Glass eel index catch efficiency - experiment

Summary

Glass eel index monitoring is executed using two methods: liftnets and glass eel detectors (ELFI). Based on recent results, timing of peaks in catches and timing of periods of catches differs between the methods. It is suggested that each method has its own catch selectivity in relation to the proportion of ‘active glass eels’ which is related to water temperature. A lift net catches both passive as well as active swimming glass eels in different ratio’s during the season, while an ELFI only catches active swimming glass eels. This may underestimate glass eel abundance estimations. In order to optimise glass eel abundance calculations a better understanding is needed to correct for selectivity in relation to activity of the glass eels. This KB WOT Fisheries proposal studies catch selectivity of an ELFI throughout the migration season by exposing glass eels caught by a lift net and an ELFI to different water temperatures and calculate catch efficiency in an experiment.