Lake trout in the Upper Great Lakes

The Ministry of Natural Resources assesses the state of lake trout populations in the upper Great Lakes by reviewing harvest information and monitoring commercial fish harvests through onboard catch sampling.  Annual standardized netting surveys provide data to compare trends in lake trout abundance from various locations over time.  In both upper Great Lakes, assessment activities are also undertaken by U.S. state, federal, and First Nation governments.
 

Photo: Arunas Liskauskas.

Research also plays a role in lake trout rehabilitation. Declining lake levels, shoreline development, invasive species, commercial and recreational fishing, and ongoing sea lamprey predation all continue to impact lake trout.  The Ontario Ministry of Natural Resources is committed to gathering the best available science and information to help address these concerns. Research projects in the upper Great lakes have assessed population structure, recovery of wild populations, and are investigating stock structure of siscowet lake trout.

Lake Huron
The abundance of adult lake trout has been increasing in the main basin of Lake Huron since 1998. Some of this increase can be attributed to successful sea lamprey control efforts in the St. Marys River. Restrictions on lake trout harvest in U.S. waters have also contributed to lake trout’s recovery.

Additionally, in recent years there has been a shift in the prey fish community of Lake Huron back to a more natural state.  Alewife, an invasive species, has significantly declined, allowing for increased numbers of lake cisco in some locations.  The decline in alewife is important as a diet rich in alewife causes thiamine deficiency syndrome.  This affliction does not occur with a diet comprised of native prey fish such as lake cisco.

In Georgian Bay, the rehabilitation of lake trout populations has met with variable success.  

The most significant development is the successful rehabilitation of lake trout in Parry Sound.  This population of lake trout represented one of only two native lake trout populations in Lake Huron that survived lamprey predation and overfishing.  A recovery program that included a combination of stocking and strict harvest controls, implemented by the Ontario Ministry of Natural Resources and local stakeholders, has allowed the population to recover to historic levels of abundance.

Signs of rehabilitation are less obvious in Iroquois Bay, the other historic lake trout population that survived in Lake Huron.  In spite of ongoing stocking and strict regulations controlling recreational angler harvest, population levels remain low.

In other parts of Georgian Bay, recent trends indicate declining abundance, particularly in southern Georgian Bay.  Assessment is being done to determine the reasons for the decline and then develop appropriate measures to reverse the trend.

Lake Superior
After decades of restoration work, self-sustaining populations of lake trout have been established throughout all of Lake Superior with the exception of the east end.  Lake trout abundance has reached pre-1940 levels in the remainder of the lake. Cooperation among agencies around the lake in terms of stocking programs, sea lamprey control measures, limits on sport and commercial fishing, and habitat protection and enhancement have been effective in spurring the recovery of lake trout in Lake Superior.  Restoration has now reached the stage where stocking is no longer needed in most areas of the lake, and some lake trout commercial fisheries are being re-opened.  The return of self-sustaining lake trout populations in Lake Superior is a coordinated management success story.  

Although the rehabilitation of lake trout has proven to be a long and difficult process, some success has been achieved in re-establishing spawning stocks and reproduction.  

The collapse of alewives in Lake Huron has clarified that consumption of early life stages of native species such as lake trout by alewives was a major problem.  Their decline has relieved lake trout populations of this impediment and the collapse of alewives therefore provides an opportunity to build on the accomplishments achieved to date.

The successful rehabilitation of lake trout in Lake Superior is proof that the rehabilitation of this native species in the Great Lakes is an attainable goal.

What the public can do to help

• Respect current fishing regulations for lake trout (ontario.ca/fishing)
• Help prevent the spread of aquatic invasive species (ontario.ca/invasivespecies)
• Protect fish habitat (http://www.dfo-mpo.gc.ca/regions/central/pub/habitat-on/pdf/habitat-on_e.pdf)
• Get involved with fisheries projects through the Ontario Stewardship program (ontariostewardship.org) and the Community Fisheries and Wildlife Involvement Program (ontario.ca/fishing)
• Help MNR develop fisheries management strategies through Fisheries Management Zone Councils. (ontario.ca/fishing)