Oceans and Estuaries - Ocean And Estuarine Fisheries—avaluable Resource

In many parts of the world, fish is the major source of protein in the diet. Humans on average worldwide obtain 16% of their animal protein from fish, and an estimated two billion people worldwide depend on fish for 40% of their protein supply. A staple in the diet of many cultures, fish are consumed in much greater quantities in countries other than the United States. The United States consumes only about 8% of the total world catch of fish and shell-fish. This supply comes from U.S. commercial fishermen, aquaculture producers, and imports.

In the 1990s the United Nations Food and Agriculture Organization (FAO) reported record world marine harvests of more than 100 million tons annually. Fisheries experts believed that the catch had peaked and that future harvests would begin to decline. The FAO supported this finding, claiming that most traditional marine fish stocks had reached full exploitation; therefore an intensified effort was unlikely to produce an increased catch, and any increase would produce a state of over-fishing.

Eighty-two percent of the fish caught in 1996 came from oceans and estuaries. Growing fish, shrimp, and other aquatic species on coastal and freshwater farms ("aquaculture") increased greatly during the 1990s, accounting for twenty-seven million tons in 1996, up from seven million tons in 1984. According to the FAO, aquaculture in 1996 accounted for 26% of food fish. Fifty-nine percent of aquaculture fish were freshwater farmed, while 41% were marine and estuarine farmed. Some scientists and fisheries experts predicted that aquaculture production would surpass the volume of harvest of wild fish in the first twenty-five years of the twenty-first century, but it is doubtful that aquaculture will ever be able to match the variety of species found in oceans and estuaries. According to Fisheries of the United States 2003, published in 2004 by the National Marine Fisheries Service, a part of NOAA, total aquaculture production in the United States in 2002 was 867 million pounds.

For centuries, freedom of the seas was the reigning doctrine, and the waters more than three nautical miles from shore were open to all. After the end of World War II in 1945, there was a boom in marine fishing, and fishermen began to engage in fierce competition over fishing grounds. In the 1970s, as conflict mounted, the world took a step toward curtailing fishing freedom on the high seas. As part of the Third United Nations Conference on the Law of the Sea, governments agreed to establish a zone no more than 200 nautical miles wide within which a coastal country has sole rights to natural resources. Known as an exclusive economic zone (EEZ), this area includes the most productive fishing grounds in the oceans. Outside the EEZ, however, freedom of the seas still largely stands.

Overfishing

Overfishing is the state created when fish catch exceeds the maximum sustainable yield (the amount of fish that can be harvested every year without depleting the natural breeding stock). When harvest exceeds recruitment (the ability of a fishery to reproduce and replace animals lost to the fishery), both the fish population and the fish catch decline, causing both ecological and economic harm. Although fishing directly affects the abundance of adult and juvenile fish, the growth and survival of fish in their early life stages depends on the presence of necessary ocean, coastal, estuarine, and river habitats. Lack of abundant, high-quality habitat can be as devastating to fisheries as overfishing.

According to the National Fisheries Institute (the U.S. trade association for commercial fishermen and seafood suppliers) Web site (http://www.nfi.org/), more than 170,000 people worked in the United States as commercial fishermen in 2005. These fishermen operate many different types of vessels, ranging in size from small one-person boats to large purse seiners and trawlers. The vast majority of these vessels are independently owned and family operated, and harvest more than 300 species of seafood from U.S. waters. Seventy percent of the harvest is caught with purse seine and trawl nets. A purse seine is a net that is deployed with floats and traps the fish in a purse-like bag when pulled from the sea. A trawl net is a large conical net that is weighted and dragged along the sea bottom to collect fish and other marine life.

Fisheries of the United States 2003 reported that per capita consumption of fishery products in 2003 was 16.3 pounds, an all-time high. U.S. commercial fish landings—the volume of fish brought to the dock by commercial fisheries—at ports in the fifty states amounted to 9.5 billion pounds and was valued at $3.3 billion in 2003.

NOAA described the general welfare of the U.S. living marine and estuarine resources as "guarded with vigilance needed." The decline in Northeast groundfish, the uncertain state of some West Coast salmon runs, and the reduced populations of sharks and other marine species are examples of areas that need special attention. Overfishing and habitat loss are causing many fisheries to fall below the levels required to produce long-term potential yield. The challenge is to maintain the long-term viability of the natural system, while at the same time addressing the social and economic needs of the fisheries.

In the United States, the EEZ is the responsibility of the federal government and regional fishery management councils. Nearshore fisheries, defined as those within zero to three miles of the coastline, are the responsibility of coastal states and interstate marine fishery commissions.

Shellfish Harvesting

More than 33,000 square miles (an area about the size of Maine) of marine and estuarine water in the contiguous United States are classified as shellfish harvest waters under a program that is jointly administered by the coastal states and the National Shellfish Sanitation Program (NSSP). In this program shellfish are narrowly defined as "bivalves," that is, mollusks having two valves. Common bivalves are oysters, clams, and mussels. Once a common staple in the diet of people living near coastal waters, most bivalves are considered a delicacy today. The national commercial harvest of these mollusks is valued at more than $200 million when it is first put ashore.

Since the time of the Romans, bivalves have been identified as potential transmitters of infectious disease. The infectious and sometimes dangerous diseases that have been transmitted by bivalves range from typhoid and cholera to minor intestinal disorders. The disease agents may originate in the sewage of humans or other warm-blooded animals or may be naturally occurring in the environment. It is the unique biology of bivalves and the way in which people eat them that contribute to our vulnerability to disease.

Shellfish are filter feeders that tend to stay in one place and pump large amounts of water through their bodies. If pathogens (disease-causing bacteria and viruses) are present in the water, the bivalves may concentrate the pathogens in their tissues to levels that can cause disease in humans who eat the bivalves raw. The bivalves are not harmed by the microbes, and if exposed to clean water, will cleanse themselves. Crabs, shrimp, and other crustaceans do not concentrate the pathogens.

To protect the public that eats bivalves raw and to ensure a safe harvest, the coastal states carefully monitor the water and control commercial harvest under the NSSP guidelines. Special emphasis is given to identifying and eliminating the discharge of untreated or poorly treated human and animal sewage in harvest areas. Harvesting is restricted in waters that do not meet NSSP guidelines. States determine if an area is safe for harvesting by monitoring the concentrations of the indicator bacteria, total coliform, and fecal coliform. Indicator bacteria provide evidence of possible fecal contamination from human and domestic animal wastes. These wastes may contain pathogens that can be taken up and concentrated by the bivalves. Figure 6.4 shows the most common sources responsible for the presence of these indicator bacteria that led to shellfish harvest restrictions as reported by three states. The program has been very successful in preventing illness from contaminated bivalves, and outbreaks of illness rarely occur.

The filter feeding of bivalves also makes them vulnerable to the concentration of chemical contaminants that may be harmful to humans. Concentrations of chemicals in bivalves are directly related to the concentrations in the water column and the food that they consume. Because bivalves are low in body fat, they do not tend to bioaccumulate and retain chemicals to the extent that fish do.

NOAA has monitored chemical contaminants in mussels and oysters in its Mussel Watch Program since FIGURE 6.4
Sources associated with shellfish harvesting restrictions, 2000
SOURCE: "Figure 7-3. Sources Associated with Shellfish Harvesting Restrictions," in 2000 National Water Quality Inventory, U.S. Environmental Protection Agency, August 2002 1986. According to the latest report, issued in 2002, while the levels of most chemical contaminants were decreasing, others remained the same. The best news, however, was that none of the chemicals monitored were increasing in concentration.