US authorities are investigating after two dead endangered whales were removed from the bottom of an Australian Navy ship.
The whales, possibly a mother and her calf, were discovered on Saturday (local time) and later dislodged from the hull of HMAS Sydney while berthing alongside Naval Base San Diego in California.
One of the deceased whales was close to 20 metres long while the smaller one was just seven-and-a-half metres.
Tissue and blubber samples have been taken from both whale to determine if they are related, and the larger whale has now been towed out to sea.
National Oceanic and Atmospheric Administration (NOAA) confirmed with Yahoo News Australia the pair were fin whales, which are listed as endangered in the US, with only 8000 living off the West Coast of North America.
They said they are cooperating with the Royal Australian Navy and the US Navy to examine what led to their deaths.
In a statement the Royal Australian Navy said they took "marine mammal safety seriously", adding they were "disheartened" by the deaths.
Ships, speed and whales – a 'lethal combination'
A senior director at International Fund For Animal Welfare (IFAW), Patrick Ramage, told Yahoo News Australia the "tragic" deaths occurred even though there is increased use of underwater acoustic monitoring and other technologies to try and minimise strikes.
He said despite being the second largest species to have lived on the planet, fin whales are tiny when compared to large military ships which tower over them like "floating skyscrapers".
"It's not the first time that an Australian Navy vessel has struck a whale, and certainly it's something that other navies including the US Navy have had to contend with, as they move sometimes at high speed through critical habitat areas," he said.
"Speed kills almost irrespective of size of vessel, but when large vessels are moving through critical habitat areas, such as off southern California right now, where a lot of fin whales and other species are feeding, it can be a lethal combination."
While only eight whales were reported to have been killed by ship strikes down the US West Coast between 2012 and 2016, NOAA believe many go unreported.
Their modelling estimates that on average 43 fin whales are killed annually in the region, but this data only looked at the period between July and December and deaths could be as high as 93.
If the upper estimate is correct, this would account for one per cent of the population.
Research suggests shipping and its associated noise is increasing, and this is affecting whale communication, particularly baleen whales who speak using low-frequency sound.
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