Simulating search behaviour of fish towards bait

Search by olfaction is common in many aquatic animals, and this feature is exploited by the fishing industry, which has a long tradition in the use of longlines, pots, and other kinds of baited gear. Here we discuss a range of possible search strategies that fish might apply when searching for prey; this in order to improve our understanding of fish movement dynamics towards baited gear. Various search strategies were investigated using an individual-based behavioural model. The search phase was divided into plume-search (search for relevant stimuli) and bait-search (search when an olfactory stimulus has been encountered). The search strategies were evaluated based on their efficiency in providing guidance to the goal (plume or bait). The model was developed based on previous tagging studies of cod (Gadus morhua L.). The results for plume-search show that when the landscape is considered to be continuous, strategies based on moving at an angle against the current performed better than strategies moving straight into the current, or random walk-based strategies. When it is assumed that the fish is constrained to a home range, the results are reversed so that random walk-based strategies perform better than the counter current strategies. For bait-search the counter current strategies performed much better than strategies based on gradient-search, which rarely resulted in contact with the bait. (C) 2004 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.