There are probably more than you would think, up to 7 different species. Don’t panic though, they dive deep, up to 121m in some cases, and they’re mostly hunting small fish such as sardines and mackerel. Sightings are quite rare, and Portugal has a safe history of no recorded shark attacks. Several sightings have been caught on camera over recent years, and with miles of rugged coastline, it’s no surprise that these sightings get recorded.

Basking sharks (Cetorhinus maximus) are a migratory species of shark that can be found in every temperate ocean that exists in the world, even the Mediterranean Sea. This is primarily because they follow concentrations of zooplankton to feed, and these concentrations have been known to swell during the summer in each hemisphere, which makes them a large and tasty food source for basking sharks to feed on.

Second largest shark - These are enormous creatures and are the second largest living shark - only the Whale Shark is bigger - and one of three plankton-eating species. Adults can reach around an average of 8m in length and are capable of opening their mouths to 1m wide! Colouring is a mottled greyish-brown, with the inside of the mouth being white in colour.

However, they are mainly found in British coastal waters between May and October. Most basking sharks live in cool to moderate waters, but some travel as far as North Africa, and have even been spotted off Portuguese coasts, and studies show evidence that some basking sharks do undergo transatlantic migration. Nevertheless, some of these sharks retain their unpredictable nature by remaining in Irish and British waters during the winter.

This is a slow-moving filter feeder, often seen with its mouth agape as it cruises for plankton, and contrary to common belief, it is actually capable of closing its mouth! Its name derives from its habit of feeding at the surface, appearing to be basking in the warmer surface water. It has adaptations for filter-feeding - opening that enormous mouth and with highly developed gill rakers, they catch plankton as water filters through. They have a lot of very small teeth too - as many as 100 per row, which all slope backwards - and has the smallest brain weight of all sharks, which might account for their relatively passive lifestyle!

Temperature - They live in most of the world's oceans, including the Mediterranean Sea. Basking sharks like water between 46°F and 58°F, but have seen in even warmer waters.

These large sharks are seen as docile, gentle giants, posing no harm to humans. There has been one recorded incident where a basking shark reportedly caused the death of humans - in 1937 a breaching basking shark capsized a boat in Carradale Bay in Kintyre, and unfortunately, 3 of the 5 passengers onboard drowned.

Isle of Man connection - Every summer, from mid-May to mid-August, mighty basking sharks descend upon the Isle of Man, with most sightings being reported within 1km of land along a 40km stretch of easily accessible coastline on the west and southwest of the Island.

In April 2022, a charity called the Manx Whale and Dolphin Watch took over the public sightings scheme for basking sharks in Manx waters but have since ceased operating due to falling numbers of sharks, and all tagging/DNA sampling in Manx waters has been taken over by Irish scientists, who have successfully deployed off Achill Island, in Ireland.

When the seas are calm and the weather is settled and sunny, the plankton concentrates at the surface of the sea and the basking sharks feed on this plankton close inshore. You may even see basking shark courtship activity from the coast with the naked eye or binoculars, or even breaching.

Despite sightings, globally the basking shark is decreasing in numbers and is therefore on the International Union of Conservation of Nature’s Red List, and boat owners are warned to exercise caution when using their vessels to avoid damaging them, though I would think a creature that big surely can’t be missed!


Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan