Preliminary Studies On Age, Growth And Reproduction Of Yellow Catfish Pseudobagrus Nitidus In Nanchang Section Of Ganjiang River

The age, growth and reproduction of Pleteobagrus nitidus, a kind of yellow catfish in Nanchang section of Ganjiang River, were studied by 251 samples obtained between May and June 2009. The aim of the present study was to understand the biological characteristics and population structure, which could provide the basic information for the conservation and management.Lapillus and Neural Spine Complex(NSC)were used in age determination. Both had good interpretability and reproduction rate in age estimation of Pleteobagrus nitidus. The relationship between the lapillus radius(R) and body length (BL) of Pleteobagrus nitidus from Nanchang section of Ganjiang River was linear and there was no significant difference in the formula between males and females. But the R2 was low compared with that of NSC and the fitting in the linear formula of NSC and body length was better. The body length-weight relationship can be described by the following equations:W=0.0244×BL2.723. The age structure of Psedobagrus nitidus in Nanchang section of Ganjiang River was simple, which had only three age groups. The 1 age group accounted for 27.34 % of all samples, the 2. age group accounted for 71.88% of all samples and only one specimen of 3 years old was observed. The dominant body length group and the dominant weight group were 90-126mm and 10-20g, respectively. The maximum body length and maximum weight collected in the catch were 126 mm and 26.1g, respctively.The primary sexual character Pleteobagrus nitidus is very obvious in the mature individuals. The whole sex ratio was near to 1:1. Most of female and all of male Pleteobagrus nitidus could sexually mature at 1 age, and all of the female could sexually mature at 2 ages. The smallest individuals at first maturity for both sexes were:88mm in body length and 8.5g in body weight for female with ovary weight 0.1g and 82mm in body length,7.1g in body weight for male. The individuals absolute fecundity was 212-2861 eggs and the relative fecundity was 19.9-280.5 eggs/cm for body length with mean 235.78 eggs/cm for body length. The relative fecundity for body weight was 15.8-233.9 eggs/g with mean 7.38 eggs/g for body weight. The egg diameter was distributed in two groups of 0.5 mm-1.2 mm and 1.3 mm-2.0 mm, nearly 50/50 between the two egg groups, which suggested that the spawning pattern of Psedobagrus nitidus would be in batches.