Current methods for capture, handling and tagging wild fish

Niels Jepsen

Danish Institute for Fisheries Research

Silkeborg

In practical field based studies, wild fish are often captured, handled and tagged in order to gain essential knowledge of their behaviour, migration and survival. Traditionally this tagging was rather non-invasive external attachment of small identification tags. However, during the last two decades, electronic tags have been used increasingly. It is beyond doubt that the information gained from telemetry studies have significantly improved our understanding of fish behaviour in general and lead to more efficient management and conservation. The most common way of tagging fish with telemetric transmitters is surgical implant. This method is rather invasive and requires anaesthesia and surgical procedures. Field researchers are faced with several constraints when working with wild fish and the general rule of thumb is to “keep it simple”, so surgery is often performed under very primitive conditions far from what is recommended in laboratory experiments. In this presentation I wish to provide an insight in the way we treat wild fish in tagging studies and what is done to evaluate and refine the methods used.