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Title: Squid and their prey : insights from fatty acid and stable isotope analysis
Author: Stowasser, Gabriele
ISNI:       0000 0001 3487 9293
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2004
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The analysis of both the digestive gland and the muscle tissue of Lolliguncula brevis showed that fatty acid and stable isotope signatures of the predator changed with time to reflect the signatures found for prey species fed in the experiment. Both short-term (digestive gland) and long-term effects (muscle) of the diet could be established through the analysis of these metabolically different tissues and the present study proved that these methods are viable for the use in reconstructing diets of squid species in the wild. Using this combination of techniques it was possible to identify seasonal and regional differences in the diet of L. forbesi. Ontogenetic differences in feeding could be established with bigger squid taking more varied prey and switching from a predominantly benthic to more pelagic diet. It was furthermore possible to distinguish between squid feeding in coastal and offshore waters respectively. Through the application of either fatty acid or stable isotope analysis to tissues of Todarodes sagittatus, Illex coindetii and Illex argentinus it was possible to determine short-term and long-term trends in the diet and formulate hypotheses as to which ecosystem mainly contributed to the diet. The diet of T. sagittatus was influenced by both benthic and pelagic prey species. Fatty acid profiles indicated a shift from small planktonic prey taken by small squid to a more piscivorous feeding in bigger squid. Similarities found for fatty acid signatures of deepwater fish and T. sagittatus suggest that this species spends part of its life cycle in deeper waters. Fatty acid signatures of I. coindetii indicated an omnivorous diet for this species determined by prey availability in two regions subject to different hydrographical conditions. Stable isotope signatures of I. argentinus indicated a diurnal feeding rhythm and regional differences in feeding in this highly migratory species point towards differences in migration routes from spawning to feeding grounds.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available