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Many philosophers and Effective Altruist researchers have argued that the overall welfare of wild fish is negative. Since there are more fish than any other kind of wild vertebrate on earth (even when taken together), the view that suffering is predominate among wild fish is a key part of their larger suggestion that the overall welfare of wild vertebrates is negative, a view I'll call 'wildlife pessimism.' Correspondingly, undermining the wildlife pessimist's view might largely be accomplished simply by taking a closer look at their arguments concerning fish. Focusing on fish alone will allow for a greater depth of empirical analysis than has hitherto been possible in the wildlife welfare debate, which usually features attempts to discuss all wild animals at once. As I will show, wildlife optimism is at least as likely as wildlife pessimism. That is, it seems just as plausible that wild fish have a welfare level that is neutral or positive overall. [ABSTRACT FROM AUTHOR]

Lumpfish (Cyclopterus lumpus) are raised as cleaner fish for controlling sea lice. Intensive rearing is complicated by fin nipping that occurs between juvenile conspecifics. Lumpfish density‐dependent interactions are not well understood; therefore, the effects of rearing density for different fish size classes warranted evaluation. Two size classes (2‐ and 13‐g) of juvenile lumpfish were stocked at four different rearing densities (40, 60, 70, and 90 g/L) with growth, survival, and fish aggression assessed over 8 weeks. Mean weight gain and specific growth rates ranged from 170% to 307% and 1.77% to 2.50%, respectively, depending on density treatments, for the 2‐g fish, and from 286% to 471% and 2.42% to 3.10% for the 13‐g fish. Growth was negatively correlated with density, with faster growth linked to lower densities. No mortality occurred in any treatment and significant fish aggression only occurred among the larger lumpfish in the higher rearing densities. Based on these findings, growth of 2‐g lumpfish can be increased if reared at 40 g/L or slowed at 70 g/L without impacting aggression. For grow out of 13‐g fish to ~70 g with minimal aggression, a 40 g/L rearing density is recommended for faster growth and 60 g/L for slower growth. [ABSTRACT FROM AUTHOR]

There is an increased demand for tuna meat to supply the growing global sushi and sashimi market. Current methods to farm tunas, especially Atlantic bluefin tunas (ABFTs; Thunnus thynnus), are unsustainable. This is driving a movement towards closed-cycle ABFT aquaculture, i.e., farming tuna from spawning and hatching to slaughter on land, to try and meet the demand for these fish. Tunas are not domesticated species and thus face different challenges in terms of closed-cycle aquaculture when compared to other farmed fish species. Tunas also possess unique physiological traits such as regional endothermy and ram ventilation which affect their needs and how they are farmed. No current global standards exist to measure or monitor ABFT welfare in captivity, because there are many unknown factors surrounding ABFT welfare in aquaculture settings. There is a need to conduct studies that measure the baseline physiological parameters of ABFT in closed-cycle systems. Issues such as manipulation of breeding cycles, tank design, and slaughter procedures need attention and further research is required before such welfare indicators can be established. Stress is an overarching concern for animal welfare. In particular, pre-slaughter crowding and stress negatively affect the quality of the meat produced due to lactic acid buildup in the red muscle. Further research needs to be conducted throughout all life stages in terms of both animal welfare implications and the commercial viability of farmed ABFTs. [ABSTRACT FROM AUTHOR]

In this study, we described immediate/acute reactions to stress-related chemical cues (SC – Stress Cue) in fish. Specifically, we evaluated the effects of SC on ventilation rate (VR) and feeding behavior in Nile tilapia (Oreochromis niloticus), a highly relevant species for world aquaculture, therefore, to understand the diversity of stressful contexts and stress responses in this species have important practical applications (stress reduction). Stress cue was obtained from conspecifics exposed to a handling stressor. Stress was confirmed by measuring plasma cortisol levels. The responses to SC were contrasted to chemical control cues: a cue originated from non-stressed conspecifics and pure water (vehicle control). We observed that Nile tilapia exposed to SC had an increase in VR, but without effects on feeding behavior (feeding latency and ingestion). Thus, the SC is a stressor that induces readily stress response (VR increase), suggesting sympathetic activation, but did not change feeding performance. In practical terms, it is positive because although social propagation of stress via SC elicits a stress response, it did not harm appetite. [ABSTRACT FROM AUTHOR]

Purpose: A limited number of studies have aimed at understanding behavior towards animal welfare. However, there are indications that consumers make an important distinction between land animals and fish. As no studies have attempted to explain the factors that influence consumer behavior towards the welfare of fish, this study aims to explain the behavior using the value–belief–norm (VBN) model. In addition, we extend the model by using empathy as a factor influencing the formation of personal norms. This study argues that by adding empathy to the model, we will improve the ability of the VBN to explain moral behavior. Design/methodology/approach: The study is based on survey data from 416 Norwegian consumers. A structural equation modeling analysis with latent constructs is used to test the hypotheses. Findings: The findings validate the ability of the VBN model to explain consumer intention to buy products containing fish with better welfare. We also showed that empathy and beliefs strongly influence personal norms. The extended VBN model increased the explained variance of personal norm by 11,54%. Consumers with biospheric values are strongly likely to have empathetic feelings towards fish suffering and believe that fish can feel pain. However, consumers with hedonistic values are significantly negatively related to beliefs and empathy. Practical implications: By understanding the role of empathy, companies can develop marketing strategies that appeal to consumers' values, empathy and beliefs and ultimately encourage them to make purchases that support fish welfare. Originality/value: Practically, this study explores consumers' beliefs towards fish welfare and identifies consumers who are more likely to purchase products containing fish with better welfare based on their values. [ABSTRACT FROM AUTHOR]

The stress‐coping ability (SCA) is one of the core aspects of fish welfare and is of vital importance for fish production in the aquaculture industry and for fish fitness in hatchery release. Environmental enrichment (EE), a method of introducing external stimuli into the husbandry environment, has been recently proposed to improve fish SCA, but the present experimental evidence is mixed, and the reasons for these discrepancies are unclear. Here, we conducted a global meta‐analysis using a data set that consists of 1786 cases from 107 studies across 42 fish species to solve this problem. Overall, we found that enriched fish had significantly higher SCA than control fish, reflected in either basal stress levels or stress responses. Meta‐regression analyses showed that specific subgroups of enrichment type, fish developmental stage, stress category, stress duration, stress place, sample tissue and indicator system showed significant positive EE effects on SCA. Multi‐model inference indicated that the indicator system, fish developmental stage, stress characteristic and enrichment mode are important drivers for the high heterogeneity among effect sizes. These results highlight the importance of introducing EE into the rearing systems, which will not only increase the welfare of aquaculture fish but also improve the ecological adaptability of released fish. The comprehensive knowledge obtained in this analysis will provide insights into fish ontogenetic plasticity and its responses to EE and have important implications for improving the production cycle in fish aquaculture and fisheries conservation. [ABSTRACT FROM AUTHOR]

Billions of fishes are kept in captivity for research and food production world‐wide, with a strong impetus for maintaining high welfare standards. Accordingly, the importance of empirical research into the welfare and husbandry of captive fishes is increasingly acknowledged in both science and aquaculture, alongside growing public and governmental interest. Physical enrichment can have an important influence on welfare in of captive fishes, but many questions remain. Here, we summarise the current state of research and outline knowledge gaps in the area of physical enrichment, which is a fundamental aspect to improving welfare of captive fishes. To explore the level of research interest this area across time we conducted a series of surveys, using the number of papers published per year as a metric. These surveys highlight that work on fish welfare, while representing a relatively low proportion of fish research overall, is increasing rapidly. For species that are of aquaculture importance or used commonly as laboratory subjects, we show a positive relationship between general research interest and number of welfare‐related papers. However, for many, particularly relatively less studied, species the proportion of papers on enrichment remains low, with a slower increase compared to welfare‐related papers in general. In terms of common metrics used to quantify fish welfare, there is a reliance on growth and behaviour, with scope for inclusion and combination of a more comprehensive range of reproducible measures. We finish by highlighting recent progress, promising areas for future research and suggestions for advances in this area. [ABSTRACT FROM AUTHOR]

Abstract The present study aimed to determine the anaesthetic effectiveness, safety, and applicable concentrations of coriander (Coriandrum sativum) essential oils (CEO) for three-spotted tilapia (Oreochromis andersonii). For this purpose, CEO concentrations of 400, 500, and 600 µL/L were tested at two temperatures, 20.90 ± 1.19 °C and 30.60 ± 0.92 °C, on three different sizes (small, medium, and large) of the fish in duplicate glass aquaria with 200 mg/L of tricaine methanesulfonate (MS-222) served as the control. The sedative efficacy during simulated transportation experiments was also carried out. The results demonstrated that the induction and recovery time in O. andersonii anaesthetised with CEO were significantly influenced by concentration, water temperature, and fish size (P

The present study aimed to determine the anaesthetic effectiveness, safety, and applicable concentrations of coriander (Coriandrum sativum) essential oils (CEO) for three-spotted tilapia (Oreochromis andersonii). For this purpose, CEO concentrations of 400, 500, and 600 µL/L were tested at two temperatures, 20.90 ± 1.19 °C and 30.60 ± 0.92 °C, on three different sizes (small, medium, and large) of the fish in duplicate glass aquaria with 200 mg/L of tricaine methanesulfonate (MS-222) served as the control. The sedative efficacy during simulated transportation experiments was also carried out. The results demonstrated that the induction and recovery time in O. andersonii anaesthetised with CEO were significantly influenced by concentration, water temperature, and fish size (P < 0.05). A concentration of 600 µL/L of CEO was found to be highly effective in inducing deep anesthesia and promoting rapid recovery in small and medium-sized fish at both water temperatures (20 and 30 °C). Based on this study, 100 µL/L of CEO is recommended for short-term transportation lasting up to 4 h, while 50 µL/L is advised for longer-distance transport. Although coriander essential oil shows anaesthetic effectiveness in three-spotted tilapia, further research is needed to fully understand the efficacy and safety of CEO across different fish species. [ABSTRACT FROM AUTHOR]

DNA methylation clocks provide information not only about chronological but also biological age, offering a high-resolution and precise understanding of age-related pathology and physiology. Attempts based on transcriptomic and epigenetic approaches arise as integrative biomarkers linking the quantification of stress responses with specific fitness traits and may help identify biological age markers, which are also considered welfare indicators. In gilthead sea bream, targeted gene expression and DNA methylation analyses in white skeletal muscle proved sirt1 as a reliable marker of age-mediated changes in energy metabolism. To complete the list of welfare auditing biomarkers, wide analyses of gene expression and DNA methylation in one- and three-year-old fish were combined. After discriminant analysis, 668 differentially expressed transcripts were matched with those containing differentially methylated (DM) regions (14,366), and 172 were overlapping. Through enrichment analyses and selection, two sets of genes were retained: 33 showing an opposite trend for DNA methylation and expression, and 57 down-regulated and hypo-methylated. The first set displayed an apparently more reproducible and reliable pattern and 10 multifunctional genes with DM CpG in regulatory regions (sirt1, smad1, ramp1, psmd2—up-regulated; col5a1, calcrl, bmp1, thrb, spred2, atp1a2—down-regulated) were deemed candidate biological age markers for improved welfare auditing in gilthead sea bream. [ABSTRACT FROM AUTHOR]

Environmental enrichment is a reliable and useful tool for improving fish welfare in farms. Structural enrichment is widely studied and applied to fish, with positive effects also on the zootechnical parameters of fish farming. In our study, we examined whether artificial shelters and water hyacinth - structural enrichments - improve the quality of tilapia fillets. Tilapia juveniles (n = 480) underwent three independent treatments over 100 days: artificial water hyacinth enrichment, shelter enrichment, and control (no enrichment). After slaughtering, we evaluated physical-chemical indicators of meat quality. Whereas meat pH was not affected by the availability of enrichment, we found less lightness in terms of chroma b* of the flesh from tilapia raised with artificial water hyacinth and more flesh toughness in the texture of tilapia raised with shelter, indicating a higher-quality product. Regarding the fatty acid profile, differences were found when individually analyzed. All fatty acids that differed among treatments (C4:0, C23:0, C24:0, C16:1, and C24:1) exhibited better performance in groups reared with structural enrichment. In conclusion, improving Nile tilapia welfare with structural enrichment enhances its flesh quality. Thus, in addition to promoting the welfare of farmed fish, this enrichment may benefit both farmers and consumers. [ABSTRACT FROM AUTHOR]

The aim of this study was to test the impact of replacing vegetable oils commonly used in the feed of Arctic char (Salvelinus alpinus) with biomass of the oleaginous yeast Rhodotorula toruloides. For that, a control feed containing vegetable oils and an experimental feed including yeast biomass at 15% level, were fed to Arctic char. Sensory properties of the fish were tested. The content of undesirable compounds in the new feed ingredient were evaluated. Selected heavy metals and organic pollutants were measured in the yeast biomass and the levels found were below the limits of the regulations defined by the European Union. Moisture and ash contents were similar between the two feeds. Hepatic activity of 7-ethoxyresorufin-O-deethylase was evaluated between the two fish groups and no significant differences were observed. The sensory analysis conducted on heat treated fish fillets with untrained volunteers showed no perceptible sensory difference. [ABSTRACT FROM AUTHOR]

Society is becoming more demanding with aquaculture's environmental footprint and animal wellbeing. In order to potentially mitigate these concerns, feed formulations could be based on eco-efficient (circular economy-driven) or organic ingredients. This study aimed to investigate the growth performance, feed utilization, and health status of juvenile Nile tilapia (Oreochromis niloticus) when fed with such feeds. The growth trial lasted for 8 weeks, and fish had an initial weight of 31.0 ± 0.5 g (mean ± SD). Fish were fed until visual satiation, in quadruplicate, with one of three isonitrogenous and isoenergetic experimental feeds: a commercial-like feed without fishmeal (PD), a diet based on ingredients compatible with organic certification (ORG), or a feed formulated using circular economy-driven subproducts and emergent ingredients (ECO). Fish fed ECO showed a tendency for decreased feed intake, while ORG fish significantly reduced their intake compared to those fed PD. Consequently, fish fed ECO (62.7 ± 5.4 g) exhibited almost half the growth than those fed PD (107.8 ± 6.1 g), while ORG fish almost did not increase their weight (32.7 ± 1.3 g). ECO and ORG diets had a lower digestibility for protein, lipid, and energy when compared to PD. Feed utilization of fish fed ECO or ORG was also lower than those fed PD. From the health-related genes analyzed, only glutathione reductase (gsr) showed statistically significant differences, being more expressed in fish-fed ECO than those fed PD. Thus, even when such novel formulations induced extreme effects on voluntary feed intake, their impact was noted only in fish growth, but not in robustness. [ABSTRACT FROM AUTHOR]

Aquafeed's contamination by microplastics can pose a risk to fish health and quality since they can be absorbed by the gastrointestinal tract and translocate to different tissues. The liver acts as a retaining organ with the consequent triggering of oxidative stress response. The present study aimed to combine the use of natural astaxanthin with natural-based microcapsules to counteract these negative side effects. European seabass juveniles were fed diets containing commercially available fluorescent microplastic microbeads (1–5 μm; 50 mg/kg feed) alone or combined with microencapsulated astaxanthin (AX) (7 g/kg feed; tested for half or whole feeding trial—30 or 60 days, respectively). Fish from the different dietary treatments did not evidence variations in survival and growth performance and did not show pathological alterations at the intestinal level. However, the microplastics were absorbed at the intestinal level with a consequent translocation to the liver, leading, when provided solely, to sod1, sod2, and cat upregulation. Interestingly, the dietary implementation of microencapsulated AX led to a mitigation of oxidative stress. In addition, the microcapsules, due to their composition, promoted microplastic coagulation in the fish gut, limiting their absorption and accumulation in all the tissues analyzed. These results were supported by in vitro tests, which demonstrated that the microcapsules promoted microplastic coagula formation too large to be absorbed at the intestinal level and by the fact that the coagulated microplastics were released through the fish feces. [ABSTRACT FROM AUTHOR]

Abstract Lumpfish (Cyclopterus lumpus) are raised as cleaner fish for controlling sea lice. Intensive rearing is complicated by fin nipping that occurs between juvenile conspecifics. Lumpfish density‐dependent interactions are not well understood; therefore, the effects of rearing density for different fish size classes warranted evaluation. Two size classes (2‐ and 13‐g) of juvenile lumpfish were stocked at four different rearing densities (40, 60, 70, and 90 g/L) with growth, survival, and fish aggression assessed over 8 weeks. Mean weight gain and specific growth rates ranged from 170% to 307% and 1.77% to 2.50%, respectively, depending on density treatments, for the 2‐g fish, and from 286% to 471% and 2.42% to 3.10% for the 13‐g fish. Growth was negatively correlated with density, with faster growth linked to lower densities. No mortality occurred in any treatment and significant fish aggression only occurred among the larger lumpfish in the higher rearing densities. Based on these findings, growth of 2‐g lumpfish can be increased if reared at 40 g/L or slowed at 70 g/L without impacting aggression. For grow out of 13‐g fish to ~70 g with minimal aggression, a 40 g/L rearing density is recommended for faster growth and 60 g/L for slower growth.

There is an increased demand for tuna meat to supply the growing global sushi and sashimi market. Current methods to farm tunas, especially Atlantic bluefin tunas (ABFTs; Thunnus thynnus), are unsustainable. This is driving a movement towards closed-cycle ABFT aquaculture, i.e., farming tuna from spawning and hatching to slaughter on land, to try and meet the demand for these fish. Tunas are not domesticated species and thus face different challenges in terms of closed-cycle aquaculture when compared to other farmed fish species. Tunas also possess unique physiological traits such as regional endothermy and ram ventilation which affect their needs and how they are farmed. No current global standards exist to measure or monitor ABFT welfare in captivity, because there are many unknown factors surrounding ABFT welfare in aquaculture settings. There is a need to conduct studies that measure the baseline physiological parameters of ABFT in closed-cycle systems. Issues such as manipulation of breeding cycles, tank design, and slaughter procedures need attention and further research is required before such welfare indicators can be established. Stress is an overarching concern for animal welfare. In particular, pre-slaughter crowding and stress negatively affect the quality of the meat produced due to lactic acid buildup in the red muscle. Further research needs to be conducted throughout all life stages in terms of both animal welfare implications and the commercial viability of farmed ABFTs.

The cownose ray (Rhinoptera bonasus) faces vulnerability primarily due to unregulated fishing, resource overexploitation, and habitat degradation. Consequently, individuals maintained under human care play a pivotal role in species conservation, particularly when their welfare is prioritized. Achieving optimal welfare in aquarium settings relies heavily on effective management practices, notably environmental enrichment. However, research on the efficacy of such techniques for cownose rays remains limited. Thus, this study sought to evaluate the impact of various food enrichment items on the behavior of four individuals at the São Paulo Aquarium in Brazil. The project encompassed three phases: baseline, enrichment, and post-enrichment. Enrichment items, designed to mimic the species’ natural foraging behavior, included an ice block containing food, food hidden in vegetables fixed to structures at the bottom of the tank, a tray with substrate and food, and a perforated plastic container with food inside. Behavioral observations utilized focal sampling with instantaneous recording every minute. Results showed increased foraging activity in the post-enrichment phase, whereas swimming increased and following behaviors decreased during the enrichment phase. Additionally, foraging behaviors predominantly occurred near the aquarium bottom. Overall, findings suggest that enrichment items effectively stimulated natural behaviors in cownose rays and were very attractive to the fish, advocating for their integration into species management protocols to enhance welfare.

The cownose ray (Rhinoptera bonasus) faces vulnerability primarily due to unregulated fishing, resource overexploitation, and habitat degradation. Consequently, individuals maintained under human care play a pivotal role in species conservation, particularly when their welfare is prioritized. Achieving optimal welfare in aquarium settings relies heavily on effective management practices, notably environmental enrichment. However, research on the efficacy of such techniques for cownose rays remains limited. Thus, this study sought to evaluate the impact of various food enrichment items on the behavior of four individuals at the São Paulo Aquarium in Brazil. The project encompassed three phases: baseline, enrichment, and post-enrichment. Enrichment items, designed to mimic the species' natural foraging behavior, included an ice block containing food, food hidden in vegetables fixed to structures at the bottom of the tank, a tray with substrate and food, and a perforated plastic container with food inside. Behavioral observations utilized focal sampling with instantaneous recording every minute. Results showed increased foraging activity in the post-enrichment phase, whereas swimming increased and following behaviors decreased during the enrichment phase. Additionally, foraging behaviors predominantly occurred near the aquarium bottom. Overall, findings suggest that enrichment items effectively stimulated natural behaviors in cownose rays and were very attractive to the fish, advocating for their integration into species management protocols to enhance welfare. [ABSTRACT FROM AUTHOR]

The principles of three Rs—REPLACEMENT, REDUCTION, and REFINEMENT—govern the protection and use of animals, including fish, for research purposes in the European Union and Norway. In this paper, we discuss some straightforward steps to simplify the delivery of these principles at the idea stage and adapt some of these examples for conducting fish trials related to health and welfare. Although some of the approaches are well established in other animal science arenas, we believe there can be a timely recap of their key facets. We discuss a number of simple strategies to emphasize how a reduction in fish numbers can be achieved from initial project conception to implementation, highlighting not only their advantages but also their limitations. We also highlight the role that funding agencies can play in the implementation of the 3R principles in aquaculture research. These simple points can be used in frameworks to initiate a broader and dynamic intersectoral dialogue among stakeholders of aquaculture research on how to promote ethics and embrace opportunities for this within the tenets of the 3Rs. [ABSTRACT FROM AUTHOR]

The aquaculture industry frequently employs various slaughter methods that subject fish to inhumane conditions, resulting in significant suffering. This study examined the effects of electrical method on the welfare of farmed fish (Mesopotamichthys sharpeyi) compared to air asphyxiation. Fish captured with electricity exhibited calm behavior until death, in contrast to fish treated with air asphyxiation, which exhibited violent responses within 4 minutes of capture. The electrical method achieved a complete state of unconsciousness 7 minutes faster than air asphyxiation. Our results show that air asphyxiation raised cortisol levels more than the electrical method, with no significant difference in glucose and lactate concentrations. Electrically treated fish had higher superoxide dismutase and liver-reduced glutathione levels, while suffocated fish showed elevated GSH and liver catalase levels. Radiographs revealed no fractures or skeletal changes. Electrical stunning had no effect on gill tissue, but caused brain tissue hemorrhage, whereas air asphyxiation caused less damage. Air asphyxiation caused gill tissue issues but less brain damage. Consciousness loss is crucial for humane practices. Specific electrical currents (110V for 30s) could improve aquaculture and fish welfare. [ABSTRACT FROM AUTHOR]

The live transport of farmed fish is an important practice in Chinese aquaculture due to consumer preferences in its domestic market. However, live transport can be stressful for fish and may cause many welfare issues. This study aimed to examine the effects of transport density on the welfare of largemouth bass (Micropterus salmoides). Adult fish were allocated to four experimental treatments in a two‐factor design (N = 5 groups per treatment). Factor one was stocking density of either 39 (low density) or 78 (high density) g L−1. Factor two was transport, with half of the fish groups exposed to simulated transport stress for 3 h using a motion platform, and the other half kept in static tanks for the same length of time. Baseline behavior and physiology were determined from a subset of fish after acclimation but before selection into groups and application of transport. To determine the effects of transport, stocking density, and their interaction on the experimental groups, physiological sampling and behavioral recording were carried out immediately after simulated transport, and water quality was measured both before and after transport. Changes in water quality were observed between two timepoints, with decreased dissolved oxygen levels and increased water temperature. Total ammonia nitrogen levels significantly increased in all treatments over time, particularly in the high‐density groups. Fish ventilation rates were significantly elevated in the groups kept at a high stocking density regardless of whether they also experienced transport stress. Fish transported at a high stocking density also showed more fear‐related behaviors such as freezing and thigmotaxis than non‐transported groups. Serum cortisol, catalase, and aspartate transaminase levels were significantly higher in the transported treatment groups compared to the baseline fish, but no difference was found for serum glucose, lactate, and glutathione peroxidase. We concluded that 3 h of simulated transport was stressful to largemouth bass kept at 78 g L−1, as evidenced by altered fish physiological and behavioral indicators of stress, as well as deteriorated water quality. Additionally, we identified a positive correlation between serum and skin mucus samples for cortisol, glucose, and lactate in transported fish, providing important information for developing less invasive methods for the welfare assessment of largemouth bass. [ABSTRACT FROM AUTHOR]

A 5-level crowding intensity scale for directing and auditing the crowding of Atlantic salmon in sea cages based on surface observations is currently included in standards, manuals, and guidelines for fish farmers. Here we test the feasibility of using this scale to create distinct crowding levels, the effects of these different levels upon fish welfare, and the suitability of a set of possible operational welfare indicators (OWIs) and laboratory-based welfare indicators (LABWIs) to be included in toolboxes for monitoring and assessing fish welfare in relation to the crowding of salmon in sea cages. Crowding level 1 was not included in this study since this is a very light level of crowding, and also not level 5 as this level clearly would harm the fish and lead to mortalities. We were able to use the scale to create three distinct crowding levels in two of three separate crowding events in 12×12m2 sea cages. Although the farm personnel were experienced, it soon became evident that underwater monitoring of fish behaviour and how the net was tightened around the fish was important to make sure that no pockets or irregularities that could harm the fish were formed during the crowding. Despite evidence of increased stress and epidermal damage with increased crowding intensity, there were no clear indications that this led to any long-term detrimental effects on fish welfare. In conclusion an OWI-toolbox for crowding should include both surface and underwater observations, monitoring of oxygen conditions, and morphological injury data to steer decisions to prevent welfare problems and mortalities. In addition, qualitative assessment of fish behaviour, plasma cortisol, and skin histology can be included in a LABWI-toolbox if more in-depth information on the effects from the crowding is wanted.

Husbandry procedures can be stressful for captive animals. Knowledge of the physiological effects of these procedures and the reduction of stress during regular maintenance is of pivotal importance to ensure good welfare. Environmental enrichment (EE) can be an asset to animal keepers as it has many benefits on captive animals, including the reduction of stress indicators in many aquatic species. This is particularly relevant for broodstock animals, who may spend years in captivity and who are essential for successful fish farming. We studied whether structural enrichment had a stress-reducing effect on broodstock of gilthead seabream (Sparus aurata) during standard husbandry procedures, monitoring their heart rate with surgically implanted internal bio-loggers (DST milli HRT, Star-Oddi) in 18 fish. These fish were distributed in six tanks, three of which had an EE structure consisting of a 1 m2 floating structure with nine suspended organic cables, while the other three tanks had no enrichment. We added seven more unmarked fish to each tank to simulate broodstock farming conditions (i.e., ten fish per tank). After five days of post-surgical recovery, we tested feeding, netting, and cleaning every day for three consecutive days, and a formaldehyde bath as a prophylactic procedure on the fourth day on the logger-implanted fish and continued to record their recovery for eight more days. Overall, when subjected to stressful husbandry procedures, fish reared under EE show reduced heart rate and amplitude, and faster recovery to baseline levels than non-enriched animals. Our results show that EE can be used to improve the welfare of farmed fish by reducing their stress and should be employed as a good management practice in finfish production, and is especially relevant for high-value fish that spend long periods in captivity, such as spawners.

Ensuring fish welfare is essential from the ethical, legal, environmental, economic, and social perspectives. It plays a vital role in maintaining the health and sustainability of aquaculture practices while respecting the intrinsic value and welfare of the fish themselves. The presence of reliable welfare assessment schemes is of utmost importance to appraise the well-being of animals in aquaculture and uphold stringent welfare standards. In determining fish welfare, conducting welfare assessments with non-invasive biomarkers is crucial thus the primary objective of this study is to explore the potential usability of visible parasites as welfare biomarkers in fish without causing any harm to the fish. In this research, certain secondary stress indicators (hematocrit, plasma glucose and lactate) were employed as biomarkers for assessing the well-being of European sea bass (Dicentrarchus labrax). The study aimed to investigate whether there is a possible correlation between the presence of visible ectoparasites on the gills (specifically, the Copepod parasite, Lernantropus kroyeri) and the aforementioned stress parameters. Thus, in this study, the examination was conducted to establish the validity of ectoparasites as non-invasive biomarkers for evaluating the welfare of fish. The results showed that there was a statistically significant relationship between the intensity of ectoparasites and the stress parameters used as indicators of welfare. The observable presence and intensity of ectoparasites on the gills of the fish can be proposed as a non-invasive biomarker for evaluating fish welfare in aquaculture.

Environmental enrichment has the potential to improve the welfare and post‐release survival of hatchery fish stocked for conservation purposes. However, the effectiveness of environmental enrichment is partly dependent on the fish species, life stage, and specific enrichment structure used. To enhance the effectiveness of environmental enrichment, it is crucial to focus on characteristic differences in enrichment structures, such as type and level. This study investigated how differences in enrichment type and level affected physiological and behavioral aspects of the welfare of pre‐release juvenile rock bream Oplegnathus fasciatus by evaluating growth performance, basal and stressed cortisol levels, antioxidant enzyme activities, and exploratory behaviors regarding anxiety and flexibility. Fish were reared for 4 weeks in different enrichment treatments: barren, low‐level cover structure, high‐level cover structure, low‐level interference structure (LI), and high‐level interference structure (HI). The results revealed that fish reared with the LI treatment showed less anxiety and greater flexibility with respect to exploratory behaviors, without oxidative damage being detected. Despite exhibiting less anxiety as well, fish reared in the HI treatment had oxidative damage, indicated by lower superoxide dismutase activity, compared to those in the barren treatment. In addition, none of these enrichment structures enhanced growth performance or mitigate chronic and acute stress responses. Overall, the low‐level interference structure may be more favorable in promoting the behavioral welfare of the fish. Application of this type and level of enrichment may increase the survival of the hatchery fish after release, which is critical to stocking success. [ABSTRACT FROM AUTHOR]

An 84-day growing trial was conducted to evaluate Liza ramada's performance and health. Five treatments (3 replicates) were tested using an experimental diet (ED) supplemented with rosemary oil (RO) or RO and amylase-lipase (AL) enzymes as follows; (T1) fish-fed ED with no additives "control"; (T2) fish fed ED containing 0.5 kg ton−1 RO; (T3) fish fed ED containing 0.5 kg RO and 0.917 kg AL ton−1; (T4) fish fed ED containing 1 kg ton−1 RO; and (T5) fish fed ED containing 1 kg RO and 0.917 kg AL ton−1. A total of 150 Liza ramada fish (7.30 ± 0.01 g/fish) were housed in 15 hapas (10 fish/hapa) and fed the tested diets twice daily at 4–3% of body weight. Findings revealed that fish that received RO and RO + AL supplemented diets had lower NH 3 levels and higher survival rates (24.32, 51.34, 37.83, and 54.05%) in groups T2, T3, T4, and T5, respectively when compared to the control. Furthermore, improvements in FW, WG, SGR, and FCR were recorded for fish-fed supplemented diets with better values at T5. Moreover, liver enzyme activity, kidney function indices, and intestinal histomorphometric measurements were improved in fish-fed RO + AL treated diets. The recommended treatment is T5 (1 kg RO and 0.917 kg AL ton−1). [ABSTRACT FROM AUTHOR]

Fish deformities are detrimental to aquaculture and conservation initiatives; it is also an ethical problem and causes substantial financial losses to the aquaculture industry. The exact mechanism of deformities is still a mystery. Several factors cause deformities in fish; it seems that the deformations are inevitable but can be minimised by adopting good aquaculture practices such as proper broodstock husbandry, standard breeding and larval rearing protocol, management of water quality parameters, and providing nutritionally balanced feed, especially to the broodstock and developing larvae. In addition, it can be minimised by early detection of deformities, especially at the embryonic and larval stages. Monitoring of stocking materials should be an essential part of responsible aquaculture and conservation programmes; stocking materials should be free from any types of deformities as it affects not only aquaculture production, profitability and success of conservation programmes but also the reoccurrence of deformities in nature. The mechanism behind deformities and the development of low‐cost, robust methods/tools for detecting deformities in fish remain a challenge. Still, the opportunity exists to develop a robust marker that can predict deformities even at early embryonic and larval stages. [ABSTRACT FROM AUTHOR]

To investigate the possible effect of different feed ration levels on the growth, welfare, and early maturation of juvenile Atlantic salmon, 450 salmon parr with a mean (±standard error) initial weight of 51.6 g (±0.8) were reared in triplicate under three different feed ration levels for five months. The control group (100r) was fed every day, the 50r group was fed every other day, and the 33r group was fed every third day. In every group, 75 fish (half of the group) were individually tagged for monitoring of growth. The number of fin wounds was used as the welfare indicator, and to inspect the development of maturation, all fish were euthanized, and development of the gonads was monitored by visual inspection at the termination of the trial. The control group (100r) showed a significantly higher specific growth rate (0.90% day−1) compared to the lower fed groups (50r, 0.67% day−1 and 33r, 0.49% day−1); however, the growth difference was 21–24% less than expected solely on the difference in the amount of feed given to each group. The 100r group showed the highest welfare rating, and the 33r group the lowest possible, indicating more aggressive behaviour and fin biting due to feed restriction in the 33r group. No difference (p > 0.45) was found in the development of maturation in females, but the combined numbers of males in maturity stages 2–5 showed an overall trend towards slower maturation in the 33r group compared to the 100r group. Although the present findings on the development of sexual maturation were subtle due to the limited time frame of the trial, the findings offer a foundation for future investigation into the relationship between the feed ration level and the development of sexual maturation in the rearing of juvenile Atlantic salmon. [ABSTRACT FROM AUTHOR]

Shelter is an important resource, serving as protection from rivals, predators and environmental stressors. The physical dimensions of a potential shelter are an important factor that can affect decisions about potential shelter options. Animals must select a shelter that they can fit into and use as a refuge, but beyond that, do they show fine-scale preferences based on shelter dimensions? This question has been actively studied for species whose shelter use is closely connected to their life cycles, such as obligate shell dwellers and nest-inhabiting species. However, preferences and decision making for temporary shelters has received less attention. We tested whether three-spined sticklebacks, Gasterosteus aculeatus , a common laboratory model, exhibit preferences in shelter use (actively entering and spending time within a shelter) between shelters with different dimensions. We used PVC tubes of different dimensions as shelters and conducted a simultaneous choice assay where individual fish were presented with each of three tubes available for use as shelter. The fish showed a clear preference, using larger diameter shelters more frequently than either of the other two options. There was no difference in the number of nonsheltering visits fish made or time to enter a shelter across tube sizes, which suggests an active selection by the fish rather than passive bias. There was no difference in duration of time spent within a shelter, suggesting that despite these preferences, actual benefit derived by the fish may be decoupled from the shelter dimensions. Our results offer opportunities for future research that addresses longer term questions in both behavioural ecology and welfare. What drives the preference for larger diameter tubes, and are there are long-term benefits to shelter with preferred dimensions? Certainly, our results suggest that housing sticklebacks with larger diameter shelters may be a simple and convenient means to improve welfare. • Do three-spined sticklebacks select shelters based on differences in dimensions? • We presented fish with different shelters in a simultaneous choice arena. • Fish showed a higher frequency of shelter use in larger diameter shelters. • Using larger PVC tubes may be a convenient way to improve stickleback housing. [ABSTRACT FROM AUTHOR]

Ballan wrasse (Labrus bergylta) are commonly used as cleaner fish in salmon farms as a biological treatment to mitigate sea lice infestation. Improved welfare for cleaner fish both during production of these fish and when in sea-cages with salmon is crucial for the industry's development. A common operational procedure in ballan wrasse production is transporting juveniles from one landbased farm to another for further on-growing. Episodes of increased mortality have been reported after such transportations. In this study, the relationship between transport stress and post-transport mortality at the on-growing facility was examined. It was also investigated if light sedation with AQUI-S® can mitigate stress during transport. Stress was quantified by measuring cortisol release rate to the tank water during transport. This was investigated in 10 commercial live carrier truck transports (6 without AQUI-S® sedation and 4 with sedation during loading and transport). The total time of transport varied between 12 and 21h. In general, mortality was significantly higher (1.0± 0.6% day-1) the first five days posttransport compared to 15-20days post transport (0.5% day-1). There was also a strong relationship between fish weight at transport and post-transport mortality, where higher mean weight at transport reduced mortality. In contrast to what was expected, AQUI-S® treatment during transport procedures increased cortisol excretion rate, suggesting a stimulating effect of AQUI-S® on the stress axis in ballan wrasse. Considering these results, the value of using AQUI-S® to reduce stress during transport of juvenile ballan wrasse might be questioned. However, there was no relationship between cortisol release rate during transport and post-transport mortality. Furthermore, this study emphasizes that water cortisol measurements can be used as a none-invasive tool for monitoring stress and can be integrated into the welfare evaluation during commercial fish transports. [ABSTRACT FROM AUTHOR]

Simple Summary: This study focuses on the use of high-quality and sustainable feed ingredients, derived from circular bioeconomy processes, as major components of new diets for Gilthead sea bream and European sea bass, the most important farmed fish in the Mediterranean basin. In this study, we investigated the effects of replacing dietary plant proteins with insect and poultry by-product meals on the liver health of sea bream and sea bass through histological and biochemical analyses. Four diets were tested, including a control fish meal-free diet, based on plant-derived ingredients, and three other ones, in which 40% of the plant protein was replaced with Hermetia illucens and poultry by-product meals. The results revealed distinct responses to the test diets between sea bream and sea bass, in terms of biometric parameters, lipid metabolism, and liver condition. Sea bream utilized dietary nutrients efficiently, adapting to the test diets in terms of weight gain, physiological well-being, and liver health. Conversely, the test diets led to significant hepatic lipid accumulation in sea bass, resulting in an increased risk to liver health. The liver health of Gilthead sea bream and European sea bass, fed with fish meal-free diets, including various proportions of plant proteins, as well as insect and poultry by-product meals, was investigated through biochemical and histological analyses using a new liver index (LI) formula. Four isoproteic (45% Dry Matter, DM) and isolipidic (20% DM) diets were compared, including a plant-based control diet (CV) and three other test diets, in which 40% of a plant protein-rich ingredient mixture was replaced with meals from Hermetia illucens (H40) or poultry by-product (P40) alone, or in combination (H10P30). The trials lasted 12 and 18 weeks for sea bream and sea bass, respectively. The results obtained thus far highlighted species-specific differences in the physiological response to dietary changes. In sea bream, the biochemical and histological responses suggest favorable physiological and liver health statuses, with higher serum cholesterol (CHO) and triglyceride (TAG) levels, as well as moderate hepatocyte lipid accumulation, with the H10P30 diet compared to the CV (p < 0.05). In sea bass, all diets resulted in elevated serum TAG levels and lipid accumulation in the liver, particularly in fish fed the P40 one (p < 0.05), which resulted in the highest LI, coupled with a higher frequency of severe lipid accumulation, hypertrophy, cord loss, peripheral nuclei displacement, and pyknosis. In conclusion, sea bream adapted well to the test diets, whereas sea bass exhibited altered hepatic lipid metabolism leading to incipient liver steatosis, likely due to the high lipid contents of the diets, including the insect and poultry meals. The LI formula developed in this study proved to be a reliable tool for assessing the effects of dietary changes on the liver health of sea bream and sea bass, consistent with biochemical and histological findings. [ABSTRACT FROM AUTHOR]

Ensuring fish welfare is essential from the ethical, legal, environmental, economic, and social perspectives. It plays a vital role in maintaining the health and sustainability of aquaculture practices while respecting the intrinsic value and welfare of the fish themselves. The presence of reliable welfare assessment schemes is of utmost importance to appraise the well-being of animals in aquaculture and uphold stringent welfare standards. In determining fish welfare, conducting welfare assessments with non-invasive biomarkers is crucial thus the primary objective of this study is to explore the potential usability of visible parasites as welfare biomarkers in fish without causing any harm to the fish. In this research, certain secondary stress indicators (hematocrit, plasma glucose and lactate) were employed as biomarkers for assessing the well-being of European sea bass (Dicentrarchus labrax). The study aimed to investigate whether there is a possible correlation between the presence of visible ectoparasites on the gills (specifically, the Copepod parasite, Lernantropus kroyeri) and the aforementioned stress parameters. Thus, in this study, the examination was conducted to establish the validity of ectoparasites as non-invasive biomarkers for evaluating the welfare of fish. The results showed that there was a statistically significant relationship between the intensity of ectoparasites and the stress parameters used as indicators of welfare. The observable presence and intensity of ectoparasites on the gills of the fish can be proposed as a non-invasive biomarker for evaluating fish welfare in aquaculture. [ABSTRACT FROM AUTHOR]

Background: Sedative agents are utilized to mitigate stress and improve fish welfare during and after transportation. Objectives: We aimed to assess the effects of myrcene addition to the transportation water on the plasma biochemical profile of common carp, Cyprinus carpio. Methods: For this purpose, common carp (mean weight of 45.3±1.65 g) were transported in plastic bags containing myrcene at concentrations of 0 (CTL), 10 (10 M), 20 (20 M), 30 (30 M), and 50 (50 M) μL/L for 6 h. Then, their plasma parameters were compared to those values before transportation (BT). Results: Transportation significantly (P<0.05) decreased plasma total protein, albumin, alternative complement, lysozyme, sodium, and chloride, while increasing potassium, calcium, alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase in the CTL treatment, as compared to BT. Adding 50 μL/L myrcene to water prevented total plasma protein and albumin loss. Supplementing 20 μL/L myrcene to water prevented or reduced the changes in plasma ions, alanine aminotransferase, and alkaline phosphatase. Addition of 10-50 μL/L myrcene to water decreased the changes in plasma aspartate aminotransferase. Adding 20 and 30 μL/L myrcene to water mitigated the changes in plasma alternative complement, as 30 μL/L myrcene increased plasma lysozyme activity. Transportation and myrcene addition had no significant effects on plasma immunoglobulin (P>0.05). However, a significant increase was observed in plasma globulin in the 20 M treatment (P<0.05). Conclusion: In summary, adding 20 μL/L myrcene to the transport water of common carp reduced hepatic enzyme levels and improved immune parameters, and therefore, the use of myrcene improves fish welfare during transportation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Acoustic technology has great application prospects in aquaculture. In particular, two indispensable, critical technologies for the future aquaculture industry are multi‐sensor acquisition that can achieve multi‐scale information fusion, collection and establishment of a global acoustic fish database and highly developed deep learning intelligent algorithms that can establish a correlation mechanism between fish acoustic and behaviour characteristics. Acoustic technology offers remarkable advantages in large and turbid water bodies for studying spatial and temporal distribution patterns of aquatic organism populations, developing on‐demand feeding systems and estimating biomass. This article reviews the development of acoustic technology and its application in aquaculture over the last 30 years. It further analyses, in detail, the advantages and disadvantages of acoustic technology in evaluating aquatic organism biomass and morphological and physical indicators, aquatic organism behaviour and welfare improvement. Challenges of acoustic technology in acquiring dynamic target data accurately, building a global acoustic fish database and establishing connections between fish behaviour and acoustic characteristics are also discussed. In brief, this article aims to help researchers and practitioners better understand the current state‐of‐the‐art acoustic technologies, which can provide strong support for smart aquaculture applications. [ABSTRACT FROM AUTHOR]

During the production of salmonids in aquaculture, it is common to observe growth-stunted individuals. The cause for the so-called “loser fish syndrome” is unclear, which needs further investigation. Here, we present and compare computer vision systems for the automatic detection and classification of loser fish in Atlantic salmon images taken in sea cages. We evaluated two end-to-end approaches (combined detection and classification) based on YoloV5 and YoloV7, and a two-stage approach based on transfer learning for detection and an ensemble of classifiers (e.g., linear perception, Adaline, C-support vector, K-nearest neighbours, and multi-layer perceptron) for classification. To our knowledge, the use of an ensemble of classifiers, considering consolidated classifiers proposed in the literature, has not been applied to this problem before. Classification entailed the assigning of every fish to a healthy and a loser class. The results of the automatic classification were compared to the reliability of human classification. The best-performing computer vision approach was based on YoloV7, which reached a precision score of 86.30%, a recall score of 71.75%, and an F1 score of 78.35%. YoloV5 presented a precision of 79.7%, while the two-stage approach reached a precision of 66.05%. Human classification had a substantial agreement strength (Fleiss’ Kappa score of 0.68), highlighting that evaluation by a human is subjective. Our proposed automatic detection and classification system will enable farmers and researchers to follow the abundance of losers throughout the production period. We provide our dataset of annotated salmon images for further research.

Abstract The live transport of farmed fish is an important practice in Chinese aquaculture due to consumer preferences in its domestic market. However, live transport can be stressful for fish and may cause many welfare issues. This study aimed to examine the effects of transport density on the welfare of largemouth bass (Micropterus salmoides). Adult fish were allocated to four experimental treatments in a two‐factor design (N = 5 groups per treatment). Factor one was stocking density of either 39 (low density) or 78 (high density) g L−1. Factor two was transport, with half of the fish groups exposed to simulated transport stress for 3 h using a motion platform, and the other half kept in static tanks for the same length of time. Baseline behavior and physiology were determined from a subset of fish after acclimation but before selection into groups and application of transport. To determine the effects of transport, stocking density, and their interaction on the experimental groups, physiological sampling and behavioral recording were carried out immediately after simulated transport, and water quality was measured both before and after transport. Changes in water quality were observed between two timepoints, with decreased dissolved oxygen levels and increased water temperature. Total ammonia nitrogen levels significantly increased in all treatments over time, particularly in the high‐density groups. Fish ventilation rates were significantly elevated in the groups kept at a high stocking density regardless of whether they also experienced transport stress. Fish transported at a high stocking density also showed more fear‐related behaviors such as freezing and thigmotaxis than non‐transported groups. Serum cortisol, catalase, and aspartate transaminase levels were significantly higher in the transported treatment groups compared to the baseline fish, but no difference was found for serum glucose, lactate, and glutathione peroxidase. We concluded that 3 h of simulated transport was stressful to largemouth bass kept at 78 g L−1, as evidenced by altered fish physiological and behavioral indicators of stress, as well as deteriorated water quality. Additionally, we identified a positive correlation between serum and skin mucus samples for cortisol, glucose, and lactate in transported fish, providing important information for developing less invasive methods for the welfare assessment of largemouth bass.

Society is becoming more demanding with aquaculture’s environmental footprint and animal wellbeing. In order to potentially mitigate these concerns, feed formulations could be based on eco-efficient (circular economy-driven) or organic ingredients. This study aimed to investigate the growth performance, feed utilization, and health status of juvenile Nile tilapia (Oreochromis niloticus) when fed with such feeds. The growth trial lasted for 8 weeks, and fish had an initial weight of 31.0 ± 0.5 g (mean ± SD). Fish were fed until visual satiation, in quadruplicate, with one of three isonitrogenous and isoenergetic experimental feeds: a commercial-like feed without fishmeal (PD), a diet based on ingredients compatible with organic certification (ORG), or a feed formulated using circular economy-driven subproducts and emergent ingredients (ECO). Fish fed ECO showed a tendency for decreased feed intake, while ORG fish significantly reduced their intake compared to those fed PD. Consequently, fish fed ECO (62.7 ± 5.4 g) exhibited almost half the growth than those fed PD (107.8 ± 6.1 g), while ORG fish almost did not increase their weight (32.7 ± 1.3 g). ECO and ORG diets had a lower digestibility for protein, lipid, and energy when compared to PD. Feed utilization of fish fed ECO or ORG was also lower than those fed PD. From the health-related genes analyzed, only glutathione reductase (gsr) showed statistically significant differences, being more expressed in fish-fed ECO than those fed PD. Thus, even when such novel formulations induced extreme effects on voluntary feed intake, their impact was noted only in fish growth, but not in robustness.

Aquafeed’s contamination by microplastics can pose a risk to fish health and quality since they can be absorbed by the gastrointestinal tract and translocate to different tissues. The liver acts as a retaining organ with the consequent triggering of oxidative stress response. The present study aimed to combine the use of natural astaxanthin with natural-based microcapsules to counteract these negative side effects. European seabass juveniles were fed diets containing commercially available fluorescent microplastic microbeads (1–5 μm; 50 mg/kg feed) alone or combined with microencapsulated astaxanthin (AX) (7 g/kg feed; tested for half or whole feeding trial—30 or 60 days, respectively). Fish from the different dietary treatments did not evidence variations in survival and growth performance and did not show pathological alterations at the intestinal level. However, the microplastics were absorbed at the intestinal level with a consequent translocation to the liver, leading, when provided solely, to sod1, sod2, and cat upregulation. Interestingly, the dietary implementation of microencapsulated AX led to a mitigation of oxidative stress. In addition, the microcapsules, due to their composition, promoted microplastic coagulation in the fish gut, limiting their absorption and accumulation in all the tissues analyzed. These results were supported by in vitro tests, which demonstrated that the microcapsules promoted microplastic coagula formation too large to be absorbed at the intestinal level and by the fact that the coagulated microplastics were released through the fish feces.

Live fish are in high demand all over the world, especially in China, where quality standards align with consumer preferences. In Kenya, discussions on live fish, particularly in aquaculture-rich regions, are focal points. However, the lack of a systematic approach to transporting live fish poses challenges for stakeholders. This research explores attitudes and perceptions of stakeholders in Kenya regarding the adoption and transportation of live fish, shedding light on transportation procedures and sector challenges. Using a descriptive research design, primary data were collected from diverse aquaculture stakeholders through a questionnaire, addressing their knowledge, perceptions, and attitudes toward live fish transportation in the country. The study unveils varied patterns of live fish transportation in Kenya, influenced by the purpose and distance. Private cars are prominent at 26.3%, with Nyanza and Mombasa leading at 35%. Modified vans are prevalent in Central-Nairobi and Western regions (25% and 22.5%, respectively), while public transport is widespread, especially in Central and Nairobi (25%). Purpose-built live fish vehicles dominate in Western and Nyanza (20% and 17.5%, respectively). Crustaceans like lobsters and crabs are primarily exported from the Coastal region (27.5%). Participants generally assessed their knowledge of live fish transportation as moderate, with a basic understanding of fish welfare. Feedback indicates common practices in live fish transport in Kenya as sealed tanks, plastic bags, and purpose-built vehicles. Temperature and oxygen fluctuations poses a significant challenge during transportation across all regions, particularly in Mombasa and Kisumu. The use of anaesthetics, especially for food fish, is infrequently reported. The study revealed favourable perceptions of stakeholders to live fish transportation and welfare, indicating early adoption. Further research is recommended on fish welfare, best management practices, technological advancements, and interdisciplinary studies to enhance the sustainability of live fish transportation sector and fish welfare in Kenya.

Finfishes are caught from the wild for food, feed (often in the form of fishmeal and oil) and bait. According to the Food and Agriculture Organisation of the United Nations (FAO), between 74 and 83 million tonnes (averaging 77 million tonnes) were caught annually in 2000–2019. Although fishes are now widely recognised as sentient beings, capture is still quantified as biomass rather than number of individuals (in contrast to wild-caught marine mammals and crocodiles; and farmed mammals and birds). Here, we estimate global numbers of wild-caught finfishes using FAO capture production (landing) tonnages (2000–2019 data) and estimates of mean individual weight at capture, based on internet-sourced capture and market weights. We estimate that between 1,100 and 2,200 billion (1.1–2.2 × 1012), or 1.1–2.2 trillion, wild finfishes were caught annually, on average, during 2000–2019. Anchoveta (Engraulis ringens) comprised 28%, by estimate midpoint. Estimated numbers in 2019, totalling 980–1,900 billion, were lower due to reduced anchoveta landings, but still represented 87.5% of vertebrate numbers killed for food or feed, as obtained or estimated from FAO data. These figures exclude unrecorded capture such as illegal fishing, discards and ghost fishing. Estimated finfish numbers used for reduction to fishmeal and oil represented 56% of the total 2010 estimate (1,000–1,900 billion), by midpoint. It is recommended that the FAO reports fish capture numbers. The welfare of wild-caught fishes, which is generally very poor during and after capture, should be addressed as part of sustainable utilisation of aquatic resources.

Ballan wrasse (Labrus bergylta) are commonly used as cleaner fish in salmon farms as a biological treatment to mitigate sea lice infestation. Improved welfare for cleaner fish both during production of these fish and when in sea-cages with salmon is crucial for the industry’s development. A common operational procedure in ballan wrasse production is transporting juveniles from one land-based farm to another for further on-growing. Episodes of increased mortality have been reported after such transportations. In this study, the relationship between transport stress and post-transport mortality at the on-growing facility was examined. It was also investigated if light sedation with AQUI-S® can mitigate stress during transport. Stress was quantified by measuring cortisol release rate to the tank water during transport. This was investigated in 10 commercial live carrier truck transports (6 without AQUI-S® sedation and 4 with sedation during loading and transport). The total time of transport varied between 12 and 21 h. In general, mortality was significantly higher (1.0 ± 0.6% day−1) the first five days post-transport compared to 15–20 days post transport (0.5% day−1). There was also a strong relationship between fish weight at transport and post-transport mortality, where higher mean weight at transport reduced mortality. In contrast to what was expected, AQUI-S® treatment during transport procedures increased cortisol excretion rate, suggesting a stimulating effect of AQUI-S® on the stress axis in ballan wrasse. Considering these results, the value of using AQUI-S® to reduce stress during transport of juvenile ballan wrasse might be questioned. However, there was no relationship between cortisol release rate during transport and post-transport mortality. Furthermore, this study emphasizes that water cortisol measurements can be used as a none-invasive tool for monitoring stress and can be integrated into the welfare evaluation during commercial fish transports.

Assessing the potential impacts of wind farm noise on fish is a crucial aspect of Environmental Impact Assessment (EIA) studies. There is increasing evidence of disturbances and effects on hearing and behavior in animals. The black rockfish (Sebastes schlegelii) is a commercially valuable rocky reef fish native to East Asia. However, empirical studies that measure the actual consequences are lacking. In this study, we used auditory evoked potentials (AEP) to assess the effects of dominant frequency noise emitted by offshore wind farms on the auditory sensitivity, hearing threshold, swimming, and feeding behavior of juvenile black rockfish. The experimental findings revealed that the most sensitive sound frequency was 200 Hz, with the lowest hearing threshold recorded at 86.4 ± 3.4 dB re 1 mPa. Following 3 and 7 days of exposure to 200 Hz noise at 110 dB, threshold shifts in black rockfish reached 19.0 dB and 13.3 dB, respectively. During the subsequent recovery phase, these shifts decreased to approximately 9.8 dB after 3 days, respectively. The noise-exposed group exhibited higher swimming duration, moving distance, and caudal fin swing frequency compared to the control group without noise exposure. Furthermore, noise prolonged the feeding rate of black rockfish. Our findings provide the first evidence of noiseinduced temporary threshold shift and behavioral disturbances in juvenile black rockfish, implying potential fitness consequences associated with noise pollutant. [ABSTRACT FROM AUTHOR]

Simple Summary: The development of aquaculture has led to an increased attention towards the welfare of farmed fish. Transportation, a routine procedure in this industry, can be stressful for fish due to handling, air exposure, confinement, and reduced oxygen levels. Therefore, it is crucial to gain insights into optimal practices for organizing transportation, ensuring the well-being of these animals and minimizing excessive stress. The objective of this study was to assess the stress response of meagre juveniles during commercial transport from Monfalcone to Stintino (Italy), which lasted 24 h. Welfare evaluation included measuring cortisol levels in muscle and assessing the potential cellular localization of oxidative stress markers in various organs and tissues. Significant increases in cortisol were observed in the fish during transfer from housing to transport tanks and in subsequent samplings at different phases of transport. This finding suggests that either the animals had insufficient time to recover or the transport conditions were suboptimal. However, in terms of oxidative stress, overall immunohistochemical analysis did not reveal variation in marker localization before and after transport, indicating that the stress experienced by the fish during transportation might have been relatively mild. In aquaculture, the transportation of live fish is a crucial but stress-inducing practice, necessitating a thorough understanding of its impact on fish welfare. This study aimed to assess the physiological stress response of meagre (Argyrosomus regius) juveniles during a 24 h commercial transport by quantifying muscle cortisol levels using a specific radioimmunoassay. Additionally, an immunohistochemical approach was used to detect and localize the cellular distribution of oxidative-stress-related biomarkers within various tissues and organs. The results demonstrated a significant increase in muscle cortisol levels following the loading procedure, remaining elevated above basal levels throughout the 24 h transport period. This effect may be attributed to either insufficient time for recovery from the loading stress or prolonged transportation-related stress. Immunostaining for all the antibodies we examined was observed in multiple tissues and organs, but we found no notable variations among the various transport phases. In conclusion, the observed stress response appears to be mainly linked to loading stress and the transport process itself, emphasizing the importance of implementing appropriate operational procedures to safeguard fish well-being during transport. Nonetheless, the unaltered distribution of oxidative stress markers between the control and transported groups suggests that the experienced stress might be within tolerable limits. [ABSTRACT FROM AUTHOR]