20 m
0
Ocean depth in metres
4,600 m

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Chapter 1 Krill matters

This Antarctic animal can be seen from space.

It seems improbable, but these small shrimp-like crustaceans, known as Antarctic krill, can form super-swarms tens of kilometres in size and more than a hundred metres deep.

In fact, scientists estimate there are more than 400 million tonnes of krill in the Southern Ocean around Antarctica – about the weight of every person on Earth.

But if countries want to fish for krill, how do we know how much is safe to catch, without leaving predators hungry and harming the environment?

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Most large predators in the Southern Ocean rely on krill at some point.

Think of iconic Antarctic wildlife like penguins, seals, and the largest animal to have ever existed, blue whales.

Krill are a critical part of their diet.

Over two months (29 January–29 March 2021) Australian Antarctic Program scientists will use a range of novel technologies to measure krill from all angles in waters off the coast of Mawson research station in East Antarctica.

The team on board CSIRO’s research vessel, Investigator, will provide an estimate of how much Antarctic krill is in the region and a better understanding of the environment in which krill live, to ensure the sustainable development of a krill fishery off East Antarctica.

Read on to learn more about krill and the ‘Trends in Euphausiids off Mawson, Predators and Oceanography' (TEMPO) voyage.

Antarctic krill are a ‘keystone’ species of the Southern Ocean because they convert energy from the sun (via microscopic, single-celled floating plants, called phytoplankton) into food for many larger marine species.

In this infographic, 1 krill weighs 1 gram, and each number represents the amount of krill consumed by an individual animal (penguin, seal, whale) compared to the entire krill fishery.

The number of krill consumed by the circumpolar population of penguins, seals and whales, is far greater than that taken by the krill fishery. In fact, the population of Adélie penguins alone, consumes more krill than the fishery is allowed to catch, highlighting the importance of krill to the Southern Ocean ecosystem and the continued sustainable management of the krill fishery.

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Chapter 2 Changing world

While Antarctic krill are tough, resilient animals, their Southern Ocean home is changing. Climate change is warming the ocean, and altering the movement of water currents and winds, and the duration and thickness of sea ice formation.

Carbon dioxide from human activities is also dissolving in the ocean and making it more acidic.

These changes will have huge impacts on krill reproduction and survival.

As well as these changes, commercial fishing for krill is increasing. The catch is turned into fish meal and high value krill oil.

Over the last decade, countries who have fished for Antarctic krill include Norway, Republic of Korea, China, Japan, Chile, Poland, Russian Federation, and Ukraine.

While the krill catch around Antarctica is still only about 0.1% (400,000 tonnes) of the estimated total krill biomass around the continent, the fishery is evolving rapidly around the Antarctic Peninsula, where most of the fishing takes place.

Changes in sea ice dynamics, due to climate change, mean vessels can fish longer and in areas that used to be ice-covered. New vessels and fishing technology also mean that the fishery is becoming more efficient.

The krill fishery is now looking at opportunities to fish in other areas, including off the East Antarctic coast.

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Chapter 3 CCAMLR

Enter CCAMLR (pronounced ‘camel-are’) – or the Commission for the Conservation of Antarctic Marine Living Resources.

CCAMLR is an international body established in 1982 to conserve and manage marine life in the Southern Ocean, particularly krill.

CCAMLR manages krill in three ‘statistical areas’ – 48, 58 and 88 – using precautionary catch limits.

These limits are set by estimating the quantity of krill (their biomass) in each region, through acoustic surveys, and working out the proportion of this biomass that can be safely harvested, leaving enough krill for predators.

Krill fishing is currently established in Area 48 but concentrated in Subareas 48.1 and 48.2 off the Antarctic Peninsula.

The allowed catch for Area 48 is 620,000 tonnes. In the 2019–20 fishing season, 446,783 tonnes were caught.

In Division 58 krill fishing is currently re-establishing in Division 58.4.2. The allowed catch for this region is 452,000 tonnes, but in 2018 only 246 tonnes were caught.

This graphic shows the estimated biomass of krill in CCAMLR Subareas 48.1–48.4 and Division 58.4.2, compared to the allowed catch in each (as of 2018).

In Division 58 – off Australia's Mawson research station – waters were regularly fished between 1975 and 1995, with the annual krill catch reaching 155,000 tonnes in 1981.

After a 25 year hiatus, commercial fishing recommenced in 2016. However the current allowed catch is based on biomass surveys from 1996 and 2006.

Australian Antarctic Program scientists are currently undertaking the most comprehensive study of krill in the region since then.

Chief Scientist for the ‘Trends in Euphausiids off Mawson, Predators, and Oceanography’ (TEMPO) voyage, Dr So Kawaguchi, said the voyage will provide updated information to CCAMLR about krill biomass off Mawson research station.

This will allow CCAMLR to update the Conservation Measure (the agreed ‘laws’, such as who can fish and how much they can take) for the krill fishery in the region.

But while calculating krill biomass in the region is important, it’s not the whole story.

“Understanding the environment in which the krill live, and how it is changing, is key to understanding how krill biomass could be affected in the future,” Dr Kawaguchi said.

“So we want to understand how krill are distributed in relation to predators, ocean currents and fronts, food sources, sea floor habitat, and other krill swarms.”

“We also need to study their growth and behaviour.”

“This information will help us to develop a long-term monitoring program for the region, that encompasses the impacts of a fishery, predators and climate change on krill.”

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Chapter 4 The voyage

Previous krill studies have largely focussed on the top 250 metres of ocean, where most krill are found feeding on single celled plants, called phytoplankton. However, research has shown that krill do visit the very deep ‘abyssal zone’ on the sea floor.

For the first time, the TEMPO voyage will aim to understand the importance of this deep sea habitat to krill, across the seasons, using deep sea moorings, a deep sea camera and light trap, and by examining water samples from near the sea floor for krill’s DNA signature.

The voyage, onboard CSIRO’s research vessel Investigator, will undertake six north-south survey lines or ‘transects’ across an area of more than 793,100 square kilometres. A smaller ‘krill box’ survey, just off the Mawson coast, will intensively survey krill on a fine scale in the vicinity of a large Adélie penguin colony, to tie in with a long-term penguin monitoring program that also reports to CCAMLR.

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Chapter 5 Krill from all angles

During each transect a range of instruments and equipment will be deployed to measure krill, and their environment, from all angles.

These include trawl nets, oceanographic instruments, camera systems and three deep sea moorings called ‘KOMBIs’. The ship’s echosounders will also run constantly, sending out ‘pings’ of sound to find and measure the biomass of krill swarms.

Scroll down to see how the different instruments and equipment will be used to measure and study krill. Click links for more information about each.

Predator observation

More

Acoustics

0–300 metres

Swarm study system

0–60 metres

Trawl net

0–200 metres

KOMBI

Sea floor: 300–1500 metres

Oceanography

10–4600 metres

Environmental DNA

10–4600 metres

Light trap

3 metres above seafloor

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Chapter 6 Life without krill

The TEMPO voyage will help ensure the needs of both the krill fishery and marine predators are met, through its biomass survey and the collection of ecosystem information to design a long-term monitoring program for the region.

But more work is needed at a global level to understand how krill, and the charismatic species that prey on them, are affected by changes in climate, sea ice and ocean chemistry, due to human activities.

Antarctic krill face double jeopardy - their eggs are particularly vulnerable to ocean acidification, and young krill need stable sea ice under which to feed and grow.

Research at the Australian Antarctic Division’s krill aquarium has shown that by 2100, krill habitat in the Southern Ocean is likely to be unsuitable for krill reproduction if carbon dioxide (CO₂) emissions – leading to ocean acidification – continue unabated. By 2300 the entire krill population in the Southern Ocean could collapse.

These risk maps show the hatching success, compared to today, for krill in 2100 (left) and 2300 (right), if CO₂ emissions continue at current rates.

By 2100, if emissions continue on their current trajectory, only 50% of krill embryos will hatch across most of the Southern Ocean (green colour). By 2300 less than 2% will hatch (beige colour).

Use the arrow slider to see the comparison.

These findings are not only disastrous for krill, but a grim warning for the survival of the whales, seals, penguins and flying seabirds that depend on them.

The more we can reduce emissions the more likely we are to ensure the survival of such a critical component of life on Earth.

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