I agree with Tight Loops. Having just helped to plant Salmon fry in the Walker creek and North Creek the fish tend to stay together for a while after being in small bins together. A guess after being so tightly packed it takes awhile to get used to having so much room. Ours from the time they are eggs till they are released are in bins of about 12"-18"-6". We release ours soon after they hatch and lose their egg sack. If they are raised bigger then I feel they would stay together even longer since up till then its all they know. It takes a few months to get to a 6" size. The ones I helped to release were about 1.5" long many even smaller.