Idaho's deep-dwelling pygmy whitefish

Ever heard of pygmies in Idaho? Most people haven't, except maybe those that have heard of the cute little pygmy rabbits in that dried-up desert country.

There is another "pygmy" creature ... and this one is a fish.

In the northern part of the state where things are wet and green and natural lakes abound, there are so many kinds of fish that many people haven't ever heard of all of them. One little-known species is Idaho's amazing little pygmy whitefish.

There are three kinds of whitefish in Idaho; mountain whitefish, lake whitefish and pygmy whitefish. Mountain whitefish are a native fish found all over the state in many of our streams, rivers and lakes. Lake whitefish were stocked into Lake Pend Oreille from the Great Lakes about a hundred years ago to provide a food source for miners and have established a self-sustaining population. Pygmy whitefish are a native fish to Idaho.

Pygmy whitefish are found in the Priest Lake system, Spirit Lake and Lake Pend Oreille, but biologists really haven't looked for them in some of the other lakes. As you probably guessed from the name they are a small fish; a large specimen is only about 6 inches long. They typically live in deep water near the bottom so they are rather easy to miss unless you are specifically looking for them.

How deep do they live? The known record has to be the ones Idaho Fish & Game research biologists caught in nets set in 1,100 feet of water at the bottom of Lake Pend Oreille. One 6-inch-long pygmy whitefish was aged at 14 years old. That is an old fish considering some of the literature says they only reach about seven years of age. Somehow, the whitefish on the bottom of Lake Pend Oreille eke out an existence in the perpetual darkness at the lake's bottom where no plants can grow and the water pressure is more than 440 pounds per square inch.

In 2009, numerous small fish were recorded near the bottom of Upper Priest Lake. Idaho Fish and Game was conducting nighttime surveys for lake trout using their scientific echosounder to make fish population estimates. The survey showed fairly high densities of 1- to 6-inch fish in the middle of the lake swimming close to the bottom ... but only after dark. During the day the lake bottom seemed pool-table flat and almost devoid of fish. At night the lake bottom came alive with an estimated 140 fish per acre cruising the 100 foot depths. That is a lot of fish for the sterile waters of the Priest Lake drainage.

Unfortunately, the echosounder cannot identify the species of the fish. So, in 2010 Idaho Fish and Game dragged a trawl net along the lake's bottom. Tows of the net caught around 40-60 pygmy whitefish per haul, along with a few small lake trout and sculpins. Based on the finding that 95 percent of these deep fish were pygmy whitefish, we figure the lake contained more than 100,000 of the little fish.

Upper Priest Lake contains thousands of predatory lake trout and yet these little bite-sized whitefish have maintained a strong population. How they do it is anyone's guess, but it is pretty amazing.

So now you know about one of Idaho's secretive pygmies. They are not as warm and fuzzy as that desert creature the pygmy rabbit, but they are truly emblematic of the watery northern part of the state.

Melo Maiolie is a fisheries biologist for the Idaho Department of Fish and Game.