SEARCH STRATEGIES OF FISH ACROSS HIGHLY VARIABLE ENVIRONMENTS

Since the environment is complex and the distribution of prey is unpredictable and dynamic, a key problem facing predators lacking complete information about their environment is finding sufficient food. Given that optimal foraging theory (OFT) predicts that predators should forage in order to maximise net energy gain, search tactics employed by predators should lead to movements that maximise the probability of encountering prey and thus increasing foraging efficiency. So how should philopatric predators behave in the light of these predictions, given that they can build up a knowledge of where the richest prey patches are located?

Analyses of field data are providing valuable information on the space-use and movements of wild adult catsharks (Scyliorhinus canicula) in a semi-enclosed marine lake (lough). Sharks are fitted with acoustic transmitters and are tracked in real-time at high spatial and temporal resolution using a radio-linked acoustic positioning system. Movement patterns are then analysed using custom-written software. The field studies are complemented by laboratory experiments to understand how prey field complexity influences foraging efficiency, and whether predators adapt to highly variable environments to maintain prey encounter rates.

People involved: Josh Filer, Professor David Sims (MBA), Professor Paul Hart (University of Leicester).

Funding: NERC, Fisheries Society of the British Isles Ph.D Studentship.