A lack of krill is thought to be the main reason for the decline in fur seals observed in the north of South Georgia. Researchers are concerned that this symptom could spread to the archipelago and the Southern Ocean.
On October 15, the journal Global Change Biology published an article on fur seals in South Georgia. The Franco-British research team discovered that this population has declined by 7% since 2009 on Bird Island.
Fur seals were hunted for their pelts between the eighteenth and early twentieth centuries, bringing them close to extinction. They then recovered, benefiting from protection measures and an abundance of krill. The South Georgia fur seal population was estimated at between 4.5 million and 6.2 million in 2000.
But the calculation methods used were not as accurate as they are today. To improve their count, British researchers flew over the colonies between 2007 and 2009. Today, the sea lion population is estimated at 3.5 million in South Georgia.
Fur seals are difficult to track. Not all the animals return to the beaches when they breed. Eighty percent of males and around 32% of females remain at sea.
The population on Bird Island in the archipelago is showing signs of weakness. It has lost 7% of its density since 2009. Researchers believe this is due to a problem with the supply of krill.
The decline in fur seal populations is correlated with the increase in ocean temperature, and therefore very probably with the loss of krill, which is moving further south and towards the bottom.
“Changes in the abundance of krill in the Southern Ocean in the 21st century are once again threatening these iconic animals. Krill can account for up to 80% of the diet of South Georgia fur seals, so they are suffering a catastrophic decline,” explains Jaume Forcada, population biologist at the British Antarctic Survey.
“If the pressure on the Bird Island fur seals also applies to the entire South Georgia population, there could be a continuing decline in this region,” he explains. Similar declines have been observed on the South Shetland Islands and Bouvet Island.
Fishing is not directly correlated with the results of the study. However, the authors recommend that fishing quotas be reduced. Today, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is meeting for 10 days of discussions, during which fishing limits will be discussed as they are every year.
Camille Lin, PolarJournal
First image, Michael Wenger
Link to the study : Forcada, J., Hoffman, J.I., Gimenez, O., Staniland, I.J., Bucktrout, P., Wood, A.G., n.d. Ninety years of change, from commercial extinction to recovery, range expansion and decline for Antarctic fur seals at South Georgia. Global Change Biology n/a. https://doi.org/10.1111/gcb.16947.
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