Chris Noble

Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e.g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e.g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.

Injuries and deformities in fish: their potential impacts upon aquacultural production and welfare

Fish can be the recipients of numerous injuries that are potentially deleterious to aquacultural production performance and welfare. This review will employ a systematic approach that classifies injuries in relation to specific anatomical areas of the fish and will evaluate the effects of injury upon production and welfare. The selected areas include the (1) mouth, (2) eye, (3) epidermis and (4) fins. These areas cover a large number of external anatomical features that can be injured during aquacultural procedures and husbandry practices. In particular, these injuries can be diagnosed on live fish, in a farm environment. For each anatomical feature, this review addresses (a) its structure and function and (b) defines key injuries that can affect the fish from a production and a welfare perspective. Particular attention is then given to (c) defining known and potential aquacultural risk factors before (d) identifying and outlining potential short- and long-term farming practices and mitigation strategies to reduce the incidence and prevalence of these injuries. The review then concludes with an analysis of potential synergies between risk factors the type of injury, in addition to identifying potential synergies in mitigation strategies. The paper covers both aquaculture and capture-based aquaculture.

Demand feeding and welfare in farmed fish

Following the development of demand-feeding systems, many experiments have been conducted to explore feeding motivation and feed intake in farmed fish. This work aims to review a selection of studies in the field, focusing on three key factors, related to demand feeding and fish welfare. Firstly, we outline how demand feeders should be considered when developing feed management strategies for improving welfare in production conditions. Secondly, via laboratory demand-feeding experiments, we show self-feeding activities depend not only on feeding motivation and social organisation, but also on individual learning capacity and risk-taking behaviour. Thirdly, we report encouraging results demonstrating that when presented with two or more self-feeders containing complementary foods, fish select a diet according to their specific nutritional requirements, suggesting that demand feeders could be used to improve welfare by allowing fish to meet their nutritional needs.

HOW TO MEASURE THE ECONOMIC IMPACTS OF CHANGES IN GROWTH, FEED EFFICIENCY AND SURVIVAL IN AQUACULTURE

In this article we introduce a variety of bio-economic models that can be used to calculate the economic benefits associated with improved productivity in aquaculture. In the aquaculture industry, three important biological productivity factors are growth, survival and feed efficiency. The profitability of improving productivity factors, especially growth, is highly dependent upon the cost factor structure, production system, its constraints and other factors within the supply chain. Therefore we present a number of different bio-economical models that can be used to robustly assess the economic impacts in different production environments. These models are introduced with case examples across a range of aquaculture species and production systems. We calculate changes in profitability through a reduction in production costs and any potential increases in product price premiums via the use of weight dependent unit profit as the outcome in cost-benefit analysis, so that results may be expanded to cover different volumes.

THE BIO-ECONOMIC IMPACT OF IMPROVING FISH WELFARE USING DEMAND FEEDERS IN SCOTTISH ATLANTIC SALMON SMOLT PRODUCTION

Fin damage can be common in farmed juvenile Atlantic salmon and is both directly harmful to the welfare of the fish and a potential sign of poor rearing conditions. Fin damage can be reduced during freshwater production by the use of feeding systems that deliver food in accordance with the fishs current appetite, rather than at fixed times. The bio-economic implications of feeding fish to appetite using demand feeding technology were modelled with the BENEFISH decision analysis tool. Using figures for Scottish smolt production, results from the model show that implementing demand feeders generates welfare benefits, but at a clear economic cost.

BIO-ECONOMIC COSTS AND BENEFITS OF USING TRIPLOID RAINBOW TROUT IN AQUACULTURE: REDUCED MORTALITY

Analysis of data collected from rainbow trout farms in the United Kingdom found that mortality levels in triploid rainbow trout were lower than those in diploids. The consequences of rearing triploids, as opposed to diploids, as an intervention to reduce mortality in the U.K. trout farming industry were quantified using a bio-economic model. The model showed that growing triploids could be more profitable than growing diploids, and this was achieved through improvements in productivity (in terms of better survival) and potential for increased product value, and despite the extra costs attributed to purchasing triploid fingerlings.

THE BIO-ECONOMIC COSTS AND BENEFITS OF IMPROVING PRODUCTIVITY AND FISH WELFARE IN AQUACULTURE: UTILIZING CO2 STRIPPING TECHNOLOGY IN NORWEGIAN ATLANTIC SALMON SMOLT PRODUCTION

High dissolved CO2 levels in tank water are potentially detrimental to the production and welfare of Atlantic salmon smolts in Norwegian hatcheries. A potential welfare action for reducing CO2 levels is to deploy CO2 stripping technology. The economic consequences of using this approach were modelled using a bio-economic decision analysis tool. Results from the model showed that farmers can improve fish welfare and their profits by utilizing CO2 stripping technology, as costs of implementing the welfare action were less than the potential bio-economic benefits that can be achieved through improved productivity and any potential added value for improving the welfare of smolts.

MODELING THE ECONOMIC IMPACT OF WELFARE INTERVENTIONS IN FISH FARMING—A CASE STUDY FROM THE U.K. RAINBOW TROUT INDUSTRY

Actions that aim to improve animal welfare are likely to involve costs for the producer, although at the same time such actions may improve the profitability of production. In this article we introduce a quantitative bio-economical approach for estimating the economic consequences for improving animal welfare in the aquaculture industry; for farmers and the industry as a whole. The decision tool can be used with different welfare indicators, different species and production systems. It can be used to rank the economic consequences of different techniques that aim to improve welfare. We illustrate the decision tool with a case study relating to the use of triploids in rainbow trout farming. We highlight the probability how the benefits gained from changes in bio-economical productivity factors, and consumers’ willingness to pay can overcome the costs associated with implementing a specific welfare intervention.

A MULTI-DISCIPLINARY FRAMEWORK FOR BIO-ECONOMIC MODELING IN AQUACULTURE: A WELFARE CASE STUDY

This article summarizes the framework that translated data from multiple disciplines into a bio-economic decision tool for modeling the costs and benefits of improving fish welfare in commercial aquaculture. This decision tool formed the basis of a recent EU research project, BENEFISH which was funded via the European Commissions Sixth Framework (FP6) initiative. The bio-economic decision model can incorporate biological data, productivity data, micro (farm) and macro (industry) level economic data, and consumer marketing and business to business data. It can identify areas for potential added value that might be achieved by improving fish welfare across a range of species and husbandry systems within European aquaculture. This article provides a brief overview of the minimum data requirements for successfully modeling the bio-economic impacts of improvements in farmed fish welfare using the model developed during the BENEFISH project. It also highlights potential bottlenecks and the minimum prerequisites for each potential data set to be used for successful modeling.