Undersea Volcanoes in Deep Trouble, Eco-Groups Say

James Owen
for National Geographic News

December 11, 2003

Rising from the depths of the North Atlantic, seamounts are described by
conservationists as oases of life. The underwater volcanoes harbor a
vast array of deep sea creatures, many of them still unknown to science.
They also attract large numbers of fish, which in turn have attracted
the attention of commercial fishing fleets. Environmentalists now say
such attention could destroy these precious ecosystems.

A report published last month identifies commercial fishing as the major threat to the biodiversity of seamounts in the North Atlantic, while marine scientists are calling for urgent conservation action to protect seamounts worldwide.

The report was published jointly by World Wildlife Fund (WWF) Germany and the Oceanic Seamounts: An Integrated Study (OASIS) project. The latter involves marine scientists throughout Europe and is funded by the European Union. The study aims to shed light on the natural history of seamounts in the northeast Atlantic Ocean and their contribution to the ecology of the surrounding ocean.

Many important commercial marine species congregate on seamounts, according to the report's author, Susan Gubbay, an independent marine ecologist based in the U.K. They include the black scabbard fish (Aphanopus carbo), blue ling (Molva dipterygia), morid cod (Mora mora), orange roughy (Hoplostethus atlanticus), shovel nosed shark (Deania calceus), and tusk (Brosme brosme).

Gubbay writes that the fish species "have been the targets of intensive exploitation" through a variety of commercial fishing methods, including longline fishing, mid-water trawling, and bottom trawling that can operate at depths of more than 1,500 meters (4,900 feet).

Scientists say such exploitation has been fueled by the collapse of shallow-water stocks due to overfishing. This switch of focus to offshore waters is blamed for population crashes in fish like the orange roughy and blue ling, which gather in dense shoals around seamounts and are easily targeted by trawlers. In the northeast Atlantic these trawlers come mainly from France, Ireland, the Faroe Islands, Greenland, and Norway.

The report also highlights concerns over other vulnerable deep sea fish inadvertently taken as by-catch. "One ton of fish is discarded for every ton of fish landed," Gubbay wrote.

Ancient Corals

While baited longlines can stretch 50 kilometers (31 miles) and carry over a thousand hooks, scientists consider bottom trawling, in which large, weighted nets are dragged along the seafloor, to be most damaging to seamounts. The method destroys or disturbs delicate, slow-growing seabed communities. For instance, some cold water coral reefs discovered on seamounts are believed to be more than a thousand years old.

Seamounts are cone-shaped, volcanic mountains that rise as much as five kilometers (three miles) from the seabed and can measure 100 kilometers (62 miles) across. There are over 800 of them in the North Atlantic alone. Often they are isolated, and, like some of their counterparts on land, scientists suspect they support large numbers of endemic species. Up to 50 percent of species observed during recent explorations to seamounts have been new to science.

The steep slopes of the deep sea mountains amplify ocean currents, providing ideal conditions for corals, sea-anemones, and other suspension feeders that attach themselves to rock faces. Plankton concentrations are higher than elsewhere, laying the foundation for a food chain that builds to big fish predators such as swordfish (Xiphias gladius) and shark species. Seamounts are also considered important nursery areas for deep sea fish.

Like the corals and sponges, many of these fish are long-lived and slow to mature. For instance, the orange roughy can live 150 years, and takes 25 to 30 years to reach sexual maturity. Conservationists say this makes the fish particularly vulnerable to overfishing.

Also known as the deep sea perch, the species was first targeted in the northeast Atlantic in 1991, with annual catches soon hitting 5,000 tons (4,500 metric tons). But within three years, catches fell 75 percent as numbers dwindled, according to the WWF.

A second report, also released last month by the WWF and TRAFFIC, an international wildlife trade monitoring network based in Cambridge, England, called for immediate action to halt the global collapse in orange roughy stocks.

"Unsustainable Levels"

Anna Willock, TRAFFIC's senior fisheries advisor, said: "In 25 years of commercial fishing for this species, over one million tons of orange roughy have been caught. These levels have proven to be unsustainable and yet…management has failed to act responsibly."

WWF marine policy officer Helen McLachlan added: "This is just one example of deep sea species we need to protect. There are a myriad of deepwater species associated with seamounts which are also under threat. The future development of deep sea resources must be conditional on a full and transparent assessment of the risks involved if we are to avoid more and more species facing commercial extinction in years to come."

Fishing nations criticized in the orange roughy report include New Zealand, where up to 70 percent of the orange roughy catch is taken on seamounts.

New Zealand government fisheries scientist John Annala concedes that during the 1980s, allowable catches turned out to be unsustainable. But he noted: "Subsequent research showed orange roughy was a very unusual species, long-lived and slow to reproduce. When we found this out we took major action, developing a 20-year rebuild strategy. That strategy has been enormously successful and has seen stocks recover to or towards sustainable levels."

Meanwhile, the International Council for the Exploration of the Sea (ICES), an intergovernmental organization based in Copenhagen, Denmark, which promotes marine and fisheries research in the North Atlantic, states: "Little is known about seamount ecosystems in the [Northeast] Atlantic, or the impact of human activities upon these unique oceanic ecosystems, mainly due to lack of funding for research into these systems."

With the search for new seamount fishery locations and potentially marketable deep sea species continuing, the creation of Marine Protected Areas (MPAs) through international agreements is seen as a conservation tool that could help safeguard seamounts.

Gubbay says a MPA program for the northeast Atlantic is currently being developed by the Commission for the Protection of the Marine Environment of the North-East Atlantic, an alliance of 15 European countries, though it remains unclear how the program will be implemented.

These protected zones can be introduced horizontally, so that upper levels may continue to be exploited commercially, while the deeper ocean, areas below 500 meters (1,640 feet), for example, become off-limits to trawlers.

A total fishing ban on some seamounts must also be considered, Gubbay concludes, if these mysterious deep sea wildernesses are to be preserved.