基于稳定碳氮同位素的莱州湾4种鳀鲱科鱼类营养级研究

Determination of the trophic levels of four fish species in Engraulidae and Clupeidae in Laizhou Bay based on stable carbon and nitrogen isotopes

为研究莱州湾4种鳀鲱科鱼类营养级, 根据2011年夏季（8月）和秋季（10月）莱州湾底拖网调查取得的样品, 测定了130 尾样品的稳定碳氮同位素值。结果表明所有样品的δ13C值范围为-21.97‰-11.67‰, δ15N值范围为8.54‰-15.95‰。单因素方差分析结果表明, 各种类间稳定碳氮同位素比值差异显著（P〈0.05）。青鳞小沙丁鱼（Sardinella zunasi）和斑鰶（Konosirus punctatus）的δ15N值随叉长变化而有显著变化（P〈0.05）, 但黄鲫（Setipinna taty）和赤鼻棱鳀（Thrissa kammalensis）的δ15N值随叉长的变化不明显（P〉0.05）。青鳞小沙丁鱼营养级范围为2.80-4.88, 平均营养级为3.52±0.46; 斑鰶营养级范围为2.71-4.29, 平均营养级为3.34±0.33; 赤鼻棱鳀的营养级范围为3.38-4.42, 平均营养级为3.97±0.28; 黄鲫的营养级范围为3.28-4.13, 平均营养级为3.76±0.23。根据稳定碳氮同位素结果, 可以得出以下结论： （1）斑鰶的稳定碳同位素值范围较宽（-20.92--11.67）, 几乎涵盖了其余3种鱼类的稳定碳同位素范围（-21.97--16.68）, 表明斑鰶栖息水层分布较广, 和传统的中上层鱼类有明显差异; （2）斑鰶营养级随叉长增加而降低, 青鳞小沙丁鱼营养级随叉长增加而增加, 黄鲫和赤鼻棱鳀营养级随叉长变化不明显; （3）与胃含物分析方法相比, 赤鼻棱鳀营养级偏高0.7左右, 可能与赤鼻棱鳀摄食较多底层虾类有关, 其他3种鱼类稳定同位素测定结果略高, 但基本相当。本研究结果可为认识莱州湾渔业生物的营养关系以及构建食物网提供依据。

Long-term overfishing and environmental pollution has led to a high degree of change in Laizhou Bay fisheries resource structures. Since 1980, small pelagic fish have become the new dominant species in this area. These small pelagic fish play a connecting role in the food chain and are often one of the key groups in marine ecosystems. Research on the trophic level of Engraulidae and Clupeidae fish in Laizhou Bay based on stomach content analysis has provided useful but dated information. More up-to-date research is now necessary. Based on bottom trawl surveys in Laizhou Bay during summer and autumn, 2011, the stable isotope signatures of four Engraulidae and Clupeidae species revealed that the stable carbon isotope ratios ranged from -21.97‰ to -11.67‰, while stable nitrogen isotope ratios ranged from 8.54‰ to 15.95‰. ANOVA analysis revealed that δ13C and δ15N varied significantly among the four species （P〈0.05）. Linear regression analysis between fork length and stable isotopic ratios showed that Sardinella zunasi and Konosirus punctatus had significant ontogenetic variation in terms of δ15N （P〈0.05）, while Setipinna taty and Thrissa kammalensis did not （P〉0.05）. The S. zunasi trophic level ranged from 2.80 to 4.88, with the average being 3.52±0.46; the K. punctatus trophic level ranged from 2.71 to 4.29, with the average being 3.34±0.33; the T. kammalensis trophic level ranged from 3.38 to 4.42, with the average being 3.97±0.28; the S. taty trophic level ranged from 3.28 to 4.13, with the average being 3.76±0.23. According to the stable carbon and nitrogen isotope results, we can draw the following conclusions： （1） The stable carbon isotope values showed that K. punctatus trophic level range （-20.92 to -11.67） almost covers that of the remaining three species （-21.97 to -16.8）, meaning that K. punctatus inhabits a wide depth range which is different to that of other pelagic fish; （2） The K. punctatus trophic level decreases with increasing fork length while that of S. zunasi increases with increasing fork length, no such changes were observed in the other two species; （3） The T. kammalensis trophic level is about 0.7 times larger than that reported from the traditional stomach content analysis, which may be related to increased feeding on shrimp. The trophic level of the other three species was slightly higher according to the stable isotope results, but not significantly so.