| From Feb.1999 to Dec.2000, 562 specimens of A nigrocauda were collected from laixi river,a branch of the Tuojiang river.The study provided foundation to the protection of the natural resources of A nigrocauda.Moreover,this study accumulates biological data for Ancherythroculter.Yih el Woo fishes also.562 specimens were.aged by the sèale.at the same time,260 specimens vertebra were used as material for comparison.The rate of coincidence between scale and vertebra was89%.Analysis of. the catch showed that it mainly consists of LI-Ill year-old fish,with a body length of 7.6—29cm,and a body weight of 3.8-365.42 g respectivelyThe correlation formula for radius of the scale and body length, the body length and body weight were selected as follow:L=5 . 8x+4. 177 (x- 10 X R,cm;R-ridius of the scale,mm;L-body length,cm)W=0.0064 L3~270' (W-body weight,g)The growth of A nigrocauda fits in with Von Bertalanffy equation .The parameters and equations for growth are as follow:L.~=44.426cm W~=1 539.15(g) k=0. 153 to~=-0.624(year)tr7. I 12(year) Lr 30.75(cm) Wr =466.85(g)Lt=44.426[ I ~e~I532(t+O6243)]Wt 1539.1 5[ 1 -e0 1532(t+O.6243) j3.2701The indices of growth and the amount of products on yearly increments of length and weight depended on the growth-equation indicate that the fastest growing period of length is in the age of I-lI years.Based the statistical analyses of the fi.llness (K)of 562 specimens , liver-somatic4index(LSI) of 217 specimens and coefficient of maturing(M) of 375 specimens It was found that K is correlated to seasonal changes.. body length developmental stage of gonado and sex,and LSI is related to seasonal changes.. developmental stage of gonado ,but not to sex. M is related to seasonal changes and sex.From the statistical analyses of stomach contents of 84 specimens we found that A nigrocauda feeds mainly on shrimps. Ingestion rate of A nigro~auda was especially high from April to Novemmber, and especially low from December to March,we inferred that the ingestion rate of A nigrocauda changes with aboundance of preys in the river.According to external characteristics, the development of the ovaries was divided into 6 stages, and in winter ovaries are at stage liThe spawning season was from April to iuly.The M of ovary varies from 0.4%-22. 1%.According to external characteristics, the development of the testis was divided into 6 stages also, and stage V were found in April to July with higher M in this season.A nigrocauda has a single spawning season from April to July each year when the natural water temperature is at 17-260C.The spawning grounds by the river is weedy with the water flowing slowly. Sex ratio of the female to the male fish is about 1:1 in spawning season.One year old in male and two years old in female A nigrocauda reach their first maturity. Both male and female fish of A nigrocauda own much white sharp and coarse pearl organs on lips..checks..fins..operculer and head in spa'vning seasons.The ripe eggs are ball-like and sticky with deep yellow colour,they are 0.65-1 . 12mm in diameter with an average of 0.88mm.The fecundity of 64 specimens in A nigrocauda was studied. The absolute fecundity F varies from 4541-114356 eggs, with an average of 35726.8 leggs;the relative fecundity F,t varies from 273.55-4462.61 eggs/cm, with an average of 1604.O3eggs/cm;the relative fecundity FIW0 varies from 42.76-601.4 eggs/g,with an average of 277.28 eggs/g.the relationships between absolute fecundity F and body length (L,cm).. net weight(Wo,g)-. product of body length with net body weight (LXW0).. age.. coefficient of maturing(M) can be expressed as: F=8836.1L-144784(r=0.86P<0.01N=64) F=424.91W0-9538.2(r~0.9045P<0.01N64) F=14.617617LXW0+3527.9(r=0.8952P<0.0lN64) F=15611t-17944(r=0.4123P<0.01N=64)F~330646M-3211.6(r=0.703p |
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