Br.Ant.Territory : Antarctic Krill: Are They Really in Decline?
Submitted by (Juanita Brock) 16.11.2004 (Article Archived on 30.11.2004)
Besides there being ethical problems with the targeting of animals so low on the food chain, there seems to be confusion about the biomass of Krill.
ANTARCTIC KRILL: ARE THEY REALLY IN DECLINE?
By J. Brock (FINN)
Some commercial fisheries, such as the Krill Fishery, target animals that are near the bottom of the food chain. Besides there being ethical problems with the targeting of animals so low on the food chain, there seems to be confusion about the biomass of Krill. Some experts say its biomass is so huge that it cannot be counted, and others putting a declining figure on the stocks by 80% in the last 30 years.
Antarctic Krill is a tiny shrimp-like creature, which is a vital source of food to other fish and animals in the region of the Southern Ocean. At the moment, stocks are in the process of being counted. Just about every creature in the Antarctic either eats Krill or eats something else which eats it. And, the British Antarctic Survey wants to know how many of these important creatures there are, even the ones living under the ice. From the Research Ship, the James Clark Ross, Dr. Andrew Brearly (AB) of BAS told Claire Bolderson of BBC World Service (CB) on 22 December 2000, how they went about discovering this.
AB: We use echo-sounders onboard the ship and we drive up and down pre-determined transit lines and as the ship steams along we send puffers of sound down into the water and measure the strength of the echoes that are returned. And, a lot of these echoes are returned from the Krill and we just add up all the echoes from Krill and that enables us to work out how much krill there is in the water around South Georgia.
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CB: But what do you mean by echo? Are the Krill talking to you?
AB: No. the Krill aren't talking themselves but if you sort of imagine a situation where you are standing in front of a brick wall and you clap your hands, you will hear an echo of the clap from the brick wall. And we sort of use a similar system in BAS. We fire puffers of sound into the water and the sound is reflected back off the Krill. The Krill aren't singing or shouting or anything but they act, if you like, like the brick wall off which your clap would bounce.
CB: Now, you say these Krill are extremely important to everything that lives in that area. Are you doing this because you think that their numbers are diminishing?
AB: Not necessarily directly because of that. We are doing it as part of a long-term monitoring exercise to see how the population size of Krill varies naturally. But part of our research may lead us to show that Krill populations were diminishing if, in fact, they were. Our evidence to date actually just shows a cyclical change of abundance. One year you may have quite a large population size of krill and, in the following year, the population size might be low. and, in years when the population size is low, predators such as seals and penguins, which depend upon Krill have quite a hard time. They cannot find enough food to eat. They also have difficulty rearing their young but it appears that this cycle of high and low Krill abundance is quite natural.
In March, 2003 and again in March, 2004, SARTMA interviewed Fisheries and Scientific Officials on South Georgia. Chief Fisheries and Maritime Officer, Patrick Lurcock (PL) was adamant both in 2003 and in 2004, that numbers of Antarctic Krill were unknown but thought to be uncountable. He told SARTMA:
PL: Because the Krill stocks are so super abundant, CCAMLR have set a low precautionary figure and of that low precautionary figure, only 4% were caught last year. So, that means we are pretty confident that there is no significant pressure on the krill fishery so there is not a real urgency to do the fine-scale in-depth monitoring of catch and effort and the biology. We know quite a bit about the biology. Whereas the more commercial species such as the Toothfish, we have to concentrate more on them because there are as many people as possible who want to fish for that. So, it’s more urgent and there isn’t that safety level with Toothfish as there is with Krill. But at the moment the amount of Krill that they are taking is insignificant compared to the amount of Krill that’s out there. And, the other advantage that we have with Krill compared with something like Toothfish, Krill don’t live very long, just like the squid in the Falklands. Katherine can correct me if I am wrong here. She is a Biologist and understands these things. And, if you have a blip – a bad year – it doesn’t take long to breed back up once conditions get good again, whereas South Georgia’s finfish grow very, very slowly. If you get it wrong and hammer them too hard, it takes a long, long time to recover.
As for the Krill, it’s being watched. CCAMLR and the Government here have their eye on it, making sure that it’s not endangered and we are confident that the Krill stocks are safe.
SARTMA: Surely, there has been some forethought in this but given that Krill are a major food source for the wildlife that is indigenous to South Georgia, is there any priority to find out what catches for human consumption can be taken?
PL: Yes. There is research being done British Antarctic Survey people on Bird Island and in Cambridge are doing research cruises that are working on predator-prey relationships. They want to know what stocks are in all the species – how many Penguins there are, how many seabirds there are, how many seals there are. And, they want to know what they eat and how much. And then, the whole point is to run a management facility from this approach and running it depends on everything, especially something like Krill, which is so central to it all. I don’t know the numbers but I know there are people working on it and fine-tuning our estimates of just how much stock of Krill there is.
They do it using the James Clark Ross, sailing up and down and doing acoustic surveys of Krill and other species and, with the hands-on studies of the creatures of the beaches. They put satellite tags on seals and penguins and seabirds and see where they go and then they look at the stomach contents and see what they eat. Then, for example, they see how much energy a penguin needs over a year. We’ve got some work with HMS Endurance. They have been taking aerial photographs while using their helicopters, of the various penguin colonies, to get a better idea of how many penguins are breeding. The whole idea is that when we fish for Krill that we do leave enough for the birds and other wildlife here to eat. Presumably, that includes whales and other fish, even though we can’t see them. And, the biologists aboard the commercial fishing ships and the biologists here are looking to see what the whales and fish eat as well. So, we are constantly building up a better picture of the interaction between birds, penguins, fish and seals.
On 01 November this year, British Antarctic Survey released a press statement that, on the surface, refuted what the South Georgia officials and their own scientists had previously said. On the 9th of November 2004, Dr. Angus Atkinson told BBC World Service presenter, Graham Bound that: “The most likely explanation is a decline in sea ice in the main area of the Southern Ocean where Krill are concentrated.
Data shows that at least half of the Southern Ocean Krill stocks are in the South-West Atlantic sector, broadly between the Antarctic Peninsula and South Georgia.
In that area, over the last 30 years or so, there has been a decrease in winter sea ice extent and the sea ice is important for the Krill because it acts as a nursery area for the young Krill to survive the winter. The food source is the ice algae on the underside of the ice. The decrease in the extent and duration of the sea ice seems, at the moment the most likely explanation for this decline.”
SARTMA wonders if the echo-sounding project and assessment of Krill stocks is complete and if the results of the study compare with what Dr. Atkinson and the British Antarctic Survey are now saying about Krill stocks in the South-West Atlantic. Somehow, the later report doesn’t set well with me as I have a natural tendency to believe the people who are working on location.
There are ethical problems with having a commercial fishery that competes with other animals that are dependant on the same resource. Those ethical problems become critical when, if the later report is true, that resource has been in decline. However, the South Georgia Fishery is one of the best managed in the world and I cannot envisage that excellently managed fishery putting any stock at risk, especially if it will lead to the decline of other fish stocks in the fishery and on the high seas.
Perhaps the second report was a little premature. While it is true about the decline of sea ice, the Krill are resourceful and perhaps it is possible that they have found another suitable food source in the nutrient-rich waters of the Southern Ocean. Lets hope so.
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