Preliminary Studies On The Biology And Stock Biomass Of Xenophysogobio Boulengeri

Xenophysogobio boulengeri which belongs to Xenophysogobio of Cyprinidae, Gobiobotinae, is an endemic fish and lives only in the upper reaches of the Yangtze River. A total of933specimens of Xenophysogobio boulengeri were collected from October2010to October2011in the upper reaches of the Yangtze River. According to analysising of the samples, the study opened out the biology and population ecology of Xenophysogobio boulengeri provided the scientific bases to formulate how to use and protect fishery resources effectively in the upper reaches of the Yangtze River. The results were summarized as follows:1) There were annulus on otolith, scale, vertebra and opercular. The round lines of scale which had a few fragmentation, effected to judge reading the age accurately. The starting annual of vertebra was diffcult to judge and the round lines of opercular was unconspicuous.The otoliths of Xenophysogobio boulengeri were the main material to definite the age, scale were used as the supplementary material.2) The catch consisted of four age groups and individuals of age2to age3groups were dominant, occupying more than82.97%of total capture. The average body length was80.13±12.18mm, the preponderant groups were60-90mm,81.88percent in total. The average body weight was2.7-23.8g, the preponderant groups were4-10.0g,53.86percent in total.3) The relationship between body length and total length of Xenophysogobio boulengeri was able to be expressed as LT=1.1873LB+9.0741(R2=0.9443). The relationship between body length and weight was estimated as that, W=5×10-6L3.2841(r2=0.9641, n=933, F=7142.64, P＜0.01). The body length and otolith radius could be expressed as L=0.0008R2-0.1684R+42.504(r2=0.8365, n=399, F=399.20,.P＜0.01). The Von Bertalanffy equations of the species were calculated as that Lt=188.05(1-e-0.2487(t+0.2863)),Wt=147.21(1-e-0.2487(t+0.2863))3.2841. As follows the growth parameters were, L∞=188.05mm,W∞=147.21g, K=0.2487, t0=-0.2863. The inflexion point was4.49years, the body length in this point was130.79mm and body weigth in this point was44.67g.4) The diet was dominated by mosquito larvae, limnoperna fortunei, aquatic insect, leeches larvae, tubificidae, filamentousalgae, include organic matter of sediment. Most of invertebrate animals live in the bottom of the water or belong to the self-swimming species in middle level or lower level of the water. From above, it can be preliminary deduced that Xenophysogobio boulengeri mainly feed on bottom invertebrate animals.5) The sex ratio of the female to the male was1.03:1. The minimum body length and age of male individuals at first maturity of Xenophysogobio boulengeri were70mm.1.62years. The mean diameter of mature eggs of Xenophysogobio boulengeri were0.892±0.226mm, the mean relative fecundity of Xenophysogobio boulengeri was93.18±90.25(89.74-122.56) egg/g. The peak of spawning activity for Xenophysogobio boulengeri took place in June and September.6) Compared with the life history patterns of13kinds of fishes, the life history pattern of Xenophysogobio boulengeri was studied using the fuzzy set analysis method. The results showed that the life history pattern of Xenophysogobio boulengeri tended to be r selection.7) The total mortality coefficient (Z) of Xenophysogobio boulengeri in the upper reaches of the Yangtze River was estimated to be1.37. The natural mortality coefficient (M) was0.56, the fishing mortality coefficient (F) was0.81. The exploitation ratio (E) was0.59. According to length-based cohort analysis model, the average annual stock biomass of Xenophysogobio boulengeri2.785×103kg, with the number of0.450x106individuals respectively in the upper reaches of the Yangtze River8) The first capture age (tc) of Xenophysogobio boulengeri in the upper reaches of the Yangtze River was1.5. The first capture body length was65mm. Using the B-H model, it can be concluded that the exploitation rate was close to maximum level at present. To protect Xenophysogobio boulengeri resource, the first capture age should be reduced to3age, and their habitat, feeding and spawning sites should be protected and preserved.