Question
Why do domesticated fish have a size dependent on their living space? I thought goldfish were supposed to be fairly small but they keep finding giant ones in Australian rivers. If one was to buy a big enough tank, could one theoretically convince a goldfish to grow to a much bigger size?
Answer
The size of domesticated fish, such as goldfish, can indeed be influenced by the size of their living space. This phenomenon is observed across various fish species and is linked to both behavioural and physiological factors.
Influence of Tank Size on Fish Growth
Behavioural and Physiological Effects: Studies on zebrafish and Siamese fighting fish show that tank size significantly affects fish behaviour and welfare. Fish in larger tanks tend to be more active and exhibit fewer abnormal behaviours, suggesting that a larger living space can promote better overall health and potentially support larger growth (Maierdiyali et al., 2020; Clark-Shen et al., 2024).
Space and Activity: Larger tanks provide more space for movement, which can lead to increased activity levels. This increased activity can contribute to better muscle development and overall growth, as seen in studies with Siamese fighting fish (Clark-Shen et al., 2024).
Potential for Growth in Larger Tanks
Growth Potential: While the specific growth potential of goldfish in larger tanks isn’t directly addressed in the provided studies, the general principle that larger living spaces can support larger body sizes is supported by research on other fish species. For example, coastal pike use more space as they grow larger, indicating a relationship between available space and body size (Dhellemmes et al., 2023).
In summary, the size of a fish’s living space can influence its growth and behaviour. Larger tanks can promote better health and potentially larger sizes in domesticated fish like goldfish. Therefore, if one provides a sufficiently large tank, it is theoretically possible for a goldfish to grow to a much larger size than typically seen in smaller tanks.
References
Dhellemmes, F., Aspillaga, E., Rittweg, T., Alós, J., Möller, P., & Arlinghaus, R., 2023. Body size scaling of space use in coastal pike (Esox lucius) in brackish lagoons of the southern Baltic Sea. Fisheries Research. https://doi.org/10.1016/j.fishres.2022.106560
Maierdiyali, A., Wang, L., Luo, Y., & Li, Z., 2020. Effect of Tank Size on Zebrafish Behaviour and Physiology. Animals : an Open Access Journal from MDPI, 10. https://doi.org/10.3390/ani10122353
Clark-Shen, N., Tariel-Adam, J., Gajanur, A., & Brown, C., 2024. Life beyond a jar: Effects of tank size and furnishings on the behaviour and welfare of Siamese fighting fish (Betta splendens). Animal Welfare, 33. https://doi.org/10.1017/awf.2024.67
