Results from a 15-year study of factors affecting population levels of Eastern brook trout in the face of climate change show that high summer air temperatures have a large influence, in particular on the smallest fry and eggs, which are most important to wild trout abundance in streams.
Co-author Ben Letcher, fisheries biologist at the U.S. Geological Survey and adjunct faculty in environmental conservation at the University of Massachusetts Amherst, says, "It took years of sampling four streams and tracking more than 15,000 individual fish, but we feel we can account for about 90 percent of the yearly variation in abundance. The bottom line is that high summer temperatures are bad. That is unfortunate because summer air temperature is expected to increase with climate change and extreme rain is also expected to increase, especially in the spring when vulnerable eggs are hatching and fry are emerging."
"Those two things are heading in the wrong direction for this particular species," he adds. Letcher and his colleagues predict that if climate warming proceeds as projected and the trout don't evolve, in as soon as 15 years these sentinel fish of cold water streams could be gone from the study stream. "If they can evolve, they may at least double their ability to stay in the stream," he notes.