Find a fish farm that is raising the fish and make a deal with them. You can buy stock trout by the truckload, put them in a holding tank, and practice away. It may not be a completely natural environment, but I think you'll find what is effective in the tank will be effective in a pond or stream, more or less.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)