On the Ecology of Skeena River Whitefishes, Coregonus and Prosopium

Abstract

Incidental information on the ecology of the common (Eastern) whitefish, Coregonus clupeaformis, and the Rocky Mountain whitefish, Prosopium williamsoni, was collected in the course of the Skeena River Salmon Investigation of 1944–1948. The common whitefish has been found in only four Skeena lakes, which have characteristics that are mainly oligotrophic. Rocky Mountain whitefish were taken in all the lakes where netting was done, which included warm and shallow, as well as deep and cold, bodies of water. The bottom fauna of Lakelse, Babine and Morrison Lakes was described. During the summer common whitefish were most abundant in depths of 10–15 m., and Rocky Mountain whitefish at 5–10 m. The food of the two species was very similar, and consisted mostly of bottom organisms. An exception was that of common whitefish in Morrison Lake, which had fed almost wholly upon plankton crustaceans. This situation was associated with the paucity of bottom fauna in the lake. The important competitors for food of the whitefishes, identified on the basis of common food and habitat, were peamouth chub, Mylocheilus caurinum, and squawfish, Ptychocheilus oregonense. Chief predators of the whitefish were lake trout, Cristivomer namaycush, and ling, Lota lota. However, there was no evidence that predation upon either whitefish was particularly serious. The oldest common whitefish were X years of age (473 mm. fork length), and Rocky Mountain whitefish IX years (365 mm. fork length). No food organisms occur in the Skeena lakes in such abundance as do certain amphipods in other Canadian lakes where the common whitefish is fished commercially. This scarcity of suitable food is considered to be the main condition limiting the abundance of the Skeena populations of common whitefish.