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Content archived on 2024-06-25

On farm assessment of stress level in fish

Final Report Summary - FASTFISH (On farm assessment of stress level in fish)

The European Union aimed to develop a modern, sustainable and competitive aquaculture sector. Aquaculture systems ought to be designed as an integrated part of healthy ecosystems in order to achieve this objective, thus securing acceptable standards of animal welfare and reducing the risk of events which impose high stress levels on fish. The development of a protocol for monitoring pre-critical stress levels in populations of farmed fish, which is a key parameter for achieving sustainable fish production, was the FASTFISH project overall objective.

FASTFISH used Atlantic salmon and European sea bass as model organisms and had the following targets:
1. to identify behavioural indicators for monitoring and quantification of farmed fish stress levels;
2. to validate and quantify the indicators using immunological and physiological methods;
3. to develop databases and protocols for on-farm monitoring of environmental data and stress indicators;
4. to propose a system for stress level assessment and management based on monitored parameters;
5. to identify the prerequisites and market mechanisms for the developed tool implementation and estimate the cost and benefits of such an implementation by the fish farmers;
6. to implement, test and refine the database, protocol and expert system in commercial aquaculture periods with potentially high and low stress levels.

The fish behavioural activities and their ontogeny were studied in order to select the most suitable conditions for fish cultivation. Two different rearing technologies were used for that purpose, namely the intensive and mesocosm rearing system. Sea bass populations during different growing stages, from larvae to the commercial size, served as experiment samples. The most marked differences between the populations concerned swimming performance and speed and some divergence in feeding behaviour was also apparent. Intensive rearing fish appeared to present a behavioural delay compared to the mesocosm reared ones, whose behaviour approached that of the wild populations. It was proven that both feeding and swimming were differentially modulated by the level of domestication and selection, with feeding being a primary modulated variable and swimming forming a secondary indicator of feeding motivation alteration. Fish issued from all strains presented the same adaptation abilities and thus the same welfare potential under the constrained environment.

Additional studies were carried out for Atlantic salmon farmed populations of different growing stages, whose results were validated and quantified using physiological or immunological methods. Three experiment series, two in tanks and one in sea cages, were carried out. The sub-goals of the experiments were to identify indicators of acute stress and measure the latency of the stress behaviour and reduced appetite after the application of the acute stressor. Consistency was found between the levels of physiological responses to different stressors, taking into account differences in cortisol production and oxygen consumption between the growing phases under consideration. Cortisol released to water was found useful as a non invasive method for verification of physiological stress, but was a relatively expensive and cumbersome method. Hyper consumption of oxygen could, along with cortisol or even unaccompanied by other physiological measurements, be used as a precise assessment of acute stress. The assumption of reduced immune response in chronically stressed fish was not verified by the experiment; hence reduction in immune response could not serve to validate chronic stress levels in Atlantic salmon.

In order to allow the different professionals of the sector to monitor fish behaviour, a web application and database system, named Fasttool, was developed for registration of environmental data, stress indicators and husbandry data on a daily basis. Fasttool was based on the latest internet technology to provide a seamless interaction with the database. The latter was designed as flexible as possible so as to respond to the needs of either complex users, such as researchers, or fish farmers dealing with a limited amount of data.

Fasttool performance monitoring showed that it was difficult to get everyday compliance from the farmers; as a result the user friendliness and attractiveness of the application needed to be increased, while less dependence on manual data entering was necessary. A prototype of a measurement system that provided a profile of the environmental conditions at a sea cage and automatically transmitted data to the database was thus created. The new application was called Welfaremeter. Based on a software analysis of the transmitted data Welfaremeter evaluated the environmental conditions in each case and calculated a relevant welfare index.

A segmentation, based on desk research and according to the various stakeholders' needs and aims, was carried out to determine the costs and benefits of the fish welfare monitoring systems implementation in the aquaculture industry. A survey on the intentional use of Fasttool was performed using questionnaires, and, in addition, an initial implementation plan for the technology was designed. Finally, strategic issues faced by each specific organisation were commented based on the research and survey results.

It appeared that adoption of Fasttool would be feasible in case fish farmers were legally obliged or socially forced to apply monitoring systems in the farms, so as to achieve sustainable aquaculture development. Building capacity and experience by all stakeholders about the approach followed in monitoring welfare needed to be a priority during the first development stage. The platform roles could then be extended to deal with the adoption of new insights, monitor the progress and achievements about learning and verification, or find ways of how farms with low welfare could be given temporary access and opportunities to market their fish.

The developed technology was implemented, tested and evaluated in pilot and commercial scale sea farms, examining the fish species used for its development, i.e. sea bass and Atlantic salmon. The system application helped to derive useful conclusions regarding both fish behaviour and potential technology improvement which could increase its validity and applicability.

FASTFISH was a combination of basic and applied research and included the study of societal issues related to the implementation of the monitoring and documentation tool. The project main conclusions were the following:
1. behavioural indicators could be used to assess stress levels in different stages of fish evolution. However, training and employment of adequate technology were necessary in order for the farmers to be able to personally assess these indicators.
2. behavioural stress level indicators seemed more sensitive to stress than the latency of physiological effects. Oxygen consumption could be an easy to measure indicator for both deviations in food consumption and active metabolism as a result of stress levels.
3. acute stress resulted in reduced food intake, for which fish never compensated. As a result, all unnecessary handling should be avoided.
4. the links between chronic stress and immune response were not evident and further research was required to define chronic stress tolerance limits.
5. the project contributed a lot to the creation of a web-based database; however, further refinement was needed to develop a functional system which could be implemented at an industrial scale.

The monitoring of rearing condition, fish behaviour, stress and welfare conditions in fish farms was at a low level before FASTFISH initiation while no consensus for assessment of stress level or fish welfare existed. Fish welfare was a complex issue to be addressed, since it depended on the animals' physiological and psychological state and on the way they assessed their individual needs. Theories, models and methods to score and assess welfare had to be further developed, after the project completion, in order to fully understand this condition. In addition, dissemination and education plans were necessary. However, it was estimated that the knowledge acquired through FASTFISH could help in establishing a general framework towards stress and welfare monitoring in the rapidly changing aquaculture industry.