Basking shark feeding on plankton in Gunna Sound, Coll, Inner Hebrides, Scotland
The west coast of Scotland is one of the best places in the world, along with my home region of the SW of England, for seeing basking sharks, the second largest fish in the world. They can grow up to 10m (33ft) long. They are an open water shark, but move closer to shore in summer to feed on the plankton bloom. They are usually solitary, but occasionally gather in aggregations of 100 or more where there are large concentrations of plankton, usually where there are tidal fronts where different water masses meet. They are filter feeders, and in 1 hour they can filter 1.5 million litres (330,000 gallons) of water through their gills. They are highly migratory, but long-distance tracking of individuals only began recently, and it is still unknown whether they migrate between lower and higher latitudes, or between deep and shallow water. Their livers contain a large proportion of oil typical of deepwater sharks, which may indicate that they spend some time in deep water. Very little is known about their breeding. They probably mature late and reproduce slowly, making them particularly vulnerable to overfishing, especially as fisheries catch more females than males. They were once fished commercially on a small scale around Scotland for their huge livers, which contain oils formerly used in various industries, with a peak recorded catch of 250 sharks in 1947. But in response to dwindling numbers the basking shark has been fully protected since 1998.
Because they swim at the surface, these magnificent sharks are easily harmed, either deliberately or accidentally. Currently, potential threats include bycatch in fishing nets, and disturbance or impact by jet-skis, speedboats and other vessels. Globally its conservation status is currently listed as vulnerable.
- © 2012 Duncan Murrell
- Image Size
- 1132x850 / 540.8KB
- Contained in galleries
- From the Isle of Mull to the Small Isles via Coll and Lunga