Lake trout are not lazy fish. They won’t wait around for you to do all the work. In frigid waters with plentiful oxygen, food is scarce and predators is competitive. To understand their lives, we must consider what it costs them to live in darkness. Their growth chart depict the slow accumulation of length and weight across decades. It’s a story about patience more then speed.
As you can see, growth is surprisingly fast during first couple of years as opposed to later years. Because they’re feeding on insects and small crustaceans close to shore, a yearling could adds several inches in its first season. That first flush is important; it helps the fish survive its fragile juvenile stage or else they seldom catch up.
How Lake Trout Grow
Once they reach age four, their growth rate drop off significantly, as shown on chart. Their slowdown relates to their habitat since lake trout are coldwater species with temperature preferences ranging from 35-55 degrees Fahrenheit. They’ll also be slower growing and longer living in northern lakes where water is cooler and food is scarcer. Southern populations may mature sooner but they’ll be smaller and live longer.
That brings us back to the lake itself. Trout in a warm southern reservoir will experience something very different from those in a cold Canadian highland lake. The graphic makes it very clear that location of the lake makes all the difference in the world. Fish on northern lakes will grow an inch or two a year and live anywhere from 40-60+ years old. This is an ancient animal. The record size isn’t necessarily due to genetics, but rather just having a few decades to bulk up.
On the flip side, trout on more fertile nutrient-rich lake will be able to fatten out rapidly thanks to abundance of smelt, cisco and other food sources. But this also leads to a trade off. Because their metabolism is running high thanks to such a good life, their lifespan may be relatively short.
People get locked into thinking it’s all about depth, which I understand, because it seems like the thing you’d be doing when targeting these fish. People go out and throw downrigger weights until they feel their line touch bottom and hope the cold water does the rest. That doesn’t take into account details of their seasonal movement though.
During the summer, lake trout live in the hypolimnion, the stable layers below the thermocline where temperatures remains constant. The key here is they aren’t stagnant; they’ll move up shallow during both the spring and fall to spawn as well as feed. According to the chart, mature fish frequently reach spawning grounds in October or November. A better approach would of be to time your trip around this movement rather than simply guessing at depth. It’s not just about finding cold water; it’s about finding an opportunity.
Food availability is a major limit on size. The scarcity of sculpin, whitefish, or other available forage in a lake can keep even the best genetics from growing out. Some populations max out with modest sizes while others produce trophy classes. And fishing pressure does come into play as well, heavy angling eliminates the biggest age classes, resulting in a reset of the population structure and lower average sizes overall. Protecting bigger fish through conservation efforts allows the natural growth curve to play itself out fully.
“On a big lake like this, catching a big laker isn’t as much about luck as it is about respect for time. They don’t rush; they don’t panic. Big lake trout has been growing their body for two decades or longer. You’re putting a lure into their space and essentially you’re asking an efficient, ancient predator to change its routine.”
The chart tells us what they can be when we leave them alone, our job is simply to meet them where they are, quietly and with patience, in the cold dark water where they belong.