The community composition and structure of gastrointestinal tract helminths were investigated in largemouth bass (Micropterus salmoides) and lake whitefish (Coregonus clupeaformis), both are important fish species in the Laurentian Great Lakes basin. The book provides a thorough identification of the helminths species infecting the gastrointestinal tract of largemouth bass in 15 inland lakes in Michigan’s Lower Peninsula. The retrieved helminths were generalists in nature and represented four phyla and nine species. The gastrointestinal tract helminths retrieved from spawning lake whitefish stocks ( from lakes Huron and Michigan) were also generalists in nature and demonstrated two phyla and five species, along with a swimbladder nematode. The book demonstrates the significant effects of the Great Lakes (Huron and Michigan) and watershed on infection parameters of both fish species. The findings displayed in this book represent the most comprehensive parasitological study ever conducted on largemouth bass or lake whitefish in the Great Lakes.