Wednesday, March 27, 2024

Lake Superor's Lake Trout

Environmental & Science Education, STEM, Behavior, Biodiversity, Biological Evolution, Global Change, Climate Change

Ed Hessler

I point you to an article in the Minnesota Conservation Volunteer (March - April) and borrow from the story along the way. 

Mysterious Whoppers is by Chris Pascone and if you get the Volunteer you can read it there; otherwise it is on the Web site for the Volunteer although not laid out as well or the the photographs inserted in the text. 
The whoppers in question are all lake trout, a single species (Salvelinus mamaycush) but one which Pascone refers to as "shape-shifting." Currently there are four known morphotypes, also referred to as "morphs"- shape shifters. 

First a few comments about the climatology of Lake Superior Many factors are at work as you will learn in this release from the University of Michigan (n.d..). I chose it for its comprehensiveness. But when we focus on lake trout, I found Pascone's blunt statement on one climatic feature edifying: "How is global warming affecting cold-water lake trout" Under study."

First to the lake trout (Salvelinus mamaycush). These fish "fill" the lake from top (about 300' below the surface) to bottom although little is known about their distribution and abundance.

--Humpers. These are the least common. The name is "for a physical feature...--the tops of large seamounts, or humps, that rise from the depths of Lake Superior to heights that approach the surface, the habitat it prefers.

--Redfins. Photo showing fin color, "The colorful fins...give it its moniker." There are three great photographs in the Volunteer article.

--Siscowet. This link includes photos, side by side of Siscowet, Humpers and Leans.

Gary Goldsworthy, the Minnesota DNR Lake Superior fisheries supervisor notes that "the morphotypes are a product of their habitat features such as depth and locations (population isolation).

You may also be interested in a section of the DNR Fisheries Management Plan For Lake Superior on tributary habitat which influences the lake variously.

Pascone summarizes the history of Lake Superior trout in a section titled "Back From The Brink." I was struck by an observation made by Shawn Sitar, a Michigan DNR research biologist who compared lake trout and Chinook salmon.

From an evolutionary point of view Lousie Chavarie of the Norwegian University of Life Sciences, provides some perspective. Pascone quotes a statement she made on the role such diversity plays on ecosystem resilience (''e.g., climate change"). One to add to your daybook.

The uniqueness of Lake Superior and their trout is pointed out by DNR's Gary Goldsworth. Grant Sorenson, the host of Superior Angling who also comments on some remaining mysteries. Pick any Sorenson video and you will be captured by his passion for fish. He puts it into words in the section About Us (from the Superior Angling Co.).  He loves fish and their habitat.

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