Omnivores that live in the ocean include sea turtles, manatee, dolphins, opaleye, saltwater crabs, lobsters, sea otters, sharks and whales. Deep-sea omnivores include copepods and some species of squid and octopus. Among sea birds, several species of seagull are omnivorous.
Living in large open habitats like the ocean means that animals must be able to take advantage of food whenever it presents itself. Marine omnivores must either wait for food to drift their way or range over vast territories to find it. Omnivores have a distinct genetic advantage over obligate herbivores and carnivores because they can eat almost any protein available, sometimes even carrion, depending on species.
Just like omnivores in other habitats, marine omnivores may be either primary consumers or secondary consumers in the food chain. Primary consumers usually feed on plant matter and serve as food for secondary consumers, which in turn serve as food for tertiary consumers such as sharks and whales. Ocean-going omnivores, such as crustaceans, fish and mammals in particular, are excellent sources of protein and other nutrients.
Marine omnivores, like other omnivores, have evolved into very successful organisms, and representatives are common throughout the orders of plants, animals and insects. Not just opportunistic feeders, many rely on their varied, high-protein diet to remain healthy.