Krill to Kill?

Proposals were made in the 1960's to harvest krill, a shrimp-like crustacean about 2-3 inches (4-6 cm) long which are the sole diet of the baleen whales in the Antarctic. As adults, they gather in huge swarms near the surface of the ocean and can be easily fished. The Soviets and Japanese experimented with krill fishing, and by 1974, Poland, West Germany, South Korea and Taiwan had joined in. New krill fishing technology allowed West German trawlers to harvest 8 to 12 tons of krill per hour in 1976. The maximum catch was 35 tons in 8 minutes. Krill products were developed including krill-butter, krill-cheese, krill protein concentrate, Siberian krill dumplings, meat pies, fish balls, deviled eggs and German krill Bruhwurst. By 1979, krill were being harvested at the rate of 80,000 to 90,000 metric tons annually.

Krill either swim forward by using their five pairs of rear paddle-shaped legs or propel themselves quickly backwards using their tails. They feel using a further six pairs of forward legs, each of which is split into two branches and covered with a net-like array of feathery seta used to gather phytoplankton. Because krill are heavier than the seawater in which they live, they must constantly paddle to stay in one place, as if they were treading water.

Antarctic krill spawn in the summer months, beginning in either their third or fourth summer. Adult females usually release between three and five batches of eggs, two to six thousand eggs per batch, in a spawning season. The eggs sink and hatch at depths of 700 meters (2300 feet). During their first three weeks of life, the larvae rise toward the surface where they begin to feed. Antarctic krill take two to three years to mature, and live for 5 to 7 years.

Krill were thought to be herbivores, but were known to be carnivores and cannibals in winter. Most of the evidence now suggests that adult krill in winter are in a quiescent stage with low energy requirements, and do not need to feed. Larval krill on the other hand must feed or starve. Estimates of krill stock varied widely from 125 metric tons to 6 billion tons. Estimates of krill use by whales, seals and penguins were as varied as the estimates of the standing stock. It was thought that baleen whales (population 338,000) would eat 33 million tons annually, Crabeater seals (population 25 million) would eat 100 million tons annually, and Leopard, Ross, and fur seals would consume 4 million metric tons annually. The seven species of penguins and 19 species of winged birds (petrels, albatross and others) with a total population of 188 million were thought to consume 39 million tons of krill in 1979. Thus, the total estimated consumption was greater than the lowest standing stock estimate, causing alarm that commercial fishery could pose a substantial threat to the Antarctic ecosystem.


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