FEATURE
Sustaining
Global Fish Stocks
Despite conflicting views on harm from trawling and overfishing, experts agree that changes in fishing practices are necessary. K R I S C HRISTEN
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s fisheries collapse the world over, particularly along shallower, more easily accessible continental shelf areas, fleets are resorting to advanced technologies to locate and catch ever scarcer prey in deeper waters, some more than a mile deep. At any given moment, satellite systems can provide daily u p dates on where fish are collecting; global positioning systems can precisely locate these areas; and fish finders can identify how many fish are in a given spot. Once fish are located, heavily weighted nets are often dragged over the targeted area. The resulting seafloor damage and unnecessary loss of marine life can be enormous (see photo pair on page 454). In a single pass the huge nets can mow down and destroy or damage vast amounts of structure-forming corals sea anemones tubeworms mussels and other organisms Along with the intended species catch large quantities of untargeted marine fish and m a m m a l s are entangled in nets raised to the © 1999 American Chemical Society
ocean's surface—as much as one-third of the worldwide marine catch is thrown back each year. Many, sometimes all, of these discarded plants and animals die as a result of being removed from their habitat (i). Marine scientists researching the ecological effects of this race to catch fewer and fewer fish question whether the marine habitat destruction that comes with such fishing practices may be severely impacting the recovery ability of both the fish stocks and marine ecosystem taken as a whole. According to Paul Dayton, a professor of marine ecology at the University of California-San Diego's Scripps Institution of Oceanography, fishing has a far greater impact on the marine ecosystem than nonpoint source runoff, habitat loss, or natural climate change combined. Research papers appearing in the December 1998 issue of Conservation Biology compare bottom trawling and dredging to the practice of forest clearcUtting. "The seabed is covered and honeycombed with structures," said Elliott Norse, president of the Ma-
rine Conservation Biology Institute and coauthor of one of the papers. Logging, which is like dragging the seafloor with heavily weighted nets, crushes, buries, and exposes organisms to predators or removes them outright and dramatically degrades habitat quality in the process, Norse explained. Fishing in deep seas disturbs a marine environment quite different from that of shallower shelf waters. "The problem is that these deeper waters have ecosystems that naturally receive less disturbance," Norse said. Whereas the sea surface is often roiled by winds and currents, "further down, things are a lot quieter, and species that dwell there are less equipped to withstand disturbance or recover from it," he added. According to the National Oceanic and Atmospheric Administration (NOAA), mobile fishing gear may be the most common source of disturbance in deeper waters where natural events such as storm waves rarely affect the bottom. Effects can be longlasting, because some deep sea inhabitants, such as NOVEMBER 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 4 5 3 A
(Left) On this undisturbed seabed, the bottom is densely covered with the tubes of polychaete worms and a flounder swimming about. (Right) After the single pass of a scallop dredge, more than 90% of these worm tubes are gone, one lone scallop remains, and the dredge's tracks are clearly visible.
ocean quahog clams and sea fans, which can live for more than 200 and 500 years, respectively, are slow to repopulate and rebuild their structures in disturbed areas. Several efforts are underway to address these problems; creation of no-take reserves within the national marine sanctuaries is one such venture. Given large existing gaps in scientific knowledge about the world's fisheries and their ability to recover, it remains to be seen, however, whether these
Untargeted species In addition to the fish, scallops, mussels, oysters, or sea urchins that commercial fishermen may be trying to catch, their nets also bring up a number of other species known as bycatch. This includes "economic" and "regulatory discards," which are those species that are too small, the wrong sex, of bad quality, of no commercial value, or are caught when the season is closed, as well as prohibited species, such as marine mammals or species that might be the target of other fisheries. The problem is prevalent in virtually all fisheries. Depleted fish stocks could be more the result of bycatch than the direct result of habitat damage caused by trawling according to Shipp Shrimp trawls are "far and away" the worst fishing industry in terms of bycatch, Shipp said, noting that the shrimp bycatch ratio is generally between 2 and 5 times the amount of actual shrimp caught. He noted further that bycatch is also a major problem with the longline fishery, which sets out nets that primarily target swordfish. "Even though the tonnage isn't as great as in the shrimp fishery, there's a tremendous amount of billfish [such as marlins and tuna] bycatch. Those particular species are of such great value, that this is a serious problem," Shipp said. Likewise, ghost fishing, or lost gear that continues to function, often captures marine life for years, even decades, after it was lost. Some estimates find that as much as a quarter of the fishing aear used is eventually lost. Davton said.
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initiatives will prove sufficient to mitigate the harmful effects of current fishing practices and assure sustainable fish harvests in the future. Long-term harm? Underwater before-and-after photos of an area that a trawler or scallop dredge went through "are hard to argue with," noted Justin LeBlanc, vice president for government relations with the National Fisheries Institute, a trade association representing the fish and seafood industry. "You see an absolutely astounding difference in habitat structure and complexity because much of the biology of that area is taken up in the net," he said (see photo pair on page 456). But LeBlanc questioned whether the longterm impacts of such disturbances can fairly be compared to clearcutting. "The boundaries in the ocean ecosystem are much more fluid [than in a forest], and general marine biology and marine ecology suggest that those areas would be recolonized relatively quickly," he asserted. Others also question whether long-term ecological impacts necessarily go hand-in-hand with trawling. Steve Hughes, president of Natural Resources Consultants, Inc., in Seattle, Wash., who does annual biomass estimates of individual fish stocks in Alaska for the federal government, reported seeing no adverse effects on habitat associated with trawling vessels. "The vast majority of our fisheries occur in the Bering Sea or Gulf of Alaska where a sand and gravel substrate is predominant, not in-shore, where all these pretty littie creepy-crawly dungs live," Hughes said. Large factory trawlers far at sea bring in most of the Alaska catch. On smooth, muddy bottoms, trawling probably does not have a tremendous amount of impact on biodiversity either, at least not on the immediate area, said Robert Shipp, a professor in the University of South Alabama's Department of Marine Sciences in Mobile. "The negatives come from the water turbidity that results," he said—in adjacent areas harboring submerged vegetation, such as a grass bed, where reduced light penetration could cause those areas to fail.
Effects can be complicated in other ways. The pass of a trawl or dredge can resuspend sediment plumes, potentially increasing nutrients in bottom waters and enhancing phytoplankton productivity (i). A study conducted in deep waters of the heavily trawled Gulf of Maine found that effects associated with sediment resuspension were minimal. "But in a shallower system, the potential for those nutrients to get to the surface and potentially affect production is greater than in a deeper water system," said a coauthor of the study, Cynthia Pilskaln, an associate professor of oceanography at the University of MaineOrono. This thought is especially intriguing since most bottom trawling is conducted in areas significantly shallower than the Gulf of Maine, and many studies have shown high bacterial activity in resuspension layers in other areas Pilskaln said Missing science "It's obvious diere have been habitat changes due to trawling in some areas (see Figure 1), and in a few cases, there's evidence to indicate that it's detrimental, but most of it is circumstantial," said Andrew Rosenberg, deputy assistant of the National Marine Fisheries Service (NMFS). NMFS is the primary agency responsible for managing and sustaining marine resources and their habitats. "It's not enough to say you saw that a trawl stirred up the bottom; what you have to do is be able to relate that to an effect on a fish population as a whole," Rosenberg said. "What are the long-term impacts of these changes— are they going to decrease fishery productivity? Are they decreasing essential fish habitat or total ecosystem health?" Rosenberg asked. So far, surprisingly little research has been undertaken on what kinds of long-term effects fishing activities may be inflicting on marine biodiversity and whether declines in the abundance of particular commercial species like cod and haddock are the result of habitat loss as much as they are the result of overharvesting. Moreover, the baseline data being used to determine these effects have been taken from marine ecosystems that have already been severely altered through decades of fishing as in the Gulf of Mexico, one of the most heavily trawled areas of the world. Some initiatives are being undertaken to provide more meaningful information. The Gulf of Mexico Council, for instance, recently made research on the impacts of trawling one of its primary objectives after realizing that little information existed, said Shipp, who is a member of the Council. The organization is one of eight regional fishery management councils mandated under the 1976 Magnuson-Stevens Fishery Conservation and Management Act to develop fishery management plans in federal waters. The original purpose of the Magnuson-Stevens Act was to force foreign fishing fleets out of U.S. waters. The act was amended in 1996 with a mandate to end overfishing and minimize bycatch by the U.S. fishing fleet, as well as to identify and protect essentialfishhabitat, with die goal of rebuilding stocks and managing them for long-term sustainability.
FIGURE 1
The damage caused by trawling Huge quantities of nontarget species are taken and extensive seabed damage results when large weighted nets are dragged along the seafloor by fishing trawlers and dredges.
Source: Joe Shoulak.
Response measures inadequate There is no uncertainty surrounding whether or not overexploitation is occurring. Using statistics from the United Nations Food and Agriculture Organization (FAO), the primary source of global information on the condition of fisheries, a 1999 study by the U.S. National Research Council concluded that globally, some 30% of individual fish stocks are overfished, depleted, or recovering, and another 44% are being fished at or near the maximum long-term potential catch rate (2). Important commercial stocks being overfished in U.S. waters include cod, haddock, and yellowtail flounder off the New England coast; chinook, coho, sockeye, pink, and chum salmon off the Pacific coast; and king mackerel and red snapper in the Gulf of Mexico (3). This is a cause for concern: On average, humans obtain 16% of their animal protein from seafood (4). However, reducing thefishcatch and rebuilding individual stocks are contentious issues, often carrying wrenching socioeconomic and political ramifications. Moreover, as fish stocks decline further, market prices for them can rise, increasing the pressure to fish, especially in developing countries (cf. (2), p. 13), which increased their proportion of the global catch from about 40% to 65% from 1973 to 1993 (cf. (2), p. 20). As a result, efforts to turn the fish decline around have been slow and met by a lot of resistance. Environmentalists charge that plans created by the eight regional fishery management councils and approved by the NMFS are "woefully inadequate" for achieving the goals of the 1996 amendments to the Magnuson-Stevens Act. An evaluation of the plans earlier this year by the Marine Fish Conservation Network and the Center for Marine Conservation noted that whereas the councils did a "decent" job of identifying essential fish habitat, none of the councils injected anything into the plans to reduce the harmful effects of fishing on marine habitats. In addition, NOVEMBER 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 4 5 5 A
(Left) Before a trawler passed through, this gravel bottom on Georges Bank in New England was covered with structureforming organisms such as sponges, corals, moss animals, clams, and crustaceans. (Right) After a trawler passed through, only a bare gravel bottom remains.
"bycatch (see sidebar on page 454A) garnered little or no attention from any of the councils," the report found. One issue that greatly frustrates the regional management councils is that the 1996 Sustainable Fisheries Act [the a m e n d m e n t to the M a g n u s o n Stevens Act] fails to take overall ecosystem impacts into consideration, LeBlanc said. For instance, as groundfish stocks in New England were increasingly overfished through the years, the dogfish biomass grew substantially. In response to that population shift, fishing then began on dogfish resources, and pressure to do so has increased in recent years, LeBlanc explained. Under the 1996 amendments, the New England Council must implement a dogfish rebuilding program that will maintain dogfish biomass at this new high level, which occupies niche space that cod and haddock could be filling.
Toward sustainable fishing Since 1972 (100 years after the first terrestrial national park was created) the United States has designated 12 underwater national parks as offshore protected areas. Together, they e n c o m p a s s nearly 18,000 square miles—nearly the size of Vermont and New Hampshire combined—of ocean waters and habitats. Although the reserves are protected from such practices as oil drilling and gravel mining, the fishing industry has long fought efforts to restrict fishing in them. Commercial fishing is currently allowed in all but one of these reserves. Highlighting some of the difficulties involved with area closures, Rosenberg said, "It's easier when you close an offshore area that is only accessible to larger boats that can more easily move to odier areas. It's much harder when you close a large near-shore area, because small-boat fishermen have nowhere to go. When you start making allocation decisions like that, it gets very complicated." But fishermen may not have a choice. Since the Magnuson-Stevens Act passed in 1976, "The council system has been managing the business side [of fisheries], working to make a profit [for fishermen] 4 5 6 A • NOVEMBER 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
every year, while [addressing] die biological side at the same time," said Tatiana Brailovskaya, a research associate with The Nereus Project, a nonprofit group of independent researchers. "The evidence isn't a ringing endorsement of our fishing management system, [but] rather than get rid of everything, let's at least have some areas that are preserved for their own sake and are intact and off limits. If you wait until you can prove irrefutably in science that [such a reserve system] works, you risk losing it." The national marine sanctuaries would be a good place to start, but "the more you can have mem contiguous, like wildlife corridors on land, the better," said Brailovskaya, who has studied the obstacles marine reserves face. She mentioned the situation in New Zealand as proof of the benefits marine reserves can offer. "They're at a point where commercial fishermen themselves are advocating for more no-take reserves because they see the difference in the amount of fish available to them on the outside," she said. Some of the principal stocks of the New England fishery, which have been the most devastated in the United States, are slowly showing signs of recovery through a combination—hotly contested by the fishing industry—of gear restrictions, limits on fishing time, and area closures, most notably Georges Bank, a famous fishing ground, Rosenberg said. Cod, however, is still hovering on the brink between recovery and continuing depletion. Shipp and Dayton are convinced that reserves can definitely aid recovery of the more sedentary stocks that are severely overfished. In fact, said Dayton, "There should be no fishing until there is good evidence that proposed fishing is sustainable and only involves direct impacts that are sustainable. The burden properly should be on those exploiting society's resources to at least offer the preponderance [of evidence] tiiat their profitable exploitation is sustainable." For highly migratory species, such as mackerels, dolphins, and tuna, however, Shipp questioned whether reserves would do much to help. For migratory species, it would likely be necessary to set
aside 50% of ocean waters as protected reserves, he said. "That probably isn't doable, but for sedentary species, 10-15% may be all that's needed," he remarked. In 1997, more than 1600 scientists issued a signed statement calling for 20% of the world's coastal and offshore waters to be protected from all possible harm, including fishing. And in April, NOAA, the National Geographic Society (NGS), and the Goldman Fund, a private foundation, launched the Sustainable Seas Expedition to study the nation's current network of marine sanctuaries. The five-year program, led by Sylvia Earle, NGS's explorer-in-residence and former chief NOAA scientist, is using developed submersible technologies to explore and establish underwater monitoring programs and long-term observations. Earle, long a champion for more and better protected marine reserves, said earlier this year at a congressional briefing, "If ducks and geese had been captured by dragging trawls through marshes, or if songbirds were taken by bulldozing forests, or squirrels captured by dynamiting their trees, or buffalo obtained by gathering them in nets along with rabbits, lizards, shrubs, and clumps of prairie grass, the catch for market of these creatures would have ended much sooner than it did. The same principle applies to cod, halibut, tuna, sharks, crabs, oysters, and clams, but we're still trying to capture them with heavy-handed techniques." Convinced that reducing global fishing capacity
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is key for long-term, economically healthy fisheries, the United States has pushed for and obtained agreement within the U.N.'s FAO for a voluntary international plan of action calling on all member nations to address the excess fishing capacity that is leading to unsustainable fishing practices in their nations, Rosenberg said. "We're also discussing this within the World Trade Organization because this relates to issues of fishing vessel subsidies," he noted. Many nations have provided both direct and indirect subsidies, which has created the economic, social, political, and biological pressures that result in overfishing, LeBlanc said, adding that "because the U S fishing industry is likely be the least subsidized fleet in world we strongly siiDport efforts to address fishing subsidies that lead to overcapacity" References (1) Brown, S. K.; Auster, P. J.; Lauck, L.; Coyne, M. Ecological Effects of Fishing; National Oceanic and Atmospheric Administration. http::/state-of-coast.noaa.gov/bulletins/ html/ief_03/ief.html (accessed July 1999). (2) Sustaining Murine Fisheries, National Research Council, National Academy Press: Washington, DC, 1999; p. 3. (3) Status and Trends of the Nations Biological Resources, Volume 2; U.S. Geological Survey, U.S. Government Printing Office: Washington, DC; p. 847. (4) Platt-McGinn, A. Charting a New Course for Oceans. In State of theWorld; WorldWatch Institute: Washington, DC, 1999; p. 78.
Kris Christen is an assistant editor or ES&T.
THE ROYAL NETHERLANDS A C A D E M Y OF A R T S A N D S C I E N C E S CALLS FOR N O M I N A T I O N S FOR THE
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