This study was carried out to uncover the relationship between opercular girth (Gope), maximum girth (Gmax) and total length (TL) for eight fish species [(Sardina pilchardus (Walbaum, 1792), Sardinella aurita (Valenciennes, 1847), Serranus cabrilla (Linnaeus, 1758), Serranus scriba (Linnaeus, 1758), Symphodus mediterraneus (Linnaeus, 1758), Symphodus tinca (Linnaeus, 1758), Trachurus mediterraneus (Steindachner, 1868), and Trachurus trachurus (Linnaeus, 1758)] from four families (Carangidae, Clupeidae, Labridae, and Serranidae) sampled between August 2016 and December 2017 in Saros Bay (Northern Aegean Sea, Turkey). Gope and Gmax were found to increase linearly with the total length for all the species. All r2 values were statistically significant (r2 > 0.83, P < 0.001). The values about length-girth relationships (LGRs) of S. mediterraneus were estimated for the first time worldwide. This information will contribute to the development of ecosystem-based fisheries management.