Age, Growth And Gonadal Development Of Coilia Brachynathus In Swan Oxbow Of The Yangtse River

Swan Oxbow of the Yangtse River lies in Shishou city in Hubei province. It is the protection area of Baiji dolphin. C.brachynathus is a kind of small econimal fish in Swan oxbow of the Yangtse River .It eats fingerling and shrimp, simultanally it is regard as food of big predacity fish and cowfish. So it is very important in the food chain and is necessary to research it. Growth ring character, age , growth , propagation and gonadal development of C.brachynathus in Swan oxbow of the Yangtse River is researched in the paper. The main results are summarized as follows:1. The age of C.brachynathus can be identified by the character of annual rings on the squama, otolith and vertebrae; and agreement rate was 100% within one annual reading error. But the squama was the most reliable material to define age.2. The annual rings on the squama can be divided into widely and narrows-spaces type and shatter type.The annual ring was assigned to the last growth ring to the close zones adjacent to the outer wide zones. In the perspective light, otolith and vertebra were arranged alternately by wide opaque zones and narrow translucent zones.The annual ring was assigned to the outer border of opaque zones under perspective light.3. Acorrding to the comparison to the results of the age identifying by three materials , the result got from squama was better to judge age than those from otolith and vertebrae. So squama was selected to judge the age of C.brachynathus in Swan oxbow of the Yangtse River.4. Sexual ratio of propogation of C.brachynathus was as follows: ♀: ♂ = 1.19 : 1.5. The condition factors of female and male's of C.brachynathus changed with season. The influence of the condition factor was identical with eating and propagation. The propagation season were from April to September. Among this period, the condition factor was declining. But after propogation, the condition factor was rising with eating.6. The relationship between the body length and the body weight of C.brachynathus could be expressed...