Lake Superior Lake Trout Depth and Temperature Study


depth and temp

GLIFWC staff placing a depth/temperature tag on a lake trout (namegos)


Chinamekos – lake trout – have long been a food source for the Anishinaabe people, and several tribes rely on the species for their commercial fishery. These swimmers thrive in the cold waters of Gichigami, preferring temperatures around 50 degrees Fahrenheit.


As part of its Climate Change Program, GLIFWC is studying how lake trout may be affected by warming lake temperatures and less winter ice cover. Less ice cover in winter means the open, dark blue water absorbs more heat (as opposed to an iced-over lake which reflects the light). This heat absorption of an ice-free lake gives the upper water layers a head start for further heating over the warm summer months, leading to a later ice cover the following year as the lake takes longer to cool down.


Through its Lake Trout Depth / Temperature project, GLIFWC is studying how the warming lake temperatures affect lake trout. Using archival tags, the study records the depths and temperatures where the fish travel. Generally, warmer water temperatures means the fish eat more food and grow faster. But warmer water temperatures might also result in the fish moving deeper to cooler waters, which could lead to changes in where the fish are located for harvest or changes in their diets if their prey fish do not also go deeper.


The study replicates an earlier project completed in 2003. When complete, it should demonstrate whether fish are now inhabiting warmer or deeper water than they did fifteen years ago. Whether the fish chose to remain in warmer water – and consume more food and grow faster – or whether they decide to head to deeper, colder waters. Their behavior could lead to changes in their harvest location and possibly their prey fish.


Although GLIFWC is not yet finished with the study, and data remains to be analyzed, it appears that lake trout have not significantly changed their behavior in response to warming lake temperatures. This means that more research is needed to understand how climate change and warming lake temperatures are affecting chinamekos.


To read more about the Climate Change Program’s Chinamekos study in Gichiigamii, go to Mazina’igan, GLIFWC’s quarterly newspaper:


“Research tracking laker habits in a warming Gichigami”