海州湾秋季小眼绿鳍鱼的摄食策略及食物选择性

基于2011年及2013—2015年秋季在海州湾海域进行底拖网调查数据,通过分析733尾小眼绿鳍鱼(Chelidonichthys spinosus)的胃含物样品,对其食物组成、摄食强度、摄食策略以及食物选择性等摄食生态特征进行初步研究。结果表明,小眼绿鳍鱼摄食饵料生物共有80余种,其中优势饵料种类为细螯虾(Leptochela gracilis)、戴氏赤虾(Metapenaeopsis dalei)、疣背宽额虾(Latreutes planirostris)、双斑蟳(Charybdis bimaculata)、细条天竺鲷(Apogon lineatus)等。聚类分析结果显示,小眼绿鳍鱼的食物组成无明显体长变化。不同体长组小眼绿鳍鱼的空胃率差异不显著(P0.05),平均胃饱满指数差异显著(P0.05)。广义加性模型(GAM)分析表明,底层盐度、底层水温和纬度对小眼绿鳍鱼的摄食强度有显著影响(P0.05),而体长、经度和水深的影响则不显著(P0.05)。摄食策略分析表明,小眼绿鳍鱼是以虾类和鱼类为主要饵料类群的广食性鱼类。通过计算食物选择性指数发现,小眼绿鳍鱼喜食饵料与实际摄食的主要饵料种类存在一定差异,表明其摄食既具有较强的主动选择性,同时又受到海州湾饵料丰度和可获得性等因素的影响。

Feeding strategy and prey selectivity of Chelidonichthys spinosus during autumn in Haizhou Bay

With the decrease in traditional economic fish resources, Chelidonichthys spinosus has become one of the dominant fish species in the Haizhou Bay ecosystem, playing an important ecological role in the food web. Chelidonichthys spinosus is a benthic fish species widely distributed in the China seas and Japan Sea, and in the waters around the Korean Peninsula. Using the samples collected from the bottom trawl survey in the Haizhou Bay during the autumn of 2011 and 2013-2015, 733 C. spinosus stomach samples were analyzed to study their feeding ecology, including diet composition, feeding intensity, feeding strategy, and prey selectivity. The results showed that the prey items of C. spinosus included more than 80 species, and shrimp and fish were the predominant prey taxa, with the index of relative importance of 97.14% and 1.15%, respectively. Leptochela gracilis, Metapenaeopsis dalei, Latreutes planirostris, Charybdis bimaculata, and Apogon lineatus were the most important prey species. The results of the cluster analysis showed that the diet composition did not change significantly with the increase in body length. The average similarity coefficient of the food composition of C. spinosus was 86.74% among different size classes. This might be because the samples were collected in autumn. The samples reached or were close to adulthood, with their mouth, teeth, gill rake, and other feeding organs developed perfectly. The feeding intensity was described by the percent of empty stomachs and the mean stomach fullness index. The percent of empty stomachs of C. spinosus did not vary significantly among different size classes (P> 0.05), but the mean stomach fullness index varied during the growth period (P<0.05). Overall, the feeding intensity of small-sized C. spinosus was higher than that of large individuals. This is because the growth rate of small-sized C. spinosus is faster than adalts; they require more energy from prey. The feeding of fish is generally affected by several variables, including the development status of fish, the type and abundance of prey species, environmental conditions, and other factors. In this study, the generalized additive model (GAM) revealed that the feeding intensity of C. spinosus was affected significantly by salinity, water temperature, and latitude (P< 0.05), whereas, the effects of body length, longitude, and water depth were not significant (P>0.05). It will help analyze the factors that affect feeding habits of fish, understand the feeding status of fish, and examine the current situation and development of fish and their prey species, in order to make reasonable resource development and utilization decisions. The feeding strategy analysis further revealed that C. spinosus is a generalist predator and mainly feeds on shrimp and fish. The general feeding habit is an adaptive feeding strategy for fish that facilitates the adaptation of fish to variable environmental conditions, regulating the relationships with competitors. By calculating the prey selectivity index, it was found that there was a difference in the composition of favorite prey items and actual feeding prey items. The feeding ecology of C. spinosus is affected not only by the abundance and availability of prey, but also by strong active selectivity. These results will provide basic data to further understand the trophic dynamics in the Haizhou Bay ecosystem. It can also provide scientific reference for the protection and rational utilization of C. spinosus resources in Haizhou Bay.