Moutopoulos D.K., Dimitriou N., Nystas T., Koutsikopoulos C. 2017. Length-girth relations of fishes from a Mediterranean lagoon system. Acta Ichthyol. Piscat. 47 (4): 397-400. Abstract. We estimated the relations between total length (TL) and opercular (G ope) and maximum (G max) girths, for the eight most representative lagoon fish species in Mesolonghi-Etolikon lagoons within 2015-2017 (June through December). The following species were studied: Chelon LGR estimates were not available. Results showed that both G ope and G max increased significantly linearly with TL for all studied species with all r 2 values being higher than 0.862. When G max values were plotted against TL for all species combined, two significant (ANCOVA, P < 0.05) length-girth relations were identified corresponding to different body shapes. The implications of girth measurements for lagoon gear selectivity estimates are also discussed.