Importance of Blue Whiting (Micromesistius poutassou) discarded in the diet of Lesser-Spotted Dogfish (Scyliorhinus canicula) in the Cantabrian sea

Abstract

Blue whiting is the most important demersal species caught, in landed biomass as well as in discarded biomass, by the trawl fleet in the South part of the Gulf of Biscay. Dogfish' is not commercial by-catch and it is discarded inmediately after sorting. During 1994 were accomplished analysis of 1094 stomach contents of dogfish caught in commercial ships working in a discard sampling program and a cruise research. The results reveal that from 17 cm, this especie depredates on blue whiting along all the year. The length ranges found in the stornach contents (6-31 cm) is similar to the length ranges discarded in the fishery (7-39 cm). The average quantity of blue whiting in stomachs of dogfish between 40 and 60 cm constitutes the 25% of the stomachs volume. The state of digestion in which is found the blue whiting prey, and the comparative analysis of the size distributions of blue whiting of the stomachs and the one of the fishery, presuppose that the blue whiting consumed is dead material originated from discard. Finally it is discussed the importance that this supplementary material can have in dogfish abundance.