Goldfish (Carassius auratus) originated in eastern Asia including China, Hong Kong, Korea, and Taiwan. From China, the range of this species expanded north to most of the world. Goldfish have been introduced in the United States in Kansas, the northern part of Oklahoma, Washington, New Mexico, and four of the five Great Lakes: Lake Erie, Lake Michigan, Lake Huron, and Lake Ontario. They are also extant in western Canada in the Rocky Mountains, southern France, northern Italy, South Africa, Madagascar, and southern India. (Huckstorf and Freyhof, 2013; Lorenzoni, et al., 2007)
Goldfish mainly occupy fresh inland waters and wetlands in temperate regions. They tend to live in bodies of water with slow or no movement. This includes rivers, lakes, ponds, streams, marshes, bogs, and swamps. They can live in salinities up to 17 parts per trillion (ppt) but cannot thrive properly in waters above 15 ppt salinity. Luz et al. (2008) conducted a study on goldfish behavior in different salinities, and found that goldfish exhibit a higher tolerance to low salinities than high salinities.
Goldfish typically live at depths of 10 meters (range 1-20 meters). Goldfish are able to live in temperatures 0-10°C but can tolerate temperatures as high as 30-40°C. They are more common in water with pH levels between 5.5-7.0 but may tolerate waters with pH levels up to 10.5. (Brown, et al., 2019; Huckstorf and Freyhof, 2013; Lorenzoni, et al., 2007; Luz, et al., 2008)
Goldfish hatch with dark, pigmented scales, but they depigment 2-3 months after hatching. Adult goldfish are a yellow-orange color and possess transparent fins. In captivity, goldfish can come in colors like red, black, and silver due to a variety of factors including diet, light, and illness. If released back into the wild, the goldfish will revert to the yellow-orange color after a couple of generations.
Goldfish can grow to 15-45 centimeters total length. At hatching, they are 4.5-5.0 millimeters in length. As adults, they can weigh from 0.1-3.0 kilograms. Female goldfish tend to have rounder bodies while males tend to have slimmer, oval-shaped bodies. Wild goldfish often grow bigger than domesticated goldfish because of their richer environment with more resources and space to swim.
Goldfish grow to have 5 types fins including two pectoral fins, two pelvic fins, one anal fin, one dorsal fin, and one caudal fin which all help goldfish swim efficiently through their environment. Goldfish have 25-31 cycloid scales along the lateral line. There are three cycloid scale types, based on color, reflectivity, and transparency: matte, metallic, and nacreous. Matte scales are transparent and have little to no color. Metallic scales are shiny and turn black when a goldfish is injured. Nacreous scales are semi-transparent and are most commonly black, blue, or white.
Goldfish are ectothermic, meaning they rely on heat from their environment to regulate their body temperature. (Kajishima, 1975; Lorenzoni, et al., 2007; Omori and Kon, 2018)
When goldfish eggs are spawned into the water, the chorion is formed around the egg and adheres the eggs to an aquatic plant or somewhere similar where they will be stored until hatching. Fertilized goldfish eggs progress through typical deuterostome stages as the embryos divide and develop. Goldfish-specific features are visible in the gastrula period when tail buds become present. From that period onward, the tail bud becomes longer, and the pectoral fins develop. The eggs are 1.2-1.5 millimeters long. After hatching, they are around 4.5mm in length. Goldfish larvae can grow to 6 centimeters after one year and continue to grow until they become adults, which can take around 3 years. The rate of growth then slows down once in adult stage, to about 2.5 cm per year. In captivity, goldfish grow to about 2.5-15cm in length. Wild goldfish have a higher growth rate with some reaching 18cm in length at 1 year old. They can reach a maximum size of 45cm and 2kg.
Goldfish have indeterminate growth in the wild, meaning they do not stop growing. (Beatty, et al., 2017; Stauffer, et al., 1995; Tsai, et al., 2013)
Goldfish are polygynandrous, with males and females each having multiple mates in a season. When females are with eggs, they release a pheromone into the water to signal males to produce milt, or sperm. When females spawn eggs, males approach the female. Both sexes will pursue one another by chasing and bumping each other. Males then release milt into the water near the eggs to fertilize them. (Agosta, 1994; "Species Profile: Koi and Goldfish", 2004)
Goldfish breed seasonally from February to June, but temperature drives the range. The minimum temperature goldfish start to breed is 10 °C. They spawn once each month during this period. Both male and female goldfish become sexually mature at 3-4 years of age. Goldfish are iteroparous and oviparous.
Female goldfish spawn eggs into the water, then the eggs get fertilized externally with milt from multiple male goldfish. Fertilization is external. Female goldfish normally spawn 2000-4000 eggs at a time, although the highest number of eggs spawned was 380,000. The weight as larvae ranges between 0.15-0.17 grams. Goldfish eggs hatch in 2-9 days. Once hatched, larvae are independent. (Agosta, 1994; Lorenzoni, et al., 2007; Sharma, et al., 2011; "Species Profile: Koi and Goldfish", 2004)
Female goldfish carry eggs that are spawned into the water. When released into the water, the eggs are fertilized by male milt. Beyond the act of mating, males and females provide no parental care. Adult goldfish also consume their own offspring. (Lorenzoni, et al., 2007)
Goldfish usually live from 20 to 30 years in the wild and 5 to 10 years in captivity. The reduced captive lifespan is due to issues of tank size and food resources. The longest a goldfish lived in captivity was 43 years. The maximum longevity in the wild is 41 years. (Bobick and Peffer, 1993; Brown, et al., 2019; Lorenzoni, et al., 2007)
Goldfish are a social species. They form schools and communicate with conspecifics within the school. The schooling also allows them to defend against predators. Goldfish are not aggressive towards conspecifics and do not form social hierarchies. Goldfish are mobile and natatorial, typically active during dusk and dawn.
Goldfish hibernate in the winter months when water temperatures are below 10 degrees Celsius and possess sufficient oxygen. They can tolerate lower levels of oxygen for shorter periods (several months) at 2 degrees Celsius. Goldfish tolerate a wide range of water conditions and environmental stress. They can live in water salinities as high as 17 ppt. They have a tolerance to ammonia in water, which is toxic to other species. Wilkie et al. (2011) did acute toxicity tests on goldfish and determined that goldfish can tolerate 4132 micromoles (umol) of ammonia. They can withstand high turbidity levels and can tolerate high levels of water pollution.
Goldfish use pheromones to attract mates and subsequently chase and bump into one another before mating. They use their lateral line to help them detect motion in the water and communicate with surrounding goldfish by sensing natural ripples, currents, and vibrations made while swimming. (Brown, et al., 2019; Lorenzoni, et al., 2007; Stacey, 2003; Wilkie, et al., 2011)
Beatty et al. (2017) studied seasonal movement related to spawning of goldfish, and they moved 0.30 km per day, on average, in the eastern Australian Murray River. One fish moved 231.3 km over a one-year period and another fish moved 5.4 km in one day. By comparison, Kim et al. (2014) recorded average movement of 1.4 km per day in the Jangheung Dam. Goldfish in rivers will migrate to off-channel stagnant (lentic) waters to spawn during breeding season. They do not defend a territory. (Bajer, et al., 2010; Beatty, et al., 2017; Kim, et al., 2014; Lorenzoni, et al., 2007; Stauffer, et al., 1995)
A main part of goldfish perception and communication is their lateral line which is a line of sensory organs on the sides of their body. It helps them detect motion in the water around them and communicate with surrounding goldfish by sensing the natural ripples, currents, and vibrations they make while swimming. Goldfish have a hearing frequency limit of 2 to 3 kHz. Their inner ear is able to detect pressure by coupling to their gas bladder.
Goldfish are tetrachromats, meaning they can see four colors. These include red, green, blue, and ultraviolet (UV) wavelengths. UV wavelengths penetrate water better than light wavelengths, helping goldfish better sense predators and prey by water reflection. They can also use their vision to discover (and remember) landmarks in water as a method of orienting themselves.
Goldfish communicate the most through groups called schools or shoals. Being in these groups are beneficial in many ways. For example, goldfish can secrete a substance when their skin is damaged which alerts their school to help with monitoring surroundings. Goldfish use chemicals to perceive food and avoid predators throughout their environment. Monello and Wright (2001) state that goldfish are capable of learning feeding behaviors through conspecifics - that is, if they see a goldfish consuming an unusual item, others may participate in feeding too.
Female goldfish secrete pheromones to communicate to male goldfish to fertilize their eggs. This chemical stimulates the males' reproductive system to produce more milt, or fish semen. Male goldfish are more likely to discharge milt near female goldfish who are releasing pheromones than to female goldfish who are not. (Agosta, 1994; Brown, et al., 2019; Dailey and Braun, 2011; Fay, 1994; Monello and Wright, 2001)
Goldfish are opportunistic feeders. They are generalist omnivores that eat a variety of insects, eggs, plants, and crustaceans. They search widely for food throughout aquatic vegetation and sandy substrates. Richardson et al. (1995) examined gut contents of Stoneycroft Pond goldfish in Quebec and found that 45% of their diet consists of vegetation (e.g., aquatic pondweeds like Potamogeton). Insects like non-biting midges (family Chironomidae) and mosquitos (family Culicidae) made up 21% of their diet. Small crustaceans like brine shrimp (Artemia), water fleas (Daphnia magna), and zooplankton made up 4% of diet. They also consume terrestrial worms like earthworms (suborder Lumbricina) and any detritus they can find in the water. They may eat the carrion of these insects and crustaceans. Pond experiments with caged goldfish suggest that they will consume amphibian eggs, too.
In captivity, goldfish mainly consume commercial fish flakes and small vegetables like peas. Newly-hatched goldfish, also known as fry, have the same diet as adults, but in smaller portions. There are no differences in the diets of male and female goldfish. (Brown, et al., 2019; Mohammad, et al., 2018; Monello and Wright, 2001; Richardson, et al., 1995)
Goldfish can be predators to their own young by consuming their eggs. In the wild, animals such as dogs (Canis lupus familiaris), cats (Felis catus), coyotes (Canis latrans), plain-bellied water snakes (Nerodia erythrogaster), mountain lions (Puma concolor), herons (family Ardeidae), bears (family Ursidae), eastern indigo snakes (Drymarchon couperi), northern river otters (Lontra canadensis), and American bullfrogs (Lithobates catesbeianus) can be predators. To defend against predation, goldfish form large groups called schools to evade predators and warn each other with chemical signals that predators are nearby. (Brown, et al., 2019; Tsai, et al., 2013)
Goldfish eat a variety of insects, plants, and crustaceans and are consumed by various mammals. Goldfish play a role in their ecosystems by efforts of sediment bioturbation. They do this naturally by foraging, reproduction, and avoiding predators in the water. This plays a significant role in how their ecosystem functions. It can increase food supply for other organisms in their environment as well as increase and spread nutrients throughout the water.
Parasites that use goldfish as a host include endoparasites like trematodes (Metagonimus), nematodes (Contracaecum), apicomplexans (Plasmodium), flatworms (class Monogenea), parasitic cnidarians (Sphaerospora, Mitraspora), those in class Kinetoplastea (Ichthyobodo necator), and monogeneans (Dactylogyrus). Ectoparasites include fish lice (Argulus foliceaus), anchor worms (Lernaea cyprinacea), and leeches (Trachellobdella torquata). (Ahmed, 1973; Eszterbauer and Székely, 2004; Gandar, et al., 2015; Hakoyama, 2001; Tekın-Özan and Kir, 2005; Zhou, et al., 2020)
Goldfish breeding and sales are sources of income for humans. They are sold as pets and as bait for larger predatory fish. Prices for captive goldfish range from 15 cents for feeder goldfish up to $120 for rarer goldfish. Goldfish are also used for research for many toxicity tests including ammonia tolerance. (Wilkie, et al., 2011)
There are no known adverse effects of goldfish on humans.
Goldfish are a species of "Least Concern" on the IUCN Red List. They have no special status on the US Federal List, CITES, and State of Michigan List.
Threats to goldfish are limited because they are an invasive species that can withstand harmful water conditions. Due to this, goldfish are not known to be harmed by climate change or moderate levels of water pollution. One potential threat is hybridizing.
There are no conservation efforts in place but there may be efforts in place to remove goldfish from non-native areas. (Beatty, et al., 2017; Huckstorf and Freyhof, 2013; Lorenzoni, et al., 2007)
Ashanti White (author), Radford University, Sierra Felty (editor), Radford University, Bianca Plowman (editor), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
flesh of dead animals.
uses smells or other chemicals to communicate
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
active at dawn and dusk
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
an animal that mainly eats leaves.
mainly lives in water that is not salty.
An animal that eats mainly plants or parts of plants.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
Animals with indeterminate growth continue to grow throughout their lives.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
an animal that mainly eats all kinds of things, including plants and animals
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the business of buying and selling animals for people to keep in their homes as pets.
chemicals released into air or water that are detected by and responded to by other animals of the same species
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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