Fish bycatch and discarding in Nephrops trawlers in the Firth of Clyde (west of Scotland)

Nephrops norvegicus (Norway lobster or prawn) is an important target specie s in demersal fisheries of the north-east Atlantic. Trawling for Nephrops i s wasteful when many small fish are caught and discarded in the process. He re, data from 106 commercial fishing trips, sampled between 1982 and 1998 a s part of the Scottish discard sampling programme, are used to investigate the fish bycatch and discards of Nephrops trawlers in the Firth of Clyde (w est of Scotland). A large proportion of the fish caught in the Clyde is dis carded, the discards mainly consisting of small demersal fish (mean length about 19 cm), particularly young whiting (Merlangius merlangus). Within the study period, annual estimates of total fish discards ranged from 318 to 3 027 tonnes, with a mean of 1761 tonnes. Fish landings and discards biomass per unit effort both decreased over the study period. However, the decline in landings per unit effort was greater than that in discards per unit effo rt, corresponding to an increase in the discard rate over time. In recent y ears, discards have comprised about 70% of the fish bycatch. The mean lengt h of discarded fish was positively related to mesh size. (C) 2001 Ifremer/C NRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS.