Study On The Biology Of Mystus Pluriradiatus(Vaillant) In Yuanjiang River

Age and growth, feeding habits and reproductive characters of Mystus pluriradiatus (Vaillant) were studied based on 482 specimens collected from Yuanjiang River, Yunnan Province, during July 2008 to June 2009. The main results are shown as follow.1. After comparison, it was found that asteriscus is a suitable age-determining material, and lapillus and vertebra can be used as ancillary materials. The relationship between body-length (L) and radius of annuli (R) on asteriscus is L=139.54R+30.491 (r2=0.945, n=204). Furthermore, the weight of lapillus (Wo) is closely related to the age of M. pluriradiatus (A) and their relationship is Wo= 0.0008 e0.4494A (r2= 0.879, n= 216).2. There were 4 age-groups in the capture of M. pluriradiatus, dominated by individuals of 1+ and 2+ age-groups which together accounted for 83.16% in total catches. The dominant body-length groups were 115 mm to 174.7 mm (accounted for 79.87%) and dominant body-weight groups were below 70 g (accounted for 84.16%).The relationship between body-weight and body-length is W= 0.0212 L 2.8292 (r2= 0.9465, n= 303). The growth of M. pluriradiatus fits in with von Bertalanffy growth formula. The VBGF and parameters are as follow:The inflexion point (ti) of body-weight growth curve is at 2.68 a.3. M. pluriradiatus is a carnivorous fish mainly feed on small fishes and aquatic insect larvae. Small fish had an average occurrence rate of 64.2% and accounted for 46.90% in weight in the stomach content. Aquatic insect larvae had an average occurrence rate of 73.8% and accounted for 40.00% in weight together with insect imago. M. pluriradiatus also is a euryphagous fish feeding on a wide range of food items including mollusc, annelida, crustacean, fish eggs, frogs, rotifers, cladoceran, copepoda, cereals, macrophytes and etc. M. pluriradiatus is a guttler. Its stomach fillness index can reach 11.6%-16.2% at satiation. As the body-length increase, its food composition simplified and feeding intensity decreased. 4. M. pluriradiatus spawns in single batch in one year. Its spawning season is from April to July. Females matured mainly at 3-year-old and males at 2-year-old. The sex ratio at spawning season was 1:0.8704. The females'GSI of 1-4 age groups were 1.802%, 4.389%,9.772% and 10.719%, respectively. The absolute fecundity (F) varies from 790 eggs/ind. to 2115 eggs/ind., with an average of 1483 eggs/ind.; the relative fecundity F/W0 varies from 9.22 eggs/g to 17.22 eggs/g body-weight, with an average of 13.37 eggs/g.