红海湾远海梭子蟹Portunus pelagicus的食物组成及营养位置分析

利用稳定同位素技术；分析了2015年5月在红海湾海域采集的远海梭子蟹Portunus pelagicus及其潜在食物的碳（δ13C）和氮（δ15N）稳定同位素比值；通过稳定同位素混合模型（SIAR）；估算不同食物对远海梭子蟹食性的相对贡献。结果表明:远海梭子蟹的δ13C值在-18.1‰~-14.1‰之间；δ15N值的范围为9.8‰~13.8‰；平均值分别为-16.9‰±1.3‰和12.1‰±2.3‰。δ13C和δ15N值的变化范围均较大；表明远海梭子蟹食物来源广泛、多样。远海梭子蟹的食物主要由双壳贝类、螺类、鱼类、头足类、虾类、蟹类和藻类组成。SIAR模型计算结果显示:藻类为远海梭子蟹的主要食物；其平均贡献为32.5%；双壳贝类的相对食性贡献为21.9%；虾类、螺类、鱼类和蟹类的平均贡献差异较小；分别为9.7%、9.7%、9.6%和9.3%；头足类的贡献最低；仅为7.3%。此外；根据δ15N值及营养位置的计算公式得出:远海梭子蟹在红海湾海域位于2.91±0.68营养级。远海梭子蟹的7类潜在食物中；藻类的营养位置最低；为1.21±0.58；其次为双壳贝类；为2.00±0.25；蟹类、螺类、虾类和鱼类的营养位置分别为2.85±0.33、2.87±0.26、3.01±0.16和3.08±0.18；头足类的最高；为3.41±0.17。

Dietary composition and trophic position of blue swimmer crab (Portunus pelagicus) in Honghai Bay

Carbon and nitrogen stable isotope analyses were employed to explore the dietary composition and trophic position of P. pelagicus in Honghai Bay based on samples collected in May 2015. The results showed that, the average δ13C and δ15N values of the P. pelagicus were -16.9‰±1.3‰ and 12.1‰±2.3‰, in a range of -18.1‰ to -14.1‰ and 9.8‰ to 13.8‰, respectively, indicated that P. pelagicus feed on numerous prey species. Potential food sources of P. pelagicus were bivalves, snails, fishes, cephalopods, shrimps, crabs and algaes. Algaes were the most important prey of P. pelagicus by averagely contributing 32.5% to the diet, followed by bivalves (21.9%), shrimps (9.7%), snails (9.7%), fishes (9.6%), crabs (9.3%) and cephalopods (7.3%). The average trophic position of P. pelagicus was 2.91±0.68, and algaes, bivalves, crabs, snails, shrimps, fishes as well as cephalopods' trophic positon were 1.21±0.58, 2.00±0.25, 2.85±0.33, 2.87±0.26, 3.01±0.16, 3.08±0.18 and 3.41±0.17 respectively.