CHARACTERISTICS OF HATCHING TIME AND DAILY INCREMENTS CONFIRMATION OF OTOLITH IN GYMNOCYPRIS POTANINI LARVAE AND JUVENILE

Gymnocypris potanini Herzenstein, an endemic freshwater species in China, distributes in the upper reaches of the Minjiang River and the Lancang River and some plateau areas with low water temperature even in the summer. The present study investigated the morphological characteristics, formation period of increment, and hatching date of G. potanini. Larvae were identified by COⅠ sequences, which were caught in the Mengtun River at 2015 and 2016. Homology analysis showed that the COⅠ sequence of captured larvae and juvenile were genetically similar to G. potanini and then identified as the G. potanini. The shape of lapilli finally changed into mussel shape, whereas sagittae became wedge-shaped, the long ellipse shape, and eventually changed into long pointed. Then one increment of lapilli by marked temperature was formed every day. The number of marked increments on lapilli were linearly related to the age, and the slopes of the equations were closed to 1.0 (P>0.05). These results demonstrated a daily formation of otoliths increments. By counting the number of daily increment and confirming daily pattern of the increment deposition, the back-calculated hatching dates of the larvae were from 29 June to 15 July in 2015 and from 13 July to 18 August in 2016, indicating that G. potanini has a long spawning period in late summer. These results provided important information on the spawn time of estimation and the basic data for resources conservation of G. potanini.