How do you know which fish are safe to eat?

March madness, green beer, the overhead chortle of sandhill cranes, crocus blooming, bald-faced calves kicking up their heels, a bare-topped Rattlesnake Mountain (finally) and the smell of newly turned garden soil. These harbingers of spring remind me that water temperature is rising and fish are getting hungry.

We Tri-City anglers are lucky. Area waterways are filled with walleye, smallmouth bass and channel cats. Local lakes and ponds are being populated with truckloads of hatchery rainbow trout. The Columbia River will soon teem with upstream-migrating spring chinook salmon.

There’s more to catching fish than dreaming about the possibilities though.

Spring means rebuilding tackle inventory, swapping out old monofilament line for new, lubricating reels and cleaning spider webs off rods. It could also be time to add a new fly or spinning rod to your arsenal (and a new reel to match). I recently mounted a rod rack on the garage ceiling to help manage my rod clutter.

For many anglers, harvest is an important part of the fishing experience. I don’t mind bonking a few fish if for no other reason than to satisfy my hunting and gathering instinct. I also like to eat fish. One challenge though is knowing which fish are safe to eat.

“Do you eat smallmouth bass from the Yakima River?” a fishing buddy recently asked. I had to think twice before replying, “I allow myself two meals each spring.”

Why do I limit myself to only two meals of such a fine-tasting fish? Is it possible a regular diet of bass from the Yakima River would damage your nervous system or cause cancer? The short answer is maybe, depending on how often you eat them.

You should limit yourself to two meals of Yakima River bass per month, according to the state Department of Health (DOH). The definition of a meal is 1 ounce per 20 pounds of body weight. As a point of reference, an 8-ounce Arby’s crispy fish sandwich would be considered a DOH-size meal for a 160-pound person.

Regional waters are not pristine. Persistent organic pollutants, including PCBs, DDT, mercury and other industrial and agricultural pollutants, have been detected. Mercury is a particular problem because it bioaccumulates and magnifies moving up the food chain, from insects to minnow-sized fish to predators.

The most persistent contaminants bind to fine sediments to create “hot spots” in slack water upstream of mainstream dams. As an example, the one-mile stretch upstream of Bonneville Dam is red-lighted for eight different species, including walleye, catfish, sturgeon and bass. The Walla Walla River and Brownlee Reservoir also have eating advisories.

Several studies, led by the Environmental Protection Agency, provide information on pollutants in water, sediment and fish of the Columbia and Snake rivers. For the most part, the studies targeted hazardous waster contamination from past industrial practices. But by no means have all waterways been sampled, nor does it look like they will be any time soon, given current politics.

Knowing the life history and behavior of fish you harvest can lead to healthy choices. For example, are they bottom-feeders or predators? Do they migrate or stay in one place?

Eating two to three servings per week of salmon, steelhead and shad is recommended. Their migration from fresh water to the Pacific Ocean and back limits exposure time to pollutants of concern. Panfish, such as bluegill, yellow perch and crappie, typically contain low levels of pollutants because they eat mostly insects and zooplankton. In contrast, bottom feeders like carp and catfish, and resident predators like large walleye and bass, are more likely to contain elevated levels of contaminants.

Proper cleaning and cooking of fish helps reduce your exposure risk. Remove the skin, trim fatty tissue along the back and belly and remove darker meat running along the lateral line. Grilling or baking your fish (instead of frying which binds up certain pollutants) is the safest way to prepare a meal.

The flip side to all this is eating fish is important for a healthy heart and enhanced brain function. If you’re nervous about what comes out of the river or pond, there’s always Grandma’s tuna noodle casserole. Make sure she serves up the “chunk light” version, because “chunk white” tuna or albacore contains higher concentrations of mercury.

Dennis Dauble is a retired fisheries scientist and author of three books about fish and fishing. Learn more at his website DennisDaubleBooks.com.

This story was originally published March 18, 2017 at 6:39 PM with the headline "How do you know which fish are safe to eat?."