Effects of Temperature on Movements of Prespawning Brook Sticklebacks, Culaea inconstans, in the Roseau River, Manitoba

During spring, brook sticklebacks (Culaea inconstans (Kirtland)) in the Roseau River, Man., moved upstream from deep, cool, overwintering areas to shallow warmer waters in meltwater ponds and ditches, where they reproduced. Movement upstream occurred during daylight, in water velocities less than 90 cm/sec, when a temperature gradient was present, but ceased at night or when water temperatures exceeded 19–20 C. In a horizontal laboratory gradient, prespawning sticklebacks from the field selected a range of temperatures from 14.9 to 20.2 C, considerably narrower than after spawning. More prespawning sticklebacks moved upstream in an artificial stream tank at water temperatures of 15.6 and 21.1 C than at 7.2, 10.0, or 23.9 C, and more moved upstream in light than in darkness.