In captivity, the nutritive demands of aquatic mammals are super-ceded by the practical considerations of price and availability. In many respects, the criteria established for marketing quality fishes does not meet the biological requirements of the animal. In fact, many of the existing diets expose the animals to toxins, antimetabolites, and nutritional deficiencies. The present report uncovers some of the nutritive differences between the food available to feral and captive animals, and makes recommendations for upgrading dietary quality.