For decades, Antarctic fish have drawn scientists from all over the world to study their strange polar adaptations. Few people would have seen any potential for eating or harvesting these bizarre fish. I had studied fish for years, but had seen nothing like Antarctic dragonfish (Family Bathydraconidae). Some with leopard print, thick leather-like skin and blunt triangle heads that culminated with a jagged underbite. Nor had I ever gutted a fish so clean as an Icefish (Family Channichthyidae), fish that lack hemoglobin – a peculiar polar adaptation that gives them clear white blood. With one quick slit up their belly, clear fluid spilled out and their white gills were sobrilliant. In one trawl we found a small speckled purple fish with a long fleshy barbell snaking off its chin. I held it delicately in my hand as everyone snapped photos; no one had ever seen one before. We coined it “species A.”
Our nets were also full of fish from the family Nototheniidae, the most diverse family of fishes in the Southern Ocean. While most of the notothenoids don’t look particularly strange, their physiological adaptations are extraordinary. These fish proliferate in the frigid Antarctic waters by producing anti-freeze proteins that keep their blood from crystallizing.
Most of the fish were small and slender, usually 10 to 30 centimeters, until we caught an Antarctic toothfish (Dissostichus mawsoni), a fish that grows to more than two meters in length, making them the largest and most dominant fish in the Southern Ocean. On deck I picked up the toothfish – so heavy and dense outside of its water world. But once we placed it in a tub of water for a quick buoyancy test, it floated perfectly neutral in the water. Most fish use a swim bladder (filling it with air to stay aloft in the water column) but toothfish use lipids (or fats) to achieve perfect buoyancy with zero effort.
But I wasn’t here to study any amazing Antarctic piscine adaptations. I was a graduate student studying the life history of toothfish (also known as “Chilean sea bass”), heeding a request made by the Southern Ocean management body, CCAMLR (the Convention of the Conservation of Antarctic Marine Living Resources) in an effort to manage the growing fishery.
Harvesting the Southern Ocean
It may come as a surprise that some fish in our local grocery stores come all the way from Antarctica. Indeed it makes little sense to use so much gas, time and energy traveling to the most remote corner of the earth in pursuit of fish. But our fisheries closest to home have been over exploited and can no longer meet the needs of a growing world population, hungry for fish.
Recent United Nations Food and Agriculture Organization statistics show that 80 percent of global fisheries are fully exploited, overfished, or collapsed while another 18 percent are moderately exploited. That leaves only two percent of our world fisheries undeveloped, including some stocks of Antarctic toothfish. Fishermen are constantly forced to into deeper and more remote waters to keep up with world demands and continue fishing, with or without a license to do so.
In the 1960s, fisherman began trawling around the sub-Antarctic islands, mostly for Notothenia rossi (the marbled rock cod) and some species of Icefish. Catches rose steadily, and by 1990, marbled rock cod populations plummeted to five percent of their pre-exploitation level.
With these shallow water species exhausted, fishermen began targeting the deep-water Patagonian toothfish – the northern cousin of the Antarctic toothfish. Equal in its length and full of the same fatty lipids for buoyancy, the fish was marketed as Chilean sea bass, and quickly became a popular menu item in up-scale restaurants. But legal commercial fishermen weren’t the only ones interested in tapping this new gold mine; pirate fishermen also wanted their share. Within ten years local populations of Patagonian toothfish declined and stock closures ensued.
To keep up with market demands, fishing boats pressed into the southernmost reaches of Antarctic waters in pursuit of the Antarctic toothfish. With retail prices at more than $20 per pound (USD, about $70 kilo NZD), the fishery plunders on despite stock depletions and the potential vulnerability of both species of toothfish.
The problem with deep-sea fisheries
As a graduate student in 2007, I attended a symposium on deep-sea fisheries in San Francisco. I listened in earnest, scribbling down notes as all the fishery biologists on the panel – including world renowned fishery experts like Daniel Pauly – stood up and talked about the vulnerability of deep-sea fisheries. Deepwater fish tend to grow slowly, live a long time, mature later in life and have low fecundity (reproductive capability). The symposium led to a clear conclusion: deep-sea fisheries are not resilient to heavy commercial exploitation. In the past we’ve realized this far too late, long after the deepwater fishes had been over-harvested.
Toothfish, which occupy the deep waters of the Southern Ocean are among these slow-growing and long-lived fish — 50 years for the Patagonian species and about 40 for the Antarctic species, the latter of which was confirmed by my graduate work. We still don’t know at precisely what age toothfish mature, but its likely well into their teen years. Because many are caught long before that, they will never have a chance to reproduce and propagate the population. We also still know very little about where and when exactly they spawn. Incredibly, to date no one has found a larval Antarctic toothfish.
Given the trends of Antarctic and deep-sea fisheries, the chances that toothfish could withstand heavy fishing pressure seem slight. Toothfish are the largest fish in the Southern Ocean; decimating their population could be damaging to the entire Antarctic ecosystem. Scientists in the Ross Sea, the primary region for the Antarctic toothfish fishery, have formally pleaded to the Antarctic managing body to stop the fishery. For the last few years they’ve no longer been able to catch enough toothfish to continue the research they’ve been doing for decades.
Under the Antarctic Treaty, the Antarctic continent is fully protected as a place for international peace and science. Exploitation is strictly forbidden. Yet the treaty only applies to the land, leaving the waters around the continent part of the global commons. But don’t these waters, teeming with animals found nowhere else on the planet, deserve the same protection? Do we really have any business commercially harvesting fish that come all the way from Antarctica?
Cassandra Brooks is marine scientist and science writer and is the USA Coordinator for The Last Ocean. She began studying life history and population structure of the Antarctic toothfish as a graduate student at Moss Landing Marine Laboratories in Moss Landing, California.