Eggs of Baltic salmon displaying M74, yolk sac mortality syndrome have elevated levels of cholesterol oxides and the fatty acid 22:6 n-3

Abstract

In this study, level of cholesterol oxidation products (COPs), fatty acids and carotenoids were compared between healthy and M74 yolk sac mortality syndrome-affected eggs in two Swedish stocks of Baltic salmon ( Salmo salar). In addition were eggs from one stock of Atlantic salmon, originating from a Swedish west coast river analysed. This syndrome is believed to be the result of a combined environmental load of anthropogenic substances like chloroorganic pollutants and their metabolites. The syndrome is so far only found in Baltic salmon spending their post-smolt period in the Baltic Sea. COPs were significantly higher ( p=0.0289) in Baltic salmon eggs suffering from M74 than in healthy eggs, while no difference was found between healthy Baltic salmon eggs and those from the Atlantic stock ( p>0.05). The absolute level of COPs varied between rivers and year classes, while the level of cholesterol was relatively stable. However, the level of COPs was always higher in the M74-affected eggs compared to their healthy counterparts. The content of the fatty acid 22:6 n-3 (DHA; docosahexaenoic acid) was higher and astaxanthin lower in M74-affected eggs ( p=0.0056; p=0.0078, respectively) compared to healthy ones of the same stock and year class.