Its not often you get to peek into a lake and see what dwells there, but thats what Idaho Department of Fish and Game crews did this month at Lake Cascade.
The peeking was via gillnets strung from different points at the lake to get a sample of the fish populations. Its like a fish geeks version of trick or treat you end up with a whole variety of stuff.
Trout, perch, bass, suckers, bullheads, pikeminnows and kokanee all went into the tub. The fish were measured and recorded into a database and compared with surveys from years ago.
Surveys give biologists an idea of not only the fish populations, but the age structure and the all-important question of whos eating whom.
Most anglers arent interested in pikeminnows, which are at best a nuisance and at worst a highly effective predator that keeps other fish populations down.
Thats what Fish and Game biologists Paul Janssen and Dale Allen decided about 10 years ago.
They netted the lake and found no young perch, or many young fish of any kind. A large population of big pikeminnows was limiting the fish population.
They were literally eating all the juveniles of every species, including their own, Janssen said.
Pikeminnows live a long time up to 18 years and the two biologists decided waiting for the pikeminnows to eat themselves out of house and home was not a good management option.
They set out to tip the balance back in favor of the reservoirs game fish, most notably its perch.
Thats what makes this lake work: billions of young perch, Janssen said.
Everything eats young perch, Allen added.
NOT JUST FOR SCIENCE
They took on a multiyear project to reduce the pikeminnow populations and boost perch numbers, which once attracted thousands of anglers who spent millions in the Central Idaho town.
About 528,000 perch were caught by anglers in 1986 when Cascade anglers were enjoying more than 400,000 hours of fishing that added $4.5 million annually to the local economy, according to an economic study done then.
To restore perch, Fish and Game crews started trapping pikeminnows in the early 2000s with large nets set from shore. Crews also blocked their upstream spawning migration and poisoned them for several years in a row.
Crews trapped and transferred nearly 900,000 adult perch into the reservoir between 2004 and 2006 and continued stocking hundreds of thousands of trout and kokanee.
Small perch, which were the offspring of the adults planted in the reservoir, started showing up more each year as Fish and Game crews sampled the reservoir. In 2006, anglers also started catching them during the ice fishing season.
We reduced pikeminnow numbers and jacked up the perch population as high as we could, Janssen said. We made sure perch had an advantage. We increased recovery time by eight to 10 years.
Fish and Game didnt eradicate the pikeminnow, which was obvious from their netting earlier this month.
The reservoir still has lots of them, as well as some big ones. But killing them off wasnt the goal, Allen said. It was knocking the population back enough to allow game species to flourish.
Theres definitely a lot less pikeminnow were seeing, and theyre smaller, he said.
At the same time, both adult and juvenile game fish have returned.
One net caught trophy-sized perch, trout and smallmouth bass, as well as the reservoirs lesser-known fish such as brown bullheads.
Much of the boost is attributed to the rebounded perch populations.
But the reservoirs fish populations are dynamic, and there will always be fluctuations between the different species.
Trout populations are doing very well now thanks to generous stocking by Fish and Game and plenty of forage thanks to those young perch.
Theres more trout here than Ive ever seen in this lake, said Janssen, who has worked as a biologist in McCall since 1990.
But different species will also boom and wane.
Currently, there are lots of large smallmouth bass in the reservoir, but biologists are seeing few young bass to replace them. Perch may be part of the reason there are so few young bass.
Perch are good predators, too, Allen said.
That could mean a crash in the bass population in the future.
We dont know for sure, but we havent seen many juvenile bass in our sampling, Janssen said.
NO EASY ANSWERS
Part of what makes Idahos fourth-largest body of water interesting yet frustrating is its changing nature.
Cascade Dam created the reservoir in 1948, and since then, it has been stocked with a whole menu of fish, including trout, coho, kokanee, perch, bass, bluegill, crappie, bullheads and tiger muskie all of which added to the native trout, suckers, pikeminnow and others that already existed.
Biologists can only do so much to manage those different fish populations, which often compete with each other.
A CHANGED FISHERY
Another challenge is many anglers remember only the best of times, even if the good ol days were just a few years or even a decade. That period becomes the standard by which every other is judged.
During the prime years in the 1980s and early 1990s, nearly anyone could pull a bucket of perch out of the reservoir. Despite the likelihood there are millions of perch in the reservoir, that hasnt been the case in recent years.
What weve seen is perch fishing hasnt done as well as the population shows, Allen said.
Cascade appears to have shifted from a family fishery where lots of fish were easily caught to more of a trophy fishery that caters more to specialized anglers than casual ones.
Those who put in the hours and learn the lakes nuances, or those who are simply lucky, are rewarded with some big fish, whether perch, bass, trout or something else.
Cascade is a year-round fishery, and each season brings something different.
Trout fishing has been good this fall, but soon the reservoir will freeze and ice anglers will get their shot.
In the last few years, ice anglers have taken some huge perch out of the reservoir, including one in 2012 that tied the state record 16 inches, 2 pounds 9.6 ounces caught by Bobby Shindelar of Meridian.
Allen said those perch grew big because Fish and Game knocked back predator populations and there was plenty of food to eat.
Theres a lot more competition now, so its not going to be like it was in the last couple years, Allen said.
But he hopes anglers might catch more perch this winter and those big trout remain active year-round.
Allen and Janssen hope anglers will start paying more attention to Cascade and take advantage of those big fish and resurging perch population.
I think its time to come back and put some time into Cascade because were definitely not seeing the fishermen, Allen said.
Roger Phillips: 377-6215, Twitter: @rogeroutdoors