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Goldfish

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The goldfish, known scientifically as *Carassius auratus*, is a freshwater fish within the family Cyprinidae.

Carassius auratus
Carassius auratus

These fish are among the most popular pets kept in indoor aquariums worldwide. However, they can also become invasive pests in parts of Australia and North America if released into the wild. While they are often seen as small ornamental animals, they are actually complex organisms with unique biological traits. Their history is a long story of human selection and changing environments.

The goldfish originated from natural color mutations in silver carp. In Imperial China, specifically during the Jin dynasty (266–420), people first recorded these red, orange, or yellow mutations. During the Tang dynasty (AD 618–907), people raised these carp in ornamental water gardens. Eventually, people began selectively breeding the gold varieties instead of the silver ones. By the Song dynasty (AD 960–1279), this domestic breeding was firmly established. During the Ming dynasty (1368–1644), goldfish moved from outdoor ponds to indoor settings. This change allowed breeders to select for mutations that might not survive in the wild, such as specific fin shapes.

Ryukin goldfish plate
Ryukin goldfish plate

Goldfish exhibit incredible variety due to centuries of selective breeding. They differ greatly in body shape, fin configuration, and coloration. Common colors include white, yellow, orange, red, brown, and black.

Black Moor Goldfish
Black Moor Goldfish

There are many distinct breeds, such as the Ryukin or the Black Moor. Some varieties have specialized features like the Bubble Eye or the Celestial eye. Because of these different shapes, some highly bred goldfish can no longer breed naturally. They may require a manual method called "hand stripping" to assist in reproduction.

Bubble Eye goldfish
Bubble Eye goldfish

Understanding the biology of the goldfish requires looking at their unique senses. Goldfish are tetrachromats, meaning they possess four types of cone cells. These cells allow them to see red, green, blue, and ultraviolet light.

Celestial eye goldfish
Celestial eye goldfish

Their hearing is also highly developed and well-studied. They use two otoliths to detect the motion of sound particles. Additionally, Weberian ossicles connect their swim bladder to these otoliths. This connection helps them detect sound pressure. This combination of senses makes them very responsive to their environment.

Reproduction in goldfish is a process driven by environmental changes. Breeding often occurs in spring after a significant change in water temperature. Males will chase gravid females, which are females carrying eggs. The males nudge and bump the females to prompt them to release eggs. These eggs are adhesive and attach to aquatic plants like *Elodea*.

Goldfisheggs
Goldfisheggs

The eggs typically hatch within 48 to 72 hours. The newly hatched fry are often a metallic brown color. They grow very quickly during their first weeks to avoid being eaten. It can take a full year for them to develop their mature adult colors.

Goldfishfry
Goldfishfry

Goldfish are surprisingly intelligent and possess strong cognitive abilities. They have associative learning skills, allowing them to link certain actions with rewards. For example, they can learn to push a lever to receive food.

They can also distinguish between different shapes, colors, and sounds. Contrary to the myth of a three-second memory, goldfish can remember things for at least three months. They can even recognize individual humans. Many owners notice their fish swim to the glass to "beg" for food when they approach. This shows they have learned to associate humans with feeding.

In terms of physical scale, goldfish can reach impressive sizes. While wild goldfish usually grow between 12 cm and 22 cm, they can reach up to 41 cm.

Domesticcometgoldfish
Domesticcometgoldfish

A pet's size is influenced by its breed and its container. While a common myth says they grow to fit their tank, the tank size actually affects their growth rate. Historical records show the scale of the goldfish industry was massive. In the late 19th century, Henry Bishop was called the "Gold Fish King." His operations in Baltimore sold more than one million goldfish every year. This highlights how deeply integrated these fish have become in human culture and commerce.

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🖼️ Images & Media (42)
File:Carassius auratus 197778318.jpg
Carassius auratus 197778318.jpg
File:Carassius auratus.jpg
Carassius auratus.jpg
File:Goldfish in Fish Swimming Amid Falling Flowers by Liu Cai (cropped).jpg
Goldfish in Fish Swimming Amid Falling...
File:Carassius gibelio male 2021 G1.jpg
Carassius gibelio male 2021 G1.jpg
File:1856aquariumfresh.png
1856aquariumfresh.png
File:Ryukin goldfish plate.jpg
Ryukin goldfish plate.jpg
File:CarassiusCarassius8.JPG
CarassiusCarassius8.JPG
File:Goldfisheggs.JPG
Goldfisheggs.JPG
File:Goldfishfry.JPG
Goldfishfry.JPG
Goldfish in a bowl - Hakone - 2025 Aug 1.webm
File:%E3%83%AF%E3%82%AD%E3%83%B320120701.JPG
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File:Black Moor Goldfish.jpg
Black Moor Goldfish.jpg

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