长江口中华绒螯蟹雌蟹的食性和摄食强度

2017年10月-2018年4月逐月采集长江口生殖洄游期中华绒螯蟹(Eriocheir sinensis)雌蟹,运用胃含物分析法分析雌蟹抱卵前后饵料组成、摄食强度以及营养级,探讨其在长江口抱卵繁殖期间的摄食规律。结果表明:雌蟹摄食率、食物饱满指数、平均胃饱满度系数等3项指标具有明显的月份变动,抱卵前雌蟹的摄食指标在10-11月份(秋季)最高,12-2月份(冬季)最低;抱卵后雌蟹的摄食指标在12-2月份(冬季)最低,3-4月份(春季)最高。洄游期的雌蟹抱卵前后饵料来源多样,包括水生植物、藻类、甲壳类、多毛类、鱼类、软体动物、棘皮动物、卵、颗粒碎屑等。其中,藻类、颗粒碎屑和甲壳类为抱卵前的主要饵料,出现频率分别为68.13%、54.76%和19.05%;藻类、颗粒碎屑和水生植物为抱卵后的主要饵料,出现频率分别为70.35%、73.91%和25.39%。雌蟹抱卵前后饵料组成存在显著差异(χ^2=21.57,P<0.05),对差异贡献最大的饵料组成是颗粒碎屑(χ^2=8.32)、甲壳类(χ^2=5.49)和水生植物(χ^2=4.02)。雌蟹抱卵前后的营养级分别为3.60和3.10,平均营养级为3.35,属于第三营养级动物。

Dietary and feeding intensity of female Eriocheir sinensis in the Yangtze River Estuary during migratory period

Eriocheir sinensis is an important economic aquatic animal, and the Yangtze River Estuary is an important reproductive migration place for Eriocheir sinensis. In recent years, Eriocheir sinensis resources have declined sharply due to overfishing, reclamation activities and habitat degradation in the Yangtze River Estuary. The protection of Eriocheir sinensis has attracted extensive attention. At present, enhancement and releasing, habitat restoration are important remedies for protecting the population. As the most important life stage in the life history of Eriocheir sinensis, spawning period is the key stage to determine its population resources. In this study, gastric content analysis was used to analyze the food composition, food difference of female crab before and after spawning in the Yangtze River Estuary. It can provide a reference for food types and food amount in artificial habitat restoration. It is of great significance for the protection and rational utilization of Eriocheir sinensis. It also supplements the basic biological knowledge of Eriocheir sinensis. The feeding composition, feeding intensity and trophic level were analyzed by the gastric contents of female crab collected from October 2017 to April 2018 in Chongming East Beach(121°58′~122°12′E、31°05′~31°22′N) of the Yangtze River Estuary by trawling.The results showed that the feeding rate, food fullness index and mean gastric fullness index of female crab had obvious monthly changes. The indexes before the spawning were the highest in October-November(autumn) and the lowest in December-February(winter). After spawning, the indicators were the lowest in December-February(winter) and the highest in March-April(spring). The female crabs in the migratory stage had various feed sources, including Bacillariophyta, Pyrrophyta, Cyanophyta, Chlorophyta, Crustacea, Polychaeta, fish, Mollusca, Echinodermata, eggs, aquatic plants, detritus, rubbish etc, belonging to omnivorous aquatic animals. Algae, detritus and Crustacea were the main diets of female crab before spawning, and frequency percentage was 68.13%, 54.76%, 19.05% respectively. Algae, detritus and aquatic plants were the main diets for female crabs after spawning, and frequency percentage was 70.35%, 73.91%, 25.39% respectively. There was a significant difference in food composition of female crab before and after spawning(χ^2=21.57, P<0.05). The food composition contributing most to the differences were detritus(χ^2=8.32), Crustacea(χ^2=5.49) and aquatic plants(χ^2=4.02). The trophic levels of female crabs before and after spawning were 3.60 and 3.10, and the average trophic level was 3.35. Thus, the crabs belonged to the third trophic level animals.The female crab before and after spawning did not stop eating in the migration stage, and their food sources were diverse. Therefore, during the reproductive period of female crab, sufficient food conditions can be provided to improve the reproductive performance of spawning population.