Factors Affecting Seasonal Habitat Use Of Native Brook Trout (Salvelinus Fontinalis) In Urban Headwater Streams

To better understand the ecology of coldwater fishes in urban-dominated landscapes, factors influencing seasonal brook trout (Salvelinus fontinalis) habitat use were assessed using backpack electrofishing surveys in three urban groundwater-fed streams in central Ontario. Generalised additive models revealed that yearling brook trout (<100 mm TL) were primarily influenced by water quality (stream temperature, conductivity), while older brook trout (>= 100 mm TL) were primarily influenced by stream morphology (water depth, undercut bank volume). Colder stream temperatures were preferred by yearlings in summer, whereas they occupied the warmest temperatures available in winter and spring. Yearlings were never found in sites with high stream conductivity (>= 900 mu s/cm), regardless of season, which may be attributed to poor water quality in stream sections with stormwater influence. Older brook trout were found mainly at intermediate pool depths in spring and summer, while there was a greater range of depths used during the spawning season. Undercut banks were important for older brook trout occupancy at all times of year. The protection of groundwater aquifers in urban watersheds is recommended to maintain optimal temperature regimes for the persistence and successful recruitment of native brook trout.