The Fall Colors (and Travels) of Wild Trout

If you gaze deep into a clear, cold brook this week, you may glimpse fish whose autumn colors put those colorful October leaves to shame! When Eastern Brook Trout spawn in mid-October, their coloration is particularly vibrant.

“Brookies” sport slightly-forked, nearly-square tails, white leading edges on orange fins, dark worm-like markings called “vermiculations” on their olive-green backs and bright red dots with blue halos along their glistening flanks. During spawning when eggs are fertilized externally in gravel depressions called “redds,” males develop a hooked jaw called a “kype” and exhibit aggressive territorial behavior.

In 2005, NH fisheries biologist, Diane Timmins surgically-inserted tiny radio transmitters into bellies of wild brook trout to track their seasonal travels. Contrary to conventional wisdom that “Brookies” occupy a limited home range of less than 5 miles, her research revealed a champion male trout traveled more than 50 miles before returning to its home pool in a North Country stream.

Fish biologists cite a range of environmental conditions that trigger trout travel. Summer water temperatures were a key factor governing fish movement. Trout also sought deeper water in winter to avoid ice scouring.

While biologists do not fully understand the mechanism wild trout use to navigate such long distance journeys, there seems to be a “home stream” natal response. Watershed connections and removal of obstacles to fish passage are critical to the continuity of ancestral travel routes and to seasonal congregations of our state’s remaining native Brook Trout.