The first time I fished for pikeminnows was with my son and grandson last year. We caught 9 keepers in a few hours fishing in 20-25 ft. of water. The next trip we only caught 1 at the same spot.
I live on the Elochoman River and during the summer I can see nice sized fish swimming in the clear shallow water right behind my house. My neighbor told me they were Pea Mouth. They look just like pikeminnow, but have smaller mouths and are not bounty fish. On a whim this last summer I thought I'd catch one just to see. Sure enough they weren't pea mouth, but spawning pikeminnows. Since they aren't in the Columbia River there is no bounty them here even though they had to swim up the Columbia to get here.
To make a long story short, I decided to learn more about how to catch them. I fished them quite a bit this summer and experimented with all sorts of variations. Here's my most deadly combination.
A trout rod and reel
sliding lead, any type will do
6 lb. test leader at least 1 ft. long
1/2 of a large night crawler
a sharp hook suitable for about an 18 inch trout.
They say to fish in about 25 ft. of water, but I was catching them in 3 ft of water behind my house.
The above rigging is standard fare for fishing trout with a nightcrawler.
Location is a big factor in your results. They're typical predators that will congregate around the mouths of tributaries, dropoffs and any type of underwater structure. Just drop anchor and if you don't get a bite within a few minutes, then move.
If you want make a lifetime fishing buddy, take a very young person fishing these scrappy little buggers. After they have fun catching them the fun is not over, oh no, grandpa pays them the going rate of the bounty so they don't have to wait weeks for their check to come back from the state. Then grandpa takes them and their bounty money down to the store and they get to buy neat stuff like toys and such. It's a guaranteed great time!