Otolith Microstructure of Larval Gymnocypris potanini Herzenstein from the Minjiang River in China

Abstract

Otolith microstructure of about 120 Gymnocypris potanini larvae from the Minjiang River in China was examined and analyzed. Larvae had multiple primordia in most lapilli and sagittae, while had only one primordium in a few specimens. There had only one nucleus in otoliths of the larvae, except for some few specimens with 2 nuclei. The transparence of many otoliths differed from center to edge, and part of them could be divided into inner low optically dense zone (LODZ) and outer optically dense zone (ODZ). Based on increment clarity, otoliths of this species could be classified into three types, which were otolith with subtile increments, otolith with almost identified increments, and otolith with fairly clear increments characterized by high contrast. The last two types of otolith accounted for 87.07% in lapilli and 94.46% in sagittae, respectively. Increment clarity of sagitta was higher than that of lapillus. Natural checks were identified in 32.50% lapilli and 48.33% sagittae. These checks primarily located in the first to sixth increment. According to the number of increments in otoliths, the age of this batch larvae was 14 – 22 days, birth date was on June 17 – 25, and average growth rate of body length was 0.8936 ± 0.08769 mm/d.