Bull Trout Form Two Discrete Lineages
Analysis of bull trout from British Columbia's coastal rivers finds that this species of special conservation concern comprises two genetically distinct groups. The two lineages are sufficiently separate enough for researchers to recommend that their conservation status be assessed separately by the Committee for the Status of Endangered Wildlife in Canada (COSEWIC).
Bull trout from north of the Squamish River have more in common with trout living in BC's interior watersheds than with bull trout from the lower Fraser River, its tributaries, and the Olympic Peninsula. This pattern reflects post-glacial dispersal routes of the fish, which includes crossing headwaters from interior drainages into coastal watersheds, such as from Chilko River into Klinaklini River.
Overall, while the trout show little variation within populations, there is substantial variation between most populations. Population patterns also differ among watersheds. In some cases, adjacent populations are fairly distinct, indicating they rarely mix. This is the situation with bull trout in Birkenhead Lake and in Phelix Creek which flows into the lake.
In contrast, upper Pitt River and Chilliwack Lake bull trout populations lack differentiation. Recreational fish catches reveal these stocks mingle in the lower Fraser River. Nine out of ten bull trout landed from the Fraser below New Westminster come from Pitt River, with about 5 percent originating from each of the Chilliwack and Ryan Rivers.
Eric B. Taylor and A.B. Costello. 2006. Microsatellite DNA analysis of coastal populations of bull trout (Salvelinus confluentus) in British Columbia: zoogeographic implications and its application to recreational fishery management. Canadian Journal of Fisheries and Aquatic Sciences. 63(5): 1157-1171.