Seasonal changes in lipid content and fatty acid composition of vendace (Coregonus albula) and its plankton food

Lake Arendsee is known to be one of the best lakes for vendace (Coregonus albula) in Germany. Fish of this species and their freshly ingested zooplankton prey caught in this lake between April 1994 and May 1995 were analysed for the seasonal pattern of the fatty acid composition of triglycerides (TG) and phospholipids (PL). Zooplankton of Lake Arendsee was characterized by a high level of n-3 polyunsaturated fatty acids (PUFAs) in both lipid classes. The relative amount of n-3 PUFAs in TG was fairly constant over a long period (June 1994 to March 1995), while the PL level of n-3 PUFAs was extremely variable. This was mainly caused by the variation of docosahexaenoic acid. The n-6 PUFAs in TG and PL of thr zooplankton were found in lower amounts as compared to those of n-3 PUFAs. The lipid content of vendace in Lake Arendsee varied seasonally with the highest fat content at the end of September prior to spawning. The level of n-3 PUFAs in TG exhibited a seasonal variation in this fish as well. The highest relative amount of n-3 PUFAs was found during the spawning season. This result did not correspond to the level of n-3 PUFAs in zooplankton. The n-3 PUFAs in PL of vendace showed little variation, with the exception of the period from June to September but were lower as compared to the levels observed in zooplankton. During this period, the relative concentrations of docosahexaenoic acid (22:6 n-3) were low. The proportion of n-6 PUFAs in both lipid fractions remained fairly constant. No clear seasonal changes in the relative amount of n-6 PUFAs in both lipid classes could be observed. N-3 PUFAs were preferentially incorporated into ovaries while the testes contained more free fatty acids (FFA) than TG. The relative amount of both arachidonic (20:4 n-6) and eicosapentaenoic acid (20:5 n-3) was greater in the testes than in the ovaries.