GROUNDWATER AND THE SELECTION OF SPAWNING SITES BY BROOK TROUT (SALVELINUS-FONTINALIS)

Spawning areas selected by brook trout (Salvelinus fontinalis) displayed variable relationships to discharging groundwater across geologic regions. In Canadian Shield waters, spawning was associated with areas of distinct, discharging groundwater. The specific mechanism of selection could not be determined. Groundwater did not appear to influence the selection of individual redd sites within these discharge areas. Competition among females for the opportunity to spawn in a limited area defined by the discharging groundwater appeared to control the selection of redd sites. In southwestern Ontario streams, discharging groundwater was prominent throughout areas of spawning both at redds and at adjacent, nonspawning substrates (less than or equal to 7 m). Consequently, relationships between groundwater and spawning site selection were ambiguous. On the unglaciated plateau of central Pennsylvania, no groundwater was observed in redds or nonspawning substrates in streams. Brook trout management programmes must consider these groundwater relationships and therefore the impact of land use on groundwater quality and quantity.