Tracy,
Bill C. recommended I stock 2500 papershell craws (PSC)to get an established population in my half acre as there are predators already present. I have rip rap and concrete slab for habitat. So for your 3.5 acre, that comes to 17500 to establish a population.
Hey, Bill D. Where were you able to get papershells? There are tons of craws for sale now here in Louisiana, but I don't think they are PSC.