The Goldfish

The goldfish (Carassius auratus auratus) is a freshwater fish in the family Cyprinidae of order Cypriniformes. It was one of the earliest fish to be domesticated, and is one of the most commonly kept aquarium fish.

A relatively small member of the carp family (which also includes the koi carp and the crucian carp), the goldfish is a domesticated version of a less-colorful carp (Carassius auratus) native to east Asia. It was first domesticated in China more than a thousand years ago, and several distinct breeds have since been developed. Goldfish breeds vary greatly in size, body shape, fin configuration and coloration (various combinations of white, yellow, orange, red, brown, and black are known).

History

Starting in ancient China, various species of carp (collectively known as Asian carps) have been domesticated and reared as food fish for thousands of years. Some of these normally gray or silver species have a tendency to produce red, orange or yellow color mutations; this was first recorded in the Jin Dynasty (265–420). A drawing in brown ink on an ocher background. A rectangular glass aquarium tank sits on a wooden stand with carved, curled legs, and contains two fish as well as plants with wavy grass-like leaves.

A western aquarium of the 1850s of the type that contained goldfish among other coldwater species

During the Tang Dynasty (618–907), it was popular to raise carp in ornamental ponds and watergardens. A natural genetic mutation produced gold (actually yellowish orange) rather than silver coloration. People began to breed the gold variety instead of the silver variety, keeping them in ponds or other bodies of water. On special occasions at which guests were expected they would be moved to a much smaller container for display.

By the Song Dynasty (960–1279), the domestication of goldfish was firmly established. In 1162, the Empress of the Song Dynasty ordered the construction of a pond to collect the red and gold variety. By this time, people outside the imperial family were forbidden to keep goldfish of the gold (yellow) variety, yellow being the imperial color. This is probably the reason why there are more orange goldfish than yellow goldfish, even though the latter are genetically easier to breed.

During the Ming Dynasty (1368-1644), goldfish also began to be raised indoors, which led to the selection for mutations that would not be able to survive in ponds. The occurrence of other colors (apart from red and gold) was first recorded in 1276. The first occurrence of fancy tailed goldfish was recorded in the Ming Dynasty. In 1603, goldfish were introduced to Japan, where the Ryukin and Tosakin varieties were developed. In 1611, goldfish were introduced to Portugal and from there to other parts of Europe.

During the 1620s, goldfish were highly regarded in Southern Europe because of their metallic scales, and symbolized good luck and fortune. It became tradition for married men to give their wives a goldfish on their one year anniversary, as a symbol for the prosperous years to come. This tradition quickly died, as goldfish became more available, losing their status. Goldfish were first introduced to North America around 1850 and quickly became popular in the United States.

Related species

Goldfish were bred from Prussian carp (Carassius auratus gibelio) in China, and they remain the closest wild relative of the goldfish. Previously, some sources claimed the Crucian carp (Carassius carassius) as the wild version of the goldfish. However, they are differentiated by several characteristics. C. auratus have a more pointed snout while the snout of a C. carassius is well rounded. C. gibelio often has a grey/greenish color, while crucian carps are always golden bronze. Juvenile crucian carp have a black spot on the base of the tail which disappears with age. In C. auratus this tail spot is never present. C. auratus have fewer than 31 scales along the lateral line while crucian carp have 33 scales or more.

When found in nature, goldfish are olive green. Introduction of goldfish into the wild can cause problems for native species. Goldfish can hybridize with certain other species of carp. Within three breeding generations, the vast majority of the hybrid spawn revert to their natural olive color. The mutation that gave rise to the domestic goldfish is also known from other cyprinid species, such as common carp and tench. Koi may also interbreed with the goldfish to produce a sterile hybrid fish.

There are many different varieties of domesticated goldfish. Fancy goldfish are unlikely to survive in the wild because of their bright fin colors; however the hardier varieties such as the Shubunkin may survive long enough to breed with wild cousins. Common and comet goldfish can survive, and even thrive, in any climate that can support a pond.

Reproduction

Goldfish may only grow to sexual maturity with enough water and the right nutrition. Most goldfish breed in captivity, particularly in pond settings. Breeding usually happens after a significant temperature change, often in spring. Males chase females, prompting them to release their eggs by bumping and nudging them. A pregnant goldfish is called a "twit".

Goldfish, like all cyprinids, are egg-layers. Their eggs are adhesive and attach to aquatic vegetation, typically dense plants such as Cabomba or Elodea or a spawning mop. The eggs hatch within 48 to 72 hours.

Within a week or so, the fry begins to assume its final shape, although a year may pass before they develop a mature goldfish color; until then they are a metallic brown like their wild ancestors. In their first weeks of life, the fry grow quickly—an adaptation born of the high risk of getting devoured by the adult goldfish (or other fish and insects) in their environment.

Some highly bred goldfish can no longer breed naturally due to their altered shape. The artificial breeding method called "hand stripping" can assist nature, but can harm the fish if not done correctly. In captivity, adults may also eat young that they encounter.