When you hook a brook trout you notice something: They are much larger than they look. And they are heavy for their size. Typically that’s because they have had plenty of opportunity to grow up in the best environments.
And because we all encounter brookies regularly fishing our home waters, most of us believe we can identify a healthy brookie by sight alone. But things aren’t always as simple as that, especially when it comes to brook trout. In fact, where these fish reside at night determine everything about their growth. A great breakdown explains the difference visually and why some days you’ll catch little fingerlings while other times you’re landing fat trophies.
Why Brook Trout Grow at Different Sizes
Habitat type and water temperature plays important roles here. Brook trout are not little lake trout, get it through your thick skull: They’re a different species. They’re char, which are cousins to salmon family, but they adapted to thrive in the clear, cooler headwater streams. Because they’re biologically programmed to prefer those conditions, they grow based off season. When the water gets into the ideal temperature range (approximately fifty-five degrees Fahrenheit), they’ll feed like crazy and grow quickly. But as the water temps rise above sixty-five degrees, they’ll begin to feel stressed out; they won’t eat much and will hold off until things cool down again. So that’s why you see some pale, thin brookies caught in shallow riffles in midsummer while plumper ones are tucked away in deeper, cold spring holes nearby.
Brook trout living in streams also have limited options as their habitat plays an important role; there’s little room to spread out, food is hard to come by, and battling currents eats up precious energy. As a result, they grow slowly, and on average, a six-year-old stream fish may only be twelve inches long. Survival, not explosive growth, is the name of the game. So how do you find good fish? Learn to read the water, seek out those unique areas where the current can ease enough to allow them to feed well.
Great Lakes tributary brook trout are quite different than their stream cousins. They have easy access to heavy concentrations of smelt, alewife and other baitfish throughout the year. There’s no need to fight swift current, as these brookies live much of their life in huge lakes with incredibly dense populations of food. For this reason, they develop at a fast rate relative to stream fish, and a seven year old coaster will be easily twice to three times larger than one of his stream born peers. This stark difference is highlighted by the chart above, which shows that the availability of good forage dramatic impacts their physical development.
Another interesting contrast comes from those who live on alpine lakes. While they have lots of room, this water can be right at freezing most of the year as a result of its high elevation and snowmelt. This results in incredibly slow growth for these fish. Low temperatures leads to a lower metabolism, which means less appetite. So you may come across brook trout here that are fifteen years old and only eight inches long. They look ancient despite their small size because each inch they’ve grown was achieved through great effort against harsh conditions.
Knowing how big they’re going to get also sets realistic expectations on the water. Knowing where to cast saves you from wasting hours of your day casting around for a big one when you’re targeting a big one. Targeting deep holes in slow-moving sections yields better results than working shallow runs. Knowing that alpine fish aren’t going to be any bigger just because they’re older will keep you from getting disappointed after a long day of fishing high-country waters.
Timing is everything, too, and as you might expect, these fish typically spawn when water temperatures drops into the low forties (typically during October). The females create gravel nests (redds) to lay their eggs; the fry hatch a few weeks later and are only a few inches long. Their lives depend on the yolk sac until they transition to eating zooplankton; it’s several years before reaching maturity. Every good year adds another generation of fish that could of eventually be caught. This means safeguarding the habitat ensures there will be enough fish left to catch when you return.
To appreciate brookies is to respect how perfectly they are adapted to coldwater environments. You must also understand that they do not thrive unless the water is perfectly clean and stays very cold. From the legendary records, fourteen pounders were pulled from some of the most remote wilderness lakes of Canada, while others are mere twelve-inch beauties. Each fish helps you appreciate their nature. Knowing more about what makes them grow makes every cast even better. Once you realize it is all about the temperature, and how that affects appetite and fish size (you see the stream in a whole new way).