To put it more then simply, no the swim bladder is not a disease. It is an organ, also known as the gas bladder largely used for buoyancy in many of the fishes we are familiar with. Of course given the wide diversity of fishes there is variations on this for example; Polypterus (bichir) use it as an equivalent of a lung (Pelster, 2021) and it’s pretty well known sharks lack this organ (Yalowitz & Feriuson, 2006).

It’s a rather curious organ, as ichthyologists or even biologists we learn about it pretty early during our university undergraduate degree. Maybe like me it’s a lot of physiology that involves biochemistry so I phase out a little at the niche aspects.

There are also two main types of fishes, Actinopterygii fishes to be correct I guess depending on this organ:

Physostomes: This is where there is a direct duct/tube from the gas/swim bladder to the gut. This includes what seems to be groups of fishes that branched out earlier; carps, catfish, eels, Polypterus. It is largely assumed they fill up the organ by gulping for air (Solberg & Kaartvedt, 2014’Sundnes & sand, 1975).

Physoclisti: These species lack a duct, the gas is secreted into the organ (Ross, 1979).

Maybe more to the point of this article, it is an organ with an important purpose.

What about the disease some might ask?

It’s no different from heart disease, it’s anything causing an issue with an individual organ.

Honestly I think I can’t state much without asking people to read this paper first: https://weu-az-web-cdnep.azureedge.net/mediacontainer/medialibraries/midlandvetsurgery/documents/buoyancy-disorders-of-ornamental-fish.pdf

It’s brilliant just for showing the gross anatomy, gross as in just the anatomy as it’s not simple. Given the funding of fish pathology how much do we know? I feel sometimes it just shows we are jumping at strings. Much of what we see in goldfish I think is anatomical but other fishes might have complex answers.

What else?

Well when people see this they will be asking why does this fish spin, why does it move how it does? My fish is acting different?

The short answer is like with most animals that strange behaviours can be a sign of many things. If your spatial awareness and balance is gone is the answer always the inner ear, maybe our equivalent? I must always ask can we define the difference? Beyond goldfishes where it is likely the cause due to their shape, I’m not sure but maybe it seems less likely the swim bladder.

Neurological disorders (Burton & Burgess, 2023) can cause issues with balance that could look like swim bladder disorders such as those caused by malnutrition or oxygen starvation. Both of these examples either limit those elements or compounds required for neurological function or in the case of oxygen, the starvation of that can cause areas of the brain to die as they can no longer respire.

There is so little maybe we do know about fish pathology and for individual situations then there is individual solutions, another aspect is when researching fishes it comes up with mostly how to eat fish haha.

References:

Burton, E. A., & Burgess, H. A. (2023). A Critical Review of Zebrafish Neurological Disease Models− 2. Application: Functional and Neuroanatomical Phenotyping Strategies and Chemical Screens. Oxford Open Neuroscience, 2, kvac019.

Pelster, B. (2021). Using the swimbladder as a respiratory organ and/or a buoyancy structure—Benefits and consequences. Journal of Experimental Zoology Part A: Ecological and Integrative Physiology, 335(9-10), 831-842.

Ross, L. G. (1979). The haemodynamics of gas resorption from the physoclist swimbladder: the structure and morphometrics of the oval in Pollachim virens (L). Journal of Fish Biology, 14(3), 261-266.

Sundnes, G., & Sand, O. (1975). Studies of a physostome swimbladder by resonance frequency analyses. ICES Journal of Marine Science, 36(2), 176-182.

Solberg, I., & Kaartvedt, S. (2014). Surfacing behavior and gas release of the physostome sprat (Sprattus sprattus) in ice-free and ice-covered waters. Marine biology, 161, 285-296.

Wildgoose, W. H. (2007). Buoyancy disorders of ornamental fish: A review of cases seen in veterinary practice. Fish Vet. J, 9, 22-37.

Yalowitz, S., & Ferguson, A. (2006). Sharks: Myth and mystery. Monterey Bay Aquarium.