Summary Length–weight relationships for 47 coastal fish species from Gökceada Island in the northern Aegean Sea, Turkey are presented. Samples were caught in depths of <30 m by gill and trammel nets between March 2004 and February 2005. The most abundant families were Sparidae (30%), Centracanthidae (19.9%), Serranidae (7.14%), Scorpaenidae (6.59%) and Labridae (6.09%). Estimates for parameter b of the length–weight relationship (W = aLb) ranged between 2.08 and 3.73. The mean b‐value 3.03 ± 0.052 (SE) was not significantly different from 3. Significant differences between b‐values were found between sexes for Boops boops, Diplodus annularis, Mullus surmuletus, Pagellus acarne, Sarpa salpa, Spicara maena and Spicara smaris and between seasons for Diplodus annularis, Mullus surmuletus and Spicara maena.

Fishing trials were carried out with gill nets and trammel nets in the northern aegean Sea from March 2004 to February 2005. Four different mesh sizes for the gill nets and the inner panel of trammel nets (16, 18, 20 and 22 mm bar length) were used. Selectivity parameters for the five most economically important species, bogue (Boops boops), annular sea bream (Diplodus annularis), striped red mullet (Mullus surmuletus), axillary sea bream (Pagellus acarne) and blotched picarel (Spicara maena), caught by the two gears were estimated. the SeLeCt method was used to estimate the selectivity parameters of a variety of models. Catch composition and catch proportion of several species were different in gill and trammel nets. the length frequency distributions of the species caught by the two gears were significantly different. the bi-modal model selectivity curve gave the best fit for gill net and trammel net data, and there was little difference between the modal lengths of these nets. However, a clear difference was found in catching efficiency. the highest catch rates were obtained with the trammel net. Given that many discard species and small fish are caught by gill nets and trammel nets with a mesh size of 16 mm, it is clear that these nets are not appropriate for fisheries. Consequently, the best mesh size for multispecies fisheries is 18 mm. this mesh size will considerably reduce the numbers of small sized individuals and discard species in the catch.