Koi
The major named varieties include:Goldfish (金魚) were developed in China more than a thousand years ago by selectively breeding Prussian carp for color mutations. By the Song dynasty (960–1279), yellow, orange, white, and red-and-white colorations had been developed. Goldfish ("Carassius auratus") and Prussian carp ("Carassius gibelio") are now considered different species. Goldfish were introduced to Japan in the 16th century and to Europe in the 17th century. Koi, though, were developed from common carp in Japan in the 1820s. Koi are domesticated common carp ("Cyprinus carpio") that are selected or culled for color; they are not a different species, but a subspecies, and will revert to the original coloration within a few generations if allowed to breed freely.
Hardhead catfish
The hardhead catfish ("Ariopsis felis") is a species of sea catfish from the northwest Atlantic and Gulf of Mexico, and similar to the gafftopsail catfish ("Bagre marinus"). It is one of four species in the genus "Ariopsis". The common name, hardhead catfish, is derived from the presence of a hard, bony plate extending rearward toward the dorsal fin from a line between the catfish's eyes. It is an elongated marine catfish that reaches up to in length and in weight. Their typical weight is less than , but they commonly reach up to . They are often a dirty gray color on top, with white undersides.