A view to a krill: the deep south’s fragile wildlife

Rosy Whelan

This time last year, as our ship steamed north from the Antarctic Peninsula – one of our beleaguered planet’s few remaining wilderness areas – four fishing ships hove into view. With calm waters and clear skies, the ships stood out like monstrous invaders from an alien world. Perhaps they answered a question that had been forming in our minds – where have all the animals gone?

While visitors to Antarctica have many different reasons for wanting to partake in this extreme form of tourism, the overarching impression is of wildlife – of animals that are so engrossed in the activities of daily life that they have little fear of, or interest in, the humans who come and go.

Having visited many different penguin colonies and cruised blissfully in inflatable boats through picturesque, ice-bedecked waterways, it became alarmingly evident how few penguin nest sites were occupied, and how few and far between were sightings of seals – crabeater, Weddell, elephant, fur and leopard. Never before had we needed to ‘queue’ to see a lone seal basking on an ice floe.

Our ship’s Automatic Identification System (AIS) supplied the names and call signs of the fishing ships, their GPS locations and their proximity to Smith and Snow islands in the South Shetland group. A quick check of the website of The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), whose global headquarters is located in Hobart, confirmed that the four ships were licensed krill-fishing vessels, two Norwegian and two Chinese. Nevertheless, we were left wondering when and where these ships are permitted to fish, and for how long. There was no doubt that their position was well within the crucial foraging range – an area constrained for nesting penguins – at peak time during the breeding season.

Krill the key

At first sight, the Antarctic food chain seems short and simple. Its keystone is krill, Euphasia superba, a tiny shrimp-like crustacean with intricate compound eyes, two antennae, seven pairs of thoracic legs used for feeding and grooming, and five pairs of swimming legs. These krill reach sexual maturity at the age of two and live for about five to seven years. While most krill are one to two centimetres in length, others can grow to between six and 15cm. Externally visible gills help to distinguish krill from shrimp.

Krill reproduce in summer, their eggs sinking through the water column to some 1,000m before hatching and evolving through five larval stages to reach maturity the following spring. The complicated lifecycle of these tiny creatures has developed over millennia to cope with the rigours and challenges of the Southern Ocean environment, including dramatic fluctuations in the availability of sea ice, daylight and food.

Appealing

On reaching the adult phase, krill swarm in schools of thousands, which might offer protection to the individual, but sadly makes them particularly appealing to the fishing industry.

The ever-growing global market for krill has made it increasingly commercially viable for ships to travel from anywhere to the bottom of the world. Krill is used as food by the aquaculture and livestock industries, as fish bait, pet food, for human consumption and by the ‘health’ industry. But at what cost? For more than four decades, based on tonnage, the Antarctic krill fishery has outstripped all others in the Southern Ocean.

Biomass

The estimated biomass of krill varies dramatically – from 60 million to 25 billion tonnes – depending on the method of calculation employed. In spite of a significant amount of research having been undertaken to identify how much krill is consumed by warm-blooded animals – such as whales, seals, penguins and birds – the reality is that the amount consumed by fish and squid is even more challenging to estimate with any degree of accuracy.

Furthermore, there is much speculation about krill numbers prior to the commencement of last century’s whaling industry, complicated by decades of scientists labouring with falsified whale capture figures.

Interestingly, CCAMLR was established as a ‘multilateral response to concerns that unregulated increases in krill catches in the Southern Ocean could be detrimental for Antarctic marine ecosystems particularly for seabirds, seals, whales and fish that depend on krill for food’.

Real risk

It is optimistically believed that the annual krill harvest is well below the catch limit, but there is a risk that localised excessive fishing will impact on the animals that depend on krill for food, particularly during the short summer breeding season. There is much overlap between the fishery and the breeding grounds of seals and penguins in particular.

During the next few Antarctic seasons, it will soon become evident whether or not last season’s paucity of wildlife was a one-off occurrence. Distant as it may seem to be, the destruction of Antarctica’s intricate food chain has far-reaching implications for us all. The good new is, as independent consumers, we can decide whether or not to buy krill-based products.

Rosy Whelan is a freelance writer and a veteran Antarctic expeditioner.