Life in Antarctica Relies on Shrinking Supply of Krill

On the Antarctic island of South Georgia, in February, toward the middle of what passes for summer at the bottom of the world, I hurried through the ruined whaling station of Grytviken.

I had an appointment at the British Antarctic Survey station on the opposite side of King Edward Cove. I was to interview a marine ecologist working on krill. I did not want to be late.

The keystone of the South Georgia ecosystem, the secret to the miraculous abundance of wildlife on this stark, cold, windswept island—the foundation, indeed, for almost all vertebrate life in the Antarctic—is krill.

South Georgia and the South Sandwich Islands are administered from the Falkland Islands as a British Overseas Territory, in which the little outpost of Grytviken is the only inhabited spot. The inhabitation is very marginal. In southern winter there are just eight staff members of the British Antarctic Survey, including a doctor, a government officer, and a postal clerk. A handful of visiting scientists augment this skeleton crew in southern summer.

Grytviken is gritty and grim. The name means "Pot Bay," a reference to the cauldrons in which the Norwegian whalers here rendered oil from blubber. It is apt. The rusting vats, boilers, ramps, chimneys, and ramshackle buildings of the long-abandoned whaling station; the wrecks of the catcher boats stranded on the waterfront; and the rows of giant whale-oil tanks upslope are all the apparatus of a genocide, in the literal, Latin sense of the word. The genus was Balaenoptera, the baleen whale.

From the whale's upper jaw, in place of teeth, hang long, fringed curtains of keratin—baleen—used to seine krill. The largest member of the genus and the biggest creature ever to live, the blue whale gets that way from its ability to process eight tons of krill a day.

The Antarctic, in its remoteness, girded by pack ice, abloom in summer with phytoplankton and coursing with torrents of krill, was the stronghold of the blue whale. The invention of the steam-powered catcher boat and the explosive harpoon ended all that. Today in the Southern Ocean, where a century ago 200,000 blue whales fed on the krill swarms of austral summer, only a few hundred are left. (Related: "Catching Copepods: Charasmatic Microfauna of the Arctic")

A Game of Chinese Boxes

If William Blake thought he had seen "dark satanic mills" in England, then he should have taken a stroll through Grytviken. After the darkness of the whaling station, and the black, snow-seamed rock of the encircling mountains, and the somber sky, the white interior of the British Antarctic Survey laboratory was dazzling.

For a moment I lost my bearings. Bright fluorescent light glinted from microscopes. Martin Collins turned away on a swivel stool from his laboratory workbench and stood to greet me. In his immaculate white lab coat he was incandescent, an angelic figure of medium height, pale-skinned, with semi-curly hair of indeterminate color. This might have been the start of the Rapture, with Collins as my heavenly guide—until I chanced to glance down. Beneath his white lab coat the ecologist was wearing muddy trousers and gumboots streaked with penguin guano.

He mimed an apology for not shaking hands, holding up both of his own to show blue rubber gloves. Just now he had been rooting around in fish stomachs. Pulling over a bucket of offal, he groped about inside and extracted a half-digested mackerel icefish. "That's come out of a skate's stomach," he said.

"A little worse for wear," I suggested.

Collins agreed and he dug again in the offal, searching for a more intact specimen. His bucket of guts was bloody, but not in the normal, crimson sense, for icefish have no hemoglobin. Their plasma is full of antifreeze but no red cells, so their blood runs clear.

"This one's probably slightly better," he said, holding up a less eroded fish. "There's a fishery for these mackerel icefish. We've done a trawl survey for icefish all around South Georgia to estimate the stocks. Icefish are krill feeders—80 percent of their diet is normally krill—so their stomachs can tell us what's happening with krill. I've done something like 650 icefish in the last couple of weeks. It's been a slightly strange year for the krill around South Georgia."

"Strange," I said. "In what way?"

"You get odd years, and 2004 was one of those, when there's a little bit less krill. This year seems to be fairly extreme. There's very little krill and scarcely any icefish at all. We're seeing the gentoo penguins struggling a little bit this season, as well. Not enough krill. The gentoos don't seem to be giving the food to their chicks that they normally do."

From his workbench Collins retrieved a glass dish of krill. He had extracted this handful—eight or nine little shrimplike crustaceans—from the stomach of an icefish, which he had previously extracted from the stomach of a skate, and had counted, weighed, and measured each one.

In death the krill were bright red. They were big Euphausia superba, the king of krill, probably the most successful species on Earth by measure of sheer biomass: roughly twice the weight of humanity, thronging in "swarms" as dense as 10,000 individuals per cubic meter.

In Norwegian, kril means "small fry." The noun is almost always a collective plural in that language, as it is in English. And as it is in the grammar of Nature herself, where krill are collective like no other organism. The name has an onomatopoeic rightness; "krill" seems to boil, seethe, swarm.

Collins's game of Chinese boxes—his opening of stomachs to investigate the stomachs within—had ended with this dish of krill. No further dissection was necessary, for krill are translucent, and the green contents of the gastric mill and the hepatopancreas were visible through the exoskeleton. In the middle of krill mating season, the last meal—interrupted by a hungry icefish—for these krill had been phytoplankton. More

 

Overfishing Threatens Critical Link in the Food Chain - Earth Policy Institute

The fish near the bottom of the aquatic food chain are often overlooked, but they are vital to healthy oceans and estuaries. Collectively known as forage fish, these species—including sardines, anchovies, herrings, and shrimp-like crustaceans called krill—feed on plankton and become food themselves for larger fish, seabirds, and marine mammals.

Krill

Historically, people have eaten many of these fish, too, of course. But as demand for animal protein has soared over the last half-century, more and more forage fish have been caught to feed livestock and farmed fish instead of being eaten by people directly. A growing body of scientific evidence suggests that current fishing levels are dangerously high—both for the forage fish themselves and for the predators and industries that depend on them.

Found from the tropics to the poles, forage fish typically travel in dense schools of thousands or even millions of fish. While this is effective for guarding against ocean predators, it makes them easy prey for modern fishing fleets equipped with purse seine nets that can cinch up an entire school at once. What’s more, forage fish stocks are highly sensitive to environmental change and prone to population crashes, so fishing levels considered safe in good years can be disastrous in bad ones.

Many of the world’s largest fisheries focus on forage species, including Peruvian anchovy, Atlantic herring, and chub mackerel. Together, forage fish typically account for more than 30 percent of the 80 million tons of fish caught annually in the world’s oceans and estuaries. Roughly 9 of every 10 tons of forage fish hauled in are destined for the “reduction” factory, where they are cooked and pressed to extract the oil; what remains is then dried and milled into fishmeal, a high-protein brownish powder. About 6 million tons of fishmeal and 1 million tons of fish oil are produced each year. Nearly all of the fishmeal is fed to farmed fish, pigs, and poultry. The oil, high in omega-3 fatty acids that are prized for their health benefits, is a popular feed additive and is also used as a nutritional supplement for humans.

Notwithstanding their large contribution to the world fish catch, recent research suggests that forage fish are worth at least twice as much in the ocean as they are on the boat. In 2012 the Lenfest Forage Fish Task Force, an international group of 13 distinguished marine and fisheries scientists, released the results of a three-year study in a report entitled Little Fish, Big Impact. The authors calculated that forage fish generate nearly $17 billion per year in reported catch—$5.6 billion for the small fish themselves and $11.3 billion in landings of the fish that eat them. This does not include the value of ecotourism for watching whales, which eat forage fish; the value of recreational sport fishing where forage fish are used as bait; or the important role of forage fish in keeping plankton under control.

Forage fish have a long history of being targeted for meal and oil. For example, Atlantic menhaden—herring and sardine relatives that migrate along the U.S. Atlantic coast—were first sent to processing factories in New England and the mid-Atlantic region in the mid-1800s to become fertilizer and a cheap substitute for whale oil, which was used in everything from leather tanning to cosmetics. Menhaden meal was later used in animal feed, beginning in the early 1900s. (Around that time, North Europeans started fishing Atlantic herring for the same purpose.) Still used mainly in feed but also in health supplements, Atlantic menhaden are one of the largest U.S. fisheries by weight today.

As more pork and poultry producers in the United States and Europe began using inexpensive fishmeal in feed rations, landings of forage fish grew. When the large-scale Peruvian anchovy fishery was launched in the 1950s and Peru and Chile began to aggressively exploit the productive waters along the western coast of South America, fishmeal use in feed began to spread worldwide. For decades now, the Peruvian anchovy has been not just the world’s largest source of fishmeal, but the world’s largest fishery overall, in some years topping 10 million tons. Peru alone has some 1,200 vessels supplying anchovy to 140 reduction factories, which produce meal and oil worth about $2 billion per year in exports.

While the Peruvian anchovy fishery is indeed lucrative, it is also, like many other forage fisheries, highly dependent on favorable environmental conditions. Especially during El Niño events, warm Pacific Ocean waters—sometimes with overfishing as an accomplice—have over the decades led to numerous anchovy population crashes and devastated harvests. In October 2012, Peru cut the allowed anchovy catch to its lowest level in 25 years after the fish’s population plummeted yet again, likely due to warmer ocean temperatures. With the anchovy supply thus restricted, the world price of fishmeal jumped to a record high by December. (See data.)

A half-century earlier, the young but already massive Peruvian anchovy fishery illustrated the ecological repercussions of heavy forage fishing. Unfavorably warm waters and an anchovy catch averaging 8 million tons per year depleted the food base for cormorants, gannets, and pelicans in the mid-1960s. Severe population declines among these birds ensued. Cormorants, almost entirely reliant on anchovies for food, saw an 89 percent drop from their historical average. Seabird populations in this ecosystem still have not recovered.

Worldwide, three quarters of the 72 marine ecosystems studied by the Lenfest Task Force contain predators dependent on forage fish for at least half their diet. Some predators, including the blue whale, Humboldt penguin, and yellowfin tuna, rely on forage fish for at least 75 percent of their diets. For these animals, plummeting prey populations can mean both impaired breeding and starvation.

The vast majority of the world’s forage fish stocks are either considered fully exploited, with no room for safely increasing the catch, or they are already overfished and in need of rebuilding. Given the climate sensitivity of forage fish and the key ecological role they play, the Lenfest authors recommend that, in general, catches should be half their current levels.

Reducing demand for fishmeal and oil will largely depend on the aquaculture sector. Twenty-five years ago, pigs and poultry accounted for 80 percent of world fishmeal consumption. By 2000, this share had dropped to 60 percent. But over the next decade, aquaculture production doubled, fishmeal prices rose nearly four-fold, and pig and poultry producers rapidly replaced fishmeal in feed with soybean meal. Today 68 percent of fishmeal goes to fish farms, as does 74 percent of fish oil.

There are some encouraging signs on this front, however. For example, nearly every major type of farmed fish—from salmon to carp—has seen significant reductions in the fishmeal content of feed since the mid-1990s as proteins from plants (particularly soybeans) and livestock and poultry byproducts have increasingly become suitable alternatives. Between 1995 and 2007, the fishmeal content in shrimp feed dropped from 28 percent to 18 percent. The drop was even more dramatic for salmon, from 45 percent to 24 percent. The recent surge in fishmeal prices is forcing even more feed switching.

There has also been a rise in the use of seafood industry byproducts in fish feed. In 2010, one third of fishmeal production came from fish trimmings and other food fish production wastes. On the other hand, finding substitutes for fish oil rich in omega-3s has been more difficult and may prove a bigger obstacle to lowering the forage fish catch in line with scientific advice.

Some scientists and chefs have promoted greater consumption of forage fish directly as food, noting that this is much more efficient—and more accessible to poorer consumers—than eating them indirectly through farm-raised salmon or shrimp. Forage fish already provide an important protein source in many low-income countries around the world, especially in coastal Africa. In fact, they account for over half the supply of food fish in 36 countries, including the Maldives, the Philippines, and Ghana. And direct consumption is on the rise in some countries. For example, Peruvians ate 190,000 tons of anchovies in 2010—19 times as much as in 2006. More