Fish Families Research Articles

EXPLORING THE LINK BETWEEN WATER CHEMISTRY VARIATION AND FISH DIVERSITY IN RIVER JHELUM: A META-ANALYSIS

This study aimed to establish a connection between changes in the water chemistry of the river Jhelum and the diversity, richness, and abundance of species over time. Empirical evidence was reviewed from existing literature on fish species diversity and physicochemical parameters. A comparison was made between the upper and lower sections of the river, considering both spatial and temporal aspects. The dominant fish family in the river was Cyprinidae, consisting of eight species, followed by Nemachilidae, with only two species. Regarding diversity indices, the upper stretch exhibited values of 2.192 for the Shannon-Wiener diversity index (H'), 0.104 for Simpson's dominance index (D), 0.896 for the heterogeneity index (1-D), 1.436 for Margalef's index (d), and 0.350 for Pielou's evenness index (J'). Conversely, the lower stretch showed values of 1.978, 0.145, 0.855, 1.144, and 0.323, respectively. These findings indicated a decline in fish species diversity, richness, and relative abundance in the lower section. These results align with existing literature, suggesting that water pollution is more severe in the lower stretch compared to the upper stretch. However, correlation analysis revealed that, except for dissolved oxygen and ortho phosphorous, there is a negative relationship between water quality parameters and fish diversity, which, while present, is not significant enough to impact the river's fish diversity substantially. This suggests that other anthropogenic activities, such as sand mining, overfishing, and exotic common carp in the river, are responsible for the decreased fish diversity downstream in the river Jhelum. Further research is needed to investigate the effects of other hydrological parameters, such as precipitation, evapotranspiration, surface runoff, water velocity, and depth, on the fish diversity of the river Jhelum. Such studies would provide additional empirical evidence for protecting the aquatic fish biodiversity in the river Jhelum.

Testing Phylogenetic Placement Accuracy of DNA Barcode Sequences on a Fish Backbone Tree: Implications of Backbone Tree Completeness and Species Representation.

Advancements in DNA sequencing technology have facilitated the generation of a vast number of DNA sequences, posing opportunities and challenges for constructing large phylogenetic trees. DNA barcode sequences, particularly COI, represent extensive orthologous sequences suitable for phylogenetic analysis. Phylogenetic placement analysis offers a promising method to integrate COI data into tree-building efforts, yet the impacts of backbone tree completeness and species composition remain under-explored. Using a dataset comprising 27 genes and 4520 species of bony fishes, we assessed the accuracy of phylogenetic inference by "placing" COI sequences onto backbone trees. The backbone tree completeness was varied by subsampling 20%, 40%, 60%, 80%, and 99% of the total species separately, followed by placement of those missing species based on their COI sequences using software packages EPA-ng and APPLES. We also compared the effects of biased, random, and stratified sampling strategies; the latter ensured the representation of all major lineages (Family) of bony fish. Our findings indicate that the placement accuracy is consistently high across all levels of backbone tree completeness, where 70%-78% missing species are correctly placed (by EPA-ng) in the same locations as the reference tree derived from the complete data. High completeness produces slightly high placement accuracy, although in many cases the differences are nonsignificant. For example, at the 99% completeness level with stratified sampling, EPA-ng placed 78% missing species correctly, and when only considering placement with high confidence (LWR > 0.9), the percentage is 87%. Additionally, stratified sampling outperforms random sampling in most cases, and biased sampling has the worst performance. The likelihood-based EPA-ng consistently provide higher accurate placements than the distance-based APPLES. In conclusion, COI-based placement analysis represents a potential route of using the available vast barcoding data for building large phylogenetic trees.

The Influence of Economic Pressure, Social Capital, and Coping Strategies on Fishers's Family Well-being

Fish families are vulnerable to poverty. The vulnerability of fishermen’s families leads to economic pressure that can reduce family well-being. This study aimed to analyze the influence of economic pressure, social capital, and coping strategies on the well-being of fishers. This cross-sectional study was conducted in the Aru Islands Regency, Maluku Province, Japan. The sample consisted of 50 skipper fisher families and 50 laborer families. Sampling was performed using snowball sampling. The data were processed using descriptive tests, independent sample t-tests, and structural equation modeling (SEM) tests. This research revealed that labor fisher families' economic pressures were higher than those of skipper fisher families. The social capital of skippers and laborers was classified as a low category. The coping strategies of the skipper and laborer fisher families were classified as in the moderate category. The well-being of skipper fisher families was higher than that of labor-fisher families. Economic pressure has a direct negative influence on fishers’ well-being. Social capital has a direct negative influence on fishers’ well-being. The research implication is that the well-being of a fisher's family can be increased by increasing social capital.

Density and diversity of larval fish in some coastal bays in Sharm El-Sheikh, northern Red Sea, Egypt

This study was carried out to investigate the composition and the spatial and temporal distribution of coral reef fish larvae in Port Bay, Sharm El- Maya Bay and Naama bay located in Sharm El-Sheikh area on the Egyptian Red Sea coast. Ichthyoplankton samples were collected monthly for one year mostly in the morning just before and at sunrise. A net of 100 cm, and 0.5 mm mesh size was towed horizontally parallel to the reef for 5–10 min. Throughout the period of study, a total of 205 plankton samples resulted in a collection of 3678 larvae representing 46 taxa and 32 fish families. Although larvae occurred all the year round, the general pattern showed two peaks in summer and winter with their maximum density in August with 1030 individuals/1000 m3. The lowest density of fish larvae was observed in September with 12 individuals/1000 m3. Regarding the distribution in bays, Port Bay (PRT) recorded the highest larval density where 1476 individuals/1000 m3 were collected. On the other hand, the lowest density was recorded in Sharm El-Maya Bay (SMB) with an average density of 908 larvae/1000 m3. The highest density of fish larvae occurred in any sample was recorded in Naama bay in August with a density of 1824 individuals/1000 m3. In several cases the spawning seasons of these taxa as determined from the present work based on the seasonal occurrence of larvae coincides mostly with that obtained from the literature based on the reproductive biological studies. Results obtained during this work reflected the importance of fish eggs and larvae survey in the management and conservation of reef fish in the Red Sea.

Male mating tactics are associated with distinct female cognitive-behavioral profiles in 4 poeciliids

Abstract Male mating tactics, the morphological and behavioral traits that males employ to access potential mates, alter female space use, time budget, and ecology in ways that may have downstream consequences for female behavior and cognition. Courtship tactics, in which males display and females exercise preferences, are common in some taxa. In others, coercive tactics, in which males force matings with limited female choice, predominate. Because behavior and cognition often transcend a single context, we ask whether variation in male mating tactics predictably shapes female behavior and cognition outside of mating. Controlling for predation by using populations housed in ecologically identical mesocosms for multiple generations, we compared female behavioral and cognitive traits of 4 different species across the teleost fish family Poeciliidae. We compared all-coercive Gambusia vittata and Heterandria formosa to Limia perugiae and Xiphophorus nigrensis, species with both coercion and courtship. We assessed females on sociability, activity, boldness, stress movement, cognitive flexibility, and spatial learning. Mating system predicted variation in movement patterns, cognitive flexibility, and spatial learning. Mixed-tactic species showed higher activity, stress movement, and cognitive flexibility than coercion-only taxa. In spatial learning, the all-coercive G. vittata had the highest accuracy and was the only species to show evidence for learning across trials. Multivariate approaches identified movement traits as the largest factors differing between mating systems in cognitive-behavioral syndromes. This work provides the first suggestion that species-level variation in poeciliid male mating tactics is a potential factor contributing to differences in female behavior, cognition, and cognitive-behavioral syndromes.

Weak integration allows novel fin shapes and spurs locomotor diversity in reef fishes.

In complex functional systems composed of many traits, selection for specialized function can induce trait evolution by acting directly on individual components within the system, or indirectly through networks of trait integration. However, strong integration can also hinder diversification into regions of trait space that are not aligned with axes of covariation among traits. As a result, non-independence among traits may limit capacity for functional expansion. We explore this dynamic in the evolution of fin shapes in 106 species from 38 families of coral reef fishes, a polyphyletic assemblage that shows exceptional diversity in locomotor function. Despite strong shared developmental pathways and expectations of a strong match between form and function, we find that species that share swimming mode show substantial disparity in fin shape, and preferred swimming mode is a poor predictor of fin shape. The evolution of fin shape is weakly integrated across the four functionally dominant fins in swimming (the pectoral, caudal, dorsal, and anal fins) and integration is weakened as derived swimming modes evolve. The weak integration among fins in the ancestral locomotor condition provides a primary axis of diversification while allowing for substantial off-axis diversification via independent trait responses to selection. However, the evolution of novel locomotor modes coincides with a loss of integrated axes of covariation among fins. Our study highlights the need for additional work on the functional consequences of fin shape in fishes and impact of evolutionary integration on functions other than locomotion.

Phylogeography of Microphis retzii (Bleeker, 1856) and Microphis brachyurus (Bleeker, 1854) in the Pacific.

Syngnathidae are a charismatic family of teleost fishes, represented by seahorses, seadragons, and pipefishes. Syngnathidae are mainly composed of marine species, but about 30 species of pipefishes inhabit freshwater insular environments of the Indo-Pacific realm. Recent research has shown that some freshwater pipefish species are amphidromous and exhibit high intraspecific divergences across their distribution range, like Microphis brachyurus (Bleeker, 1854) distributed from Sri Lanka to French Polynesia and Microphis retzii (Bleeker, 1856) distributed from Taiwan to Indonesia. In this study, we used the mitochondrial cytochrome oxidase I (COI) partial gene of 91 specimens of M. brachyurus and 30 specimens of M. retzii from localities representative of their respective distribution area to improve knowledge on the population structure of these two widespread species. Genetic species delimitation and phylogeographic analyses were combined to explore spatial patterns of genetic diversity across the distribution ranges of the two species. We have highlighted deep genetic structuring within the two species and relate these results to various biotic and abiotic factors. For M. brachyurus, the population in Polynesia is distinct from those in the West Pacific, suggesting its distinctiveness and recognition as an evolutionary significant unit (ESU). For M. retzii, three lineages are delimited in its range distribution, suggesting the existence of two distinct species in Southeast Asia (Bali/Java/Lombok and China/Taiwan). Pipefish species are particularly vulnerable to anthropogenic pressures (inherent to Syngnathidae and insular environments). The present results, revising species delimitation and geographic distribution, will help implement effective conservation and management measures.

Submissions of diagnostic samples of two critically endangered species of handfish (Branchionichthys hirsutus and Thymichthys politus) from a public aquarium from 2018 to 2024.

Handfish (Family Brachionichthyidae) is the most threatened marine teleost fish family, however, there is little information on handfish health. We reviewed the results of submissions of mortalities from captive and captive bred spotted handfish (Branchionichthys hirsutus (Lacepède, 1804)) and red handfish (Thymichthys politus (Richardson, 1844)) from a public aquarium from January 2018 to February 2024. Seventeen cases for spotted handfish (comprising 33 individuals) and five cases for red handfish (one individual each) were submitted for mortality investigation. In 2018-2019, six of seven cases were diagnosed with scuticociliatosis. Other conditions included epitheliocystis (1 of 17), infections with metazoan parasites (2 of 17 for spotted handfish and 2 of 5 for red handfish) and hepatic lipidosis (4 of 17). Most submissions were fixed samples for histology with only one fish suitable for microbiology. We recommend development of a coordinated health program for all captive breeders and aquaria, which should include sampling protocols, collection, and preservation in a range of fixatives of all the dying or dead handfish and adapting sublethal sampling, including tank water to assess presence of pathogens and other microorganisms. Risk factors for handfish health in captivity should be assessed. Handfish health database should be established to avoid loss of corporate knowledge in this area.

Genetic and phenotypic validation of whole body fat content measured across production phases of Atlantic salmon using dielectric and near infrared Interactance spectroscopy

Accurate and repeated whole-body fat (WBF) measurements across production phases are important for optimizing feed utilization, reducing production waste, safeguarding fish health, ensuring product quality and improving overall salmon production. However, the chemical extraction (reference) methods for WBF recording, although precise and accurate, are costly, destructive and have limited applicability for repeated measurements on live fish. This study validates two digital phenotyping technologies: Dielectric spectroscopy (DS) and Near-infrared spectroscopy (NIR) against the reference Soxhlet chemical extraction method. DS is a fast and non-destructive commercial fat meter, whereas the specially designed NIR interactance allows deep penetration (up to 10 mm) through the fish skin into the body. Approximately 2800 fish belonging to 35 full sibs fish families were recorded for WBF at mean body weight (BW) of ∼110, 300 and 750 g in parr, pre-smolt and post-smolt phases, respectively. The WBF percentage changed across the studied production phases: with parr having a mean of 11.3 % and coefficient of variation (CV = 11 %), pre-smolt decreasing slightly in both mean 10.9 – 11.1 % and CV (5.5 – 8.8 %) and post-smolt with an increase to 14.9 % and CV (8.5 %). Both methods performed well relative to the reference, with NIR (R2 = 0.77 – 0.91) slightly outperforming the DS (R2 = 0.61 – 0.71). Significantly high genetic estimates for NIR (h2 = 0.57 ± 0.04 – 0.62 ± 0.06) and DS (h2 = 0.38 ± 0.07 – 0.56 ± 0.10) signify the potential use of these digital technologies for improving WBF in future selective breeding. The low genetic correlations (rg = 0.22 ± 0.13 – 0.33 ± 0.14) across fresh and seawater phases raise questions about the generalizability of metabolic, lipid and feed efficiency research conducted in parr and pre-smolt phases in freshwater, to the post-smolt stage in seawater. The study highlighted the unexplored detail of the genetic regulation of WBF as fish undergoes production phases. Overall, these results will add to our understanding of genetic architecture for WBF and pave the way for digital phenotyping technologies to record complex but economically important traits and refine breeding strategies.

Reference genome for the endangered, genetically subdivided, northern tidewater goby, Eucyclogobius newberryi.

The federally endangered sister species, Eucyclogobius newberryi (northern tidewater goby) and E. kristinae (southern tidewater goby) comprise the California endemic genus Eucyclogobius, which historically occurred in all coastal California counties. Isolated lagoons that only intermittently connect to the sea are their primary habitat. Reproduction occurs during lagoon closure, minimizing marine dispersal and generating the most genetically subdivided vertebrate genus on the California coast. We present a new genome assembly for E. newberryi using HiFi long reads and Hi-C chromatin-proximity sequencing. The 980Mb E. newberryi reference genome has an N50 of 34Mb with 22 well-described scaffolds comprising 88% of the genome and a complete BUSCO score of 96.7%. This genome will facilitate studies addressing selection, drift, and metapopulation genetics in subdivided populations, as well as the persistence of the critically endangered E. kristinae, where reintroduction will be an essential element of conservation actions for recovery. It also provides tools critical to the recovery of the genetically distinct management units in the northern tidewater goby, as well as broader ecological and evolutionary studies of gobies, the most speciose family of fishes in the world.

Diel movement patterns in nominally nocturnal coral reef fishes (Haemulidae and Lutjanidae): Intra vs. Interspecific variation

Movement of animals, habitat connectivity, and nutrient transport are key elements in the ecological functioning of coral reef ecosystems. However, most studies have focused on the diurnal component of these aspects; nocturnal patterns are less known. Our study aims to address this knowledge gap by assessing diel movement patterns in ecologically and commercially important nocturnal coral reef fishes. We evaluate 122-days of acoustic telemetry data from 4 nocturnal species in 2 coral reef fish families (Haemulidae and Lutjanidae) on the Great Barrier Reef. For all species, we found a clear division between daytime resting areas on the reef and a move towards off-reef areas at night. This was highlighted in the low number of detections at night and the high average transitions between receivers at twilight. Over our study period, average nocturnal space use area (minimum convex polygon) of Plectorhincus gibbosus was 328,089 m2, Plectorhincus lineatus 28,828 m2, and Lutjanus carponotatus 20,369 m2. However, results from a Principal Component Analysis revealed that space use, and movement, varied substantially within species; for 3 of the 4 species the main axis of variation correlated with individual-level behaviour. These large differences in individual space use patterns highlight the need for caution when using species averages when considering ecosystem functions. Overall, our preliminary observations provide a glimpse into the large spatial extent, potential habitat connectivity, and intra and interspecific variation in activity patterns among large nocturnal Indo-Pacific reef fishes. This highlights their potential importance in maintaining ecosystem links between coral reefs and adjacent habitats.

Biological Characteristics of the Glacier Lantern Fish Benthosema glaciale (Myctophidae) in Icelandic Waters andthe Irminger Sea During Summer.

Myctophids are one of the most diverse and abundant fish families in the mesopelagic zone, making them a key component in the marine pelagic community. In the North Atlantic, Benthosema glaciale (glacier lantern fish) is considered the most abundant myctophid north of 35° N, yet some regions within its extensive range lack information on its basic biological parameters. We investigated the growth and described the distribution of B. glaciale in Icelandic waters, including the southern continental shelf, Iceland Basin, and Irminger Sea. Length distribution, growth, relative body condition, age, and otolith-fish size relationships were analyzed from samples collected opportunistically with pelagic trawls during the International Ecosystem Summer Survey in the Nordic Seas (IESSNS) in July 2020. In total, 1374 individuals were caught, and only a subset of 225 were measured fresh at sea and 89 were frozen and dissected on land. Total lengths of fresh fish ranged from 38 to 85 mm, while dissected individuals ranged from 40 to 74 mm and were 2 to 6 years old. Located over the Reykjanes Ridge in the Iceland Basin region, individuals had a significantly higher mean standard length and mean age, and a lower mean body condition. We reported length-weight relationships for both fresh and frozen samples, indicating evidence that preserving of the specimens through freezing affected relationships. The von Bertalanffy growth curve was calculated along with significant otolith-fish size relationships where r 2 values ranged between 0.87 and 0.92. Our research highlights the importance of cross-regional studies and provides baseline biology for B. glaciale in Icelandic waters, specifically in the southern continental slope and Reykjanes Ridge.

Parasites Infestations Status in Fish Species from River Orogodo, a Freshwater Municipal Stream, Southern Nigeria

Parasites are ubiquitous and fish are host to some of these parasites that can be zoonotic. Assessing their status and trends is vital in public health safety, and aquatic ecology. The study aimed to identify parasites, assess the prevalence, identify the infection sites and also determine the variation in infection among sexes in fish from River Orogodo, Agbor, Delta State. A total of 780 fish, comprising 23 species belonging to 12 fish families were collected between September 2014 and August 2019 using cast nets of various mesh sizes and funnel entrance traps. Fishes were identified and examined using standard morphological keys. According to established procedures, parasitological indexes were determined by inspecting various external and internal body parts. The overall prevalence recovered was 196 (25.1%) with twenty-two parasites including larvae stages both from external and internal parts of the fish. These include 5 protozoans (Microsporidium gen sp, Trichodina spp, Epistylis sp, Crytobia sp and Chilodonella sp), Myxobolus sp, 5 nematodes (Procamallanus laevionchus, Camallanus sp, Cucullanus sp, contracaecum larvae, Rhabdochona sp); 3 acanthocephalans (Acanthogyrus sp, Neoerchinorhynchus sp and Acanthocephalus sp), 4 cestodes (Monobothroides woodlandi, Wenyonia sp, Proteocephalid sp including plerocercoid larvae); 3 digeneans (Clinostomum sp, Euclinostomum heterostomum, Centrocestus sp, unidentified metacerceriae in the liver). The study revealed that female fish (32.5%) were more infected than their male counterparts (26.4%). The results indicate that fishes in River Orogodo, Delta State are hosts of various external and internal parasites, which may be of public health and aquacultural importance.

Influence of increasing noise at the offshore wind farm area on fish vocalization phenology: A long-term marine acoustical monitoring off the foremost offshore wind farm in Taiwan

The rapid increase of offshore projects at Taiwan Strait in recent decade has been debated for elevated noise levels. However, there are no studies on long-term assessment of noise levels and impact of noise on marine organisms. The passive acoustic monitoring was conducted at the foremost wind farm area in Taiwan to assess the sound levels and the impact of noise on fish vocalization behavior. Predominately, in the soundscape around the Taiwan Strait, two chorusing types (Type 1 and Type 2) from the Sciaenid family of fishes exist. Ambient sound levels significantly increased from 2014 to 2019, while the chorusing Types 1 and 2 were observed in a lower percentage of the recordings. Additionally, chorusing peak intensity and duration significantly reduced over the years for both choruses. This is the first field-based evidence to demonstrate the consequences of increasing anthropogenic noise having the potential to alter the vocalization behavior of the fish.

Insight into the diet of early stages of mesopelagic fishes in the Indian Ocean using DNA metabarcoding

Despite playing a critical role in oligotrophic ocean food webs, relatively little is known about the diet of mesopelagic fishes in the Indian Ocean. These fishes are an abundant component of the micronekton assemblages and are a major energy- and nutrient-rich food source, linking the plankton which they feed on to marine predators at higher trophic levels. DNA metabarcoding, a molecular method to identify species from mixed assemblages, has not been commonly used in studies of mesopelagic fish diet, but using it to analyse gut contents can greatly improve the understanding of mesopelagic fish feeding ecology. In this study, we apply DNA metabarcoding (18S rRNA and COI) to gut contents from Stomiiformes and Myctophiformes species from 20 sampling stations covering 30° of latitude on the 110°E meridian in the Indian Ocean. In total, 174 fish specimens from 13 genera were examined. Differences in the gut contents among fish families, geographic areas and fish stages were identified. Specimens within the family Myctophidae had the most diverse diet, more so in the northern sampling stations than the south. Gonostomatidae had the least diverse diet. Overall, the most frequently identified prey items from the gut contents were calanoid copepods and halocyprid ostracods. The proportion of halocyprids were also identified to be significantly different among Myctophidae larvae and juvenile specimens, which is a potential ontogenic shift in diet towards a higher ostracod contribution in juveniles as mouth gape increases. In comparison with other plankton abundance data, Copepoda were the most abundant plankton in the gut contents of all fishes sampled throughout the latitudinal gradient, allowing them to be a potential food resource through the region. There are indications that other less abundant plankton, such as Ostracoda and Malacostraca, may be preferentially targeted by some mesopelagic fish families.

Structure of Reef Fish Families (Butterflyfishes and Angelfishes) at Isolated Oceanic Reefs in the Indian Ocean: Christmas Island and the Cocos (Keeling) Islands

There has been substantial research on the factors that structure reef fish assemblages, but this has mostly focused on nearshore or continental reefs. This study examines patterns of abundance and species composition for two iconic groups of coral reef fishes, angelfishes (family Pomacanthidae) and butterflyfishes (family Chaetodontidae) at two isolated, oceanic reefs in the Indian Ocean: Christmas Island and the Cocos (Keeling) Islands. Six explanatory variables were investigated to determine whether large-scale physical factors are more important than fine-scale biotic factors in structuring reef fish communities on oceanic islands. For angelfishes, depth was the factor that most explained patterns in abundance (explaining 46.5% of the variation), species richness (44.8%) and composition (15.3%), with both abundance and species richness being greater at 20 m than at 5 m. Differences in species composition were greater between depths than between islands. For butterflyfishes, variation in abundance and species richness was best explained by the difference in aspect or exposure among sites, though abundance and composition also differed significantly between Christmas Island and the Cocos (Keeling) Islands. Large-scale variation in the structure of these reef fish assemblages could not be explained based on differences in habitat diversity, or coral and algal cover. This study indicates that large-scale physical factors (island location, exposure, depth) are more important than fine-scale biotic factors in structuring reef fish assemblages on oceanic islands.

Habitat trumps biogeography in structuring coral reef fishes

As one of the world’s most diverse ecosystems, coral reefs have been the focus of numerous biogeographic analyses. With strong biodiversity gradients across the Indo-Pacific, coral reefs have shed light on the effects of evolutionary history, isolation, and human exploitation on local assemblages. However, there are also strong environmentally driven local gradients in faunal assemblages. We ask, does reef fish community composition and trait space vary to a greater extent across small scales (i.e. along habitat gradients) or across large scales (i.e. across geographic regions separated by up to 12,000 km)? Using a standardized survey method that explicitly includes habitats (i.e. the slope, crest, and flat), we surveyed a highly diverse family of reef fishes (Labridae) in nine regions across the Indo-Pacific, from the Cocos (Keeling) Islands to French Polynesia. We demonstrate that small-scale habitat gradients represent a greater axis of variation, in both the taxonomic and trait composition of fish assemblages, than large-scale biogeographic gradients. Indeed, fish assemblages just 10 m apart, along a habitat gradient, appear to differ more than assemblages in the same habitats separated by over 12,000 km along the world’s largest biodiversity gradient. Essentially, fish assemblages cluster by habitat regardless of their biogeographic region, with habitat associations trumping biogeographic affiliations. This emphasizes the primacy of local environmental factors, such as hydrodynamics, in shaping the ecology of reef fishes. It also raises serious concerns over the use of combined datasets, where data from different habitats are used, without explicit recognition, in global-scale analyses.

Variations in the Abundance, Biodiversity, and Assemblage Structure of Larval Fish in the Restricted Waters of the Wang-an Light Fishery off Penghu, Taiwan

This study examined the abundance, biodiversity, and assemblage structure of larval fish inside and outside the restricted fishing zone of the Wang-an light fishery, which is located off Penghu, Taiwan. A total of 97 taxa belonging to 48 families of larval fish were identified through plankton tows conducted during the present investigation. Upeneus japonicus from the Mullidae family emerged as the dominant species in the surveyed area. Diurnal variation in larval fish abundance was evident, with higher abundance observed at night-time than during daytime. However, no significant difference was observed between the larval fish abundance inside and outside the restricted zone. Moreover, fish egg abundance and larval fish biodiversity did not exhibit notable differences between sampling locations or times. Cluster analysis revealed the presence of two groups of seasonal species. The major species in the spring group were Abudefduf vaigiensis and Pomacentrus coelestis, which prefer a low-temperature environment. The major species in the summer group was U. japonicus, which prefers a high-temperature environment. The seasonal succession of water masses under the influence of monsoon activity likely contributed to the observed grouping patterns of larval fish assemblages in the study area. These patterns were closely linked to the marine environmental conditions in this area. The study outcomes provide scientific insights and recommendations regarding the importance and benefits of establishing a restricted fishing zone for sustaining fishery resources.

The secret lives of wedgefish: first insights into fine-scale behaviour and movement ecology of a globally imperilled ray

Wedgefishes have recently been recognised as one of the most imperilled marine fish families worldwide. However, many knowledge gaps about their biology and ecology hinder conservation efforts. Here we used a combination of acoustic telemetry and acceleration datalogger technology to gain fundamental insights into the fine-scale behaviour, habitat use, size of activity spaces, and residency of adult female bottlenose wedgefish (Rhynchobatus australiae) in the Ningaloo region of northwestern Australia. Acoustic tracking data over one year demonstrated that female bottlenose wedgefish continuously resided in a relatively small area of a productive coral reef lagoon. Acceleration data revealed that bottlenose wedgefish were nocturnal, with time of day having a greater influence on activity than tidal patterns. Bottlenose wedgefish also increased activity with seasonally increasing temperatures. We identified several discrete behavioural signatures in the acceleration data, inferred to correspond to chafing, settling/burying behaviour, foraging behaviour, and escape behaviour, based on their kinematics. Further observations are required to confirm these behaviours with certainty. Additionally, according to datalogger and acoustic data, tagged bottlenose wedgefish rarely inhabited areas greater than 2 m deep. Together, these first insights into behaviour and habitat use of adult female bottlenose wedgefish highlight the importance of nearshore habitats for this species and indicate that they may be highly resident to specific areas. Our findings provide important insight into the conservation of bottlenose wedgefish in northwestern Australia, including potential effectiveness of protected areas and interactions with specific anthropogenic threats such as shoreline development and recreational beach fishing.

Variations in methylmercury contamination levels and associated health risks in different fish species across three coastal bays in China

The growing atmospheric mercury (Hg) emissions in China have raised ongoing concerns regarding contamination in marine fish. To better understand the pollution patterns and associated risks, we examined methylmercury (MeHg) content in demersal and pelagic fish from four commonly found families in three geographically distinct bays along the Chinese coast. We identified significant spatial variations in MeHg levels within the same fish family across regions. Specifically, fish collected from the Beibu Gulf in the South China Sea consistently exhibited significantly higher MeHg levels compared to those from the Laizhou Bay in the Northeast and/or Haizhou Bay in the East of China. In contrast, MeHg levels in fish collected from Haizhou Bay consistently remained the lowest. Within each region, we observed significantly higher MeHg concentrations in demersal species compared to pelagic species. This trend was particularly evident in fish species including bartail flathead (Platycephalus indicus), small-scale tongue sole (Cynoglossus microlepis) and greater lizardfish (Saurida tumbil) from the Beibu Gulf (0.50, 0.21, and 0.18 mg/kg dw, respectively), as well as bartail flathead and slender lizardfish (Saurida elongata) from Laizhou Bay (0.09 and 0.12 mg/kg dw, respectively). By comparison, MeHg content in silver pomfret (Pampus argenteus) from all three regions consistently remained relatively lower than in other species. Using target hazardous quotient (THQ) calculations, we estimated potential health risks in local populations associated with the consumption of the studied fish species. Our results showed a lack of apparent health risks to local residents, as all THQ values obtained from the three regions fell within the safe limits (0.02–0.94). However, it remains important to conduct additional assessments and spatiotemporal monitoring that encompass a broader range of species and regions.