The carcass of a critically endangered Antarctic blue whale that washed up in Walvis Bay this week is the first-ever recorded stranding of this species in Namibia, South Africa and probably on the continent since the end of commercial whaling in 1985, according to conservationists.
Blue whales are the largest animals ever known to inhabit the Earth.
The young cetacean was almost certainly killed in a collision with a large ship near the bay, according to Dr Simon Elwen, the director of the Namibian Dolphin Project (NDP).
“It looks like the ship hit the flank, then the animal was rolled and the fin was broken too. It likely died very quickly,” he said, adding, “We have no idea of what hit that whale. It was a fresh animal, it wasn’t bloated. In the port, there’s a lot of boat traffic in and out of there.”
The NDP said ship strikes are increasingly common in global waters and around South Africa, because both whale and ship numbers are on the rise, with this event the first clear evidence in Namibia of a ship striking a large whale.
“There’s certainly anecdotal evidence,” Elwen told the Mail & Guardian on Thursday. “It’s in very low numbers — one or two a year. The evidence is that it’s not significantly affecting our local populations of any kind of whales, but certainly it is a growing concern, especially around the Western Cape where we have lots of whales year-round.
“Ship strikes are increasing around Southern Africa but it’s sort of in line with increases in whale populations,” Elwen said. “Whale numbers are getting more; ships are getting more.”
Last year, a review published by the Endangered Wildlife Trust and Nelson Mandela University described how there is increasing concern about the consequences of maritime vessels colliding with marine animals.
The review found at least 75 marine species affected by collisions with vessels, including smaller whales, dolphins, porpoises, dugongs, manatees, whale sharks, sharks, seals, sea otters, sea turtles, penguins and fish.
The Antarctic blue whale carcass, which measured 18m in length — they can reach up to 30m — was first seen floating in the bay on 26 April by local tour operator Laramon Tours, which reported the find to the NDP. The next day, the carcass washed ashore and samples were taken.
The NDP said it was liaising with Namibian officials to try to recover the skeleton.
The Antarctic subspecies of blue whales remains listed as critically endangered, with its current estimated population still being less than 1% of its original pre-whaling size. Surveys co-ordinated by the International Whaling Commission have estimated the population to be increasing at about 7% per year.
It’s not clear why the whale was so close to shore. Blue whales, according to the NDP, are usually found offshore (well off the continental shelf), and their seasonal migrations and breeding and feeding grounds are generally poorly understood.
There have been only a handful of sightings — fewer than 10 — of live blue whales around Southern Africa to date, mostly off western South Africa and Namibia, despite extensive observer effort.
“There’s been less than five sightings of blue whales alive that we have records of in Namibia post-2000. The good news is that whale stocks have recovered well. But numbers of blue whales are still very low compared to historical records,” Elwen said.
Acoustic monitoring in deep waters off the southwestern Cape and northern Namibia has revealed regular detection of blue-whale calls over winter months “revealing that the animals are still using these areas where they were historically caught, supporting overall population recovery”, the NDP said.
But the downside of those increasing numbers is that this means there will be more impacts with human-made causes, such as entanglement and fishing-ship strikes “not to mention the impacts of overfishing and habitat change”, Elwen said.