Originally published in Lake of the Woods Area News, Volume 55, Number 1, Early Spring 2025
If ever there was a “high needs fish”, it is the lake trout. They are particular about where they spawn and especially fussy where they live.
In the Kenora area, lake trout spawn early to mid-October with diminishing light and water temperature. Spawning occurs over clean broken rocks or cobble on shorelines or shoals exposed to wave action. Fertilized eggs are broadcast over rocks falling between cracks called interstitial spaces. These spaces provide protection from predators but must be clean of sediment and debris or the eggs will suffocate. Larvae grow slowly during winter hatching in late February or March, remaining in the rocks for an additional few weeks living off their yolk sac until their fins fully develop.
Threats to the lake trout populations
Lake trout are found only in deep, cold, oxygen rich waters that are nutrient poor (oligotrophic lakes). They are the aquatic equivalent to “the canary in the coal mine” and are extremely vulnerable to water quality changes and overfishing. If their numbers decrease, it usually can be attributed to one or both stressors.
From 1984 to 1987, the Ministry of Natural Resources (MNR) conducted studies in the north end of Lake of the Woods where lake trout reside—Clearwater Bay, Echo Bay and Cul de Sac. These included assessments of harvest, water quality and spawning habitat. Findings revealed lake trout were being over harvested during the winter fishery; reduced oxygen levels; and higher than normal nutrient levels in Clearwater and Echo Bays. It was suggested changes in water quality were caused by run off from septic fields, lawns and gardens.
Protective measures and monitoring
To protect and rehabilitate the existing lake trout population and water quality, the Restricted Area Order (RAO) and angling regulations were implemented in 1988. The intent of the order is to ensure additional development on private lands will not negatively impact water quality and lake trout habitat. Angling regulations included closing the winter fishery; restricting the harvest to a maximum of 110 trout; and gear restrictions.
For the next 10 years, in what I like to call the “golden age of RAO monitoring”, numerous studies were conducted. These included MNR’s standard assessment of water quality and fisheries but also involved volunteers in citizen science projects.
High school students played an integral part in the Spring Littoral Index Netting (SLIN) projects (1995, 1996, 1997, 2001). Small mesh nets were set in the spring for brief time periods capturing trout by their teeth. Once sampled for length, weight, age and tagged, all trout were released unharmed. The most innovative program recruited volunteer scuba divers to identify, map and assess lake trout spawning habitat. These underwater surveys (1994, 1995, 1996, 2001) are the largest of their type ever conducted in North America. Up to 60 divers with over 60 surface support personnel were involved.
In 2001, MNR met with various stakeholders to review the results of past monitoring programs; identify future work directions; and identify volunteer partnership opportunities. Water quality results from 1980, 1994 and 1997 showed considerable variability, confirming the need for greater frequency of monitoring. Total dissolved solids, nutrient levels and water transparency were atypical and outside the Provincial average for lake trout waters.
SLIN provided valuable insights regarding the status of lake trout in each of the basins. Compared to the Provincial summary of 84 lake trout lakes, Clearwater Bay and Cul de Sac trout populations were considered healthy and in good condition. Overall abundance was high with representation of both young and older year classes and mortality (20 per cent) was well below the maximum allowable mortality of 30 per cent. In contrast, the low abundance and erratic or missing year classes signalled concerns for the Echo Bay and Granite Lake populations. Although mortality was within an acceptable level, the populations were dominated by a small number of older adults and did not compare well to other lakes.
The recommendations were to hold the course in Clearwater Bay and Cul de Sac and continue monitoring water quality and populations. Increased monitoring of summer lake trout habitat (dissolved oxygen/temperature profiles) were recommended for Echo Bay and Granite Lake and possibly include Granite Lake in the tag or restricted harvest program.
The underwater surveys generated the most interest within the scientific community and some of the most valuable results. Traditionally scuba divers, particularly volunteer divers—like me—have seldom been used in freshwater assessments. The underwater surveys conducted in the RAO demonstrated the usefulness of this technique. Results of these surveys and a video “Beneath the Surface” were presented at the Second Lake Trout Symposium (Yellowknife, NWT) and the 138th American Fisheries Society Annual Meeting (Ottawa, Ontario).
Identifying known and unknown risks
Over 30 spawning locations were identified, mapped and assessed. Most eggs were found in depths ranging from 0.5–2 m on rocky wave-washed shorelines adjacent to deep water. The divers also discovered eggs in areas never documented before—narrow ledges adjacent to vertical cliffs e.g. McCallum Point. The underwater surveys confirmed shoreline alterations and developments (docks, boathouses, etc.) negatively impacted lake trout spawning habitat by directly covering spawning substrate or blocking the cleansing effect of wave action resulting in sediment and debris degrading the substrate.
The most intriguing discovery was a band of benthic algae resembling “quiche” found at 6–7 m depth but occasionally extending into the shallows in front of some cottages. Analysis of the algae confirmed it was a blue-green algae dependent on an external source of nitrogen to exist. The nitrogen source was not confirmed, but septic leakage was highly suspected.
Looking for more answers—for the present and future
Fast forward to the present or 35 years post regulations. Are water quality and lake trout populations in the RAO better, the same or worse? Unfortunately, MNR and MOE were unable to provide a definitive answer. The MNR no longer conducts lake trout assessments in the RAO. Instead, they rely on lake wide monitoring of large-bodied fish communities in Lake of the Woods using the North American netting standard and Broadscale Monitoring as their primary assessment tools. Although effective in monitoring some fish communities, these techniques captured few lake trout and MNR was unable to comment on the present status of lake trout in RAO.
However, Kenora District MNR conducted spawning population assessments in Clearwater Bay, Echo Bay and Cul de Sac in 2021 and 2022. Their results indicated mature spawning trout up to 20 years, but a clear trend in population size was not apparent. No information regarding recruitment of young trout or status of spawning habitat was available.
Ministry of the Environment, Conservation and Parks (MOE) analyzed water quality samples taken by MNR in the RAO from 2003 to 2018, but this program has since been discontinued. The most important finding indicates no evidence of increased total phosphorous or chlorophyll A across the multiple bays sampled in the RAO. I was unable to determine if long term records of dissolved oxygen/temperature profiles are available for the RAO. This would provide critical information regarding the amount of summer lake trout habitat available within the RAO basins.
With no MNR or MOE programs dedicated to RAO waters, this may be the opportune time for citizen science to partner with these agencies and take the lead. For example, with a minimum amount of training and equipment, volunteers could monitor lake tout summer habitat (dissolves oxygen/temperature profiles).
Maybe a graduate student or two could be enticed to solve the mystery of the benthic algae band. They may be getting a “little long in the tooth,” but there is a crack team of volunteer divers ready to help.
