Localization of a source of marine odd chain-length fatty acids. II. Seasonal propagation of odd chain-length monoethylenic fatty acids in a marine food chain.

The unusual occurrence of elevated levels of odd chain length fatty acids (OCFA) in smelt taken during winter months in Jeddore Harbour, Nova Scotia, is due to the dietary intake of large numbers of the amphipod Pontoporeia femorata (Kröyer). Sampling over two winters confirms that the seasonal peak period for this amphipod in stomachs is mid-December to the end of February. The distributions of monoethylenic isomers are compared to distinguish exogenous and endogenous smelt dietary features in terms of the geographically limited phenomenon of high OCFA levels and the essential absence of biological activity for these acids.