Fluctuating asymmetry in otolith dimensions of Trachurus mediterraneus collected from the middle Black Sea

Abstract

Asymmetry is crucial in the natural world and assumed to reflect the developmental instability of the fish in polluted aquatic habitats. Trachurus mediterraneus are a commercially important species living at different depths in the Middle Black Sea. In aquatic habitats, high level asymmetry occurs in more stressed fish, and these fish consume more energy to buffer their growth than fish that are not under stress. A total of 88 specimens were collected in the Middle Black Sea and their total length and weight ranged from 119-164 mm and 11.14-35.09 g. There were significant differences between the right and left sagittal otolith measurements (P<0.05). There were no significant differences between males and females’ otoliths measurements of the species (P>0.05). The asymmetry was calculated for the sagittal otolith characters such as area, width, length, and perimeter. The present study results indicated that otolith width has the lowest asymmetry value (4.337) while otolith length has the highest asymmetry value (8.717) among the four otolith characters obtained for the male and female of Mediterranean horse mackerel collected from the Middle Black Sea. Overall, developmental instability as fluctuating asymmetry levels within total length classes could be a relevant indicator of pollution in the habitat.