U researchers take to icy streams to study insect-trout link

Taking to icy trout streams across Minnesota in search of tiny mosquito-like insects isnâÄôt on most to-do lists, but University of Minnesota entomology professor Leonard Ferrington and a team of researchers brave the Minnesota winter nearly every weekend doing just that. This past weekend, Ferrington and his team waded through Hay Creek in southeast Minnesota and searched in the snow for non-biting midges âÄî tiny insects that are a key source of food for trout in the winter. Ferrington is the first researcher to examine these cold-hardy bugs and their effects on Minnesota trout streams. According to Mark Ebbers , a trout and salmon program consultant for the Minnesota Department of Natural Resources, 92,000 people bought trout stamps in 2007, making them eligible to fish for trout. In addition to the recreational aspects of trout fishing, Ebbers said the trout fishing industry generates revenue for communities around the streams. There are nearly 600 trout streams scattered throughout Minnesota, and trout remain active during the winter, Ferrington said. With the cold weather, however, the food supply for trout can vary, affecting the weight and health of the fish. âÄúWeâÄôre trying to figure out why thereâÄôs such a disparity in growth and weight in trout in the winter,âÄù Ferrington said. âÄúObviously itâÄôs related, we think, to the kind of organisms they eat.âÄù In the winter, the trout feast on the non-biting midges Ferrington and his team spend weekends collecting. The midges are uniquely adapted for the cold, Ferrington said, surviving in temperatures as low as 7 degrees below zero. âÄúWe have discovered in the trout streams there are some very cold-adapted insects that actually only grow in the winter time,âÄù Ferrington said. âÄúMost insects donâÄôt do that.âÄù The midges have a unique antifreeze-like chemical in their tissue, and Ferrington is investigating how they evolved this mechanism, in addition to his research involving trout streams. By examining the habitats midges live in âÄî usually rocks or sand âÄîand how their abundance affects the trout, Ferrington said his research can eventually be used to better manage the streams. âÄúIf we want to increase their abundance, in a management sense we can add rocks or take rocks out,âÄù he said. As part of their research, Ferrington and his team venture out in frigid temperatures to sample different trout streams from around the state, measuring the size of the trout, the amount of midges in and around the stream and collecting midge samples for lab work. Back in the lab, entomology graduate student Brian Schuetz uses midges to create a simulated trout stream for research. Using small aquariums and refrigerators, Schuetz examines how quickly the midges mature in a cold environment. In addition to their importance to trout-stream ecosystems, Schuetz said the cold-hardy midges can also serve as indicators of climate change. âÄúSome of these uniquely adapted insects can be warning signs of shifts that we wonâÄôt be able to feel for decades,âÄù Schuetz said. âÄúJust a change by a couple of degrees could eliminate an insect from an area.âÄù Overall though, FerringtonâÄôs researchâÄôs greatest potential lies in the benefit that increased midge populations will have on trout streams across Minnesota. âÄúThese insects we think are really critical to the health of the trout,âÄù Ferrington said. âÄúThey are the major food resource.âÄù