Marking fish

Abstract

Fish, a major world food resource, are still largely obtained by hunting wild animals rather than by farming. In 1975, 70,000,000 tonnes of wild fish were caught world wide, and the total production of farmed fish was 4,000,000 t. In Britain, 1,000,000 t were captured and about 2,000 t farmed. It is important to plan efficient exploitation of wild fish stocks, both to aid efficient fishing and for conservation purposes. Direct observations of fish are seldom possible, and so sophisticated techniques have been developed in order to study migrations, population sizes, growth rates and behaviour. These include a wide range of marks and tags: for a more detailed account, and illustrations of their use see Laird and Stott (1978). Although fish farming provides relatively small amounts of fish at present, it is a developing industry. Marks may be used to distinguish the offspring of different parents when many thousands of fish are being held in the same cages. Marks and tags are also used to distinguish fish in experimental aquaria.