If you’ve caught a brown trout before, chances are you’ve encountered one of two varieties. The first one is a nervous little sucker that darts back and forth in shallow water with a quick flash of silvery scales. The second is an old codger that slowly walks along the bottom of deep pools with side-blotches of amber. It’s the same species, yet they’re very different. Knowing which one to expect requires reading the water propery. Casting at a little parr like he’s a big lake trout are going to lead to frustration.
A growth chart turns guessing into a game plan. From the day it was born until you set the hook, a brown trout has been living its life. It was laid as an egg in gravel in the cool fall. As an alevin, it’s weak, has a yolk sac and is just hanging on through the winter. Its first season isn’t much better. The yolk sac dissapears by spring and fry begin feeding on zooplankton. Now small but fierce, fry protects what little territory they can find behind pebbles, yet remain hidden most of the time. Conditions, predation and other factors kills most of the young in the wild. Those few who live past two years prove themselves hardy.
How Brown Trout Grow and Change
What they eat will change over time and impact your fishing approach to them. Young trout feed primarily on insect larvae such as mayfly nymphs, stoneflies, etc. This is easy to understand and fish since you can target those little guys with small flies on the bottom or by watching them rise for dry flies on the surface. But once the trout hits its adolescent stage (typically between four and five years of age), their behavior become different. Their jaws becomes hook-shaped in males and they cease feeding primarily on insects. Instead, they begins pursuing other fish and crayfish. You can see this transition easy through a growth chart and it has everything to do with their increased caloric requirements. They aren’t ignoring bigger food items on purpose; instead, they is eating them to be more efficient.
The other thing is where does the trout live based off its age? So a two year old fish may spend his time on the banks and hide under logs in six inches of water. But an older one probably will be out in those deeper pools eight foot or more from surface. The older ones are habitual. They slow their metabolism down as well but becomes bigger so they needs to conserve energy. So what you’re doing is targeting areas with structure because you want it to match up to the life stage of the fish. You’re not just fishing for any fish; you’re looking for the right habitat for that age group.
Where did that trout come from? Hatchery raised fish that are released into nature has a shorter life span than wild browns. Stocked fish might only live two years if they is stressed or killed by predators. A wild brown can live for a dozen or more years in a good habitat. Some survive to twenty years in Scandinavian lakes. Those old ones appear distinct; they’re stronger bodied, darker, the spots fade. Their pace is slow but strong.
The scales (or otoliths) are like a time capsule for a big fish and will tell you exactly how old they are. The rings forms closely each winter, just like a tree trunk. If you count those rings it reveals the real story of the fish’s life. You can map out where those rings match certain sizes and ages in a visual guide. It also serves as a reminder that all big trout is survivors through many harsh winters.
You interact with several generations at once when standing on top of a river. Each generation have its own set of rules. The deep pool is for the old fish. Mid current for the juveniles. The fry are near the bank. Adjust your patience, depth and lure size to fit each life stage. Your big fish is related to that little trout that’s taking your fly off. You should of respect this life cycle and the river will reward you with good fishing.