Lipid class and fatty acid composition of plankton and settling particles at a fish enclosure, and of cod (Gadus morhua) in Gilbert Bay, Labrador

Van Biesen, Geert (2003) Lipid class and fatty acid composition of plankton and settling particles at a fish enclosure, and of cod (Gadus morhua) in Gilbert Bay, Labrador. Masters thesis, Memorial University of Newfoundland.

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Abstract

A small cod enclosure was set up in Gilbert Bay, Labrador. The lipid class and fatty acid composition of plankton and settling particles on a transect away from the net pens were determined in order to see if biomarkers for the dispersal of organic waste could be identified. Free fatty acid levels and the proportions of the long-chain monounsaturated fatty acids 20:1ω9, 22:1ω9 and 22:1ω11 in the settling particles close to the pens (5 m) were significantly higher (p < 0.05) than before the fish enclosure was in operation, and than further away from the pens. This is consistent with a higher input of feed and/or feces at this location. Free fatty acids are the major lipid class in fish feces, while the long-chain monounsaturated fatty acids are present in high proportions in the feed and in fish feces. -- Gilbert Bay cod (Gadus morhua) muscle and liver were analyzed for lipid content and composition and compared interannually and with offshore cod. This study could not detect any clear differences between Gilbert Bay cod from 2001, offshore cod from 2001 and offshore cod from 2002. However, Gilbert Bay cod caught in 2002 just after the winter had different muscle and liver fatty acid profiles than the three aforementioned groups of cod, which were caught in midsummer. The differences can be related to starvation during the winter, as evidenced by an average lower hepatosomatic index and a higher water content of muscle and liver.

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