Philip Lake Bull Trout Survey

In support of continued operation of the Mount Milligan Copper-Gold project, Mount Milligan proposed to withdraw water from Philip Lake in British Columbia. Before approval could be granted by the British Columbia Ministry of Forests, Lands, Natural Resource Operations, and Rural Development, Thompson Creek had to show that Philip Lake was not used by bull trout, a species of special concern in the province.

The investigation into bull trout presence in the lake was completed using two techniques: an environmental DNA (eDNA) survey of the lake and surrounding tributaries and a fall hoop-netting survey of the downstream creek during the bull trout spawning period. After capturing two adult bull trout from the Nation River, we sent the samples to our partners at the University of Guelph to build an eDNA profile. Over the course of a week, our team tested eight different sites for the presence of bull trout using eDNA: three in the lake, one in the creek, three positive control sites where bull trout were known to occur, and one negative control site in a fishless lake near the mine.

No bull trout DNA was identified from any of the samples collected from the lake, creek, or at the negative control site. The only positive sample was from one collected in the one of the three positive control sites, confirming that the primer was successful at detecting bull trout eDNA in the environment. With the absence of bull trout eDNA in the target area, combined with the absence of bull trout in the hoop-nets, Thompson Creek was able to reasonably demonstrate that their proposed water withdrawals would not detrimentally affect bull trout in Philip Lake.