Some ocean species and habitats struggle to recover on their own and need help. Take sea otters, which were virtually eliminated by the end of the 19th century by commercial hunting for their super-dense pelts.
From the 1960s to 1990, some sea otters were moved to repopulate places where they had once lived. Today there are about 150,000 sea otters in the wild and a third of them are descended from translocated otters.