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Cardiac abnormalities may pose a threat to salmonid aquaculture due to their potential detrimental effect on fish health and welfare. The teleost heart is an extremely plastic organ with important morphological differences between wild and farmed fish that include ventricular shape, alignment of the bulbus arteriosus and epicardial fat deposition. However, little is known about how different factors and interactions among them may affect cardiac morphology of Atlantic salmon. To determine whether rearing temperature could induce cardiac malformations in large Tasmanian Atlantic salmon, we examined a range of cardiac morphology indicators and growth parameters in a population of 1-2 kg seawater salmon (n = 60 temperature-1 diet-1 ) exposed to control and elevated temperatures of 15 and 19°C, respectively, while fed one of two commercial feeds with different dietary energy levels. Most fish possessed conspicuous fat around the heart with a tendency towards a rounded ventricle and a more obtuse angle of the bulbus arteriosus. However, fish showed no significant differences in heart shape and bulbus alignment in relation to water temperature and dietary energy. These results suggest that cardiac morphology of large Atlantic salmon is unlikely to be affected by rearing temperature and dietary energy during the grow-out phase.

Fishmeal (FM) is the main protein source in fish feed. However, it is quite expensive due to its limited resources. Therefore, finding a dietary alternative to the FM to sustain fish production is crucial, and the current study was performed to assess the impact of poultry offal silage (POS) with or without betaine supplementation; as an effective and cheaper alternative to FM; on feed efficiency, growth performance, spleen morphology and intestinal morphometry of Nile tilapia (Oreochromis niloticus) fingerlings. Four dietary treatments were formulated: (1) FM based diet, (2) FM-B; FM diet +0.7% betaine, (3) POS diet and (4) POS-B; POS diet +0.7% betaine. Each dietary treatment consisted of three replicates (n = 10/replicate), and the experiment was continued for 16 weeks. By the end of the experiment, spleen and intestine specimens were collected from 15 fish (n = 5/replicate) for histopathological assessment. The results were statistically analysed using GLM procedures of SAS 9.4. Feed efficiency increased in both POS-B and FM-B groups (p = 0.01), while body weight and body weight gain showed only weak tendencies towards an increase (p = 0.10 and 0.12, respectively). The villi length was the highest in POS-B fed group (p

Installation of feral pig (Sus scrofa) exclusion fences to conserve and rehabilitate coastal floodplain habitat for fish production and water quality services remains untested. Twenty‐one floodplain and riverine wetlands in the Archer River catchment (north Queensland) were surveyed during postwet (June–August) and late‐dry season (November–December) in 2016, 2017, and 2018, using a fyke net soaked overnight (~14–15 hr) to test: (a) whether the fish assemblage are similar in wetlands with and without fences; and (b) whether specific environmental conditions influence fish composition between fenced and unfenced wetlands. A total of 6,353 fish representing twenty‐six species from 15 families were captured. There were no wetland differences in fish assemblages across seasons, years and for fenced and unfenced (PERMANOVA, Pseudo‐F, Fencing wetlands prevents pig access on tropical floodplains, which should be positive for fish. However, though many fish access (fenced and unfenced) wetlands during wet season connection, the seasonal effect of reduced water level conditions seems to be more overimprovised compared to whether fences are installed or not, as all wetlands supported few, or no fish species because they had dried completed regardless of whether fences were present or not.

Models are important tools to address sustainability challenges associated with developing aquaculture at farm, regional and global scales. Farm-scale models (FSMs), which are integrated mathematical models developed to simulate farm operations, can quantify energy, mass or economic input flows and predict a variety of outputs such as fish biomass, waste and by-products. The variety of farming systems, equations available to build the models, and objectives of applications and intended users has resulted in the publication of wide range of FSMs. We performed a narrative review of 36 fish FSMs published from 1985–2021 to address several questions: Can the main characteristics of these models be defined? How do the farming system studied and the objectives of the study influence model development? What are the main modelling techniques available to simulate the main processes of a fish farm, and what are their advantages and disadvantages? How can FSMs help address sustainability challenges of aquaculture? This review discusses advances, limitations and future lines of research related to FSMs to help select existing models, or develop new ones, that are suitable for their intended use and users. The article is structured according to the main steps of the modelling process: (i) definition of scope and objectives; (ii) process formulation and model selection at individual, cohort and farm levels; (iii) implementation and evaluation; and (iv) applications (e.g. precision fish farming, IMTA modelling, supporting spatial management, life cycle assessment). At each step, recommendations are provided and research needs are stated.

Intensive fish farming at high densities results in a wide range of adverse consequences on fish welfare, including pathogen spreading, stress and increased mortality rates. In this work, we have assessed whether the survival of Senegalese sole infected with the nervous necrosis virus (NNV), a pathogen responsible for severe disease outbreaks, is affected by rearing density. Based on the different fish ratios per surface area (g cm−2) and water volume (g L−1), our research showed an earlier mortality onset in the tanks containing NNV-infected fish reared at medium density (MD: 0.071 g cm−2/5 g L−1) and high density (HD: 0.142 g cm−2/10 g L−1), as well as higher cumulative mortality values. However, transcription analysis of hsp70, gr1 and pepck genes, well-known stress biomarkers, seems to indicate that none of the challenged fish were under high stress conditions. NNV load was slightly higher both in dead and in sampled fish from MD and HD groups, and especially in the rearing water from these groups, where peaks in mortality seemed to correlate with increasing NNV load in the water. In conclusion, our results suggest that rearing NNV-infected Senegalese sole at high densities resulted in an earlier mortality onset and higher cumulative values and viral load L. Vázquez-Salgado would like to thank Interreg VA Spain–Portugal cooperation Program (POCTEP) 2014-2020, 0474_BLUEBIOLAB project, co-funded by FEDER for her research contract SI

To make crucial prevention, reduce fish losses and minimize the economic damage of diseases on the fish farm owners, a rapid detection of fish pathogens is mandatory. In this study, a loop-mediated isothermal amplification assay combined with hydroxynaphthol blue dye (LAMP-HNB) was developed and used for the rapid detection of Aeromonas salmonicida that caused significant economic losses in fish farming. Firstly, a pair of outer and inner primers specific for conserved fragment of vapA gene in A. salmonicida were designed and synthesized. Secondly, by optimizing the reaction conditions including reaction temperature, time, Mg2+ concentration, dNTP concentration and primer ratio, a LAMP-HNB assay was successfully established for the detection of A. salmoncida. Thirdly, the assay showed good specificity with no false-positive and false-negative results, and good sensitivity with the detection limit of 3.077 × 10-6 ng/μl, which was 102 times more sensitive than the conventional PCR. Finally, the LAMP-HNB assay was validated by the fish samples inoculated with different concentrations of A. salmoncida. This is the first development of rapid visual detection of A. salmonicida based on LAMP-HNB assay, which has great application prospect and market for diagnostic testing, health certification and active surveillance programmers.

Tambaqui, a species native to the Amazon and Orinoco Basins and their tributaries, has a history marked by biological resilience that makes this species a model for studies focused on ecology, physiology, and fish farming. In addition, it is of economic interest, due to its favorable characteristics for production in farms and its unique flavor. As the tambaqui responds in a unique way to several environmental disturbances of natural origin, the species is often used in environmental studies. Some of these studies have been revisited in this review. We revised aspects related to its natural history, habitats and geographic distribution, physiological and biochemical adaptations, and zootechnical performance. The extraordinary adaptation of the tambaqui is the fast expansion of its lower lip when exposed to low oxygen availability that is improved simultaneously with other adjustments. The resilience of this species to significant alterations in water pH is also surprising, and is incomparable with that of other species, as only when it is exposed to pH 3.5, does the tambaqui begin to present physiological-biochemical disturbances. The analysis of the gene expression of tambaqui specimens under different experimental conditions has shed light on the adaptive mechanisms used by this unique Amazonian species. In this sense, this review sought to gather information regarding the tambaqui, and its many biological features employed to survive environmental challenges.

As aquaculture continues to grow and intensify, there is an increasing public concern over the welfare of farmed fish. Stress and production-related pathologies and repressed growth are examples of the challenges facing aquaculture, and their impacts could be minimised by effective identification of the early signs of impaired welfare. Many welfare monitoring methods have been recommended; however, continuous and reliable welfare monitoring in aquaculture is not yet widespread and commonplace. The aim of this scoping review was to present an overview of the most recent developments in fish welfare assessments with a specific focus on practical translation to the aquaculture industry. A keyword-based search was undertaken to identify peer-reviewed papers published between 2014 and 2020 in which a novel method with the potential to be used for the assessment of fish welfare in aquaculture was introduced. The results were sorted into two categories: non-invasive and invasive methods. All methods were assessed for their advantages and disadvantages, potential applicability to aquaculture. Invasive methods were also ranked on their degree of impact. It is concluded that increased interest into fish welfare, in combination with more intelligent modern technology, has resulted in the development of newer and more refined alternatives to traditional methods of welfare assessment such as behaviour monitoring by 2D cameras and plasma cortisol evaluation. Although, in many cases, more research is needed before these methods are suitable for widespread industry use, studies that focus on increasing the precision, automation and practical applicability of these methods are a promising avenue for future research.

High concentrations of environmental ammonia can cause reduced immunity and death in fish, causing enormous economic losses. Air‐breathing fish usually have a high ammonia tolerance and are very suitable for high‐density fish farming. However, research on the effects of environmental ammonia on air‐breathing fish immunity is lacking. Therefore, this study investigated the effects of environmental ammonia on the immunity of large‐scale loach (Paramisgurnus dabryanus) by exposing fish to 30 mmol/L NH4Cl solution and subsequently analyzing the changes in serum and liver immune indicators, including total protein, albumin, globulin, immunoglobulin (Ig) M, lysozyme, complement component (C) 3 and C4, heat shock protein (HSP) 70, HSP90, tumor necrosis factor (TNF)‐α, interleukin (IL)‐1β, IL‐6, and IL‐12. Results revealed that ammonia exposure significantly affected the total protein, albumin, globulin, IgM, complement C3 and C4, HSP70, HSP90, and inflammatory cytokine contents in the body, indicating that ammonia exposure induced a significant immune response and lowered bodily immunity. However, most of the immune indicators significantly decreased in the later stages of the experiment, suggesting a weakened immune response, which may be due to the species‐specific ammonia detoxification ability of large‐scale loach that reduces ammonia toxicity in the body.

Enteromyxum leei is a causative agent of enteromyxosis, with a wide range of marine fish hosts. Recently, massive morbidity and mortality were caused by E. leei infection in cultured olive flounders in Korea. To reveal a relationship between E. leei abundance in culture water and the occurrence of parasite infection in host fish, we used a quantitative PCR assay targeting the 28S rDNA of E. leei in three fish farms (two where enteromyxosis had occurred and one where it did not) from April to November 2018. The gene of E. leei was detected at levels greater than 10 cells/L in the culture water where enteromyxosis occurred from July to September. Furthermore, 2 months after the detection in the water, the parasite gene (with more than 5,000 cells per 100 mg) was detected in fish intestine samples. However, in the fish farms where enteromyxosis had not occurred, the E. leei gene was detected at

Some common practices in aquaculture, ornamental trade and fish facilities may disturb the behavioural repertoire of fish and its natural adaptive value, reducing welfare and impairing fish production. Hence, it is necessary to understand fish behaviour, as well as the factors affecting it, to improve the quality of fish's life under artificial environment. Here, we reviewed the behaviour of the angelfish Pterophyllum scalare, an Amazonian cichlid used worldwide both as an ornamental fish and as a fish model in scientific research. We characterized social, reproductive and feeding behaviour, as well as the amazing cognitive ability of the angelfish. In addition, we reviewed the effects of environmental enrichment and suggested some important variables that need to be considered for rearing P. scalare. In this review, we show for the first time a synthesis on behaviour and a best practice overview to improve the welfare of angelfish as a target species. Nonetheless, most topics reviewed fit a broader set of fish species, particularly ornamental ones. This synthesis can therefore open a path for further behavioural research applied to the welfare of angelfish and bring insights to other fish species.

Characterization of microbial assemblages via environmental DNA metabarcoding is increasingly being used in routine monitoring programs due to its sensitivity and cost-effectiveness. Several programs have been developed recently which infer functional profiles from 16S rRNA gene data using hidden-state prediction (HSP) algorithms. These might offer an economic and scalable alter-native to shotgun metagenomics. To date, HSP-based methods have seen limited use for benthic marine surveys and their performance in these environments remains unevaluated. In this study, 16S rRNA metabarcoding was applied to sediment samples collected at 0 and ≥ 1200 m from Norwegian salmon farms, and three metabolic inference approaches (PAPRICA, PICRUSt2 and TAX4FUN2) evaluated against metagenomics and environmental data. While metabarcoding and metagenomics recovered a comparable functional diversity, the taxonomic composition differed be-tween approaches, with genera richness up to 20× higher for metabarcoding. Comparisons between the sensitivity (highest true positive rates) and specificity (lowest true negative rates) of HSP-based programs in detecting functions found in metagenomics data ranged, respectively, from 0.52 and 0.60 to 0.76 and 0.79. However, little correlation was observed between the relative abundance of their specific functions. Functional beta-diversity of HSP-based data was strongly associated with that of metagenomics (r ≥ 0.86 for PAPRICA and TAX4FUN2) and responded similarly to the impact of fish farm activities. Our results demonstrate that although HSP-based metabarcoding approaches provide a slightly different functional profile than metagenomics, partly due to recovering a distinct community, they represent a cost-effective and valuable tool for characterizing and assessing the effects of fish farming on benthic ecosystems.

BACKGROUND Fish farming is one of the most productive economies in the world. One of the essential goals in fish production is to minimize processing costs while maintaining and increasing the vital functions, weight and immunity of fish. OBJECTIVE We conducted this study to explore nanoselenium (Nano-Se) particles in various feeding schemes. MATERIAL AND METHOD Nano-Se particles incorporated in the basal diet at (0.5 mg/kg diet), and the fish was divided into six groups after adaptation as the follows: The first group was feed daily with a diet containing Nano-Se (0.5 mg/kg diet); the second group was exposed to a feeding programme in which it has day feeding followed by day of starvation with a diet containing Nano-Se (0.5 mg/kg diet); the third group was day feeding followed by 2 days of starvation; the fourth group served as a negative control group in which this group was continuous feeding with a basal diet without Nano-Se; the fifth group was day feeding with the basal diet followed by a day of starvation; and the sixth group was day feeding with basal diet followed by 2 days of starvation. RESULT Our result revealed that Group 2 showed significant improvement in haematological parameters, red blood cells and haemoglobin with a substantial increase in total protein (p

Changes in biophysical conditions through time generate spatial and temporal variability in habitat quality across landscapes. For river ecosystems, researchers are increasingly able to characterize spatial and temporal patterns in habitat conditions, referred to as shifting habitat mosaics, yet rarely demonstrate how this translates into corresponding biological processes such as organism growth and production. We assessed spatial patterns and processes determining seasonal changes in juvenile Chinook Salmon Oncorhynchus tshawytscha size, growth and production over 30-40 km in two NE Oregon subbasins. We quantified seasonal patterns of growth by combining estimated emergence dates and body size distributions in July and September. We then used analysis of bioenergetics, empirical fish diets and spatial models incorporating temperature, habitat and population density to evaluate mechanisms driving spatiotemporal patterns of growth. Lastly, we quantified seasonal contributions to individual fish growth and to total production as a function of position within the stream network. Spatial heterogeneity in incubation temperatures corresponded to later estimated emergence timing with distance upstream in both subbasins. During spring, estimated growth rates decreased with distance upstream, and coupled with emergence patterns, resulted in pronounced longitudinal gradients in body size by July. During summer, spatial patterns of growth reversed, with greater diet ration sizes and growth efficiencies upstream than downstream. These opposing spatiotemporal patterns of emergence timing and seasonal growth rates produced longitudinal gradients in the proportion of fish growth achieved in spring versus summer, with up to 80% of an individual's growth occurring in spring at downstream sites but as low as 10% at upstream sites. Coupling longitudinal patterns of fish density and growth revealed that in one subbasin the majority (65%) of total production occurred in spring, while in the other, in which fish were concentrated in headwaters, the majority (60%) of production occurred in summer. While recent work has emphasized inter-annual shifts in fish production across large spatial scales, this study demonstrates that longitudinal gradients of fish growth and production can reverse across seasons, and reveals important contributions of warmer, downstream habitats to overall production that occurred during cooler times of the year.

The aquaculture industry is growing and includes the farming and breeding of more than 580 aquatic species worldwide. The rainbow trout (Oncorhynchus mykiss, Walbaum 1792) is the most commonly bred trout species in Hungary. As broodfish form the basis of most fish farms, investigation into tumours occurring in trout, although under-researched, has proven to be a valuable and necessary field of study. During our investigation, we examined a broodstock of 3- to 6-year-old rainbow trouts (800) affected with idiopathic intestinal tumours (3%) which had consequentially led to ileus (40%). While performing necropsy, initial pathological observations showed intussusceptions. Tumours were discovered upon opening the body cavity, as well as metastasis forming in the livers and in the vessels of the gills. Histopathological and immunohistochemical tests allowed us to identify the neoplasms. The primary adenocarcinoma was found to have been developed within the intestines of the fish. The tumour tissue broke through the basal membrane and infiltrated the propria, protruding asymmetrically into the lumen of the mid-intestines, causing it to narrow significantly. This subsequently led to passage disorders, invagination of the intestinal segment and finally the emaciation of the fish. Histopathological and immunohistochemical inspection of the tumour cells displayed a high mitotic index, confirming malignancy.

The long-term fish consumption rate (also referred to as the "usual fish consumption rate" [UFCR]) is a critical assumption in the derivation of human health remedial goals for contaminated sediments. At many sites, remedial goals are established using fish consumption rates based on information available from surveys of the general population or of specific highly exposed populations. To be protective of human health, remedial goals are often established using those high-end fish consumption rates. However, high-end fish consumption rates may overestimate the amount of fish that can be sustainably harvested and consumed and, thus, lead to remedial goals that may not be representative of long-term consumption from the contaminated portion of a water body. This paper presents a methodology to estimate the amount of edible fish that can be harvested sustainably from a contaminated sediment site. The methodology requires 1) estimating the total fish productivity of the area of contaminated sediments, 2) estimating the portion of total productivity that can be harvested sustainably, and 3) determining the portion of the sustainable harvest that is edible fish tissue. Estimates of total fish production rate (TFPR) and the proportion of such harvest that can be harvested sustainably rely primarily on available compilations of TFPR and harvest measurements across a range of water bodies throughout the world. Estimates of the fraction of whole fresh fish that is consumed rely on information available from the United States Environmental Protection Agency (USEPA). The methodology is used to develop sustainable UFCRs for 4 hypothetical water bodies with distinct characteristics and to compare the UFCRs to commonly used default fish consumption rates. Estimates of sustainable production provide risk managers valuable perspective about the benefits realized by cleanup of contaminated sediment sites. Integr Environ Assess Manag 2021;17:584-596. © 2020 SETAC.

Aquaculture policy often promotes production of low-trophic level species for sustainable industry growth. Yet, the application of the trophic level concept to aquaculture is complex, and its value for assessing sustainability is further complicated by continual reformulation of feeds. The majority of fed farmed fish and invertebrate species are produced using human-made compound feeds that can differ markedly from the diet of the same species in the wild and continue to change in composition. Using data on aquaculture feeds, we show that technical advances have substantially decreased the mean effective trophic level of farmed species, such as salmon (mean TL = 3.48 to 2.42) and tilapia (2.32 to 2.06), from 1995 to 2015. As farmed species diverge in effective trophic level from their wild counterparts, they are coalescing at a similar effective trophic level due to standardisation of feeds. This pattern blurs the interpretation of trophic level in aquaculture because it can no longer be viewed as a trait of the farmed species, but rather is a dynamic feature of the production system. Guidance based on wild trophic position or historical resource use is therefore misleading. Effective aquaculture policy needs to avoid overly simplistic sustainability indicators such as trophic level. Instead, employing empirically derived metrics based on the specific farmed properties of species groups, management techniques and advances in feed formulation will be crucial for achieving truly sustainable options for farmed seafood.

Monitoring variations in proteins involved in metabolic processes, oxidative stress responses, cell signalling and protein homeostasis is a powerful tool for developing hypotheses of how environmental variations affect marine organisms' physiology and biology. According to the oxygen- and capacity-limited thermal tolerance hypothesis, thermal acclimation mechanisms such as adjusting the activities of enzymes of intermediary metabolism and of antioxidant defence mechanisms, inducing heat shock proteins (Hsps) or activating mitogen-activated protein kinases may all shift tolerance windows. Few studies have, however, investigated the molecular, biochemical and organismal responses by fishes to seasonal temperature variations in the field to link these to laboratory findings. Investigation of the impacts of global warming on fishes farmed offsore, in the open sea, can provide a stepping stone towards understanding effects on wild populations because they experience similar environmental fluctuations. Over the last 30 years, farming of the gilthead sea bream Sparus aurata (Linnaeus 1758) has become widespread along the Mediterranean coastline, rendering this species a useful case study. Based on available information, the prevailing seasonal temperature variations expose the species to the upper and lower limits of its thermal range. Evidence for this includes oxygen restriction, reduced feeding, reduced responsiveness to environmental stimuli, plus a range of molecular and biochemical indicators that change across the thermal range. Additionally, close relationships between biochemical pathways and seasonal patterns of metabolism indicate a connection between energy demand and metabolic processes on the one hand, and cellular stress responses such as oxidative stress, inflammation and autophagy on the other. Understanding physiological responses to temperature fluctuations in fishes farmed offshore can provide crucial background information for the conservation and successful management of aquaculture resources in the face of global change.

A total of 122 Patinga specimens were collected from fish farms (P1, P2 and P3), and only those from fish farm P1 were shown to be infected with Echinorhynchus gomesi. In addition, fish in this study were shown to have diets that consisted of 21 different food items, and Notodiaptomus sp. (Copepoda: Calanoida) was identified as a potential intermediate host for E. gomesi.

Non-destructive sampling methods offer practical advantages to detection and monitoring of viral pathogens in economically important farmed fish and broodstock. Here, we investigated whether blood, mucus and fin can be used as non-lethal sample sources for detection of scale drop disease virus (SDDV) in farmed Asian sea bass, Lates calcarifer. Detection of SDDV was performed in parallel from three non-destructive and seven destructive sample types, collected from both clinically sick fish and subclinical fish obtained from an affected farm. The results showed that SDDV was detectable in all 10 sample types with the percentage ranging from 20% to 100%. Blood was the best non-destructive sample source exhibited by the fact that it yielded 100% SDDV-positive tests from both sick (n = 12, 95% CI: 69.9-99.2) and clinically healthy fish (n = 4, 95% CI: 39.6%-97.4%) and is considered a "sterile" sample. This study also revealed concurrent infection of SDDV and two ectoparasites Lernanthropus sp. and Diplectanum sp., in all affected fish (n = 8, 95% CI: 46.7-99.3) during the disease outbreak. These ectoparasites also tested positive for SDDV by PCR, indicating that they were potential sample sources for PCR-based detection of SDDV and possibly other viruses infecting Asian sea bass.

Mass mortality has occurred among cultured Nile tilapia, Oreochromis niloticus, on fish farms in Manzala, Dakahlia province, Egypt, in the summer season, 2019. Moribund fish were reported with deep ulcers, septicaemic lesions and sampled for bacterial isolation. In this study, most isolates were subjected to bacteriological examination, antibiotic sensitivity test, 16S rRNA gene sequencing and histopathological examination. Following isolate identification, intraperitoneal challenge of Nile tilapia with a bacterial suspension 2 × 106 CFU/ml was performed. Samples from liver, spleen and kidney were collected for histological and biochemical analysis. The results showed a high similarity (99%) to Photobacterium damselae strains using phylogenetic analysis of 16S rRNA. P. damselae exhibited resistance to amoxicillin and erythromycin, as well it was highly sensitive to chloramphenicol and doxycycline. Moreover, haemorrhage, oedema, hemosiderosis and melanomacrophage activation in the liver and head kidney of infected fish were detected by light and electron microscopy. Also, significant higher levels of CAT and SOD in the spleen and head kidney, as well as the serum levels of NO were observed in experimentally challenged O. niloticus, compared to the control fish. Our data identified P. damselae for the first time from infected Nile tilapia, describing its sensitivity to a variety of antibiotics, histopathological alterations and oxidative stress impact, and it could be useful indicators for understanding P. damselae pathogenesis, which might provide a preventive efficacy for P. damselae.

An understanding of behaviour is used in zoos, laboratories and agriculture to reduce stressful aspects of the captive environment for animals. While fish are one of the most cultivated of all vertebrate groups, incorporating their behaviour into production management has proved elusive. Here, we evaluate the current evidence base relating to use of (i) innate behaviours of fish and (ii) their ability to learn new behaviours via human-mediated training or through social learning, in fish farms. Studies that tested habituation and conditioning (training) as a tool to improve welfare demonstrate positive effects for improving fish welfare and coping capacity. However, methods solely reliant on innate behavioural responses to stimuli will always be imperfect, due to variation in individual responses which are often context dependent. To date, there has been no successful demonstration of social learning as a tool for aquaculture. While many experimental scale studies report promising results, few have translated to commercial scale, highlighting a mismatch between theoretical and practical use and cautions against extrapolation of results from small-scale studies to commercial situations. While some promising evidence exists that fish behaviour can be integrated into farm management, logistical and scale-related hurdles must be overcome before this can occur. We conclude that fish behaviour is an additional and currently under-researched resource that could be integrated into farm practices to improve production and welfare in industrial aquaculture.

Introduction Infectious pancreatic necrosis virus belongs to the genus Aquabirnavirus and family Birnaviridae. By VP2 gene similarity, aquatic birnavirus is clustered into seven genogroups. The aim of this study was to genetically analyse IPN viruses occurring on Polish fish farms. Materials and methods Samples from freshwater fish mostly from 2012 to 2013 and from northern Poland were examined for the presence of IPN virus using isolation on cell cultures, real-time RT-PCR and RT-PCR. Fragments of 1,377 and 1,079 bp of the VP2 and VP5 genes, respectively, were sequenced, and the results were assembled into one consensus and analysed by Geneious software. The same VP2 gene region was compared and a phylogenetic tree generated by the neighbour-joining method and MEGA6 software. Results All tested Polish isolates belonged to genogroup 5, like other European Spajurup isolates. Conclusion Our findings prove that there is only one IPN virus genogroup in Poland. Polish isolates show close relationships with each other. There is a close relationship between Polish isolates and isolates from Turkey, Spain and Iran. Isolate 57 is a separate branch related to isolates from the United States and Taiwan. This points to the likelihood of past virus introduction via import of stock from those countries.

BACKGROUND An innovative pilot-plant packaging was developed and evaluated for applying oregano essential oil (OEO) vapours in conditions of high vacuum for exploring the antimicrobial effect of essential oil vapours applied immediately before packaging of fish fillets. Farmed sea bream (Sparus aurata) fresh fillets have been used as a model for validating this new technology. These fillets, as a refrigerated product under modified atmosphere packaging (MAP), have a relatively short shelf life (12-14 days) mainly due to the fast microbial growth. The effects of conventional OEO dippings [pretreatment dipping (0.1% of OEO) of whole fish (T1) and filleted sea bream (T2)] were compared with the OEO application in vapour phase (67 μL L-1 ) under vacuum (5-10 hPa) immediately before MAP fillet packaging (T3). RESULTS T3/T2 samples showed the lowest microbial growth after 28 days at 4 °C, with loads up to 1/2.6 log units for Enterobacteria/lactic acid bacteria compared to untreated samples. The initial trimethylamine nitrogen (TMA-N) content (2.6 mg kg-1 ) increased in T1 and T2/T3 samples by 9.6 and 6/7 units, respectively, after 28 days. Quality Index Method (QIM) better reflected the fish fillets shelf life than texture and colour measurements. The shelf life of T3/T2 samples was established in at least 28 days (4 °C), while the QIM threshold (6) was exceeded after 7/21 days in untreated/T1 fillets. CONCLUSION The fish shelf life was extended with vapour OEO treatment using this new technology, similarly to OEO dipping treatment, according to QIM, corroborated by the microbial quality and TMA-N contents. © 2020 Society of Chemical Industry.

Blooms of toxin-producing cyanobacteria have been more frequent and lasting because of the eutrophication of freshwater ecosystems, including those used for aquaculture. The aim of the present study was to investigate the effects of chronic exposure to a saxitoxin-producing strain of Raphidiopsis (Cylindrospermopsis) raciborskii on the performance of Nile tilapia (Oreochromis niloticus) fingerlings over a 60-d period. The fingerlings were cultivated under the following conditions: 1) water without cyanobacterium (WATER), 2) R. raciborskii in ASM-1 culture medium (CYANO), and 3) ASM-1 culture medium without cyanobacterium (ASM). Exposure to the CYANO treatment led to a significant increase in the mortality rate (p 0.05). Saxitoxin toxicity was dependent on the weight of the fingerling (p

The health and welfare of farmed fish are often regarded with less concern than for other production animals. This review compares the Norwegian legal health and welfare frameworks for broiler chickens and farmed salmon, with the aim of improving regulations for salmon farming in Norway. Highlighting differences in laws, regulations and governmental organisation are also highly relevant in general, especially in developing welfare regulations for farmed fish in other countries. Norwegian chicken farmers must comply with two main laws, the Norwegian Animal Welfare Act and the Food Act, governed by the same ministry and governmental agency. The salmon farmers must in addition relate to the Aquaculture Act, different ministries and several agencies with different objectives. Compared to the regulation of chicken farming, the regulation of salmon farming is more complex, has potentially conflicting aims and uses less positive welfare phrasings. Thus, the regulation may be perceived as focusing on profitability over welfare. Despite having many similar paragraphs to regulation for chicken farming, salmon farming regulation is less strict in the daily securing of animals and recordings of mortality. There is no specified slaughterhouse control of high‐density productions, as there is for broiler chickens. There are also differences in the mandatory welfare courses, one being that infection prevention is a stated topic for chickens. The Norwegian Animal Welfare Act has no possibility of dispensation, meaning exceptions, and treats fish and other animals equally. Future regulatory frameworks for farmed fish production should avoid unintended downgrading of fish health and welfare.

Summary This study is an initial description and discussion of the kidney and liver microbial communities of five common fish species sampled from four sites along the Eastern Mediterranean Sea shoreline. The goals of the present study were to establish a baseline dataset of microbial communities associated with the tissues of wild marine fish, in order to examine species‐specific microbial characteristics and to screen for candidate pathogens. This issue is especially relevant due to the development of mariculture farms and the possible transmission of pathogens from wild to farmed fish and vice versa. Although fish were apparently healthy, 16S rRNA NGS screening identified three potential fish bacterial pathogens: Photobacterium damselae, Vibrio harveyi and Streptococcus iniae. Based on the distribution patterns and relative abundance, 16 samples were classified as potential pathogenic bacteria‐infected samples (PPBIS). Hence, PPBIS prevalence was significantly higher in kidneys than in liver samples and variation was found between the fish species. Significant differences were observed between fish species, organs and sites, indicating the importance of the environmental conditions on the fish microbiome. We applied a consistent sampling and analytical method for monitoring in long‐term surveys which may be incorporated within other marine fish pathogens surveys around the world., This study is an initial description and discussion of the kidney and liver microbial communities of five common fish species sampled from four sites along the Eastern Mediterranean Sea shoreline. The goals of the present study were to establish a baseline dataset of microbial communities associated with the tissues of wild marine fish, in order to examine species‐specific microbial characteristics and to screen for candidate pathogens.

Gill parasitic infections challenge farming of rainbow trout (Oncorhynchus mykiss, Walbaum) in freshwater facilities. Apart from flagellates (Ichthyobodo, (Pinto) and ciliates (Ichthyophthirius (Fouquet), Ambiphrya (Raabe), Apiosoma (Blanchard), Trichodinella (Sramek-Husek) and Trichodina (Ehrenberg)), we have shown that amoebae are prevalent in Danish trout farms. Gills were isolated from farmed rainbow trout in six fish farms (conventional and organic earth pond and recirculated systems) and placed on non-nutrient agar (NNA) moistened with modified Neff's amoeba saline (AS) (15°C). Gill amoebae from all examined fish colonized the agar and were identified based on morphological criteria showing species within the genera Trinema (Dujardin) (family Trinematidae), Vannella (Bovee) (family Vannellidae). In addition, hartmannellid amoebae were recorded. We established a monoculture of Vannella sp., confirmed the genus identity by PCR and sequencing and performed an in vitro determination of antiparasitic effects (dose-response studies) of various compounds including sodium chloride (NaCl), hydrogen peroxide, peracetic acid, formalin, aqueous garlic and oregano extracts and a Pseudomonas H6 surfactant. All amoebae were killed in concentrations of 16.90 mg/ml (garlic), 17.90 mg/ml (oregano), NaCl (7.5 mg/ml), hydrogen peroxide (100 µg/ml), peracetic acid (0.03 µg/ml), formaldehyde (25 µg/ml) and the Pseudomonas H6 surfactant (250 µg/ml).

This paper examined climate change adaptation strategies in fish farming and the effect of such methods on the profit of fish farmers in the Niger Delta region of Nigeria, Africa’s most populous country. Using cross‐sectional data obtained from 420 fish farmers from the region and applying multivariate probit and instrumental variable regressions, the study found that fish farmers have adopted a broad range of strategies to address climate risk and that these have significantly increased farmers’ profit. Our findings indicated important relationships between certain farm, socio‐economic and institutional characteristics and the adaptation actions. The study provides useful insight into factors that potentially encourage the adoption of livelihood‐enhancing climate risk adaptation strategies by fish farmers in the Niger Delta region and similar contexts.

The COVID-19 pandemic has had a negative impact on the global economy, with Bangladesh as a developing country exhibiting greater vulnerability. This pandemic has negatively affected the livelihoods and food security of the nation. Baor (oxbow lake) fisheries communities also were significantly affected during the pandemic, in terms of incomes, food security, health conditions, etc. Fishers have had to stop harvesting, or lower the quantity, of fishes, the sale of which was the main income source of the baor fishers' community because of reduced consumer demands during the lockdown conditions. The supply chains of fishes and fish culture inputs were also disrupted because of a lack of needed transportation, thereby hindering the availability of this convenient protein source from the fish. All these factors negatively impacted the incomes of the people dependent on this important fishery. If appropriate measures are applied to overcome these various difficulties, the baor fisheries may again contribute significantly to the livelihoods and food security of the population in the southwestern part of Bangladesh.

We present a GIS-based approach to the delineation of areas that have different levels of suitability for use as tilapia cage culture sites the Kenyan part of Lake Victoria, Africa. The study area was 4,100 km2. The method uses high-resolution bathymetric data, newly collected water quality data from all major fishing grounds and cage culture sites, and existing spatial information from previous studies. The parameters considered are water depth, water temperature, levels of dissolved oxygen, chlorophyll-a concentrations, distances to the lake shoreline and proximity to other constraints on cage culture development. The results indicated that the area most suitable for fish cages comprised about 362 km2, or approximately 9% of the total area; the remaining 91% (i.e., 3,737 km2) was found to be unsuitable for tilapia cage culture. We conclude that the successful implementation of this approach would need stakeholder involvement in the validation and approval of potential sites, and in the incorporation of lake zoning into spatial planning policy and the regulations that support sustainable use while minimising resource use conflicts. The results of this study have broader applicability to the whole of Lake Victoria, other African Great Lakes, and any lakes in the world where tilapia cage culture already occurs or may occur in the future.