The thrill of krill and the fight for survival in Antarctica

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The wonders of the Weddell Sea in Antarctica are multiple and awe inspiring. Its depth averages 500m, its clarity is that of distilled water. The temperature is zero degrees on the sea floor but it teems with life. Outweighing all other is krill, its biomass being far greater than any other: Antarctic krill are thought to have the largest population of any species on the planet.

The US passed legislation to conserve Pacific krill in 1976, soon after Japan and Russia began ‘exploratory’ fishing in Antarctica. Since then, krill harvesting has become a huge industry and, while conservation measures have been put in place in some sea areas — krill are a transglobal species — the quantities harvested are increasing and, in some regions, threatening other creatures in the ecosystems. An example is the Adélie penguins, which along with Emperor penguins live farther south than any others.

Most marine species in the Southern Ocean — including whales, seals, penguins, albatrosses, petrels, squid and many others — feed on this small shrimp-like organism. The great pity is, of course, that while the krill shoals are the staff of life for these and numerous other, less iconic species, the humans who harvest them do not use them (or rely on them) for human food but to feed farmed fish, or create nutritional and fish oil supplements, currently a vexed issue for conservationists, and rightly so. Not for essential nutritional needs but for convenience and vanity, the krill-fishing competes with creatures upon which one of the last undamaged ecologies on earth depends.

Damien Enright: 'Krill famously feeds whales, ironically the mammoths of the ocean being sustained by the mice.'
Damien Enright: ‘Krill famously feeds whales, ironically the mammoths of the ocean being sustained by the mice.’

Krill famously feeds whales, ironically the ‘mammoths’ of the ocean being sustained by the ‘mice’. Now that whales in most marine ‘jurisdictions’ are no longer targets for explosive harpoons, they face the hazard of entanglement in nets and death by drowning. That a 60ft-long whale can be entangled gives us some idea of the size and weight of nets.

A recent example was a juvenile humpback spotted in Antarctic waters entangled in fishing gear. Its dorsal fin was missing, and it was trailing nets, ropes and buoys that had wrapped around the tail cutting deep into the skin. It was probably a youngster on its first solo migration and had likely carried the gear thousands of kilometres down the South American coast. It was labouring to swim and was likely to drown as it lost the power to enable it to forage, and starved. Conservationists are demanding better protections as changing sea temperatures bring migrating whales nearer to intensely-fished areas.

A recently observed high-seas incident revealed orca behaviour rarely, if ever before, seen. A humpback in bad condition was spotted so entangled in heavy nets that it couldn’t surface to breathe. Then, a pod of orcas, killer whales, happened along. Instead of attacking and killing the whale, they moseyed about until the Mother Orca arrived and investigated the entangling ropes. Her family followed. Observers noted that they appeared to drag the hawsers from the humpback’s body so that, freed of the weight, it could more easily reach the surface to breathe. The rescuers then left.

Orcas are wary of attacking adult baleen whales for fear of a lethal blow from their tails. However, part of an orca pod will distract the mother of an infant calf so that companions can drown it. Also, a teenage humpback separated from its mother is in danger of orcas grabbing its flukes to roll it onto its back and keep it there long enough to drown. Killers are killers. It may have been sheer chance — rather than cetacean solidarity – that the orcas freed the ailing whale.

To end, I consider again the wonders of the Antarctic ocean as unbeknown to and unimagined by our intrepid Kildare-born explorer Ernest Shackleton. Last year, a colony of approximately 60 million Jonah’s icefish nests were found on the floor of the crystal clear waters of the Wendell Sea he and his brave companions crossed in 1908. The colony covers some 240sq km with 60m nests, each containing 1,500 to 2,000 eggs guarded by the parent fish. The total biomass comprises 60,000 tonnes (132,000,000 lb) of fish, average length 50cm. The largest icefish colony previously observed numbered fewer than 100 nests.

Now that we’ve found this wealth, should we not seek licences to extract it? After all, apart from feeding Adélie penguins, also useless to humans, what good are icefish? They’re unpalatable for our species and presently of no commercial interest but surely some use can be found for them? Fishmeal fertiliser? Also, they do eat krill and, hey!, sooner or later may compete with krill harvesting. Meanwhile, they’ve converted a wasteland into a living ecosystem. Unfortunately, uncontrolled fishing would soon turn it into a wasteland again.



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