Ackman R G, Takeuchi T
Lipids. 1986 Feb;21(2):117-20. doi: 10.1007/BF02534431.
In Atlantic Canada the Atlantic salmon Salmo salar change from the parr stage to the smolt stage while still in fresh water, preparatory to migration to salt water. In some stocks this takes place during the second overwintering. In several hatcheries where the water temperature drops to 0-0.5 C and the ponds ice over, there is a high incidence of erosion of the dorsal and pectoral fins and sometimes of the caudal fin. No disease organism has been identified, and the lesions heal over in most cases. Dietary fatty acids were thought to be a factor. A detailed study of lipid recoveries and classes has shown that in the skins of abnormal fish the total lipid is 7.8% compared to 4.7% in control fish. Unexpectedly, an analysis of one lot of healthy smoltstage wild fish showed that whole bodies have only a quarter of the lipid of comparable hatchery fish. Comparison of fatty acids showed that wild fish lipids include a higher proportion of arachidonic acid than those of the hatchery fish. In the latter, linoleic acid is provided readily by diet but the elongation to arachidonic acid evidently does not proceed. These results suggest that the smolt lipid is involved intimately with either the cause of the dermal lesion or is a defense mechanism, possibly mediated through oxygenase activity.
在加拿大大西洋地区，大西洋鲑鱼（Salmo salar）在仍处于淡水环境时就从幼鲑阶段转变为银化幼鲑阶段，为洄游至咸水做准备。在一些种群中，这种转变发生在第二次越冬期间。在几个孵化场，水温降至0 - 0.5摄氏度且池塘结冰，背鳍和胸鳍有时还有尾鳍出现侵蚀的发生率很高。尚未鉴定出致病生物，且在大多数情况下损伤会愈合。膳食脂肪酸被认为是一个因素。对脂质回收率和类别进行的详细研究表明，异常鱼的皮肤中总脂质含量为7.8%，而对照鱼为4.7%。出乎意料的是，对一批健康的银化幼鲑阶段野生鱼的分析表明，其全身脂质含量仅为可比孵化场鱼的四分之一。脂肪酸比较显示，野生鱼的脂质中花生四烯酸的比例高于孵化场鱼。在孵化场鱼中，亚油酸很容易从饮食中获取，但显然无法转化为花生四烯酸。这些结果表明，银化幼鲑的脂质与皮肤损伤的原因密切相关，或者是一种防御机制，可能通过加氧酶活性介导。
