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Ocean Studies Introduction to Oceanography American Meteorological Society Chapter 14 Ocean Stewardship © AMS Case in Point – Oyster production in Chesapeake Bay peaked in the 1880s and then declined. – In the early 20th century, sailing vessels, known as skipjacks were largely replaced by powerboats, and the introduction of powered winches permitted oysters to be harvested from all depths. • Oysters were overfished and oyster reefs were destroyed in the process. • In the early 20th century, commercial oyster production slipped to historically low levels. © AMS Case in Point © AMS Sail powered oyster dredges, known as skipjacks. Shells containing oyster spat raised by the Oyster Recovery Partnership are bagged and placed on pallets to grow before being transplanted to a designated oyster reef elsewhere in the Chesapeake Bay. Case in Point – Native oysters spawned and raised in hatcheries were placed on oyster beds to grow. • Few reached marketable size before dying from disease. • Sterile Asian oysters were introduced; better adapted to living in the muddy Chesapeake Bay waters than were the native oysters – Efforts to restore the oyster fishery in Chesapeake Bay focus on physically rebuilding oyster reefs that stand above the muddy bottom. • Continue but are limited by cost and the scarcity of appropriate materials for oyster attachment © AMS Ocean Stewardship • Driving Question: – How do we balance exploitation of fisheries with efforts to preserve marine species and ecosystems? © AMS Ocean Stewardship • In this chapter, we examine: – Examples of adverse human impacts on marine fisheries and ecosystems – Steps that are being taken to manage fisheries and protect threatened marine species – Ocean stewardship: action taken by society to protect the ocean and its living and nonliving resources for now and the future © AMS Stewardship of Ocean Life – Stewardship of the ocean and its resources involves responsibly managing all resources to benefit present and future generations. – Less than 5% of the ocean bottom has been explored or mapped to the same resolution as the surface of Earth’ neighboring planets, Mars and Venus. – For this reason, we often lack the basic understandings needed to effectively manage and protect marine living resources and their associated ecosystems. © AMS Stewardship of Ocean Life – In the United States, NOAA is the principal government agency charged with stewardship responsibilities for the nation’s marine environment and living resources. – Effective stewardship requires consideration of both the biotic and abiotic components of marine ecosystems to protect living organisms, their habitats, and population sustaining interactions. – One concept that is central to exercising wise stewardship is sustainability. • Requires effectively balancing environmental issues with social and economic concerns, calls for intergenerational equity in managing resources and the environment © AMS Fisheries and Sustainable Exploitation – Fisheries supply about 19% of all the animal protein consumed by humans and the fishing industry employs more than 200 million people, 95% of whom live in developing nations. – Coastal developing nations use traditional methods (artisanal fisheries) and account for about half the world’s marine fish production. – In developed nations, fishers employ technologies intended to increase the fish catch and a large amount of commercial-fish production is processed into fishmeal to feed pets and livestock, and for use in fertilizers. © AMS Fisheries and Sustainable Exploitation • OVERFISHING – Worldwide an estimated one-third of all exploited fish stocks have collapsed; that is, their numbers have declined to less than 10% of their historical maximum population. – Overfishing occurs when a fish species is taken at a rate that exceeds the maximum catch that would allow reproduction to replace the population. • Recruitment overfishing: adult fish are taken in such great numbers that too few survive to replenish the breeding stock • Growth overfishing: fish that are taken too small, before the animals have grown to a size that would produce the maximum yield © AMS Fisheries and Sustainable Exploitation • OVERFISHING – The first known human induced collapse of a marine stock occurred about 3,000 years ago along the Peruvian coast. – In the years since the Industrial Revolution, a variety of technological innovations enabled fishers from developed nations to greatly increase the fish catch. – Governments worldwide spend billions of dollars annually subsidizing their commercial fishing industry. © AMS Fisheries and Sustainable Exploitation • OVERFISHING – Government subsidies, greater fishing efficiency, coupled with the growing demand for fish by the soaring human population drove an increase in total fish catch through the 1950s into the 1980s. – The United Nations Food and Agriculture Organization (FAO) reported that after many decades of steady growth, the total annual wild fish catch began to level off in the late 1980s. – As fishers became more adept at taking fish in larger numbers, stock collapses became more frequent forcing fishery managers to impose quotas on commercially desirable fish, limit fishing time at sea, or close fisheries altogether. © AMS Fisheries and Sustainable Exploitation • OVERFISHING – Overfishing has led to the serial depletion of fish populations as each newly discovered stock is fished out and the fishing fleet moves on to the next stock or fishing area. © AMS Fisheries and Sustainable Exploitation • OVERFISHING – As increasing fishing pressures cause populations of top predators to decline, organisms at progressively lower trophic levels begin to dominate food webs in marine ecosystems. • Initially may be accompanied by an increase in total catch • Greater total catch is short-lived as populations of the competitors of the top predators increase © AMS Fisheries and Sustainable Exploitation • MAXIMUM SUSTAINABLE YIELD – To prevent overfishing of a fish stock, fishery managers typically set catch quotas. • Goal is to adhere to the maximum sustainable yield of the fish stock; that is, limits are set on fish catches so that stocks are maintained at a level that will ensure the long-term viability of the target species • A fishery is sustainable if it can be fished indefinitely at reasonable levels while maintaining the ecosystem (function, structure, and diversity) on which the fishery depends, and the integrity of the habitat essential to the fish species. © AMS Fisheries and Sustainable Exploitation The maximum sustainable yield of fish is based on a model (A) that simulates the growth of the population of a fish species. The maximum population, the carrying capacity, is determined by the availability of resources in the marine habitat. The annual population growth rate (B) peaks at some intermediate population size; this is the maximum sustainable yield. © AMS Fisheries and Sustainable Exploitation • MAXIMUM SUSTAINABLE YIELD – Maximum sustainable yield is based on a model that simulates the population growth of an exploited fish species. – The carrying capacity is the maximum population that can be sustained by the resources of the marine habitat. • In the case of fisheries, the maximum population that would exist in the absence of commercial fishing. © AMS Fisheries and Sustainable Exploitation • ECOLOGICALLY SUSTAINABLE YIELD – Fish species are components of ecosystems in which they interact with other organisms and the physical/chemical environment. • A decline in the population of a particular species of fish may have a ripple effect on the entire ecosystem, altering its biotic composition and reducing its stability. • Argues for a more holistic approach to fisheries management © AMS Fisheries and Sustainable Exploitation • ECOLOGICALLY SUSTAINABLE YIELD – Ecosystem approaches integrate ecological principles, human systems, and goals of sustainability for use in the management decision-making process. – In 1993, the 24th Annual Report of the President’s Council on Environmental Quality (CEQ) recommended that the President issue a directive establishing a national policy to encourage sustainable development through ecosystem management. © AMS Fisheries and Sustainable Exploitation • ECOLOGICALLY SUSTAINABLE YIELD – Protection of fisheries requires a thorough understanding of the entire ecosystem, not just the targeted commercial or recreational fish species. • This understanding is the basis for achieving an ecologically sustainable yield: the yield that a marine ecosystem can sustain without undergoing an undesirable change in state. • New management concepts and associated policies must take into account all the species that interact with the targeted species and the habitats they depend on. © AMS Fisheries and Sustainable Exploitation • BYCATCH – Bycatch: fish and other marine animals that are taken in addition to the target species – Major threat to many endangered species, such as sea turtles, dolphins, and other marine mammals – Discarded, either dead or dying, because they cannot be sold • One-third of the annual commercial fish catch worldwide is discarded for this reason – Bycatch problem might be partially alleviated by changing or rewriting governmental regulations to relax quotas, permitting accidental catches to be landed legally © AMS Fisheries and Sustainable Exploitation • RESTORING FISHERIES – Few marine fisheries have been restored after experiencing severe depletion. – The goal of the ecosystem-based approach to fisheries management is to maintain or re-establish marine ecosystems that are home to fisheries. • Require protection of seafloor habitats and expanding the areas of the world ocean designated as protected areas, called marine reserves, where fishing is prohibited – Reducing the capacity of the global fishing fleet could also help restore fisheries. © AMS Fisheries and Sustainable Exploitation © AMS Map of the Channel Islands National Marine Sanctuary Fisheries and Sustainable Exploitation • HABITAT DESTRUCTION AND RESTORATION – Habitat destruction has also caused depletion or destruction of major fish stocks. • Benthic ecosystems and habitats have been heavily damaged by steam-powered fishing boats dragging heavy steel nets over the ocean bottom to catch bottom-feeding fishes. • Habitat destruction threatens oysters in coastal and estuarine waters. © AMS Fisheries and Sustainable Exploitation A (A) Volunteers help NOAA scientists prepare seagrass shoots for planting. (B) Other volunteers help restore submerged seagrass near Solomons Island in Chesapeake Bay © AMS B Fisheries and Sustainable Exploitation • RECREATIONAL FISHERIES – Involve large numbers of people who catch fish for sport rather than for profit – More than half the fishes caught by recreational fishers are released alive; unfortunately many die due to the stress of “catch and release”. – Most recreational fishers prefer to fish near home; hence, sport fish populations are most heavily fished near major urban areas. – Does not damage fish habitat as much as some commercial fishing practices © AMS Protecting Endangered Marine Species – In 1973, the U.S. Endangered Species Act became law providing for the protection of endangered and threatened species. • Species determined to be in imminent danger of extinction throughout a significant portion of their range are listed as endangered. • Species are listed as threatened if they are likely to become endangered in the foreseeable future. © AMS Protecting Endangered Marine Species • SEA TURTLES – Seven species of sea turtles are recognized worldwide. • All are listed as either endangered or threatened. – Many human activities threaten sea turtle population: • commercial harvesting of adult turtles and the poaching of eggs from nests • development projects along beaches used by turtles to nest • bycatch in commercial fishing nets • collisions with ships • ingestion of plastic litter • marine pollution © AMS Protecting Endangered Marine Species • SEA TURTLES – The population of all sea turtles declined nearly 90% between 1980 and 2000. – There are several ways in which the threats to sea turtles by commercial fishing can be reduced: • Special trap door in fishing nets that trawl the sea floor • Reducing the time a trawl net remains on the bottom • Declare areas with high seasonal populations of turtles off limits to fishing at these times © AMS Protecting Endangered Marine Species • WHALES – Hunting whales began early in human history. – Whalers focused on a single species until its numbers were so reduced that they had to hunt another species. – In 1982, to protect the world’s remaining whale stocks, the International Whaling Commission (IWC) declared a moratorium on commercial whaling to take effect in 1986. – Even after decades of protection, many whale stock populations have still not rebounded to their original numbers. © AMS Protecting Endangered Marine Species • WHALES – Among endangered whales are the North Atlantic right whale, blue, and bowhead whales. Populations of humpback whales have recovered after being listed on the endangered species list © AMS Protecting Endangered Marine Species • WATER BIRDS – Restoration of some water-bird populations is among the few successes resulting from environmental policies and regulations in the late 20th century. – Commercial fishers often killed pelicans by raiding their nests because they were thought to be voracious predators of commercially valuable fish stocks. • After 1940 their numbers were further reduced by the widespread use of DDT and other persistent organic pesticides. • Began recovering after 1972 when the U.S. Environmental Protection Agency banned the manufacture and use of DDT • Removed from the endangered species list by 1985 © AMS Protecting Endangered Marine Species • WATER BIRDS – The history of North American ospreys during the 20th century was similar to that of the brown pelican. – Osprey populations were decimated by the egg thinning caused by DDT accumulation in their tissues. • 1972 ban on DDT greatly aided their recovery © AMS Mariculture – Mariculture (or marine aquaculture), industrial farming of fish and shellfish in the ocean is a growing industry worldwide. • Dominate retail markets for many varieties of fish and shellfish farmed fish • Simplest mariculture operations involve filterfeeding mollusks (i.e., mussels, oysters and clams) • Fish farms can add to water pollution problems. • Salmon farms affect wild salmon and may be responsible for reducing native salmon populations in areas where the farms are located. © AMS Mariculture Cobia at a Puerto Rican offshore mariculture facility. Mariculture refers to the farming of fish and shellfish in the ocean. © AMS Marine Exotic Species – Animals and plants introduced into ecosystems, usually by humans • Some introductions are intentional (new organisms used for mariculture) whereas others are unintentional (transported in ships’ ballast waters). • In most cases the introduced organisms do not survive because they are not well adapted to the physical or chemical conditions of their new environment or they are unable to compete in the new ecosystem. • Sometimes an exotic species finds its new environment to be favorable; lacking competitors or diseases, their population expands rapidly. – Example: Asian carp, a large fast-growing fish imported from China to the southern United States by fish farmers © AMS Marine Exotic Species – New exotic organisms may also result from subtle exchanges of genetic materials. • Tall marsh grass (Phragmites) commonly found in the midAtlantic salt marshes has become a widespread and invasive species that crowds out other types of marine grasses. – Exotic marine organisms can also cause health problems among humans. • In 1993, a new strain of bacteria, native to Bangladesh and India, appeared in Peru’s coastal waters and later spread throughout Central and South America. • Carried by coastal plankton © AMS Conclusions – Overfishing forced imposition of quotas and the closure of some fisheries but not before some species came to the brink of extinction. – Overfishing and its associated problems (e.g., habitat destruction, bycatch) spurred fisheries managers to reassess their management schemes. – Move is to shift from the traditional method of managing fisheries for maximum sustainable yield to a more holistic, ecologically based approach that emphasizes the sustainability of the marine ecosystem that is home to the fishery. © AMS