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Reproduction of three species of suckers (Catostomidae) in British Columbia Geen, Glen Howard

Abstract

Reproduction of three species of suckers, Catostomus catostomus, the longnose sucker, Catostomus commersoni, the white sucker, and Catostomus macrocheilus, the largescale sucker, has been studied in British Columbia during the summers of 1956 and 1957. These species spawned in the spring months depending on locality and annual differences in climate. 'White and longnose suckers spawned primarily in inlet streams although moderate runs of the former to outlet streams have been noted. Largescale suckers usually spawned in outlets. No lake spawning was observed. Overlap of breeding seasons and co-habitation of the same spawning stream by white and largescale suckers may explain occasional hybridization between these species. Spawning females matured a year later, were larger and lived longer than the males of all three species. Detailed work at Baker Lake, near Quesnel, indicated males entered the spawning stream before the females and generally remained till the females had returned to the lake. In 1956 the sex ratio of white suckers was 1:1. In 1957, 2 males to 1 female were present in the spawning stream. Low water levels may have prevented larger females, which were predominantly marked, from moving upstream. As a result of these conditions fish may have spawned in other streams thus masking any tendency to return to the same stream in successive years. The longnose suckers sex ratio of 2 marked females : 1 marked male suggests that a differential mortality acting either from hatching or after first spawning is in effect. Numbers of unmarked fish were not significantly different. Factors associated, with migrations at Baker Lake were studied. Adult migration was primarily at night. Numbers of white suckers migrating into the inlet stream were dependent on temperature change from one day to the next. A similar situation prevailed during the main portion of the longnose sucker run but no such relationship existed at the beginning of the run. Limno-logical conditions in the lake may have influenced migration to the creek. Fry in the inlet streams moved downstream at night. The migration was halted by placing a gas lantern over the creek. Juveniles remained in the outlet- stream up to four years before entering the lake. Their migration into the lake was related to rising temperature.

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