Blue sharks populate the waters around the Azores archipelago. They undertake long transatlantic migrations. Offshore diving with these elegant and curious animals allows to study them at arm’s length.
It’s quiet onboard, everybody stares into the ocean’s deep blue. Our Zodiac idles on the waves. Suddenly a shadow whizzes below the stern; as we look it has already disappeared in the deep.
We’re in the Atlantic between the islands Faial, Pico, and São Jorge, on a dive trip in the Azores archipelago looking for blue sharks. The skipper of our dinghy pours blood into the water. He’s wearing oilskins, and my son jokes about butcher trousers. The current takes the blood away leaving a trace on the ocean surface. There again is a shadow, then two and more… Sharks!
The night before, I haven’t slept well – sinister collective memory driving my fears. Blue sharks aren’t vicious monsters. They very rarely attack humans. Their teeth are not designed to shear. But they are still sharks.
Fabio turns on the music, Paint it Black blares from the speakers. The ocean below is several hundred metres deep. Blue sharks (Prionace glauca) like deep waters. Here they hunt fish and squid.
We take our dive gear and put on the masks. Avoiding any splash, not to scare the animals away, we glide into the water. There are five sharks circling under the boat, their blue-green backs are lit by the fleeting sunbeams.
The sharks are curious. Effortlessly they approach, make eye contact, and pass at arm’s length. Eventually they try to scratch their backs. Sharks of that size are several years old. Where might their journey across the Atlantic ocean have taken them?
Transatlantic Movements of Blue Sharks
The sharks we see are around two and a half metres long, they are mature. These animals undertake long transatlantic migrations: they swim to west African waters or towards the Caribbean. Indeed, blue sharks live in all temperate and tropic waters from Norway to South Africa, from Newfoundland to Argentina, also in the Pacific ocean, and the Mediterranean. They are fast swimmers.
Often the sharks will seasonally return to the Azores which are a pupping ground. Gestation period is nine to twelve months. Thereafter, they give birth to live animals, not eggs.
Some of the sharks have scars on the back or nose. These marks might be the result of unfortunate encounters with enemies – tiger sharks or great whites – or biting by males during reproduction.
Blue sharks are classified as near threatened on the IUCN red list. Often they end as by-catch on fishing boats, or as a trophy: up to twenty million blue sharks are killed per year.