What is the largest species of shark?

The whale shark, up to about 18 metres - the largest fish alive - and it eats plankton. It feeds by suction rather than by ramming forward with its mouth open, drawing in water and straining it through filter pads, and its thousands of tiny teeth appear to do nothing at all.

Each one carries a unique pattern of spots behind the gills, and researchers identify individuals from photographs using software originally written to match star fields - an algorithm developed at NASA for identifying patterns in astronomical images, repurposed to run a shark census from tourist snapshots.

Very little of the life cycle is known. A single pregnant female caught in 1995 carried around 300 pups at different stages of development, which established that they hatch eggs internally and give birth to live young over an extended period - and that is essentially the entire direct evidence. Where they breed has never been found. They are slow to mature, long-lived, and endangered, largely from fishing and ship strikes.