长江天鹅洲故道鲢、鳙、草鱼和青鱼种群特征与数量变动的初步研究

PRELIMINARY STUDY ON THE POPULATION GROWTH AND DYNAMICS OF SILVER CARP,BIGHEAD, GRASS CARP AND BLACK CARP IN SWAN OXBOW OF CHANGJIANG RIVER

本文报道兴建中的长江天鹅洲“四大家鱼”天然种质资源库中鲢、鳙、草鱼与青鱼的生长、死亡特性和资源数量变动规律。对这4种鱼生长参数值的比较分析表明,天鹅洲故道鲢、鳙、草鱼、青鱼基本维持了长江天然群体的优良生长特性。1991年度,故道渔获量为71.8万公斤,其中“四大家鱼”产量8.8万公斤。鲢、鳙、草鱼、青鱼的死亡率分别为0.66、0.77、0.86、0.86。”四大家鱼”的年资源补充量为16.7万尾,平均资源重量为7.28万公斤。目前该故道渔业所存在的主要问题是过度捕捞。为了发挥种质资源库的预期效应,建议将“四大家鱼”的开捕年龄定为3龄,严禁捕捞其当年幼鱼,捕捞强度控制在0.3～0.5间,以期故道鲢、鳙、草鱼、青鱼的持续产量保持在30万公斤左右。

This paper reports the characteristics of growth, mortality and dyna-mics of silver carp(Hypophthalmichthys molitrix), bighead (Aristichthys nobilis), grass carp(Ctenopharyngodon idellus) and black carp (Mylopharyngodon piceus) in Swan Oxbow ofChangjiang River, where the construction of genetic conservation in situ for Chinesecarps has been started. In 1991, the total fish yield of Swan Oxbow was 7.18×10~5kg,in which silver carp, bighead, grass carp and black carp accounted for 8.8×10~4kg.From Dec. 1990 to Dec. 1991, 496 specimens of the four species were collected andanalysed. The major results are as follows: (1) It was proved that there were nosignificant differences in the growth characters of these four species between SwanOxbow and Changjiang River. (2) The estimated total mortalities of the silver carp,bighead, grass carp and black carp were 0.66,0.71, 0.86 and 0.86 respectively. (3) Theestimated annually recruitment of the four Chinese carps was about 2.6×10~5 fish, theaverage abundance was 1.6×10~5 fish, and the average abundance weight was about7.28×10~4 kg. (4) Over-fishing is the main problem of fishery management in SwanOxbow: catching of one-year-old fish of the four Chinese carps must be prohibited;their ages of first capture are suggested to be three, and their fishing mortality shouldbe controlled at 0.3-0.5; in these cases, their abundance in weight could be maintainedat 3.0×10~5kg.