I think fishing is all year round. As far as stocking: carp, catfish, and bass are in there all the time and trout too but I don't know when they stock with trout. You do have to have a valid AZ fishing license to fish in any body of water (including canals, i believe) and you may need to get a trout stamp. Licenses last 1 year from the date of purchase unless otherwise specified.
Valerie is dead on.
Fishing is year round. You need a parking pass to park there. They sell daily passes or annual passes with the National park pass or the Discovery pass. I have seen Karp, catfish and bass in the river.
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