There are two unrelated kinds of sunfish: saltwater sunfish and freshwater sunfish. The saltwater or ocean sunfish is also called the common mola, and it ranks among the heaviest bone fish in the ocean with an average weight of 2,200 pounds (997.9 kg). The freshwater sunfish is divided into dozens of species, such as the bluegill, the pumpkinseed and the rock bass. The freshwater species usually weigh less than one pound (.45 kg), although records have been set with anglers who have recorded fish weighing more than two pounds (.91 kg).
The common mola is native to temperate and tropical saltwater seas and oceans. It has a flattened shape and has a habit of floating near the top of the water so birds can remove parasites from its body. In addition, it has four teeth that are fused together to form a beak. Besides its flattened oval–like shape, the mola has the ability to change colors. For example, the skin is usually gray or white, but it can become lighter or darker in color when it is under attack.
The common mola typically eats jellyfish, squid, and small fish. In addition, they are considered non-aggressive toward humans. The largest danger they pose is damage to boats because of their hefty weight. In addition, the meat of this saltwater fish is thought to be a delicacy in many Asian countries, but care must be used to ensure the meat does not contain toxins that are poisonous, if consumed.
The freshwater sunfish contains dozens of species of fish. All the species are native to North America, although some species have been introduced elsewhere in the globe. These small fish are popular among anglers for sport-fishing. Depending on the species, they can have hints of blue, green, and orange, but the primary body color is typically brown or gray.
Many freshwater sunfish eat insects, minnows, and crustaceans. Interestingly, many species have been known to eat their eggs. They are usually eaten by largemouth bass, walleye, muskies, and other larger fish.
Because freshwater sunfish, such as the bluegill have populated so many lakes in North America, teams of scientists have started researching and managing the fish. Bluegill, for example, are quite prolific. Because of the abundance of bluegills in lakes, stunting has occurred. This means that the fish are smaller than they once were, changing the size of the species. Scientists hope that predators will eventually consume the smaller fish, allowing the species to return to its original size.