Frequently Asked Questions
Hyperostosis - Swollen Bones
The supraoccipital bone (upper right) and frontal bone (centre left) of a Snapper. These bones give adults the distinctive head shape. View larger image.
A leatherjacket (view species list for leatherjackets) vertebra showing hyperostosis. This bone is registered in the Australian Museum Fish Collection (AMS I.40274-001). View larger image.
A hyperostotic dorsal fin spine from a jewfish (view species list for jewfishes) bought from a fish shop in Ashfield, Sydney, New South Wales. View larger image. View image showing the anterior surface of spine.
The enlargement of particular areas of fish bones is known as hyperostosis. Translated it means "above normal bone growth". The word is derived from the Greek hyper - above, osteo - bone, and osis - suffix denoting a condition.
Hyperostosis occurs in about eighty species of fishes across at least six orders and twenty families.
Bone sites that are affected and how they grow appear to be fairly consistent within a species.
The hump on the head of an adult Snapper develops as a result of hyperostosis (view fact sheet).
The cause of hyperostosis is unknown. It has been suggested that it may be a response to pollution, or possibly a disease, however evidence suggests that it has a genetic cause.
Hyperostosis doesn't appear to have any effect on the edibility of a fish.
Further reading
- McGrouther, M.A. 1994. Swollen Fish Bones. Australian Natural History. 24(11):79.
- Smith-Vaniz, W.F., L.S. Kaufman & J. Glowacki. 1995. Species-specific patterns of hyperostosis in marine teleost fishes. Marine Biology 121:573-580.
