Wild Fish Research Articles

Socio-ecological change in bait fisheries for the common sandprawn Kraussillichirus kraussi in Durban Harbour, South Africa

Bait fishing for the common sandprawn Kraussillichirus kraussi in Durban Harbour, on the east coast of South Africa, has a history going back to the early 20th century and has been influenced by port development and political changes over time. Recent controversy has centred on the fishers’ rights to port access and on the interactions between two sectors that harvest sandprawns for bait. The two sectors are a recreational bait fishery and an unlicensed subsistence (or small-scale) fishery that sells its catches to anglers for an income, in contravention of fisheries regulations. To determine the spatiotemporal extent of the fisheries and the impacts of bait fishing on the sandprawn resource, data on the fishing effort, catch and size composition were collected monthly at the sandbank sites Centre Bank and Wilson’s Wharf in Durban Harbour. A generalised linear modelling framework was used to analyse fishing effort and sandprawn size composition. Small-scale fishers dominated the bait fishery (83%), and fishing effort peaked at low tides and on public holidays and weekends, when the market demand for sandprawns as bait was higher. Fishing effort differed significantly between sandbanks and was dynamic, shifting to Centre Bank when sandprawn abundance at Wilson’s Wharf decreased. Small-scale fishers mainly retained large sandprawns, and did not adhere to daily catch limits, such as those regulating the recreational bait fishery. The results are interpreted from a socio-ecological systems perspective, and within the context of accommodating otherwise excluded small-scale fisheries within South African fisheries legislation.

Individual Behavioral Syndromes and Shoal Characteristics in Farmed and Wild Acrossocheilus fasciatus

This study investigates the individual behavioral syndromes and shoal characteristics of farmed and wild populations of the cyprinid Acrossocheilus fasciatus to elucidate the factors influencing the efficacy of fish stock enhancement. We examined two wild populations from Quzhou and Lishui, in Zhejiang Province, China, and one farmed population from the same geographical location as the Quzhou wild population. Individual behavioral syndromes were thoroughly evaluated alongside shoal characteristics. Results indicated that farmed A. fasciatus exhibited greater boldness, exploratory behavior, and sociability compared to their wild counterparts. Wild populations demonstrated distinct behavioral traits, with the Quzhou population showing reduced locomotor activity and sociability, and the Lishui population displaying timidity. Shoal analysis revealed that wild fish had higher cohesion and shoal synchronization compared to farmed fish. Additionally, mixed groups exhibited intermediate locomotor behaviors but decreased cohesion, particularly in the Quzhou population. These findings underscore significant behavioral differences between farmed and wild fish, as well as among wild fish from different geographical locations, emphasizing the need for tailored training and environmental modifications in stock enhancement programs to improve survival.

Phylosymbiosis in Seven Wild Fish Species Collected Off the Southern Coast of Korea: Skin Microbiome Most Strongly Reflects Evolutionary Pressures

Phylosymbiosis is defined as the relationship in which the microbiome recapitulates the phylogeny of the host and has been demonstrated in a variety of terrestrial organisms, although it has been understudied in fish, the most phylogenetically diverse vertebrate. Given that the species-specificity of fish microbiomes was detected in multiple body parts and differed by body parts, we assumed that the phylogenetic reflection of the microbiome would differ across body parts. Thus, we analyze the difference of phylosymbiotic relationships in the microbial communities found in three body parts (skin, gills, and intestine) of seven wild fish species from four families (Labridae, Sebastidae, Sparidae, and Rajidae) via 16S rRNA gene amplicon sequencing. Fishes were purchased at Docheon port market in Tongyeong City, Korea and were transported to nearby research institutes for aliveness. Mantel tests using dissimilarity values of microbiomes and hosts’ divergence times showed that the differences in microbial communities in all three body parts were related to the hosts’ divergence time. This pattern was the most pronounced in the skin. Furthermore, fishes from the same family showed similar bacterial compositions on their skins and gills, with clear differences depending on the family, with the exception of Labridae. These results suggest that the skin microbiome is particularly vulnerable to evolutionary pressures. We hypothesized that the evolution of the fish immune system and the difference in feeding habits induced the stronger phylosymbiotic signal in the skin. Collectively, this dataset will be useful for understanding the fish microbiome and give insights into phylosymbiosis of aquatic animals across body parts.

The gut microbiome and resistome of yellow perch (Perca flavescens) living in Minnesota lakes under varying anthropogenic pressure

Anthropogenic activities can significantly impact wildlife in natural water bodies, affecting not only the host's physiology but also its microbiome. This study aimed to analyze the gut microbiome and antimicrobial resistance gene profile (i.e., the resistome) of yellow perch living in lakes subjected to different levels of anthropogenic pressure: wastewater effluent-impacted lakes and undeveloped lakes. Total DNA and RNA from gut content samples were extracted and sequenced for analysis. Results indicate that the gut resistome and microbiome of yellow perch differ between lakes, perhaps due to varying anthropogenic pressure. The resistome was predominated by macrolide resistance genes, particularly the MLS23S group, making up 53 % of resistome sequences from effluent-impacted lakes and 73 % from undeveloped lakes. The colistin resistance gene group (mcr) was detected in numerous samples, including variants associated with Aeromonas and the family Enterobacteriaceae. The gut microbiome across all samples was dominated by the phyla Proteobacteria, Firmicutes, and Actinobacteria, with the opportunistic pathogens Plesiomonas shigelloides and Aeromonas veronii more abundant in effluent-impacted lakes. Metagenomic analysis of wild fish samples offers valuable insights into the effects of anthropogenic pressures on microbial communities, including antimicrobial resistance genes, in water bodies.

Microplastics in marine fish: a mini-review on presence, classification, and impacts.

Plastic production has experienced exponential growth in recent years due to its diverse industrial applications, low cost, and high availability, also causing issues, since plastic waste in aquatic ecosystems transforms into microplastics (MPs) through mechanical and weathering processes. Microplastics are distributed ubiquitously in water bodies, where they can be ingested by a wide aquatic organism range, including fish, which have been used as bioindicators to assess microplastic presence and toxicity. Research has revealed microplastic presence in various fish species worldwide; the most common characteristics are fibers and fragments of blue, black, and transparent colors, and polyethylene, terephthalate, polypropylene and cellophane chemical composition. Experimental studies under laboratory conditions have demonstrated microplastics impact on fish, showing physical, immunological, and hematological damage, and oxidative stress ultimately leading to organisms' death. However, laboratory results do not necessarily predict impacts on wild fish due to different conditions to which the organisms are exposed. Therefore, further research needs to simulate real scenarios faced by wild fish in the marine environment, providing greater certainty about microplastic impacts and negative effects.

Toward Sustainable Fisheries: Assessing Catch per Unit Effort, Retained Bycatch, and Discard Ratios in the Red Sea Shrimp Trawl Fishery of the Kingdom of Saudi Arabia

Shrimp trawl fishery is of significant importance in Saudi Arabia’s marine capture fishery sector. Al Qunfudhah and Jizan are the only ports along the southern Saudi Arabian coast of the Red Sea dedicated to shrimp fishing. This study evaluates the catch per unit effort (CPUE) of targeted shrimp species along with the associated retained bycatch and discard ratios across these two trawling locations. Using daily catch data from commercial shrimp trawlers specific to each port’s vessel type, this research provides the first comprehensive analysis of CPUE dynamics and fishing practices in these fishing grounds. The CPUE of target shrimps exhibited a wide range (0.01 kg h−1 to 13.08 kg h−1) with an overall mean of 1.37 ± 0.143 kg h−1. Penaeus semisulcatus emerged as the predominant species (mean CPUE: 3.77 ± 0.28 kg h−1), followed by Metapenaeus monoceros (mean CPUE: 0.1 ± 0.02 kg h−1). Significant differences in CPUE were observed among species, including P. semisulcatus, Penaeus hathor, and Penaeus pulchricaudatus, although CPUE differences between the two fishing grounds were minor, likely due to their proximity and similar environmental conditions. The bycatch analysis identified a total of 72 species across 28 families, with significant variation in the relative ratios. Sepiidae species constituted 31.8% of the total bycatch, followed by Portunidae species (24.8%). Discard patterns also varied, with Gerres oyena being the most commonly discarded species (mean discard ratio: 11.37% ± 1.89%), followed by Equulites klunzingeri (mean discard ratio: 8.76% ± 2.00%). While CPUE differences between Al Qunfudhah and Jizan were modest, this study highlights the need for expanded spatial and temporal coverage to enhance future analyses. These findings underscore the importance of integrated data for a comprehensive understanding of fishing effort and bycatch dynamics, supporting sustainable fisheries management in the Red Sea. By addressing bycatch and discard practices, this research contributes to efforts to mitigate ecological impacts and promote sustainable resource use in Saudi Arabia’s fisheries sector.

Monitoring Fish Bacterial Pathogens of Wild Fish Species From the South China Sea by Applying Next-Generation Sequencing on Gill Tissue.

The classic epidemiological triangle model of host-environment-pathogen is recently being reshaped into a tetrahedron, with the growing understanding of the importance of the microbiome in this array. The gills, being a gateway into the fish body, bearing an important role in fish homeostasis, host a complex microbiome that reflects the ambient water, while also showing resemblance to gut microbiome. Next-generation sequencing (NGS) and improvements in data analysis tools enable researchers to gather and analyse a lot more data than ever before, take a closer, more detailed look at microbiota, and gain a much better understanding of the biological processes at work in these complex relations. Here, 16S rRNA amplicons of bacterial DNA extracted from the gills of 36 asymptomatic specimens of three wild fish species from the South China Sea (Nemipterus japonicus, Alepes djebaba, and Saurida tumbil) were sequenced using NGS. Data analyses revealed the presence of 20 potentially pathogenic species, including several zoonotic agents. Gill microbiota exhibited host species-specificity, and expressed a significant difference between demersal and pelagic-amphidromous fish. It is suggested that this method be more widely implemented, in order to gain more insight on ocean ecosystems' health status, as well as fish stocks of commercial importance.

Single pass saltwater disinfection using low voltage electrolysis: Potential implications for aquaculture systems

Open net pen saltwater aquaculture faces criticism due to the potential transmission of pathogens between fish farms and to wild stocks. To address this issue and improve the sustainability and growth of net pen farming, closed containment farms have been suggested, but the cost and feasibility of disinfecting large volumes of water in these types of farms is problematic. We explored the potential for using electrolysis to disinfect saltwater in a flow-through system with water flow velocities between 47 and 105 cm/s. This was the first step to investigating whether this technology could be applied to saltwater flow-through closed containment systems. Various voltage levels (3.3–9.0 V) were applied to generate chlorine from saltwater. We found the disinfection properties of the system varied with wattage (i.e., voltage × ampere), velocity of water flow over the electrodes, salinity of water, and residual chlorine contact time. Wattage was highly correlated with the production of chlorine, and this relationship was dependent on water flow (p = 0.0398). A slower flow velocity led to higher chlorine concentration, and the effect was more pronounced at higher wattages. Using a zero-inflated negative binomial regression model, we found the probability of full disinfection was increased by increasing wattage (p < 0.001) and the residual chlorine contact time (p < 0.001). The level of disinfection (count model) suggested the number of bacteria in the treated samples was determined by the interaction between wattage and flow (p = 0.0056) and the interaction between wattage and salinity (p < 0.001). The bacterial count was also associated with residual chlorine contact time (p < 0.001). The results of this study, although preliminary and limited in their scale, offering a potential solution for disinfecting large volumes of seawater, which could make closed containment fish farming in the ocean viable for reducing bacterial transmission within a farm and to wild fish stocks.

PENGOLAHAN PRODUK DIVERSIFIKASI IKAN BAGI KELOMPOK WANITA NELAYAN MANDIRI DESA LAMUNDRE, KECAMATAN WATUBANGGA, KABUPATEN KOLAKA

Lamundre Village is one of the villages located in Watubangga District, Kolaka Regency which has promising marine natural resource potential, both in the form of aquaculture and capture fisheries. Various types of fish catch produced by the Lamundre Village Community include skipjack fish 30 tons/year and lure fish 70 tons/year. The catch is only dried and sold raw to the market. However, this potential can still be increased to increase the income of the Lamundre Village Community and increase the diversity of fishery products from the village. The Lamundre Village Independent Fishermen's Women's Group is a partner that operates in the fish processing sector. The main problem with partners is the low level of knowledge and skills of group members in processing fishery products. Therefore, it is very necessary to provide training and assistance to partners in processing fishery products. The fish processing products carried out are making fish balls and fish floss. Fish balls and fish floss are one of the fish processing activities that can increase the added value and shelf life of fish. The aim of this community service activity is to improve the skills and knowledge of the Independent Women Fishermen Group partners in processing fish independently into a product, namely fish balls and fish floss. This community service activity will be carried out in September 2024 in Lamundre Village, Watubangga District, Kolaka Regency. The activity method is carried out at several stages including the observation stage, preparation stage, training and mentoring stage, and evaluation stage. The result of this community service activity is an increase in partners' skills and knowledge in making fish balls and fish floss. Based on the results of the interview, the partner's skill level became 85% and the knowledge level increased 100% after the training. Partners are able to make fish balls and fish floss according to the materials provided. The fish balls and fish floss produced in this training activity do not smell or fishy, ​​this is because the process of making fish balls and fish floss complies with the quality standards for making fish balls and fish floss (SNI 7690.2013). This community service activity is able to improve the skills and knowledge of partners in making fish balls and fish floss.

RSNC-YOLO: A Deep-Learning-Based Method for Automatic Fine-Grained Tuna Recognition in Complex Environments

Tuna accounts for 20% of the output value of global marine capture fisheries, and it plays a crucial role in maintaining ecosystem stability, ensuring global food security, and supporting economic stability. However, improper management has led to significant overfishing, resulting in a sharp decline in tuna populations. For sustainable tuna fishing, it is essential to accurately identify the species of tuna caught and to count their numbers, as these data are the foundation for setting scientific catch quotas. The traditional manual identification method suffers from several limitations and is prone to errors during prolonged operations, especially due to factors like fatigue, high-intensity workloads, or adverse weather conditions, which ultimately compromise its accuracy. Furthermore, the lack of transparency in the manual process may lead to intentional underreporting, which undermines the integrity of fisheries’ data. In contrast, an intelligent, real-time identification system can reduce the need for human labor, assist in more accurate identification, and enhance transparency in fisheries’ management. This system not only provides reliable data for refined management but also enables fisheries’ authorities to dynamically adjust fishing strategies in real time, issue timely warnings when catch limits are approached or exceeded, and prevent overfishing, thus ultimately contributing to sustainable tuna management. In light of this need, this article proposes the RSNC-YOLO algorithm, an intelligent model designed for recognizing tuna in complex scenarios on fishing vessels. Based on YOLOv8s-seg, RSNC-YOLO integrates Reparameterized C3 (RepC3), Selective Channel Down-sampling (SCDown), a Normalization-based Attention Module (NAM), and C2f-DCNv3-DLKA modules. By utilizing a subset of images selected from the Fishnet Open Image Database, the model achieves a 2.7% improvement in mAP@0.5 and a 0.7% improvement in mAP@0.5:0.95. Additionally, the number of parameters is reduced by approximately 30%, and the model’s weight size is reduced by 9.6 MB, while maintaining an inference speed comparable to that of YOLOv8s-seg.

Optimism about Wild Fish Welfare

Optimism about Wild Fish Welfare

Implications of feed and seed costs in Asian seabass mariculture in the face of climate change

Mariculture, a sustainable and rapidly growing aquaculture sub-sector, meets global seafood demand while reducing strain on wild fish stocks and continues to expand worldwide. However, rising feed and seed costs pose significant challenges, overshadowing other farming expenses. Climate change exacerbates the profitability of sea cage farming, increasing volatility. The surge in fishmeal costs has a detrimental impact on operational expenditure (Opex) and continues to be a threat. Consequently, sea cage farming in India is at a critical juncture, needing a balance between technological advancements and stakeholders’ fiscal needs. In this context, this study examines peer-reviewed synthesized data by employing metrics to evaluate the implications of feed and seed costs in Asian Seabass (Lates calcarifer) sea cage farming over a 10-year horizon. The total sales revenue over the 10-year period was US $100,848, with a net profit of US $55,198.89. A 30% increase in feed and seed prices significantly altered the economic dynamics of the enterprise, leading to an 8.8 and 9.2% rise in the respective break-even points. There was also a significant effect on the Benefit–Cost Ratio (BCR), with a 30% increase in each factor resulting in a 10 and 18% change in the projected BCR, respectively. Therefore, the significance of feed and seed cost has been established, necessitating an inevitable shift from low-value fish to formulated feed adaption for sustainable mariculture development. The study suggests improvements to existing practices to maximize efficiency and minimize production costs.

Incorporating habitat use and life history to predict PCB residues in wild fish in an urban estuary

Owing to the heterogenous distribution of contaminated sediments in urban estuaries, contaminant residues, such as polychlorinated biphenyls (PCBs), in fish tissue can vary widely. To investigate the relationship between PCBs in fish tissue and heterogeneity of PCBs in sediment, we developed a geospatial Biota-Sediment Accumulation Factor (BSAF) model for an urban estuary. The model predicts whole fish total PCB residues at a scale of 0.1 km2 by incorporating sediment chemistry, fish home range, and habitat type. The model predicted concentrations from across the estuary ranging from 0 to 161,456 ng/g lipid. An estuary-wide (50+ km2) and a project-scale (1+ km2) field validation of the model demonstrated it produced values that were slightly skewed to low concentrations; performance improved with increased sediment data spatial coverage. We conclude this approach has potential for determining PCBs “hot spot,” estimating remediation project footprints, and evaluating potential remediation improvements to the quality of a fishery.

Realising Rights of Nature across and beneath the Southern Ocean

ABSTRACT If the philosophical, ecological, moral and ethical imperatives for Rights of Nature (RON) in the Antarctic can be argued to be clear, given the limitations and failures of contemporary instrumental environmental management, the modalities of operationalising and applying these to the Antarctic marine environment, commonly understood as the Southern Ocean, are not. Securing progressive environmental policies is very much harder in the marine environment than ashore, everywhere. Structural complications of the existing Antarctic regime structure and the historic and contemporary regional geopolitics add to the challenges in the Southern Ocean, beyond those posed by RON. Classical Antarctic framings cast the Southern Ocean as either the area south of the Antarctic Convergence or as merely the area south of 60° South Latitude. Neither suffices for the purposes of RON. Antarctic biota cross even the Antarctic Convergence. In doing so, they enter spaces subject to extra-Antarctic Treaty System (ATS) international legal regimes including Regional Fisheries Management Organisations abutting the ATS area and/or coastal state jurisdictions in the sub-Antarctic. They also penetrate deep below the levels of the ocean hitherto operationally managed by the ATS. Even ‘within’ the ATS geographical area, the deep seabed and particular taxa (cetaceans) are formally subject to other regimes. The area of relevance for RON is thus neither coterminous with the geographical area nor the jurisdictional competence of the ATS. The relevant geographical area is a ‘Greater Southern Ocean’. The politico-legal context across multiple regimes meaningful to RON is extraordinarily complex and multi-tiered. Advancing a RON discourse across this huge and complex field likely entails a fragmented engagement with discrete jurisdictional and institutional entities, albeit an engagement informed by a unitary and coherent understanding and purpose. Necessary as this is, it will be neither simple nor quick.

Species-specific trends of plutonium, radiocesium, and potassium-40 levels in three fish species of the Yenisei river (Siberia, Russia)

The Yenisei is the largest river in the Northern Hemisphere receiving controlled radioactive discharges from nuclear facilities. The paper presents a comparative study of temporal trends of artificial radionuclides plutonium (239,240Pu) and radiocesium (137Cs), and a natural isotope of the essential macronutrient potassium (40K) in samples of three commercial fish species (Northern pike, Baikal grayling, and Siberian dace) occupying different positions in a trophic network in the Yenisei River (Siberia, Russia). Samples of fish were caught in the Yenisei in 2011–2020 during a period of significant changes in controlled radioactive releases into the river. The study has shown no increase in plutonium concentration in fish samples within two years after the upsurge in controlled Pu discharge into the river (2018–2020). Average activity concentration of 239,240Pu (mBq∙kg−1 d.w., range, mean ± sd) in muscle of grayling (0.6–31.8, 10.9 ± 8.6) was higher (p < 0.01) than in muscle of dace (1.0–4.4, 2.4 ± 1.2) and pike (1.1–11, 3.8 ± 2.9). This can be attributed to the feeding of grayling on benthic invertebrates rich in Pu. The concentration of Pu tended to increase in muscle of pike with the increasing size of the fish. Average activity concentration of 137Cs (Bq∙kg−1 d.w., range, mean ± sd) in muscle of pike, a piscivorous fish (1.8–23.4, 7.7 ± 5.1), was significantly higher (p < 0.001) than the average activity concentration of 137Cs in muscle of dace (0.7–5.7, 2.7 ± 1.6) and grayling (1.3–7.2, 2.5 ± 1.7). A similar effect was revealed for 40K. This can be attributed to biomagnification of 137Cs and 40K in food chains. The results will draw a baseline for assessment of dose-dependent ecological risks for wild fish itself and fish consumers, add field-based facts to the fundamental knowledge of behavior of artificial radionuclides in freshwater food chains, and suggests a hypothesis for consequent experimental studies.

Environmental Impact and Sustainable Practices in Aquaculture: A Comprehensive Review

Aquaculture is the fastest-growing food production sector, now contributing more to global fish biomass than capture fisheries. While much of this expansion has occurred over the past 50 years, it has been accompanied by numerous environmental challenges, including aquatic pollution driven by urbanization, industrialisation, harbour dredging, sand filling, pesticide runoff from agricultural activities, and land-use conflicts between aquaculture, industry, and tourism. These environmental concerns have heightened the focus on sustainability, particularly in relation to ecological preservation. This review explores the various types of waste generated by industries, households, and other establishments that are discharged into aquatic ecosystems, examining their potential impacts on aquaculture. In addition, it evaluates mitigation strategies aimed at reducing or eliminating these environmental threats. Increasing attention has been placed on raising awareness of environmental issues and adopting sustainable practices to minimise aquaculture's ecological footprint. While environmental degradation was not viewed as a critical issue in the early stages of the industry's development, it has now become a central concern across academic, governmental, industrial, and market sectors.

Brazil and regional fisheries management organizations - What is at stake?

This study compares Brazil's participation in two distinct Regional Fisheries Management Organizations (ICCAT and CCAMLR) from the mid-2000s to 2019 to reveal how domestic governance issues such as substitutability and regulatory capture shape its international negotiation strategies. By contrasting Brazil's active fishing role in ICCAT with its conservation-focused stance in CCAMLR, the study demonstrates how varying domestic interests influence the country’s international engagement and sustainability commitments. By analyzing primary and secondary sources, including government documents, international submissions, and reports from non-governmental organizations, this study offers insights into the complexities of fisheries management in Brazil. The findings reveal that Brazil's contributions to and stance on RFMOs are significantly shaped by internal challenges, including governance instability and insufficient fisheries data, which hinder the formulation of coherent and effective international fishery policies. This study highlights the need for improved governance framework, data reliability, and a balanced approach to environmental and economic objectives to enhance the sustainability of fishery management practices. It provides critical perspectives for policymakers, stakeholders, and researchers concerned with advancing sustainable fisheries governance in Brazil and similar global contexts.

Gill-associated ammonia oxidizers are widespread in teleost fish.

Recent advances in sequencing methods have greatly expanded the knowledge of teleost-associated microorganisms. While fish-gut microbiomes are comparatively well studied, less attention has gone toward other, external organ-microbiome associations. Gills are particularly interesting to investigate due to their functions in gas exchange, osmoregulation, and nitrogen excretion. We recently discovered a branchial symbiosis between nitrogen-cycling bacteria and teleosts (zebrafish and carp), in which ammonia-oxidizing Nitrosomonas and denitrifying bacteria together convert toxic ammonia excreted by the fish into harmless dinitrogen (N2) gas. This symbiosis can function as a "natural biofilter" in fish gills and can potentially occur in all ammonotelic fish species, but it remains unknown how widespread this symbiosis is. In this study, we analyzed all publicly available gill microbiome data sets and checked for the presence of Nitrosomonas. We discovered that more than half of the described fish gill microbiomes contain 16S rRNA gene sequences of ammonia-oxidizing bacteria (AOB). The presence of gill-specific AOB was shown in both wild and aquacultured fish, as well as in marine and freshwater fish species. Based on these findings, we propose that ammonia oxidizers are widespread in teleost fish gills. These gill-associated AOB can significantly affect fish nitrogen excretion, and the widespread nature of this association suggests that the gill-associated AOB can have similar impacts on more fish species. Future research should address the contribution of these microorganisms to fish nitrogen metabolism and the fundamental characteristics of this novel symbiosis.IMPORTANCERecent advances in sequencing have increased our knowledge of teleost-associated microbiota, but the gill microbiome has received comparatively little attention. We recently discovered a consortium of nitrogen-cycling bacteria in the gills of common carp and zebrafish, which are able to convert (toxic) ammonia into harmless dinitrogen gas. These microorganisms thus function as a natural nitrogen biofilter. We analyzed all available gill microbiome data sets to determine how widespread gill-associated ammonia-oxidizing bacteria (AOB) are. More than half of the data sets contained AOB, representing both aquacultured and wild fish from freshwater and marine habitats. In total, 182 amplicon sequencing variants were obtained, of which 115 were found specifically in the gills and not the environmental microbiomes. As gill-associated AOB are apparently widespread in teleost fish, it is important to study their impact on host nitrogen excretion and the potential to reduce ammonia accumulation in (recirculating) aquaculture of relevant fish species.

Re-evaluation of certain aspects of the EFSA Scientific Opinion of April 2010 on risk assessment of parasites in fishery products, based on new scientific data. Part 2.

The objective of this opinion was to determine if any wild caught fish species, originating from specific fishing grounds and consumed in the EU/EFTA could be considered free of zoonotic parasites. In this Opinion the term 'fishery products' only refers to fresh finfish. As there are multiple fish species and numerous potential parasites, Anisakis sp. was used as an indicator of zoonotic parasites in marine areas. This parasite species is particularly suited as it is common in marine environments, capable of infecting multiple fish species and is the subject of the majority of published studies. On the rare occasion where Anisakis sp. data were not available, or all tests were negative, other parasites such as Contracaecum osculatum (s.l.) and/or Phocanema spp. were considered. In freshwater systems, all zoonotic parasites were investigated. Consumption, import and landing data were used to determine the most relevant fish species and, where possible, the source fishing areas were identified. The most commonly consumed wild caught fish species in the EU/EFTA include tuna, cod, Alaskan pollock, hake, herring, sardines, mackerel, trout and saithe. Although the majority of these fish are caught in the Atlantic Ocean, the Mediterranean and the Black Sea (37) as well as several areas in the Indian Ocean, imported fish may originate from any global fishing areas, with the exception of Antarctica. Based on the data, at least one zoonotic parasite has been reported in at least one fish species in each of the FAO marine fishing areas. Thus, due to relative low fish host specificity of the zoonotic parasites, the panel concluded that all wild caught fish species may be exposed to and infected with zoonotic parasites. The same applies to freshwater fishing areas, with many areas having multiple studies reporting the presence of zoonotic parasites in the wild caught fish species.

Seasonal and Interannual Salinity Variability on the Northeast U.S. Continental Shelf: Insights From Satellite Sea Surface Salinity and Implications for Stratification

AbstractThe Northeast U.S. continental shelf (NEUS) is a highly productive and economically important region that has undergone substantial changes in recent years. Warming exceeds the global average and several episodes of anomalously warm, sustained temperatures have had profound impacts on regional fisheries. A majority of recent research studies focused on the analysis of temperature; however, salinity can serve as a valuable tracer as well. With now more than a decade of remote‐sensing sea surface salinity data, we shed new light onto salinity variability in the region with focus on the Mid‐Atlantic Bight and assess its role for modulating stratification on the shelf using historical hydrographic data. Local river discharge drives decreasing salinities not only in spring and summer on the shelf but also in the Slope Sea. In spring, fresher water aids the build‐up of stratification and a low salinity surface layer extends to the shelf break above the pycnocline by the beginning of summer. An observed salinification in the fall is linked to offshore forcing over the slope associated with the presence of Warm Core Rings. Coherent low‐frequency salinity variability is found over the slope and shelf, highlighting that shelf conditions are significantly impacted by offshore variability. Conditions on the NEUS in 2015 were characterized by anomalously high salinities, associated with a northerly position of the Gulf Stream. A freshening between 2015 and 2021, is in agreement with increased river cumulative discharge as well as lower offshore salinities. Overall, salinity serves as a valuable additional tracer of these multi‐variate processes.