Introduction of Lake Trout (Salvelinus namaycush) to Inland Lakes of Ontario, Canada: Factors Contributing to Successful Colonization

Abstract

We evaluated the success of 183 introductions of lake trout (Salvelinus namaycush) in small inland lakes in Ontario, Canada. Our purpose was to identify variables associated with successful versus failed natural recruitment after introductions of hatchery-reared lake trout. Origin of donor stocks, angling regulations, geophysical and water quality characteristics, and fish species presence-absence of the recipient lakes were evaluated as possible factors contributing to colonization success. Origin of donor stock had some minor influence on the success of introduced lake trout in these lakes, but other factors, including angling, were also important. Closure of lakes to fishing was strongly associated with some successful introductions. MANOVA revealed differences in the geophysical and water quality variables, and fish community structures among the native, successful, and failed lakes. The lake groups were further distinguished by canonical variate analysis using either geophysical and water quality variables and/or presence-absence of fish species. Lakes were correctly classified to one of the three lake groups with 63-83% accuracy using a cross-validated, chance corrected, discriminant analysis. Lakes in which new lake trout populations failed to become established were smaller and shallower, had higher total dissolved solids, larger littoral areas, smaller hypolimnions, and richer fish communities, including more lake trout egg and juvenile predators, than lakes that were successfully colonized. Intensity of pre-dation by indigenous species was a possible cause of failure of introduced lake trout to establish self-sustaining populations. Similar fish communities in native and failed lakes suggested that invasion and colonization by lake trout was possibly determined by the order of arrival of colonizing species. This suggested that the present day Great Lakes fish communities, which have experienced a recent net gain in species, might be resistant to reestablishment of self-sustaining lake trout stocks.