Length-weight relationships were estimated for 18 fish species and a Cephalopod species from 17 families. A total of 3433 individuals were caught from the coasts of Gokceada Island, Northern Aegean Sea, Turkey. Pagellus acarne, P. bogaraveo, Gadiculus argenteus, Scyliorhinus canicula, Lepidopus caudatus, Capros aper, Lepidorhombus boscii, Hoplostethus mediterraneus, Ophidion barbatum, Helicolenus dactylopterus, Coelorinchus caelorhincus, Argentina sphyraena, Lophius budegassa, Chlorophthalmus agassizi, Lepidotrigla cavillone, Conger conger, Engraulis encrasicolus, Serranus hepatus and Illex coindetii (Cephalopoda) were collected by commercial trawl from the coasts of Gokceada Island. The slopes (b) of the length-weight relationships ranged between 2.5091 and 3.4807 with a mean of 3.0265. All length-weight relationships were highly significant (p < 0.0001). This paper provides valuable information for biological studies and stock assessments of these fishes in fisheries management and decision-making processes.