Animal welfare aspects of husbandry systems for farmed fish - European eel - Scientific Opinion of the Panel on Animal Health and Welfare

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Following a request from European Commission, the Panel on Animal Health and Welfare was asked to deliver a scientific opinion on animal welfare aspects of husbandry systems for farmed fish. Council Directive 98/58/EC concerning the protection of animals kept for farming purposes lays down minimum standards for the protection of animals, including fish. The Scientific Opinion on welfare of European eel was adopted on the 12th of September 2008.

Eel is a significant cultured species in Europe. The juvenile stock is obtained by capture from the wild as there is no closed cycle of production. Although it is a cultured species albeit captured from the wild, the European eel (Anguilla anguilla) is also listed as an endangered species and is subject to EU Council Regulation EC No 1100/2007 establishing measures for the recovery of the stock in view of protection and sustainable exploitation of this species. Another specific feature of eel production is that it is the only fish species that is caught in large quantities at the larval stage (glass eels) before they can make any contribution to the reproduction of the species. In addition, the existence of a human consumption market for (dead) glass eels does not favour good welfare practices as dead and animals in poor condition can still have a high market value.

It is recommended that research be supported that is directed towards completion of the eel life cycle under artificial conditions as such research has high potential impact on recovery of endangered stocks and sustainability of an important aquaculture sector.

The various life stages of eel that were considered are: glass eels and juveniles, on-growers, and marketable fish. A review of environmental conditions and factors that were identified as possibly affecting the welfare of European eel at those different life stages has been conducted. These factors are grouped as: abiotic environmental conditions, biotic factors (including behavioural interactions), food and feeding, husbandry and management, genetics, and the impact of disease and disease control measures. It is however important to realise that the environmental conditions are always defined by a range of inter-related factors. While each specific variable is described separately, there are very few occasions in reality where only a single factor is involved in any fish welfare issue relating to environmental conditions. For this reason, only ranges of acceptable levels for the various factors can be given and always these must be considered in the context of the other variables involved.

There are various methods for the capture of glass eels for farming purposes which have varying levels of welfare concern for the subsequent maintenance of the stocks in the farm. Currently, in Europe, extensive culture systems have been almost entirely replaced by the high technology high density intensive systems.

There is very little scientific literature that specifically addresses the welfare of eel under farming conditions. However, it was possible to overcome such a paucity by extrapolating from existing peer reviewed publications, and using expert opinion, in a risk assessment approach. The conclusions and recommendations are based on the scientific literature review and the performed risk assessment.

Major welfare issues for glass eels were identified as being: skin damage associated with consequent osmoregulatory failure, tail damage and damage to the caudal sinus associated with secondary infections, stress and demucinisation during storage and handling (post capture). These hazards occur frequently (if not invariably), affect a high proportion of the glass eel population, and are severe. Injuries and mortalities are recorded amongst fished glass eel and the number of mortalities is linked to the speed, depth and net used in active trawling. It is recommended that the capture of glass eels for farming purposes be addressed to reduce the highly significant poor welfare of glass eels during the process. During capture and post-capture storage, temperature is a critical hazard for glass eels.

For juveniles, the most significant hazards identified are: weaning, artificial food training, parasitic infections and disease management methods (exposure to herpes virus). Ineffective weaning and artificial food training received a relatively low score in our analysis because only a small minority of farms would be affected. Nevertheless the hazard is severe, prolonged and results in death in the eels affected.

For on-growers, infectious diseases remain a significant problem during this life-stage; but this is normally less severe compared with the juvenile stage.

Among the hazards that were identified for marketable fish, rapid reduction in water temperature was seen as the most important.

For all life stages of the European eel, water pH is important, mainly to control the level of ammonia. Also for all life stages, infectious diseases are a primary source of poor welfare despite good management. The lack of efficient treatment and vaccines increases the significance of this hazard. It is recommended that research be directed toward these issues.

Where parameters have been identified as having a welfare implication for eel, it is recommended that these parameters be monitored. Without continuous recording and monitoring, the use of alarm systems, and a reliable emergency backup even relatively small failures in husbandry systems can produce disastrous outcomes in terms of welfare.

It is also recommended to develop contingency plans to protect fish welfare from exposure to rare and brutal hazards.

DISCLAIMER

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.

On 29 January 2009 the AHAW Panel adopted an opinion on the general approach to fish welfare. This provides an overall approach regarding the welfare, biology and physiology of fish. It addresses and satisfies all the issues outlined in the minority opinions recorded in relation to AHAW Panel opinions previously adopted on the welfare of individual fish species. This minority opinion is therefore superseded in the light of the opinion on general approach.

European eel, Anguilla anguilla, animal welfare, risk assessment, fish farming, husbandry system, aquaculture, environmental conditions, biotic factors, feeding, disease