STUDIES ON THE OTOLITH MICROSTRUCTURE, THE DAILY AGE AND THE GROWTH OF CULTER ALBURNUS JUVENILES AT EARLY DEVELOPMENTAL STAGES IN THE MUDONG SECTION OF THE THREE GORGES RESERVOIR

We collected ninety-seven juveniles of Culter alburnus in the Mudong reach of the Three Gorges Reservoir (TGR) from September to October in 2013. We examined the otoliths to estimate their hatching period and growth during the early developmental stages. The typical body length of the juveniles ranged from 40 to 98 mm. Their otoliths were in anomalistic and elliptic shapes and had one rostral protrusion. There was one nucleus and one primordium on the transverse plane of the otolith. The diameter of the primordium ranged from 11.6 to 27. 8 m and the mean value was 18.63.8 m. The distance between the central nucleus and the first increment was 13.04.7 m. The hatching period of these juveniles ranged from 44 to 104 days. Thus, we estimated that their hatching time window was 9 June to 17 August in 2013, and the peak period was from 9 July to 22 July in 2013. There was a significant linear relationship between the radius of the otolith, the daily age, and the body length (P0.05). The increments of the Otolith constantly changed, indicating a continuous change in the growth rate of C. alburnus at the early developmental stages. The average daily growth rate was 0.774 mm/d.