Dietary effects on the fatty acid signature of whole Atlantic cod (Gadus morhua)

Abstract

Understanding the influence of dietary fatty acids on whole fish is necessary to evaluate the degree to which fatty acids may be used for understanding foraging patterns in fish, as well as in marine mammals that consume their prey whole. Adult Atlantic cod (Gadus morhua) were fed two prey items that differed significantly in fat content and fatty acid compositions. Cod were first fed squid (Illex illecebrosus, 2.0% fat) for 6 weeks, followed by Atlantic mackerel (Scomber scombrus, 15.7% fat) for 8 weeks. Twenty whole cod were individually analyzed at each of 0, 3, 6, 11, and 14 weeks. Despite being on a low-fat squid diet, in only 3 weeks, cod fatty acid patterns changed significantly to reflect the patterns found in squid and did not further change at 6 weeks. When switched to a high-fat mackerel diet, total body fat of cod increased and the fatty acid composition of cod changed significantly in the direction of patterns found in mackerel. Despite changes in cod fatty acid signatures, cod were readily distinguished from the fatty acid signatures of their diets. Our results provide support for the use of fatty acids as indicators of diet at upper trophic levels.

Tracing aquatic food webs using fatty acids: from qualitative indicators to quantitative determination

“…In contrast, fishes have a more limited ability to modify FA, but may still be better able to modify some exogenous FA than birds and mammals. However, given that their natural marine diets contain high levels of essential long-chain n-3 and n-6 PUFA (e.g., Ackman 1980) , overall modification of dietary FA in fish is probably limited relative to direct dietary deposition (e.g., Kirsch et al 1998 ;see Sect. 12.3.2.1).…”

“…Although further studies are needed, current evidence indicates that effects of short-term fasting are unlikely to have major impacts on overall FA composition. In summary, although biosynthesis and modification of FA does occur, by far the greatest quantitative contribution to the fat stores of higher marine or aquatic predators arises from direct deposition of dietary FA (Ackman and Eaton 1966 ;Rouvinen and Kiiskinen 1989 ;Colby et al 1993 ;Iverson 1993 ;Kirsch et al 1998 ;Iverson et al , 2007 .…”

Stomach contents of long‐finned pilot whales,Globicephala melas, mass‐stranded on Farewell Spit, Golden Bay in 2005 and 2008

“…Nevertheless, given the inherent difficulties in studying the feeding ecology of oceanic cetaceans, the general lack of knowledge of the biology of whales in New Zealand waters, and the complete lack of any temporal information on diet for any species, ongoing research monitoring diet is of value. Compared with the short-term record of diet provided by stomach contents, diet information from stable isotope analyses reflects the average composition of food resources that have been assimilated over periods of days to months, depending on rates of tissue turnover (Tieszen 1978;Kirsch et al 1998Kirsch et al ,2000. Research involving combined use of stomach content analysis, together with carbon and nitrogen isotope measurements of marine mammal tissues, is recommended to gain further insights on trophic relationships and feeding ecology, including spatial use of habitat and temporal shifts in diet.…”

Diet of long-beaked common dolphin (Delphinus capensis) in the East Sea, Korea

“…The essential FAs such as 20:5n-3 and 22:6n-3 are especially important dietary FAs, as marine mammals must obtain essential FAs from their diet, much like humans. Moreover, this method complements the disadvantages of SCA, because a long-term indication of diets taken over periods of up to months can be derived from FA analysis (Kirsch et al 1998).…”