Global Harvest

World fisheries landings have increased from 18.5 million metric tons in 1950 to 121 million metric tons in 1996. Presently China cultures or lands 25% of the catch, while 70% of the global catch is landed by only 12 nations. The United States ranks fifth, with landings of 5-6 million tons in recent years. Approximately 85% of the world fisheries harvest is marine species, most of which are from commercial landings of fish and shellfish (i.e., capture fisheries). A large fraction, 25-30%, of landings is used industrially (mostly fed to livestock) rather than being consumed directly by humans. Landings from capture fisheries have been stagnant in the past decade at 80-85 million tons, while marine aquaculture production has increased rapidly from roughly 3 to 7 million tons during the period 1985-1995. Global potential for marine capture fisheries is estimated to be sustainable at approximately 100 million tons. Serious constraints on achieving that level of yield are imposed by overfishing, the incidental kill of non-targeted organisms (bycatch), habitat destruction, and water-quality deterioration. These impacts not only affect potential fishery yields but may also compromise the productive potential of ecosystems.

State of Marine Ecosystems and Productivity

The productivity of the oceans is nearly fully tapped with respect to fishery harvests. Only major and risky changes in global fishing strategies could possibly bring bigger yields. Estuaries, continental shelves, and upwelling ecosystems, where biological productivity is highest, are most heavily exploited. In many marine ecosystems large predator species, which are favored for consumption, have been overfished, and in some cases stocks have collapsed. The collapse of the Newfoundland cod fishery and the near-collapse of the New England cod, haddock, and yellowtail flounder fisheries serve as examples of how overfishing has severely depleted historically important commercial fish stocks. Approximately 20-25% of the world's commercially-desirable fish resources may be overfished and, unless restored, cannot sustain the maximum yields that might otherwise be possible. Global catches have been maintained in part by fishing lower on the food chain, where larger stocks of fast-growing, but economically less valuable, species can sustain higher yields. Some scientists are concerned that such fishing practices disrupt predator-prey relationships upon which the productivity of marine ecosystems depends. Discarded 'bycatch' is estimated to be roughly 25 million tons annually and consists of unwanted species, the young of desirable species, and unintentional catches of birds, mammals, and turtles, including endangered species. Some kinds of fishing affect habitat and may be destructive. Sustainability of fisheries is threatened by overcapitalization and the excess fishing effort it generates. Management institutions often lack the authority, the political will, or the science-based knowledge to effectively manage fisheries .

Management Options

Managing for sustainability initially requires a new resolve to be more conservative in managing traditional single-species fisheries. Fishing mortality must be controlled to protect spawning stocks. However, even this will not be sufficient in the long term. Ecosystem approaches that are protective of habitat, preserve critical predator-prey relationships, reduce or eliminate bycatches, deal effectively with uncertainties in ocean climate, and fully recognize humans as elements of ecosystems, must ultimately be instituted to sustain high ecosystem productivities, high fisheries yields, and healthy marine ecosystems.

New paradigms are evolving with respect to fisheries management. Globally and in the USA, the 'precautionary approach' and 'risk-averse' management are key elements of recent management plans. These approaches recognize the high degree of uncertainty associated with assessing and managing fisheries. Uncertainties arise from: 1) lack of understanding of ocean climate, its trends and variability; 2) poor predictive ability with respect to effects of environment on recruitment variability (replenishment of fish stocks by annual increments in the number of young fish), which often fluctuates tenfold or more annually); 3) errors in stock assessments; 4) uncertain economics and predictors of fishing effort; and 5) unresponsive or ineffective management. Better multispecies and ecosystem models are needed to help understand responses of ecosystems to fishing and to predict future states of marine ecosystems and fish stocks. In addition, many scientists now advocate 'purchasing insurance against uncertainty' in the form of setting aside significant portions of marine ecosystems as reserves within which fisheries are greatly restricted or not permitted. Fortunately, despite many abuses, marine ecosystems and most marine fish stocks appear to be resilient to overfishing if given the opportunity to recover. Most marine fish stocks are not yet overfished; and it is likely, with important exceptions (i.e., estuaries and spawning habitats of anadromous fishes (fish such as salmon, which spawn in fresh waters and live in marine waters), that most marine ecosystems have not yet been irreversibly damaged. There are numerous examples of the capacity of severely depleted fish stocks to recover following episodes of overfishing (i.e., striped bass, herring, and mackerel), supporting the belief that restoration of fisheries can be achieved. Thus, there is an opportunity to redeem past mistakes.

Implications of Contaminants in Coastal Ecosystems

Toxic chemicals have been discharged to coastal areas from a variety of sources for decades. These chemicals include trace metals and organic contaminants, such as polychlorinated biphenyls (PCBs), pesticides, and polycyclic aromatic hydrocarbons (PAHs). Natural biogeochemical processes that influence contaminant persistence and bioavailability control the fate and effects of these contaminants in coastal marine environments. Accumulation of contaminants in biological resources may occur through aqueous, sedimentary or dietary pathways. In the long-term, chemical contaminants of ecological and human health concern, such as metals and organic contaminants, are associated with particulate matter. Transport of particle-bound contaminants within coastal areas coincides with sediment transport processes and, thus, there are numerous examples around the world where sediment deposits in coastal areas reflect waste disposal histories. Transfer of contaminants to marine organisms and humans, and disturbance of ecological systems, are dependent on the availability and persistence of contaminants within sediments, and uptake in bottom-dwelling organisms. There are numerous data sets from US coastal waters on the distribution of chemical contaminants in sediments, fish and shellfish. Spatial gradients of contamination are delineated with nearshore, urban and industrialized areas having higher concentrations of specific contaminants than offshore areas.

Lipophilic (or fat-soluble) organic contaminants, such as PAHs and PCBs, are generally resistant to degradation in the marine environment. Thus, such compounds or their metabolites may accumulate to high levels in animal tissues and interfere with normal metabolic processes that affect growth, development, and reproduction. The bioavailability, bioconcentration, and toxic effects of these contaminants are related to their physical and chemical properties. Differences in contaminant concentrations among species from different habitats may be the result of differences in the availability of sediment-bound contaminants and capacity for biotransformation. The limited capacity of bivalve molluscs (i.e., clams, oysters, etc.) to detoxify organic contaminants, for example, results in the uptake and accumulation of high concentrations of organic contaminants. Samples of bivalve molluscs from contaminated harbors such as Boston Harbor and New Bedford Harbor are highly contaminated with a variety of lipophilic organic contaminants and reflect the sediment contamination.

Ecological concerns of contamination in the marine environment include changes in species distributions and abundance, habitat alterations, and changes in energy flow and biogeochemical cycles. The toxic effects of chemical contaminants on marine organisms are dependent on bioavailability and persistence, the ability of organisms to accumulate and metabolize contaminants, and the interference of contaminants with specific metabolic or ecological processes. Recent studies of the incidence of tumors and other tissue disorders in bottom-dwelling fish and shellfish from contaminated coastal areas have suggested a possible link between levels of lipophilic organic contaminants and the increased incidence of various tissue disorders (i.e., tumors, etc.) . The relationship between tissue disorders and effects on population-level processes in marine animals is not well understood. In addition to a range of tissue damage, sublethal toxic effects of contaminants in marine organisms include impairment of physiological processes that may alter the energy available for growth and reproduction and other effects on reproductive and developmental processes including direct genetic damage.

The transfer of toxic chemicals through marine food chains can result in bioaccumulation in commercial fishery resources and transfer to the human consumer. Contaminants that demonstrate mutagenic, carcinogenic, or teratogenic (disruptive to fetal tissue) potential to the human consumer are of particular concern because they pose direct threats to human health. Chemical contamination of fishery resources, for example, has recently led to fishery closures or fishery advisories in several areas of the U.S. coastline. Examples include the following.

• Striped bass fisheries in the states of New York and Rhode Island were closed in 1986 as a result of PCB contamination.

• The State of California developed health advisories warning the public against frequent consumption of fish caught in southern California waters.

• In 1988 the Department of Public Health in the Commonwealth of Massachusetts issued a state-wide advisory on the consumption of lobster tomalley (hepatopancreas) because of the exceedingly high levels of PCBs and other contaminants.

• In 1994 health officials in Maine issued a health advisory for nursing mothers, pregnant women, and women of childbearing age on the consumption of lobster tomalley because of dioxin levels.

• Health advisories for the consumption of freshwater fish have been issued in Maine because of dioxin contamination (1990) and in Massachusetts because of mercury contamination (1994).

• In Buzzards Bay, MA, approximately 28 square miles are closed to finfishing and shellfishing as a result of PCB contamination.

These recent actions illustrate a growing concern for the impact of chemical contamination on resources in coastal waters. At present there are over 100 Superfund sites in the marine environment where removal or remediation of contaminated sediments will be necessary within the next decade to minimize the potential risks to marine ecosystems and human health. In addition to the ecological concerns of contaminated sediments and their removal, there are also significant economic and political concerns as controversies over risks and costs associated with sediment removal and disposal are balanced with the economic viability of US ports. Recent examples of coastal dredging projects in many US cities illustrate the complexity of the scientific and political concerns of management and disposal of contaminated sediments.

Although general trends in contaminant distributions in urban areas and adjacent waters have been defined, critical information on biological effects of chemical contaminants as they affect human health and ecosystems is lacking. Because contaminated sediments will continue to be a major source of contaminants to ecosystems, even with the improvement in water quality from the reduction of point source contamination, the potential risks to populations of marine biota must be defined.

Biography of Dr. Edward D. Houde

Dr. Edward D. Houde has been affiliated with the Chesapeake Biological Laboratory at the University of Maryland's Center for Environmental Science since 1980, where he is Professor of Fisheries and Estuarine Science. He was formerly on the faculty of the Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, from 1969-1980, and later served as Director of the Biological Oceanography Program at the National Science Foundation from 1983-1985. Dr. Houde's research is focused on fisheries science and management, larval fish ecology, and fisheries oceanography, especially factors that affect production and recruitment of marine fish. His present research concentrates on processes that promote recruitment success in anadromous, marine, and estuarine fish. Results of his research have been published in roughly150 peer-reviewed papers and book chapters. He is the recipient of the Beverton (Fisheries Society of the British Isles) the Sette (American Fisheries Society) Awards for career achievements in fisheries science.

Dr. Houde is a member of the National Research Council's (NRC) Ocean Studies Board and has served on numerous other advisory boards. He is a U.S. representative to the Scientific Committee on Oceanic Research and a member of the International Council for Exploration of the Sea's Committee on Living Resources. He also serves on the Scientific and Statistical Committees of the Mid-Atlantic and Gulf of Mexico Fishery Management Councils. Dr. Houde recently served on the NRC Committee on Ecosystem Management for Sustainable Fisheries and serves on the National Marine Fisheries Service's Ecosystem Principles Advisory Panel. He presently chairs the NRC Committee on Evaluation, Design, and Monitoring of Marine Reserves and Protected Areas.

Biography of Dr. Judith E. McDowell

Dr. Judith E. McDowell is a Senior Scientist in the Biology Department at the Woods Hole Oceanographic Institution (WHOI), with research interests focused on the physiological effects of contaminants on marine animals. She joined the staff of the Biology Department at WHOI as a Postdoctoral Scholar in 1975 and was appointed to the scientific staff in 1976. Her research has led her to her involvement in a number of expeditions throughout the world. One of her current projects is examining the relationship of contaminant exposure and disease processes in bivalve mollusk populations in contaminated estuaries and bays in the United States, Eastern Europe, and several areas within the former Soviet Union. Dr. McDowell has received numerous awards for her research including the New England Monthly "Local Hero" Award in 1985, EPA's Environmental Merit Award in 1987, and a Pew Fellowship in Conservation and the Environment in 1995. She currently holds the positions of Coordinator of the Woods Hole Oceanographic Institution Sea Grant Program and Associate Dean of the MIT-WHOI Joint Program in Oceanography.

Dr. McDowell holds a B.S. degree in Biology from Stonehill College, and M.S. and Ph. D. degrees in Zoology from the University of New Hampshire.