Length-girth relationships of 24 marine fishes in the northern Aegean Sea (eastern Mediterranean Sea)

Abstract

The knowledge of morphological relationships and particularly of those concerning fish body girth (G) with total length (TL) is necessary in gear selectivity and specifically the technical measures to avoid capture of undersized individuals. This study concerns 24 marine species exploited by the small-scale coastal fleet in the Aegean Sea (eastern Mediterranean Sea), for 6 of which, the TL-G relationships are mentioned for the first time in the Mediterranean Sea and the adjacent seas. Samples were collected seasonally, from April 2016 to February 2017. The coefficients of the linear regression of body girth in three body positions, (Geye, posterior to the eye; Ghead at the posterior end of the operculum; Gmax at the maximum body depth), with the total length were estimated for each species and for the groups formatted when Geye, Ghead and Gmax were plotted against total length for all the species combined. Statistically significant differences among the three groups were detected (ANCOVA, P<0.001). Comparison of the total length-body girth relationships for 18 species previously studied in different geographic areas of the Mediterranean and the adjacent seas, showed differences mainly with the results from Portuguese waters for certain species populations. Based on the resulted equations, the maximum girth (G max) corresponding to the Minimum Conservation Reference Size (MCRS) and to the total length at maturity (L m) were calculated for each species. Identified mesh sizes respective to G max values were quite larger than the minimum legal mesh size for gillnets and the inner sheet of trammel nets, indicating that the relevant current fisheries regulations cannot meet the requirements for sustainable exploitation of fish resources.