STUDIES ON THE ONTOGENY, GROWTH AND DAILY INCREMENT OF OTOLITHS IN LARVAE AND JUVENILES OF SCHIZOTHORAX PRENANTI

We performed observation and analysis on the development of the otoliths of larvae and juveniles of Schizothorax prenanti in the laboratory from 2013 to 2014. The procedures were carried out at the hatching temperature 13.5-17.2℃. Lapilli and sagittae formed before hatching, and the asteriscus first appeared on the 12th day post hatching (DPH 12). Lapilli and sagittae had rounded shapes at hatching. As developed the shape of lapilli finally changed into reniform, whereas sagittae became wedge-shaped, the long ellipse shape, and eventually changed into long pointed posterior. The shape of the asteriscus remained mussel-like during the development. The growth of the anterior, dorsal and ventral areas of lapilli, and ventral and dorsal areas of sagittae showed an exponential pattern. The growth of the posterior area of lapilli, and the anterior and posterior areas of sagittae was linear. Furthermore, the summed length of anterior and posterior radius in sagittae and lapilli were linearly related to the total length of the larvae and juveniles. The first increment on the sagittae of larvae appeared on DPH 2 (18 hours post hatching and 19 hours post hatching) at (18.50.5)℃ and (15.61.1)℃. Then one more increment of lapilli and sagittae was formed each day. The number of increments on lapilli and sagittae was linearly related to the age, and the slopes of the equations were close to 1.0 (P0.05). These results demonstrated a daily formation of otoliths increments. Furthermore, our study provided more clues on the ecological characteristics of Schizothorax prenanti, including breeding seasons and the development at early stage.