象山港春、夏季仔稚鱼种类组成结构特征

为研究象山港仔稚鱼的时空分布特征及其与环境因子的相关关系,在象山港港湾内设置14个站,于2015年4月3日~6月10日期间按周采样,共调查10个航次(Ⅰ~Ⅹ),用方形网(网口为1 m×2 m,网目1.0 mm)采集仔稚鱼,同时采集温度、盐度和浮游动物等数据。调查期间采集仔稚鱼180 254 ind共45种,隶属25科39属,主要优势种为斑鰶(Konosirus punctatus)、矛尾鰕虎鱼(Chaeturichthys stigmatias)、鮻(Chelon haematocheilus)、斑尾刺鰕虎鱼(Acanthogobius ommaturus)、普氏缰鰕虎鱼(Amoya pflaumi)、拟矛尾鰕虎鱼(Parachaeturichthys polynema)、黑棘鲷(Acanthopagrus schlegelii)、舌鰕虎鱼(Glossogobius giuris)等。仔稚鱼密度呈先升后降的趋势,第Ⅲ航次密度最高(平均密度为587.9 ind·100 m-3),第Ⅷ航次最低(8.2 ind·100m-3)。前弯曲期仔鱼最多,占63.6%,弯曲期仔鱼占26.4%。基于层级聚类(Bray-Curtis相似性指数,Ward法聚类)分析表明,可将10航次仔稚鱼分为4个类型,各类型间存在明显差异:类型1(Ⅰ和Ⅱ航次)主要为矛尾鰕虎鱼和斑尾刺鰕虎鱼,类型2(Ⅲ~Ⅵ航次)为斑鰶、鮻、矛尾鰕虎鱼和黑棘鲷,类型3(Ⅶ和Ⅷ航次)为斑鰶、日本鳀(Engraulis japonicus)、拟矛尾鰕虎鱼,类型4(Ⅸ和Ⅹ航次)为普氏缰鰕虎鱼、拟矛尾鰕虎鱼、美肩鳃鳚(Omobranchus elegans)。Spearman相关分析表明,仔稚鱼分布与温度极显著相关(P0.01),与浮游动物密度呈显著相关(P0.05),与盐度无明显相关关系(P0.05)。

Species composition of larval and juvenile fish in the Xiangshan Bay in spring and summer

The larvae and juvenile fish assemblage was investigated in Xiangshan Bay to analyze their composition and distribution as well as the relationships between the fish larva amount and the environmental factors.Fourteen sampling stations were established,and larval and juvenile fish were weekly collected by the frame trawls (1 m × 2 m,1.0 mm mesh size) from April 3 to June 10 in 2015.The water temperature,salinity and zooplankton at each sampling site were also measured at each sampling time.In total,180 254 larval and juvenile fishes were collected belonging to 25 families and 45 species.The dominant fish species were Konosirus punctatus (25.8％),Chaeturichthys stigmatias (23.9％),Chelon haematocheilus (19.2％),Acanthogobius ommaturus (9.9％),Amoya pflaumi (8.5％),Parachaeturichthys polynema (4.5％),Acanthopagrus schlegelii (2.5％) and Glossogobius giuris (1.2％).The density of larval and juvenile fishes varied significantly among cruises(P ＜ 0.05).The highest mean density of larval and juvenile fishes was recorded in the third cruise (587.9 ind · 100 m-3),while the lowest mean density (8.2ind · 100 m-3) occurred in the eighth cruise.The number of species increased gradually from the first cruise to the last one.Fish larvae in preflexion stage accounted for 63.6％ of the total catch.The flexion stage of larvae made 26.4％ contribution to the total catch.There were temporal variation in the dominant species in Xiangshan Bay.According to the Bray-Curtis similarity measure on the relative abundance of each taxonomic type,four principal types were identified,including Type 1 (cruises Ⅰ and Ⅱ),Type 2 (cruises Ⅲ to Ⅵ),Type 3 (cruises Ⅶ and Ⅷ) and Type 4 (cruises Ⅸ and Ⅹ).Variations of some larval and juvenile fish density,such as Konosirus punctatus,Chelon haematocheilus,Chaeturichthys stigmatias,Acanthogobius ommaturus,Amoya pflaumi and Parachaeturichthys polynema were thought to account for the type variation in the larval and juvenile fish assemblage structure.The environmental factors can have important implications for the distribution,growth,and survival of larval and juvenile fish.Furthermore,we measured environmental factors and determined the responses of the larval and juvenile fish communities to the factors,including the temperature,the salinity and the zooplankton density.The results of the Spearman Correlation between the amount of fish and the simultaneous environmental factors showed that the fish larva amount had the distinct correlation with water temperature and zooplankton density,but the salinity had no remarkable relationship with the fish larva density.Zooplankton is the vital food source for most larval and juvenile fish specie.Variations in zooplankton distribution and quantity can directly or indirectly affect the larval and juvenile fish.High quantities of zooplankton provide the sufficient food to support the larval and juvenile fish populations and therefore provide a valuable condition for fish reproduction and growth.