By Martin J. Kidston
As the soggy shells of burrowing mayflies decompose in the sun, the swallows chatter madly overhead. The feisty birds flutter about, defending their nests in the lakeside cliffs which are now a dry, dusty walk from the retreating water.
Northcentral Montana knows the promise of rain in August is little more than a dark cloud looming on the horizon. And with such minimal moisture falling in the summer, reservoirs begin to draw down, leaving the lakes fish in competition for the diminishing aquatic habitat.
How the fish respond to that changing environment while maintaining their reproductive success is the question Montana Fish, Wildlife and Parks Biologist Kent Gilge wants to answer. Accompanied by fish technician Tim Roth, the two-man crew prepares to set out for the waters of Fresno Lake where it will conduct the divisions beach seining studies.
In his office, Gilge explains the studies are a way of counting the lakes new fingerlings, or young of the year, which are present in the underwater world.
The studies are a way for us to gather long-term information on the reproductive success of the lakes fishes, Gilge says. They demonstrate trends which help us get an idea of what occurs over a 30-year period.
Gilge points to the fish specimens he has contained in formaldehyde on a shelf below his window. Pike, perch, spot-tailed shiners and crappie are among the fingerling samples which, at their young stage of development, are quite similar in appearance. With their sleek, wet bodies and black, embryonic eyes, they float nose up in bunches like strands of kelp anchored to some invisible stone.
In a quiet, lifeless way, the fish tell a story of the struggles hidden under the breakers of a shallow prairie lake, where survival is uncertain and mortality rates change from year to year.
In order to understand those mortality rates, Gilge and Roth finally lock up shop on a crisp Tuesday morning and head out to the sampling stations scattered about Fresno Lake. With boat in tow and the lake but a short drive west, their mission, they say, is simple: To accumulate data and test the reproductive success of this summers hatch.
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In the rising light of a crisp August morning, the placid waters of Fresno appear from the apex of a grassy knoll. Theres not a cloud in sight, and while the truck backs the boat into the water, the only rise comes from the terns diving into the lake before reappearing with a splash and flutter.
Roth climbs into the aluminum boat and gives the engine cord a tug. The motor sputters on with a hum and churns the water in a quiet, lazy effort. With a practiced turn, Roth guides the boat away from shore and like a ripple ventures into the breadth of the lake, the seining net coiled in a high mass at the bow.
It takes Roth 15 minutes, the car even more, to reach the waters of Kiens Bay. Pulling up, the boat is already sitting on the moist sand, its aluminum hull just steps away from a line of mayfly hollows positioned where the last draw down left them. The gnats are getting thick.
These are ideal conditions, Gilge says, taking Roths place in the boat. We dont get this very often.
The lake is a mirror reflecting the blue of the sky, but as Gilge takes the boat back onto the water, its wake shatters the glassy calm. Roth has taken hold of the free end of the seining net and as the boat moves out, the net rolls off the bow like the letting of kite string to form a half-moon on the water, ending where Gilge lands the boat 30 feet down shore.
Held afloat by a series of buoys and weights, the net traps everything between the beach and its weave. Gilge moves into position and the two men begin pulling the net, slowly drawing the catch into the shallows.
We just loop it out and draw it in, Gilge says, just like that its that simple.
With the net drawn to shore, hundreds of small fish splash in the allotted water. Gilge and Roth crouch over the catch and begin taking the fingerlings by the handful, counting and identifying each one.
Theyre mostly yearling perch and a few spot-tailed shiners, Roth says, tossing the small fish out into the open water.
As if sorting marbles, the men separate the fish when Gilge spots a small walleye in the catch. He sets it in a nearby bucket and when the catch is counted, identified, recorded and released, Gilge measures the single walleye.
3.2 inches, he announces, placing the fish on a device that resembles something used to measure the size of a foot at the shoe store. Gilge tosses the walleye back into the lake.
There was a good number of perch in that catch, he says, helping Roth coil the net back onto the boat. I like the fact we didnt see any pike. Generally, there are too many of them.
There are no roads leading to the next stop, so the boat is loaded to the hilt as it trolls across the bay to an isolated cove where the water is murky and green.
Were going to get some pike in this one, Gilge presumes, letting us off on shore before casting the net. As the net is looped into position, Roth points out the call of the killdeers and the tracks of a raccoon.
As we work our way up the lake and the water gets muddier, well start getting different fish species, Roth says.
Drawing in the net their presumption holds true: The catch shows fewer perch than the first, mixed with other species to include a three-inch pike lurking in their midst. Gilge sets the pike aside for dissection, and after counting the catch, its moment comes. A quick, accurate slice up the pikes belly reveals the animals stomach. Opening the stomach, a tail appears, followed by the body and the partly digested head of another small fish.
A walleye, Gilge says. Out of all those perch he picks a walleye. He probably ate him less than two hours ago.
The catch revealed more than 600 fingerling perch, and because the pike took a walleye, it prompts Gilge to explain the other significant factors of his study.
This particular sampling also is meant to classify older fish and to understand their relationship with the fingerlings, Gilge said, referring to the study he calls recruitment. Just because we have a large, successful hatch does not mean we will have large numbers of fish recruited into the adult population.
Gilge cited past data which had shown a large hatch of walleye, followed by low winter lake levels that resulted in fewer walleye passing into the adult population.
Predation, cannibalism and migration out of the reservoir may all be factors, Gilge said. It definitely affects the number of fish that will recruit the next year as one year-old fish.
After the study and despite the walleye found in the pike, Gilge found more walleye up the lake. He says their numbers have remained steady over the last three years.