GROUNDWATER AND THE INCUBATION AND EMERGENCE OF BROOK TROUT (SALVELINUS-FONTINALIS)

Groundwater was observed to discharge through brook trout (Salvelinus fontinalis) redds during the November to April incubation period in Canadian Shield waters. Groundwater was important for protecting redds from infiltrating surface water acid ice. Physical and chemical characteristics of individual redd environments were similar during the incubation period. Substrate temperature and oxygen levels were reduced in nonredd substrates 100 cm from redds. The stability of discharge, temperature, dissolved oxygen, and specific conductance during incubation was similar between redd and nonredd substrates (less than or equal to 100 cm away). The quality of redd habitats and embryo survival did not appear to be related to female competition for redd sites or time of spawning. There was evidence of density-dependent control of spawning success and the adaptive nature of alevin emergence behaviour in Canadian Shield waters.