【摘要】 为探究禁捕后长江口棘头梅童鱼(Collichthys lucidus)的食物组成,本研究采用胃含物分析法对2024年春季在长江口水域采集的棘头梅童鱼样本进行分析。结果发现,长江口棘头梅童鱼的饵料生物共计11类29种,甲壳类(虾蟹类)是其主要的食物来源,相对重要性指数百分比(IRI%)达96.32%(虾类32.78%、蟹类63.54%)。相似性检验结果显示,幼鱼与成鱼在饵料选择上表现出显著的生态位分化(P<0.01),其中,幼鱼主要以狭额绒螯蟹(Eriocheir leptognathus, IRI%=38.55%)和长额刺糠虾(Acanthomysis longirostris, IRI%=23.12%)为主要饵料,成鱼则偏好摄食中华绒螯蟹大眼幼体(Eriocheir sinensis megalopa, IRI%=54.76%)和安氏白虾(Exopalaemon annandalei, IRI%=27.67%)。长江口不同区域间棘头梅童鱼食物组成也存在显著差异(P<0.05),淡水区以安氏白虾(IRI%=73.65%)为绝对优势饵料生物,咸淡水区则以中华绒螯蟹大眼幼体(IRI%=54.17%)和安氏白虾(IRI%=22.86%)为主。与禁捕前相比,禁捕后棘头梅童鱼食物组成发生显著改变,优势种更替率为66.6%,这一改变或与长江禁捕效应带来长江口饵料生物和鱼类生存空间的竞争压力有关。更多还原

【Abstract】 This study investigated the dietary composition of Collichthys lucidus in the Yangtze River Estuary during the post-fishing moratorium period through stomach content analysis of specimens collected in spring 2024. Statistical analyses revealed that the diet comprised 29 prey species from 11 taxonomic groups, with crustaceans(shrimps and crabs) dominating as the primary food source, accounting for 96.32% of the index of relative importance(IRI%)(shrimps: 32.78%; crabs: 63.54%). Significant ontogenetic niche differentiation in prey selection was observed between juveniles and adults(P<0.01). Juvenile fish primarily consumed Eriocheir leptognathus(IRI%=38.55%) and the Acanthomysis longirostris(IRI%=23.12%), while adults showed preference for megalopa larvae of Eriocheir sinensis(IRI%=54.76%) and Exopalaemon annandalei(IRI%=27.67%). These ontogenetic dietary shifts can be explained by optimal foraging theory, where fish optimize energy acquisition by balancing energy gain against expenditure. As body size increases, the feeding strategy shifts toward larger prey items to meet higher energy demands and improve feeding efficiency. Spatial analysis demonstrated significant regional variations in dietary composition(P<0.05). The freshwater zone was dominated by Exopalaemon annandalei(IRI%=73.65%), while the brackish water region showed preference for Eriocheir sinensis megalopa(IRI%=54.17%) and Exopalaemon annandalei(IRI%=22.86%). The observed increase in cannibalism frequency from 0.4%(pre-moratorium) to 2.5%(post-moratorium) suggests intensified intraspecific competition, likely due to population density increases and food scarcity, potentially forcing less competitive individuals to migrate from brackish to freshwater zones for foraging. Comparative analysis revealed significant post-moratorium dietary changes, with a 66.6% turnover rate among dominant prey species, possibly reflecting ecological restructuring due to altered competitive pressures in the estuarine ecosystem. Notably, our results indicate no feeding preference for Eriocheir sinensis megalopa in C. lucidus, but rather reveal density-dependent feeding suppression. This phenomenon may result from either collective defense mechanisms of megalopa larvae or alternative prey preferences in C. lucidus, warranting further investigation. These findings provide crucial baseline data for understanding trophic dynamics in the Yangtze Estuary ecosystem and evaluating the ecological effects of fishing moratorium policies, while highlighting the need for continued monitoring of predator-prey interactions under changing environmental conditions.更多还原