City of Cape Town officials pulled a large whale carcass from the harbour on Thursday.
"This was a humpback whale that was originally about 10m long," Jacques du Toit of the environmental management branch in the City of Cape Town told News24.
The large carcass was removed at the Oceana power boat club slipway.
"The propellers of a ship literally chopped off the back part of the whale just behind the dorsal fin. The parts we pulled out were about 7m long," said Du Toit.
This is not the first carcass found this week.
"On Tuesday, we pulled out a Bryde's whale off Miller's Point by Simon's Town. That one was killed by entanglement in an octopus trap line," Du Toit said.
Number of carcasses
The environmental management branch recovers between 14 and 15 whale carcasses per year, and not all of them are due to ship strikes.
Some are killed when they get tangled in nets, or because of strandings.
Du Toit said the ship reported the incident to the port authority.
"I believe it [the incident] was reported to port control and to the NSRI. It's an accident that ships can't avoid. Ships are simply too big to manoeuvre out of the way."
According to a research document titled "Vessel Strike of Whales in Australia: The Challenges of Analysis of Historical Incident Data", whales face a significant risk from ship strikes.
"Death or injury to whales from vessel strike is one of the primary threats to whale populations worldwide. However, quantifying the rate of occurrence of these collisions is difficult because many incidents are not detected (particularly from large vessels) and therefore go unreported," says the research paper.
It found that fin whales were most likely to be involved in ship strikes, followed by humpbacks, right, grey and minke whales.
The International Whaling Commission (IWC) has said there is no solution to prevent whales and ships from colliding.
"For now, the most effective way to reduce collision risk is to keep whales and ships apart, and where this is not possible, for vessels to slow down and keep a look out. All mitigation work needs to be undertaken in a collaborative way as migratory animals like whales travel across national boundaries," said the IWC.
Du Toit said that the number of whales made accidents inevitable.
"There are literally thousands of whales out there and the more there are, the more are likely to die. Generally the whales move out of the way, but sometimes the boats come quite fast.
"It seems the whale tried to dive down, but it was at the surface," said Du Toit, explaining why the rear of the whale was hit.
Last week, a whale washed up on the breakwater at Paarden Eiland.
Du Toit said that, while the number of dead whales around Cape Town was consistent, he was surprised at the number of whales which were caught in octopus fishing lines.
The carcass was delivered to a landfill.