An empirical comparison of sex ratio, condition factor and length–weight relationships in Mediterranean horse mackerel from the Sea of Marmara, the Middle and Eastern Black Sea

Abstract

Fish length–weight relationships are essential for estimating biomass and assessing fish population health, typically showing low variation within and between neighbouring stocks. This study investigates the length–weight relationships of Mediterranean horse mackerel (Trachurus mediterraneus) collected from the Sea of Marmara, the Middle Black Sea, and the Eastern Black Sea in Türkiye during 2022. In addition, the study assessed the sex ratio and condition factor of Mediterranean horse mackerel at each station, alongside an examination of length-frequency samples, providing a comprehensive analysis. The one-way ANCOVA analysis showed no significant differences in length–weight regression between the sexes. However, it identified a considerable area effect, with samples from the Sea of Marmara significantly differing from those in the middle Black Sea and Eastern Black Sea. Fish samples from the latter areas displayed moderate length–weight variation, which was close to the significance threshold with a p-value of 0.069. The growth pattern of Mediterranean horse mackerel consistently exhibited negative allometry across all sampled areas for both males and females, except for female Mediterranean horse mackerel from the middle Black Sea, which tended to follow an isometric growth pattern. This study revealed consistent results within neighbouring areas (Middle Black Sea and Eastern Black Sea) and significant variations when comparing the Black Sea and Sea of Marmara Mediterranean horse mackerel, emphasising notable large-scale spatial trends.