Published online by Cambridge University Press: 11 May 2009
Moreau (1876), Bohr (1894), and Fänge (1953) are among those authors who have demonstrated that the swimbladder walls of certain fish are highly impermeable to gases. This property assists in the maintenance of high partial pressures of gases in the swim-bladder and enables physoclist fish to use the swimbladder as a buoyancy mechanism, often at great depth. It has been shown experimentally that the swimbladder contains a high percentage of oxygen (Fänge, 1953; Kanwisher & Ebeling, 1957) and that this percentage increases with depth in most fish (Scholander & Van Dam, 1953; Scholander, 1954). Diffusion of gas through a tissue increases with increasing partial pressure difference across the tissue (Krogh, 1919). This may be as high as 10–20 atm in inshore gadoids such as the saithe, Pollachius virens (L.) or 50–60 atm in mesopelagic fish (Kanwisher & Ebeling, 1957). Thus low permeability to oxygen is required if the swimbladder is to be used as a buoyancy mechanism at any depth.