Did you know? The heat in the upper six miles of the earth’s crust contains 50,000 times much as energy as found in all the world’s oil and gas reserves combined. Despite this abundance, only 10,500 megawatts of geothermal generating capacity have been harnessed worldwide. For more information view the text and data in Chapter 5 of Plan B 4.0: Mobilizing to Save Civilization.
After decades of growth, the reported global wild fish catch peaked in 2000 at 96 million tons and fell to 90 million tons in 2003, the last year for which worldwide data are available.* The catch per person dropped from an average of 17 kilograms in the late 1980s to 14 kilograms in 2003—the lowest figure since 1965. (See data.)
As fishing fleets expanded through the late 1980s and as fish-finding and harvesting technologies became more efficient, the world’s fishers have systematically gone after their catch at greater depths and in more remote waters. Over the past 50 years, the number of large predatory fish in the oceans has dropped by a startling 90 percent. Catches of many popular food fish such as cod, tuna, flounder, and hake have been cut in half despite a tripling in fishing effort. According to the U.N. Food and Agriculture Organization, the 4 million vessels scouring the world’s waters are at or exceeding the sustainable yields of three quarters of all oceanic fisheries.
The 10 most-fished species constitute 30 percent of the world’s catch. Seven of these have reached their limits and are classified as fully exploited or overexploited throughout their entire ranges, meaning that we cannot expect to increase their harvests. Included in this group are two types of Peruvian anchoveta, Alaska pollock, Japanese anchovy, blue whiting in the northeast Atlantic, capelin in the North Atlantic, and Atlantic herring. The other three species—chub mackerel, skipjack tuna, and largehead hairtail—are overfished in parts of their ranges.
Interestingly, several of these species became fishing targets only after the stocks of more desirable fish were overharvested. After the collapse of the 500-year-old Canadian cod fishery in the early 1990s, blue whiting catches increased. In the northwest Pacific, the overfishing of Alaska pollock and Japanese sardine led fishers to focus on Japanese anchovy, largehead hairtail, and squid. Some scientists warn that continuing to “fish down the food web” will lead to harvests almost exclusively of bait fish and jellyfish.
The tendency to catch larger and older fish first, leaving those small enough to escape from nets to breed, has over time reduced the average size of those caught. The effect on large predators is striking: for example, in the 1950s an average blue shark weighed 52 kilograms; in the 1990s, the average was 22 kilograms. In addition, fish that breed late in life are sometimes pulled out of the water before they can reproduce. When fish respond to overharvesting by reproducing at earlier ages, recent research shows that their populations are still hit hard because, for some species, the offspring of older fish have a better chance of survival than the offspring of younger fish.
Although fishers generally target specific kinds of fish, they often bring in more than just the intended catch. Some 8 percent of global landings are discarded, returned to the sea dead or dying. Shrimp trawlers, which drag enormous nets over the seafloor and destroy delicate ecosystems, are the most indiscriminate; some 62 percent of their catch is thrown back in the water. And these tallies underestimate the true losses as they only include reported bycatch and do not consider any of the marine mammals or birds that become entangled in fishing gear. Longliners with thousands of hooks on central fishing lines of up to 100 kilometers (60 miles) are estimated to kill some 4.4 million sharks, sea turtles, seabirds, billfish, and marine mammals in the Pacific each year.
Overall, 1 billion people around the world rely on fish as their primary source of protein. While annual fish consumption per person in the industrial countries (at 29 kilograms) is more than twice that of developing countries, three quarters of the fish caught in the wild (by weight) come from developing countries, which also supply 9 out of 10 farmed fish.
Thus fish are one of the most widely traded commodities. Seventy-five percent of the total marine harvest is sold on international markets each year, accounting for some $58 billion in exports in 2002. Japan, the United States, and the European Union are the top importers, bringing in fish caught in foreign seas or farmed in other regions and also sending industrial fishing fleets to empty the waters near developing countries. Off the west coast of Africa, for instance, large European and Japanese ships have displaced smaller boats, leaving little of the catch to feed local people.
The irony is that governments subsidize the destruction of oceanic resources to the tune of $15-30 billion each year. In 2001, subsidies paid to the fishing industry in Japan reached $2.5 billion, equal in value to a quarter of the catch. U.S. fishing subsidies totaled $1.2 billion, exceeding the worth of 30 percent of the U.S. catch. Removing these subsidies could go a long way toward relieving pressure on fish stocks.
While fish stocks historically have been managed on a species-by-species basis, scientists now recognize the need for management of whole ecosystems. This includes setting aside marine reserves where fishing is prohibited altogether. There is no guarantee that a collapsed fishery can recover, but studies of protected areas around the world have shown that some exploited fish populations rebound faster and that individual fish grow larger in and around marine reserves than in unprotected areas. A global network of marine reserves protecting up to 30 percent of the world’s oceans would cost around $13 billion—far less than the subsidies that currently promote overfishing. Such a network would also create some 1 million new jobs and bolster the number of fish that can be caught in nearby waters.
Creating sustainable fisheries also depends on strict fishing quotas and better enforcement to quash illegal fishing. Restricting the most damaging and indiscriminate types of fishing gear and adopting new bycatch-reducing technologies can stop the killing of incidental catch. For example, by modifying the shape of their hooks and switching to a different type of bait, fishers in the Western North Atlantic were able to reduce turtle bycatch by 92 percent and increase the catch of their target species. On the other side of the globe, Australian prawn trawlers have used devices to cut bycatch by more than 60 percent without adversely affecting their catch.
Such measures that boost the resiliency of aquatic populations and ecosystems should work in tandem with broader policies to protect our waters from looming threats like climate change and pollution. Coral reefs, kelp forests, and estuaries—the nurseries of the sea, where young fish develop and biodiversity thrives—are particularly vulnerable. Water temperatures just 1 degree Celsius above the norm can decimate coral reefs, leading to the loss of fish and other animals that depend on them. Global warming is already altering fish habitats, distribution, and migration patterns.
With oceanic ecosystems hitting their limits and demand for fish climbing, the farming of fish in pens and ponds supplies a growing share of the world’s food fish. From less than 1 million tons in 1950, global aquacultural production hit a new high of 42 million tons in 2003, making it the fastest-growing food production sector in the world. Farmed fish production, growing 9 percent a year over the last decade, is offsetting the decline in wild catch, sustaining the total availability of fish at 21 kilograms per person. (See data.)
Nonetheless, aquaculture will alleviate pressure on wild fish only if it is done wisely. The construction of near-shore fish farms frequently requires the razing of sensitive wetlands. These farms also harbor diseases and concentrate fish wastes that can lead to harmful algal blooms and low-oxygen dead zones. Making matters worse, farmed carnivorous fish can eat several times their weight in wild fish, which only adds to pressure on such resources. Though salmon, trout, shrimp, and prawns currently account for just 9 percent of world aquacultural output, production of these carnivorous fish is doubling almost every eight years, rapidly increasing demand on wild stocks.
Better methods of fish farming include onshore mixed-species production of herbivorous fish, like carp. China, which accounts for some 68 percent of world aquacultural production, has developed an efficient carp polyculture using freshwater ponds. Fish farmers in several countries, particularly in Asia and Africa, have even had success growing fish within rice paddies, where the fish need limited or no added feed and their wastes fertilize the grain crop.Modeling future aquacultural endeavors on such lower-impact systems would be an important step toward a more sustainable fish harvest.
Informing consumers about the environmental effects of the fish they eat—whether from the sea or a farm—allows them to vote with their wallets for sustainable food choices. The Marine Stewardship Council, an independent global certification agency, has thus far certified 12 fisheries as sustainably managed, and 263 MSC-certified products are now available in 24 countries. In addition, a number of other organizations, including the Monterey Bay Aquarium and the National Audubon Society in the United States, provide information for the public and restaurateurs on the status of a variety of food fish.
Without careful management, the limits of the world’s fish supply—a resource once thought to be boundless—will become all too clear. Sustaining global fisheries and sound aquacultural practices are in the best interest of fishers and consumers today as well as for the generations to come.
Copyright © 2005 Earth Policy Institute
* Note: Taking into account probable overreporting by China, the world’s largest fisher, as well as climate-related fluctuations in the large catch of Peruvian anchoveta, the global wild catch has actually been falling for longer than the official records reveal—dropping 660,000 tons per year since 1988. For more information see Reg Watson and Daniel Pauly, “Systematic Distortions in World Fisheries Catch Trends,” Nature, vol. 414 (29 November 2001), pp. 534-36.