Researchers determined that fish raised in circular tanks migrated downstream faster upon release, reaching a checkpoint five days earlier than their brethren. More of them survived, as well -- 72 percent compared to 52 percent of fish raised in rectangular tanks, according to a Freshwater Institute news release. Also, the fish raised in circular tanks included fewer "mini-jacks," juvenile salmon that become sexually mature early and stay in freshwater rivers instead of migrating to the ocean. Researchers are concerned that hatchery-raised jack salmon can distort the genetic makeup of wild salmon over time.