I think the local craws are best. They are going to be best adapted to the climate of the locale. It doesn't have to be a lot of them. A good to time to seek them out is in the March through May time frame at your location. Most species of crays up there will exude eggs around then. If he can find just a few of them and a bit of cover for them ... they'll establish. The numbers they can reach will depend on the available cover and their predators. One only need a few pounds overwintering each year to contribute meaningfully to forage.

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers