Mackenzie River Chum Salmon: Clinging to or Colonizing the Top of the World?

The vast and remote Mackenzie River drainage represents the northern frontier for Chum Salmon (Oncorhynchus keta). Although present in low numbers, these fish are consistently harvested in the subsistence fisheries in the Canadian Western Arctic. Whether these fish represent consistent vagrancies or a self-sustaining fringe population, however, remains unknown. A long-term community-based monitoring program has recently identified an increased frequency of years with exceptionally higher levels of subsistence harvests compared to the more common years with low harvests. Tissues samples of Chum Salmon obtained from this program were analyzed using nuclear DNA markers to identify and develop knowledge regarding the potential origins of these fish and to investigate the genetic structure within the Mackenzie River. Preliminary results suggest that Chum Salmon harvested in the Mackenzie River monitoring program appear to be more closely genetically related to Kotzebue Sound populations and those in Siberia and the Russian Far East than to Yukon River populations of Chum Salmon. These analyses also provide evidence of genetic sub-structuring within the Mackenzie River. Implications regarding the historic or present-day origins of Chum Salmon harvested in the Mackenzie River will be discussed.