The ‘Krill Action Group’ said successful ecosystem-based management of Antarctic krill should address uncertainties in their recruitment, behaviour and ecological adaptation.

The group was established in 2018 by the Scientific Committee of Antarctic Research (SCAR), with support from the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

Lead author of the group’s first paper, Dr Bettina Meyer of the Alfred Wegener Institute in Germany, said that understanding of krill distribution and dynamics has dramatically increased in the last few decades.

“But there are still major gaps in our current knowledge, including controversy on population trends, overwintering, migration and other key aspects of krill biology,” she said.

Dr So Kawaguchi, a krill biologist at the Australian Antarctic Division and vice-chair of the action group, said that a better understanding of hotspots for krill spawning and larvae production is needed to ensure sustainable fishing.

“Because krill abundance is highly variable, and the krill fishery is more concentrated than ever before, the risk of direct fishery impacts on the krill stock itself may be higher than previously thought,” he said.

• Antarctic krill (Euphausia superba) is a key species in the Southern Ocean ecosystem, being the major prey for marine land-based predators such as penguins, as well as a major grazer of primary production.
• Seventy percent of the known krill population lives in the Southwest Atlantic sector of the Southern Ocean, near the Antarctic Peninsula. The SW Atlantic sector is also warming rapidly and one of the regions most affected by climate change.
• This area is the focus for the krill fishery managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), with the main goal of safeguarding the large populations of krill-dependent predators.
• While still well below sustainable levels, the krill catch is increasing, is concentrated in a small area, and has shifted seasonally from summer to autumn/winter.

Dr Meyer said that technological innovation and the potential to involve the fishing industry in research provide new opportunities for knowledge.

“A combined effort by the krill research community and fishery would enable a holistic approach to data and information collection and integration,” she said.

Some of the key research priorities identified by the SCAR Krill Action Group (SKAG) are:

• What controls the numbers and source of juvenile krill?
  Surveyed numbers of juvenile krill are far below those required to explain the patterns in abundance of adults. Further research on environmental conditions and krill behaviours that favour recruitment of juveniles to the adult population are needed. This would include plankton surveys from fishing vessels, echo sounders on seals, and remote sensing of sea ice from satellites.
• Resolve the debate over whether krill populations have declined
  Understanding whether krill populations have been impacted by the known ecosystem changes over the last century is necessary to inform future projections. Krill fishery management does not explicitly factor in the effects of long-term warming of the Southwest Atlantic sector of the Southern Ocean (habitat of 70 percent of the known krill population), and projected adverse consequences for krill.
• Pinpoint the hotspots of successful spawning which merit protection
  Data focused on resolving where and when spawning hotspots occur can be used to assess the fishery risk to the krill stock. Studies show that successful spawning occurs primarily near shelf/slope areas during summer. Given that the fishery is now concentrated on the shelf during autumn and winter, it may mean that fishing pressure on the spawning portion of the population is higher than previously thought.
• Identify seasonal overlaps between the fishery and successful spawning stock
  Catch limits may not be as precautionary as intended. Adult krill distribution shifts from mainly off-shelf in summer to on-shelf in winter, where the present-day fishery effort is focused. Understanding the mechanism of this behaviour and what portions of the population are involved, are critical to understanding the impact of the on-shelf fishing on this winter krill population.
• Future-proof fishery management for climate change
  A better understanding of how krill populations respond to changing temperature, food availability and environmental conditions, needs to be built into decisions about fishery management.

The SCAR Krill Action Group (SKAG) involves scientists from the US, Europe, Australia, China, and Argentina. Their research priorities were published in Communications Earth & Environment on 16 October 2020.