That fish is how old? Idaho’s lakes, rivers can provide some tales for the ages
Wildlife has fascinated me since childhood. From watching nature shows and memorizing Wildlife Fact Files to searching the backyard for snakes and salamanders, I could never get enough. To this day, seeing river otters, turtles or a bald eagle on a fishing trip is always the first thing I tell my two nature-loving daughters when I get home.
Over the years, my efforts to add to my knowledge tackle box dovetailed with my study of nature. After all, learning as much as you can about a fish’s diet, habits and life cycle goes a long way toward improving your angling success.
One fish factoid I find especially interesting is lifespan, which varies wildly between species (and regions) and has some surprising wrinkles. Through my fishing classes, I’ve also learned fish lifespans are misunderstood by many anglers.
If you’ve ever caught a big fish and wondered how old it was, here’s an Idaho guide (with variance allowed for the whims of nature, and our state’s geographic diversity).
Bass: Up to 15 years. Both largemouth and smallmouth bass can live more than a decade, with largemouth having slightly longer lifespans. In an interesting twist, Idaho bass may live longer than most. Studies show that bass in colder climates have a slower growth rate but live longer, sometimes surpassing 20 years. This phenomenon is common across many species — colder habitat often means slower growth rates and longer life. Big Idaho bass are likely pushing 10 years old, and those 6-pound giants swimming in the local ponds might be teenagers!
Trout: About 7 years. Trout are fast-growing fish with relatively short lives. Idaho rainbow, brown and cutthroat varieties typically max out at about a decade. According to my biologist friends at Idaho Fish and Game, the majority of big trout in river systems die out naturally, clearing the way for the next-age class of fish to take their place.
Kokanee: About 4 years. Kokanee are the fish on this list with the shortest lifespan. Adult Kokanee, typically after their third or fourth growing season, head up tributaries to spawn. And like most salmon, their spawning journey is a one-way trip, as they create the next generation and then die.
Crappie: About 7 years. Another short-lived species, crappie often experience boom and bust years in fisheries like Brownlee and C.J. Strike reservoirs. A highly successful spawning class will lead to several years of great fishing, typically years three through five, when crappie reach popular harvest sizes of 10 to 14 inches. The year class gets thinner after that, although surviving fish can reach 16 to 17 inches.
Bluegill: About 8 years. These feisty panfish can live up to a decade. Bluegill (and crappie) share some genetics with bass, and can experience the same slower-growing, longer-living effects in colder climates.
Perch: Up to 12 years. In another unique Idaho wrinkle, Lake Cascade’s legendary jumbo perch have been known to live up to 15 years — pretty much unheard of for yellow perch, and one of the reasons the lake grows such giants. In most places, the maximum perch lifespan is closer to 10 years.
Carp: Up to 20 years. Carp lifespans haven’t been studied extensively in Idaho, but data from other regions suggest they live up to 20 years. Their close cousin, the Koi fish, has been known to live up to 200 years in captivity! In its native Japan, the Koi is a good-luck symbol for long life.
Lake Trout: Up to 50 years. Also known as Mackinaw, these deep-water dwellers earn a distinction from other trout because they can live five times as long. (They are also technically char.) The rarely captured monsters that reside in places like Payette Lake and Bear Lake can live up to 50 years! Catching one is a special experience, especially through the ice.
Sturgeon: 100+ years. We’ve come to the grandaddy of them all. Yes, sturgeon really can outlive humans. If you’ve ever caught a big one in the Snake River, odds are it was older than you. These prehistoric giants never stop growing (which is true of most fish), and since their lifespans are measured in decades, it’s no wonder they can surpass 10 feet in length and weigh several hundred pounds.
So, there you have it. The next time you catch a fish, you’ll have a better idea of how old it is. Not every big fish is old, and not every small fish is young — food supply and population density can greatly impact size-to-age ratio — but it’s cool to think about how long our finned friends are capable of swimming around out there. And having that knowledge can help us make informed decisions as anglers.
Tight lines!
Jordan Rodriguez has been fishing Idaho waters since he was a teen. Share your fish stories, adventures and questions with him at tightlinesboise@gmail.com , or visit www.tightlines208.com for the latest local fishing reports and upcoming class offerings.
