论文部分内容阅读
分别在长江南支南门至新河水域、北港水域和圆沙至九段沙水域设置调查断面,对三峡蓄水后(2003~2011年)长江口凤鲚汛期生物学特征、渔汛特征及捕捞量进行了持续调查,并将之与蓄水前(1997~2002年)调查数据进行了对比研究。调查期内凤鲚汛期绝对怀卵量变幅为3 404~26 850粒,平均为11 554粒;相对怀卵量变幅为347~1 582粒/g,平均为783粒/g;卵径变幅为0.53~1.06mm,平均为0.78mm。凤鲚全长变幅为139~155mm,平均为146mm;体长变幅为123~137mm,平均为129mm;体重变幅为12.0~15.8g,平均为13.6g;丰满度系数变幅为0.387~0.466,平均为0.442。2003~2011年凤鲚全长小于140mm的个体所占比例均值为36.91%,140~180mm的个体占比为57.06%;体重小于12g的个体占比为39.57%,12~20g的个体占比为45.34%。长江口凤鲚渔汛出现时水温通常介于17℃~20℃,5月中下旬至6月中旬为旺汛期,各年5月捕捞量占比变幅为30.59%~83.76%,平均为61.17%。调查期间长江口凤鲚汛期捕捞船数量变幅为63~278艘,平均为141艘;单船全汛捕捞量变幅为367.9~5 023.5kg,平均为2 441.2kg;汛期总捕捞量变幅为23.2~1 256.9t,平均为422.3t。三峡蓄水后长江口凤鲚渔获规格和捕捞量均出现了不同程度的下降,与历史记录相比,其资源几近枯竭,捕捞价值基本丧失。建议立即对凤鲚实施禁捕,并尽快建立繁殖场和越冬场保护区。
The survey sections were set up respectively in the area from Nanmen branch to Xinhe waters, Beigang waters and Yushansha waters from Nanmenan to Yangtze River, and the biological characteristics, the characteristics of flood season and the amount of catch A continuous survey was conducted and compared with the survey data before the impoundment (1997-2002). During the investigation period, the absolute fecundity of fecundity during the flood season was between 3 404 and 26 850, with an average of 11 554; the relative fecundity ranged from 347 to 1 582 grains / g with an average of 783 grains / g; 0.53 ~ 1.06mm, an average of 0.78mm. The average length of FENG is 139 ~ 155mm, the average is 146mm; The body length is 123 ~ 137mm, the average is 129mm; The body weight is 12.0 ~ 15.8g, the average is 13.6g; The fullness coefficient is 0.387 ~ 0.466, with an average of 0.442. The mean percentage of individuals with less than 140mm in total length from 2003 to 2011 was 36.91%, while the percentage of individuals with 140 ~ 180mm was 57.06%; the percentage of individuals with body weight less than 12g was 39.57% 20g of individuals accounted for 45.34%. When the Yangtze River estuary fishing season appears, the water temperature usually ranges from 17 ℃ to 20 ℃. From mid-late to mid-June, the fishing season flood season fluctuates from 30.59% to 83.76% with an average of 61.17% . During the survey period, the number of fishing vessels fluctuated from 63 to 278 in the flood season of the Yangtze River estuary, with an average of 141 vessels. The single-ship catchment amplitude ranged from 367.9 to 5203.5 kg, with an average of 2 441.2 kg. The total catch in the flood season varied by 23.2 ~ 1 256.9t, with an average of 422.3t. Compared with the historical record, the catch and catches of Fungi in the Changjiang Estuary after the Three Gorges impoundment all decreased to some extent. Compared with the historical record, the resources of the Fungi nearly dwindled and the fishing value was basically lost. It is recommended that a ban on phoenix bears be promptly implemented and that breeding grounds and wintering grounds be established as soon as possible.