We report the current status of Taimen (Hucho taimen) population in Wusuli River of China. The amount of catch per year was only 1 800 - 5 400 individuals ranging from 2-15 years old during 1998-2002. Of all the captured, individuals with sexual maturity were up to 30%-70% (female maturity at 5 years old and male 6 years old). Sex ratio varied greatly among different localities. Its breeding population mainly consisted of males aged 5-10 years and females aged 8-13 years’old, which spawned in May each year.Females breed once with about 4 000 - 23 000 eggs produced every 2-3 years. Taimen grows fast and average growth rate is about 10 cm per year prior to 10 years’s old, which corresponded with von Bertelanffy’s equation calculated as L t=246 41[1-e -0 0407(t-0 4625) ] and W t= 174 075 72 [1-e -0 0407(t-0 4622) ] 2 9537 , and the relationship between body length and weight was W=0 015018L u 2020 .
The Dace ( Leucisus brandti Dybowski) was a migration fish in Suifen river. The Dace can spawn at the water temperatures from 7℃ to 25℃. Changing of water temperature is the leading factor cause the spawning population to ovulate. However, high or low current water temperature had no obvious effectuation on ovulating behavior of Dace. The ovulation of the Dace often occurred in the evening or next morning after the water temperature rapidly in creased. The fish spawning often occurred as the water temperature decreased at first, after a period of steady low water temperature, then increased. A massive ovulating action began at the time. If the rising of water temperature happens only after a period of steady level without any decreasing of the water temperature, the change can not stimulate ovulation of the Daces. Usually, every large scale ovulate can sustain for 1 or 2 days. The peak time of ovulation often appears in 48 hours after the water temperature increases. Once the spawning population began to ovulate, their actions will be very intense, so that even catching action of human on them can not prevent the ovulation. The test of artificial induced ovulation showed that only when variation of water temperature were more than 10℃ ( increased degree+decreased degree), the Dace would ovulate. The Dace began to ovulate in 12～36 hours after the water temperature’s change. The efficient time was shorter and the ovulation rate was higher the variation of water temperature were greater. At the range from 8℃ to 24℃, as high or low water temperature had no effect on the efficient time stimulating ovulate, the Dace can not ovulate out of the temperature range.
