globally threatened fishing cat Prionailurus viverrinus through a participatory science approach in the Chilika lagoon, eastern India

The fishing cat Prionailurus viverrinus is an Indo-Malayan wetland-dependent felid which is listed as Vulnerable on the IUCN Red List. Its main prey, fish, has low energetic demands and is abundant in productive aquatic habitats. This facilitates high piscivore densities and potentially alters expected scaling patterns that link population density to the body mass of small cats. With local community participation, we estimated the density of the fishing cat in Chilika, Asia’s largest brackish water lagoon, located in the state of Odisha, eastern India, with community participation. The study was carried out in 2 phases in different habitats during 2021 and 2022: a homogeneous marshy habitat and its buffer (Northern Block), and a heterogeneous matrix of different land-use types (Southern Block). We deployed a total of 144 camera traps across 4380 trap nights. Using spatially explicit capture-recapture (SECR), we estimated mean (±SE) fishing cat density to be 0.69 ± 0.1 ind. km-2 in the Northern Block and 0.67 ± 0.33 ind. km-2 in the Southern Block. The population abundance estimates for the Northern and the Southern Blocks were 159 ± 23 and 185 ± 91 respectively. In the former, SECR modelling indicated an effect of anthropogenic habitat modification upon the species’ home range extent. Our density estimates are amongst the highest reported for the species outside protected areas. The results imply that Chilika holds an abundant population of the fishing cat, the continued persistence of which requires mitigation of local and external threats to fish populations. Furthermore, our study, with its inclusive approach, sets a precedent for the use of camera trapping for obtaining robust density estimates of species with uniquely marked individuals in wetland habitats.

Coding Optimization for an Ecological non-linear Age-structured Fish Population Model with a Shepherd Recruitment Function

The study of the optimally density-regulated recruitment plays a crucial role in the overall management and determining of fishing efforts of marine fish populations. This paper will develop a Matlab code can determine what an optimal recruitment density regulation strategy would be for the un-fished population and what it changes to when fishing efforts are applied. This code can determine threshold values used to avoid fisheries from collapsing. The code will be applied to the Gulf of California Pacific sardine (Sardinops caeruleus) population. An age structured design with a Shepherd density regulating stock-recruitment function is used in this study. In this work, the parameter which is varied is captured in the Shepherd recruitment function and is associated with behavioral interventions such as selecting different drift routes and clumping on resources that will increase egg-larvae survival to the recruitment stage. A detailed background study of other models is explored, then a derivation of the Shepherd recruitment model is developed from the traditional discrete model. A special MATLAB code is then developed to illustrate the pair-wise invasive plots for the model structures. The code is for theoretical analysis of fish population models.

Comparing the Structure of Fish Assemblage among Natural and Artificial Shallow Rocky Habitats

Artificial coastal structures, such as seawalls, breakwaters, and groins, can exert various impacts on the fish communities in the nearby regions. This study focuses on assessing the ecological effects of coastal infrastructure on marine environments, by comparing, at different seasons, the habitat complexity and heterogeneity, as well as their effects on fish assemblages, between the artificial habitat created with the intention of constructing a marina (Puerto Amor) and the natural habitats surrounding the Cabo de la Huerta area in Alicante (Spain). Employing an asymmetric design and examining two temporal and spatial scales, we utilized visual censuses in snorkeling to gauge the abundance and size of fish species, alongside various parameters related to habitat complexity and heterogeneity. The overarching hypothesis is that fish populations associated with artificial habitats will differ in terms of abundance, biomass, species richness, and diversity compared to fish populations associated with natural habitats, due to changes in complexity and heterogeneity. The findings indicate a shift in fish assemblages; for example, the family Labridae showed differences between the two habitat types for several species. These changes were due to the influences of the Posidonia oceanica meadow and algae like Jania rubens; being influenced by biological variables such as Ellisolandia elongata, Oculina patagonica, and Sarcotragus spinosulus; as well as physical variables such as stones, gravel, and blocks. While there is evidence of alteration in fish assemblages due to changes in habitat structure, there is also an increase in richness (9 species/m2) and total abundance and biomass (1000 ind./m2 and 1700 g/m2, respectively) in the artificial habitat. Multivariate analyses reveal that the fish community in Puerto Amor is less homogeneous than the one in the natural habitat. However, these analyses also indicate an overlap between the communities of both habitats, suggesting substantial similarity despite the noted differences. Consequently, although the habitat alteration has impacted fish populations, it has not diminished abundance, biomass, or species richness. In conclusion, the artificial rocky habitat resulting from the construction attempt at Puerto Amor harbor has fish populations with ecological significance and its removal could lead to undesirable impacts in the area, as the fish assemblages have become well established.

Elevated fish densities extend kilometres from oil and gas platforms.

Thousands of offshore oil and gas platforms have been installed throughout the world's oceans and more structures are being installed as part of the transition to renewable energy. These structures increase the availability of ecological niches by providing hard substrate in midwater and complex 3D habitat on the seafloor. This can lead to 'hotspots' of biodiversity, or increased densities of flora and fauna, which potentially spill over into the local area. However, the distances over which these higher densities extend (the 'range of influence') can be highly variable. Fish aggregate at such structures, but the range of influence and any implications for wider fish populations, are unclear. We investigated the relationship between fish and platform areal densities using high resolution fisheries acoustic data. Data were collected in the waters surrounding the vessel exclusions zones around 16 oil and gas platforms in the North Sea, and throughout the wider area. We estimated densities of schooling fish using echo-integration, and densities of non-schooling fish using echo-counting. At 10 platforms, non-schooling fish densities were elevated near the platform relative to background levels in the equivalent wider area. The range of influence, defined here as the range to which fish densities were elevated above background, varied from 0.8 to 23 km. In areas of high platform density, fish schools were encountered more often, and non-schooling fish densities were higher, when controlling for other sources of environmental variation. This is the first time such long-range effects have been identified; previously, ranges of influence have been reported in the order of just 10s-100s of metres. These findings suggest that the environmental impact of these structures may extend further than previously thought, which may be relevant in the context of upcoming management decisions around the decommissioning of these structures.

Insights into the discovery and intervention of metalloproteinase in marine hazardous jellyfish

The proliferation of toxic organisms caused by changes in the marine environment, coupled with the rising human activities along the coastal lines, has resulted in an increasing number of stinging incidents, posing a serious threat to public health. Here, we evaluated the systemic toxicity of the venom in jellyfish Chrysaora quinquecirrha at both cellular and animal levels, and found that jellyfish tentacle extract (TE) has strong lethality accompanied by abnormal elevation of blood biochemical indicators and pathological changes. Joint analysis of transcriptome and proteome indicated that metalloproteinases are the predominant toxins in jellyfish. Specially, two key metalloproteinases DN6695_c0_g3 and DN8184_c0_g7 were identified by mass spectrometry of the red blood cell membrane and tetracycline hydrochloride (Tch) inhibition models. Structurally, molecular docking and kinetic analysis are employed and observed that Tch could inhibit the enzyme activity by binding to the hydrophobic pocket of the catalytic center. In this study, we demonstrated that Tch impedes the metalloproteinase activity thereby reducing the lethal effect of jellyfish, which suggests a potential strategy for combating the health threat of marine toxic jellyfish.

How fish populations in Lake Bafa (Western Anatolia) respond to ecological shifts

Abstract Long‐term biodiversity monitoring is crucial for freshwater ecosystems as it enables the detection of even subtle changes and biodiversity trends, guiding conservation efforts and ensuring the sustainability of these vital habitats. Despite becoming more commonly considered in the field of freshwater ecology and biological invasions, studies using long‐term time series from Türkiye's freshwater resources have remained scarce. To assess the availability of data and ultimately present a baseline for future efforts, we combined published museum records and samples from recent field studies from the highly anthropogenically‐altered Lake Bafa in Western Anatolia covering the period 1958–2019. Lake Bafa has a very diverse aquatic ecosystem, providing habitat for both freshwater and saltwater species, and is one of the allottees in Türkiye's inland fish production. In the current study, we investigated how fish populations in Lake Bafa were affected by environmental changes and examined changes in taxonomic and functional diversity of non‐native species over time. The analyses revealed—concomitant to an increase in native marine and freshwater species richness—an increase in non‐native species richness over time. Non‐native species did not interfere with native species' niche space, whereas applied models indicate that in this highly altered ecosystem, foremost temperature and salinity shaped the fish community over time, limiting the impacts of non‐native species. These results have implications for the fishery of the lake, which includes highly valuable catadromous fish species, highlighting the value and importance of collecting long‐term data in Türkiye to better understand both invasion dynamics and changes in the naturality of Turkish ecosystems. These findings further underline the importance of long‐term data to create new management strategies for the lake and to start restoration processes, thus improving fisheries management.

Empirical and model‐based evaluation of a step‐pool stream restoration project: Consequences for a highly valued fish population

AbstractObjectiveWe sought to measure a step‐pool restoration project's effects on a steelhead Oncorhynchus mykiss population and explore the capability of process‐based modeling to enhance understanding of the results.MethodsWe used before‐after–control‐impact monitoring in combination with a process‐based, individual‐based, spatially explicit fish population model to evaluate a stream restoration project that reconfigured the channel and primarily added step pools to a reach of a second‐order stream in northwestern California.ResultFive years of monitoring both before (2012–2016) and after (2018–2022) restoration indicated that restoration caused substantial increases in the abundance and biomass of steelhead. Individual growth rates and retention of fish in the study reach did not exhibit consistent patterns, even in the first 2 years after restoration, when fish abundance and biomass exhibited extreme increases of about fivefold. Model simulations predicted about a twofold increase in the abundance and biomass of steelhead in the restoration reach, which corresponded with the empirical results 4–5 years after restoration. The model also predicted a similar increase in the production of steelhead out‐migrants, a response we did not attempt to measure in the field.ConclusionStep‐pool restoration benefitted steelhead. The model's correspondence with empirical observations indicates its potential applicability to more complex resource management questions in the study area, such as how restoration will combine with changes in climate to affect the sustainability of salmonid populations.

Dietary administration impact of olive pulp on growth performance, metabolic profile, immune status, and antioxidant potential of gilthead seabream (Sparus aurata L.)

The use of natural immunostimulants in aquaculture is intended to foster overall health and bolster resilience against diseases in farmed fish populations. It constitutes a crucial strategy that can contribute to securing the sustainability of the aquaculture industry, and it is an area that warrants ongoing exploration and development. Therefore, the aim of the present work was to evaluate the effect of dietary administration of olive pulp on growth rate, metabolic profile, serum antioxidant potential, and humoral and cellular innate immune parameters of gilthead seabream (Sparus aurata L.). For this, fish were fed control diet or olive pulp enriched diets (50, 100, and 200 mg kg feed−1) for 4 weeks. Our results demonstrated that the highest inclusion level improved the growth rates and the biological antioxidant potential in the serum of fish. However, after 4 weeks of feeding, most of the assayed metabolic parameters (Ca2+, TP, ALB, K+, and Na+) were increased in the serum of fish fed with a diet containing the lowest level of olive pulp (50 mg kg feed−1). Regarding the innate immune parameters, the IgM levels decreased in the serum of fish fed 50′s diet after 2 and 4 weeks of trial. However, the serum of fish fed with diets containing 100 and 200 showed an increase in hemolytic complement activity after 2 weeks whilst this increase was only sustained in the 200′s group after 4 weeks. After 2 weeks of feeding, the serum of the fish showed an increase in peroxidase activity due to the highest olive inclusion. Concerning cellular innate parameters, peroxidase activity, respiratory burst, and phagocytic ability were increased in head-kidney leucocytes of fish fed 100′s diet at 2 weeks compared to values from control fish. These results suggest that the administration of olive pulp-enriched diets can benefit fish growth, antioxidant, and immune status of gilthead seabream.

Unveiling the gut bacteriome diversity and distribution in the national fish hilsa (Tenualosa ilisha) of Bangladesh.

The field of fish microbiome research has rapidly been advancing, primarily focusing on farmed or laboratory fish species rather than natural or marine fish populations. This study sought to reveal the distinctive gut bacteriome composition and diversity within the anadromous fish species Tenualosa ilisha (hilsa), which holds the status of being the national fish of Bangladesh. We conducted an analysis on 15 gut samples obtained from 15 individual hilsa fishes collected from three primary habitats (e.g., freshwater = 5, brackish water = 5 and marine water = 5) in Bangladesh. The analysis utilized metagenomics based on 16S rRNA gene sequencing targeting the V3-V4 regions. Our comprehensive identification revealed a total of 258 operational taxonomic units (OTUs). The observed OTUs were represented by six phyla, nine classes, 19 orders, 26 families and 40 genera of bacteria. Our analysis unveiled considerable taxonomic differences among the habitats (freshwater, brackish water, and marine water) of hilsa fishes, as denoted by a higher level of shared microbiota (p = 0.007, Kruskal-Wallis test). Among the identified genera in the gut of hilsa fishes, including Vagococcus, Morganella, Enterobacter, Plesiomonas, Shigella, Clostridium, Klebsiella, Serratia, Aeromonas, Macrococcus, Staphylococcus, Proteus, and Hafnia, several are recognized as fish probiotics. Importantly, some bacterial genera such as Sinobaca, Synechococcus, Gemmata, Serinicoccus, Saccharopolyspora, and Paulinella identified in the gut of hilsa identified in this study have not been reported in any aquatic or marine fish species. Significantly, we observed that 67.50% (27/40) of bacterial genera were found to be common among hilsa fishes across all three habitats. Our findings offer compelling evidence for the presence of both exclusive and communal bacteriomes within the gut of hilsa fishes, exhibiting potential probiotic properties. These observations could be crucial for guiding future microbiome investigations in this economically significant fish species.

Application of environmental DNA metabarcoding to identify fish community characteristics in subtropical river systems

AbstractFish are vital in river ecosystems; however, traditional investigations of fish usually cause ecological damage. Extracting DNA from aquatic environments and identifying DNA sequences offer an alternative, noninvasive approach for detecting fish species. In this study, the effects of environmental DNA (eDNA), coupled with PCR and next‐generation sequencing, and electrofishing for identifying fish community composition and diversity were compared. In three subtropical rivers of southern China, fish specimens and eDNA in water were collected along the longitudinal (upstream–downstream) gradient of the rivers. Both fish population parameters, including species abundance and biomass, and eDNA OTU richness grouped 38 sampling sites into eight spatial zones with significant differences in local fish community composition. Compared with order‐/family‐level grouping, genus‐/species‐level grouping could more accurately reveal the differences between upstream zones I−III, midstream zones IV−V, and downstream zones VI–VIII. From the headwaters to the estuary, two environmental gradients significantly influenced the longitudinal distribution of the fish species, including the first gradient composed of habitat and physical water parameters and the second gradient composed of chemical water parameters. The high regression coefficient of alpha diversity between eDNA and electrofishing methods as well as the accurate identification of dominant, alien, and biomarker species in each spatial zone indicated that eDNA could characterize fish community attributes at a level similar to that of traditional approaches. Overall, our results demonstrated that eDNA metabarcoding can be used as an effective tool for revealing fish composition and diversity, which is important for using the eDNA technique in aquatic field monitoring.

Preserving the Lake Toba ecosystem: Strategic planning to mitigate red devil fish invasion

Lake Toba is known as a tourism destination and also has aquaculture that is utilized for freshwater fish. However, several types of endemic fish and consumable fish cultivated in Lake Toba are facing the threat of extinction, and their populations are decreasing due to the presence of Red Devil Fish. The research aims to explain how the local government’s strategic planning efforts mitigate the invasion of Red Devil Fish and preserve the ecosystem in Lake Toba. This research uses qualitative research with descriptive methods. This research prioritizes secondary data collection that can support research. Data analysis techniques include data reduction, data display, and conclusion. The results showed that the Indonesian government must overcome the problem of red devil fish invasion into the Indonesian aquatic ecosystem. The presence of Red Devil fish in Lake Toba has reduced the number and diversity of fish, including the extinction of several native fish species. The impact of this invasion damages the ecosystem and causes economic losses such as control costs and decreased fish production for public consumption. The local government’s strategic planning in protecting the Lake Toba ecosystem from Red Devil fish invasion is carried out by controlling spatial planning, conducting talks, and collaborating with various related parties. The North Sumatra Provincial Marine and Fisheries Service and the Fish Family Association have implemented strategies to minimize Lake Toba’s Red Devil fish population. Increasing community involvement in managing the Lake Toba ecosystem and reducing the Red Devil fish population is crucial.

SOLUȚII TEHNICE PENTRU ESTIMAREA BIOMASEI CONFORM CONCEPTULUI DE ACVACULTURĂ 4.0

Aquaculture, as a dynamic field, undergoes continuous evolution requiring continuous improvements in efficiency and new research efforts. Estimating fish biomass is an essential practice in the field of precision aquaculture, obtaining periodic information on fish biomass has been identified as an urgent need, considering the objective of optimizing daily feeding, controlling fish density and finally determining the optimal timing of harvesting. Conventional weighing methods, which often rely on manual procedures, have inherent challenges. Manual weighing processes are labor-intensive, requiring substantial time and human resources. Furthermore, manual handling of fish during weighing procedures induces considerable stress on aquatic organisms, potentially compromising their health and welfare. Consequently, there is a pressing need in the aquaculture industry to explore alternative weighing techniques that alleviate stress levels while increasing operational efficiency. In response to these challenges, contemporary research efforts have increasingly focused on the development of noninvasive and automated weighing methodologies. These innovations aim to simplify the weighing process, minimize human intervention and reduce the level of stress experienced by the fish population. However, estimating fish biomass without human intervention presents significant challenges because fish are sensitive and move freely in an environment where visibility, lighting, and stability are difficult to control. The paper analyzes technological solutions for biomass estimation according to the concept of Aquaculture 4.0.

Phylogenomic Characterization of Ranavirus Isolated from Wild Smallmouth Bass (Micropterus dolomieu).

In September 2021, 14 smallmouth bass (SMB; Micropterus dolomieu) with skin lesions were collected from Green Bay waters of Lake Michigan and submitted for diagnostic evaluation. All the skin samples tested positive for largemouth bass virus (LMBV) by conventional PCR. The complete genome of the LMBV (99,328 bp) isolated from a homogenized skin sample was determined using an Illumina MiSeq sequencer. A maximum likelihood (ML) phylogenetic analysis based on the 21 core iridovirus genes supported the LMBV isolated from SMB (LMBV-WVL21117) as a member of the species Santee-Cooper ranavirus. Pairwise nucleotide comparison of the major capsid protein (MCP) gene showed that LMBV-WVL21117 is identical to other LMBV reported from the United States and nearly identical to doctor fish virus and guppy virus 6 (99.2%) from Southeast Asia, as well as LMBV isolates from China and Thailand (99.1%). In addition, ML phylogenetic analysis based on the MCP gene suggests three genotypes of LMBV separated by region: genotype one from the United States, genotype two from Southeast Asia, and genotype three from China and Thailand. Additional research is needed to understand the prevalence and genetic diversity of LMBV strains circulating in wild and managed fish populations from different regions.

Southernmost record of Coryphaena hippurus Linnaeus, 1758 (Coryphaenidae) in the southwest Atlantic Ocean, off Mar del Plata, Argentina

This paper reports the presence of the common dolphinfish, Coryphaena hippurus, in Argentinian waters for the first time, with a specimen collected by experienced sport fishermen near Mar del Plata (38°S). This finding also represents the first record of a species from the Coryphaenidae family in Argentinian waters. The collection of these specimens coincided with sightings of other rarely-seen pelagic and oceanic fish species during the same period, providing further evidence supporting the influx of subtropical fish species from warmer Brazilian waters. These observations highlight the need for continued monitoring of fish populations and their distribution and the ecological dynamics within the region.

Variation in population assemblage of Acanthuridae and Scaridae across human concentration levels during a bleaching event affecting the coral reefs of Guna Yala, Panama

Abstract Coral reefs are the ocean's most productive ecosystem, supporting a huge amount of biodiversity, and are relied upon by millions of people worldwide. As we progress into the Anthropocene, coral reef ecosystems are increasingly threatened by a swath of pressures. Of the most impactful are El-Niño Southern Oscillation-related heat pulses, which result in the bleaching and potential mortality of coral reefs. Bleaching events, in synergy with other threats, are increasing algal-dominated reefs, which impact the productiveness of coral reef ecosystems. Herbivorous fish are the prominent algal consumers and are essential in controlling algal blooms. Species from the family Acanthuridae and Scaridae are the most conspicuous of herbivorous fish on coral reefs, and through a diverse array of physiological differences compose several unique functional groups. The population distribution of Acanthuridae and Scaridae are directly correlated with coral reef characteristics and composition and can suffer from bleaching events as well. Despite their importance in maintaining reef health and improving resilience to disturbances, there is a very scarce collection of literature that describes the population assemblage of Acanthuridae and Scaridae spp. during bleaching events. This study aims to contribute to this underreported phenomenon. Visual surveys of Acanthuridae and Scaridae species were conducted to measure the average density, mean size, and biomass in terms of coral reef characteristics across a human concentration gradient in Guna Yala, Panama. Results suggest a similar overall abundance of herbivorous fish between the two reef locations, with significantly larger sizes and biomass of A. coeruelus, S. aurofrenatum, S. viride, and S. iseri in reefs further away from human concentration. This correlates with significantly higher rugosity on these reefs. The mean size of each respective species appears to be lower than previously reported across the Caribbean. Additionally, the biomass distribution was strikingly skewed by S. viride which corresponds to almost ¾ of the total biomass. This indicates that the current bleaching event is having drastic impacts on the distribution of herbivorous fish populations, which is exacerbated by proximity to human concentration. This can have very negative consequences for the recovery of these reefs following the bleaching event. Of specific concern are the coral reefs closer to humans. Data from benthic composition surveys show that macroalgae cover and overall coral bleaching are significantly higher compared to reefs far from humans. This study provides vital information that may be useful for future studies to identify coral reef resilience to bleaching events through the scope of Acanthuridae and Scaridae population distribution. Lay Summary The ocean is a crucial and largely unexplored part of our planet. One area that has begun to receive sufficient scientific attention is coral reefs. This is because, despite only covering less than 1% of the ocean’s surface, coral reefs support a quarter of all marine life. This rich environment provides more than a billion people with their primary source of protein and offers coastal protection to hundreds of millions of people. However, the future of coral reefs is under threat. Due to climate change and human pressures, coral reefs are facing mortality on a worldwide scale. Of the most lethal are bleaching events, when the water temperature rises past the threshold of coral, and they turn white and die. At the same time, corals face a daily threat from increasing algae coverage, which can smother and kill the coral. These threats have intensified in the recent few decades and may permanently alter the biodiversity and productivity of coral reefs. Understanding these changes is of utmost importance, and one way to do so is to study the animals that eat algae and give coral a chance to thrive—herbivorous fish. This paper analyzes the population distribution of two herbivorous fish families: Acanthuridae (surgeonfish) and Scaridae (parrotfish) during a bleaching event. Learning how a bleachingevent can impact the presence of these essential species among coral reefs has rarely been accomplished in scientific literature, so this paper offers valuable contributions to a more comprehensive understanding of reef health during bleaching events and our changing world.

Status of pink ear emperor (Lethrinus lentjan) fishery in the Sinjai and Bone waters, South Sulawesi, Indonesia

The pink ear emperor (Lethrinus lentjan) is a type of coral fish belonging to the Lethrinidae family, they usually eat mainly at night, namely benthic invertebrates or fish. L. lentcan included in the main family of food coral fish that live in coral reef ecosystems and in sandy bottom coastal waters. Good management of fisheries resources is by utilizing fish populations without having to deplete fishery resources. If fishing is carried out continuously without taking into account the ability to renew, over exploitation will occur. The research was conducted from March to May, 2023, in Sinjai and Bone waters, south sulawesi Indonesia which focused on fishing ports with L. lentjan landing potential. The highest class length was obtained in Sinjai Regency and in Bone regency which was negative allometric. Lc in Sinjai regency uses basic gillnet, and in Bone regency 21.9 uses basic longline. Gender comparison between L. lentjan males and females in Sinjai regency is 45% : 55%. Meanwhile for Bone regency it is 41% : 59%. L. lentjan males and females have a ratio of 1: 1.43 with the results of the chi square test tcount < ttable, this condition shows that H0 accepted, there is no real difference between the number of male and female biota. gonad maturity level L. lentjan in Sinjai regency it is 24 cm with a length range of 23 – 25 cm, and in Bone regency it is 24.6 cm with a length range of 24-25 cm.

Hybrid choice modeling offers an interdisciplinary perspective on angler preferences for the future

Angler decisions are shaped by an interplay between ‘internal’ psychological processes and ‘external’ institutional factors that are equally important yet often evaluated in isolation. We therefore developed a hybrid choice model whereby a structural equation model of behavioral antecedents was integrated with a discrete choice experiment to evaluate competing preferences for fisheries management scenarios across the Great Lakes region. We observed that preferences for native fish populations, invasive species impacts, wash station availability, habitat quality, and added cost per fishing trip were rooted in nature-based (i.e., biospheric) and self-driven (i.e., egoistic) values. Feelings of moral obligation and beliefs that an individual could make a difference were correlated with values, but not with preferences. Willingness to pay for a preferred future differed by fishing mode, in that boaters were more sensitive to cost than shoreline or mixed-mode users. Preferences also varied by age, in that younger anglers were more open to change. This study showcases an interdisciplinary methodological approach that builds more complete knowledge of the interrelationships between psychological and institutional factors that underpin angler decision-making.

Multiple introduction pathways of non-native Phoxinus minnows (Teleostei: Leuciscidae) in Corsica revealed by its hidden diversity and their parasites

The introduction of freshwater fish species is a leading cause of aquatic biodiversity erosion and can spread parasites to native populations. Hidden diversity evidenced by recent taxonomic revisions can add further complexity to the issue by rendering biological assessment data incomplete. The Eurasian minnows Phoxinus are one such example of cryptic diversity, with several described species being invasive. Current non-native fish populations in the small Mediterranean island of Corsica (France) are the result of successive waves of introductions, including several Phoxinus species. This study aims at determining which Phoxinus species were introduced to Corsica using the cytochrome oxidase subunit I barcoding marker, reconstructing their introduction routes and examining their parasite communities. The study found four species in Corsica: Phoxinus phoxinus and Phoxinus csikii mainly in the northernmost studied drainage basin and Phoxinus dragarum and Phoxinus septimaniae in the Tavignano drainage basin. P. phoxinus and P. csikii were most likely introduced through a live bait wholesaler while P. dragarum and P. septimaniae were probably introduced by recreational anglers bringing their bait from continental France. The molecular study of their Gyrodactylus (Platyhelminthes: Monogenea) parasites with the ITS marker allowed us to hypothesize inter-drainage basin secondary introduction routes for P. phoxinus and P. dragarum. In several sampling sites, Phoxinus minnows had black spot disease caused by encysted metacercariae of Digenea, likely Posthodiplostomum cuticola. These parasites were also found on the brown trout Salmo trutta in a locality where this patrimonial species co-occurs with Phoxinus minnows. Barcoding should be used in fish communities monitoring to help to accurately identify cryptic species.