An evaluation of the diet of Emphasis Type="Itali

Authors: L J Nordin M T Arts O E Johannsson W D Taylor

Publish Date: 2007/05/15

Volume: 42, Issue: 3, Pages: 421-436

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Abstract

Diets of Mysis relicta from four lakes in central Ontario that had been invaded by Bythotrephes longimanus and three lakes that had not been invaded were investigated using gut content analysis and fatty acid FA composition Gut content analysis of M relicta revealed a high incidence of cannibalism in all lakes and consumption of B longimanus and native zooplanktivorous midges in the genus Chaoborus in lakes where these were present Cladocera other than B longimanus were present in the guts of all M relicta examined except those from Bernard Lake the lake with the most B longimanus In that lake B longimanus was the most frequent diet item Copepod remains were found in 60–100 of M relicta guts with the lowest frequency occurring in Bernard Lake Fatty acids FA that contributed strongly to the variation in FA composition in M relicta as revealed by a principal component analysis were C160 palmitic acid C161n7 palmitoleic acid C181n9c oleic acid C204n6 arachidonic acid C205n3 eicosapentaenoic acid and C226n3 docosahexaenoic acid Significant differences in FA amount and composition of M relicta were found between invaded and noninvaded lakes and among lakes within these groups Generally M relicta in noninvaded lakes had higher concentrations of C160 C181n9c C182n6c linoleic acid C183n3 αlinolenic acid and C204n6 while M relicta in invaded lakes had higher concentrations of C226n3 Two of the noninvaded lakes had lower water transparency as measured by Secchi depth which may be the reason why mysids and abundant populations of Chaoborus spp could be found in the water column during the day However differences in FA profiles and gut contents of M relicta between invaded and noninvaded lakes are consistent with competition for Cladocera in the presence of the invader rather than preexisting differences among lakes We conclude that the diet of M relicta is affected by the invasion of B longimanusWe are grateful to Emily Parrott and Norman Yan of York University for the B longimanus abundance data Thank you to Kelly Bowen Rob Quinn Tyler Spencer John Butler and Rachel Nagtegaal for help in the field and in the laboratory Secchi depth data were provided by A Strecker Department of Biology Queen’s University and J Hovius Department of Integrative Biology University of Guelph Funding for this research was provided by the Department of Fisheries and Oceans Canada through the Environmental Science Strategic Research Fund ESSFR an NSERC PGSM Scholarship to LJN and by Environment Canada

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