The problems with pin bones: Intermuscular bone development and function in salmonids and their implications for aquaculture

A healthy skeletal system is fundamental to fish welfare and performance and a key physiological feature of a robust fish. The presence of skeletal deformities in farmed salmonids is a persistent welfare problem in aquaculture, and one which threatens to impede industry growth. Deformities of the fine bones of fish, such as ribs and intermuscular bones (IBs), have received less attention than vertebral body deformities, despite their potential to compromise fish welfare and product quality. IBs, commercially known as pin bones, are small spicule-like bones embedded in the muscle fillets of salmonids, cyprinids and other basal teleost species. In farmed basal teleosts, they impact fish processing, have negative effects on the economic value of fish and present a potential consumer health concern if ingested. Current understanding of IB development and function in teleosts has mostly relied on morphological research. More recently, advances in our understanding of molecular mechanisms of IB development in cyprinids have been made, largely due to the exploration of breeding IB-free fish for use in aquaculture. In this review, we explore the existing literature on IBs in teleosts, highlight the points of contention within this field of research and identify the significant knowledge gaps about the development and function of salmonid IBs. To our knowledge, there is no available research on the function of IBs and scarce research concerning IB development in salmonids. Future research on teleost IBs would benefit from the use of consistent terminology to facilitate interdisciplinary collaboration and identify research outputs in this field.