BROOK TROUT SPAWNING AREAS IN LAKES

Nine lakes containing self-sustaining populations of brook trout (Salv elinus fontinalis) were surveyed to provide quantitative information o n the abundance and distribution of redd sites. We measured rates of g roundwater flow at redds in four of these lakes, and in one of these l akes we also compared the frequency of site use over four years from s pawning observations. The number of redd sites in each lake ranged fro m 1 to 53 (mean = 30) with most found relatively close to shore (appro ximate to 1 m deep). Spawning areas per lake (16.9-829.4 m(2)) were no t related to lake size and were often not continuous areas of littoral zone habitat. Rates of groundwater flow in lakes, averaged across red d sites in each lake, ranged from 20.0 to 107.9 ml.m(-2).min(-1). The intensive survey of redd site use in one lake demonstrated that only 1 1% of sites (10 of 92) were used in all four years of observation. The mean rates of groundwater flow at sites used in all four years were s ignificantly greater than at sites used intermittently Data from this and other studies point to the conservation of subcatchments associate d with groundwater discharge areas used by spawning brook trout as a m eans of maintaining self-sustaining populations.