STUDIES ON THE BIOLOGY OF SINILABEO DECORUS TUNGTING

This paper deals with some results of a biological survey on Sinilabeo decorus tungting. This species is an important economical fish of river Yuanjiang in Hunan Province and is a favourite of the local people.The feeding habit, age and growth and the natural propagation of S. decorus have been studied. The main results of these studies are as follows:This fish feeds mainly on benthic plankton, especially diatoms and has a strong appetite during the period of spring to autumn.The age of the fish was determined according to the number of annual rings formed by the "U" type cireuli on the scale. The "U" type circuli are formed between spring and autumn, which denote the growing period of this fish. Among the fish we examined, there are 2 to 6 years old individuals. The largest one we weighed is 3400 g., which is of 6 years old. The average body length and body weight of 1 to 3 years old fish are calculated respectively. The interrelationship between body length (L) and body weight (W) may be expressed by the following equation: W=0.02180L3.2176.The age of mature females of S. decorus which grow in the river Yuanjiang is mostly of 3 years old, the male spawners ripen one year earlier than the females. The male and female sex ratio of the fish examined is about 1.14: 1. The oocytes develop from phase Ⅲ to phase Ⅳ nonsynchronously. The spawning season of the fish in the river is from the middle of April to the end of May.