The shoal rises to just below the surface and apparently basks in the sun.
Nobody knows why.
Fish are influenced by changes in temperature. Together they have been establishing a research project on the huge fish off the Scottish island of Arran. Only its close relative the whale shark, found in tropical waters, is bigger. What the researchers are coming to understand is that while the fish might be under no threat, there are fewer of them. Officially there is no decline in the population.