Welfare In Aquaculture Research Articles

Insights into Decapod Sentience: Applying the General Welfare Index (GWI) for Whiteleg Shrimp (Penaeus vannamei—Boone, 1931) Reared in Aquaculture Grow-Out Ponds

The rapid growth of shrimp farming, particularly of Penaeus vannamei, accounts for about 80% of the global production of farmed shrimp and involves the cultivation of approximately 383 to 977 billion individuals annually, which highlights the urgent need to address the ethical and technical implications of raising potentially sentient beings. This study builds on the state-of-the-art assessment of sentience, consciousness, stress, distress, nociception, pain perception, and welfare to adapt the General Welfare Index (GWI) for farmed shrimp. The GWI is a quantitative index developed by our research group to measure the degree of welfare in aquaculture, and it has been previously applied to grass carp and tilapia. Using the PRISMA methodology and the creation of a hypothetical shrimp farm, the GWI, with 31 specific and measurable indicators across various welfare domains, is adapted to P. vannamei, offering a comprehensive assessment framework. The inclusion of quantitative welfare indicators promises to improve living conditions in alignment with legislation adopted on decapods’ sentience and contemporary scientific advances.

Fish welfare in farms: potential, knowledge gaps and other insights from the fair-fish database.

An adequate understanding of fish behaviors and their interaction with farm-specific environments is pivotal for enhancing fish welfare in aquaculture. The fair-fish database aims to provide a consistent overview of the welfare of farmed fish. This platform consolidates ethological knowledge into profiles of farmed aquatic species. Its WelfareCheck profiles are organized around welfare indicators, with each criterion receiving classifications (no findings, unclear, low, medium, and high) regarding the likelihood and potential for individuals of a given species to experience good welfare in aquaculture systems, along with the associated certainty level. These criteria include home range, depth range, migration patterns, reproduction, aggregation patterns, aggressive behavior, substrate needs, stress responses, malformations, and slaughtering protocols. We investigated which of these 10 criteria are most relevant to the overall welfare of a species, considering the likelihood, potential, and certainty of good welfare in aquaculture. To achieve this, we reviewed and recorded the high classifications across each criterion and dimension from all published WelfareCheck profiles. To further investigate knowledge gaps across the criteria, we also recorded classifications marked as unclear and no findings. These were then compared across the criteria to assess the frequency of such classifications. While no significant differences were found between the criteria regarding the likelihood that the surveyed species meet their basic welfare needs, criteria related to reproduction, slaughter practices, and substrate needs demonstrated a high potential for better welfare outcomes. Moreover, reproduction and migration patterns exhibited high certainty in the available literature. Based on these findings, we conclude that improving the reproduction of farmed aquatic species, considering their natural needs and behavior, could be an effective and reliable approach to improving welfare. However, we also found a low certainty of information on aggression and an absence or conflicting data on home range, aggregation patterns, stress, and malformations. This highlights an urgent need for research in these areas, which are fundamental for developing more accurate assessments and recommendations for farmed aquatic species.

Metabolic Rate of Goldfish (Carassius auratus) in the Face of Common Aquaculture Challenges.

This study examined the metabolic rate (MO2, oxygen consumption) of goldfish (Carassius auratus) under normal management conditions in aquaculture. Using an intermittent respirometry system, we assessed daily variations and the effects of feeding, handling, temperature increase, and anesthetics. MO2 exhibited a daily rhythm, with higher values during day. Feeding to satiety produced a 35% increase in MO2 compared to fasted animals, with a maximum peak after 3 h and returning to baseline after 7 h. Handling stress (5 min) produced a 140% MO2 peak (from 180 to 252 mg O2 kg-1 h-1), returning to the routine MO2 after 2.5 h. An increase in water temperature (+0.1 °C min-1) up to 30 °C caused MO2 to peak at 200% after 2.5 h from the start of the temperature increase. The use of common anesthetics in aquaculture (MS-222, 2-phenoxyethanol and clove oil in deep anesthesia concentration) affects MO2 during the first few minutes after anesthetic recovery, but also during the following 4 h. It can be concluded that the metabolic rate is a good indicator of the goldfish's response to aquaculture practices involving energy expenditure and stress. Thus, intermittent respirometry is a valuable non-invasive tool for understanding and improving fish welfare in aquaculture.

Fish feeding behavior quantification and automatic acoustic event detection: algorithmic optimization with deep learning

In recent years, the integration of sensor processing technologies with intelligent feeding control systems has become crucial for enhancing recirculating aquaculture systems (RAS). Intelligent feeding control significantly improves profitability and animal welfare in aquaculture by accurately monitoring feed intake and reducing waste. Acoustic methods have proven effective in automating feed monitoring, particularly in assessing feeding intensity. Automatic Audio Event Detection (AED) holds promise for identifying sound events associated with feeding activities, enabling precise monitoring of feeding behavior and estimation of feed consumption through frequency-based feeding signatures. Advancements in sensor technologies and computational capabilities enable real-time collection, processing, and analysis of acoustic data. However, handling high volumes of data with minimal latency and high accuracy poses challenges. To address these challenges, we propose a systematic approach: (1) Data preprocessing using wavelet transforms enhances efficiency and reduces computational overhead. (2) Data pruning focuses on informative features and reduces input data dimensionality, improving classification accuracy. (3) We adopt a weakly-labeled semi-supervised learning model with Convolutional Neural Networks (CNNs) to detect feeding events, improving classification performance. (4) Ensemble learning combines multiple classifiers to mitigate overfitting and enhance model generalization. Our methodology shows promise in accurately quantifying fish feeding behavior using acoustic signals.

Farmed fish welfare research status in Latin America: A review.

Latin America (LATAM) plays an important role in the world's production of aquatic animals and is the second most productive region in the world. Chile, Ecuador, Brazil, Mexico, Colombia, and Perú contribute 87% of LATAM aquaculture production. The fish welfare in aquaculture is of increasing public concern globally, and LATAM is no exception, growing in importance for fish farmers, authorities, and scientists. Although the topic is somewhat controversial, the welfare status of farmed fish has direct implications for their production and the sustainability of the industry. Therefore, this study analyses scientific papers on animal welfare in farmed fish, from the six countries in LATAM with the highest aquaculture production. The main objectives were to quantify the number of papers published between 2000 and 2023 on fish welfare by using scientific databases. A total of 285 papers were found for the period analysed. The country with the largest number of publications was Brazil (75.79%), followed by Chile (13.33%), Mexico (7.02%), Peru (1.75%), Ecuador, and Colombia (1.05%). Nile tilapia was the most studied species, appearing in 30.18% of the publications, with most of the studies mainly dealing with nutrition (32.28%). The growth of aquaculture is leading to joint efforts to generate knowledge on welfare issues, especially in poorly studied species with high production, to create policies that help minimize welfare risks. Given this, the insights generated by this review could be a useful addition to approaches investigating the trends and concepts of fish welfare in LATAM.

Surveying the welfare of farmed fish species on a global scale through the fair-fish database.

Fish welfare is a critical issue that needs to be addressed by the rapidly growing aquaculture industry. Scientific knowledge regarding the natural behaviors of species and the conditions in which they are kept in farms is essential for improving their welfare in aquaculture. To provide a consistent overview of the welfare of farmed fish, the organization fair-fish has created the online platform fair-fish database, which gathers ethological knowledge categorized into profiles of farmed aquatic species. The WelfareChecks on this platform are profiles based on criteria that are rated based on the likelihood and potential of the species to experience a high level of welfare in aquaculture systems, together with the certainty about the findings. A score (WelfareScore) is calculated from these ratings, serving as a reference to identify knowledge gaps, assess welfare, and suggest ways to improve it. Here, we performed an in-depth analysis of the species with WelfareChecks already published in the fair-fish database based on their respective WelfareScores. In general, although just a small percentage of farmed aquatic species (~5%) have at least a 20% chance of experiencing a good level of welfare under minimal aquaculture conditions, 60% of them have at least some potential to achieve good welfare under high-standard conditions, with more than a third of the species (~37%) having at least a 20% potential. Despite that, several species exhibit a very high frequency of low chances and potential for experiencing good welfare levels under aquaculture conditions, besides a low degree of certainty based on literature reviews. Furthermore, many others show a very frequent occurrence of unclear or nonexistent knowledge in their profiles. The current welfare state is therefore poor for the majority of farmed aquatic species; yet, there is considerable potential for improvement. However, many species are very unlikely to achieve good welfare, even under high-standard conditions. Importantly, large knowledge gaps remain for an accurate assessment of the welfare of several farmed species.

Fish Welfare-Related Issues and Their Relevance in Land-Based Olive Flounder (Paralichthys olivaceus) Farms in Korea.

Korean aquaculture has expanded considerably in recent decades; however, this growth has often prioritized quantity over fish welfare. Therefore, we analyzed the aquaculture practices of olive flounder, the predominant species in Korean consumption and production, within the framework of fish welfare. We conducted extensive interviews and surveys across olive flounder farms in Jeju-do and Wando to examine prevalent issues impacting fish welfare in aquaculture. These issues include stressors, mass mortality events, and disease outbreaks, all of which strain the welfare of farmed fish. Moreover, our survey revealed farmers' varying perceptions of fish welfare, highlighting the necessity for a cohesive approach. Accordingly, we propose recommendations to enhance fish welfare and establish a more sustainable aquaculture model in Korea. Ensuring fish welfare in aquaculture operations requires a comprehensive approach that considers the physiological and behavioral needs of fish throughout the farming lifecycle. By prioritizing fish welfare, Korean aquaculture can strengthen its growth while maintaining ethical standards and ensuring the well-being of farmed fish. This welfare-centric approach is crucial for the long-term sustainability and resilience of the Korean aquaculture industry. By addressing welfare concerns and promoting responsible practices, Korean aquaculture can foster an ethically sound and sustainable future.

The use of Tetraselmis chuii as seafood flavoring agent in a vegetable broth

The growing demand of seafood alternatives is driven by concerns on overfishing, marine pollutants and animal welfare in aquaculture and fisheries. Currently, the availability of non-animal-based seafood flavorings on the market is limited, and animal-based seafood flavorings conflict with vegetarian and vegan criteria.The aim of this study is to explore the use of Tetraselmis chuii as a seafood flavoring in a vegetable broth. The flavor of the T. chuii broth was compared with a broth containing vegan fish flavoring based on a yeast extract and two broths containing white fish and lobster flavorings. To evaluate the different broths, the study employs a combination of sensory evaluation by a trained panel, chemical flavor analysis for aroma and umami characteristics, and consumer acceptability tests.Our results indicate that T. chuii effectively imparts a fish and shellfish flavor to the broth, which is less intense compared to the white fish and lobster flavorings. Nevertheless, consumers are equally positive of the aroma and flavor of the T. chuii broth and the animal-based seafood flavorings broths. The chemical flavor analysis of the T. chuii broth identifies volatile organic compounds (VOCs) such as dimethyl sulfide, methanethiol, trimethylamine, and 4-heptenal (Z), which collectively contribute to its distinct seafood aroma.Consumer preference tests show a preference for the seafood aroma of the T. chuii broth over the vegan fish flavoring broth, attributed to the meaty-like off-odor originating from specific VOCs of the yeast extract. In contrast, the vegan fish flavoring broth exhibits a stronger umami taste which is explained by elevated levels of free glutamate and guanosine-5′-monophosphate.This study highlights the potential of T. chuii as innovative seafood flavoring agent to enhance the sensory experience of seafood alternatives, contributing to the ongoing development of sustainable and flavorful non-animal alternatives in the food industry.

Identifying the physiological and behavioral responsiveness to characterize the stress coping style in the large yellow croaker (Larimichthys crocea)

Consistent variation in behavior and physiology has been well recognized when fish responds to challenges, as defined as proactive and reactive coping styles which enlightens a compromise between production and welfare in aquaculture. In the present study, behavioral and physiological responses after a 3 min net restraint were evaluated to predict stress-coping styles in the lager yellow croaker (Larimichthys crocea). The behavioral responses to open field, avoidance, and swimming capability were assessed, and resting plasma cortisol, CRH, IFN-α, and IgM levels were measured in the proactive and reactive individuals. Results indicate that the recovery latency is a candidate to characterize the coping style, as L. crocea recovering more quickly from 3 min net restraint also having significant lower plasma cortisol, suggesting a proactive coping style. And recovery latency showed consistency at an interval of 10 days. Furthermore, proactive L. crocea were more active in exploration, risk averse, and superior in swimming capability than the reactive fishes. The physiological responses, including plasma cortisol, CRH, and IFN-α, were observed without significant difference, while IgM in the proactive significantly exceeded the reactive individuals at 7 days after the restraint stress. Overall, the net restraint is a predictive tool to assess the varying stress responsiveness in L. crocea, which is the first step into exploiting the importance of ethology to improve the production and welfare in L. crocea aquaculture.

Fasting and its implications for fish welfare in Atlantic salmon aquaculture

AbstractPeriods of fasting occur for a multitude of reasons in Atlantic salmon aquaculture. Feed withdrawal is widely used prior to transport, parasite treatments, preslaughter and for depuration purposes in recirculating aquaculture systems. Voluntary fasting is a coping response when fish have poor health or are exposed to poor farm environments. Owing to increased attention to animal welfare in aquaculture, concerns have been raised regarding ethical issues when farmed fish are subjected to fasting. However, thorough science‐based recommendations for fasting and feed‐withdrawal regimes have been lacking. The purpose of this review is to provide a synthesis of the various causes for fasting in Atlantic salmon aquaculture and evaluate their associated welfare implications so that guidelines for appropriate practices can be formulated. To interpret impacts, we describe biological responses and tolerance limits to fasting in Atlantic salmon and consider adaptations in the wild. Fry and parr are highly sensitive to feed withdrawal. However, post‐smolts and adults are well‐adapted to endure prolonged fasting without experiencing compromised functionality or health. Here, short periods of feed withdrawal prior to operations should therefore not constitute significant welfare concerns. Serious concerns are instead associated with voluntary fasting that may continue for weeks. We emphasize that environmental extremes that exceed appetite impairing thresholds must be avoided. Additionally, farmed fish should not be subjected to practices that lead to chronic stress that induce cessation of appetite. Diseases or parasites that impair appetite should also be mitigated. Fasting is here a symptom rather than a cause for poor welfare.

Circadian rhythm in turbot (Scophthalmus maximus): daily variation of blood metabolites in recirculating aquaculture systems

IntroductionAnimal welfare in aquaculture is becoming increasingly important, and detailed knowledge of the species concerned is essential for further optimization on farms. Every organism is controlled by an internal clock, the circadian rhythm, which is crucial for metabolic processes and is partially influenced by abiotic factors, making it important for aquaculture practices.ObjectiveIn order to determine the circadian rhythm of adult turbot (Scophthalmus maximus), blood samples were collected over a 24-h period and plasma metabolite profiles were analyzed by 1H-NMR spectroscopy.MethodsThe fish were habituated to feeding times at 9 am and 3 pm and with the NMR spectroscopy 46 metabolites could be identified, eight of which appeared to shift throughout the day.ResultsWe noted exceptionally high values around 3 pm for the amino acids isoleucine, leucine, valine, phenylalanine, lysine, and the stress indicator lactate. These metabolic peaks were interpreted as either habituation to the usual feeding time or as natural peak levels in turbot in a 24-h circle because other indicators for stress (glucose, cortisol and lysozymes) showed a stable baseline, indicating that the animals had no or very little stress during the experimental period.ConclusionThis study provides initial insights into the diurnal variation of metabolites in adult turbot; however, further studies are needed to confirm present findings of possible fluctuations in amino acids and sugars. Implementing optimized feeding times (with high levels of sugars and low levels of stress metabolites) could lead to less stress, fewer disease outbreaks and overall improved fish welfare in aquaculture facilities.

Fish Welfare in Aquaculture: Physiological and Immunological Activities for Diets, Social and Spatial Stress on Mediterranean Aqua Cultured Species

Welfare assessment currently is less well-characterized for aquatic animals and the classical methodologies used for terrestrial animals are not adequate to improve our knowledge about fish well-being. Among different approaches, the status of organism responses can be carried out using different physiological and biochemical tools. Here, we present the state of the art regarding fish welfare, methodologies, and experimental results with a particular focus on two important Mediterranean aquaculture species, Sparus aurata and Dicentrarchus labrax. We introduce an approach using physiological stress-indicators, growth performance and swimming activity to investigate the effects of the implantation of electronic tags to facilitate the application of telemetry for aquaculture purposes. The application of telemetry to research on aquatic organisms has expanded recently, and its utilization needs to be better understood. The mentioned approaches have been discussed for application in different aquaculture methodologies. Moreover, social stress and territoriality are relevant factors in the evaluation of gregarious species that may have consequences on the conditions of animals farmed in captivity. These aspects, that may impair the ability of fish to respond to various stimuli or negatively influence the flesh quality, here are analysed through behavioural observation, flanked by the physiological and immunological approach.

‘Positive’ animal welfare in aquaculture as a cardinal principle for sustainable development

‘Positive’ animal welfare in aquaculture as a cardinal principle for sustainable development

Daily rhythms in the behavioural stress response of the zebrafish Danio rerio

In nature, animals are exposed to stressors that occur with different likelihood throughout the day, such as risk of predation and human disturbance. Hence, the stress response is expected to vary plastically to adaptively match these challenges. Several studies have supported this hypothesis in a wide range of vertebrate species, including some teleost fish, mostly through evidence of circadian variation in physiology. However, in teleost fish, circadian variation in behavioural stress responses is less understood. Here, we investigated the daily rhythm of stress response at the behavioural level in the zebrafish Danio rerio. We exposed individuals and shoals to an open field test every 4 h over a 24 h cycle, recording three behavioural indicators of stress and anxiety levels in novel environments (thigmotaxis, activity and freezing). Thigmotaxis and activity significantly varied throughout the day with a similar pattern, in line with a stronger stress response in the night phase. The same was suggested by analysis of freezing in shoals, but not in individual fish, in which variation appeared mostly driven by a single peak in the light phase. In a control experiment, we observed a set of subjects after familiarisation with the open-field apparatus. This experiment indicated that activity and freezing might present a daily rhythmicity that is unrelated to environmental novelty, and thus to stress responses. However, the thigmotaxis was constant through the day in the control condition, suggesting that the daily variation of this indicator is mostly attributable to the stress response. Overall, this research indicates that behavioural stress response of zebrafish does follow a daily rhythm, although this may be masked using behavioural indicators other than thigmotaxis. This rhythmicity can be relevant to improve welfare in aquaculture and reliability of behavioural research in fish models.

From the basics to emerging diagnostic technologies: What is on the horizon for tilapia disease diagnostics?

AbstractTilapia is an affordable protein source farmed in over 140 countries with the majority of production in low‐ and middle‐income countries. Intensification of tilapia farming has exacerbated losses caused by emerging and re‐emerging infectious diseases. Disease diagnostics play a crucial role in biosecurity and health management to mitigate disease loss and improve animal welfare in aquaculture. Three continuous levels of diagnostics (I, II and III) for aquatic species have been proposed by Food and Agriculture Organization of the United Nations (FAO) and the Network of Aquaculture Centers in Asia and the Pacific (NACA) to promote the integration of basic and advanced methods to achieve accurate and meaningful interpretation of diagnostic results. However, the recent proliferation of cutting‐edge molecular methods applied in the diagnosis of diseases of aquacultured animals has shifted the focus of researchers and users away from basic approaches and toward molecular diagnostics, despite the fact that many diseases can be rapidly diagnosed using inexpensive, simple microscopic examination and that most emerging diseases in aquaculture were discovered by histopathology. This review, therefore, revisits and highlights the importance of the three levels of diagnostics for diseases of tilapia, particularly the frequently overlooked basic procedures (e.g., case history records, gross pathology, presumptive diagnostic methods and histopathology). The review also covers current and emerging molecular diagnostic technologies for tilapia pathogens including polymerase chain reaction methods (conventional, quantitative, digital), isothermal amplification methods Loop‐mediated Isothermal Amplification (LAMP), recombinase polymerase amplification (RPA), clustered regularly interspaced short palindromic repeats (CRISPR)‐based detection, lateral flow immunoassays, as well as discussing what is on the horizon for tilapia disease diagnostics (next generation sequencing, artificial intelligence, environmental Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA) and point‐of‐care testing) providing a future vision for transferring these technologies to farmers and stakeholders for a sustainable aquatic food system transformation.

Environmental Enrichment for Rainbow Trout Fingerlings: A Case Study Using Shelters in an Organic Trout Farm.

Physical enrichment can improve the welfare of captive fish. Previous research has shown that fish often show preference for enriched environments, which can also result in improvements in growth performance. However, effects of enrichment are not always positive and the design and extent of the enrichment needs to be carefully considered. In this regard, information in real aquaculture scenarios is limited. The aim of this study was to serve as a proof of concept to test the feasibility of using simple PVC immersed shelters as a tool for better welfare in an organic rainbow trout farm. Our shelters induced little extra work in farm routines and had no negative effects on fish performance, health or mortality. The behavioral assessment pointed to a preference for sheltered areas in undisturbed conditions. However, no benefits were observed in terms of stress responses during standardized stress tests, and fish showed no obvious shelter-seeking behavior after disturbance. The results in terms of shelter-seeking behavior were probably limited by the short duration of the experiment, which was due to the farm's routines and needs. It is recommended that strategies for enrichment in real scenarios should be tested covering a relevant part of the life cycle of the fish in captivity, to fully account for their potential to improve welfare in aquaculture.

Modified kinetic energy feature-based graph convolutional network for fish appetite grading using time-limited data in aquaculture

Feed has the greatest impact on the carbon footprint of the aquaculture, and also determines the water quality in aquaculture to a great extent. Making appropriate feeding control strategies is one of the most effective ways to promote cleaner production as well as fish welfare in aquaculture. Reliable and accurate fish appetite grading especially based on time-limited data is a prerequisite for achieving high-precision and reasonable feeding control in practical production. To date, however, few efforts have been done on this challenge. For these, regarding Micropterus salmoides as the experimental fish, a novel and practical method, based on a modified kinetic energy feature-based graph convolutional network (GCN), was developed in this study. First, graphs were constructed based on the extracted modified kinetic energy features and their temporal correlation. Then, with the help of a series of the convolution and global pooling operations, a GCN model was customized based on the constructed graphs. Following this, the customized GCN model was enriched by the self-attention pooling mechanism and customized network structure. Results show that the proposed GCN-based approach outperforms other typical state-of-the-art methods in fish appetite grading, and the grading accuracy obtained here could be 98.60% using only the first 4.2 seconds as well as the first 8.3 seconds of input data, which is not much different from that (98.89%) using full-length (25 second-long) input data. What’s more, compared to the recurrent neural network (RNN)-based method which performance is closest to our method, the space complexity of the proposed approach here can better satisfy the requirements of real aquaculture, in which the quantity of the trainable parameters here is only 6.4% ~ 31.8% of the RNN-based method. In summary, the proposed modified kinetic energy feature-based GCN approach is favorable for the appetite grading of fish like Micropterus salmoides with time-limited data, which is a promising approach in dealing with feeding control tasks and alleviating the water environmental burden in aquaculture.

Shelter Color Selection of Juvenile Swimming Crabs (Portunus trituberculatus)

Color preference testing for animals is a prerequisite for optimizing facilities and ensuring animal welfare in aquaculture. Swimming crabs (Portunus trituberculatus) are aggressive, and shelters are often installed in ponds to reduce the high mortality rate caused by their agonistic behavior. To test the preference of juvenile crabs for the color of shelters, this study observes the preferences of crabs for shelters of different colors (white, yellow, blue, and black). The counts and duration of crabs occupying different colored shelters were quantified. The probability of fighting and the probability of abandoning the shelter were also calculated. The results revealed that: (i) when all colors were presented simultaneously, the z-scores of the blue shelters were far higher than others during the day; (ii) when only one color was present, crabs occupied the blue shelter significantly more often and for longer periods of time than others during the day, with invasive crabs exacerbating this preference; and (iii) the probability of fighting between crabs was relatively low in the presence of the blue shelter, and the probability of abandoning the shelter was significantly lower than that of others. Based on these results, blue shelters are recommended for use in swimming crab ponds.

Mucin O-glycosylation and pathogen binding ability differ between rainbow trout epithelial sites

Mucins are highly glycosylated proteins that make up the mucus covering internal and external surfaces of fish. Mucin O-glycans regulate pathogen quorum sensing, growth, virulence and attachment to the host. Knowledge on this mucosal defense system can enable alternative treatments to diseases posing a threat to productivity and welfare in aquaculture. Here, we characterize the rainbow trout (Oncorhynchus mykiss) gill, skin, pyloric ceca and distal intestinal mucin O-glycosylation and compare it to known teleost O-glycomes. We identified 54 O-glycans, consisting of up to nine monosaccharide residues. Skin glycans were most acidic, shortest on average and consisted mainly of NeuAcα2-6GalNAc. Glycans from the gills were less acidic with predominantly core 1 and 2 glycans, whereas glycans from pyloric ceca and distal intestine expressed an increased number of core 5 glycans, distinctly decorated with NeuAcα2-8NeuAc- like epitopes. When compared to Atlantic salmon and Arctic charr, trends on the core distribution, average size and overall acidity remained similar, although the epitopes varied. Rainbow trout mucins from gill and intestine bound A. salmonicida and A. hydrophila more efficiently than skin mucins. This is in line with a model where skin mucins with small glycans limit bacterial adhesion to the fish surface whereas the complex intestinal mucin glycans aid in trapping and removing pathogens from the epithelial surface.

Importance of substrate on welfare in swimming crab (Portunus trituberculatus) culture: A territorial behavior perspective

Concern for animal welfare in aquaculture is increasing. Environmental enrichment (EE) is an effective means to improve the welfare of animals, which is linked to their behavior. Territorial behavior includes interactions between animals and their environment and conspecifics, and can directly reflect the welfare status of cultured animals. To explore the influence of different substate, an important influence factor of EE, on welfare of swimming crab (Portunus trituberculatus), a behavior acquisition system was established. Moving trajectory, territory size, time budgeting, total number of territorial behaviors, and bouts of crabs in EE groups (sand substrate, sand and shell mixed substrate, and shell substate) and the control (hard bottom) group were calculated and analyzed. Furthermore, the territorial behavior score of crabs was calculated using PCA to estimate territoriality. According to the results, the presence of substrate EE effectively reduced the territoriality of the swimming crabs, and sand as substrate affected most significantly. In the control group, stereotypical behaviors of crabs (repeated movements for long periods) indicated a low welfare level. In the EE group, interactions with the substrate, including burying behavior, digging, etc., revealed a higher behavioral diversity, which demonstrated that a suitable EE could effectively improve the welfare of swimming crabs. In general, from the perspective of territorial behavior, the presence of substrate, especially sand, was an effective means of improving the welfare of cultured swimming crabs.