Comparison of fatty acid composition and astaxanthin content in healthy and by M74 affected salmon eggs from three Swedish river stocks

M74 is an extremely lethal syndrome appearing during the yolk sac-swim up stage. The syndrome is known in the Baltic Sea salmon but is still unknown in Atlantic salmon. In this study, Baltic salmon eggs from females showing M74 syndrome were compared with those from healthy females. Further, the study also included a comparison between eggs from a western (Atlantic) and two eastern (Baltic) Swedish stocks. We found differences between the Atlantic and Baltic stocks in the content of 22:6 (n-3) both in the phospholipid and triacylglycerol lipid fractions (P < 0.013, P < 0.0001, respectively). In addition, the eggs from the Baltic stocks had a much lower astaxanthin content than the west coast stock (P < 0.0001). In the phospholipid fraction, an inverse relation was found between river temperature and 22:6 (n-3) content, when rivers were arranged according to day degrees during egg development. M74 affected eggs had a higher content of 22:6 (n-3) compared to non-affected M74 ones. We found differences in the (n-3)/(n-6) ratio between healthy and M74 eggs (P < 0.0046). Also, the astaxanthin content was significantly lower in M74 eggs (P < 0.0018). We suggest that egg lipid composition is under strong genetic influence. Further, we suggest that in healthy eggs of Baltic salmon, there is a balance between oxidative potential and antioxidant capacity and that a disturbance of this balance at the cellular level could possibly be a cause of the M74 syndrome. (C) 1998 Elsevier Science Inc. All rights reserved.