Limited mid-water scavenging of trawl discards

The consumption or scavenging of ¢sh in the water column at depths from 75 to 275m in Algarve (southern Portugal) trawl ¢shing grounds was evaluated. Longlines were used to suspend baits throughout the water column while electric ¢shing reels were used to simulate sinking discards. Eighteen species were caught, with higher catch rates near the surface than near the bottom. However, scavenging rates were generally highest near the bottom and lowest in the middle of the water column. At depths less than 100m the majority or all the ¢sh were scavenged throughout the water column, while at depths greater than 200m most of the ¢sh were untouched after periods of time greater than would be required for them to sink to the bottom. Since other studies have shown that most small ¢sh discards are scavenged at the surface by sea birds and most of the discarded species that sink are either too large or not attractive to pelagic predators, these results suggest that mid-water scavenging of trawl discards in deep water is relatively unimportant.