Do humans really consume 300 million tons of Antarctic krill per year? Why are they not extinct?

Do humans really consume 300 million tons of Antarctic krill per year? Why are they not extinct?

Three hundred million tonnes of Antarctic krill (Euphausia superba) are consumed by humans each year, which is impressive. 

Although Antarctic krill has astonishing longevity, according to incomplete statistics there are around five hundred million tonnes of krill remaining in the world, and the hindrance to global production of Antarctic krill is gradually declining over the next few years.

However, do humans really consume three hundred million tonnes of krill each year? Why are Antarctic krill not extinct? Let us briefly discuss these two problems.

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Antarctic Krill

let’s briefly understand Antarctic krill

Antarctic krill belongs to the genus Euphausia. The name of Antarctic krill is a combination of the geographical location and species classification of this organism.

Antarctic krill is widely distributed in waters near Antarctica and can be seen in groups from a few hundred meters to over 2000 meters in the deep sea.

Antarctic krill have fluorescent substances, they can be found through fluorescence even in the deep sea, especially a large group of glowing krills, which are truly beautiful.

Antarctic krill is a cornerstone species in the Antarctic waters because their large number provides a continuous source of energy for many marine lives, such as penguins, turtles, whales, etc., especially krill is the main food for blue whales as the largest animal in existence.

Adult krills have an average body length of about 6 cm and weigh only about 2 grams each. They feed on marine plankton, such as diatoms that are only 20 microns.

Humans really consume three hundred million tonnes of krill each year?

https://images.app.goo.gl/dkz64WvUtrJwNp5u7
Antarctic annual krill catching statistics

Although krill lives near Antarctica, its vast population has attracted a large number of fishing boats from all over the world. 

According to statistics, the annual catch of krill is about 30,000 tons, which is equivalent to killing tens of thousands of adult Asian elephants. 

In addition to the main krill fishing countries, several countries in the world are the “main force” for krill fishing.

A statistical report from 1973 to 2015 shows that in these 42 years, the world’s catch in 1981 was the highest, as high as 550,000 tons.

In general, the total annual global krill catch averaged around 250,000 tonnes, not the rumored 300 million tonnes.

https://images.app.goo.gl/1Vn5yTN7oY7dTyCz7
School of Antarctic krill

The annual loss of Antarctic krill due to biological reasons

Certainly, these 250,000 tons is indeed an annual human catch, and in the ocean, there are indeed many creatures that feed on krill. 

However, the sum of these animals’ predation of krill is far less than that of humans.

First of all, the blue whale, the marine organism that consumes the most krill, The blue whale can eat about 6 tons of krill a day, so that it can eat 2136 tons of krill a year.

For 10,000 heads, they can eat more than 20 million tons of krill in a year.  But one thing we need to pay attention to is that blue whales mainly feed on Nothern krill species (Meganyctiphanes norvegica), but there are many types of krill species in the ocean.

There are currently 85 known krill species, but blue whales do not live near Antarctica all year round.

Many of the marine organisms we see here feed on krill, not just Antarctic krill.  Relatively speaking, in addition to humans, only Antarctic penguins can only eat Antarctic krill.

Therefore, even if the consumption of Antarctic krill by marine organisms is added, the annual consumption of Antarctic krill will not exceed 100 million tons.

In terms of the relationship between the amount of krill stock and consumption, research shows that the decline of the Antarctic krill stock can take 5 to 8 years.

However, the Antarctic krill fishery has been recorded as the largest fishery in the Southern Ocean.

Why are Antarctic krill not extinct?

Antarctic krill fishing has also been in practice for 47 years, and the number of Antarctic krill is still not extinct. Why is that? There are two reasons.

Strong reproductive ability

At the moment, a species that is consumed in large quantities, if it is not to be extinct, the necessary condition is to have a robust reproductive capacity, which is the case with Antarctic krill.

Antarctic krill is a bisexual oviparous organism. An adult female Antarctic krill can lay an average of 8,000 eggs at a time.

Looking at the entire nature, there are almost no creatures that can give birth to 8,000 offspring at a time, and it is such a tremendous reproductive capacity that the Antarctic krill can still maintain the population under such large consumption.

https://images.app.goo.gl/GBLwjZMuoUchxgVt6
Antarctica’s super food (Image credit: Wkipedia)

Appropriate reproduction timing and unique incubation process

Although the temperature in the waters near Antarctica is low and there is no distinct differentiation of the four seasons, Antarctica is divided into warm and cold seasons.

From November to March of each year is the cold season of Antarctica, and the main breeding period of Antarctic krill is concentrated in the period from January to March each year, which is the period of the Antarctic warm season so that the warmer seawater is conducive to the hatching of krill eggs.

The second is the incubation process. In general, the hatching of eggs is static. For example, fish will lay eggs on aquatic plants, preventing the eggs from being washed away and reducing the hatching rate.

However, the hatching of Antarctic krill eggs is mobile. When spawning, the female Antarctic krill will lay eggs in the shallow sea. After the spawning is completed, the krill eggs will begin to sink.

The entire sinking process will last for about three weeks. They drop from the shallow sea to 2500 meters.

In the deep sea area, the entire incubation process is completed. After the incubation is completed, the small krill begins to float slowly and reaches the shallow sea again from the deep sea.

This unique hatching process keeps most of the krill eggs and larvae in the deep sea for a period of time, so that predators in different established seawater layers can only feed on a small Phosphorus portion of the eggs, thereby significantly improving the survival rate of Antarctic krill eggs.

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References

Nicol, S., Foster, J. and Kawaguchi, S., 2012. The fishery for Antarctic krill–recent developments. Fish and Fisheries13(1), pp.30-40.

Atkinson, A., Siegel, V., Pakhomov, E.A., Rothery, P., Loeb, V., Ross, R.M., Quetin, L.B., Schmidt, K., Fretwell, P., Murphy, E.J. and Tarling, G.A., 2008. Oceanic circumpolar habitats of Antarctic krill. Marine Ecology Progress Series362, pp.1-23.

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Rajitha Dissanayake

Researcher in the field of Marine Mammals and Bio-acoustic

I'm a Master’s student in marine mammals and bio-acoustic laboratory, Institute of Deep-Sea Science and Engineering (IDSSE), Chinese Academy of Sciences (CAS) and focusing on the sustainable environmental application, conservation, and exploring all aspects of the ecology and behavior of marine mammals.

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