Brook trout are among the most attractive freshwater fish in the Northeast and a favorite target of anglers in the region. Vermont state fisheries biologist Jud Kratzer said they look “like a work of art.” But increasing temperatures due to climate change is a concern for their populations because they prefer cold, forested streams. They are declining precipitously in the southern extent of their native range in the eastern United States, and many anglers worry that the fish are imperiled in northern New England and New York as well.
That doesn’t seem to be the case, however, in Vermont. A study comparing data from a survey of 153 Vermont stream sites conducted from 2005 to 2016 to similar data from the 1950s found more trout in the 2000s. According to Kratzer, 710 brook trout per mile were recorded in the 1950s, while 1,121 trout were detected per mile in the same streams in the 2000s. Adult trout numbers were about the same between the two periods, but trout in their first year of life were way up.
“We speculate that it has to do with improving water quality and habitat,” said Kratzer. “The 1950s were before the Clean Water Act, when not much was being done to protect water quality and stream habitat. The state has also become much more reforested since the ’50s, and that probably contributed, too.”
The surveyors – James McMartin in the 1950s and Rich Kern in the 2000s – also counted non-native brown trout and rainbow trout, species that were introduced for fishing but that are known to outcompete and displace native brook trout, particularly in warmer streams.
“We thought we might see evidence of brown trout and rainbow trout causing problems for brook trout, but we were surprised to find fewer sites in the 2000s that had brown and rainbow trout than in the ’50s,” Kratzer said. “We found no evidence that the non-native species were impacting brook trout abundance.”
While the results are a good sign for brook trout in Vermont and suggest that management efforts have been successful, Kratzer said that comparing today’s trout numbers to the 1950s doesn’t necessarily mean that managers and fishermen can rest easy.
“We don’t really know what things were like before the ’50s, but it’s safe to assume that things were different before we settled the area and cleared the land and disrupted our streams,” he said. “There were probably better conditions for brook trout back then. So while our findings are encouraging, there’s still room for improvement.”
He noted that previous studies found that water temperature and the availability of woody material in streams are the primary factors affecting brook trout populations. Climate change will likely continue to increase stream temperatures, so protecting habitat and restoring streams by adding woody material will be vital to the future health of brook trout populations.
“People tend to remove fallen trees from streams, but those trees are important as trout habitat,” Kratzer said. “We need to change the culture about woody debris in the water so we’re protecting the habitat in the way that’s most effective.”