SPECIES AND SIZE-SELECTIVITY IN A PORTUGUESE MULTISPECIES ARTISANAL LONG-LINE FISHERY

The species and size selectivity of long-lines using small hooks were studied off the south coast of Portugal using ''Mustad'' brand round b ent, flatted sea hooks (Quality 2316 DT) numbers 15, 13, and 11 baited with razor shell clam (Ei-isis siliqua). Hook numbers 13 and 11 are 4 9 and 109% larger respectively than number 15 hooks in terms of overal l size (maximum width x maximum length). A total of 39 900 hooks were fished in 45 sets and 35 species of fish and cephalopods were caught. As a group, 13 species of sea breams (Sparidae) dominated the catch by numbers (58%) and weight (73%). Six species of sea breams, along with the greater weever fish (Trachinus draco) accounted for 81% of the to tal catch by weight, with the common or white sea bream (Diplodus sarg us) bring the most important (29%). Catch size distributions by hook s ize were, in general, highly overlapped for all species and hook size had little apparent effect on minimum size at capture. All hooks caugh t a wide range of sizes per species, but the catch rate (number of fis h per 100 hooks) was significantly lower for the largest hook. Except for the black sea bream (Spondyliosoma cantharus), capture of illegall y sized or immature fish was minimal. Small increases in average size with hook size were evident for four species: Diplodus sargus, D. vulg aris, Lithognathus mormyrus and Serranus cabrilla. No differences in s ize selectivity were detected for Boops boops, D. annularis, Spondylio soma cantharus and Trachinus draco. A skew-normal model adequately des cribed differences in size selectivity in five of six species. (C) 199 6 International Council for the Exploration of the Sea