A newly compiled marine atlas details the array of discoveries made in the region by the Hebridean Whale and Dolphin Trust between 2003 and last year.
The charity has so far carried out around 200 research expeditions on its specialised yacht Silurian, staffed by both scientific researchers and more than 700 paying volunteers.
The surveys have previously established the Hebrides is a vital feeding ground for minke whales and basking sharks and one of the most important areas for harbour porpoises in Europe. Research has also found the region supports the UK’s only resident population of killer whales, or orca, which is likely to become extinct within a generation as no calves have ever been seen.
So far 23 species of whales, dolphins and porpoise – collectively called cetaceans – have been recorded in the Hebrides, a quarter of the global total.
Biologist and TV presenter Liz Bonnin, who is also the charity’s patron, said: “It is increasingly clear that the Hebrides is a truly special place for cetaceans and basking sharks, and that we need to do far more to protect them and their environment.”