Studies On The Growing Development And Reproduce Biology Of Silurus Lanzhouensis

Silurus Lanzhouensis is an endemic fish to the upper HuangHe River.From June 2005 to July 2006,184specimens collected from Zhongwei and Shizuishan of Ningxia sections in the higher HuangHe River were used for studies on aging, age structure and growth, reproduction, the embryonic and larva development of Silurus lanzhouensis.The following are the main results:1 Vertebra could be used for aging the fish efficiently. Aging results of vertebra corresponded with that of pectoral fin in 81.94%(59:72).The annulus are laid down mainly from March to July and the ratios of the scales with new annulus increases from 26.7% to 80%。2 The commercial catches consisted of five age groups (age1to age5) and individuals of age 1 to 3 groups were dominant (occupying more than 78.5% of total capture). The body length changed from 20.0cm to 68.0cm with an average of 40.0±13.5cm; the body weight changed from 66.5g to 990.0g with an average of 530.0±14.3g; Body length (L) and body weight (W) presented a curve line: W=3×10-5L2.72013 All females and males of three years old reached maturity.The minim mature female was 20.0cm in length 60.0g in weight.The minim matures male was21.0cm in length 58.0g in weight.4 The ovary maintained in stage II in winter began to develop in March and reached maturity in July.Value of gonadosomatic index (GSI) increased in March, and decreased to bottom in July till the beginning of the next March.The spawning activities of the fish could last from May to July.5 The results of this paper in dicate that this fish spawns only once a year.6 The Silurus lanzhouensis is one of the important economic fishes. Its fertilized eggs are yellowish and spherical.The diametre of a swollen egg is 3.44～3.46mm.Treated in the physiological solution.When the water temperature is 21.5～23℃.The larvae will be hatched in 30 hours and 20 minutes.The newly hatched larva is about 4.60～5.80mm long.The fry grow fast and become 19.0～24.5mm long in 9d.