Occurrence Of Fish Research Articles

Distribution and Diversity of Coastal Fish in Fresh and Oligohaline Waters: An Example of the Largest Baltic Sea Estuary of the Neva River

ABSTRACTUnderstanding how low salinity gradients (0‰–5‰) influence fish life cycles is critical for clarifying principles of fish assemblage formation in estuarine ecosystems. This study is intended to provide a foundation for predicting changes in fish populations amidst ongoing surface salinity decreases in the Baltic Sea. In the Neva River Estuary, differences in fish diversity and distribution between fish assemblages in freshwater and oligohaline areas were assessed using beach seine and multi‐mesh gillnet surveys. The use of multiple sampling gears greatly enhanced understanding of fish distribution across salinity gradients. Fish assemblages were analysed depending on the different areas of the estuary, seasons of sampling, salinity and confounding environmental variables such as water temperature and depth. Salinity was the major influencing factor for the surf zone fish assemblages and a season of sampling was the main factor for coastal assemblages of larger fish studied with the gillnets. Fish assemblages in the surf zone exhibited significant but gradual changes in freshwater and marine‐estuarine fish occurrence and abundance along the critical oligohaline barrier ‘δ‐horohalinicum’ (0.5‰–1.9‰). Although freshwater species showed high occurrence and abundance throughout the estuary, their juveniles were less abundant in the oligohaline surf zone with salinity ≥ 2‰, where small‐size marine‐estuarine and euryhaline species predominated. Coastal multi‐mesh gillnet catches showed remarkable similarity between assemblages of larger fish in freshwater and oligohaline areas. Differences in species richness and diversity indices were not pronounced throughout the salinity gradient; the decline in freshwater species was offset by an increase in marine‐estuarine and euryhaline species.

Long-term variations in the diet composition of Atlantic wolffish, Anarhichas lupus marisalbi (Zoarcoidei: Anarhichadidae), in Kandalaksha Bay, White Sea

Understanding the diet variability of the White Sea wolffish, Anarhichas lupus marisalbi Barsukov, 1956, is essential for explaining its population dynamics and variations in its life cycle. This study examined the food spectrum of wolffish from the coastal waters of Chupa Inlet (Kandalaksha Bay, White Sea) and analyzed interannual and seasonal changes in the species composition of its diet. During the summer period, wolffish feeds on a variety of macrobenthic organisms in its feeding grounds, particularly molluscs, echinoderms, crustaceans, and ascidians. The diet was predominantly composed of bivalves and gastropods, with Buccinum undatum Linnaeus, 1758 and Serripes groenlandicus (Mohr, 1786) being the most important prey species. Statistical analysis of multi-year diet data from 2001 to 2023 revealed interannual variations in the frequency of occurrence of key food organisms in wolffish stomachs. The results showed that in the early 2000s, the role of epibenthic crustaceans Hyas araneus (Linnaeus, 1758) and Pagurus pubescens Krøyer, 1838 in the wolffish diet was significantly greater compared to other years of the study. The dietary importance of the bivalve S. groenlandicus increased gradually and statistically significantly during the observation period, while Buccinum undatum dominated the wolffish diet throughout the entire study period. Overall, three species (B. undatum, S. groenlandicus, and Mytilus edulis Linnaeus, 1758) accounted for a significant portion of the wolffish diet during 2001–2023. In some years, other mollusc species, as well as crustaceans and the ascidian Styela rustica Linnaeus, 1767, were also included in the group of important prey items. The feeding intensity of wolffish in Chupa Inlet showed interannual variability. Throughout the observation period, certain years were identified as having the greatest frequency of fish with empty stomachs. Female wolffish showed a seasonal pattern in the frequency of occurrence of individuals with empty stomachs: the highest occurrence of such fish was observed during the spawning period of wolffish, in late July to early August. No significant seasonal changes in the frequency of occurrence of individuals with empty stomachs were found in males.

A revised marine fossil record of the Mediterranean before and after the Messinian salinity crisis

Abstract. The Messinian salinity crisis and its precursor events have been the greatest environmental perturbation of the Mediterranean Sea to date, offering an opportunity to study the response of marine ecosystems to extreme hydrological change and a large-scale biological invasion. The restriction of the marine connection between the Mediterranean and the Atlantic Ocean resulted in stratification of the water column and high-amplitude variations in seawater temperature and salinity already from the early Messinian. Here, we present a unified and revised marine fossil record of the Mediterranean (https://doi.org/10.5281/zenodo.13358435, Agiadi et al., 2024) that covers the Tortonian stage, the pre-evaporitic Messinian stage, and the Zanclean stage and encompasses 23 032 occurrences of calcareous nannoplankton, dinoflagellates, foraminifera, corals, ostracods, bryozoans, echinoids, mollusks, fishes, and marine mammals. This record adheres to the FAIR principles, is updated in terms of taxonomy, and follows the currently accepted stratigraphic framework. Based on this record, knowledge gaps are identified, which are due to spatiotemporal inconsistencies in sampling effort and the distribution of sedimentary facies, as well as the inherent differences in the preservation potential between the groups. Additionally, sampling bias in old records may have distorted the record in favor of larger, more impressive taxa within groups. This record is now ready to be used to answer both geological and biological questions about the Mediterranean Sea and beyond and is amendable when new fossil data are brought to light.

Temporal Patterns of Fish Occurrence in the Colorado River, Grand Canyon in Response to Temperature, Largescale Drought, and Newly Exposed Habitat

ABSTRACTTwo large dams on the Colorado River, Glen Canyon and Hoover Dam, have profoundly altered the river within Grand Canyon. Owing to widespread drought and increased water usage throughout the Southwest, water levels in Lake Mead declined by over 40 m since 2000, exposing over 80 km of newly emerged riverine habitat in the western Grand Canyon that experiences higher water temperatures and increased turbidity relative to upstream portions of the Colorado River within the Grand Canyon. Our objective was to investigate how the probability of fish occurrence has changed within the Colorado River in Grand Canyon as abiotic conditions have shifted in relation to these altered environmental conditions. We used 22 years of long‐term fish monitoring data, from 2000 to 2022, on the mainstem of the Colorado River in the Grand Canyon to map the probability of occurrence based upon modeled water temperature for native and common nonnative salmonid species through space (river kilometer) and time in relation to declining water levels in Lake Mead. Our results suggest that native fish occurrence is strongly correlated with longitudinally increasing water temperature, while nonnative trout species were negatively correlated with increased water temperature downstream from the dam. Further, we found that nonnative trout species have experienced decreases in their probability of occurrence through time, while natives have experienced an increase in probability of occurrence. Information on distribution of fish prior to reservoir declines, and how the fish assemblage has shifted coincident with environmental changes, can help inform future management of native and nonnative fish in highly regulated river systems.

The contribution of fish to the diet of loggerhead sea turtles in the western Mediterranean revisited

Early juvenile loggerhead turtles (Caretta caretta) rely on gelatinous zooplankton, whereas individuals larger than 40 cm curved carapace length are adapted to crush hard-shelled invertebrates. Nevertheless, fish were reported to be the staple food of loggerhead turtles in the western Mediterranean 30 years ago. Here, the temporal consistency of such a fish-based diet of loggerhead turtles is assessed through gut content analysis and stable isotope analysis of samples from the Mediterranean coast of Spain spanning three decades. The gut contents of 134 juvenile loggerhead turtles (curved carapace length range: 27–71 cm) from three different periods (1991, 1999–2008 and 2010–2017) were analyzed, as well as a subsample of the same turtles (n = 10 in each period) for both bulk and compound-specific stable isotope ratios (CSIA-AA). Gut content analysis revealed a decline in the frequency of occurrence and numerical abundance of fish and an increasing contribution of gastropods and bivalves throughout time, although pelagic tunicates were always the most frequently observed prey. The δ15Nbulk of turtle bone also dropped throughout the study period, but the values of the stable isotope ratio of N in phenylalanine (δ15NPhe) indicated that 52.5% of that variability was due to a baseline shift over time. Accordingly, the trophic position estimated from CSIA-AA did not follow the decreasing pattern of δ15Nbulk, but fluctuated throughout time. The overall evidence indicates that fish consumption by loggerhead turtles in the study region declined through time, but the trophic position of loggerhead turtles did not change simultaneously. This is probably because low trophic prey such pelagic tunicates and filter-feeding bivalves and suspension-feeding gastropods were the bulk of the diet during the whole study period and fish played a minor role, even when their frequency of occurrence peaked. Past levels of high fish consumption might be due to high levels of fishery discards, currently declining because of the recent reduction of the fishing fleet.

Sulawesi stream fish communities depend on connectivity and habitat diversity.

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

Seasonal variability of microplastic contamination in marine fishes of the state of Gujarat, India.

Seasonal variation in microplastics abundance, occurrence, and distribution in pelagic and demersal fishes was observed in this study during December 2021 to November 2022. One hundred percent presence of microplastic in inedible (gut and gills) tissue, while 82% and 54% in edible tissue (muscle) of pelagic and demersal fishes respectively were seen. Post-monsoon period showed high prevalence of microplastics followed by monsoon and the least during pre-monsoon in both pelagic and demersal fishes. In pelagic fishes, the edible tissue had microplastics abundance of 1.56 to 13.34 numbers per 10g of tissue whereas inedible tissue had 3.36 to 16.67 numbers per 10g of tissue. In demersal fishes, the edible tissue had microplastics abundance of 1.04 to 5.26 numbers per 10g of tissue while it was 2.67 to 8.34 numbers per 10g of inedible tissue. There was significant variation in abundance of microplastic in edible and inedible tissue of all the fishes (Mann-Whitney test, p < 0.05). The most dominant microplastics size was 0.005-0.05mm followed by 0.05-0.5mm and the least of greater than 0.5mm in pelagic and demersal fishes respectively. Taking microplastic shape into consideration, the most dominant was fiber followed by fragment and the film in inedible tissue of all the fishes. The edible tissue of all the fishes had only fiber in them (100% occurrence). The dominance of blue color microplastics was observed followed by red, green, yellow, and orange at least in edible as well as inedible tissues of the fishes. More than 99% microplastics polymer observed in this study include polyethylene (PE), polypropylene (PP), and polystyrene (PS); only less than 1% was unidentified. This is the first study done on seasonal variation of microplastic in the marine fish population of Gujarat waters, Northeast Arabian Sea. The study highlights the nature of micro-pollutant in marine environments, emphasizing the need for comprehensive monitoring and management strategies.

Feeding habits of splendid alfonsino Beryx splendens in the vicinity of Kuroshio, the south of Japan

AbstractGut contents and nitrogen isotope ratio (δ15N) analyses were conducted on splendid alfonsino Beryx splendens collected in the vicinity of Kuroshio from May 2015 to November 2016 (n = 708) to identify their feeding habits in the Western North Pacific. Micronektonic fish, shrimp, and squid were the dominant prey species, with the Decapoda Acanthephyra quadrispinosa, Prehensilosergia prehensilis, Cephalopoda Enoploteuthis chunii, Chiroteuthis calyx, Teleostei Sigmops gracilis, and Gonostoma elongatum. These micronektons are common in the Kuroshio Current; thus, B. splendens is a possible opportunistic feeder. Gut content weight (GCW), occurrence (%O) of fish and squid, and δ15N were significantly increased with the fork length (FL) of B. splendens. Only the %O of shrimp does not show a significant relationship with the FL of B. splendens. These indicated the ontogenetic shift of dominant prey from shrimp to fish. Fattened specimens could also prey on a greater number of fish. The seasonality of GCW and %O values was high in spring and autumn and low in summer and winter. This seasonality indicated that the feeding habits of B. splendens are controlled by primary productivity in the surface layer and/or by maturity. When the Kuroshio flowed in the north of Hachijojima Island, the GCW was significantly increased, and some organisms, including C. calyx, G. elongatum, and S. gracilis, were preyed on more. While the offshore area of the Kuroshio has low productivity, B. splendens can actively prey in this area, indicating that it is an important feeding ground for this species.

Organophosphate esters and their metabolites in silver pomfret (Pampus argenteus) of the Vietnamese coastal areas: Spatial-temporal distribution and exposure risk

A large number of studies on organophosphate esters (tri-OPEs) in marine organisms have not assessed the simultaneous occurrence of tri-OPEs and their metabolites (di-OPEs) in these species. This research investigated the concentration and geographical distribution of 15 tri-OPEs and 7 di-OPEs in 172 samples of Pampus argenteus that were collected annually from 2021 to 2023 at three distinct locations along the Vietnamese coast. As a result, tri-OPEs and di-OPEs were detected in numerous fish samples, indicating their widespread spatial and temporal occurrence in marine fish and pointing out the importance of monitoring their levels. The tri-OPEs and di-OPEs ranged within 2.1–38.9 ng g−1 dry weight (dw) and 3.2–263.4 ng g−1 dw, respectively. The mean concentrations of tri-OPEs ranged from 0.4 (TIPrP) to 5.4 ng g−1 dw (TBOEP), with TBOEP and TEHP having the highest mean values. In addition, the profiles of tri-OPEs in fish exhibited a descending order: Σalkyl OPEs > ΣCl-alkyl OPEs > Σaryl OPEs. The di-OPEs, namely BEHP and DMP, had the highest mean levels, measuring 33.4 ng g−1 dw and 23.8 ng g−1 dw, respectively. Furthermore, there have been significant findings of strong positive correlations between di-OPEs and tri-OPE pairs (p < 0.05). It is worth noting that there is a noticeable difference in the composition of tri-OPEs between the North and other regions. Despite these findings, the presence of OPE-contaminated fish did not pose any health risks to Vietnam's coastal population.

Reconstructing historical fish occurrence and documenting human-mediated introductions in lakes using sedimentary DNA

The recovery of DNA preserved in the sediment of aquatic systems (sedDNA) has provided short-term and long-term data on biological groups (e.g., bacteria, phytoplankton, zooplankton, and fishes) and has advanced our understanding of how environmental changes have affected aquatic communities. Here, we demonstrate the use of fish sedDNA from lake sediment cores in reconstructing the history of fish occurrences in four lakes within the Oil Sands region in Alberta, Canada. A general fish and eight targeted qPCR-based eDNA assays for freshwater fish species (cisco, lake whitefish, northern pike, chain pickerel, burbot, rainbow trout, lake trout, and walleye) were rigorously designed and validated. Utilizing these assays, we detected sedDNA from several fish species in sediment cores spanning over a century, which aligned with conventional fish surveys and historical records of human-mediated introductions. The use of fish sedDNA provided greater temporal resolution into the historical fish faunal records, bridging the knowledge gap that spanned from 100- to 150-year-old data. The present study also allowed documentation of human-mediated introductions of fish populations to the examined lakes. These findings can be used to refine native freshwater fish ranges and clarify the influence of human-mediated introductions on fish diversity in lakes, providing essential baseline data for conservation management and environmental impact assessments.

Species communities can accurately predict the occurrence of an imperilled fish

Species distribution information is essential for conservation. However, sampling the full range of a species’ potential distribution is rarely feasible, necessitating the development of models to predict distributions, as well as relevant environmental and biotic drivers. We applied a novel approach to model the distribution of a species at risk in Canada, silver shiner (SS; Notropis photogenis) in tributaries of Lake Ontario using the fish community as a predictor of SS occurrence. Associative rule learning (ARL) identified simple species combinations that provided strong insight into SS distribution, which may be particularly useful for identifying new occupied locations, including making sampling decisions in real time. The species with the most positive or negative associations with SS identified by ARL were included in a random forests model, which predicted SS distribution with high accuracy in test data from the study tributary system and in a neighbouring system where SS is exceedingly rare. Predicting species distributions based on biotic associations presents opportunities for discovering new populations, identifying critical habitat, and evaluating the suitability of sites for re-introduction potential.

Biodiversity of Demersal Fish Communities in the Cosmonaut Sea Revealed by DNA Barcoding Analyses.

The Cosmonaut Sea is one of the least accessed regions in the Southern Ocean, and our knowledge about the fish biodiversity in the region is sparse. In this study, we provided a description of demersal fish diversity in the Cosmonaut Sea by analysing cytochrome oxidase I (COI) barcodes of 98 fish samples that were hauled by trawling during the 37th and 38th Chinese National Antarctic Research Expedition (CHINARE) cruises. Twenty-four species representing 19 genera and 11 families, namely, Artedidraconidae, Bathydraconidae, Bathylagidae, Channichthyidae, Liparidae, Macrouridae, Muraenolepididae, Myctophidae, Nototheniidae, Paralepididae and Zoarcidae, were discriminated and identified, which were largely identical to local fish occurrence records and the general pattern of demersal fish communities at high Antarctic shelf areas. The validity of a barcoding gap failed to be detected and confirmed across all species due to the indicative signals of two potential cryptic species. Nevertheless, DNA barcoding still demonstrated to be a very efficient and sound method for the discrimination and classification of Antarctic fishes. In the future, various sampling strategies that cover all geographic sections and depth strata of the Cosmonaut Sea are encouraged to enhance our understanding of local fish communities, within which DNA barcoding can play an important role in either molecular taxonomy or the establishment of a dedicated local reference database for eDNA metabarcoding analyses.

Repeatability of Hydroacoustic Results versus Uncertainty in Assessing Changes in Ecological Status Based on Fish: A Case Study of Lake Widryńskie (Poland)

Assessments of changes in the ecological state of aquatic ecosystems are always burdened with uncertainty, which results from environmental reasons and poor repeatability of measurement results of elements enabling the assessment. This study determines the uncertainty related to the elements of the assessment of the hydroacoustic structure of fish communities’ (1) vertical target strength distribution (TS) in two-meter layers of water and (2) changes in the area where fish were recorded (which was determined on the basis of maps of their distribution in 2 m deep water layers). The object of this study was a lake (depth: 27 m) in which at the end of June 2016 the O2 concentration was &lt;1.4 mg L−1 below 8 m depth, which resulted in the accumulation of fish to a depth of 6 m. Hydroacoustic acquisition was carried out along transects arranged in the east–west (WE), north–south (NS), and zigzag (ZZ) directions in three repetitions. It was shown that the empirical probability of obtaining statistically different results was 2/9 when (1) Kendall’s τ coefficient, used to determine the similarity of the TS distribution, was less than 0.7—moderate correlation—and (2) fish occurrence areas in two cases (WE and ZZ on the third day of research) in layers 2–4 m and 4–6 m differed statistically significantly from the average area for all repetitions by 10–14% and 56–66% (p &lt; 0.05), respectively. The obtained results indicate quite good repeatability of acoustic measurements; however, in order to reduce the uncertainty, it is recommended that tests be conducted in this type of lake in three series of measurements.

Water mass exchange in triangle seas of the Java-Makassar-Flores (JMF): A modeling study

The ocean dynamics of the marginal seas in the Java-Makassar-Flores (JMF) Triangle seas facilitates the seasonal exchange of water masses between Java, Makassar, and Flores, which influences the occurrence of small pelagic fish. This research investigates seasonal fluctuations in sea currents, seawater temperature, salinity, and phytoplankton primary production (PPN and PPD) based on validated model output datasets from NEMO and PISCES from the INDESO simulation (2008–2015). The model demonstrated seasonal exchanges of the top 50 m of water masses in the area, where the eastward monsoon current transported freshwater (salinity<31 psμ) from the Java Sea to southern Makassar and Flores. This northwest monsoon produced a much fresher water in the southern region of Makassar and western region of Flores. During the southeast monsoon, the surface component of the Makassar throughflow, which transports saline water (salinity >34 PSU) into the Java Sea, pushes fresh Java waters westward. Seasonal salinity changes and PPN/PPD in the shelf region of southern Kalimantan correlated with substantial small pelagic fishing.

Recent Declining Trends in Pelagic Fish Catches in the Indian Ocean off Sri Lanka: Is Gill Oxygen Limitation Theory (GOLT) a Possible Explanation?

Recent trends in the pelagic fish landings of multi-day fishing fleets operated from Sri Lanka indicated significant declines in many fish species. Therefore, the present preliminary analysis investigates the perceptions of fishers on recent declining trends of pelagic fish landings from offshore areas of the Indian Ocean and further investigates whether the most common pelagic species landed in Sri Lanka conform to the gill oxygen limitation theory (GOLT) and to speculate GOLT as a possible explanation to such trends. According to the perceptions of 457 skippers of fishing vessels interviewed, such declines were possibly attributed to shifting of the areas of occurrence of pelagic fish species, making them less vulnerable to multi-day fishing vessels. As climate change and deoxygenation are major stressors affecting fish stocks, there is a challenging need for disentangling the impacts of these stressors from the effects of overfishing. The 18 most common pelagic fish species harvested from the Indian Ocean confirmed to the predictions from the GOLT, suggesting that shifting of these stocks could be due to deoxygenation which may have been triggered by increased sea surface and sub-surface temperatures. Therefore, fishery-independent surveys are needed to investigate the shifting of areas of occurrence of pelagic fishes in the Indian Ocean to understand their areas of occurrence the further investigate the relevance of GOLT for defining regional fisheries management plans.

The coastal ichthyofauna of the Mediterranean coral reef: the case of Mljet National Park (Croatia, southern Adriatic Sea)

The authors studied the structure of the coastal fish assemblage in a temperate coral reef within a marine protected area in order to provide a baseline information on the occurrence and temporal distribution of fish and to highlight the importance of the coral reef to ichthyofauna. The coastal fish assemblage was investigated at two sites in Veliko jezero (Mljet National Park) in the southern Adriatic Sea with a non-destructive SCUBA visual technique in the period from 2013 to 2021. Altogether, 38 fish taxa were recorded on the right bank (coral reef) and 36 species on the left bank. The presence of the coral reef at a depth range between 9 m to 12 m is the main factor differentiating the fish fauna in these two areas, which are otherwise governed by the same environmental factors. At the coral reef a decrease in fish diversity was discovered with a steady regression from 2013 to 2021.

Tropical seamounts as stepping-stones for coral reef fishes: range extensions and new regional distributions from mesophotic ecosystems in the Coral Sea, Australia

Seamounts and remote oceanic islands serve as valuable natural laboratories in which to study patterns and processes in marine biodiversity. A central hypothesis arising from studies of these systems is the ecological function of seamounts as stepping-stones for dispersal and population connectivity. Evidence of this mechanism exists for a range of taxa, including coral reef fishes, but is still lacking from many tropical seamounts in remote regions. In this study, we used remotely operated vehicles and baited remote underwater video systems to survey fish and benthic communities between 1 and 100 m on seamounts in the Coral Sea Marine Park (CSMP), Australia. We found evidence to support the stepping-stone model of ecological connectivity from new observations of 16 coral reef fishes which have previously not been recorded by quantitative surveys in the region. The widespread distribution of many of these species throughout the full latitudinal extent of the CSMP suggests that there is greater connectivity between mesophotic habitats in the Coral Sea and surrounding biogeographic regions than previously known. We also found a wide variety of mesophotic habitats and recorded significant depth range extensions for 78 fishes in these habitats. This further highlights the potential role of increased habitat area and heterogeneity in a stepping-stone effect throughout the region. Four of the fish occurrence records represent significant range extensions into the Coral Sea from adjacent biogeographic regions, and 13 fishes recorded by this study in the CSMP are not known from the neighbouring Great Barrier Reef, despite its close proximity. Although the Coral Sea remains relatively understudied, these findings suggest that larger-scale models of marine biogeography are relevant to communities in the region, particularly at mesophotic depths. Given the extent and the spatial arrangement of seamounts in the Coral Sea, our findings emphasise that the region is an important link between the centre of marine biodiversity in the Coral Triangle and the Southwest Pacific. Greater mesophotic sampling effort and genetic studies are necessary to understand the nature of connectivity and to establish the role of regional seamount chains, like the Coral Sea reefs, in broader marine biogeographic processes.

Assessing the relative impacts of habitat size, hydrology, and fish occurrence on aquatic invertebrate assemblages in a set of depressional wetlands of Georgia, USA

Assessing the relative impacts of habitat size, hydrology, and fish occurrence on aquatic invertebrate assemblages in a set of depressional wetlands of Georgia, USA

Microplastic(MP) occurrence in pelagic and demersal fishes of Gujarat, northwest coast of India.

Microplastics (MPs) are globally observed in marine as well as freshwater habitats, and laboratory studies have shown that marine organisms can accidentally ingest them. Monitoring the MP ingestion by fish in the environment is very crucial for understanding the risk of consuming MP-contaminated fish for human health. In this study, we investigated MP ingestion in 400 fish individuals from the Veraval Coast, in the state of Gujarat, India. There was 100% MP occurrence in the inedible tissues of fish, and 68% of the analyzed fishes presented MPs in edible tissues. The most dominant MPs based on their size in fishes were 0.05-0.1 mm. One hundred percent presence of only fibres in edible tissue was observed, while in inedible tissue, it was 77%, 20.42% and 2.58% of fibre, fragment and film respectively. The most common MP colour was blue. The predominant polymers were low-density polyethylene (LDPE) followed by polypropylene, high-density polyethylene (HDPE) and polystyrene. This is the first study performed on MPs in marine fishes from this region. Our findings suggest that the abundance of MPs observed in this area is higher than in other states of the country.

Occurrence of larval fishes sampled by drifting light traps in the lower reaches of a South African estuary.

The tidal occurrence of larval fishes was investigated in the permanently open Kowie Estuary on the warm-temperate coast of South Africa. Larval fishes were sampled in the mouth region using two drifting light traps deployed on the ebb and flood tides every second night for two consecutive 14-day periods, coinciding with the dark moon phase. A total of 553 larval fishes were caught, representing nine families and 26 species, of which Blenniidae and Clupeidae dominated. The prevalence of different estuarine association fish guilds was also tide-specific. Marine and estuarine species, such as Omobranchus woodi, were more dominant during flood tides, while marine straggler species, such as Sardinops sagax, which are not dependent on estuaries, were dominant on the ebb tide. Marine estuarine-dependents were only present during flood tides, potentially indicating ingress and entrainment within the estuary. The results confirm that light trap catches yield a different composition of species compared to towed ichthyoplankton net studies. Additionally, drifting light traps allow for better targeting of species with a phototactic response and reduction of incidental catch. Consequently, a mixture of gear is encouraged for more comprehensive surveys of larval fish occurrence.