阿根廷巴塔哥尼亚陆架拉氏南美南极鱼(Patagonotothen ramsayi)不同组织中脂肪酸分布及食物来源指示

作为南美南极鱼科中数量最为丰富的一个种,拉氏南美南极鱼(Patagonotothen ramsayi)在巴塔哥尼亚海域食物网能量流动中起着重要的传递作用。目前针对该鱼种的营养及摄食生态学研究主要集中于反映短期摄食的传统胃含物分析上。为此,本研究分析了拉氏南美南极鱼3种组织(肌肉、肝脏和性腺)中脂肪酸含量及分布情况,并就3种组织中的脂肪酸是否能表征其食性及食性转换进行了探究。结果表明,拉氏南美南极鱼体内共检测出27种脂肪酸;由于涉及生长、繁殖等因素影响,肝脏、性腺组织对于脂肪酸的储存及使用情况并不适用于指征食性,而肌肉组织更新时间相对较长,故能够较好地反映其对食物中脂肪酸的吸收。对不同体长组拉氏南美南极鱼肌肉组织中脂肪酸分析可知,未成熟拉氏南美南极鱼(100~240 mm)主要摄食浮游性生物;随着体长增加对底栖生物的摄食也随之增加,由浮游性摄食方式转变为浮游-底栖性摄食。另外,因拉氏南美南极鱼摄食一定量的渔业丢弃物,导致腐生食物链和捕食食物链的贡献率特征弱化。研究结果进一步显示,针对大洋性鱼类,与肝脏和性腺相比,肌肉组织脂肪酸更适用于表征食物来源。

The distribution of fatty acids in tissues of rock cod (Patagonotothen ramsayi) in the Argentina Patagonian Shelf and their implications to feeding habit

As one of the most abundant species of family Notothenioidei, rock cod (Patagonotothen ramsayi) plays an important role in energy transfer in the food web in the Patagonian Shelf. Currently, the work on feeding ecology of this species mainly bases on the conventional stomach content analysis, which only reflects short-term variation in feeding. Therefore, this study analyzed the distribution of fatty acids in three tissues (muscle, liver and gonad) of rock cod, and analyzed whether fatty acids in these tissues can characterize their feeding habits and transfer of diet. The results indicate that 27 kinds of fatty acids were detected in the tissues of rock cod. The storage and use of fatty acids in liver and gonad tissues are not suitable for indicating the diet of rock cod because they are involved in growth and reproduction. Compared to liver and gonad tissues, the longer renewal cycle of muscle tissue may better reflect its absorption of fatty acids from food. For the analysis of fatty acids in the muscle tissue of the rock cod in different size groups, it is inferred that the small-size rock cod (immature individual, 100−240 mm) mainly fed on planktonic organisms. The benthic feeding characteristics of rock cod increase with the increasing of size, and the feeding pattern transfer from planktonic feeding to planktonic-benthic feeding. In addition, due to the consumption of a certain amount of fishery discards by rock cod, the contribution rate of saprophytic food chain to predatory food chain is weakened. The results derive from this study further demonstrate that, compare to tissues of liver and gonad, the fatty acids of muscle tissue can be more suitable to indicate the food source of oceanic fish species.