长江近口段沿岸刀鲚生物量的时间格局

为了解长江刀鲚Coilia nasus资源的变动状况,探讨沿岸水域对刀鲚资源的保育作用,于2002~2013年间用定制张网对长江靖江段沿岸鱼类作了每月2~3个样本的采集。分析结果显示,12a采集的369份样品中,刀鲚的出现频率达94.6%,分别占总渔获数量和重量的5.18%和5.46%。刀鲚平均CPUEN和CPUEW有16.7±19.9尾和106.6±109.5g,是沿岸鱼类群聚的优势种或次优势种。但其年资源量并不稳定,最高的2010年是最低2002年的5.4陪。平均体长123.6±37.0mm,平均体重仅7.5±8.2g。0+龄组占78.9%,1+龄组占20.7%,2+龄仅出现在4、5月份,且仅占当月个体数的3.0%,幼体是沿岸刀鲚群体的主要组成成分。从0+龄个体的月度体长分布看,当年孵化的幼鱼大多栖息在河岸水域,沿岸生境在维持刀鲚幼鱼资源上具有重要作用。分析显示,4月1日至6月30日的长江禁渔期虽可保护约42.6%的幼鱼个体,但从保护效果看,还因适当延长沿岸水域的禁渔时间。维护沿岸水域的生境完整性,也是保护长江刀鲚幼鱼资源的重要措施。

TEMPORAL PATTERN OF COILIA NASUS BIOMASS ALONG THE JINGJIANG SECTION OF THE YANGTZE RIVER OVER THE LAST DECADE

To clarify variation of Coilia nasus biomass and explore the conservational effects of the coastal waters on anchovy resources, investigations were carried out along the Jingjiang section of the Yangtze River 2 or 3 times per month from 2002 to 2013 using a stow net． The results showed that occurrence rate of C.nasus was 946% in 369 samples, accounting for 518 % (individual) and 546% (weight) of the total catch yield, respectively. The average abundance and biomass (CPUEN and CPUEW) of C.nasus was 167 ±199 ind. and 1066±1095 g. Being a dominant or subdominant species of the fish assemblage in 12 years, C.nasus was not stable in resource. The highest biomass in 2010 was 54 times higher than the lowest in 2002. The average body weight and body length was 75 g and 1236 mm, respectively. 1 315 specimens were determined as three age compositions: 789% of specimens as 0+ year age group, 207% as 1+ year age group and 05% as 2+ year age group. 2+ year age group only appeared in April and May, and accounted for 30% of the total individual. Thus, the larvae were major components of C.nasus population along the coast water. According to monthly length distribution of 0+ age group individual, larvae and juveniles began to appear in the coastal zone after hatching, coastal habitats supposedly play an important role in maintaining anchovy recruitment stock. Although the closed fishing season in the Yangtze River during April 1st to June 30th could protect the total 426% larvae and juveniles, properly longer fishing ban period in coastal region might acquire better protective effect. Maintaining habitat integrity of coastal waters is also an important measure to protect the resources of C.nasus larvae.