渤海小黄鱼摄食习性

根据2009年8月至2011年5月4个航次渤海底拖网调查所获得的样品,采用胃含物分析法、K-W检验和聚类分析等方法,对38～218 mm体长范围小黄鱼(Larimichthys polyactis)的摄食习性及其随体长、季节的变化进行了研究,并探讨了小黄鱼摄食随海域和年际的时空变化。结果表明:渤海小黄鱼摄食的饵料有40余种,主要以鱼类、虾类和浮游动物为食,优势饵料种类为六丝钝尾虾虎鱼(Amblychaeturichthys heaema)、日本鼓虾(Alpheus japonicus)、太平洋磷虾(Euphausia pacifia)、长额刺糠虾(Acanthomysis longirostris)和中华哲水蚤(Calanus sinicus)。渤海小黄鱼在春夏秋这三个季节中,春季的摄食强度最低,夏季和秋季的摄食强度都较高,不同的是夏季摄食率更高,而秋季的摄食量更高。随着体长的增大,渤海小黄鱼的摄食策略发生了相应的变化。从摄食强度分析,在体长较小时,胃饱满指数低,小黄鱼通过高摄食率来提高摄食强度;随着体长的增加,通过高胃饱满指数来提高摄食强度。从摄食的饵料个体分析,小黄鱼采取了随着体长增加摄食饵料个数减少,饵料个体增大的摄食策略。从摄食的饵料组成分析,小黄鱼随着体长增加发生了显著的食性转换现象:体长小于60 mm属浮游动物食性;体长60～99 mm时,属混合动物食性;体长100～119 mm时,属虾食性;体长超过120 mm,包括了虾/鱼食性和鱼食性。小黄鱼摄食的时空变化与环境中优势饵料生物的数量波动密切相关。

Feeding habits of small yellow croaker Larimichthys polyactis in the Bohai Sea

Based on four bottom trawl surveys conducted in the Bohai Sea from August 2009 to May 2011, 2979 stomach samples of small yellow croaker Larimichthys polyactis with body lengths of 38-218 mm were collected. Stomach contents analysis, the Kruskal-Wallis test and the cluster analysis were used to study their feeding habits and ontogenetic, temporal and spatial variations. The results indicated that small yellow croaker fed on more than 40 prey species. Amblychaeturichthys hexanema, Alpheus japonicus, Euphausia pacifica, Acanthomysis longirostris and Calanus sinicus were the dominant prey item. With the increase of fish size, there is a corresponding change in the feeding strategy of the Bohai Sea small yellow croaker. According to the feeding intensity, as indicated by the percentage of empty stomachs (PES) and mean stomach fullness index (MSFI), MSFI was low at the smaller fish size, resulting in the small yellow croaker increasing the feeding intensity as observed by the low PES. With the increase of fish size, the feeding intensity was enhanced by increasing MSFI. According to the prey items, the mean number of prey per fish decreased significantly with the increased fish size, while the mean weight of prey items per fish increased. According to diet compositions, the feeding habits of small yellow croaker had significant ontogenetic variations. Small yellow croaker less than 60 mm in body length mainly fed on the zooplanktivores copepoda, euphausiacea and mysidacea. At 60-99 mm long, it mainly fed on demersal shrimps and copepoda. The frequency of demersal shrimps in the food increased gradually with the increasing fish size, whereas the frequency of copepod decreased. Thus, fish with a 60-99 mm body length belonged to the generalist predators group. At 100-119 mm long, it belonged to shrimp predators group, mainly feeding on demersal shrimps at a frequency of more than 60%, and fish. It still mainly fed on demersal shrimps and fish at greater than 120 mm in body length with the frequency of fish in the food increasing gradually, and ultimately more than the frequency of demersal shrimps (beyond 60%). Thus, fish greater than 120 mm long included shrimp/fish predators and piscivores. The feeding intensity varied significantly across seasons. The feeding intensity of spring was lowest and the feeding intensity of summer and autumn were higher. The difference in the feeding rate was higher (PES was lower) in summer and the feeding amount (MSFI) was higher in autumn. Seasonal variations were also discovered in diet composition. Acanthomysis longirostris and Crangon affinis were the dominant preys in spring, Amblychaeturichthys hexanema and Alpheus japonicus were the dominant preys in summer, whereas Alpheus japonicus was the dominant prey in autumn. By analyzing historical data, we found that the feeding habits of small yellow croaker in the Bohai Sea were closely related to the composition and abundance of dominant prey organisms. The temporal and spatial variations in the feeding habits of small yellow croaker is closely related to the fluctuation of dominant prey species in the environment.