Otolith shape analysis and growth characteristics in larval and juvenile Squalidus argentatus

Otolith microstructural features and morphological development of larval and juvenile fish are important for studying the early life history of fish. In this study, the analysis of otolith features was performed on Squalidus argentatus laboratory-reared larvae and juveniles (0 to 40 days post-hatching or dph) collected as eggs in the Laibin section of the Pearl River (South China) from April to August 2020. According to the otolith development analysis, there was a corresponding relationship between the development of otoliths and the ontogenesis of fish, in which the shape of otoliths had a greater change in the post-flexion larval stage corresponding to the formation period of each fin. Observations of the microstructural features suggested that lapilli were the most suitable otoliths for age determination and increment deposition rate validation among the three pairs of otoliths. The result of a regression analysis of the number of lapilli increments on age indicated that otolith growth increments were deposited daily and the first increment was deposited at 3 dph. Our results support the usage of otolith increment deposition rate when assessing hatching dates and daily growth for wild S. argentatus at 40 dph when environmental conditions are comparable to those described in this study.