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Identification of two hatch-date-dependent cohorts, and variation in early growth rate of mud carp (Cirrhinus molitorella) in the Pearl River Delta, China.
Cirrhinus molitorella is one of the most important commercial fish species in the Pearl River, but there are few published studies on early growth of this species. In this study, seasonal recruitment patterns, temporal variations in early growth rates and environmental variables were analysed. A total of 1512 individuals were collected during monthly sampling from July 2015 to January 2016 and ranged from 30.8 to 84.9 mm standard length (SL). A subsample of 276 juveniles was aged from 68 to 193 days old with the hatch dates between 2 February and 19 September by determining daily increments in otoliths. Monthly abundance data and SL frequency distributions showed that there were two major temporal cohorts of juvenile recruitment, which were mainly hatched in April and July. Average growth rate, estimated by the linear relationship between age and SL, was greater for the April cohort (0.49 mm/day) than the July cohort (0.37 mm/day). Mean increment widths from the 23rd increment onwards were significantly greater for the April cohort than the July cohort (P < 0.05). The slower growth observed in the July cohort was probably due to poorer food availability caused by high river discharge volumes. These results are important for predicting recruitment dynamics and managing the C. molitorella fishery.
MF17278 Accepted 23 December 2017
© CSIRO 2017