TJ -- there are grass pickerel in Lewis and Clark Reservoir and in quite a few of the Sandhill lakes. However, they are a lot smaller than chain pickerel. At Pony Lake on the Valentine Refuge, the biggest we caught was about 10 inches, and most were 6-8 inches. Send me an email or PM me an email address, and I'll send you the paper. Knowing your interest, you might like to see the information.
