ENVIRONMENT YUKON






 

Fish

Sustainability of lake trout fisheries

 

Significance

 

The health of lake trout populations reflect the general health of an aquatic ecosystem due to the species’s:
  • slow growth,
  • position at the top of the aquatic food chain, and
  • reliance on healthy and clean habitats.

As an indicator species, monitoring the sustainability of lake trout populations can provide valuable information about the ecosystem. This species is also highly valued in Yukon fisheries. Monitoring the harvest data and calculating the optimal sustainable yield for each lake informs management decisions such as changes to catch and possession limits.

 

Profile

Seasonal lake trout movement – Southern Lakes

 

 

Lake trout move throughout the Southern Lakes system in Yukon and British Columbia. As trout are a very important species in an aquatic environment and many Yukoners rely on trout as a food source, the Government of Yukon's Department of Environment Fish and Wildlife Branch is working to understand how trout use these lakes.

Through this multi-year project, the department is studying annual migration patterns between each lake. By determining the origin, destination and timing of lake trout movements and linking this to genetic information, department biologists and managers can understand the effects of harvest on lake trout, allowing more effective harvest management within the region.

As of 2016, the third year of the project, researchers have placed 18 receiver stations around the lake system and have deployed 163 transmitters in lake trout. Additionally, six receivers and 1556 transmitters were deployed in Atlin Lake in collaboration with the B.C. Ministry of Forest, Lands and Natural Resource Operations and the Taku River Tlingit First Nation.

As of June 2016, the project had gathered approximately 7.2 million unique lake trout relocations, not including Atlin Lake. The department has also collected genetic samples from 971 lake trout throughout the Southern Lakes system through netting assessments, angler harvest surveys and volunteer angler submissions.

The data are revealing that lake trout move extensively between lakes in this system and can travel long distances in short periods of time. In one case, a lake trout moved from Bennett Lake to Tutshi Narrows—a distance of 80 km—in 3.5 days. The data are also showing that male lake trout are returning to spawning locations the year after they were captured. This movement pattern suggests these lake trout are using traditional spawning areas.

Work on lake trout movement and genetics in the Southern Lakes will continue for another few years and will contribute to the sustainable management of lake trout in this important lake system.

See the Fish and Wildlife Branch Highlights http://www.env.gov.yk.ca/
publications-maps/plansreports.php#fw_branch
for more information.

 

What is happening?

Recreational harvest data are available for the lakes in Yukon where the most intensive fishing activity takes place. Fisheries on other lakes are expected to be within sustainable levels, due to low fishing activity. Generally, small lakes are more vulnerable to overharvesting because of their smaller lake trout populations and lower sustainable yields.

Harvest of fish is considered to be unsustainable when it exceeds the “optimal sustainable yield.” Overharvested populations will decline and fishing will become poor if no management action is taken.

 

Figure 1: Sustainability of angler harvest on select Yukon lake trout populations based on most recentangler harvest data up to 2015.
Source: Environment Yukon

 

In 2015,
  • The majority of the recreational lake trout harvest in Yukon was sustainable, with most water bodies maintaining quality fisheries.
  • Lake trout harvest in Fox, Caribou, Fish and Tarfu lakes exceeded sustainable limits according to most recent angler harvest data.
  • In some cases, harvest may appear to be sustainable when, in fact, a lake trout population has been depleted. For example, while the lake trout harvest in Braeburn, Snafu, Frenchman, Pine and Ethel lakes is below the sustainable threshold, it may prove unsustainable because these lake trout populations appear to be depleted.

 

Capturing lake trout in gill nets to estimate their density and abundance.

 

 

Taking action

  • Based on 2014 recommendations by the Yukon Fish and Wildlife Management Board, regulation changes for Snafu, Tarfu, and Pine lakes came into effect April 1, 2015. These changes reduced the catch and possession limits for trout, and should result in no recreational (licenced) harvest of lake trout from these lakes. An evaluation of these changes are planned for future years.
  • The Yukon Fish and Wildlife Management Board have recommended regulation changes for Fox, Frenchman, Kusawa, and Twin lakes. The changes would reduce catch and possession limits for lake trout in order to: maintain a sustainable fishery in Kusawa Lake; and, to allow the depleted populations in Fox, Frenchman, and Twin lakes to recover. These regulation changes are not yet in effect.
  • In 2016, the Department of Environment's Fish and Wildlife Branch performed lake trout and lake whitefish population assessments at five lakes; burbot population assessments at two lakes; and, performed Angler Harvest Surveys at nine lakes and rivers. Data from these surveys are currently being analyzed.

 

Data quality

  • The optimal sustainable yield is derived from a model based on physical and chemical parameters of the lake, such as temperature and nutrient content. To be sustainable, harvest levels must not exceed the optimal yield.