Fish Distribution across Trophic States

Different species of fish require different habitats and food sources for survival.  The figure below is a summary of fish distribution across lake trophic states for natural, unstocked lakes (figure adapted from The In-Fisherman Handbook of Fishing Knowledge).

Oligotrophic lakes are very low in nutrients and have low concentrations of plants and algae.  Their cold, high oxygenated water is suitable habitat for lake trout and whitefish/tullibee/cisco.  Whitefish live more toward the top of the lake, while lake trout live at the bottom of the lake and come to the top to feed on whitefish.  As lakes become mesotrophic, there are more nutrients available, more plants, and the water is warmer.  In mesotrophic lakes walleyes are the dominant species and smallmouth bass begin to establish.  The walleyes live in the deeper parts of the lake and prey upon other fish such as perch.  Smallmouth bass live in the shallower areas where there is plant cover.  Northern pike and muskellunge are the top predators, but they are present in much smaller numbers than walleye and smallmouth bass.  In eutrophic lakes more of the lake is occupied by plants, and open water fish such as walleye begin to disappear while fish associated with shallow water and plants become established.  Largemouth bass and sunfish are dominant in eutrophic lakes.  Once a lake becomes hypereutrophic, only rough fish such as carp can survive.


For descriptions and photos of Minnesota fish species, fish facts, fish diseases, fishing seasons, and fishing records visit: http://www.dnr.state.mn.us/fishing/index.html.