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 Ca nadian Shield waters. Groundwater was important for protecting redds f rom infiltrating surface water acid ice. Physical and chemical charact eristics of individual redd environments were similar during the incub ation period. Substrate temperature and oxygen levels were reduced in nonredd substrates 100 cm from redds. The stability of discharge, temp erature, 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 no t 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 Cana dian Shield waters.