长江口南支邻近水域碎波带仔稚鱼群落结构的差异及关联

Differences and Association of Larval and Juvenile Fish Community in Surf Zone of South Branch of Yangtze River and the Adjacent Waters

为探明长江口南支及邻近水域碎波带仔稚鱼群落结构的差异及相互联系,分别对长江口南支、杭州湾北岸与泗礁沙滩碎波带进行小型拖网(1 m×4 m,网目1 mm)取样调查,样品在实验室内进行种类鉴定及数量统计。结果显示:种类组成方面,3处水域分别采集到仔稚鱼11科40种、23科59种与28科46种,共有种7种;洄游性种类、河口性种类与海洋性种类分别为3者优势类群;单位捕捞努力量渔获量(CPUE)长江口南支最高,为41.45 ind./haul,泗礁沙滩最低,为5.72 ind./haul;长江口南支仔稚鱼各发育阶段个体分布相对均匀,杭州湾北岸以稚鱼个体为主,泗礁沙滩以后弯曲期仔鱼占优势;多样性指数杭州湾北岸最高,为2.19,泗礁沙滩最低,为1.75;长江口南支与杭州湾北岸群落相似度较高。数量变动方面,3处水域种类数均为8月最高,CPUE分别于8月、9月与5月达到峰值。生境功能方面,长江口南支兼具定居地、保育场与暂居地等功能,杭州湾北岸与泗礁沙滩则仅为保育场与暂居地;3处水域共有种中国花鲈(Lateolabrax maculatus)分别在不同时间段及不同发育阶段进入3处水域栖息保育,长江口南支及其邻近水域碎波带是其向岸及溯河洄游过程中的重要保育场与中转站。

In order to identify the difference and relationship of the larval and juvenile fish in surf zone in south branch of Yangtze River Estuary and the adjacent waters. Monthly field works were conducted in surf zone in south branch of Yangtze River Estuary（ SYE）, north Hangzhou Bay（NHB） （from Aug 2009 to Aug 2010） and Si Jiao Island （ S J1） （ from Aug 2010 to Aug 2011 ）. Fishes were collected by small trawls （ 1 m × 4 m, 1-mm mesh size） , each site sampling was repeated three times. Water temperature and salinity were also measured in the sampling periods. Samples were fixed in 5% formalin solutions in the fields and moved to lab for further analysis. All fish species were identified, measured and counted by stereomicroscope in lab. The result showed that there were 40 species（in 11 families） at SYE; 59 species（in 23 families） at NHB, and 46 species（in 28 families） at SJI, in which 7 species could be found at all above 3 sties. The dominant populations at SYE, NHB and SJI were migration fish, estuarine fish and marine fishes, respectively. The highest Catch Per Unit Effort （CPUE） at SYE, NHB and SJI were 203.62 ind. /haul, 112.80 ind. /haul and 53.67 ind. /haul, respectively. The predominant fish populations at the three sites were different one by one. post-flexion and juveniles fishes are predominant populations at Hangzhou Bay （NHB） and Si Jiao Island （SJI） , respectively; and the four development stages fishes equally distributed at Yangtze River Estuary （ SYE ）. The diversity index was highest at NHB （2. 19） and lowest at SJI （ 1.75 ）. The greatest fish diversities at the three sites all occurred in August, whereas the highest CPUE at the three sites existed in August, September and May, respectively. The only species that existed at all three sites, Lateolabrax maculates, reach the 3 water areas in different months and development stages. The three areas are all involved on Lateolabrax maculates migration routes to upriver waters.