Wild Brook Trout
Still Thriving in Vermont's Coldwater Streams
By Jud Kratzer
Fisheries Biologist -Vermont Fish & Wildlife
Generations of anglers have enjoyed pursuing brook trout in the thousands of miles of coldwater streams that course throughout most of Vermont. A lot has changed in Vermont over the decades, but the brook trout is still one of state’s most beloved and iconic fish species. How have changes in climate, land use, water quality, and angling affected the state’s wild brook trout populations? An extensive dataset from the 1950s provides
a unique opportunity to answer this question, at least for the last half-century.
From 1952 to 1960, James MacMartin, a fisheries biologist with the then Vermont Fish and Game Department, used electrofishing equipment to sample fish populations at over 1,000 stream sites throughout the state. Electrofishing is a technique still used by fisheries biologists today to sample fish populations, and it involves the use of an electrical field to temporarily stun fish. MacMartin took detailed notes of his sampling efforts and locations, and these notes allowed fisheries biologists with today’s Vermont Fish & Wildlife Department to sample wild trout populations at 153 of these same sites from 2005 to 2016.
From the 1950s to the 2000s, wild brook trout abundance increased. This increase was driven by young-of-the-year brook trout, which are less than one year old. We don’t know why this increase occurred, but improvements in water quality and habitat may be contributing factors. Water quality has improved since the 1950s as a result of the Clean Water and Clean Air Acts of the early 1970s. Brook trout habitat has also likely improved as reforestation has continued to progress from the early 1900s. Healthy streamside forests are important for brook trout because the trees shade the stream and provide organic material (e.g., leaves), which provides food for invertebrates, which are food for trout. Trees that fall into the stream also provide important cover for brook trout and other fish species.
While it is encouraging to learn that brook trout populations in Vermont’s coldwater streams have been stable or increasing over the past half-century, there is still work to be done. Cold water and quality habitat are two of the most important factors for brook trout populations. The department continues to work at protecting and restoring streamside forests, which help to keep the water cool as well as provide valuable large woody habitat to streams. The department is also working to remove dams and culverts that prevent the free movement of brook trout to necessary habitats, including the cold water that they need to survive the summer.
While brook trout are thriving in the state’s small cold streams, they have been displaced from many of the state’s larger streams and from most of the ponds that once supported wild brook trout populations. Habitat has been slower to recover in most of Vermont’s larger streams, and the warmer temperatures of these streams are not favorable to brook trout. In most of the ponds that formerly supported wild brook trout populations, introduced fish species have displaced the native inhabitants. Although brook trout can grow abundant and large in ponds, they are poor competitors with warmwater fish species.
The Vermont Fish & Wildlife Department needs your help to ensure a robust future for the state’s wild brook trout. Do your part to support the protection and restoration of streamside forests, and when you see a tree fall into a stream, leave it there so it can provide habitat for brook trout and other aquatic species. Never introduce a fish species or other aquatic organism into a waterbody. Once introduced, these new species could have devastating consequences for brook trout and
other native species, and they may be impossible