Peace Reach Lake Trout movements
This project is year four of a multi-year project to study Lake Trout movements in the Peace Reach. In 2019, data from year three will be analyzed and survey work will occur near the Wicked River to identify potential Lake Trout spawning sites at this location. Movements of adult Lake Trout in Williston Reservoir were monitored in the past by using acoustic transmitters and data-logging receivers, stationed in the Peace, Finlay, and Parsnip reaches. Data suggest Williston Reservoir Lake Trout are a single, wide-ranging population that moves extensively within and beyond the Peace Reach, and concentrate in the vicinity of the Wicked River during the October spawning period.
Update: Nearly a million detections provide insight into the movements of lake trout in Williston Reservoir
A four-year, FWCP-funded project on lake trout in the Williston Reservoir is now complete and the outcomes give us more insight into the behaviour and movements of lake trout in the reservoir, which until now were largely unknown. However, more work is still needed which is why we have developed new priority actions related to lake trout in our updated Rivers, Lakes and Reservoirs Action Plan. The action plan identifies priority actions eligible for FWCP funding and will guide our funding decisions for the next five years.
The project, led by Diversified Environmental Services in collaboration with Carleton University, aimed to better understand reproductive behaviour and movement of lake trout, and potential interactions they may have with the provincially Blue-listed (vulnerable) bull trout. This information can then be used to inform conservation and management actions for the species.
With the creation of the Williston Reservoir, the previous riverine habitat changed to a large, deep, cold body of water and lake trout thrive in this type of habitat. Populations of lake trout may be increasing as a result, and may be competing with, or impacting, other species.
In natural systems, they typically spawn in the fall on cobble shoals and shorelines, however, in the reservoir, water levels may fluctuate up to 17 metres, preventing lake trout from doing so. The project discovered that lake trout don’t have a problem spawning well below the reservoir’s drawdown zone. Sixty adult lake trout, mostly in the Peace Reach of Williston Reservoir, were captured and implanted with acoustic transmitters as part of the project, and their movements were recorded by fixed acoustic hydrophone receivers, resulting in more than 917,000 detections.
The results indicate that Peace Reach adults made seasonal movements to the west end of the reach during early to mid-summer, and back again in the fall. A preliminary analysis also suggests that bull trout generally occupy shallower depths than lake trout. This may indicate that bull trout are being excluded from deeper water by the presence of lake trout, or that the two species are selecting different habitats. More work is planned—and forgive the pun—to dive deeper into this question and further data is expected to become available in 2021.
Final report: executive summary
The formation of the Williston Reservoir resulted in large-scale habitat changes in the upper Peace watershed due to a shift from a riverine to reservoir environment. In response, changes in the composition of the fish community occurred and some species, such as Kokanee and Lake Trout, have increased in abundance. Throughout the range of Bull Trout, the expansion of Lake Trout is generally regarded as a potential threat. A lack of life history information with respect to the status, population trend, and reproductive cycle of Lake Trout in Williston Reservoir has limited the understanding of interactions between the two char species and impeded the future implementation of appropriate management and conservation measures. Research actions directed towards understanding these issues are specifically identified by the Peace Basin Reservoirs Action Plan (Action 1a-1, FWCP 2014).
Click the provincial database link below to read the full final report for this project.