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The lipid composition of Patagonian toothfish from the Macquarie Island region : ecological and dietary implications within a regional food web

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Wilson, Gareth Anthony (2004) The lipid composition of Patagonian toothfish from the Macquarie Island region : ecological and dietary implications within a regional food web. PhD thesis, University of Tasmania.

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Abstract

Recent commercial interest in the Patagonian toothfish (Dissostichus eleginoides) in
the Macquarie Island region has heightened the need for a better understanding of
the life history of this species. Of particular interest are dietary considerations.
However, despite the importance of toothfish in the deep-sea food web of this and
other Southern Ocean regions, relatively little is known of their diet. Current
knowledge is based upon the examination of stomach contents, a technique that
fails to identify with any certainty long-term dietary composition. The determination
of lipid composition may provide a simple and effective means of determining the
diet of toothfish, one that complements traditional techniques. Specifically, many
higher order species are thought to deposit fatty acids derived from prey into storage
with little or no modification. Constituent fatty acids of a predator may therefore
represent a temporal integration of diet. The lipid composition of toothfish was
investigated in relation to both physical (sex, age/size) and fishing parameters
(region, season, depth, time of day). Each parameter was compared using a variety
of statistical methods including multidimensional scaling and linear discriminant
analysis. Significant variations in total lipid content, lipid class composition and
especially fatty acid composition between fish of different sizes (ages) points to a
potential shift in diet as fish mature. Eicosapentaenoic and docosahexaenoic acids
were those fatty acids most responsible for the observed variation with size. The
influence of the remaining parameters on lipid composition is less pronounced. To
determine whether these variations in lipid composition were due to possible
variations in diet, a comparison with potential prey species was undertaken. This
involved the examination of 21 species of midwater fish, including 8 species of
Myctophidae, and 6 species of squid. Many of these species are know to contribute
to the diet of toothfish in the Macquarie Island region. The results of statistical
analysis suggest that the diet of Patagonian toothfish at Macquarie Island may vary
to a far greater extent, relative to size increases, than is suggested by stomach
content analysis. For instance smaller sized toothfish are more closely linked to
squid, based on fatty acid composition, than are larger toothfish. Most notable with
regards to potential fish prey is that the fatty acid compositions of Myctophidae are
more closely related to larger rather than smaller toothfish, possibly indicating a shift
in dietary preference as toothfish mature.

Item Type: Thesis (PhD)
Keywords: Patagonian toothfish
Copyright Holders: The Author
Copyright Information:

Copyright 2004 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2004. Includes bibliographical references

Date Deposited: 04 Feb 2015 23:29
Last Modified: 11 Mar 2016 05:54
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