2001
Time to Start Frying Fewer Fish?
I love to eat, and I love to eat fish. But lately I’ve been realizing that it might be time to start frying fewer fish. Not time to stop fishing, just time to start putting a few more of them back in the lake.
Now, a lot of people might be quick to agree that catch-and-release is a good idea down south, where there are more people fishing, and where anyone can drive on up to the edge of any lake. But up north in the Boundary Waters and Quetico? Who needs catch-and-release in the wilderness? Hardly anyone ever goes there, and there are plenty of fish for everyone. After all, how many fish can you eat while you’re out there? You can’t portage them all back to the car, can you?
But things aren’t so simple. First of all, the Boundary Waters and Quetico aren’t a wilderness area that never gets fished. Over 200,000 people visit the area every year. While some of us don’t even bring a fishing rod, most of us do. For many of us, fishing is an integral part of the experience.
Too many people, however, still believe their trip has been a failure if they don’t eat fried fish for every dinner-and even for every breakfast. Sixty years ago, maybe that was a reasonable expectation. Today, it’s not. Now, I’m not saying we shouldn’t keep any fish for the frying pan. But maybe it’s time to think about leaving a few for next time.
Believe it or not, catch-and-release is even more important in cold, northern lakes than it is farther south. To see why, let’s quickly review some basic high-school geology and biology.
Lakes that are warm, shallow, and fertile are called eutrophic. Lots of nutrient chemicals wash into them. These nutrients feed algae and other small plants, which in turn feed small animals called zooplankton. They feed minnows, which then feed the fish that we like to catch. That whole food chain idea.
Most lakes in the Boundary Waters and Quetico—and especially those even farther north—are deeper, colder, and less fertile. That’s one reason why they’re so clear. They’re not necessarily less polluted, they’re just less fertile. They contain fewer nutrients, and thus less algae and other plant life to cloud the water. Biologists call these lakes oligotrophic. There’s still life in these lakes, but it takes a lot more water to support the same amount of it.
Plus, the few fish that are there will grow much more slowly. That’s partly because there’s less for them to eat, and partly because the water is colder. Since fish are cold-blooded, their metabolic rate slows when the water is either above or below a certain optimum temperature. That temperature is different for each species; for trout, it’s about 59 degrees F. For every degree warmer or colder, their metabolism slows by about 4 to 5 percent.
Now, just in case you’re already thinking of using this information against them... You may indeed be able to find more summer lake trout with a thermometer on as string than you would with a fish finder or a dissolved oxygen meter. If this trick works, however, then please consider one other implication of your new inside information about trout metabolism. Later on in the fall, when all the water in the lake is colder than 59 degrees, a trout’s metabolism slows down. Regardless of how much food there is to eat, they may not be hungry. That means they’re harder for us to catch, but it also means their growing season is shorter-especially in cold, infertile northern lakes. With such a short growing season, it takes a lot of years to grow that trophy fish.
When a fish’s metabolic rate varies in this fashion, that also makes it possible to tell just how slowly it’s growing. Turns out, fish have growth rings in their scales and bones, just like the growth rings in a tree trunk. With a microscope, biologists can use these rings to tell how old a fish is. In the Summer 1998 issue of Boundary Waters Journal, fisheries biologist Brian Borkholder described a study of growth rates among smallmouth bass in Basswood lake. This lake is more fertile than most in the neighborhood, and has higher populations of food sources like crayfish and cisco.
Still, Borkholder found that the average 18-inch-long smallmouth was about 10 years old. After that, they grew even more slowly; a 20-inch smallmouth was at least 16 years old. In warmer, more fertile waters, smallmouth often reach that size in less than half the time. (Fortunately, these biologists were able to practice catch-and-release. They carefully snipped a single dorsal spine off close to the body, and then released all of their subjects relatively unharmed. Nice work if you can get it.)
Growth rates for other game fish are similarly slow in cold, northern lakes. You may have even noticed how northern pike caught in oligotrophic lakes are actually shaped differently, with a head that’s much larger in proportion to their bodies. That’s because of their unusually slow growth rates.
Sure, catch-and-release is an OK idea for those warm, green lakes down south. But for all these reasons, it’s even more important in cold northern lakes.
I’ll have to admit, though... After you’ve been out a while, a meal of fried fish can be a nice break from the noodles and granola. Still, maybe it’s time to give up on the idea of frying fish for every dinner and every breakfast.
And when you do keep fish, consider keeping a few of the smaller ones. Small fish grow much faster, and they’re not reproducing yet. The biggest fish are the ones that do the most to increase future populations. Besides, let’s face it. The really big fish don’t usually taste as good. I personally have rarely had to worry about this, but that’s what I’ve heard.
There’s one more problem, however. All too often, despite our best intentions, the fish we catch and release are floating belly-up a day or two later. Next month, a few tips for ensuring that the fish you watch swim away will keep on swimming.
