| Rhinogobio ventralis(Sauvage et Dabry) is a kind of representative fish adapting to rapids, which is unique in the upper Yangtze River. In recent years, its resource decline year by year because of the habitat degradation and overfishing. From March 2013 to June 2014, wild resources of the fish were investigated in the Luzhou section of the upper of Yangtze River, and 414 samples were collected totally. with the conventional biological methods, a comprehensive research has carried on about its reproductive biology characteristics, including secondary sex characters, egg size and type of spawning, breeding season, the individual fecundity and gonad development, so as to clarify its reproductive biology characteristics. And then it can provide some references for the artificial propagation and scale breeding, as well as scientific guidance to its natural population resources protection and sustainable development. The main results were as follows:1. 414 individuals of 6 age groups were collected in all. The preponderant age is 3and it accounts for 43.00% of all. The body length ranges from 93mm-229 mm and the preponderant body length concentrates on 170mm-200 mm, accounting for 73.67%. The body weight ranged from 70.8g-178.6g, with the preponderant body weight concentrates on 90g-120 g, accounting for 48.79% of all.2. The external form between male and female individuals in the breeding season has not obvious difference. In the breeding season, the secondary sex characteristic of mature male is apparent, with keratin pearl stars appearing in pectoral fins. It can be used as reliable identification from male to female during sexual maturity.3. The 414 samples collected consists of 256 females and 158 males. The female to male ratio is 1.6203, close to 3:2. From March to May of 2014, 93 samples consists of 57 females and 36 males fish tail. The female to male ratio is 1.5833, close to 3:2 as well.4. The minimum age of both mature female and male individuals are 2. For the female the length is 154 mm, and weight is 57.2 g and maturity coefficient is 6.29%. Forthe male, the length is 157 mm, and weight is 60.5 g, and maturity coefficient is 1.02%.Determine the age of initial sexual maturity is 2.5. Choose ovary of Ⅳ period to count individual fecundity of females. The scope of the absolute fecundity is from 4051 grain to 32853 grain, with an average of 15348 grain. The relative fecundity ranges from 61.19 grain/g to 168.52 grain/g, with an average of 129.33 grain /g. Absolute fecundity(F, grain) and length(L, mm) or weight(W, g) respectively has power function or linear correlation, namely presents that the absolute fecundity increases with the increase of body length or weight. the respective optimal fitting relationship equation is F=2e-08L5.1842(R2=0.88253, n=33) and F=137.96 W-3014.8(R2= 0.8751, n=33).6. The mature egg is ball shape, beige or dark green. By measuring the eggs from ovary of Ⅳ, the eggs size ranges from 0.5 mm to 1.5 mm, with an average of 1.1063 mm, and the distribution is concentrated. The preponderant egg size is 1.1 mm to 1.2 mm,and 1.2 mm to 1.3 mm, accounting for 17.93% and 20.09% respectively. The annual statistics of maturity coefficient, gonad histological observations and the distribution of egg size all can be concluded that the fish is of one-time spawning type. The breeding season lasts from March to May every year, and the spawning peak appears in April.7. Every year in February, after the winter, the individual ovarian stage began to develop from Ⅱ to Ⅲ, with the mature coefficient ranging(1.38 ± 0.67) %. In early March, the most of individual ovaries develops into Ⅲ stage, and the earlier part even develops into Ⅳ, with the maturity coefficient rising to(3.78±2.18) %.In late March, a small amount of individuals have reached reproductive maturity, with the gonad developing into Ⅴ stage, and begin to lay eggs. The spawning peak appears in April,when most of the ovaries develop into Ⅳ stage and quickly enter the Ⅴ stage, with the maturity coefficient peak appears and rise to(11.77±3.36) %.Early in May, the females ovaries begin to degenerate to Ⅵ stage after laying eggs, and the maturity coefficient drops into a low level of(3.07±0.42) %. In June the ovary is in the transition from stageⅥ to Ⅱ, with the maturity coefficient drops into a lower level of(0.82±0.39) %. From July to next February, the ovaries are stuck in Ⅱ stage, with the maturity coefficient stays at the lowest level of from(0.63±0.27) % to(0.91 ±0.56) % in a reproductive cyclewithout any significant changes. The maturity coefficient of mature male individuals has a same trend as females and its maturity coefficient changes from(0.19±0.04) % to(1.23±0.26)% all the year round. |
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