Most of the human population does not know and has probably never heard of the Antarctic krill species (Euphasia superba). However, this small marine species is designated by many scientists as the most important in the food web of the Southern Ocean, which surrounds the entire Antarctic continent. Antarctic Krill is a small crustacean, like a “mini-shrimp” (figure 1), however its biomass is estimated to be between 300 and 500 million tons, which makes it the largest biomass of any multicellular species in the world. The Atlantic sector part of the Southern Ocean contains 70% of the population.
Thus, both due to their enormous quantity and the high energy values they contain (e.g.: omega 3), krill are the main prey for countless Antarctic species, from penguins, seals, whales, fish and many other species of albatrosses and petrels. In some of these species, krill can even represent more than 70% of the diet. Its ecological importance is therefore undeniable in this large ecosystem.
Finally, and as mentioned above, krill is an animal with characteristics that are also very beneficial for humans through medicines, as well as for other activities through fishmeal/aquaculture or natural fertilizers. In this way, there is a very active fishery that targets krill, making its management laborious and highly special.
Krill fishing has existed for over 50 years, mainly around the Antarctic Peninsula and the South Shetland Islands, South Orkney Islands and South Georgia. Initially more focused during the summer, it moved progressively to mainly operating in the winter. A measure aimed at avoiding competition between fishing and predators during the breeding season.
Its management is carried out by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which is based on biomass surveys. This is a representative sample of the potential biomass in a given area, then stipulating a maximum quota of krill. As a prevention and sustainability focus, CCAMLR states that 75% of the original biomass is maintained.
So, what is the difficulty in this management?
Much of the discussion about krill fishery management in CCAMLR has focused on protecting krill predators that breed on land and fishing operations.
On the other hand, in recent times, there has been relatively little discussion about the risks that fishing poses to the krill population itself. The view of sustainability to date is now challenged by the high levels of variability observed in available indices of krill abundance, particularly over the last two decades, which vary in magnitude and increasing fishing space, resulting in substantial local impacts.
Although the reproduction cycle is considerably known and studied, krill are quite dependent on both ocean currents, plus the locations and environmental conditions where juveniles develop. Hence, being where the problem lies today. With current climate change or the increasingly strong decline of sea ice, crucial in its development, krill recruitment has varied strongly between years, and this is expected to be subsequently reflected in the available biomass. Much of the previous research was carried out mainly in the summer, leaving a gap in its cycle in the winter phase. Fishing itself has evolved and today its capacity to extract krill from the water both spatially and in quantity is much faster, having much more sudden impacts on the population. In addition, this decreases in sea ice, opens new areas available to the fishing industry, which generate more pressure. The key thus lies in understanding the krill reproduction and development cycle with present environmental conditions and future perspectives. Both science and the fishing industry must work hand in hand, so that we have the most real value of the total krill biomass, and thus adjust and apply the best measures. In the end, is of upmost aim that the benefits for humans never corrupt the ecological and biological importance that this fantastic species has for the Southern Ocean and the entire Antarctic region.
Author: José Abreu
Source: Meyer, B., Atkinson, A., Bernard, K.S. et al. Successful ecosystem-based management of Antarctic krill should address uncertainties in krill recruitment, behaviour and ecological adaptation. Commun Earth Environ 1, 28 (2020). DOI: 10.1038/s43247-020-00026-1
