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Precisely analysing and optimising feeding regimes is central to salmonid growth performance and delivery of special diets. The current study developed novel video surveillance methods and analysis techniques to assess individual feed intake and minimum pellet intake (MPI) in individually identified juvenile rainbow trout, Oncorhynchus mykiss. Three trials were conducted to test the impact of short-term starvation (N=112 [16 tanks, 7 fish per tank], average weight=27.1±3.4g, age= 119 days), portion numbers per feeding (N=105 [15 tanks, 7 fish per tank], average weight=22.8±2.1g, age= 99 days) and varied numbers of daily feeding events (N=84 [12 tanks, 7 fish per tank], average weight=32.4±3.3g, age= 133 days). All trails were carried out in a recirculating aquaculture system with 20 tanks held at 15 ± 0.5°C. All individuals were code-tagged and high quality video images were taken and analysed to identify all feeding interactions. Individual trout feeding activity under different feeding regimes could be precisely analysed with the video methods developed. Moving from one to two daily feeding events doubled pellet intake per fish from 27.4 ± 5.8 to 52.8 ± 11.5 pellets. Pellet intake (58.8 ± 24.2 pellets) did not increase at three daily feeding events but became more variable across fish. MPI nearly doubled to 30 pellets in fish receiving two daily feeding events (MPI30: chi-squared = 8.74, df = 2, p = 0.01). Short-term starvation had no influence on intake (28 ± 8 pellets/fish) or MPI. Increasing portion number from one (27.8 ± 7.4 pellets fish−1) to two (31.1 ± 7.4 pellets fish−1) or more did not significantly increase the number of ingested pellets. Adjusting the feeding regime by increasing daily feeding events to two, possibly combined with multiple portions, can increase pellet intake and reduce the heteroscedasticity of pellet intake. The methods presented in this study are viable for analysing feeding regimes for juvenile rainbow trout and controlled feedstock/supplement delivery. Implications for analyses with other species and for vaccination optimisation are discussed. [ABSTRACT FROM AUTHOR]

A variety of tagging techniques are now available to monitor fish behaviour, physiology and their environmental experience. Tagging is frequently used in aquaculture research to monitor free‐swimming individuals within farmed populations. However, for information gathered from tagged fish to be representative of farmed populations, tagging must not fundamentally affect fish behaviour, physiology or survival. Here, we systematically review studies that used tags to monitor farmed fish behaviour and test factors that affect tag retrieval and tag‐related mortality. Most studies using tags assessed movement and swimming behaviour in salmonids, predominantly in Europe and North America. Mortality of tagged fish was 10 times higher in sea‐cages (mean = 25%, range = 0–61.5%, n = 22 studies) than in tanks (mean = 2.5%, range = 0–17%, n = 23 studies), while mortality of tagged fish in sea‐cages was markedly higher in longer trials (from 4% in single day trials to 36% after 100 days). Higher‐than‐usual mortality rates among tagged fish, together with largely unknown sublethal effects on behaviour, should caution against using tagging studies to make decisions related to farm management. Moreover, key metrics such as mortality rates of tagged and untagged fish or evidence of sublethal effects are often unreported. We make several recommendations to improve future tagging studies and increase transparency in reporting. A greater insight into the causes of tagged fish mortality in sea‐cages is required to secure animal welfare and data validity in studies that use tags to assess fish behaviour in aquaculture. [ABSTRACT FROM AUTHOR]

As a first attempt to assess bone health in cleaner fish production, wild and cultured ballan wrasse Labrus bergylta and lumpfish Cyclopterus lumpus were examined by radiology. In C. lumpus, wild fish (57%) had more vertebra deformities (≥1 deformed vertebrae) than cultured fish (2–16%). One wild C. lumpus had lordosis and another was missing the tail fin. In L. bergylta, wild fish (11%) had fewer vertebra deformities than cultured individuals (78–91%). Among the cultured L. bergylta, 17–53% of the fish had severe vertebra deformities (≥6 deformed vertebrae) with two predominate sites of location, one between vertebra 4 and 10 (S1) in the trunk, and one between 19 and 26 (S2) in the tail. Fusions dominated S1, while compressions dominated S2. Although wild L. bergylta had a low vertebra deformity level, 83% had calluses and 14% had fractures in haemal/neural spines and/or ribs. The site‐specific appearance and pathology of fracture and callus in wild L. bergylta suggests these are induced by chronic mechanical stress, and a possible pathogenesis for fish hyperostosis is presented based on this notion. In conclusion, good bone health was documented in cultured C. lumpus, but cultured L. bergylta suffered poor bone health. How this affects survival, growth, swimming abilities and welfare in cultured wrasse should be further investigated. Significance Statement: Skeletal deformities were studied in ballan wrasse and lumpfish of both wild and cultured origin for the first time to identify potential welfare issues when deploying them as cleaner fish in salmon sea cages. While cultured lumpfish showed good bone health, cultured wrasse had a high occurrence of vertebra deformities, which is expected to impact lice eating efficiency and animal welfare negatively. These deformities are most likely induced early in development. [ABSTRACT FROM AUTHOR]

The overall fish welfare in sea-caged European sea bass (Dicentrarchus labrax) was quantitatively assessed by adapting the Salmon Welfare Index Model (SWIM 1.0). In the model, a total of 16 operational welfare indicators in three segments (i) individual fish-based; (ii) fish-group specific; and (iii) sea cage environment-specific indicators were evaluated. In this study, the welfare indicators for salmon aquaculture which are incompatible with the characteristics of European sea bass were modified. Differently from SWIM 1.0, the welfare indicators of smoltification and salinity were eliminated; however, gill integrity and pH were added in the modified model of this study while the water temperature attributes were also changed in the model proposed. The modified model was tested for two sea cage farms of European sea bass (Farm A and Farm B) in two different locations of Mediterranean Sea for the first time. The overall welfare scores were expressed by a scale from 0-poor to 1-good welfare. The overall welfare assessment calculated by the model yielded the value of 1.0 and 0.81 for Farm A and Farm B, respectively. Based on the scores, Farm A represented the conditions of 'good welfare' while Farm B gave fair warning about welfare status. The methodology developed in the SWIM 1.0 model can be applied to European sea bass in Mediterranean aquaculture with small modifications. Salmon Welfare Index Model (SWIM 1.0) was utilised for E. sea bass welfare evaluation SWIM 1.0 was tested in sea-caged fish from two farms located in Mediterranean Sea SWIM 1.0 model can be applied to E. sea bass with small modifications [ABSTRACT FROM AUTHOR]

The literature on global trends in recreational fishing, the determinants of participation in recreational fishing, and the social embedding of recreational fishing in the public eye are reviewed across the world. Data support a conceptual life-cycle model of fisheries according to which interest in recreational fishing rises rapidly with economic development before leveling off and eventually declining. Participation in recreational angling across the globe varies substantially and is directly related to societal-level developments affecting resources, time, and socialization into fishing. Moreover, culture and the way that fish are historically situated within society appears to affect interest in fishing and the public perception of certain fishing practices. Across the more developed western countries, a sustained shift in public values from anthropocentric to more biocentric viewpoints is documented. This shift puts traditional fisheries management that manages ecosystems for optimal fishing experiences under increasing scrutiny and elevates biodiversity conservation toward a key goal of contemporary fisheries management in many countries. However, while a pro fish welfare discourse can be traced to almost all developed countries covered in this review, this does not mean the recreational activity is threatened or welfare-oriented regulations are widely implemented, with a few exceptions in selected countries. Public surveys conducted in mainly developed countries around the world instead reveal that people generally view recreational fisheries as an acceptable pastime. Major structural changes are occurring in many societies related to immigration, increasing ethnic and cultural diversity of populations, and social value change. Yet, little is known how these changes might affect recreational fishing participation and behavior, and the view of the general public toward fishing in the future. Panel research designs that repeatedly survey the public, and recreational fishers, will be needed to track value and participation changes over time, but such designs are rarely implemented in most countries that were reviewed in this work. Data gaps are particularly strong for Africa and large parts of Central and South America as well as Russia and Asia. [ABSTRACT FROM AUTHOR]

Fish welfare has become a significant concern during the last decade. The issue of slaughter is getting the interest of many consumer organizations and fish growers, and suppliers. We need to take careful consideration to food fish slaughtering, and not only for an ethical reason. Numerous quality traits are in place already at the end of fish life. Nonetheless, other traits can be developed while the post mortem muscles are turning into consumer produce. Therefore, it is necessary to investigate ways to avoid the suffering of the fish before their processing. To improve the efficiency of the immobilizing and stunning process of the fish at the entrance of the fish plant, we investigated the use of CO2 in combination with low temperature. When combining CO2 to 2°C water temperature, fish were stunned and permanently immobilized within 20 min or less, while their core temperature was 3°C. Our results suggest that combining low temperature and bubbling CO2 in the fish receiving tank of the processing plant might be more appropriate for animal welfare. Therefore, we suggest continuing our experiments in the fish processing plant. [ABSTRACT FROM AUTHOR]

Handling or transporting fish can strongly affect physiology and behaviour, and anaesthesia is often used to minimize stress or injuries. The potential of propofol as an immersion anaesthetic for Nile tilapia (Oreochromis niloticus) was investigated in this study. Nile tilapia were divided into groups based on a body mass criteria of 10, 50, 100, 150 and 200 g, and subjected to different propofol concentrations (2.5, 5, 7.5, 10 or 12.5 mg L−1) using 3 individuals per size class for each prepared anaesthetic solution. Fish were placed in the prepared anaesthetic baths and times to lose reflex to mild touch as well as induction of full immobilisation recorded. Behavioural markers such as loss of the righting reflex and respiratory responses were also monitored. Following the induction of full anaesthesia, blood samples were drawn from each of the 200 g fish for haematological analysis. Induction times for deep anaesthesia (Stage IV) decreased significantly (p < 0.05) with increasing propofol concentrations for all size classes and increased as a function of increasing fish size. Recovery from anaesthesia was smooth in all size classes and exposure to higher doses of anaesthesia resulted in a general trend of prolonged recovery times. Larger fish showed a general trend of faster recovery times than smaller fish under the different propofol concentrations. Besides reporting the practicality of propofol as an immersion anaesthetic, this study has also demonstrated the importance of considering size when anaesthetizing Nile tilapia with propofol.

Disease, pest control, and environmental factors such as water quality and carrying capacity limit growth of salmon production in existing farm areas. One way to circumvent such problems is to move production into more exposed locations with greater water exchange. Farming in exposed locations is better for the environment, but may carry unforeseen costs for the fish in those farms. Currents may be too strong, and waves may be too large with a negative impact on growth and profit for farmers and on fish welfare. This study employed two major fish monitoring methods to determine the ability of Atlantic Salmon (Salmo salar) to cope with wavy conditions in exposed farms. Echosounders were used to determine vertical distribution and horizontal preference of fish during different wave and current conditions as well as times of day. Video cameras were used to monitor shoal cohesion, swimming effort, and fish prevalence in locations of interest. The results indicate complex interacting effects of wave parameters, currents, and time of day on fish behaviour and vertical distribution. During the day, hydrodynamic conditions had stronger effects on vertical distribution than during the night. In weak currents, fish generally moved further down in taller waves, but stronger currents generally caused fish to move upwards regardless of wave conditions. Long period waves had unpredictable effects on vertical distribution with fish sometimes seeking deeper water and other times moving up to shallower water. It is unclear how much the cage bottom restricted vertical distribution and whether movement upwards in the water columns was related to cage deformation. In extreme cases, waves can reach below the bottom of a salmon cage, preventing fish from moving below the waves and cage deformation could exacerbate this situation. Farmers ought to take into consideration the many interacting effects on salmon behaviour within a cage as well as the potential for cage deformation when they design their farms for highly exposed locations. This will ensure that salmon are able to cope when storms and strong currents hit at the same time.

We performed field measurements of the behavioral changes in cultured chub mackerel (Scomber japonicus) caused by tide-induced changes in the shapes of their small-sized tetragonal fish cages. The field measurements were conducted in two separate periods: neap tide, a period in which the shape of the fish cages was stable; and spring tide, a period in which the fish cages are significantly deformed, which was expected to have significant influences on fish behavior. In the spring tide, the cages were deformed greatly by the moving water, with different water velocities affecting the cages to different degrees; the volume loss was estimated at 4.9% and 7.3% for v = 0.114 m/s and v = 0.221 m/s, respectively. The fish exhibited significantly different behaviors between the neap tide and spring tide. During the neap tide, the fish remained in the lower part of the cage, but during the spring tide they made frequent upward and downward movements, and their horizontal distribution changed significantly due to the changes in the shape of the cage. The cage deformation during the spring tide greatly influenced the swimming behavior of fish.

Globally, it is estimated that around 10% of the fish that are caught are discarded. This is considered to be a wasteful human marine activity since these fish are often dead or dying. To reduce the high discard rates of commercial fisheries, the European Union (E.U.) has enacted a landing obligation that includes the ability to exempt “species for which scientific evidence demonstrates high survival rates”. Therefore, discard survival studies (henceforth DSSs) have become one of the most politically prioritized fisheries research areas in European fisheries. International expert groups have produced guidance reports to promote best practices and to harmonize the methodologies. Nevertheless, there has not been any focus on how to implement animal welfare (AW) regulations experimentally. Discard survival studies are “frontrunners” in fisheries science research areas that are embedded by animal research welfare requirements and are expected to be more restrictive in the future because of an increased public focus on fish welfare. This paper focuses on AW regulations in relation to conducting DSSs, but the outreach is much broader. We investigate experimental procedures by bringing in relevant examples, using output results, and relating this information to relevant AW guidelines and regulations by focusing on implementing 3R principles.

In aquaculture, fish species may experience stressful episodes caused by poor farming conditions. The exponential increase of global aquaculture has raised the number of research studies aimed at demonstrating the sensitivity of aquatic animals in confined environments. The development of a real-time PCR and immunohistochemistry methods were investigated to evaluate the presence, localization, and quantity of biomarkers of oxidative stress in European sea bass (Dicentrarchus labrax). In particular, stress tests such as manipulation and temperature changes were conducted through molecular methods to identify the expression level of heat shock protein 70 (HSP70) in stressed animals compared with a control group. The immunohistochemical technique was also applied to locate and study the trends-levels of nitrotyrosine (NT), heat shock protein 70 (HSP70), malondialdehyde (MDA), and 4-hydroxy-2-nonenal (HNE) in different tissues from stressed animals and control group. The presence of the rodlet cell (RCs) was evaluated by histology in both a control and stressed group. Our results show that the real-time PCR method developed is specific for the evaluated target gene and that manipulation and temperature increase are strong stressors for animals. Relative quantification data revealed a gene expression increase of HSP70 in the stressed group of animals compared to the control group. The antibodies used for the immunohistochemical staining were efficient, and it was possible to appreciate the increase of immunoprecipitates in European sea bass either manipulated or stressed by temperature increase. The present study can be a starting point to allow the quantification of HSP70 and the identification of other stress biomarkers in D. labrax. [ABSTRACT FROM AUTHOR]

Aquaculture sustainability and profit is highly dependent on good welfare for farmed fish including the economically important species Atlantic salmon (Salmo salar). Welfare is closely linked to stress, as prolonged stressful farming conditions can translate into reduced performance and health. Understanding how Atlantic salmon responds to aquaculture‐related stressors has for the past years been a key focus area of research. Present review evaluates the current state of the art by assessing a defined panel of 13 recent articles on the topic. Particular attention is paid to methodological approaches and challenges in investigating chronic stress effects. Stress experiments are performed in profoundly different ways based on scientific interest, and applied stressors range from environmental challenges, for example water quality, to management‐related practices and dietary stress. We show that majority of studies are limited to analysis at the transcriptional level. Quantitative reverse transcription PCR (RT‐qPCR) is the dominating technology, followed by microarray assays. Post‐translational studies are rare, and correlations between changes in transcript expressions and protein levels are generally not explored. We encourage future research to address this knowledge gap, as insight on proteome status may unravel more long‐standing physiological mechanisms towards stress, for example tertiary effects, that can only be postulated by transcriptional analyses. Attention should also be paid to regulatory mechanisms operating on pre‐ and post‐translational levels, for example microRNAs, which may be affected by environmental challenges and play roles in modifying stress responses. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Disease, pest control, and environmental factors such as water quality and carrying capacity limit growth of salmon production in existing farm areas. One way to circumvent such problems is to move production into more exposed locations with greater water exchange. Farming in exposed locations is better for the environment, but may carry unforeseen costs for the fish in those farms. Currents may be too strong, and waves may be too large with a negative impact on growth and profit for farmers and on fish welfare. This study employed two major fish monitoring methods to determine the ability of Atlantic Salmon (Salmo salar) to cope with wavy conditions in exposed farms. Echosounders were used to determine vertical distribution and horizontal preference of fish during different wave and current conditions as well as times of day. Video cameras were used to monitor shoal cohesion, swimming effort, and fish prevalence in locations of interest. The results indicate complex interacting effects of wave parameters, currents, and time of day on fish behaviour and vertical distribution. During the day, hydrodynamic conditions had stronger effects on vertical distribution than during the night. In weak currents, fish generally moved further down in taller waves, but stronger currents generally caused fish to move upwards regardless of wave conditions. Long period waves had unpredictable effects on vertical distribution with fish sometimes seeking deeper water and other times moving up to shallower water. It is unclear how much the cage bottom restricted vertical distribution and whether movement upwards in the water columns was related to cage deformation. In extreme cases, waves can reach below the bottom of a salmon cage, preventing fish from moving below the waves and cage deformation could exacerbate this situation. Farmers ought to take into consideration the many interacting effects on salmon behaviour within a cage as well as the potential for cage deformation when they design their farms for highly exposed locations. This will ensure that salmon are able to cope when storms and strong currents hit at the same time. [ABSTRACT FROM AUTHOR]

Aquaculture is an industrial activity that not only aims to be a source of quality food, but also is a way to restock fish populations and to conserve the biodiversity of our oceans. On the other hand, the production system can influence the consumer perceptions about what is purchased and consumed, as well as the subsequent environmental and social effects. Fish feeding production is affected by the growth of aquaculture and the increasing demand that have let to deficit, high prices, and low ecological safety of fish meal and oil. In this regard, the use of microbial biomass obtained from a variety of microorganisms has been reported as a potential substitute for plant- and animal-derived ingredients, satisfying the requirements in protein and energy and even adding functional properties. In addition, microalgae can increase the nutritional value of animal feed, play a key role in the physiological growth and external appearance of aquatic animals. Finally, politicians, industry and society in general should be careful with the numerous uncertainties still present in the sector that can weaken its sustainability from environmental, social and economic perspectives. [ABSTRACT FROM AUTHOR]

Touch pools are popular open-topped fish tanks often found in aquariums where visitors may interact with animals, by touching and sometimes even feeding them, for educational and recreational purposes. However, although animal interactions are becoming increasingly popular in recent years, the welfare impact on the animals and the educational effectiveness of such interactions is under debate. Awareness concerning the different, and sometimes controversial, aspects connected with such interactions has spread. The aim of this paper is to investigate the ethical issues arising from the presence of touch pools in aquariums and facilities alike. In particular, possible sources of moral conflicts between five interested parties will be identified and discussed: biodiversity; aquariums; staff involved with touch pools; individual animals used in the touch pools; visitors interacting with animals in touch pools. In order to assess the framework of ethical demands from different parties, it will be used an analytical tool provided by a revised version of the Ethical Matrix. [ABSTRACT FROM AUTHOR]

The role of cognitive factors in triggering the stress response is well established in humans and mammals (aka cognitive appraisal theory) but very seldom studied in other vertebrate taxa. Predictability is a key factor of the cognitive evaluation of stimuli. In this study, we tested the effects of stressor predictability on behavioral, physiological and neuromolecular responses in the European sea bass (Dicentrarchus labrax). Groups of four fish were exposed to a predictable (signalled) or unpredictable (unsignalled) stressor. Stressor predictability elicited a lower behavioural response and reduced cortisol levels. Using the expression of immediate early genes (c-fos, egr-1, bdnf and npas4) as markers of neuronal activity, we monitored the activity of three sea bass brain regions known to be implicated in stressor appraisal: the dorsomedian telencephalon, Dm (putative homologue of the pallial amygdala); and the dorsal (Dld) and ventral (Dlv) subareas of the dorsolateral telencephalon (putative homologue of the hippocampus). The activity of both the Dm and Dlv significantly responded to stressor predictability, suggesting an evolutionarily conserved role of these two brain regions in information processing related to stressor appraisal. These results indicate that stressor predictability plays a key role in the activation of the stress response in a teleost fish, hence highlighting the role of cognitive processes in fish stress. [ABSTRACT FROM AUTHOR]

We investigated the effects of plant density on the welfare of African catfish, Clarias gariepinus, in coupled aquaponics over 85 days. The moderate density (mpd) of basil, Ocimum basilicum, was compared with the high density (hpd) and control (n = 0). The behavior was analyzed by visual and video observations, and after the application of induced stressors, skin injuries, blood glucose, lactate, and plasma cortisol responses were considered. The hpd fish showed the least activity (control: visual 77.8%, video 81.6%; mpd: 74.6%, 82.6%; hpd: 63.2% [p < 0.05], 78.8%). High agonistic behavior (control: 5, 131; mpd: 4, 57; hpd: 1, 45) and the highest number of injuries (control: 3.9; mpd: 2.9; hpd: 3.4) were observed in the control. Glucose and lactate levels did not differ significantly (control: 5.5, 2.6 mmol/L; mpd: 5.6, 2.7 mmol/L; hpd: 5.3, 2.6 mmol/L); however, cortisol levels did (control: 18.8 ng/mL, mpd: 19.9 ng/mL, hpd: 25.8 ng/mL). pH adjustment led to additional stress, resulting in temporal cortisol alterations. While in the control and mpd, low cortisol levels were followed by acute responses and downregulation, the hpd fish showed prior elevation and lagged an acute response. However, comparing injuries and behavioral patterns with control, aquaponics with high basil density influenced African catfish positively. [ABSTRACT FROM AUTHOR]

Environmental enrichment (EE) has been generally accepted as an effective and promising way to enhance the performance and improve the welfare of animals kept in captivity. Evidence for the effects of EE on fish has accumulated rapidly, but little is known about its underlying mechanisms. In this study, black sea bream (Acanthopagrus schlegelii) were reared under enriched and enrichment-free conditions for 30 (post-larval) and 60 (juvenile) days. Physiological, transcriptome, and metabolome data were compared to investigate potential rearing improvements, physiological responses to acute stress, and the underlying mechanisms. The results showed that fish reared under enriched conditions had significantly better growth performance, a higher survival rate, and lower basal cortisol levels. Meanwhile, the cortisol, lactic acid, malondialdehyde (MDA), and total antioxidant capacity (T-AOC) levels in fish subjected to acute stress suggested that EE-reared individuals presented greater stress resistance. However, the effect of EE may decrease with the extension of treatment time for larger fish. The transcriptome analysis showed that energy-related pathways (including oxidative phosphorylation, the citrate cycle, and glycolysis/gluconeogenesis) as well as protein folding, sorting, and degradation-related pathways (protein processing in the endoplasmic reticulum and proteasome pathways); replication and repair related pathways (including pathways involved in nucleotide excision repair, base excision repair, mismatch repair, and homologous recombination); and immune-related pathways (complement and coagulation cascades pathway and the IL-17 signaling pathway) were significantly altered in the EE-reared individuals. In addition, integrated analysis of metabolome and transcriptome data revealed marked enrichment of transcription-associated metabolites involved in cortisol synthesis and secretion, taste transduction, olfactory transduction, and protein digestion and absorption pathways. Our results suggested that EE may influence the growth, fitness, and stress resistance of A. schlegelii by regulating a series of biological processes including energy metabolism, cortisol synthesis, antioxidant enzyme activities, protein folding, DNA replication and repair, and complement and coagulation cascades. [Display omitted] • Environmental enrichment (EE) enhanced growth and survival rate of black sea bream. • Effect of EE was compared by physiological, transcriptomic and metabolomic analysis. • EE affects growth by regulating nutrition intake and energy metabolism related genes. • EE affects process of cortisol synthesis, antioxidant activity and immune regulation. • Effects of EE diminished with the extension of treatment time when fish grew bigger. [ABSTRACT FROM AUTHOR]

This document is a corrigendum for an article titled "Does sedation with AQUI-S® mitigate transport stress and post transport mortality in ballan wrasse (Labrus bergyltae)?" The corrigendum acknowledges an error in the original article regarding the citation of references in the text. The correction has been made to the discussion section of the article. The authors apologize for the error and state that it does not affect the scientific conclusions of the article. The corrigendum also includes a note from the publisher stating that the claims expressed in the article are solely those of the authors and do not necessarily represent the views of their affiliated organizations or the publisher. [Extracted from the article]

Cryoanesthesia is a low-cost procedure that has advantages for use in fish, however, there are only a few studies dealing with the electrophysiological evaluation and its safety-related aspects. The relationship between behavior and electrocardiographic activity allows for the monitoring of functional changes in cardiac activity in fish submitted to low temperatures. This study aimed to describe the behavior and cardiac effects of cryoanesthesia in juvenile tambaqui (Colossoma macropomum) through electrocardiographic assessment. For this purpose, 27 juveniles of tambaqui (28.9 ± 4.2 g) were used and essayed into two experiments. Experiment 1: behavioral evaluation (n = 9) and Experiment 2: electrocardiographic recordings with control group (n = 9), and fish submitted to water at 5 °C in baths followed by subsequent recovery at a temperature of 26 ± 2 °C (n = 9). Each cardiac activity recording lasted 1200 s, after which fish were immediately transferred to a bath in water at 26 ± 2 °C, for 600 s. Heart rate, QRS amplitude, QRS complex duration and RR, PQ and QT intervals were analyzed. The results showed that four tracing patterns emerged which characterized the induction phases of cryoanesthesia throughout exposure to water at 5 °C. In phase 1, there was a decrease in the amplitude of the QRS complex. In phase 2, there was an increase in the amplitude of the QRS complex and maintenance of sinus rhythm. Phase 3 showed a gradual loss of cardiac function with the onset of an atrioventricular blockade. In phase 4, a cardiac arrest occurred, albeit reversible. Heart rate decreased as exposure time was longer at low temperatures. The fish recovered completely from cryoanesthesia after the increase in temperature, showing normal heartbeats, and QRS complex duration, QT, RR, and HR intervals being restored with maintenance of sinus rhythm, indicating recovery of fish hemodynamics. Overall, tambaqui juveniles at 5 °C showed a time-dependent and gradual reduction of motor activity with loss of postural reflex and immobility. Cardiac response was a function of temperature and progressed to a reversible cardiac arrest. During recovery, stages similar to those of induction were observed, but in the opposite direction, until recovery of the postural reflex. Cryoanesthesia can be used as an alternative method for the immobilization of C. macropomum. • This is the first study showing the ECG effects of cryonesthesia in C. macropomum. • The C. macropomum cardiac response was a function of temperature and progressed to a reversible cardiac arrest. • The fish recovered completely from cryoanesthesia after the increase in temperature. • Cryoanesthesia can be used as an alternative method for immobilizing C. macropomum. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of two stunning/slaughtering methods, percussion vs. immersion in cold saline (−6 °C, 5% NaCl) water, on stress status and freshness evolution in rainbow trout (Oncorhynchus mykiss). Stress indicators (cortisol, malondialdehyde-MDA) were measured in plasma, muscle, fin and skin mucus of 30 fish (15 per treatment), while freshness evolution and quality (pH, rigor mortis index, fillet and skin colour, and muscle texture) were assessed in 70 fish (whole fish and fillets; 35 per treatment) at 3, 48, 168, and 264 h of storage. Compared with percussion, cold immersion resulted in lower cortisol levels in skin mucus (−58%; P < 0.001), muscle (−53%; P < 0.01), and fin (−51%; P < 0.01), and higher muscle MDA (+90%; P < 0.001), while cortisol (184 ng/ml, on average) and MDA (13.7 nmol/mg protein) of plasma were not affected. Skin colour was darker in fish subjected to cold immersion compared with percussion. As for fillet, no differences were found in pH (6.46), L* (47.3), a* (−0.89), b* (10.1), TVB-N (17.6 mg/100 g of fillet), fatty acid profile, or texture, where only chewiness was higher (+28% and + 32% for whole fish and fillet, respectively; P < 0.05) when cold immersion was used compared with percussion. Over time, TVB-N showed the highest value at 264 h of storage (26.5 mg/100 g of fillet), and pH decreased from 6.57 at 3 h of storage to 6.39 at 48 h and 6.37 at 168 h, before increasing to 6.50 at 264 h (P < 0.001). Immersion in cold saline water was proved to be a viable alternative to percussion for stunning/slaughtering rainbow trout, being an ease technique, cost-effective, and with reduced labour, while producing a similar stress response amplitude and no relevant changes on product quality. • Immersion in cold saline water was compared with percussion. • Cold immersion affected onset and evolution of rigor mortis during the first 48 h. • The stunning/slaughtering methods differently affected plasma cortisol levels. • Cold immersion reduced cortisol in fin, muscle and skin mucus. • The stunning/slaughtering method scarcely affected fillet quality. [ABSTRACT FROM AUTHOR]

Animal welfare science recognizes fish as sentient beings capable of experiencing pain, stress, and various emotions. As social interactions and mutual relationships are essential for fish welfare, the social environment in aquacultures is important for fish welfare. Pigmentation influences fish social behavior, e.g., communication and/or shoaling behavior. We investigated how pigmentation and shoal phenotypic composition affect locomotor activity in relation to feeding, exploratory behavior, sheltering and lateralization in holding tanks and Y-mazes in pigmented and albino Bronze Corydoras (Corydoras aeneus). The fish were divided into three treatment groups: pigm only, alb only, and mix groups. Each group comprised 12 shoals, with a total of 288 fish distributed across 36 shoals, each containing eight individuals. The study revealed behavioral differences between fish with pigmented and albino phenotypes, both within and among shoals. For both phenotypes, an increase in locomotor activity before feeding was followed by a decrease in activity after food consumption, indicating an anticipatory response and a shift from foraging to postfeeding behavior. In the mixed shoals, pigmented fish exhibited greater activity and sheltering behavior than albino fish. Both albino and pigmented fish showed lateralization toward the right arm of the Y-maze; however, in the mixed shoals, the preference for the right arm was not significant. Albino fish reached the shelter at the end of the Y-maze more often; however, in the mixed shoals, albino fish maintained their success rate in exploring the maze, while pigmented fish showed an increased success rate. We emphasize the significance of considering phenotypic variation and shoal composition when evaluating fish behavior and welfare. Such insights can inform the management of practices in aquaculture and ornamental breeding to ensure optimal fish welfare and enhance their overall quality of life. [Display omitted] • Variations in pigmentation affect locomotor activity, exploratory behavior, hiding and lateralisation. • The behavior of pigmented and albino fish phenotypes differs • Albinos are more likely to face reduced welfare conditions [ABSTRACT FROM AUTHOR]

Cardiovascular diseases such as coronary arteriosclerosis are widespread and constitute severe health and welfare problems for both farmed and wild salmonid fish. However, effective tools for rapid screening and analysing heart diseases in fish do not currently exist. Electrocardiogram (ECG) recordings are widely used for screening and diagnosing numerous cardiac pathologies in humans, but the use of ECG techniques to diagnose and characterize cardiac abnormalities in fish is still in its infancy. In this study, we induced myocardial ischemia in anaesthetized rainbow trout by surgical coronary artery ligation. Additionally, we experimentally manipulated the fish's heart rate and environmental oxygen availability by altering gill water flow and oxygen saturation (i.e. , no flow, normoxic flow and hyperoxic flow), and analyzed changes in the ECG profile in detail. The main ECG abnormalities observed in fish with ligated coronaries in normoxia were atrioventricular blocks, prolonged QRS duration, reduced QRS amplitude and changes in the ST-segment such as the presence of early repolarization pattern. Furthermore, when gill water flow was stopped, fish exhibited pronounced hypoxic bradycardia, which alleviated all ECG abnormalities in coronary ligated fish. This is the first study to provide a detailed characterization of electrocardiographic markers of myocardial ischemia in fish. Our study shows that hypoxic bradycardia improves cardiac electrical conductivity, presumably by reducing mismatches in myocardial oxygen supply and demand. Yet, the importance of avoiding hypoxic bradycardia in experimental and biomedical studies on anaesthetized fish is highlighted as it can potentially lead to incorrect ECG interpretations. • Electrocardiogram (ECG) is suitable for detecting myocardial ischemia in trout. • ECG changes included heart block, low QRS amplitude and abnormal ST-segment. • The fish's heart rate significantly impacted the extent of ECG abnormalities. • ECG abnormalities were unmasked during tachycardia but improved during bradycardia. • Bradycardia alleviates ECG abnormalities by decreasing myocardial oxygen demand. [ABSTRACT FROM AUTHOR]

Probiotics for freshwater fish farming can be administered as single or multiple mixtures. The expected benefits of probiotics include disease prophylaxis, improved growth, and feed conversion parameters, such as the feed conversion rate (FCR) and specific growth rate (SGR). In the current work, we review the impact of probiotics on freshwater finfish aquaculture. Data were gathered from articles published during the last decade that examined the effects of probiotics on fish growth, FCR, and water quality in freshwater fishponds/tanks. While the expected benefits of probiotics are significant, the reviewed data indicate a range in the level of effects, with an average reduction in ammonia of 50.7%, SGR increase of 17.1%, and FCR decrease of 10.7%. Despite the variability in the reported benefits, probiotics appear to offer a practical solution for sustainable freshwater aquaculture. Disease prophylaxis with probiotics can reduce the need for antibiotics and maintain gut health and feed conversion. Considering that fish feed and waste are two significant parameters of the aquaculture ecological footprint, it can be argued that probiotics can contribute to reducing the environmental impact of aquaculture. In this direction, it would be beneficial if more researchers incorporated water quality parameters in future aquaculture research and protocols to minimize aquaculture’s environmental impact.

China is the largest food fish producer in the world. Chinese consumers normally purchase fish that are still alive to ensure freshness. Therefore, the live transport of fish is important in China’s aquaculture, although it carries potential risks for animal welfare. This study investigated the attitudes and knowledge of stakeholders within Chinese aquaculture towards the live transport and welfare of fish. Semi-structured interviews were conducted with 12 participants who were involved with the aquaculture industry in China. Most participants self-rated their transport-related knowledge as moderate and had some understanding of animal welfare, although this term was generally considered only relevant to terrestrial animals. Participants’ responses indicated that the live transport of fish occurs frequently in China, generally using sealed tanks, plastic bags, and foam boxes, in purpose-built vehicles. Seasonal changes, such as changes in ambient and water temperature, are considered to be important contributors to successful live transport, as well as sufficient oxygen supplies and stocking density. The use of anesthetics was not commonly reported, particularly in food fish, and fish capture is predominantly by conventional dipnets. The health status of transported fish is determined mostly by morphology (body injury, body or eye color, and fin condition), as well as vigor and swimming ability. Our results indicate that live transport poses a number of welfare risks to fish but that participants in the process associated welfare concerns more with terrestrial animals, not fish.

Fish are the most exploited, forgotten and misunderstood animals on the planet. They also are extraordinary creatures: complex, intelligent, sensitive, curious, and some of them have amazing abilities. For instance; some use tools, have a good memory, or collaborate to hunt. And most importantly, they are sentient, and they feel pain. Aquaculture has become the main supplier of fish worldwide, accounting for just over half of the fish eaten by humans due to static global wild-capture stocks, which have been overfished for decades. Also, global consumption of fish has doubled since the early 1970s and will continue to grow with population growth in the developing world. However, the aquaculture industry has developed without proper consideration of the needs of the fish species farmed, and the welfare consequences for those animals. Moreover, the rapid growth of aquaculture has raises major sustainability concerns due to its continued reliance on wild-caught fish. Annually, 0.5-1.0 trillion fish are caught to be reduced to ingredients to feed farmed animals, mainly fish. When considering the negative environmental consequences of using wild-caught fish as feed, we must not overlook the huge animal welfare impact that represents for the huge number of animals involved. Compassion in World Farming is working to raise awareness about fish sentience and the welfare problems that aquaculture industry represents for fish welfare. The way that fish are treated is important and we must do it better.

Integration of technological solutions aims to improve accuracy, precision and repeatability in farming operations, and biosensor devices are increasingly used for understanding basic biology during livestock production. The aim of this study was to design and validate a miniaturized tri-axial accelerometer for non-invasive monitoring of farmed fish with re-programmable schedule protocols. The current device (AE-FishBIT v.1s) is a small (14 mm × 7 mm × 7 mm), stand-alone system with a total mass of 600 mg, which allows monitoring animals from 30 to 35 g onwards. The device was attached to the operculum of gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax) juveniles for monitoring their physical activity by measurements of movement accelerations in x- and y-axes, while records of operculum beats (z-axis) served as a measurement of respiratory frequency. Data post-processing of exercised fish in swimming test chambers revealed an exponential increase of fish accelerations with the increase of fish speed from 1 body-length to 4 body-lengths per second, while a close relationship between oxygen consumption (MO2) and opercular frequency was consistently found. Preliminary tests in free-swimming fish kept in rearing tanks also showed that device data recording was able to detect changes in daily fish activity. The usefulness of low computational load for data pre-processing with on-board algorithms was verified from low to submaximal exercise, increasing this procedure the autonomy of the system up to 6 h of data recording with different programmable schedules. Visual observations regarding tissue damage, feeding behavior and circulating levels of stress markers (cortisol, glucose, and lactate) did not reveal at short term a negative impact of device tagging. Reduced plasma levels of triglycerides revealed a transient inhibition of feed intake in small fish (sea bream 50–90 g, sea bass 100–200 g), but this disturbance was not detected in larger fish. All this considered together is the proof of concept that miniaturized devices are suitable for non-invasive and reliable metabolic phenotyping of farmed fish to improve their overall performance and welfare. Further work is underway for improving the attachment procedure and the full device packaging.

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 × 10 12 ), 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., Competing Interests: None., (© The Author(s) 2024.)

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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Calabrese, Jonassen, Steigum, Åsnes, Imsland, Saude, Wergeland and Höglund.)

Intraspecific aggression is detrimental to body/fin damage, physiological stress, and other problems in aquaculture. Environmental enrichment has been proposed to have positive effects on fish aggressive behavior, physiological stress, and fish welfare, but there are mixed results. Here, we examine the impact of physical enrichment levels (i.e., the intensity of physical enrichment) on aggression in black rockfish (Sebastes schlegelii) and fat greenling (Hexagrammos otakii). Generally, with the increase in the enrichment level, the frequency of the aggressive behavior of black rockfish gradually decreased. In contrast, a non-monotonous effect of the enrichment level on aggression was observed for fat greenling, with low and intermediate levels leading to no or more aggression, while a high enrichment level reduced aggression. After three days, the high-level enrichment groups in both rockfish and greenling reached social stability (i.e., a relatively stable social structure indicated by lower aggression), while aggression in the other groups continued increased. These results show the significant regulatory effect of enrichment levels on the aggressive behavior in both black rockfish and fat greenling. This study may promote the development of environmental enrichment measures, and it provides useful information for reducing fish aggression and improving fish welfare in aquaculture.

We compared preferences shown by zebrafish Danio rerio and three‐spined stickleback Gasterosteus aculeatus for shelter provided by above‐tank shade and artificial plants. Zebrafish showed no preference for either shelter, whereas sticklebacks showed a preference for both shelter types over open areas and for shade over plants. Our results suggest shade may be used as enrichment for captive fish and re‐emphasise the importance of species‐specific welfare considerations. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of harvest practices and slaughter method on stress, quality and shelf life of whole fish (gilthead sea bream, European sea bass and red sea bream) towards the development of a humane slaughter practice. The use of hook and line resulted in significantly lower plasma cortisol and glucose in European sea bass and gilthead sea bream. Water temperature at harvest affected significantly the concentrations of stress indicators (plasma cortisol and glucose), mainly in European sea bass and gilthead sea bream. No significant differences were observed between the harvesting methods, regarding fish appearance, microbial spoilage and sensory scoring and subsequently shelf life. However, significantly lower hardness was recorded in fish harvested using the electric stunner, compared to the fish killed with slurry ice of the same harvesting period. Shelf life ranged between 13–18 days for gilthead seabream, 10–16 days for European sea bass and 10–14 days for red sea bream, depending on harvesting period. [ABSTRACT FROM AUTHOR]

This study investigated the anaesthetic potential of the essential oil from the leaves of Piper divaricatum (EOPD) through evaluation of the behaviour and electromyographic (EMG) recordings from the fish Colossoma macropomum which was used as an animal model. Initially, fish (3.9 ± 0.3 g; 6.4 ± 0.49 cm, total length) were subjected to short-term anaesthetic baths in five different concentrations of the EOPD: 25, 30, 35, 40 and 45 μL.L−1 to record the latencies for deep anaesthesia and recovery. Ten fish per concentration were used (n = 10) and each animal was considered a replicate and used only once. Thereafter, for the evaluation of EMG, fish (5.6 ± 1.8 g; 8.7 ± 0.52 cm, total length) were assigned to the following groups: a) sham control (basal recordings) and b) fish exposed to the EOPD at 40 μL.L−1 and subsequent recovery in anaesthetic-free water. Nine fish per analysis (n = 9) were used. The EOPD presented a high concentration of methyleugenol (71.36%) and prompted immediate behavioural changes in fish. Initially, hyperactivity was observed, followed by loss of the righting reflex and full body immobilization. All concentrations tested were capable to promote an anaesthetic-like state in tambaqui, with 40 μL.L−1 being the minimal concentration necessary to induce a rapid immobilization, i.e. < 3 min. The EMG showed a marked and reversible myorelaxation effect, confirming this oil as an indisputable muscle relaxant agent. The EOPD was capable of promoting a general anaesthesia-like state, with complete body immobilization of Colossoma macropomum at all concentrations tested. Gradual increases in frequency and amplitude of EMG tracings confirm the reversibility and uneventful resumption of normal swimming behaviour observed during recovery. Our results underscore the anaesthetic potential and myorelaxant effects of Piper divaricatum essential oil. • This is the first study to report the Piper divaricatum essential oil as an anaesthetic for fish. • All concentrations tested induced full body immobilization and loss of the righting reflex in Colossoma macropomum. • P. divaricatum essential oil dampened skeletal muscle contraction power in C. macropomum. [ABSTRACT FROM AUTHOR]

• Ballan wrasse is a widespread cleaner fish species in Atlantic salmon aquaculture. • Swim tunnel respirometry was performed at a range of acclimation temperatures on ballan wrasse. • Aerobic scope increased steadily from 5 to 25 °C, but was low compared to in salmon. • Critical swimming speed was only obtained at 25 °C as 1.1 body lengths s−1. • Ballan wrasse may suffer poor welfare in cold and strong current farm environments. Ballan wrasse (Labrus bergylta) are used extensively as cleaner fish to control salmon lice (Lepeophtheirus salmonis) infestations in the Atlantic salmon (Salmon salar) aquaculture industry. Fish are either cultured or caught in the wild before being transferred to salmon sea cages. Ballan wrasse are a poorly studied species, and fundamental knowledge of physiological performances and environmental limits are therefore needed for better deployment strategies and to predict when animal welfare may be at risk. We acclimated ballan wrasse for a minimum of 2 weeks to 5, 10, 15, 20 and 25 °C, representing the full range of temperatures wrasse may experience in salmon sea cages. Swim tunnel respirometry was performed at each temperature to measure standard and maximum metabolic rates, aerobic scope, and critical swimming speed (U crit). No mortalities occurred at any acclimation temperature. However, fish were generally inactive at lower temperatures, as evidenced by low metabolic rates. It was not possible to stimulate fish to swim continuously between 5 and 20 °C, and U crit was only obtained at 25 °C as 27 cm s−1 (1.1 body lengths s−1). The aerobic scope increased throughout the thermal interval tested from 129 ± 7 mg O 2 kg−1 h−1 at 5 °C to 265 ± 18 mg O 2 kg−1 h−1 at 25 °C. Owing to weak swimming capabilities, ballan wrasse deployment at locations with moderate to strong current speeds will likely result in poor welfare. Low metabolic rates and inactivity at 5–10 °C suggests that their efficiency as cleaner fish will be limited in winter and in higher latitude locations. Overall, ballan wrasse differs substantially from Atlantic salmon in physiology, behaviour and morphology, and may not thrive in some farm environments suitable for salmon. [ABSTRACT FROM AUTHOR]

• Novel methods explored for examining how particle motion and sound pressure affect acoustic responses in zebrafish. • The ratio between particle motion and sound pressure in a small aquarium varied considerably from open water conditions. • Sound pressure and particle motion were predicted at the location of the fish during each exposure. • Particle ellipticity was measured as an indication of the strength of directional information in the soundfield. Underwater sound fields can be complex, both in open water and small tank environments. Here we measured 1) spatial variation in artificially elevated sound levels in a small fish tank for both particle motion and sound pressure. We confirmed that the ratio of pressure and particle motion deviated considerably from what would be expected in theoretical far field environments. We also tested 2) whether the acoustic response tendency of adult zebrafish (Danio rerio) was correlated to the sound field conditions at their position at the moment of sound on-set. We found no correlation between the intensity, quality, or directionality of the behavioural response and the sound pressure or the directivity and ellipticity of particle motion. There was a negative correlation, however, between the tendency to freeze and the particle velocity level. The data and experimental setup provided here may serve a basis to further explore the acoustic world of fish in complex environments and may contribute to the study of potential welfare and conservation issues related to anthropogenic noise. [ABSTRACT FROM AUTHOR]

Declining populations of marine mammals have led to growing concern about their conservation. As a result, a series of specific conservation measures have been put in place (bans on hunting and trading, establishment of protected marine areas). Such rules, although restoring the populations of some species of marine mammals, have nevertheless failed to protect them from the most challenging threat to their survival: the bycatch of non-target species. Accordingly, this Article highlights gaps within fisheries law, clarifying the efficacy of existing norms on the protection of the most endangered marine species of marine mammals, with a particular focus on cetaceans, from over-exploitation. To this aim, the Article explores the peculiar norms developed by treaties of global and regional scope and the European Union (EU) with reference to specific species, including whales, seals, small cetaceans—referred to as direct protection. The Article then proceeds to an analysis of fisheries law that addresses, in an incidental manner, marine mammal protection—referred to as indirect protection. The Article is based on the assumption that measures simply banning hunting or fishing, as envisaged by wildlife law, must necessarily be complemented by fisheries law—that is, Inter-regime linkages. Paradoxically, indirect protection can have a major impact in terms of improvement of both fish welfare and conservation; the problem lies in the fact that current fisheries law fails to provide an adequate response to bycatch. This Article proposes methods to improve fisheries law and also discusses whether the emerging concept of fish welfare can be an asset if included in fisheries rules; the Article ultimately contends that welfare issues must necessarily be part of future legal developments. [ABSTRACT FROM AUTHOR]

Fish have evolved a biological clock to cope with environmental cycles, so they display circadian rhythms in most physiological functions including stress response. Photoperiodic information is transduced by the pineal organ into a rhythmic secretion of melatonin, which is released into the blood circulation with high concentrations at night and low during the day. The melatonin rhythmic profile is under the control of circadian clocks in most fish (except salmonids), and it is considered as an important output of the circadian system, thus modulating most daily behavioral and physiological rhythms. Lighting conditions (intensity and spectrum) change in the underwater environment and affect fish embryo and larvae development: constant light/darkness or red lights can lead to increased malformations and mortality, whereas blue light usually results in best hatching rates and growth performance in marine fish. Many factors display daily rhythms along the hypothalamus-pituitary-interrenal (HPI) axis that controls stress response in fish, including corticotropin-releasing hormone (Crh) and its binding protein (Crhbp), proopiomelanocortin A and B (Pomca and Pomcb), and plasma cortisol, glucose, and lactate. Many of these circadian rhythms are under the control of endogenous molecular clocks, which consist of self-sustained transcriptional-translational feedback loops involving the cyclic expression of circadian clock genes (clock, bmal, per , and cry) which persists under constant light or darkness. Exposing fish to a stressor can result in altered rhythms of most stress indicators, such as cortisol, glucose, and lactate among others, as well as daily rhythms of most behavioral and physiological functions. In addition, crh and pomca expression profiles can be affected by other factors such as light spectrum, which strongly influence the expression profile of growth-related (igf1a, igf2a) genes. Additionally, the daily cycle of water temperature (warmer at day and cooler at night) is another factor that has to be considered. The response to any acute stressor is not only species dependent, but also depends on the time of the day when the stress occurs: nocturnal species show higher responses when stressed during day time, whereas diurnal fish respond stronger at night. Melatonin administration in fish has sedative effects with a reduction in locomotor activity and cortisol levels, as well as reduced liver glycogen and dopaminergic and serotonergic activities within the hypothalamus. In this paper, we are reviewing the role of environmental cycles and biological clocks on the entrainment of daily rhythms in the HPI axis and stress responses in fish. [ABSTRACT FROM AUTHOR]

Recreational fisheries that use rod and reel (i.e., angling) operate around the globe in diverse freshwater and marine habitats, targeting many different gamefish species and engaging at least 220 million participants. The motivations for fishing vary extensively; whether anglers engage in catch‐and‐release or are harvest‐oriented, there is strong potential for recreational fisheries to be conducted in a manner that is both responsible and sustainable. There are many examples of recreational fisheries that are well‐managed where anglers, the angling industry and managers engage in responsible behaviours that both contribute to long‐term sustainability of fish populations and the sector. Yet, recreational fisheries do not operate in a vacuum; fish populations face threats and stressors including harvest from other sectors as well as environmental change, a defining characteristic of the Anthropocene. We argue that the future of recreational fisheries and indeed many wild fish populations and aquatic ecosystems depends on having responsible and sustainable (R&S) recreational fisheries whilst, where possible, addressing, or at least lobbying for increased awareness about the threats to recreational fisheries emanating from outside the sector (e.g., climate change). Here, we first consider how the concepts of R&S intersect in the recreational fishing sector in an increasingly complex socio‐cultural context. Next, we explore the role of the angler, angling industry and decision‐makers in achieving R&S fisheries. We extend this idea further by considering the consequences of a future without recreational fisheries (either because of failures related to R&S) and explore a pertinent case study situated in Uttarakahand, India. Unlike other fisheries sectors where the number of participants is relatively small, recreational angling participants are numerous and widespread, such that if their actions are responsible, they have the potential to be a key voice for conservation and serve as a major force for good in the Anthropocene. What remains to be seen is whether this will be achieved, or if failure will occur to the point that recreational fisheries face increasing pressure to cease, as a result of external environmental threats, the environmental effects of recreational fishing and emerging ethical concerns about the welfare of angled fish. [ABSTRACT FROM AUTHOR]

Over the past few decades, a considerable scientific progress has been achieved in the area of fish welfare at all stages—farming, transportation, various pre-slaughter manipulations, stunning/killing procedures, etc. The increasing scientific interest is mainly due to the serious need of developing and implementing specific fish welfare requirements across the whole chain for both ethical (welfare) and commercial (meat quality) reasons. Since there has been substantial evidence that fish are able to experience pain and suffering, the provoked stress response could be a major cause of altered post-mortem metabolism and impaired meat quality. The present review was aimed to present the relationship between ante-mortem stress, course of post-mortem metabolic processes and the potential alterations in some quality traits of fish for human consumption. [ABSTRACT FROM AUTHOR]

Integration of technological solutions aims to improve accuracy, precision and repeatability in farming operations, and biosensor devices are increasingly used for understanding basic biology during livestock production. The aim of this study was to design and validate a miniaturized tri-axial accelerometer for non-invasive monitoring of farmed fish with re-programmable schedule protocols. The current device (AE-FishBIT v.1s) is a small (14 mm × 7 mm × 7 mm), stand-alone system with a total mass of 600 mg, which allows monitoring animals from 30 to 35 g onwards. The device was attached to the operculum of gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax) juveniles for monitoring their physical activity by measurements of movement accelerations in x - and y -axes, while records of operculum beats (z -axis) served as a measurement of respiratory frequency. Data post-processing of exercised fish in swimming test chambers revealed an exponential increase of fish accelerations with the increase of fish speed from 1 body-length to 4 body-lengths per second, while a close relationship between oxygen consumption (MO2) and opercular frequency was consistently found. Preliminary tests in free-swimming fish kept in rearing tanks also showed that device data recording was able to detect changes in daily fish activity. The usefulness of low computational load for data pre-processing with on-board algorithms was verified from low to submaximal exercise, increasing this procedure the autonomy of the system up to 6 h of data recording with different programmable schedules. Visual observations regarding tissue damage, feeding behavior and circulating levels of stress markers (cortisol, glucose, and lactate) did not reveal at short term a negative impact of device tagging. Reduced plasma levels of triglycerides revealed a transient inhibition of feed intake in small fish (sea bream 50–90 g, sea bass 100–200 g), but this disturbance was not detected in larger fish. All this considered together is the proof of concept that miniaturized devices are suitable for non-invasive and reliable metabolic phenotyping of farmed fish to improve their overall performance and welfare. Further work is underway for improving the attachment procedure and the full device packaging. [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]