Climate Change May Mean Fewer Fallen Trees For Fish To Use As Shelter

A Wisconsin study says climate change could hurt the ability of fish to benefit from trees that have fallen into the water.

Dead trees in lakes serve as good habitat for fish, and often lead to the growth of algae and insects the fish consume. Scientists monitoring Little Rock Lake in northern Wisconsin during the previous decade found dropping water levels put 75 percent of the woody habitat out of reach for fish.

University of Wisconsin-Madison researcher Jereme Gaeta said the lake’s perch population went down because those fish lost their hiding places and largemouth bass ate them. Eventually, the bass population dropped too.

Gaeta said if climate change continues to mean less precipitation and more evaporation, it will take a long time for enough trees to fall in the water at the right angle and depth.

“If lake levels go down and stay down, we’re talking about a process that’s at least several hundred years — if not a millennia — to catch things up to how they used to be,” said Gaeta.

Gaeta said water levels in Little Rock Lake are back up over the last few years, but fish numbers might not rise accordingly. Gaeta also said over the long term, more Wisconsin lake owner associations may have to consider dropping wood into shoreline waters, to maintain a diverse fish population.

The UW research is published online in Canadian Journal of Fisheries and Aquatic Sciences.