Cape Town - Nineteen shark carcasses have washed ashore, torn apart, on Pearly beach near Gansbaai in the Western Cape since last week, with the latest washing ashore on Sunday morning.
The carcasses were sighted by residents and the Marine Dynamics Conservation Trust was called to action.
Necropsies by shark scientists and PhD candidates Alison Towner and Ralph Watson confirmed that two well-known killer whales, Port and Starboard, who were linked to at least five white shark predations in the Gansbaai area, were responsible for these deaths.
The last six years have seen increased sightings of these killer whales around the coast with ongoing speculation that their presence has been driving away the Cape’s great white sharks and other shark species.
Following this recent feeding frenzy, the orca pair was last seen off Mossel Bay.
On Tuesday, February 21, 11 sevengill shark carcasses washed up on the beach. Then by Friday, February 24, eight more shark carcasses had washed ashore the same beach.
On Sunday morning, February 26, another shark carcass was found on the beach, bringing the total number of shark carcasses to 19. Of these, 18 were sevengill sharks and one was a small spotted gully shark.
Towner, who leads research on the decline of white shark sightings in the Gansbaai area as a result of the killer whale predations, said: “It is fascinating to see the way these sharks have been handled by the orcas; every shark had really clear orca tooth impressions known as rake marks on them.
“I have necropsied all the white sharks killed by this pair … Out of the 18 sharks retrieved, all but one sevengill shark was torn open and missing the liver, and most of them had their stomachs missing too.”
Those that did have stomach contents had consumed bony fish and Cape fur seal – which sevengill sharks consume as prey.
Watson, who completed his PhD on smaller endemic shark species in South Africa, said the male spotted gully shark was less than 1 metre long and was missing its head and its liver – it too had visible rake marks on its body, very similar to the sevengills.
“This is the first time we have confirmed the orcas to prey on this species and shows they are more capable of handling smaller sharks than we thought,” Watson said.
Towner said this has been happening since 2015 but this instance was the largest amount of sharks to wash up in Gansbaai and it was the first time sevengill sharks had washed out there due to orcas.
