Aldabra experienced its first known whale beaching inside the lagoon at Passe Hoareau on the north coast late last week.

Returning from a field camp, rangers came across two stranded adult humpback whales and one still-swimming juvenile. They appear to have come into the lagoon on the high spring tide and become stuck on the reef as the tide receded.

Aldabra has been experiencing record numbers of humpback sightings this year, particularly adults with calves, but these have been outside the atoll, not in the shallow water of the lagoon.

The causes of whale stranding often remain unknown, and whereas human impacts such as pollution, injuries from boat collisions or noise from ships have been implicated in some, but Aldabra’s isolation makes this unlikely. It’s more likely that this was a sad, but natural event. Natural beaching in whales is said to occur due to factors such as rough weather, weakness due to old age or illness, difficulty giving birth, feeding too close to shore, or navigational errors. It is possible that after entering the lagoon at high tide, the humpbacks were unable to return to deep water via one of the channels before the tide became too low for them to navigate.

Despite attempts by Seychelles Islands Foundation (SIF) staff to save them, the location and sheer size of the whales meant the team were not able to move or refloat the whales; the adults died, and the current whereabouts of the juvenile are unknown.

Although whale deaths are a tragic event, every cloud has a silver lining. The beaching and deaths of two humpbacks at Aldabra atoll, while a terrible end for the whales themselves, will provide a bonanza for reef organisms for weeks, if not months to come. The first visitors to the carcasses are inevitably the sharks; the day after the deaths, nurse, lemon and tiger sharks converged on the whales, and as the scent drifts out into the sea in the coming days many other denizens of the deep are expected to pay a visit.

SIF staff rarely sees more than one tiger shark at any one time, so it was a special event to see five or six together, with one of them being in excess of four metres long!

Aside from sharks, the humpback carcasses will also be eaten by many species of fish, birds and crabs, providing a nutrient boost to the entire ecosystem.

Forrás: www.nation.sc