Survival of small-spotted catshark (Scyliorhinus canícula, L.) discarded by trawlers in the Cantabrian Sea.

Abstract

Discards represent a significant percentage of the total catches (up to 35%) in the north of Spain trawl fishery. In the Cantabrian Sea (southern area of the Bay of Biscay), the estimated average total annual catch of small-spotted catshark (Scyliorhinus canicula) is approximately 1500 tn, from which 80% is discarded. Several experiments have been carried out in order to estimate the survival-rate of the small-spotted catshark caught by commercial trawlers in this area. The estimate of mean survival-rate from tagging surveys was 90% while from commercial trawlers it was 78%. Several factors potentially influencing the survival-rate (sex, length, maximum depth fished, sorting time and trawl duration) were examined. No significant differences in survival-rates were found between males and females, and no strong relationships between survival-rate and depth fished, sorting time or trawl duration were evident. In commercial trawlers survival-rate was not dependent on the fish length.