The goldfish, Carassius auratus, is a popular aquatic pet. Although many goldfish are kept in groups in ponds, some are also kept solitarily in tanks, which raises the question of whether this species requires social contact to maximize its welfare and enable it to thrive.
Goldfish originate from crucian carp, Carassius carassius, and were domesticated in ancient China around a thousand years ago. Since then, this fish has undergone a huge amount of artificial selection which has resulted in a great variety of morphological features, such as differences in the shape of the body, eye, tail fin, and dorsal fin.
Crucian carp are reported to shoal, forming large groups and synchronizing their swimming speed to remain together. However, this species has not been found to engage in social learning, suggesting that this, among other social behaviors, is something that developed in goldfish since their domestication.
The Social Life of Goldfish
Goldfish are highly motivated to shoal and will copy their conspecifics in searching for food and avoiding predators. Social learning is important to goldfish – one study found that individuals could learn to navigate a maze more quickly when they had watched another fish complete it.
Because we are such visual animals, it is easy to forget that other creatures communicate using a variety of sensory stimuli. As well as using visual cues for shoaling and reproduction, individuals can also identify each other using olfactory cues such as pheromones, which proves useful when water clarity is poor.
Although goldfish are a non-vocal species, research has found that they can detect some sounds, such as that produced when a fish flips its tail. Goldfish have been found to orient towards conspecifics that are swimming, possibly due to them receiving tactile and visual cues from the movement.
What Does This Mean for Keeping Goldfish?
Goldfish need to be provided with sufficient space to move away from conspecifics if they desire, and their enclosures should accommodate the size of individuals when they are fully grown, even if they have not attained these lengths yet.
Although these fish are not usually aggressive, if there is a shortage of food they may display agonistic behaviors towards each other – so ensuring that they always have plenty on which to forage is essential to maintain good relationships within the pond or tank.
