Tasmanian scientists study a krill's 'sound signature' to help estimate populations
Updated
Scientists in Hobart are experimenting to capture the sound of Antarctic krill in a bid to better determine how many are swimming in the Southern Ocean.
Key points:
- Krill is the term used to describe about 85 species of open-ocean crustaceans known as euphausiids
- Antarctic krill live in the southern ocean
- Adult Antarctic krill grow to about six centimetres and weigh over a gram
- They are one of the most successful and abundant animal species on earth
- There are an estimated 500 million tonnes of Antarctic krill in the southern ocean
- Commercial krill fishing began in the early 1970s
- The fishery is now managed through an international body (CCAMLR)
Antarctic krill are one of the most abundant animal species on Earth, and most of the larger Antarctic animals depend directly or indirectly on the crustacean.
The sound that scientists are recording does not actually come from the krill itself.
They are using echo sounding technology to record the sound reflected from different-sized krill, and to help them identify the 'sound signature' of individual krill.
Australian Antarctic Division (AAD) acoustician Martin Cox said scientists wanted to use the acoustic signature of an individual to help estimate the size of a biomass.
"What we're trying to do is figure out how much sound an individual animal, individual krill, actually reflects," Dr Cox said.
"Now, the reason we're doing that is we can then use that to tell us how many krill, how much biomass is in the southern ocean."
More than 8,000 Antarctic krill have been placed in a large 10,000 litre tank at the AAD headquarters at Kingston near Hobart.
The tank is equipped with echo sounders, which transmit pulses of acoustic energy into the water.
"When they hit an object, such as krill, the energy is reflected back, amplified and illustrated on a digital display," Dr Cox said.
The krill inside the tank are filmed at the same time.
"We can compare what we see with the camera, and what we see on the echo sounder," Dr Cox said.
"Then we can take those signals and then we can figure out how much sound an individual krill is reflecting."
'Krill are happy in test tank'
Echo sounders are used by fishing boats and scientific vessels as they move around the Antarctic continent.
Australia's new icebreaker will also be equipped with the latest echo sounding technology.
"So what we can do is take the signal from here, compare it to the signal we see from the ship as it's doing a survey, and calculate how much krill biomass is there," Dr Cox said.
Commercial krill fishing in Antarctic waters began in the early 1970s.
The fishery is regulated through an international body, the Commission for the Conservation for Antarctic Marine Living Resources (CCAMLR), which sets limits on the krill catch.
Australia's scientific representative to CCAMLR Dirk Welsford said the research was going well.
"Working with animals is always difficult and we weren't sure the krill were going to be happy in the big tank," he said.
"Because we've got such experienced people working with krill when we transferred them into the tank last week, they have been happy, and they're doing their natural behaviour, which means the data we're getting is going to be really good quality," Dr Welsford said.
This data will be analysed and used in conjunction with data being collected from vessels in Antarctic waters.
"At the moment the information we use is based on a precautionary approach," Dr Welsford said.
"So, there's certainly the potential for this work, to change significantly our estimates of krill biomass."
Topics: fishing-aquaculture, rural, research, research-organisations, tas
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