When a fish is caught by angling and released, it is unclear for how long that fish will be able to remember the experience and exhibit hook avoidance. Previous research in ponds using carp (Cyprinus carpio) as a model are suggested that in this species a single hooking event might be enough to cause hook avoidance to last over one year. We re-examined this finding, determining whether private (i.e., personal experience of a catch-and-release event) or social (i.e., sensing a conspecific being hooked and released) hooking experiences maintains hook avoidance 7 and 14 months from the initial experience. A fully controlled laboratory experiment was used that recorded the behavior towards sham-rigs where the hook tip was removed, which served as measure for hook avoidance. Although individuals with a private hooking experience required more time to pick up the sham rig 7 months after the initial hooking relative to controls, no differences in ultimate ingestion rates over a time period of 600 s were found, indicating a more cautious approach to the hook but the loss of hook avoidance after 7 months. For carp with a one-trial social hooking experience, neither an increased latency to ingest the offered sham rig nor differences in ingesting rates compared to never-hooked controls were found, indicating that the carp had forgotten that experience after about half a year. Thus, the previous findings from pond studies with group-held carp according to which one-trial hooking is enough to reduce the capture probability one year after the event could not be replicated in carp tested alone in the laboratory. It is unclear whether strain differences, lack of statistical power or differences in the set up alone or in combination explain the differences in study outcomes.
Climatic extremes are becoming increasingly common against a background trend of global warming. In the oceans, marine heatwaves (MHWs)—discrete periods of anomalously warm water—have intensified and become more frequent over the past century, impacting the integrity of marine ecosystems globally. We review and synthesize current understanding of MHW impacts at the individual, population, and community levels. We then examine how these impacts affect broader ecosystem services and discuss the current state of research on biological impacts of MHWs. Finally, we explore current and emergent approaches to predicting the occurrence and impacts of future events, along with adaptation and management approaches. With further increases in intensity and frequency projected for coming decades, MHWs are emerging as pervasive stressors to marine ecosystems globally. A deeper mechanistic understanding of their biological impacts is needed to better predict and adapt to increased MHW activity in the Anthropocene. Expected final online publication date for the Annual Review of Marine Science, Volume 15 is January 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Atlantic salmon will experience periods of fasting during its lifecycle. In nature, prolonged fasting periods occur owing to seasonal fluctuations in available feeds, migration or in relation to reproduction. In a culture setting, salmon is fasted mainly as part of planned operational handling prior to vaccination, delousing, transfer etc., and where fasting may last up to nine days. The mechanisms regulating the appetite during long-term fasting may vary among fish species. Here, we studied the impact of long-term fasting on neuro-endocrine regulation of appetite through the stomach-hypothalamic axis in Atlantic salmon post smolts (1.2 kg, ~46 cm), reared in two experimental conditions (Fed and Fasted; triplicated tanks), and sampled after 4 weeks and 6 weeks of fasting. Fasted fish showed lower condition factor and hepatosomatic index at both sampling points compared to Fed group. In qPCR analysis, hypothalamic relative mRNA expression of agouti-related protein 1 (agrp1) was upre-gulated in fasted group at both sampling points. Among neuropeptide Y (npy) paralogs, only npya1 at 4 weeks was upregulated by fasting. As for cocaine-and amphetamine-regulated transcripts (cart), cart2a was elevated at 4 weeks, and cart2b at both 4 and 6 weeks in fasted group, while cart3a and cart4 showed no response to fasting. The pro-opiomelanocortin (pomc) a1, a2 and melanocortin-4 receptor (mc4r) a2 increased only after 6 weeks of fasting, while mc4rb1 did not respond to fasting. In stomach, 6 weeks of fasting resulted in a decrease of ghrelin1 (ghrl1), while expression of mboat4 was unaffected. The elevated levels of hypothalamic agrp1 and npya1 in fasted group support orexigenic roles for these neuropeptides. In addition, upregulation of cart2a, cart2b, pomca1 and pomca2 indicate that these play vital roles in appetite regulation and that fasting may halt and/or counteract hunger signals (agrp1 and npya1) to save energy from foraging search activities during catabolic conditions. Another possibility is that these neuropeptides play a role in fasting-induced stress. Based on the drop in mRNA expression of ghrl under catabolic conditions, we hypothesize that Ghrl might return as hunger signal once feed becomes available. We also propose that agrp1 is a potential appetite biomarker gene under feed deprived conditions.
Though a naturally occurring species throughout the Atlantic, parasitic salmon louse (Lepeophtheirus salmonis) population dynamics are increasingly intertwined with salmonid aquaculture. In contrast to reactive louse management, tools and strategies which reduce louse infestation success provide an off-ramp from the 'more farming equals more lice' feedback loop. This experiment tested the efficacy of a dynamic, environmentally responsive louse prevention strategy using common, commercially available tools throughout a full production cycle at commercial scale. By strategically luring salmon away from the halocline where concentrations of infective louse copepodids are highest using feeding and lights, and minimizing surface water flow through the cage with a protective skirt barrier when no halocline was present, both new louse infestations and mobile louse numbers were cut by half compared to control cages. The reduced louse numbers resulted in 25% fewer delousing events and improved fish welfare in dynamic cages, with no differences in gill condition or growth between treatments. With farmed salmon driving the ecology of salmon lice, this dynamic, environmentally responsive prevention strategy offers a way to work with nature, rather than against it, to reduce the parasite burden on both farmed and wild salmonids.
The aim of the current work was to investigate the impact of marine aquaculture on seafloor biogeochemistry and diversity from pristine environments in the northern part of Norway. Our analytical approach included analyses of 182 samples from 16 aquaculture sites using 16S and 18S rRNA, shotgun analyses, visual examination of macro-organisms, in addition to chemical measurements. We observed a clear bimodal distribution of the prokaryote composition and richness, determined by analyses of 16S rRNA gene operational taxonomic units (OTUs). The high OTU richness cluster was associated with non-perturbed environments and farness from the aquaculture sites, while the low OTU richness cluster was associated with perturbed environments and proximity to the aquaculture sites. Similar patterns were also observed for eukaryotes using 18S rRNA gene analyses and visual examination, but without a bimodal distribution of OTU richness. Shotgun sequencing showed the archaeum Nitrosopumilus as dominant for the high OTU richness cluster, and the epsilon protobacterium Sulfurovum as dominant for the low OTU richness cluster. Metabolic reconstruction of Nitrosopumilus indicates nitrification as the main metabolic pathway. Sulfurovum, on the other hand, was associated with sulfur oxidation and denitrification. Changes in nitrogen and sulfur metabolism is proposed as a potential explanation for the difference between the high and low OTU richness clusters. In conclusion, these findings suggest that pollution from elevated loads of organic waste drives the microbiota towards a complete alteration of respiratory routes and species composition, in addition to a collapse in prokaryote OTU richness.
Mass mortality events are ubiquitous in nature and can be caused by, for example, diseases, extreme weather and human perturbations such as contamination. Despite being prevalent and rising globally, how mass mortality in early life causes population-level effects such as reduced total population biomass, is not fully explored. In particular for fish, mass mortality affecting early life may be dampened by compensatory density-dependent processes. However, due to large variations in year-class strength, potentially caused by density-independent variability in survival, the impact at the population level may be high in certain years. We quantify population-level impacts at two levels of mass mortality (50% and 99% additional mortality) during early life across 40 fish species using age-structured population dynamics models. The findings from these species-specific models are further supported by an analysis of detailed stock-specific models for three of the species. We find that population impacts are highly variable between years and species. Short-lived species that exhibit a low degree of compensatory density dependence and high interannual variation in survival experience the strongest impacts at the population level. These quantitative and general relationships allow predicting the range of potential impacts of mass mortality events on species based on their life history. This is critical considering that the frequency and severity of mass mortality events are increasing worldwide.
Mesopelagic organisms play a crucial role in marine food webs, channelling energy across the predator-prey network and connecting depth strata through their diel vertical migrations. the information available to assess mesopelagic feeding interactions and energy transfer has increased substantially in recent years, owing to the growing interest and research activity in the mesopelagic realm. However, such data have not been systematically collated and are difficult to access, hampering estimation of the contribution of mesopelagic organisms to marine ecosystems. Here we present Mesoptroph, a georeferenced database of diet, trophic markers, and energy content of mesopelagic and other marine taxa compiled from 203 published and non-published sources. MesopTroph currently includes data on stomach contents, carbon and nitrogen stable isotopes, major and trace elements, energy density, fatty acids, trophic positions, and diet proportion estimates for 498 species/genera. MesopTroph will be expanded with new data emerging from ongoing studies. Mesoptroph provides a unique tool to investigate trophic interactions and energy flow mediated by mesopelagic organisms, and to evaluate the ecosystem services of this community.
To protect and restore ecosystems and biodiversity is one of the 10 challenges identified by the United Nations's Decade of the Ocean Science. In this study we used eDNA from sediments collected in two fjords of the Svalbard archipelago and compared the taxonomic composition with traditional methods through metabarcoding, targeting mitochondrial CO1, to survey benthos. Clustering of 21.6 mill sequence reads with a d value of 13 in swarm, returned about 25 K OTU reads. An identification search with the BOLD database returned 12,000 taxonomy annotated sequences spanning a similarity range of 50% to 100%. Using an acceptance filter of minimum 90% similarity to the CO1 reference sequence, we found that 74% of the ca 100 taxon identified sequence reads were Polychaeta and 22% Nematoda. Relatively few other benthic invertebrate species were detected. Many of the identified sequence reads were extra-organismal DNA from terrestrial, planktonic, and photic zone sources. For the species rich Polychaeta, we found that, on average, only 20.6% of the species identified from morphology were also detected with DNA. This discrepancy was not due to missing reference sequences in the search database, because 90-100% (mean 96.7%) of the visually identified species at each station were represented with barcodes in Boldsystems. The volume of DNA samples is small compared with the volume searched in visual sorting, and the replicate DNA-samples in sum covered only about 2% of the surface area of a grab. This may considerably reduce the detection rate of species that are not uniformly distributed in the sediments. Along with PCR amplification bias and primer mismatch, this may be an important reason for the limited congruence of species identified with the two approaches. However, metabarcoding also identified 69 additional species that are usually overlooked in visual sample sorting, demonstrating how metabarcoding can complement traditional methodology by detecting additional, less conspicuous groups of organisms.
Animals need to move between different habitats to successfully complete their life cycle. Anthropogenic activities and infrastructure impact animal movement, especially in the aquatic realm, due to habitat alteration (including fragmentation), pollution, overexploitation, the spread of invasive alien species and climate change. Gaining knowledge on the complex phenomenon of fish movement is essential to understand the diverse ways in which anthropogenic activities may influence the spatial ecology of fish, which can inform management. The four main methods to study fish movement are through observation and interception, electronic tracking, otolith chemistry and environmental DNA. We discuss the strengths and shortcomings of these methods and suggest effective management can be aided by combining these and other methods. Often the weaknesses of one technique can be met by the strengths of the others. Also, cross-boundary collaboration is essential for the successful management of fish that move over jurisdictional boundaries to complete their life cycle. Data analyses on interdisciplinary datasets obtained at spatial scales relevant to the movement ecology of a given population can yield a more holistic understanding of fish movement. This knowledge may help for the appropriate selection of cost-efficient, evidence-based and effective management actions that balance the needs of fishes and human activities. Graphical abstract
Shell debris increases habitat diversity and ecological heterogeneity, stabilizing sediments and providing substrate for encrusting and epifaunal animals and protection against predation. However, how shell debris influences disturbance-recovery dynamics in different habitats has not been evaluated. We experimentally tested the effects of shell debris on early colonization of macroinvertebrates into defaunated patches across 12 sites along a mud-to-sand gradient. The addition of shell debris enhanced species richness compared to plots without shells and increased variability in the local contributions to beta-diversity, mostly at the muddier sites. The variation in the strength of these effects along the mud gradient highlights the effects of shell debris on community structure and how the muddying of coastal sediments shifts species composition. Loss of shellfish and burying of shells with elevated rates of sedimentation diminishes the role of small-scale sediment heterogeneity for sustaining beta-diversity in low-energy environments.
Large-scale, climate-induced synchrony in the productivity of fish populations is becoming more pronounced in the world's oceans. As synchrony increases, a population's 'portfolio' of responses can be diminished, in turn reducing its resilience to strong perturbation. Here we argue that the costs and benefits of trait synchronization, such as the expression of growth rate, are context dependent. Contrary to prevailing views, synchrony among individuals could actually be beneficial for populations if growth synchrony increases during favourable conditions, and then declines under poor conditions when a broader portfolio of responses could be useful. Importantly, growth synchrony among individuals within populations has seldom been measured, despite well-documented evidence of synchrony across populations. Here, we used century-scale time series of annual otolith growth to test for changes in growth synchronization among individuals within multiple populations of a marine keystone species (Atlantic cod, Gadus morhua). On the basis of 74,662 annual growth increments recorded in 13,749 otoliths, we detected a rising conformity in long-term growth rates within five northeast Atlantic cod populations in response to both favorable growth conditions and a large-scale, multidecadal mode of climate variability similar to the East Atlantic Pattern. The within-population synchrony was distinct from the across-population synchrony commonly reported for large-scale environmental drivers. Climate-linked, among-individual growth synchrony was also identified in other Northeast Atlantic pelagic, deep-sea and bivalve species. We hypothesize that growth synchrony in good years and growth asynchrony in poorer years reflects adaptive trait optimisation and bet hedging, respectively, that could confer an unexpected, but pervasive and stabilizing, impact on marine population productivity in response to large-scale environmental change.
Fishery inspector logbooks were used to estimate fishing gear interaction rates for humpback (Megaptera novaeangliae) and killer (Orcinus orca) whales in Norwegian purse seine fisheries for herring from 2011 to 2020. Estimated rates were applied to fisheries data to estimate fleet‐wide totals. Estimates showed that in a 10‐year period, a total of 78 humpback whales, 95% CI [41, 145] and 100 killer whales, 95% CI [63, 176] were entrapped in purse seines. Most whales were disentangled alive, with an estimated mortality of 5%, CV 0.69, 95% CI [0.0, 11.8] and 6%, CV 0.48, 95% CI [0.3, 11.9], respectively. The average yearly mortality over the study period was thus approximately 0.60 killer whales and 0.39 humpback whales corresponding to 0.008% and 0.007% of the respective abundance estimates for these whale species in Norwegian waters. Given the Potential Biological Removal sustainability limits of 98 humpbacks and 161 killer whales per year, it may be concluded that, by itself, the average yearly mortality incurred by these whale populations by Norwegian fisheries does not constitute a significant risk to either of these species, but bycatch in Norwegian purse seine fisheries may not be the only source of anthropogenic mortality.
Otoliths (ear-stones) in the inner ears of vertebrates containing visible year zones are used extensively to determine fish age. Analysis of otoliths is a time-consuming and difficult task that requires the education of human experts. Human age estimates are inconsistent, as several readings by the same human expert might result in different ages assigned to the same otolith, in addition to an inherent bias between readers. To improve efficiency and resolve inconsistent results in the age reading from otolith images by human experts, an automated procedure based on convolutional neural networks (CNNs), a class of deep learning models suitable for image processing, is investigated. We applied CNNs that perform image regression to estimate the age of Greenland halibut ( Reinhardtius hippoglossoides ) with good results for individual ages as well as the overall age distribution, with an average CV of about 10% relative to the read ages by experts. In addition, the density distribution of predicted ages resembles the density distribution of the ground truth. By using k*l -fold cross-validation, we test all available samples, and we show that the results are rather sensitive to the choice of test set. Finally, we apply explanation techniques to analyze the decision process of deep learning models. In particular, we produce heatmaps indicating which input features that are the most important in the computation of predicted age.
Since the first observation of snow crab (Chionoecetes opilio) in the Barents Sea in 1996, the population has increased significantly, supporting a commercial fishery on the Norwegian shelf since 2012. To investigate whether the availability of benthic prey organisms may support a continued geographical snow crab expansion, benthic invertebrate production was studied across the central parts of the Barents Sea and around Svalbard, where snow crabs are currently absent or at low densities. Annual productivity (P/B ratio) from 66 stations collected by grab and beam trawl was estimated using a multiparameter artificial neural network model. Mean infaunal productivity and production were 0.43 yr−1 and 38.4 g ww m−2 yr−1, respectively, while the epifaunal production was considerably lower with 2.5 g ww m−2 yr−1. The proportions of epi- and infaunal production suitable as prey for snow crab were 98 and 96%, respectively. Areas close to the Polar Front represent the most attractive snow crab foraging region, having the highest benthic secondary production, high estimated primary production, and bottom water temperatures within the snow crab’s preferences. At snow crab densities of 12800 ind. km−2, high enough to support commercial fishing, their mean consumption rate was estimated to be around 1.5 g ww m−2 yr−1, which amounts to 4% of mean infaunal prey production. Food availability is, therefore, not expected to be a hindrance to further population expansion of the snow crab in the Barents Sea.
Marine litter in the Arctic Basin is influenced by transport from Atlantic and Pacific waters. This highlights the need for harmonization of guidelines across regions. Monitoring can be used to assess temporal and spatial trends but can also be used to assess if environmental objectives are reached, for example to evaluate the effectiveness of mitigation measures. Seafloor monitoring by trawling needs substantial resources and specific sampling strategies to be sufficiently robust to demonstrate changes over time. Observation and visual evaluation in shallow and deep waters using towed camera systems, ROVs and submersibles are well suited for the Arctic environment. The use of imagery still needs to be adjusted through automation and image analyses, including deep learning approaches and data management, but will also serve to monitor areas with a rocky seafloor. We recommend developing a monitoring plan for seafloor litter by selecting representative sites for visual inspection that cover different depths and substrata in marine landscapes, and recording the litter collected or observed across all forms of seafloor sampling or imaging. We need better coverage and knowledge of status of seafloor litter for the whole Arctic and recommend initiatives to be taken for regions where such knowledge is lacking.
The Cascaded H-Bridge (CHB) multilevel converter is an attractive solution for integrating Photovoltaic (PV) generators with the ac grid. However, the power generated in the PV panels may be unequal due to partial shading, temperature change, and dust layer accumulation leading to unequal and unbalanced power between the phases and possible violation of power quality constraints. Fundamental Frequency Zero-Sequence Voltage (FFZSV) injection can be applied but this method can produce overmodulation in conditions with high PV power mismatch. A new FFZSV is proposed in this paper assuming a CHB with a Battery Energy Support (BES) to compensate for the effects of unbalanced PV power generation. A barycentric coordinate representation helps to determine the capacity of the BES required. A coordinated control between the PV system and BES is also proposed in the paper. Additionally, a novel approach to deliberate FFZSV injection is discussed in this paper by which the maximum charge and discharge rate for the BES can be obtained along with balanced current injection into the grid. The effectiveness of the proposed technique is verified in numerical simulations and with experimental results.
Our goal was to examine how the epibenthic invertebrate community in the Pacific Arctic Region might be affected by continued increases in ocean temperatures. We used epibenthic invertebrate catch and bottom temperature data collected on groundfish assessment and ecosystem surveys in the Bering and Chukchi seas from 2009 to 2018 to determine the “preferred” temperature of all taxa. We grouped taxa into five clusters according to their similarity in median temperature and temperature range. We then used an ensemble of eight climate models under Representative Concentration Pathway 8.5 (RCP8.5) scenarios to project bottom temperature from present (2008) to mid-century (2050) and end of the century (2100). Based on these projections, we show how the amount and distribution of cluster-specific thermal habitat might change with ocean warming. We found that by mid-century there was a 50% decrease in thermal habitat for all clusters except for the most eurythermic cluster, and that thermal habitat contracted to the north. By the end of the century there was very little thermal habitat for all clusters, except the most eurythermic cluster, and habitat was further contracted to the north. The cold-water and stenothermic cluster, hypothesized to be the most vulnerable to ocean warming, had virtually no projected thermal habitat by the end of the century. These “losers” were primarily gastropods and the bivalve mussel Musculus sp. These taxa are some of the primary prey to the endangered Pacific walrus (Odobenus rosmarus), which is harvested as a food resource in native Alaskan communities. Bivalves are prey for commercial flatfish such as yellowfin sole (Limanda aspera) and Alaska plaice (Pleuronectes quadrituberculatus). By 2100 the most eurythermic cluster, hypothesized to be the least vulnerable to warming, had projected suitable thermal habitat throughout most of the Bering and Chukchi seas, except nearshore coastal regions. The most abundant species of these “winners” was the basketstar Gorgonocephalus cf. arcticus. The loss of thermal habitat for all but the “winners” could impact the species diversity of the Bering and Chukchi seas because the “winner” cluster accounted for only 26 taxa or 8% of all taxa observed. Although temperature is a key determinant of habitat, a full habitat and ecosystem model is needed to provide more detailed predictions. In addition, more laboratory studies of thermal acclimation potential of Arctic benthic invertebrates are needed. Our results provide the first indications that the epibenthic invertebrate community in the Bering and Chukchi seas, which supports marine mammals, seabirds and human communities, may be seriously impacted by future ocean warming.
Our understanding of the benthic communities on arctic seamounts and descriptions of such communities in habitat classification systems are limited. In recent years, Schulz Bank (73°52′N 7°30′E), a seamount on the Arctic Mid-Ocean Ridge (AMOR), has become well studied but the work has primarily focused on an arctic sponge ground at the summit. This has compounded a general assumption that the most biologically interesting community is on the summit alone. With the potential threat of deep-sea mining on nearby sites on AMOR, it is crucial to form a baseline understanding of the benthic megafaunal communities not only on the summit, but on the slopes and base of the seamount as well. Using video footage collected by a remotely operated vehicle in 2017 and 2018 to survey the seamount from 2700 to 580 m depth, several distinct megafauna communities on Schulz Bank were identified. Specifically, five biotopes, two of which were dominated by large structure-forming sponges, appeared to follow a depth gradient and change with the type of substrata present. The sponge-dominated communities on the summit and lower slope had the highest average community densities and number of morphotaxa per image compared to the upper slope and seamount base communities. Most notably, sponge-dominated bedrock walls on the lower slopes challenge the assumption that the summit is the most dense and diverse community on Schulz Bank. The results from this study lay the foundation for future research and conservation efforts of arctic sponge grounds by looking beyond the seamount summit to bring a full view of enigmatic sponge dominated ecosystems.
Recent studies have found that feeding high levels of long chain polyunsaturated fatty acids (LC-PUFA) influenced the steroid biosynthesis pathway of Atlantic salmon on a transcriptomic level, although research observed on a metabolic level is lacking. Dietary lipid and chronic stress have also been suggested to play a role in steroidogenesis. A study was performed on Atlantic salmon post-smolts (184 g) fed with diets of high and low levels of lipid with and without high levels of LC-PUFA under hypoxic (stressed) or normoxic (unstressed) conditions. Liver, head kidney and blood samples were collected after 35 and 116 days to determine short- and long-term effects. On day 35, dissolved oxygen affected the levels of the steroid hormones 11-deoxycortisol, cortisone and testosterone as well as the relative expression of cyp11a involved in steroidogenesis and ud2a2 involved in sex steroid metabolism. On day 116, an interaction between lipid x LC-PUFA x oxygen was found for cyp11a, hsd3b (steroidogenesis) and ud2a2 genes, whereas LC-PUFA and/or oxygen affected the steroid levels of 11-dehydrocorticosterone, corticosterone, cortisol, dehydroepiandrosterone (DHEA), pregnenolone and testosterone. The observation that both LC-PUFA and oxygen affected cyp11a expression and the levels of pregnenolone, provides evidence for the influence of both parameters on the rate-limiting point of steroid production, which can take >35 days to establish. The 3-way interaction between lipid, LC-PUFA and dissolved oxygen on the expression of steroid genes suggests that the chronic stressor of hypoxia may be over-riding dietary influences of the lipid and LC-PUFA, though the relative proportion of LC-PUFA within the lipid may play a role as well. In terms of fatty acid composition, low dietary lipid and high LC-PUFA increased the levels of total n-6 and n-3 PUFA in the liver, particularly EPA and DHA, and the head kidney to a lesser extent. In terms of immune pathways, hypoxia influenced cytokine gene expression (tgfb, il10), cellular repair gene expression (gr, hsp70 and hsp90) and eicosanoid levels (PGE2 and LTB5) in the head kidney, while dietary lipid and LC-PUFA influenced cytokines (ifnγ and il1β) and eicosanoids (PGE2 and LTB5). These findings demonstrate that feeding different levels of LC-PUFA significantly alters steroidogenesis and innate immune response in Atlantic salmon post-smolts with additional interactions from dietary lipid and hypoxia stress. These results will significantly impact the aquaculture industry since it demonstrates salmon fed high levels of LC-PUFA are likely more resilient to cope with chronic stressors (e.g. prolonged hypoxia) due to lower corticosteroid levels and higher immune response.
Objectives The aim of the study was to understand the genetic basis of resistance of five β-lactam resistant Vibrio anguillarum isolates obtained from the gut content of migratory fish Atlantic mackerel (Scomber scomberus) using whole genome sequencing and to characterize a novel β-lactamase (VAN-1) from these isolates. Method Antibiotic sensitivity pattern was determined using Sensititre™ plates and whole genome sequencing was carried out using Illumina MiSeq-based sequencing. The blaVAN-1 gene was synthesized and expressed in Escherichia coli Top10 cells. Results Five isolates obtained (out of 73) from the gut content of Atlantic mackerel were identified as Vibrio anguillarum. Whole genome assemblies ranged from 3.894 to 3.906 million bases in length with an average of 50 contigs. A novel β-lactamase blaVAN-1, sharing 77.7% nucleotide identity with a known mobile β-lactamase from Vibrio species was detected. The blaVAN-1 gene in these isolates is flanked by a truncated IS5 family transposase on one end and a hypothetical protein and outer membrane protein followed by another IS5 family transposase on the other end, suggesting its potential for mobility. The blaVAN-1 gene was absent in V. anguillarum type strain (ATCC 14181) and V. anguillarum isolates from bivalves and sea water in Norway. VAN-1 conferred ampicillin resistance when expressed in E. coli, thus confirming the functionality of this gene. Conclusions Our study highlight the importance of marine environment as a reservoir of new antibiotic resistance genes. Our results suggest that migratory fish may transport novel antibiotic resistance determinants over long distances.
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