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Behavior research12 Fish as pets From a statistical viewpoint, fish are the third fa- vorite pets. However, we still find it relatively difficult to make contact with these very distant relatives. They cannot make themselves understood neither by ges- ture nor by sound. We are not familiar with their living environment. They are nevertheless sensitive creatures and not easily replaceable decoration items. Although or maybe especially because their horizon of experi- ence and their emotions strongly differ from ours, we should try to find out when a fish that we keep really feels well. An appropriately kept aquarium or pond allows the kept animals to lead a life relatively natural and according to their requirements. Unlike, for instance, many dogs and cats, ornamental fish are ideally kept in an environment close to nature that allows keeping them together with members of their own kind as well as reproducing. Optimal, stable conditions in the water are, however, rather difficult to maintain, especially in small tanks. To make things worse, the actual require- ments are often poorly researched so far. Definition of welfare It as very complex task to recognize these re- quirements, in other words to define welfare on a sci- entific basis. It is not sufficient to just measure isolated factors such as mortality or the growth rate. Besides these factors that objectively affect health, the subjec- tive preferences of the animals should also be consid- ered, provided they can be made measurable by be- havioral research. This is accompanied by the question for the behavioral repertoire of the fish in the wild (e.g. migration or schooling behavior). There is, unfortu- nately, still plenty of research required for many species before the findings can be formulated in practical keeping recommendations. Beyond these observations one should not for- get that fish living in the wild are also confronted with considerable impacts to their welfare (e.g. predators, hunger, diseases, unfavorable environmental condi- tions). Only few fish survive until they become sexually mature. This is in no way supposed to justify poor keeping conditions, but it shows that due to their evo- lutionary adaptation, fish are basically able to cope with these challenges in their environment. Stress reaction – an adaptation strategy Stress reactions are an important adaptation strategy for overcoming such problems. Upon contact with stress factors, the (fish) body reacts with a number of physiological changes (among others, by releasing the “stress hormones” adrenaline and cortisol, by in- creasing the heart and blood circuit performance, and by mobilizing energy) that make the fish more resistant in this exceptional situation. Long-term stress reac- tions, such as reducing food uptake, stopping repro- duction, weakening the immune system and affected growth, also first support overcoming the stress caus- ing situation. In the long run, however, they themselves become a problem which considerably reduces the welfare of the fish and may lead to disease and death. by Elena Rathgeber Fish welfare – Not a merely ethical consideration Part 1 ©Dobermaraner–shutterstock.com

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