The feeding behaviour of some demersal fish species in response to artificial discarding

Abstract

In an attempt to detect changes in the diet and the feeding intensity of demersal fish caused by fishery discarding, two hauls were carried out 22 h apart at a depth of 90 m in an area of the Cantabrian Sea closed to trawling. Before the second haul, dead fauna that were not common in the sampling area under natural conditions, such as Micromesistius poutassou and squat lobster (Munida spp.), which are both usually discarded by the fleet and mainly found in deeper water, were thrown overboard. A total of 319 stomach contents from 12 demersal fish species caught in both hauls were analysed. The percentage emptiness decreased in the second haul (32%) with respect to the first (43%), and at the same time the feeding intensity of scavenger species such as Trachinus draco, Pagellus acarne, Scyliorhinus canicula, Raja montagui and Leucoraja naevus increased. Discards of M. poutassou was actually found in the stomach of a typically planktophagous species, Pagellus bogaraveo. Observed changes in trophic structure of the species analysed as a response to discards are discussed.