筏式和底播增养殖模式下魁蚶食物来源的比较研究

2014年5月和9月,运用稳定同位素技术和胃含物分析法,比较研究了不同增养殖模式下魁蚶(Anadara broughtonii)的饵料特征差异,以期探讨增养殖魁蚶可能的食物来源。结果显示,魁蚶的δ~(13)C值存在明显的季节差异,在5月,筏养区魁蚶的δ~(13)C值明显低于9月,底播区则表现出相反趋势。5月,两种增养殖模式下魁蚶的δ~(13)C和δ~(15)N值均无明显差异;9月,筏养区魁蚶的δ~(13)C、δ~(15)N值均显著高于底播区。以浮游植物为主的颗粒有机物是筏养区魁蚶的主要食物来源,其贡献率可达61.0%~62.9%,附着微藻是其重要的食物补充(37.2%~39.0%);而底栖微藻则是底播区魁蚶最主要的食物来源,其贡献率达到51.7%(5月)和72.5%(9月)。胃含物分析结果显示,魁蚶主要滤食圆筛藻属(Coscinodiscus)、曲舟藻属(Pleurosigma)、菱形藻属(Nitzschia)和舟形藻属(Navicula)种类。底播模式下魁蚶胃含物组成与底栖微藻群落的相似性系数可达85.30%(5月)和77.20%(9月),表明魁蚶对水体中的微藻具有一定的选择性,以浮游性较弱、且易于下沉的硅藻或底栖硅藻类为主。研究结果可为魁蚶筏式养殖和底播增殖的科学管理提供参考。

Comparative study of food sources of Anadara broughtonii in raft mariculture and bottom sowing proliferation

Marine coastal ecosystems are commonly used for the aquaculture of suspension-feeding bivalves, such as oyster, scallops and mussels. The food sources for these bivalves often depend on particulate organic matter and benthic microalgae. Recent studies have suggested that attached microalgae and bacteria also become important food sources for suspension-feeding bivalves. Knowledge of the dietary regime of bivalves is crucial for under-standing the coastal food web and cultured bivalve management. The ark shell,Anadara broughtonii, is one of the most important commercial bivalve species in China. They are usually cultured both in raft mariculture and bottom sowing proliferation. However, information on the food sources for culturedA.broughtoniiis still limited. Based on stable isotope (δ13C andδ15N) and stomach content analysis, this study analyzed the dietary regime ofA. broughtonii under two different proliferation and culturing modes in May and September 2014, aimed to approach the potential food sources ofA.broughtonii in this area. Results showed that there was a clear seasonal variation inδ13C values ofA. broughtonii. Theδ13C value in the raft mariculture area (RMA) in May was significantly lower than that in September, but there was an opposite trend in the bottom sowing proliferation area (BSPA). There were no significant differences inδ13C andδ15N values ofA. broughtonii under two proliferation and culturing modes in May, but theδ13C andδ15N ofA. broughtonii in the RMA were clearly higher than those in the BSPA in September. The POMs, mainly including phytoplankton, were the greatest sources of food in the RMA, with a contribution rate of 61.0%-62.9%, followed by attached microalgae (37.2%–39.0%). Comparatively, benthic mi-croalgae was the most important food source in the BSPA, with a contribution rate of 51.7% in May and 72.5% in September. Stomach content analysis showed thatA. broughtonii filter-fed mostly on Coscinodiscus,Pleurosigma, Nitzschia andNavicula. The similarity analysis results indicated the proportional similarity (PS) values between stomach content in the BSPA and the benthic microalgae community were 85.30% in May and 77.20% in Sep-tember, which may suggest thatA. broughtoniishow a certain selectivity for diatoms of weaker planktonic habit, which sink easily, and for benthic diatoms. Overall, the results can improve our understanding of the biology ofA. broughtonii, and provide theoretical evidence for scientific aquaculture management of suspension-feeding bi-valves under these two proliferation and culturing modes.