Three decades of increasing fish biodiversity across the northeast Atlantic and the Arctic Ocean.

Observed range shifts of numerous species support predictions of climate change models that species will shift their distribution northward into the Arctic and sub-Arctic seas due to ocean warming. However, how this is affecting overall species richness is unclear. Here we analyze 20,670 scientific research trawls from the North Sea to the Arctic Ocean collected from 1994 to 2020, including 193 fish species. We found that demersal fish species richness at the local scale has doubled in some Arctic regions, including the Barents Sea, and increased at a lower rate at adjacent regions in the last three decades, followed by an increase in species richness and turnover at a regional scale. These changes in biodiversity correlated with an increase in sea bottom temperature. Within the study area, Arctic species' probability of occurrence generally declined over time. However, the increase in species from southern latitudes, together with an increase in some Arctic species, ultimately led to an enrichment of the Arctic and sub-Arctic marine fauna due to increasing water temperature consistent with climate change.

Microplastic-induced oxidative stress response in turbot and potential intake by humans.

Microplastic (MP) pollution has become a health concern subject in recent years. Althoughann increasing number of studies about the ingestion of microplastics by fish, research on the oxidative stress response to MPs in natural environments is quite limited. In this study, the identification and characterization of MPs in gill (G), muscle tissues (M), and gastrointestinal tract (GI) of turbot (Scophthalmus maximus) were evaluated. Oxidative damage of MPs on the brain (B), liver (L), gill (G), and muscle (M) tissues as well as their effect on superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), paraoxonase (PON), arylesterase (AR) myeloperoxidase (MPO), and malondialdehyde (MDA) biomarkers were evaluated. The potential transmission of MPs from muscle tissues to humans was examined. Results showed that gills contain the highest amounts of MPs, ethylene propylene is the most dominant polymer type, black and blue are the most common MP color, fiber is the most common shape, and 50-200 µm is the most common MP size. Results showed that MPs cause oxidative stress of tissues with inhibiting effect on enzyme activities and promoting impact on lipid peroxidation. The oxidative damage mostly affected the liver (detoxification organ) followed by gill tissue. The intake of MPS in the European Union was estimated by EFSA as 119 items/year, while in Turkey it is 47.88 items/year. This study shows that more research is needed in terms of ecosystem health and food chain safety. The risk assessment of MPs in living organisms and environmental matrices including food safety and human health should be considered a public health issue.

Are we ready to track climate-driven shifts in marine species across international boundaries? - A global survey of scientific bottom trawl data.

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio-temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate-driven ocean changes.

Microplastics in Tissues (Brain, Gill, Muscle and Gastrointestinal) of Mullus barbatus and Alosa immaculata.

The researches on MPs in commercial marine fish are very limited although in marine environments microplastic (MPs) pollution is a global problem. In this study, the presence, composition, and characterization of MPs in different tissues (brain, gill, muscle, and gastrointestinal tract) of commercial fish species [red mullet (Mullus barbatus) and pontic shad (Alosa immaculata Bennett 1835)] from the Black Sea were investigated. M. barbatus (demersal) and A. immaculata (pelagic) fish were preferred in the selection of fish species in order to represent demersal and pelagic environments. After dissected the fish, MPs were obtained from the tissues by extraction using the flotation method; then the MPs were counted and categorized according to shape, size, and color. The composition of the MPs was determined via ATR-FTIR spectroscopy. In terms of microplastic abundance in fish tissues, the gastrointestinal tract (40.0%) ranked first in both fish species, while the lowest MPs density was determined in brain tissues (7.0%). After the gastrointestinal tissue, gills were identified as the second tissue with the highest MPs density. Regardless of fish species, MPs characterization was mainly fibrous (51.0%), black colored (49.0%), and 50-200 µm in size (55.0%). Among the nine different polymers determined, polychloroprene (18.8%) and polyamide (15.0%) were found most frequently. This research provides data for tissue-based assessment of MPs in fish. The obtained data showed that MPs (one of the anthropogenic pollutants) are quite high in all tissues regardless of fish species. Moreover, it has emerged that these two fish species are suitable for monitoring microplastics in the study area.

Cryptic Speciation of a Deep-Sea Demersal Fish of the Genus Bothrocara in the Japan Sea.

Deep-sea demersal fishes of the Bothrocara hollandi species complex are distributed in the Japan Sea, the Okhotsk Sea, and the northwestern Pacific Ocean. Based on the nucleotide sequences of the nuclear Internal Transcribed Spacer 1 (ITS1) region and the microsatellite analysis, cryptic speciation resulting in the existence of two species (sp. 1 and sp. 2) in the Japan Sea was indicated for this species complex. In the Japan Sea off the San-in district, the westernmost part of the Japanese mainland, the frequency of sp. 2 individuals was highest at a depth of ∼400 m and decreased at both greater and lesser depths. Complete genetic deviation was observed between the individuals of the Japan Sea and the other sea areas, with the exception of a single sp. 2 individual, which shared an ITS1 sequence with an individual from the Pacific Ocean. Furthermore, a microsatellite analysis showed that the individuals of the other sea areas were more closely related to sp. 2 individuals. Two species were thought to have deviated from each other after their isolation from the individuals of the sea areas outside of the Japan Sea, through the occurrence of habitat fragmentation and bottleneck events in the Japan Sea during the glacial periods. Group A, one of two mitochondrial haplotype groups that were reported for the Japan Sea individuals in the previous studies, may have evolved within the lineages of sp. 2.

Comparison of Lindane and Carbaryl Pesticide Bioaccumulation in the Common Sole (Solea solea).

Organochlorines and carbamates are common pesticides predominantly employed in agriculture. Large amounts of pesticides make their way into rivers and marine habitats. They accumulate in aquatic organisms through different exposure routes and gradually move up the food chain. Since contaminant bioaccumulation in animals is affected by several factors, this work harnessed several different approaches to explore the persistence of lindane, a long banned organochlorine pesticide, and carbaryl, a newer generation pesticide, in common sole (Solea solea), a major commercial species in Adriatic fisheries. Lindane was not only more accumulated than carbaryl in sole liver, but it was also detected in greater amount in muscle tissue, the edible part (lindane, 7 ± 4 ng/g; carbaryl, <0.004 ng/g w/w). Additional assays documented a greater accumulation of lindane in adults compared with juveniles and in specimens caught offshore than in those collected close to the coast. The present findings demonstrate the different accumulation dynamics of the two pesticides to confirm the benefits derived from the replacement of organochlorine pesticides with carbamate compounds.

Using marine reserves to manage impact of bottom trawl fisheries requires consideration of benthic food-web interactions.

Marine protected areas (MPAs) are widely used to protect exploited fish species as well as to conserve marine habitats and their biodiversity. They have also become a popular management tool for bottom trawl fisheries, a common fishing technique on continental shelves worldwide. The effects of bottom trawling go far beyond the impact on target species, as trawls also affect other components of the benthic ecosystem and the seabed itself. This means that for bottom trawl fisheries, MPAs can potentially be used not only to conserve target species but also to reduce impact of these side effects of the fishery. However, predicting the protective effects of MPAs is complicated because the side effects of trawling potentially alter the food-web interactions between target and non-target species. These changes in predatory and competitive interactions among fish and benthic invertebrates may have important ramifications for MPAs as tools to manage or mitigate the effects of bottom trawling. Yet, in current theory regarding the functioning of MPAs in relation to bottom trawl fisheries, such predatory and competitive interactions between species are generally not taken into account. In this study, we discuss how food-web interactions that are potentially affected by bottom trawling may alter the effectiveness of MPAs to protect (1) biodiversity and marine habitats, (2) fish populations, (3) fisheries yield, and (4) trophic structure of the community. We make the case that in order to be applicable for bottom trawl fisheries, guidelines for the implementation of MPAs must consider their potential food-web effects, at the risk of failing management.

The Good, The Bad, and The Distant: Soundscape Cues for Larval Fish.

Coral reef noise is an important navigation cue for settling reef fish larvae and can thus potentially affect reef population dynamics. Recent evidence has shown that fish are able to discriminate between the soundscapes of different types of habitat (e.g., mangrove and reef). In this study, we investigated whether discernible acoustic differences were present between sites within the same coral reef system. Differences in sound intensity and transient content were found between sites, but site-dependent temporal variation was also present. We discuss the implications of these findings for settling fish larvae.

Spatial and temporal distribution patterns of the silver mojarra Eucinostomus argenteus (Perciformes: Gerreidae) in a tropical semi-enclosed bay.

This study determined the spatial and temporal distributions of the silver mojarra Eucinostomus argenteus (Perciformes: Gerreidae), one of the most abundant teleost species in bays and estuaries. Sampling was conducted from July 2005 to June 2007. The species was captured on all sampling dates and at six of the seven sampling stations. Approximately 80% of the individuals were below the size of first sexual maturity (12·0 cm total length, LT ). Although the spatial distribution of juveniles and adults differed throughout the study period, the environmental variables measured explained only a small part of their distribution. The recruitment period occurred during the first part of each year. Despite the high pollution levels in Guanabara Bay, this coastal system plays an important role as a nursery ground and for the growth of E. argenteus.

Quantifying alosine prey in the diets of marine piscivores in the Gulf of Maine.

The objectives of this work were to quantify the spatial and temporal distribution of the occurrence of anadromous fishes (alewife Alosa pseudoharengus, blueback herring Alosa aestivalis and American shad Alosa sapidissima) in the stomachs of demersal fishes in coastal waters of the north-west Atlantic Ocean. Results show that anadromous fishes were detectable and quantifiable in the diets of common marine piscivores for every season sampled. Even though anadromous fishes were not the most abundant prey, they accounted for c. 5-10% of the diet by mass for several marine piscivores. Statistical comparisons of these data with fish diet data from a broad-scale survey of the north-west Atlantic Ocean indicate that the frequency of this trophic interaction was significantly higher within spatially and temporally focused sampling areas of this study than in the broad-scale survey. Odds ratios of anadromous predation were as much as 460 times higher in the targeted sampling as compared with the broad-scale sampling. Analyses indicate that anadromous prey consumption was more concentrated in the near-coastal waters compared with consumption of a similar, but more widely distributed species, the Atlantic herring Clupea harengus. In the context of ecosystem-based fisheries management, the results suggest that even low-frequency feeding events may be locally important, and should be incorporated into ecosystem models.

Whole transcriptome analysis of demersal fish eggs reveals complex responses to ocean deoxygenation and acidification.

Ocean acidification and deoxygenation co-occur in marine environments, causing deterioration of marine ecosystems. However, effects of compound stresses on marine organisms and their physiological coping mechanisms are largely unknown. Here, we show how high pCO2 and low dissolved oxygen (DO) cause transcriptomic changes in eggs of a demersal fish (Sillago japonica), which are fully exposed to such stresses in natural environment. Overall gene expression was affected more strongly by low DO than by high pCO2. Enrichment analysis detected significant stress responses such as glycolytic processes in response to low DO. Increased expression of a group of glycolytic genes under low DO conditions is presumably because oxygen depletion disables the electron transfer pathway, complementing ATP production in the glycolytic pathway. Contrary to expectations, apparent mitigation of gene expression changes was dominant under combined stress conditions, and may represent an innate fish adaptive trait for severe environments.

Spatial Dynamics of Demersal Fish Assemblages off the Korean Coast in the East Sea.

This study assessed variations in demersal fish assemblages with respect to the study site and water depth. Seasonal samplings from May 2018 to March 2019 were conducted along the northern (Ayajin, Goseong) and southern (Hupo, Uljin) sites of the East Sea off the Korean coast, using commercial gill nets. Samples were collected at depths of ~50, ~80, ~150 m across the study sites, with concurrent monitoring of water column structures. A total of 73 species and 6250 specimens were collected. Distinctive fish species compositions were observed according to the study site and depth. Although Glyptocephalus stelleri was the most abundant fish species in both Ayajin and Hupo, Gadus macrocephalus, Icelus cataphractus, and Alcichthys elongatus were most predominant in Ayajin, whereas Cleisthenes pinetorum, Hippoglossoides dubius, and Gymnocanthus herzensteini were more prevalent in Hupo. In terms of depth layer, in Ayajin, G. stelleri dominated in both intermediate and deeper layers, with Hemilepidotus gilberti, A. elongatus, Enophrys diceraus common in shallower depths. Conversely, in Hupo, G. stelleri, C. pinetorum, and A. nadeshnyi dominated across all depth layers, whereas Dasycottus setiger and G. herzensteini dominated in deeper and shallower depths, respectively. Significant influences of the study site and water depth on fish assemblage structures were observed due to variations in water temperature at the seasonal thermocline boundary.

Over 20% of marine fishes shifting in the North and Barents Seas, but not in the Norwegian Sea.

Climate warming generally induces poleward range expansions and equatorward range contractions of species' environmental niches on a global scale. Here, we examined the direction and magnitude of species biomass centroid geographic shifts in relation to temperature and depth for 83 fish species in 9,522 standardised research trawls from the North Sea (1998-2020) to the Norwegian (2000-2020) and Barents Sea (2004-2020). We detected an overall significant northward shift of the marine fish community biomass in the North Sea, and individual species northward shifts in the Barents and North Seas, in 20% and 25% of the species' biomass centroids in each respective region. We did not detect overall community shifts in the Norwegian Sea, where two species (8%) shifted in each direction (northwards and southwards). Among 9 biological traits, species biogeographic assignation, preferred temperature, age at maturity and maximum depth were significant explanatory variables for species latitudinal shifts in some of the study areas, and Arctic species shifted significantly faster than boreal species in the Barents Sea. Overall, our results suggest a strong influence of other factors, such as biological interactions, in determining several species' recent geographic shifts.

The pervasiveness of microplastic contamination in the gastrointestinal tract of fish from the western coast of Bangladesh.

This study investigated the prevalence of microplastics (MPs) in the gastrointestinal tract (GIT) of fish from the western coast of Bangladesh, the world's largest mangrove ecosystem. Altogether, 8 different species of fish (5 demersal and 3 pelagic) were examined. Microplastics were detected in every individual fish with an average abundance of 7.1 ± 3.14 particles per specimen. The demersal species were observed to consume more microplastics (7.78 ± 3.51) than the pelagic species (5.92 ± 2.06). Moreover, small-sized fish was found to accumulate higher MPs/body weight than large-sized fish. Polypropylene was the most abundant polymer type (45 %) and fiber was the most prevalent shape (71 %). SEM analysis revealed cracks, pits, and foreign particles on the microplastics' surface, representing their ability to bear organic pollutants and heavy metals. This study will be a source of information for future research and a guide for policy-makers to take better actions to protect and restore marine resources.

Spatiotemporal patterns in the prevalence of microscopic hepatic changes in Gulf of Mexico Tilefish (Lopholatilus chamaeleonticeps) and associations with hepatic PAHs.

Following the 2010 Deepwater Horizon blowout, demersal longline surveys were conducted across the Gulf of Mexico (GoM) continental shelf to evaluate polycyclic aromatic hydrocarbon (PAH) exposure, tissue accumulation, and health indices in demersal fishes. Tilefish (Lopholatilus chamaeleonticeps), a target species due to Gulf-wide distribution with documented high exposure to PAHs, were collected in the north central GoM at repeat stations 2012 to 2015, and from the northwest GoM, Bay of Campeche, and Yucatán Shelf in 2015 and 2016. Liver samples (n = 239) were analyzed for microscopic hepatic changes (MHCs) by a board-certified veterinary pathologist. Histological analyzes identified 14 MHCs. Prevalence of MHCs was generally uniform throughout the GoM, except for low prevalence on the Yucatán Shelf. Inflammatory and vacuolar changes were most prevalent, while pre-neoplasia and neoplasia were rare. Tilefish sampled annually in the north central GoM showed increases in inflammatory MHCs and glycogen-type vacuolar change over time, while lipid-type vacuolar change decreased over time. Short-term exposure to PAHs was assessed by measuring PAH metabolites in bile (n = 100) using high performance liquid chromatography with fluorescence detection. Longer-term accumulation of PAHs in tissue was assessed by analyzing liver (n = 111) for PAHs and alkylated homologs using QuEChERS extractions and gas chromatography tandem mass spectrometry. Six MHCs including glycogen-type vacuolar change, biliary fibrosis, foci of cellular alteration, parasites, hepatocellular atrophy, and necrosis were significantly associated with hepatic PAH accumulation in Tilefish from the northern central GoM; however, no MHCs were associated with biliary PAH metabolites. Combined with previous studies of PAH exposure and health indices in north central GoM Tilefish post-Deepwater Horizon, which also identified decreases in hepatic lipid storage and Fulton's condition factor that were correlated to increasing PAH exposure, these data indicate concerning temporal trends and changes in hepatic energy storage.

Exploring microplastic contamination in reef-associated fishes of the Tropical Atlantic.

Microplastics (MPs) are ubiquitous in marine compartments, and their transboundary distribution favours the dispersion and accumulation of particles in ecosystems. This study investigated MP contamination in four coastal fish species (Haemulon squamipinna, Chaetodon ocellatus, Syacium micrurum, and Alphestes afer) from the southwestern Tropical Atlantic. An alkaline treatment was applied to extract MPs from the digestive tracts, and a Laser Direct Infrared (LDIR) system was used to identify polymers. All species analysed were contaminated with MPs, with Alphestes afer being the most contaminated (1.45 ± 1.09 MPs individual-1; frequency of occurrence 80 %). No significant differences were found in the number and size of detected particles among species. The most common shapes were fibres and films, and polyethylene was the most abundant polymer. This study provides important baseline data on MP contamination in coastal fish species inhabiting complex habitat areas relevant for conserving marine biodiversity.

Historical changes in fish landings indicate a significant shift in fish catch composition and biodiversity loss in the Nile-Delta lakes.

To monitor the changes in fish biodiversity and to elucidate the factors responsible for these changes, the landings composition (LC) over the past 30 years in the Nile-Delta lakes was quantitatively analyzed. The LC data indicates a shift in target species towards demersal opportunistic species. A significant difference (P < 0.001) between two main intervals highlighted in both PERMANOVA and PCA plot; the first interval (1991-2002) is dominated by Tilapia and rare species, while the second interval (2003-2020) is dominated by the opportunistic catfish and mullet species. Noticeable declines in species richness and landings of rare species were observed, where rare taxa either have been overexploited or they may be positively affected by increasing pollution levels than do other dominated species such as Tilapia. In contrast, opportunistic fish species such as catfish and mullet, have flourished in such polluted water due to their ability to tolerate seasonal pollution-related hypoxia.

Assessment of health risks due to toxic metals in demersal fish captured from Saros and Edremit Bays, Northern Aegean Sea.

Bays are vulnerable ecosystems generally located near densely populated areas where toxic metals tend to accumulate and stay longer, affecting marine life. This study aimed to investigate the age-based health risks arising from Hg, Cd, Pb, and As in demersal fish captured from two major bays in the Aegean Sea. For this purpose, red mullet, whiting, piper gurnard, and tub gurnard, frequently consumed species, were caught from Saros and Edremit Bays. Toxic metal concentrations were determined from the muscle tissue of fish. Health risk assessments were conducted by the estimation of weekly intake (EWI), provisional tolerable weekly intake (PTWI), target hazard quotient (THQ), total THQ (TTHQ), and target carcinogenic risk (TR). Red mullet from Edremit Bay was the species with the highest toxic metal levels, which were 1.597 mg/kg, 0.041 mg/kg, 0.070 mg/kg, and 19.351 mg/kg for Hg, Cd, Pb, and As, respectively. Whiting from Edremit Bay had higher mean concentrations of Hg and As than those from Saros Bay. The levels of Hg, Pb, and As (0.328, 0.043, and 0.574 mg/kg) in the tub gurnard were higher in comparison with the piper gurnard (0.252, 0.020, and 0.382 mg/kg) caught in the same station in Saros. TTHQs of red mullet and whiting from the same bay were found to be > 1, indicating potential health risks for all nine age categories studied. On the other hand, TTHQs of all species from Saros Bay were determined to be > 1 for the first four age categories, which might trigger health risks for children and adolescents. According to the TR index for Pb, no risk was determined for the fish from both bays. However, TR calculations for inorganic As indicated high cancer risk in most of the age categories for red mullet and whiting from Edremit Bay. To sum up, the results revealed that the fish captured from Edremit Bay posed serious health risks in terms of Hg and As concentrations for all nine age categories. Surveillance and monitoring of toxic metal levels in demersal fish and population-based health risk evaluation are vital in heavily populated bays.

Parasites of Three Closely Related Antarctic Fish Species (Teleostei: Nototheniinae) from Elephant Island.

BACKGROUND: Studies of parasite communities and patterns in the Antarctic are an important knowledge base with the potential to track shifts in ecological relations and study the effects of climate change on host-parasite systems. Endemic Nototheniinae is the dominant fish group found in Antarctic marine habitats. Through their intermediate position within the food web, Nototheniinae link lower to higher trophic levels and thereby also form an important component of parasite life cycles. The study was set out to gain insight into the parasite fauna of Nototheniops larseni, N. nudifrons and Lepidonotothen squamifrons (Nototheniinae) from Elephant Island (Antarctica). METHODS: Sampling was conducted at three locations around Elephant Island during the ANT-XXVIII/4 expedition of the research vessel Polarstern. The parasite fauna of three Nototheniine species was analysed, and findings were compared to previous parasitological and ecological research collated from a literature review. RESULTS: All host species shared the parasites Neolebouria antarctica (Digenea), Corynosoma bullosum (Acanthocephala) and Pseudoterranova decipiens E (Nematoda). Other parasite taxa were exclusive to one host species in this study. Nototheniops nudifrons was infected by Ascarophis nototheniae (Nematoda), occasional infections of N. larseni with Echinorhynchus petrotschenkoi (Acanthocephala) and L. squamifrons with Elytrophalloides oatesi (Digenea) and larval tetraphyllidean Cestoda were detected. CONCLUSION: All examined fish species' parasites were predominantly euryxenous regarding their fish hosts. The infection of Lepidonotothen squamifrons with Lepidapedon garrardi (Digenea) and Nototheniops larseni with Echinorhynchus petrotschenkoi represent new host records. Despite the challenges and limited opportunities for fishing in remote areas, future studies should continue sampling on a more regular basis and include a larger number of fish species and sampling sites within different habitats.

Abundance and characteristics of microplastics in gastrointestinal tracts and gills of croaker fish (Johnius dussumieri) from off Mumbai coastal waters of India.

The present study was conducted to establish the intensity of microplastic pollution in demersal fish species, Johnius dussumieri, from the north eastern coastal waters of the Arabian sea. MP recovered were analysed for size, morphology, colour, and polymer type. The study results indicated that the GI tract and gills of individual fishes had 6.6 ± 1.7 and 6.2 ± 1.7 items, respectively. The microplastics having a size of <100 µm consisting of beads were found to be most predominant. Black and blue were the most present colours of microplastic in the tissues. Among the different studied months, a higher number of MP incidence was observed in the post monsoon period. There is no significant correlation observed between the microplastic numbers in gills and guts tissue. The present study shows that there is a potential risk of microplastic bioaccumulation in the fish body and subsequent risk to the consumers and organisms sharing the food chain.