Questions..
How many pounds of fish should I expect to produce?
Should I go with brook trout? the water is COLD!
Any thing else you can suggest about my plan?
Typically raceways produce about 50 lbs. of trout per gpm but they use much higher flows than 20 gpm. I see a lot more flow there than you are extracting. If it was me I'd try a little harder to get more flow -- especially to counteract the times when your flow will decrease.
Water temp is typical at your latitude. Contrary to popular believe, temps don't vary from spring to spring or well to well, but are more associated with latitude.
Your water will warm a little with use; I wouldn't worry about it being too cold for any species of trout.
If it was me I'd go with an economical way to build raceways. Probably raised wooden one(s) with cement blocks to elevate them and an EPDM liner(s),which can be purchased from a building supply store in six foot widths that are used for under layment for roofing. Contrary to what some of the aquaculture catalogs will tell you, they are safe for fish and should say so on the liner itself. I bought some a while back at Menards and it said in distinct white letters, "Safe for Aquatic use" or something to that effect.
Another option are circular tanks that make better use of the water resource and can be made to be self cleaning with a standpipe inside another one. You can build them yourself if you're handy or pick up some stock tanks.
The concerns I would have are low flow and high flow events. Low flow could leave you with dead fish and a flood event could wash away your hard work. And as mentioned silt could be an issue. I would engineer some kind of filter if need be and a bypass in case of a flood event.
If you P.M. me your name and mailing address I can send you a discount coupon you can mail in for a book that covers what you are contemplating. It's called Small Scale Aquaculture by Steven VanGorder (the author lives in PA) and with the coupon you can get the book for $16.00. I don't make any money off it this, just want to make an outstanding book available that was written by a friend. He has a chapter devoted to flow through systems.
I produce trout in a 100,000 gallon earthen pond flowing 45 gph of well water into it 8 months of the year. It produced much lower production rates than a raceway at only 500 lbs. upon final harvest.
