OBSERVATIONS OF FISH MORTALITY ASSOCIATED WITH ICE BLASTING ON THE LOWER RIDEAU RIVER, OTTAWA, ONTARIO

Six days of the annual ice blasting program were monitored to assess b last-induced fish mortality. We observed 569 fish mortalities in two r eaches of the Lower Rideau River (Ontario, Canada) during the two moni toring periods. Rock Bass, Ambloplites rupestris, was the most commonl y observed fish killed (81% of total mortalities) in each of the two r eaches assessed. The numbers of dead fish observed during the blasting program were highly variable and presumably dependent on the site-spe cific habitat characteristics at each blast location. All but two fish mortalities were observed on or just below the water surface. Our obs ervations suggest that considerable numbers of fish, of primarily smal l sizes classes, are killed during the annual ice removal program. Our findings also suggest that some mortalities may sink to the bottom an d are difficult to quantify due to the hazardous conditions of the ice blasting exercise.