长江口鳗苗网兼捕鱼类物种多样性及其群聚结构

为探明长江口鳗苗网兼捕鱼类的物种多样性及其群聚结构,文章分析了2017—2019年鳗苗汛期用定置张网采集的11870网次鱼类样本。结果显示,样本中包含兼捕鱼类114388尾,经鉴定有54种,隶属13目27科46属。其中,鲈形目占总种数的40.74%,海洋性、肉食性、底层和小型鱼类分别占总种数的44.44%、74.07%、70.37%和48.15%。拉氏狼牙虾虎鱼(Odontamblyopus lacepedii)为第一优势种,数量占比达77.07%;焦氏舌鳎(Cynoglossus joyneri)、刀鲚(Coilia nasus)和斑鰶(Konosirus punctatus)也是个别年份的优势种。根据各月份间鱼类的群聚差异可将3月和4月、1月和2月各组合成1个组,两者的主要特征种分别有5种和6种,主要分歧种有10种。兼捕鱼类的平均体长仅(73.77±38) mm,早期资源占总样本数的96.65%,许多是当地经济鱼类的幼体。样本中有鳗苗16470尾, 3年平均的兼捕损伤率7.58,高于6年前的损伤率,鳗苗捕捞对其他鱼类幼体的损伤应引起重视。

SPECIES DIVERSITY AND ASSEMBLAGE STRUCTURE OF FISHES BY-CATCH IN ELVER NETS IN YANGTZE RIVER ESTUARY

The Yangtze River estuary is the major production regions of larval eels in China, and it is also the most important place for feeding and nursing place for fishes. In order to clarify the species diversity and damage rate of fishes by-catch in elver nets in the Yangtze Estuary, this article analyzed 11870 fish samples collected by elver nets during the eel fry flood season from 2017 to 2019. The results showed that 43 samples contained 114388 fishes by-catch in elver nets, 54 species were identified, belonging to 13 orders, 27 families and 46 genera. Among them, Perciformes accounted for 40.74% of the total species, and marine, carnivorous, demersal and small fishes accounted for 44.44%, 74.07%, 70.37% and 48.15%, respectively. Odontamblyopus lacepedii was the first dominant species, accounting for 77.07%; Cynoglossus joyneri, Coilia nasus and Konosirus punctatus were also the dominant species in individual years. According to the difference of fish assemblage, March and April, January and February can each be combined into one group. The major characteristic species of two groups were 5 and 6, and the major divergent species were 10. The average body length was (73.77±38) mm of 54 species. Fish resources of the early life history stages account for 96.65% of the total samples, many of which are larvae of local economic fishes. There were 16470 eel elvers in the sample, and the average damage rate of fishes by-catch in 3 years was 7.58, which was higher than 6 years ago. Attention should be paid to the damage caused by fishing eel elvers to other fishes’ larvae.