Spawning patterns and interspecific matings of sympatric white (Catostomus commersoni) and longnose (C. catostomus) suckers from the Gouin reservoir system, Quebec

Abstract

White (Catostomus commersoni) and longnose (C. catostomus) suckers from the Gouin reservoir, Quebec, and a small upstream lake (Lac des Cinq Miles) spawned in the same stream. White suckers numerically dominated the runs in all years; however, abundances of both species decreased eightfold during a year when the reservoir level was lowered for maintenance. Return rates of individuals of both species tagged during the spawning run were poor in the following year, and only a few fish (<0.6%) skipped a year to spawn 2 years later. Although some individuals of both species occurred at all monitored spawning areas, white suckers concentrated their spawning activity over sites with boulders, whereas longnose suckers were most abundant over gravel. Differences in the courtship behaviour of the two species initially discouraged interspecific matings. However, white sucker males ultimately participated in 32% of the female longnose sucker matings, though spawning of male longnose suckers with female white suckers was not observed. White suckers spawned in groups or in pairs, whereas in all instances longnose suckers spawned with two or more males.