Koi, Cyprinus rubrofuscus
Koi, Cyprinus rubrofuscus. Fish caught within Crystal Gardens, Phoenix, Arizona, November 2017. Length: 56 cm (22 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
Koi, Cyprinus rubrofuscus. Fish caught from a residential pond in the greater Phoenix, Arizona area, June 2020. Length: 1.16 m (3 feet 10 inches). Catch, photograph, and identification courtesy of Ben Cantrell, San Diego, California. Note: this fish significantly extends the known maximum for this species.
The Koi, Cyprinus rubrofuscus, is a member of the Carp and Minnow or Cyprinidae Family, and also known as the Amur Carp, the Japanese Carp and the Nishikigoi Carp and in Mexico also as carpa barrigona. Globally, there are twenty-four in the Cyprinus Genus, of which two are found in Mexico’s freshwater systems. The Koi is native to Japan and has been bred in captivity since the early 19th century. There are currently over one hundred different breeds that vary in coloration, patterning and scalation. The Koi has important symbolic meaning in traditional Chinese culture and Japanese culture. Relevant accounts can be seen in various ancient Chinese poetry and literature since the Jin Dynasty, while in Japan, it is closely associated with the country’s national identity, often as a symbol of luck, prosperity, and good fortune.
Koi have a deep, elongated stout body with a thick and short caudal peduncle. Today’s breed varies greatly in color variations of black, blue¸ cream, gold, orange, red, silver, white and yellow with gray or bronze anal, lower caudal lobe and pelvic fins. Their head is broadly triangular with a broad space between the very large eyes, and long snout, a mouth that ends just before the eyes and two barbels on each side of the upper jaw. They have pharyngeal teeth in their throats that are utilized to crush food. They have a keen sense of hearing and smell. Morphologically Koi are very similar to the Common Carp and their anal fin has 2 or 3 spines, the first of which is serrated, and 18 to 23 rays; their caudal fin has 17 to 19 rays and is deeply forked; their dorsal fin has 3 or 4 spines, the first of which is serrated, and 18 to 22 rays and a long base; their pectoral fins have 15 to 17 rays; and their pelvic fins are broad and short. They have 37 to 47 gill rakers. They are covered with small scales except on the head. Their lateral line is complete.
The Koi is a coldwater fish that thrives in waters between 15oC (59oF) and 25oC (77oF). They can tolerate brackish waters. During cold water episodes below 10oC (50oF) their metabolic rates slow significantly and they stop eating. Koi are a gregarious schooling species that are found in ditches, lakes, ponds, reservoirs and rivers that have either no water flow or very limited water flow at depths up to 20 m (66 feet). They reach a maximum of 1.0 m (3 feet 4 inches) in length. Koi are bottom feeding omnivores that consume algae, aquatic insects and plants. Due to their colorations they are prone to predation with by a variety of birds and mammals (badgers, cats, foxes, hedgehogs, mink, otters, and racoons). Koi have the ability to survive and adapt to many climates and water conditions, allowing them to be propagated in many new locations. Reproduction occurs in annual cycles. Each female spawns with several males and deposits vast quantities of eggs. The eggs are sticky and attach themselves to the bottom substrate. A large majority of the eggs are consumed by cannibalism. Their larvae are pelagic. They are reasonably intelligent and capable of recognizing the person that feeds them. They are subject to large kills attributed to Carp Oedema Virus (CEV) and Koi Herpesvirus (KHV). They have extended lifespans and can achieve ages over 100 years; the oldest documented fish was age 230.
The Koi was introduced to Mexico and is a resident of the freshwater systems. They are common but their specific ranges have not been well documented.
The Koi is most likely confused with the Common Carp, Cyprinus carpio (silvery body with red anal, lower caudal lobe and pelvic fins) and the Goldfish, Carassius auratus (lack prominent chin barbels; smaller in stature; wide variety of body shapes and fin and tail configurations).
From a conservation perspective the Koi is currently considered to be of Least Concern with stable, widely distributed populations. Under proper conditions they have rapid growth rates and explosive populations. Globally, they are the mostly widely used decorative fish, utilized in outdoor koi ponds, water gardens and aquariums. They have undergone a massive global explosion due to accidental and deliberate releases in the wild. In many areas of North America, Koi have been introduced into man-made water bodies to keep water-borne insect larvae under control They are highly invasive and in some areas are considered to be pests. Their introductions have had adverse effects on local environments, eroding water quality and killing off native fishes and plants. Efforts to eradicate them from certain locations has been expensive and generally unsuccessful. They are raised by aquaculture in China and have been used by humans as a food fish since the 5th century BC. Today they are raised mostly for sale as ornamental fish by the aquarium trade. Collection Koi has become a social hobby with one fish being sold for $2,000,000 in 2018. The weaker poorly colored fish are used as a live food fish for larger fish maintained in captivity.