November 15th, 2013 by

Fishing is a fond memory for many of us, whether you spent childhood summers fishing with friends, or enjoy bonding with your children or grandchildren on fishing trips. Fishing for many in the American West means one thing: trout. The trout is iconic in this region, especially in Montana, where the cutthroat trout is the official state fish. The trout, native to the American West and prized by fisherman for its mild, earthy taste and by state governments for the income it generates (about $250 million per year in Montana alone), finds itself seriously threatened by climate change.

Cutthroat trout, the state fish of Montana. Credit: USFWS Mountain Prairie.

Climate change has not only warmed the water in the streams where the trout lives, but also caused droughts and reduced snow in the winter, negatively affecting water flow in the spring, making it harder for trout to move. In order to better understand the specific effects that climate change is having on trout in the west, scientists are using electric currents to catch and, subsequently, track the cutthroat trout, native to the northern Rockies region of Montana, with small transmitters known as pit tags. Brad Shepard of the Wildlife Conservation Society explains that the electric current is used as an attraction device to make the fish easier to net, telling NPR that the current “actually draws fish.” Scientists catch the fish, insert the trackers and release the trout back into the streams, beginning a years-long tracking process. Finding these trackers sometimes takes scientists off the beaten track; they have been found anywhere from marten dens to the freezers of local fishermen. Scientists are looking to follow the lives of these fish, determining growth and mortality rates, as well as time and cause of death. This data is collected and analyzed to determine any correlation to changes in stream flow and water temperature, to see if these factors affect the trout in a significant way. These factors really affect the trout, cueing “when they spawn, when they hatch, when they emerge, when they come out, how fast they grow, where they go,” as Shepard tells NPR. “But as you shift things in one direction, you can, in fact, lose part of the population.”

It will take time to fully understand the effects that lessened stream flow and higher water temperature have on cutthroat trout, but early emerging trends suggest that non-native fish, such as the rainbow trout, are moving further upstream, which previously was too cold for that species, into the cutthroat trout’s range. As the two trout species mix, rapid hybridization occurs, resulting in a marked decrease in trout fitness. This new, weaker trout becomes prey for fish, such as bass, which are moving into trout habitat that was once too cold for them. Climate change poses and new and serious threat to this iconic fish of the American West, and measures must be taken now, at the first sign of trouble to ensure its survival.