Why Habitat Matters to Brook Trout

Fishing Regulations Vermont Freshwater Fishing


Why Habitat Really Matters to the Wild Brook Trout (and why they’re so small)

There are many waterfalls and cascades that are only enjoyed by the rare few that venture off road in search
of wilderness brook trout.

Depth and cover are important for brook trout because of the second most defining characteristic of brook trout biology, namely that it is really hard to be a brook trout.

Because of the brook trout’s all-important need for cold water, they are often limited to relatively small, shallow streams. At least, that is the case in much of Vermont. Living in small, shallow streams is difficult for several reasons. Fish in tight quarters are easier targets for predators like mink, otters, herons, and kingfishers. It can be especially easy for predators during summer droughts when brook trout are forced to congregate in the relatively few deep pools or at cold spring seeps. Winter can be even more difficult as brook trout find themselves squeezed into even tighter quarters by ice sheets that can take up most of the water column.

This hard life is why stream-dwelling brook trout tend to be small. They only reach trophy proportions in ponds and larger rivers where they have adequate cold water, depth, and food to allow for multiple year survival and fast growth. In their more typical small stream habitat, they have a high mortality rate, which means that each fish has a very high likelihood of dying of natural causes each year. In Vermont streams, approximately 90% of brook trout are less than 6 inches long, which roughly corresponds to 2 years of age. This is true even in streams that see little or no fishing effort. They don’t have time to grow to large sizes, but they don’t need to because they mature early, with some brook trout able to reproduce at age one and nearly all reproducing by age two. They are also prolific spawners, keeping the streams well-stocked with the next generation. The brook trout’s high mortality and reproductive rates mean that anglers should feel good about keeping some fish for the table, especially on lightly fished back-country streams. If anglers don’t harvest them, predators or Old Man Winter surely will.