Spawning and Early-Life Ecological Phases of the White Sucker in Jack Lake, Ontario

In 1979, peak spawning of white suckers Catostomus commersoni occurred on April 20–21 (9–15 C and 17–22 C) at night over fast riffle in a tributary of Jack Lake. Eggs hatched in 16 days and drift occurred in 27–29 days; maximum drift occurred between 2100 and 0100 hours. An estimated 11,800 postlarvae drifted to the nursery, a new boat channel and marina area in Jack Lake. Postlarva phase 1 (terminal mouth, 15–17 mm total length, TL) and phase 2 (subterminal mouth, 18–34 mm TL) were spent in the nursery. At 28 C (midsummer), phase-3 fish (35–84 mm TL) moved out to the lake shores near the nursery, and later dispersed into the lake basin. Growth of white suckers was slower in phase 1 than in phase 2, and diets differed slightly between these intervals. Phase-3 fish did not grow significantly faster than phase-2 fish in spite of their more diverse diet. The cooler lake habitat may account for a lack of surge in the growth rate of phase-3 fish, or diversity of food may be an indication of food scarcity away from the nutrient-rich nursery area.