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Due to the socioeconomic importance of salmon farming in the North Atlantic and the economic impact of sea lice in this industry, there is high demand for novel pest control methods. One such method is the use of cleaner fish to remove the lice from the salmon. A cleaner fish that has recently gained in popularity due to its ability to work in cold water, is the lumpfish (Cyclopterus lumpus). This fish varies in efficiency, but when mortality is low and cleaning optimal, the fish are successful in keeping parasite burdens low. However, there is some concern for the welfare of lumpfish in the industry, because mortality is often high. This is sometimes attributed to inadequate feeding and shelter. Here we compare growth, body condition, and fin health of fish reared for four weeks in a crossed treatment design crossing shelter availability (shelter vs none) and feed delivery method (manual meal time feeds and continuous automated feeding). In terms of weight gain, shelter availability interacted with feeding method, with fish that had access to shelters and were fed using automated feeders gaining less weight than other fish. Fin health was not affected, but body condition was lowered both by access to shelter and being fed continuously. The results indicate a need to carefully consider how feeding method and shelter use is combined, both in cages and during rearing on land. [ABSTRACT FROM AUTHOR]

The current study evaluated the effects of two different fractions derived from the methanolic extraction of the red seaweed Gracilaria sp. supplemented in European seabass (Dicentrarchus labrax) diets. With that purpose, three experimental diets were prepared: a basal diet (control), a control supplemented with the methanolic extract (GE, 0.5% diet) and a control supplemented with the insoluble residue of the GE extraction (GR, 4.5%). Seabass with an average initial weight of 16.5 ± 0.6 g were fed the experimental diets for 42 days, and the following parameters were evaluated: growth indicators, digestive enzyme activities, immune and oxidative stress responses, fillet pH and color (L*, a*, and b* values), and skin color. The dietary supplementation of GE or GR had no effect on growth performance, digestive enzyme activities, fillet pH, and color. Skin color was significantly lighter (L*) in fish-fed GE (83.9 ± 1.9) and GR (84.3 ± 2.3) diets when compared with the control group (81.9 ± 3.8). The dietary treatments did not affect the oxidative stress biomarkers. Alternative complement pathway (ACH50) was significantly higher in fish-fed GE diet (168.2 ± 13.4 EU mL−1) than in the control diet (113.1 ± 31.4 EU mL−1). No dietary effect was observed on peroxidase and lysozyme activities. The current study indicates that dietary supplementation of Gracilaria sp. methanolic extracts may have little influence on the innate immune system and skin color in seabass. [ABSTRACT FROM AUTHOR]

Environmental enrichment involves increasing the complexity of a fish's environment in order to improve welfare. Researchers are legally obliged to consider the welfare of laboratory animals and poor welfare may result in less robust data in experimental science. Laboratory zebrafish Danio rerio are usually kept in bare aquaria for ease of husbandry and, despite being a well‐studied species, little is known about how laboratory housing affects their welfare. This study shows that environmental enrichment, in the form of the addition of gravel substratum and plants into the tank, affects survivorship, growth and behaviour in laboratory‐maintained D. rerio. Larvae reared in enriched tanks had significantly higher survivorship compared with larvae reared in bare tanks. Effects of the tank conditions on growth were more variable. Females from enriched tanks had a higher body condition than females maintained in bare tanks, but intriguingly this was not the case for males, where the only difference was a more variable body condition in males maintained in bare tanks. Sex ratio in the rearing tanks did not differ between treatments. Resource monopolisation was higher for fish in enriched tanks than for those in bare tanks. Fish from enriched tanks displayed lower levels of behaviours associated with anxiety compared with fish from bare tanks when placed into a novel environment. Thus, this study demonstrates differences in welfare for D. rerio maintained under different environmental conditions with enhancements in welfare more commonly associated with tank enrichment. [ABSTRACT FROM AUTHOR]

Abstract Upon the demand of a private fish farmer, this study was applied to assess the influence of electro-fishing adopted by some Egyptian fish farmers on the fish welfare and quality. Therefore, a total of 60 Nile tilapia (Oreochromis niloticus) were sampled; from which 30 were stunned by electrofishing and the remainders by conventional fishing. Biochemical analysis (oxidative stress and energy status), meat quality based on total bacterial count (TBC) and pathological alterations were assessed. Biochemical analysis in both liver and muscle tissue showed that electro-stunned fish exhibited low oxidative stress and high energy status. Meat of electro-stunned fish showed an acceptable limit of TBC (Max. limit 107) while the histopathological examination revealed various tissue reactions. These were in the form of congestion in branchial, hepatoportal, brain and splenic blood vessels with edema in brain and pericardium. In addition, there was mild inflammatory reaction together with the presence of eosinophilic granular cells and perivascular melanophores aggregation in both branchial and muscular tissue. As a consequence of this work, we recommend the use of electrofishing method in Egypt after modifying the current tool by reducing applied voltage. Further studies and more optimization are needed to cover both fish farmers and animal welfare issues, and take in consideration the human safety precautions. [ABSTRACT FROM AUTHOR]

The attempt to replace marine-derived ingredients for aquafeed formulation with plant-derived ones has met some limitations due to their negative side effects on many fish species. In this context, finding new, sustainable ingredients able to promote fish welfare is currently under exploration. In the present study, poultry by-products and Hermetia illucens meal were used to replace the vegetable protein fraction in diets totally deprived of fish meal intended for gilthead seabream (Sparus aurata). After a 12-week feeding trial, a multidisciplinary approach including histological, molecular, and spectroscopic techniques was adopted to investigate intestine and liver responses to the different dietary formulations. Regardless of the alternative ingredient used, the reduction in dietary vegetable proteins resulted in a lower incidence of intestine histological alterations and inflammatory responses. In addition, the dietary inclusion of insect meal positively affected the reduction in the molecular inflammatory markers analyzed. Spectroscopic analyses showed that poultry by-product meal improved lipid absorption in the intestine, while insect meal induced increased liver lipid deposition in fish. The results obtained demonstrated that both poultry by-products and H. illucens meal can successfully be used to replace plant-derived ingredients in diets for gilthead seabream, promoting healthy aquaculture.

Thanks to its small size, external fertilization and fecundity, over the past four decades, zebrafish (Danio rerio) has become the dominant fish model species in biological and biomedical research. Multiple lines of evidence, however, suggest that the reliance on only a handful of genetic model organisms is problematic, as their unique evolutionary histories makes them less than ideal to study biological questions unrelated to their historically contingent adaptations. Therefore, a need has emerged to develop novel model species, better suited for studying particular problems. The paradise fish (Macropodus opercularis) has a much more complex behavioral repertoire than zebrafish and has been a favored model animal in ethological research during the last decades of the previous century. We believe that with currently available, easily adaptable genetic toolkits, this species could be easily developed into a popular model of behavioral genetics. Despite its earlier popularity, however, the description of a detailed housing and husbandry protocol for this species is still missing from scientific literature. We present here a detailed description of how to raise and breed paradise fish successfully under laboratory conditions, and also discuss some of the challenges we faced while creating a stable breeding population for this species in our facility.

In the last three decades, the aquaculture sector has experienced a 527% growth, producing 82 million tons for a first sale value estimated at 250 billion USD. Infectious diseases caused by bacteria, viruses, or parasites are the major causes of mortality and economic losses in commercial aquaculture. Some pathologies, especially those of bacterial origin, can be treated with commercially available drugs, while others are poorly managed. In fact, despite having been recognized as a useful preventive measure, no effective vaccination against many economically relevant diseases exist yet, such as for viral and parasitic infections. The objective of the present review is to provide the reader with an updated perspective on the most significant and innovative vaccine research on three key aquaculture commodities. European sea bass (Dicentrarchus labrax), Nile tilapia (Oreochromis niloticus), and Atlantic salmon (Salmo salar) were chosen because of their economic relevance, geographical distinctiveness, and representativeness of different culture systems. Scientific papers about vaccines against bacterial, viral, and parasitic diseases will be objectively presented; their results critically discussed and compared; and suggestions for future directions given.

One of the main constraints in aquaculture production is farmed fish vulnerability to diseases due to husbandry practices or external factors like pollution, climate changes, or even the alterations in the dynamic of product transactions in this industry. It is though important to better understand and characterize the intervenients in the process of a disease outbreak as these lead to huge economical losses in aquaculture industries. High-throughput technologies like proteomics can be an important characterization tool especially in pathogen identification and the virulence mechanisms related to host-pathogen interactions on disease research and diagnostics that will help to control, prevent, and treat diseases in farmed fish. Proteomics important role is also maximized by its holistic approach to understanding pathogenesis processes and fish responses to external factors like stress or temperature making it one of the most promising tools for fish pathology research.

Welfare in animal husbandry includes considerations of biology, ethics, ecology, law and economics. These diverse aspects must be translated into common quantifiable parameters and applicable methods to objectively assess welfare in animals. To assist this process in the field of aquaculture, where such methods are largely missing, we developed a model to assess fish welfare. A network of information was created to link needs, i.e., fundamental requirements for welfare, with parameters, i.e., quantifiable aspects of welfare. From this ontology, 80 parameters that are relevant for welfare, have practicable assessment methods and deliver reliable results were selected and incorporated into a model. The model, named MyFishCheck, allows the evaluation of welfare in five distinct modules: farm management, water quality, fish group behaviour, fish external and fish internal appearance, thereby yielding five individual grades categorising welfare ranging from critical, to poor, to acceptable, and good. To facilitate the use of the model, a software application was written. With its adaptability to different fish species, farming systems, regulations and purposes as well as its user-friendly digital version, MyFishCheck is a next step towards improved fish welfare assessment and provides a basis for ongoing positive developments for the industry, the farmers and the fish.

The objective of this study was to examine the effects of CO 2 , total ammonia nitrogen (TAN: nitrogen bound as either NH 3 or NH 4 +) and pH on the growth and survival of juvenile lumpfish in a two-month growth study. The results demonstrate the complex interactions of these water quality variables. The specific growth rate (SGR) of the lumpfish was progressively reduced with increasing [CO 2 ] concentration above 5–10 mg·L−1. However, growth may be reduced at even lower [CO 2 ] and the results provide no clear safe limits under which the growth of lumpfish is unaffected by CO 2 concentration. At the lowest [CO 2 ] tested (8 mg·L−1) the SGR was reduced compared with controls. Moreover, in treatments where the [CO 2 ] concentration increased to 8 mg·L−1 as pH was artificially reduced, the SGR was similarly reduced. These results indicate that lumpfish juveniles are very sensitive to increased [CO 2 ] concentration in water. The SGR of the lumpfish was progressively reduced as the NH 4 + concentration increased while maintaining the [NH 3 ] constant (70–80 μg·l−1). However, in these treatments the [CO 2 ] also increased to 8–10 mg·L−1 due to changes in pH and this likely contributed to reduced growth. Moreover, due to nitrification in the rearing systems, the nitrite concentration also increased to critical levels (1.5–4.2 mg·L−1) that could affect growth. Therefore, the results do not provide clear evidence for effects of increased NH 4 + on the growth of lumpfish. Taken together, the results of the experiments show that lumpfish are sensitive to perturbations in water quality and provide a benchmark for operational welfare indicators in lumpfish aquaculture. • The effects of CO 2 , total ammonia nitrogen (TAN) and pH on the growth and survival of lumpfish was studied. • pH in the range 7.2–7.8 does not directly affect the growth of lumpfish. • Growth is reduced at CO 2 concentration from 8 mg·l−1. • NH 3 at relatively low concentrations (0.08 mg·l−1) has negative effect on lumpfish growth. • Lumpfish are sensitive to perturbations in water quality. [ABSTRACT FROM AUTHOR]

While most animals have received increasing attention for their welfare, consideration for fish welfare has started more recently, particularly since the recognition that fish have emotions and complex cognitive abilities. Housing conditions in fish farms do not always meet fish ethological requirements as these conditions lack sufficient sensory and cognitive stimulations. An approach to address this issue involves enriching the rearing environment by including social, food, physical, or cognitive stimuli. Cognitive enrichment (CE) is a recent but promising concept to improve fish welfare by manipulating the predictability and controllability of their environment. It relies not only on the ability of fish to predict positive and negative events but also on their ability to perform and succeed in operant conditioning. In our present review, we identified four categories of CE: (i) feeding predictability, (ii) predictability of a negative event, (iii) operant conditioning through self-feeders, and (iv) learning experiences. Existing CEs were reviewed for their effects on behaviour, brain, zootechnical performances, and welfare in terms of physiological stress or physical integrity in the aquarium and farmed teleost fish. The review highlights unbalanced categories and the lack of adequate multidisciplinary analyses to assess the effects of these categories on fish welfare. Providing free access to self-feeders seems to be a good strategy, given its positive effects on zootechnical and physiological parameters. Other categories showed contradictory and species-dependent results; hence, further studies are required to confirm the benefits of CE on fish welfare. Finally, further investigations should also validate current CE systems and assess other strategies that may trigger positive emotions in fish. • Fish have the cognitive abilities required to use cognitive enrichments properly. • Promising effects of feeding predictability as a cognitive enrichment strategy on fish welfare. • Cognitive enrichments still deserve further consideration, namely validate the current existing strategies and more comprehensive analyses on fish welfare. • Cognitive enrichment needs to be designed according to the ecology of the fish species. • Cognitive enrichments must contain an appropriate level of stimulations to ensure positive effects on fish welfare: nor too low to avoid boredom, nor too high to avoid chronic stress and frustration. [ABSTRACT FROM AUTHOR]

This article aims to use contemporary (terrestrial) animal welfare science as a lens to evaluate the state of knowledge concerning welfare in fish species, focusing on farmed fishes. We take advantage of the vast expertise—including previous pitfalls and accomplishments—in the investigation of welfare in terrestrial vertebrates, borrowing questions and methodologies from terrestrial animal welfare science in order to (1) better understand the challenges and opportunities in the study of welfare in fish species, and (2) propose strategies for filling knowledge gaps.

The salmon louse (Lepeophtheirus salmonis) causes problems in Atlantic salmon (Salmo salar) aquaculture in the Northern Hemisphere, because infestations can result in both a loss of production and in fish mortality. Several types of treatment have been used to control louse infestations, but these have seen varying success. The aim of this review is to examine the efficacy and safety of commonly used treatments (chemical, biological, mechanical, and preventive measures) as documented in peer-reviewed publications. Efficacy is assessed in relation to a reduction in numbers of lice, and safety is assessed as a lack of negative treatment-associated effects on fish health and welfare (Atlantic salmon and/or cleaner fish). Most chemical treatments showed decreasing efficacy over time, together with the use of increasing concentrations as a result of the development of resistance to the treatments by lice. The need for a restrictive use of pesticides to preserve treatment efficacy has been emphasized. The use of cleaner fish was suggested to be effective, with few or no negative effects towards Atlantic salmon. The use of cleaner fish would be preferable to chemical treatment if the farmed fish health and welfare criteria are met. At present, the number of peer-reviewed publications relating to other forms of treatment and prevention are sparse.

Transport procedures usually cause fish stress. The purpose of this study was to investigate the effect of transport stress on blood biochemical profiles, oxidative stress biomarkers, and hepatic heat shock proteins (HSPs) of channel catfish (Ictalurus punctatus). Fish (body weight 55.57 ± 5.13 g) were randomly distributed to two groups, the control, and the treatment. The control group was kept under the normal culture conditions. The treatment group was exposed to the process of transport (3.5 h). Fish samples were collected before transport, after packing and at 0, 1, 6, 24, 72, and 168 h after transport, respectively. Transport caused a significant increase in the serum concentrations of cortisol, glucose, total cholesterol, and triglyceride, as well as, the activity of aspartate aminotransferase at 0 and 1 h after transport compared with non-transported fish and the basal level. Blood total protein content significantly declined in the transported fish. Total antioxidant capacity (T-AOC), malonaldehyde content, and the activities of both glutathione peroxidase and catalase significantly increased in fish within 6 h after transport. The transported fish exhibited a significant higher level in either the concentration of nitric oxide or the mRNA expressions of both hepatic HSP70 and HSP90. It is concluded that transport triggers stress response of I. punctatus, leading to the obvious change in antioxidant capacity. I. punctatus need to be more care after transport to recover from transport stress.

Environmental enrichment is widely used to improve welfare and behavioral performance of animal species. It ensures housing of laboratory animals in environments with space and complexity that enable the expression of their normal behavioral repertoire. Auditory enrichment by exposure to classical music decreases abnormal behaviors and endocrine stress responses in humans, non-humans primates, and rodents. However, little is known about the role of auditory enrichment in laboratory zebrafish. Given the growing importance of zebrafish for neuroscience research, such studies become critical. To examine whether auditory enrichment by classical music can affect fish behavior and physiology, we exposed adult zebrafish to 2 h of Vivaldi’s music (65–75 dB) twice daily, for 15 days. Overall, zebrafish exposed to such auditory stimuli were less anxious in the novel tank test and less active, calmer in the light-dark test, also affecting zebrafish physiological (immune) biomarkers, decreasing peripheral levels of pro-inflammatory cytokines and increasing the activity of some CNS genes, without overt effects on whole-body cortisol levels. In summary, we report that twice-daily exposure to continuous musical sounds may provide benefits over the ongoing 50–55 dB background noise of equipment in the laboratory setting. Overall, our results support utilizing auditory enrichment in laboratory zebrafish to reduce stress and improve welfare in this experimental aquatic organism.

Due to the socioeconomic importance of salmon farming in the North Atlantic and the economic impact of sea lice in this industry, there is high demand for novel pest control methods. One such method is the use of cleaner fish to remove the lice from the salmon. A cleaner fish that has recently gained in popularity due to its ability to work in cold water, is the lumpfish (Cyclopterus lumpus). This fish varies in efficiency, but when mortality is low and cleaning optimal, the fish are successful in keeping parasite burdens low. However, there is some concern for the welfare of lumpfish in the industry, because mortality is often high. This is sometimes attributed to inadequate feeding and shelter. Here we compare growth, body condition, and fin health of fish reared for four weeks in a crossed treatment design crossing shelter availability (shelter vs none) and feed delivery method (manual meal time feeds and continuous automated feeding). In terms of weight gain, shelter availability interacted with feeding method, with fish that had access to shelters and were fed using automated feeders gaining less weight than other fish. Fin health was not affected, but body condition was lowered both by access to shelter and being fed continuously. The results indicate a need to carefully consider how feeding method and shelter use is combined, both in cages and during rearing on land.

The present study aims at identifying the lowest number of fish (European seabass) that could be used for monitoring and/or experimental purposes in small-scale fish facilities by quantifying the effect that the number of individuals has on the Shannon entropy (SE) of the trajectory followed by the shoal’s centroid. Two different experiments were performed: (i) one starting with 50 fish and decreasing to 25, 13, and 1 fish, and (ii) a second experiment starting with one fish, adding one new fish per day during 5 days, ending up with five fish in the tank. The fish were recorded for 1h daily, during which time a stochastic event (a hit in the tank) was introduced. The SE values were calculated from the images corresponding to three arbitrary basal (shoaling) periods of 3.5 min prior to the event, and to the 3.5 min period immediately after the event (schooling response). Taking both experiments together, the coefficient of variation (CV) of the SE among measurements was largest for one fish systems (CV 37.12 and 17.94% for the daily average basal and response SE, respectively) and decreased concomitantly with the number of fish (CV 8.6–10% for the basal SE of 2 to 5 fish systems and 5.86, 2.69, and 2.31% for the basal SE of 13, 25, and 50 fish, respectively). The SE of the systems kept a power relationship with the number of fish (basal: R2= 0.93 and response: R2= 0.92). Thus, 5–13 individuals should be the lowest number for a compromise between acceptable variability (

The aims of this study were to determine the influence of the factors affecting fin damage under different rainbow trout production systems and to compare the findings with the known experimental reports. The study was based on a questionnaire that included information about the main factors i.e. oxygen level in exit water, water temperature, stocking density, daily feed ration, number of meals and grading frequency on seven rainbow trout farms. Standard multiple regression analysis, based on a previously published fi n damage dataset, was used to assess the relationship between the level of fin damage per fin and the factors. Daily feed ration received the strongest weight in the model for the caudal, anal and both pectoral fins, whereas number of meals received the strongest weight in the model for both pelvic fins. Grading frequency received the strongest weight only in the dorsal fin model. Lower levels of daily feed ration and number of meals combined with higher water temperature increased the level of fin damage, whereas stocking density had no effect. The results conform to the experimental research on fin damage in rainbow trout. The research model contributes to the overall assessment of fish welfare and the regression analysis used in this study could be used on rainbow trout farms to evaluate the effect of the main factors on the level of fin damage.

Cardiomyopathy syndrome (CMS) poses a significant threat to farmed Atlantic salmon ( Salmo salar ), leading to high mortality rates during the seawater phase. Given that controlled experimental challenge trials with PMCV do not reproduce the mortality observed in severe field outbreaks of CMS, field trials on natural CMS outbreaks are warranted. This field study explored the impact of a clinical nutrition intervention, specifically a diet enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on a severe CMS outbreak in a commercial sea farm. CMS was diagnosed in a single sea cage with high mortality rates. Histopathological analysis, RT-qPCR in situ hybridization for virus detection, and fatty acid composition analysis were used to monitor the impact of disease and the inclusion of EPA and DHA in heart tissue. Following the implementation of clinical nutrition, a decline in mortality rates, regression of CMS-associated changes, and a significant reduction in piscine myocarditis virus (PMCV) RNA load were observed within the salmon population. Fatty acid composition analysis of heart samples demonstrated increased levels of EPA and DHA, reinforcing the association between dietary factors, viral load dynamics, and overall fish health. Although further validation is needed in future studies, as field trials may not be sufficient to establish causation, our results indicate that optimizing the EPA + DHA levels may prove beneficial in severe CMS outbreaks.

In Brazil, pre-slaughter immersion in ice is used in most fish slaughterhouses. We aimed to study the parameters for electrical stunning in pacu ( Piaractus mesopotamicus ) as a way to reduce animal suffering during slaughter and the stunning effects on meat pH and rigor mortis . We evaluated 70 fish, divided into two groups. In group G205, fish were stunned with 205 Volts (V), 50 Hz, duty cycle of 70% and 1.3 Amp (A) applied for 45 s; in group G400, fish were stunned with 400 V, 30 Hz, duty cycle of 30% and 0.9 A, for 30 s. Electrical stunning was applied using a backpack electrofisher (Smith Root LR-24) in a plastic box with 80 L of fresh water. We determined the unconsciousness time through behavioral evaluation. Immediately after checking the return of consciousness, all fish were placed in a plastic box with 35 L of fresh water and 200 mg L −1 of benzocaine before bleeding. After slaughter, the first 10 fish from each group were identified and placed in refrigerated plastic boxes with ice for measurements of pH in the epaxial muscle as well as the rigor mortis index (RMI) at 0, 3, 6, 24, 72, 120 and 168 h after bleeding. All fish were effectively stunned. When the current was applied, we observed that all fish lost behavioral responses and reflexes instantly: fish stopped swimming, lost equilibrium, did not respond to painful stimuli, ceased opercular movements and did not show vestibulo-ocular reflex. The unconsciousness time was significantly higher in the G205 treatment, equal to 61.7 ± 13.4 s ( P  < .01), in relation to G400 50.1 ± 9.6 s, possibly related to longer exposure to the electric current and the longer duty cycle. The pH values (median, min-max) immediately after slaughter were: 6.80 (6.70–6.90) for G205 and 6.75 (6.60–6.80) for G400 ( P  > .05). All fish reached maximum rigor mortis (RMI = 100%) within 6 h post mortem . There was no external damage, vertebral fracture, hemorrhages or blood spotting in the meat. Electrical stunning in pacu seems to be feasible through the G205 parameters, due to the unconsciousness period longer than 1 min, which may allow minimum time period to proceed bleeding without suffering. More research is needed to provide best strategies to the fish industry, so that fish regulations regarding humane slaughter may be implemented. [ABSTRACT FROM AUTHOR]

European fish farming drives the development of sustainable marine fish feed where marine ingredients are replaced by alternatives such as plant meals and vegetable oils. A new scenario emerges where noncurrent and/or new contaminants enter into the fish food chain as potential food safety and/or welfare concerns. Novel analytical methodologies must be developed to assess the large variety of contaminants from different families in feed ingredients, feeds based on these ingredients and fish farmed on the novel feeds. Of the novel contaminants identified in feed ingredients and feeds, the pesticides, such as chlorpyrifos‐methyl, pirimiphos‐methyl, boscalid and azoxystrobin, and the mycotoxins, such as deoxynivalenol and fumonisins (B1 + B2 + B3), were detected. Polyaromatic hydrocarbons, especially those with ≤4 ring, were found in all samples. Information of the transfer of contaminants from feed to public foodstuffs is essential for an appropriate human risk assessment of feed contaminants as well as for the harmonization of legislation of contaminants throughout the aquaculture production chain. However, the pesticides and mycotoxins found in feed were not detected in fish fillet, and hence, no transfer factor could be established. As a result, no apparent risk seems to be associated with these contaminants in fish fillets at the current background exposure levels by feeds. Recent achievements in aquafeeds with marine fish oil and fish meal below 10% represented food safety risks considerably reduced. The use of plant‐based diets implies that POPs were not found. Polar pesticides and mycotoxins were not transferred to edible fillets while PAHs were widely found in both feed and fillets. [ABSTRACT FROM AUTHOR]

Transport procedures usually cause fish stress. The purpose of this study was to investigate the effect of transport stress on blood biochemical profiles, oxidative stress biomarkers, and hepatic heat shock proteins (HSPs) of channel catfish (Ictalurus punctatus). Fish (body weight 55.57 ± 5.13 g) were randomly distributed to two groups, the control, and the treatment. The control group was kept under the normal culture conditions. The treatment group was exposed to the process of transport (3.5 h). Fish samples were collected before transport, after packing and at 0, 1, 6, 24, 72, and 168 h after transport, respectively. Transport caused a significant increase in the serum concentrations of cortisol, glucose, total cholesterol, and triglyceride, as well as, the activity of aspartate aminotransferase at 0 and 1 h after transport compared with non-transported fish and the basal level. Blood total protein content significantly declined in the transported fish. Total antioxidant capacity (T-AOC), malonaldehyde content, and the activities of both glutathione peroxidase and catalase significantly increased in fish within 6 h after transport. The transported fish exhibited a significant higher level in either the concentration of nitric oxide or the mRNA expressions of both hepatic HSP70 and HSP90. It is concluded that transport triggers stress response of I. punctatus , leading to the obvious change in antioxidant capacity. I. punctatus need to be more care after transport to recover from transport stress. [ABSTRACT FROM AUTHOR]

Peracetic acid (PAA) is considered an eco-friendly alternative to other antimicrobial agents of common use in aquaculture. The literature suggests that fish can habituate to PAA exposure based on a reduction of the fish corticosteroid response to PAA administration after repeated exposures. If that is true, PAA would also be a good option from the point of view of fish physiology. However, stronger evidence is needed to confirm that the use of PAA is welfare-friendly to fish. Besides habituation, other hypothetical factors such as desensitization, physiological exhaustion or PAA-mediated endocrine disruption could potentially explain the reduction in the corticosteroid response after repeated/prolonged PAA exposure. In this study, rainbow trout that had been exposed to PAA for several weeks were challenged with a secondary chasing stressor: fish were pursued with a dipnet for 1 min and their acute response was evaluated by measuring plasma cortisol, plasma glucose, plasma lactate and brain serotonergic activity. All fish were equally able to mount a normal physiological stress response to the secondary stressor independent of previous exposure to PAA. This suggests that the decrease in the cortisol response after repeated exposure to PAA, as seen in previous studies, is a true habituation to PAA administration, which supports the use of PAA as a welfare-friendly antimicrobial agent in aquaculture. [ABSTRACT FROM AUTHOR]

Environmental enrichment is widely used to improve welfare and behavioral performance of animal species. It ensures housing of laboratory animals in environments with space and complexity that enable the expression of their normal behavioral repertoire. Auditory enrichment by exposure to classical music decreases abnormal behaviors and endocrine stress responses in humans, non-humans primates, and rodents. However, little is known about the role of auditory enrichment in laboratory zebrafish. Given the growing importance of zebrafish for neuroscience research, such studies become critical. To examine whether auditory enrichment by classical music can affect fish behavior and physiology, we exposed adult zebrafish to 2 h of Vivaldi's music (65-75 dB) twice daily, for 15 days. Overall, zebrafish exposed to such auditory stimuli were less anxious in the novel tank test and less active, calmer in the light-dark test, also affecting zebrafish physiological (immune) biomarkers, decreasing peripheral levels of pro-inflammatory cytokines and increasing the activity of some CNS genes, without overt effects on whole-body cortisol levels. In summary, we report that twice-daily exposure to continuous musical sounds may provide benefits over the ongoing 50-55 dB background noise of equipment in the laboratory setting. Overall, our results support utilizing auditory enrichment in laboratory zebrafish to reduce stress and improve welfare in this experimental aquatic organism. [ABSTRACT FROM AUTHOR]

Cognitive stimulation has been shown to be rewarding and capable of eliciting positive emotions in several species. In contrast to the abundant learning and exploration opportunities available in nature, captive environments can be under-stimulating—with the potential to induce anhedonia and reduce welfare. Zebrafish are now a popular scientific model, in part because of their high cognitive function and sensitivity to environmental manipulations, yet little is known regarding their response to free-choice opportunities to explore. To begin to understand the effect that cognitive enrichment may have on zebrafish behaviour, we housed zebrafish within six tanks (10 fish/110 L tank) for nine months and then removed a divider to expose 10 cm of additional novel tank space. We measured free-choice exploratory behaviour (latency and number of inspections), as well as anxiety/fear (bottom-dwelling) and social behaviour (agonistic behaviour, group cohesion and coordination). We collected video data on each of four days: the day before (baseline), the day of, the day after, and two weeks after divider removal. Using multilevel models, we found that after the divider was removed, zebrafish moved into the novel space on average within 9.7 ± 7.6 s (mean ± SD), and the number of inspections increased on each day observed ( p  < 0.003). We found no evidence of bottom-dwelling ( p  > 0.73), indicating that the manipulation was not likely to have induced a negative emotional response. Furthermore, the opportunity to explore altered social behaviour: reducing agonistic behaviour ( p  = 0.02), and increasing shoal cohesion ( p  = 0.04) and coordination ( p  = 0.04) for up to a day relative to baseline. In light of the fact that their natural habitats would normally include such information-gain opportunities, these results indicate that free-choice exploration may be beneficial for zebrafish welfare. This study thus adds to the growing body of literature on the role cognitive stimulation plays in welfare and indicates that zebrafish are good candidates for further cognitive enrichment research. [ABSTRACT FROM AUTHOR]

The present study aims at identifying the lowest number of fish (European seabass) that could be used for monitoring and/or experimental purposes in small-scale fish facilities by quantifying the effect that the number of individuals has on the Shannon entropy (SE) of the trajectory followed by the shoal's centroid. Two different experiments were performed: (i) one starting with 50 fish and decreasing to 25, 13, and 1 fish, and (ii) a second experiment starting with one fish, adding one new fish per day during 5 days, ending up with five fish in the tank. The fish were recorded for 1h daily, during which time a stochastic event (a hit in the tank) was introduced. The SE values were calculated from the images corresponding to three arbitrary basal (shoaling) periods of 3.5 min prior to the event, and to the 3.5 min period immediately after the event (schooling response). Taking both experiments together, the coefficient of variation (CV) of the SE among measurements was largest for one fish systems (CV 37.12 and 17.94% for the daily average basal and response SE, respectively) and decreased concomitantly with the number of fish (CV 8.6-10% for the basal SE of 2 to 5 fish systems and 5.86, 2.69, and 2.31% for the basal SE of 13, 25, and 50 fish, respectively). The SE of the systems kept a power relationship with the number of fish (basal: R² = 0.93 and response: R² = 0.92). Thus, 5-13 individuals should be the lowest number for a compromise between acceptable variability (<10%) in the data and reduction in the number of fish. We believe this to be the first scientific work made to estimate the minimum number of individuals to be used in subsequent experimental (including behavioral) studies using shoaling fish species that reaches a compromise between the reduction in number demanded by animal welfare guidelines and a low variability in the fish system's response. [ABSTRACT FROM AUTHOR]

Due to the socioeconomic importance of salmon farming in the North Atlantic and the economic impact of sea lice in this industry, there is high demand for novel pest control methods. One such method is the use of cleaner fish to remove the lice from the salmon. A cleaner fish that has recently gained in popularity due to its ability to work in cold water, is the lumpfish (Cyclopterus lumpus). This fish varies in efficiency, but when mortality is low and cleaning optimal, the fish are successful in keeping parasite burdens low. However, there is some concern for the welfare of lumpfish in the industry, because mortality is often high. This is sometimes attributed to inadequate feeding and shelter. Here we compare growth, body condition, and fin health of fish reared for four weeks in a crossed treatment design crossing shelter availability (shelter vs none) and feed delivery method (manual meal time feeds and continuous automated feeding). In terms of weight gain, shelter availability interacted with feeding method, with fish that had access to shelters and were fed using automated feeders gaining less weight than other fish. Fin health was not affected, but body condition was lowered both by access to shelter and being fed continuously. The results indicate a need to carefully consider how feeding method and shelter use is combined, both in cages and during rearing on land. [ABSTRACT FROM AUTHOR]

The effects of tank color on the growth, stress responses, and skin color of snakeskin gourami (Trichogaster pectoralis) were investigated in this study. Fish with initial body weights of 5.03±0.00 g were reared in five experimental tank colors (white, red, green, blue, and black) for 8 weeks. Each tank color was tested in triplicate with an initial stocking density of 15 fish per tank. Fish were fed with commercial sinking pellets at 4% of the average body weight per day. Growth performance, feed utilization efficiency, stress indicators (hematocrit, blood glucose, plasma cortisol levels), and skin color parameters were investigated. The fish reared in blue tanks had a significantly higher average final body weight (9.73 ± 0.14 g) and significantly lower average feed conversion ratio (3.42 ± 0.12) than the fish reared in black tanks (P < 0.05). The fish reared in black tanks exhibited higher average hematocrit (36.63 ± 1.11%), blood glucose (48.33 ± 1.45 mg dL−1), and plasma cortisol (9.00 ± 0.56 μg dL−1) levels than those reared in the other tank colors. However, the blood glucose levels in only the fish reared in black tanks were significantly higher than those in the fish reared in the other tank colors. The fish skin color ranged from very pale (high skin lightness) in the white tanks to very dark (low skin lightness) in the black tanks, and 80% of the variation in skin lightness were explained by the tank lightness. The use of a blue tank resulted in normal skin color; hence, blue tanks will not affect the customer acceptance of the fish. Our study revealed that blue is the most appropriate tank color for culturing snakeskin gourami. [ABSTRACT FROM AUTHOR]

Understanding dissolved O 2 flux in marine cages, and how individual fish respond to and experience such variation, is critical to optimizing growth and production performance of farmed salmon. We used a high resolution environmental monitoring system to create a 3-dimensional map of a commercial marine cage with respect to salinity, temperature and dissolved O 2 through time, while also tracking the oxygen experience of 4 individually tagged Atlantic salmon. Despite all of the dissolved O 2 measurements at the reference site being physiologically suitable for maximum growth, 1 in 4 of the recordings collected within the cage were below dissolved O 2 levels known to reduce feed intake and growth. Recorded dissolved O 2 in the cage ranged from 26 to 90% saturation with a high degree of vertical, horizontal and temporal variation. Poorest dissolved O 2 conditions consistently occurred at night in the central and down-current cage positions. Dissolved O 2 levels experienced by individual fish ranged from 30 to 90% saturation, with variation within 5 minute intervals as large as 32 percentage points. These results expand the current body of knowledge on environmental variability in marine cages, and provide valuable insights to aid farm managers in focusing mitigation and monitoring efforts when and where they are most needed. [ABSTRACT FROM AUTHOR]

Tench production is limited in traditional and low intensity cultures. However, its demand is increasing and makes necessary the evaluation of physiological parameters that could affect tench welfare under intensive conditions. This study analyses the growth performance and related indices, hematological and immunological parameters as well as hormone profile and electrolytes in plasma, in fish under three different culture systems: extensive (E), with initial density of 0.07 kg/m 3 , no control of environmental parameters and natural feeding; semi-intensive (SI), with initial density of 0.42 kg/m 3 , partial control of temperature and supplementation of artificial food; and intensive (I), with initial density of 2.5 kg/m 3 , total control of photo- and thermo-period and exclusive artificial diet. Results showed that variables such as weight, length, density increase and specific growth rate (SGR) were higher in I. Higher hepatosomatic index were found in I and SI. In addition, E and SI cultures, which kept natural conditions, achieved greater gonadal increase in detriment of somatic growth. On the other hand, the analysis of hormones and electrolytes, hematological and immunological parameters did not reveal a disturbed immune function in I compared to SI and E. Thus, the general activation of the nonspecific immune system and the mobilization of energy reserves associated to gonadal maturation in fishes from S-I and E systems could be related to an adaptive, non-pathological, response to the natural environmental changes, resulting in reduction of productivity. With all in mind, it can be concluded that adequate artificial feeding and control of the environmental parameters can improve tench productivity by intensive systems without major perturbations of its welfare. [ABSTRACT FROM AUTHOR]

This study evaluated whether anesthesia with essential oil (EO) of Lippia alba (300 mg L-1 for 4 min) prior to electronarcosis (128 V m-1 × 300 Hz for 5 s) or hypothermia (ice/water slurry) could delay fish spoilage during chilled storage of whole fish. Silver catfish (Rhamdia quelen) were subjected to two different pre-stunning treatments (water or anesthesia with EO of L. alba) followed by two different stunning procedures (hypothermia or electrical stunning), yielding four groups (n = 32/group): water (control) + hypothermia, water (control) + electrical stunning, EO of L. alba + hypothermia, and EO of L. alba + electrical stunning. After stunning, fish were slaughtered by percussion and stored in ice. Preslaughter anesthesia with the EO of L. alba extended fish shelf life by delaying the loss of freshness (nucleotide degradation), growth of Enterobacteriaceae, and fish deterioration (sensory evaluation). Such preservative effect was most remarkable for fish that were subsequently submitted to electrical stunning, as they had the lowest demerit scores and greatest shelf life in the sensory evaluation. Our results showed that preslaughter anesthesia with EO of L. alba followed by electrical stunning can delay the loss of freshness and extend fish shelf life during chilled storage. [ABSTRACT FROM AUTHOR]

The present study investigates the suitability of a machine vision-based method to detect deviations in the Shannon entropy (SE) of a European seabass (Dicentrarchus labrax) biological system fed with different selenium:mercury (Se:Hg) molar ratios. Four groups of fish were fed during 14 days with commercial feed (control) and with the same feed spiked with 0.5, 5 and 10 mg of MeHg per kg, giving Se:Hg molar ratios of 29.5 (control-C1); 6.6, 0.8 and 0.4 (C2, C3 and C4). The basal SE of C1 and C2 (Se:Hg > 1) tended to increase during the experimental period, while that of C3 and C4 (Se:Hg < 1) tended to decrease. In addition, the differences in the SE of the four systems in response to a stochastic event minus that of the respective basal states were less pronounced in the systems fed with Se:Hg molar ratios lower than one (C3 and C4). These results indicate that the SE may be a suitable indicator for the prediction of seafood safety and fish health (i.e., the Se:Hg molar ratio and not the Hg concentration alone) prior to the displaying of pathological symptoms. We hope that this work can serve as a first step for further investigations to confirm and validate the present results prior to their potential implementation in practical settings. [ABSTRACT FROM AUTHOR]

Atlantic salmon ( Salmo salar L.) post-smolt were reared at six different water CO 2 partial pressures (0.6 control, 2.6, 5.5, 8.0, 10.4 and 11.6 mm Hg) in duplicate 500 L tanks for 12 weeks in 34‰ sea water at 10 °C. Weight samplings divided the experiment into four periods (Periods I–IV). Plasma chloride concentration decreased linearly with increasing CO 2 partial pressure in the water and the changes lasted during the four periods (p < 0.05). During Period I and II, polynomial models described the significant relationship between PCO 2 and specific growth rate (p < 0.05). For both these periods, SGR declined between 8 and 10 mm Hg. No significant relationship between PCO 2 and SGR was found during period III (p > 0.05), however during period IV SGR decreased linearly as a function of PCO 2 in the range 0.6–12 mm Hg (p < 0.05). Condition factor decreased linearly with increasing CO 2 concentration on day 19, 36, 65 and 77 (p < 0.05), representing all four periods. Nephrocalcinosis was not observed in the control group, in the low group or in the medium group (medians in the range 0.6–5.5 mm Hg, which corresponds to 2–15 mg L − 1 ) at the end of the experiment. At the three highest PCO 2 levels (medians in the range 8.0–11.6 mm Hg or about 21–30 mg L − 1 ), 9 of 26 fish (34%) developed nephrocalcinosis (p < 0.05). [ABSTRACT FROM AUTHOR]

Participatory management is widely recognised as a working method of paramount importance, based on the principles of knowledge sharing, accountability and legitimacy. Hence, it is broadly considered suitable for addressing issues related to the sustainable development of the seafood industry, and specifically, of the aquaculture system. A survey focused on the current EU regulatory framework was carried out to elicit stakeholders’ preferences, knowledge and experience on key issues for the development of organic aquaculture, supported by science-based regulations. The survey was completed by 65 stakeholders belonging to several categories, and it was supported by the implementation of the Analytic Hierarchy Process method. Stakeholders’ preferences were elicited on organic production methods and control systems, the quality of the environment and organic products, fish health and welfare. The views expressed by the participants revealed both competence and awareness, despite the complexity of the subject. Several ideas and useful suggestions emerged regarding unresolved technical issues. In addition, the need for a targeted communication strategy on the quality of organic aquaculture products and the necessity of fostering European/national programs to support the production and marketing of organic aquaculture products were highlighted. [ABSTRACT FROM AUTHOR]

Despite generations of rearing in a laboratory environment, zebrafish (Danio rerio) retain innate preferences for environmental features that mimic their natural habitat (e.g. plants and gravel), but the effects of such preferred housing conditions on agonism are poorly understood. In this study, we worked with > 450 fish in 41 tanks to test two competing hypotheses about body size variation within shoals (a possible proxy for dominance hierarchy strength) and agonistic behaviour: A) the provision of preferred resources increases agonism (relative to levels in empty, barren tanks), possibly due to resource guarding behaviour, and B) barren housing conditions increase agonism (relative to levels in tanks containing preferred resources), possibly because subordinates are less able to hide from dominant fish. In Experiment 1, groups of 11–13 fish were housed for ∼ 1 year in 7 tanks in each of 3 treatments: empty lab-typical tanks, larger empty plastic tanks, and larger "well-resourced" plastic tanks containing preferred resources (gravel and artificial plants). Similarly, in Experiment 2, groups were housed in 5 tanks in each of 4 cross-factored treatments: empty glass aquaria, empty plastic tanks, well-resourced glass aquaria, and well-resourced plastic tanks. Live observations of agonistic behaviours and measures of body size variation (coefficient of variation for standard length and condition factor) were compared between treatments (using GLMs). In Experiment 1, empty lab-typical tanks exhibited significantly more agonistic behaviours than the other two treatment groups, which were not significantly different from each other. In Experiment 2, we found a significant interactive effect of housing treatment and tank material on agonism, where agonistic behaviours occurred most often in empty glass aquaria, possibly due to mirror-like reflections on glass walls. We therefore suggest that reflective surfaces in zebrafish housing systems should be minimized or visually disruptive resources like plants should be added to reduce agonism. Together both experiments also indicate that we need not be hesitant about adding preferred resources to captive zebrafishes' housing environments, since they likely do not exacerbate agonism (and indeed may even reduce it). We also found two unexpected results: in Experiment 1, shoals exhibiting increased agonism had significantly lower coefficients of variation in standard length and in Experiment 2, fish in barren tanks grew significantly longer than those housed with preferred resources. Possible growth-related hypotheses are discussed and we suggest that high coefficients of variation in body size should not be used to infer high levels of agonism in zebrafish shoals. • In otherwise identical plastic tanks, rearing zebrafish with preferred plants & gravel did not exacerbate agonism. • For fish in glass tanks, the provision of preferred resources reduced agonism. • Small, empty, conventional tanks exacerbated agonism relative to bigger empty ones. • Agonism levels did not predict shoal-level body size variability. • Zebrafish in empty tanks grew longer than those reared with preferred resources. [ABSTRACT FROM AUTHOR]

The objective of the work was to develop a non-invasive methodology for image acquisition, processing and nonlinear trajectory analysis of the collective fish response to a stochastic event. Object detection and motion estimation were performed by an optical flow algorithm in order to detect moving fish and simultaneously eliminate background, noise and artifacts. The Entropy and the Fractal Dimension (FD) of the trajectory followed by the centroids of the groups of fish were calculated using Shannon and permutation Entropy and the Katz, Higuchi and Katz-Castiglioni’s FD algorithms respectively. The methodology was tested on three case groups of European sea bass (Dicentrarchus labrax), two of which were similar (C1 control and C2 tagged fish) and very different from the third (C3, tagged fish submerged in methylmercury contaminated water). The results indicate that Shannon entropy and Katz-Castiglioni were the most sensitive algorithms and proved to be promising tools for the non-invasive identification and quantification of differences in fish responses. In conclusion, we believe that this methodology has the potential to be embedded in online/real time architecture for contaminant monitoring programs in the aquaculture industry.