Fluctuation asymmetry of otoliths from Coilia brachygnathus in Changhu Lake: A first study in inland waters of China

Abstract

Fluctuating Asymmetry (FA) in fish otoliths is an indicator of arbitrarily tiny variations between bilateral otolith characters, and it serves as an effective indicator of growth and developmental differences due to environmental conditions. Due to their unique resident traits, the Coilia brachygnathus can provide a potential insight to the environmental pressure reflected by its otolith FA. In this study, 228 C. brachygnathus from Changhu Lake were examined, assessing the Asymmetric Square Coefficient of Variation (CV²_a) across four characters: the length, width, perimeter, and area of the left and right lateral sagittal otoliths. Results showed that otolith length exhibited the lowest CV²_a, while otolith perimeter displayed the highest. Although no clear pattern emerged in the change of CV²_a with increasing body length for each otolith character, the CV²_a of otolith width within the 160–180 mm body length group was significantly higher than that in the 120–140 and 220–240 mm groups. Generally, otolith CV²_a within the middle and upper lake sections surpassed that in the open water sections of the lower reaches. Our findings indicated that ontogenetically, variations in C. brachygnathus otolith FA are linked to its feeding and habitat preferences, while the spatial responsiveness of otolith FA to environmental pressure warrants further exploration. Future studies will encompass the collection of otolith FA data from additional Coilia species, with particular emphasis on distinguishing migratory and sedentary Coilia, ultimately enhancing the reliability and precision of environmental pressure assessments in inland waters.