We've established criteria to ensure that any marine mammals being released into wild populations have the best possible chance of long-term survival. Marine mammal patients receive a thorough medical examination to ensure that they're clinically healthy and free from disease. They must also be at a satisfactory weight for their species. Marine mammals rely on their blubber to keep them warm, as well as to provide a source of calories when food is scarce. Lastly, they must be behaviorally competent. When appropriate, marine mammal patients are given "live fish trials" before release, to test how well they can hunt and catch live feed. The Department of Fisheries and Oceans is the authority that makes the final decision on whether an animal can be released.