Goldfish

The three-second goldfish memory is a myth. Culum Brown, a fish cognition researcher at Macquarie University, notes that the supposed span is 2 seconds in some tellings and 10 in others, but always short.

Goldfish memories can last weeks, months and even years, and they can keep memories for at least three months.

At Plymouth University, goldfish learned to push a lever for food. When the lever worked for only one hour a day, they learned to press it at the right time.

Goldfish have been taught to escape nets and to navigate mazes, and they can repeat these tasks weeks and even months later.

Goldfish use vision to find and remember landmarks, which helps them orient themselves.

Goldfish are native to eastern Asia, including China, and from China the species spread to most of the world.

A DNA study of 234 goldfish concluded that Chinese goldfish descend through the female line from native southern Chinese Carassius auratus, especially lineages from the lower Yangtze River.

The same study cites a record from China's Tsin dynasty (265 to 419 AD) as the earliest recorded use of goldfish.

Hangzhou and Jiaxin in Zhejiang are suggested as the likely area of domestication, and the study proposes the Grass-goldfish as the first domesticated breed.

Goldfish reached Japan around 1502 and Europe around 1700.

Goldfish that are released into the wild revert to a yellow-orange colour after a few generations.

Adult goldfish measure 15 to 45 cm according to Animal Diversity Web, while the US Geological Survey gives a maximum length of 410 mm.

Captive goldfish typically live 5 to 10 years, and the US Geological Survey lists a reported maximum of about 30 years.

The oldest goldfish on record is Tish, won at a fairground stall in 1956 by seven-year-old Peter Hand near Thirsk in the United Kingdom. She died on 6 August 1999 after about 43 years.

The earliest recorded releases of goldfish in the United States date to the late 1600s, probably intentional releases by settlers.

Records of goldfish exist in every US state, and the earliest listed observation is from Massachusetts in 1833.

Goldfish tolerate high turbidity, temperature swings, low dissolved oxygen and a wide pH range, and they are more tolerant of aquatic pollution than most native North American fishes.

They tolerate water from 0 to 10 °C, hibernating in winter when it falls below 10 °C, and can survive up to about 30 to 40 °C.

A female typically spawns 2,000 to 4,000 eggs at a time.