Weight−length relationships (WLRs) for 28 fi sh species were investigated in an enclosed basin in the Sea of Marmara. Due to low sample sizes (<15), 11 species were not taken into account, but length results were represented. WLR information for 8 species was taken for the fi rst time in the Sea of Marmara, and these 8 species were examined according to sex. Parameters b were found to be insignifi cant between the sexes (P > 0.05). In this study, WLRs for Pomatoschistus marmoratus are presented for the fi rst time in Turkish waters. Additionally, this study represents the fi rst results for the entire Sea of Marmara and carries signifi cant importance for the WLR database in light of previous studies, which only provided information for limited parts of this sea.