I would not look at this as a strictly protein issue. If protein in excess relative to energy you are gaining nothing. I will be the rainbow trout, if cultured and in good condition, will give a better protein to energy ratio than wild stocks that may seasonally be lower in fat. Crayfish are seasonally very variable in energy that would only partially be offset by cherry picking for peelers / soft-shelled crayfish.
Feed your forage to meet more than just the vitamin and fatty acid issues typically of concern.
