Endohelminth diversity of largemouth bass and lake whitefish in Michigan

In this study, the community composition and structure of gastrointestinal tract (GIT) helminths were investigated in two species of fish: largemouth bass (Micropterus salmoides) and lake whitefish ( Coregonus clupeaformis), both of which are important fish species in the Laurentian Great Lakes basin. The first study was designed to identify the helminth species infecting GIT of largemouth bass (LMB) in 15 inland lakes in Michigan's Lower Peninsula, and to describe their community structure. A total of 16,700 worms were retrieved from the GITs of 641 adult LMB collected between July 2002 and September 2005. Over 75% of the LMB examined harbored at least one helminth species in their GIT, with relatively high intensity (34.72+35.07 worms/fish) and abundance (26.05+35.07 worms/fish). Collected helminths were generalists in nature and represented four phyla and nine species: Neoechinorhynchus cylindratus, Leptorhynchoides thecatus, Acanthocephalus parksidei, Echinorhynchus salmonis, Pomphorhynchus bulbocolli, Proteocephalus ambloplitis, Contracaecum sp., Camallanus oxycephalus, and Leuceruthrus micropteri. The generalized linear mixed model analyses demonstrated the presence of significant effects of the Great Lakes watershed, the presence of inlets, the presence of outlets, and public access on infection parameters of LMB-GIT worms. Diversity was significantly greater in inland lakes with public access.;In the second study, prevalence, intensity, and abundance of swimbladder nematode infections were estimated in 1,272 lake whitefish (Coregonus clupeaformis) collected from four sites in northern lakes Huron (near Cheboygan and De Tour Village ports) and Michigan (near Big Bay de Noc and Naubinway ports) from fall 2003 through summer 2006. Morphological examination revealed characteristics consistent with that of Cystidicola farionis Fischer 1798. Although C. farionis was detected in all four stocks that were examined, Lake Huron stocks generally had higher prevalence, intensity, and abundance of infection than Lake Michigan stocks. A distinct seasonal fluctuation in prevalence, abundance, and intensity of C. farionis was observed. Lake whitefish (LWF) heavily infected with C. farionis were found to have thickened swimbladder walls.;The third study compliments the second study as it was designed to identify the community composition and structure of GIT helminth infections in LWF stocks. A total of 21,203 helminths were retrieved from the GITs of 1,284 spawning LWF. Collected helminths were generalists in nature and represented two phyla and five species: Acanthocephalus dirus, Neoechinorhynchus tumidus, Echinorhynchus salmonis, Cyathocephalus truncatus, and Bothriocephalus sp. In order to evaluate the effects of lake, sampling site, year, and season (as well as interactions of these factors), a series of statistical models were fitted to the helminth (all combined and separately for each helminth species) prevalence, abundance, and intensity. LWF from Lake Huron had significantly greater rates of infection than LWF from Lake Michigan. Helminth infection parameters peaked in the spring, while diversity was highest in the winter samples. The findings of this study represent the most comprehensive parasitological study ever conducted on largemouth bass or lake whitefish in the Great Lakes.