Southern seas red with krill
Southern waters are turning red with large swarms of krill.
A photographer saw red when he stumbled upon krill washed up on an Otago beach, and tourists are being treated to sights of red seas at Milford Sound and on the Fiordland coastline.
Waverley resident Paul Van Kampen was bike riding when he came across Munida gregaria - swarms of crustacean often called red lobster krill - near Wellers Rock, Te Rauone Beach on Monday.
The keen photographer captured the vivid sight on camera.
"I used a polariser filter to cut the glare off the water and got to the right sun angle to achieve this.
"I noticed they are surprisingly strong swimmers, so [I'm] not sure why some sat in the shallows and died as the tide went out."
Van Kampen recalled seeing the same thing when he was kayaking in summer when he was younger, as the krill became attracted to his red kayak.
"You could actually feel them bumping up against the kayak."
About half of the recent swarm appeared to wash up on the beach and die, while the rest washed back out to sea, he said.
Heli Tours Queenstown pilot Paul Mitchell said for the last few days Milford Sound and Fiordland coastal waters had been washed with red.
"It's the time of year for it apparently. From the air it's pretty amazing. It's quite red."
Tourists on board from Canberra, Australia, photographed the sight.
"The passengers have been pretty excited, but also amazed to see something of that scale. It's pretty unique, and it covers most of the Milford Sound and out the coast."
University of Otago marine science professor Steven Dawson said the krill were no doubt munida gregaria, sometimes called red lobster krill.
"It's quite a cool thing. It is extremely common, particularly this time of year.
"They form large swarms of hundreds of thousands, or even millions of individuals. It can be so dense as to turn quite large areas bright red."
Krill were important to how the Otago and Canterbury coastal systems worked, he said.
"There is more to these little creatures than meets the eye."
As well as food for whales, they were food to red cod, and a sign like that at Te Rauone Beach could mean a good season for red cod, Dawson said.
Krill usually swarmed on the surface early in their life cycle, then settled on the sea floor.
A similar influx of krill happened in Picton in 2013, when fishermen claimed they had not seen so much at one time for at least 30 years.