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Animal Welfare Aspects of Husbandry Systems for Farmed Atlantic Salmon

by the Fish Site Editor
01 August 2008, at 1:00am

This report is an extract taken from a Scientific Opinion of the Panel on Animal Health and Welfare on a request from the EuropeanCommission on Animal welfare aspects of husbandry systems for farmed Atlantic salmon. The EFSA Journal (2008)736, 1-31.

Summary

Council Directive 98/58/EC concerning the protection of animals kept for farming purposes lays down minimum standards for the protection of animals bred or kept for farming purposes, including fish. Following a request from the European Commission, the AHAW Panel was asked to deliver a Scientific Opinion on the animal welfare aspects of husbandry systems for farmed Atlantic salmon.. The Scientific Opinion was adopted on 19th June 2008. From the data presented in the scientific report factors affecting farmed Atlantic salmon welfare were identified which led to conclusions in the Scientific Opinion. These factors are grouped as: environmental conditions (abiotic and biotic factors), feed and feeding, husbandry, genetics and the impact of disease and disease control measures. A risk assessment was carried out to obtain a ranking of risk and compare the production systems. The discussion of the risk assessment is presented in the opinion.

Atlantic salmon behaviour such as feeding, swimming and social behaviour are relevant when considering the welfare impact of farming systems. Genetic selection of salmon should take into account possible consequences for their welfare of any changes.

The main factors affecting Atlantic salmon welfare were considered to be those discussed below.

Water quality is essential for good welfare in fish and several damaging effects of poor water quality on fish health were recognised. Water quality effects relate not only to the absolute levels but also to the rate of its change and interactions with other factors. Tolerance levels were indicated when available. For instance it was recommended that oxygen saturation should be maintained above 70% to maintain full appetite and growth but subsequent research on the impact on fish welfare may show that higher levels are required. Carbon dioxide concentration (CO2) can be an important factor especially in systems where oxygen supplementation is used. Optimal photoperiod and light intensity are also key factors and different positive and negative effects according to the life stage were identified.

Stocking density was considered a major factor affecting salmon welfare. Its effects interact with those of many other factors and make it difficult to establish a maximum and minimum values or optimum stocking densities that would safeguard welfare. The monitoring of the conditions of the fish, such as fin damage, other injuries, growth rate, and behaviours expressed and overall health, was recommended to set appropriate levels of stocking density.

Atlantic salmon diet contains a high proportion of marine fish meal and oil, to meet size and life cycle specific requirements for macro- and micronutrients but the increased demand for marine feed components has placed a focus on alternative resources. Introduction of novel non-marine feed components can lead to specific problems although there is evidence for their potential to partly replace high quality fish meal in diets.

Grading (sorting by body size) is an important part of husbandry. Grading systems should be set up to minimise the time fish are out of the tanks or cages, to ensure sufficient water quality is maintained and to minimise stress. Monitoring of the environment, fish size, fish health status and fish behaviour was recommended.

Saprolegnia infection, winter ulcer disease, IPN and sea lice are examples of diseases that cause poor welfare, and require control. Availability of veterinary medical products approved for Atlantic salmon is limited and this constitutes an important risk. Vaccines have made a significant contribution to controlling serious infectious diseases and to the significant reduction of the use antibiotics/chemotherapeutics. However several risks were identified. Future research on non invasive effective vaccination methods and new types of adjuvant is necessary.

A risk assessment approach was used to compile a risk ranking for these groups of factors, estimate which hazards are more important for each life stage and enable a comparison of the different production systems. Due to the limited amount of quantitative data related to production systems and effects of potential hazards on Atlantic salmon welfare, the risk assessment was mainly based on expert opinion.

In the risk assessment no major differences were found concerning overall welfare risk among the different production systems used for each life stage. Production systems can differ in their risk score for different categories of hazards, since they can have specific risks. Measures to improve welfare should be adapted to different production systems taking into consideration the specific requirements of each life stage.

A minority opinion was received based on the view that the accepted Report and adopted Opinion are incomplete and that in order to answer the mandate from the European Commission, the general chapters on the welfare, biological functioning and farming of fish should be included.

Further Reading

- You can view the full report by clicking here.

June 2008

the Fish Site Editor