Feb. 9, 2018, 2:30 a.m.
A view from above and below: Hatchery chinook salmon are self-sorting in tanks
Hatchery-raised chinook salmon sort themselves into surface- and bottom-oriented groups in their rearing tanks, and this behavior might be due in part to the fish's genes. https://www.sciencedaily.com/releases/2018/02/180208162049.htm