The link between brook trout young-of-year ecology and groundwater hydrology: A topographic index approach (Salvelinus fontinalis)

Lake-dwelling brook trout (Salvelinus fontinalis ) are closely linked to the terrestrial environment surrounding the waters they inhabit through their use of groundwater habitat. A large-scale approach was taken to identify this habitat use by young-of-year (YOY) brook trout across 21 lakes in Algonquin Park, Ontario using a topographic index (TI) approach in a Geographical Information System (GIS). Brook trout YOY habitat use on two small lakes was found to be spatially traditional with high levels of annual (>88%) and seasonal (>60%) reuse. On a larger scale, 231 field-observed habitats were found around the 21 lakes, of which only 74(32%) contained YOY. Preference for small, cold streams was correlated with brook trout YOY presence and linked to the occurrence of groundwater. All but three of the study lakes contained YOY in at least one habitat. The number of YOY habitats around the study lakes was significantly lower than expected given a fractal or geometric relationship between lake surface area and perimeter. The TI approach performed well at identifying potential YOY groundwater habitat, eliminating an average of 92.5% of a lake's shoreline not associated with brook trout habitat. Given that over 60% of the habitats found in the field are omitted from the Ontario Base Map (OBM) system, this technique, when combined with knowledge of the ecology of the brook trout, has many management implications for conserving lake-dwelling brook trout populations.