Terms of Reference

Advice on up-stream passage for Lake Sturgeon at Pointe du Bois Generating Station (Winnipeg River)

Regional Advisory Meeting (Central and Arctic)

Freshwater Institute, Winnipeg, Manitoba
22 October 2009 10:30 a.m. to 4:30 p.m. (Central Daylight Time)

Chairperson: Tom Pratt

Background

Manitoba Hydro is considering modernizing the Pointe du Bois Generating Station (GS) on the Winnipeg River, which could involve constructing a completely new station (i.e., new power house, dam, and spillway) and decommissioning the old structures. The existing station was built in 1910 and was the first such station on the Winnipeg River. The Winnipeg River is much more fragmented today than it was a century ago when the Pointe du Bois GS was the only man-made blockage to upstream passage on the river. Now, there are eight hydroelectric dams along the river, two in Ontario and six in Manitoba resulting in fragmentation of fish habitat. There is currently no upstream fish passage at the existing station, although fish passage at the new station can be required by Fisheries and Oceans Canada (DFO) under Section 20 of the Fisheries Act, if deemed necessary.

It is unknown whether there was any natural fish passage at the Pointe du Bois falls before the current station was built. The falls themselves are about 34 feet high and consist of a series of rock shelves and pools, so it may have been historically possible for fish to move upstream during high flows and traditional knowledge seems to indicate that upstream passage was possible at this site. Downstream fish passage at the site was and is possible, although it is more dangerous now for fish that pass through the turbines. A new station design might call for more water to flow through the turbines than over the spillway, compared to the current arrangement.

In November 2006, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed the Winnipeg River - English River Lake Sturgeon (Acipenser fulvescens) populations and designated them as Endangered. COSEWIC considered historical threats to have been primarily overexploitation for these Lake Sturgeon populations but dams and poaching are the most important current threats (COSEWIC 2006). The section of the Winnipeg River from Pointe du Bois downstream to Slave Falls is known to have the most abundant population of Lake Sturgeon in the Winnipeg River. This may be due in part to the availability of good spawning sites in the area. Currently Sturgeon are known to spawn at the base of the Pointe du Bois falls and at the outlet of the existing powerhouse. Both the availability and quality of spawning sites could change with a new station design due to the decommissioning of the existing powerhouse, the placement of the new spillway, and a change in the flow regime which might restrict flow width over the falls and direct more of the flow through the turbines than through the spillway. This could negatively impact the current spawning success of Lake Sturgeon in this reach of the river.

If Manitoba Hydro modernizes the Pointe du Bois GS, DFO may be required to make several regulatory decisions regarding the proposed changes to the GS, including whether Manitoba Hydro will be required to construct upstream fish passage facilities at the new Pointe du Bois GS. Potential benefits or negative consequences of upstream Lake Sturgeon passage at this site should be considered in light of the sources of uncertainty and the level of risk given this uncertainty. While monitoring and adaptive management can be required to determine whether mitigations have been effective, it would be problematic and ineffective for DFO to ask for inclusion of fish passage after the station is built. The advice provided by Science may be considered in other Habitat Management reviews of future upgrades to Manitoba Hydro stations on the Winnipeg River system and possibly to reviews of other upcoming Manitoba Hydro projects on the Nelson River, Churchill River, and Burntwood River systems.

Objectives

DFO Habitat Management has requested advice from Science on whether upstream passage at the Pointe du Bois GS would be beneficial or detrimental to the sturgeon population in the Winnipeg River given, 1) the potential negative impacts of the proposed new structures on sturgeon spawning habitat below Pointe du Bois, 2) the overall status of sturgeon in the Winnipeg River, and 3) the uncertainty surrounding the quality of habitat upstream of Pointe du Bois. If it is not possible to answer this question given the current state of knowledge, what would be the relative levels of risk to Lake Sturgeon populations in the Winnipeg River of asking for upstream passage when it is not necessary/desirable and of not asking for upstream passage when it is necessary/desirable?

Products

The Regional Advisory meeting will generate a proceedings report summarizing the deliberations of the participants. This will be published in the Canadian Science Advisory Secretariat (CSAS) Proceedings Series on the CSAS website. Also, the advice from the meeting will be published as a Science Advisory Report.

Participation

DFO, provincial governments, academia, industry and aboriginal experts are invited to this meeting.