chapter 23 conservation of · pdf filechapter, you will learn about some of the problems and...

When you have finished this chapter, you should be able to:

LIST important living and nonliving marine resources.

IDENTIFY recent problems in worldwide ocean fisheries.

DESCRIBE different methods of farming aquatic life-forms.

DISCUSS threats to, and protection of, marine animals.

For years we have thought of the ocean as an endless source of nat-ural resources—both living and nonliving. Fish, invertebrates, andalgae are examples of living resources from the sea that are used as asource for food, medicine, fertilizer, and cosmetics for the humanpopulation. Oil, gas, and minerals are nonliving resources that areused for energy and industry.

Advances in technology have made the ocean’s resources moreavailable to people. As the size of the human population increases, the demand for those resources also grows. People will continue tolook to the sea to meet many of their needs. How can we protect theocean and still provide for the intelligent use of its resources? In thischapter, you will learn about some of the problems and progressmade in the use and conservation of marine resources.

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23.1Marine Resources

23.2Farming the Sea

23.3Protecting Marine Animals

Conservation of Resources

MARINE ECOLOGY

2323

23.1 MARINE RESOURCES

Humans depend on materials obtained directly from the environ-ment, called natural resources, to feed themselves and to make theirlives safer and more comfortable. Many of these resources areobtained from the sea. Marine resources include animals, algae, fossilfuels, minerals, and even the water itself. Importantly, most resourcesare not endlessly available. Some items, such as fish and algae, areknown as renewable resources, because they can reproduce and replen-ish their populations. Other items, such as oil and minerals, areknown as nonrenewable resources because they are available only inlimited amounts in nature. People have to wisely manage and safe-guard natural resources to ensure their continued long-term avail-ability. The careful management and protection of natural resourcesand the environment in which they are found is called conservation.

Marine Fisheries

Fish are one of the most important resources in the ocean becausethey are a food source for the human population. The commercialharvesting of fish and shellfish is carried out by the fisheries indus-try. People eat about two-thirds of the fish that are caught and sold;the remaining one-third is used for domestic animal feeds and otherproducts. From the 1950s through the 1990s, the world’s fishingfleets harvested increasingly larger amounts of fish. (See Figure23-1.) Whereas the world’s seafood catch was about 20 million met-ric tons (mmt) in 1950, by the year 2000 it reached nearly 95 mmt.Now, due to decades of intensive overfishing, that amount hasdecreased and the world fish catch appears to be leveling off.

Most fish, about 60 percent, are caught in the North Atlanticand North Pacific waters. Almost the entire catch is made in the ner-itic zone, that is, above the continental shelf. Although there arethousands of species of marine fish, only about 30 species accountfor most of the fish intentionally caught. The most commonlycaught species of seafood (as of 1990) are listed in Table 23-1; catchnumbers are in millions of metric tons.

Japan, Russia, the United States, and China are among the lead-ing fishing nations of the world. Sixty percent of the fish eaten by

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people in the United States is imported from other countries, mostof it from Canada and Japan. On average, a person in America con-sumes only about 6 kg of fish per year, whereas a person in Japan(which has the world’s highest consumption of fish per person) eatsseveral times that each year.

Conservation of Resources 571

200019901980197019601950

90

80

70

60

50

40

30

20

10

0

100

Wor

ld F

ish

Cat

ch (

in m

mt)

TABLE 23-1 WORLD COMMERCIAL CATCH OF MARINE SPECIES

Species Group Catch (mmt)*

Herring, sardines, anchovies 24.6

Cods, hakes, haddocks 12.8

Miscellaneous marine fishes 11.0

Jacks, mullets, sauries 9.2

Mollusks 7.9

Redfish, basses, conger eels 5.9

Crustaceans 4.5

Tunas, bonitos, billfishes 4.0

Mackerel, snooks, cutlass fishes 3.8

Flounders, halibuts, soles 2.0

*Source: FAO Yearbook of Fisheries Statistics and U.S. Department of Commerce, Fisheries, 1990.

Figure 23-1 The worldcommercial fish catch overa period of 50 years.

Methods of Catching Fish

Fish are caught commercially by using either hooks and lines or avariety of nets, as shown in Figure 23-2. Long fishing lines withmany hooks attached are used to catch widely dispersed surface andbottom fish in a method called long-lining. Some species of tunaare caught in this manner. Nets catch many more fish at a time, andare usually set on schools of fish. One type of net, the trawling net,is released from the rear, or stern, of the ship and is pulled throughthe midwater region to catch squid and schooling fish such as tuna,herring, mackerel, and anchovies. The net can also be dragged alongthe seafloor to catch bottom-dwelling fish such as sole, cod, halibut,and haddock.

The pelagic fish, such as tuna, mackerel, herring, and anchovies,which swim in large schools closer to the ocean surface, can also becaught in other types of nets. The purse seine net is used to sur-round and trap large schools of fish. The gill net intercepts a schoolof swimming fish, which get caught by their gills in the net’s mesh.Both methods of fishing also catch unintended victims. Purse seinenets that are set on schools of tuna sometimes accidentally trap anddrown dolphins (which must breathe air at the surface) that swimalong with the tuna. Modifications have been made to some nets,enabling the dolphins to escape. Gill nets that are set for fish such assalmon entangle and drown thousands of marine mammals andhundreds of thousands of seabirds each year. More than 20 differentseabird species are affected. Seabirds are also caught and drownedby long-line fishing hooks. Scientists have already noticed popula-tion declines in several species of seabirds and marine mammals.

There is intensive and widespread use of large fishing nets bycommercial fishing fleets (by the “factory ships” that can catch andprocess huge amounts of fish). This has contributed to a decline inthe world catch of some of the more important species of food fish.In response to overfishing by foreign vessels in our offshore waters,the U.S. Congress in 1976 passed the Magnuson Act, which forbidsforeign fleets from fishing within 333 km of our coast.

Federal protection of our coastal waters from foreign fishingfleets stimulated the growth of the American fishing industry. Biggerand better-equipped fishing boats brought in record numbers offish, many of them species that previously had been caught by othernations. However, populations of some food fish later declined. In

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Hooks and long-line fishing

Trawling nets

Purse seine net

Gill nets

Midwater

Bottom

Figure 23-2 The fourcommercial methods ofcatching fish.

recent years, there has been a decline in the U.S. catch of severalbottom-dwelling species, particularly cod, haddock, and flounder.Overfishing by the American fishing industry replaced overfishingby foreign fleets. There were too many boats, with high technology,catching too many fish, too fast. The Magnuson Act did not pre-vent overfishing. As a result, approximately 70 species of importantfood fish have been seriously overfished.

Limits on Commercial Fishing

Like all living things, fish need time to increase their population, orstock, particularly after heavy overfishing. In recent years, the fed-eral government has initiated some important conservation mea-sures to increase the stock of commercially valuable food fish. Someof these measures include limiting the size of the salmon catch onthe West Coast; declaring the Cape Cod fishing grounds off-limitsfor cod, haddock, and flounder; and setting quotas and designatingno-fishing zones to protect the North Atlantic swordfish. When fishare left alone, their populations can recover, although it may takeyears. Indeed, this has been the case with the swordfish—after 10years of conservation measures, their numbers are increasing.

An important consideration in developing guidelines for theconservation of a species is determining a reasonable harvest sizethat would not deplete its population. The largest number of fishthat can be taken from a population without threatening its futuresize (and harvest) is called its maximum sustainable yield. Main-taining a maximum sustainable yield for commercially valuable fishspecies requires regulation and cooperation between the fishingindustry and the federal government. At present, three-fourths ofthe ocean fish that are caught are being fished at or above their sus-tainable yields; one-third of these species are decreasing in stock.

In addition to the problem of commercial overfishing of pre-ferred food fish species, there is the incredible waste of fish that areincidentally caught in huge nets. Drift nets, in particular, catch tonsof unwanted fish. These so-called trash or by-catch fish, which arenot considered commercially valuable or large enough to keep, aresimply discarded. In a recent year, approximately 30 mmt of marineby-catch—which could have been used to feed people—werethrown, dead and dying, back into the ocean. Populations of these

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CONSERVATIONRough Times for the Orange Roughy

1. Why are the stocks of well-known, popular food fish in decline?

2. Explain why fishing boats are working the waters farther offshore.

3. Why are scientists concerned about deep-sea fish like the orange roughy?

QUESTIONS


In the near future, you might be having rattailfor dinner instead of flounder, or sablefish inplace of haddock. These are only some of thecreatures from the deep that are finding theirway to the dinner table. Stocks of the well-known food fish, such as flounder, cod, andhaddock, are declining rapidly worldwide as aresult of overfishing. The total world catch offish peaked by the year 2000 and has beendeclining ever since.

Fishing boats have been returning withempty nets from their familiar fishing grounds inthe waters above the continental shelf. As aresult, they are foraging farther offshore, intothe deeper waters of the continental slope.Aided by the use of larger, stronger nets andfaster ships, the haul of fish from the deep hasincreased greatly in recent years. The NorthAtlantic harvest of rattails, a big-eyed fish with along tail, has reached the huge quantity ofabout 100,000 tons per year.

Fisheries experts claim, however, that deep-ocean fishing will not be sustainable. For exam-ple, the sablefish, which lives at a depth of 1.5km, matures and reproduces very slowly; over-fishing would limit its ability to replenish itsnumbers. Recently, thousands of tons of orangeroughy, which feed on shrimp and squid, werebeing caught each year in the deep waters offNew Zealand. As a result, this new fishery hasalready collapsed. Stocks of these deep-seafishes have been exploited to satisfy the public’s

demand for fish. Scientists say their rapiddecline can upset marine food chains becausethe fish are an important food source for otherocean animals. (See photograph above.)

In the United States, the investigation ofdeep-sea fisheries is encouraged by NOAA’sNational Marine Fisheries Service, which sup-ports exploration of the deep ocean with mil-lions of dollars in grants. One of the goals is toallow the depleted stocks of fish species, such ascod, haddock, and flounder, to make a come-back. The federal government is working closelywith commercial fisheries to strike a balancebetween exploitation and conservation.

unwanted fish are now in decline, just like the populations of pre-ferred fishes. Fortunately, there are plans by several countries tophase out the use of drift nets. But what is really needed is bettermanagement of commercial fisheries.

Fossil Fuels

Your home or apartment may be heated with oil or gas. Older build-ings use coal. Oil, gas, and coal are called fossil fuels because theycome from the remains of long-dead plants and animals. Fossil fuelsare formed in Earth’s crust, both on land and in the ocean floor.Over time, great quantities of microscopic plankton that float nearthe ocean surface die and settle to the bottom, forming (along withother mineral sediments) layers hundreds of meters thick. The pres-sure of overlying layers of sediment fuses the bottom layers into atype of rock called sedimentary rock, which contains organic chemi-cals from the dead organisms. The chemicals in the rock, calledhydrocarbons, consist mostly of fat compounds that come from thecells of the decayed organisms.

High temperatures and pressures from Earth’s interior heat therocks to more than 150°C, causing the solid hydrocarbons in therock to change to oil (much like the solid fat in bacon changes to oilwhen it is heated on the stove). The oil that forms in sedimentaryrock layers is called petroleum. Petroleum that is heated to highertemperatures produces gases such as methane and propane. The oiland gas under pressure seep through porous layers in the sedimen-tary rock until they encounter a nonporous layer called a dome,where they accumulate. When oil companies drill for oil, they hopeto tap into petroleum-rich domes. Today, almost 70 percent ofpetroleum comes from land drilling and about 30 percent comesfrom the seafloor. However, these figures are likely to change as oilwells on land dry up and new deposits are discovered at sea.

Getting Oil from the Ocean

How are oil and gas recovered from beneath the ocean floor? Oilcompanies drill for oil and gas offshore, usually at the edge of thecontinental shelf. (Most U.S. oil drilling occurs in the Gulf of Mex-

576 Marine Ecology

ico; some also occurs off the southern coasts of Alaska and Califor-nia.) A large platform, about the size of a city block, is needed tosupport the drilling rig and to provide living quarters for workers.(See Figure 23-3.) The rig contains a hollow drill pipe with a drill bitthat can bore through solid rock. The drill pipe operates insideanother pipe called the riser. During drilling, mud is pumped downinside the drill pipe to produce a counter-pressure that prevents oilfrom gushing up through the pipe. As the drill bit cuts through therock, pieces of rock are carried by the mud back up to the platformthrough the space between the drill pipe and the riser. If oil is pre-sent, it shows up in the returning chunks of sediment. When theoil amounts to more than 200 barrels a day, the drill site is consid-ered economically worthwhile. A pipeline is then attached to therig and the liquid petroleum is transported to storage tanks on land.

Drilling for oil is not without its problems. Sometimes the oiland gas accumulate in the rock layers under such great pressure thatwhen a drill breaks through, the whole pipe assembly is forcefullyejected in what is called a blowout. One of the biggest blowoutsoccurred off the coast of Santa Barbara, California, in 1969, spillingmillions of liters of oil into the sea. Careful monitoring is requiredduring the drilling operation, so that adjustments can be madewhen a high-pressure area is encountered.


Figure 23-3 Drilling for oilbeneath the ocean floor.

How is oil located beneath the seafloor? Sound or seismic tech-nology is used to locate oil fields in the seabed. Oil companiesbounce sound waves off the seafloor from ships and analyze thereturning echoes to determine if there are oil deposits under theseafloor. Once they have seismic data that indicate a possible oilfield, the oil company begins drilling. However, at best only one inten drilling operations is successful. Drilling for oil is a gamble anda very costly one at that.

Recently, a new technology was developed to increase thechances of finding oil under the seafloor. An oil-hunting ship towsseveral rows of submerged air guns that generate sound signalsaimed at the seafloor. The sound waves penetrate the seafloor andbounce off rock formations located kilometers below. The returningwaves are picked up by hydrophones in fiber-optic cables that trailbehind the ship. Millions of bits of seismic data are beamed up to asatellite orbiting Earth. The satellite then beams the data down tosupercomputer centers, which translate the data into geologicalmaps that reveal potential oil fields. This information is sent back tothe ship, directing it to focus on particular sites on the seafloor thatare most likely to have oil deposits. The use of the satellite calledACTS (Advanced Communication Technology Satellite) shortensthe time it takes for oil-hunting ships to locate promising oil fieldsbeneath the seafloor.

Minerals

Another natural resource is minerals, which are solid, inorganicsubstances that are formed in Earth’s crust. We normally think ofminerals as coming from the land. Yet the ocean also contains anabundance of minerals dissolved in the water or found in rocks.However, these elements are widely dispersed and very difficult toextract with present technology.

The most common mineral extracted from the ocean is salt.Some salt comes from shallow ponds or marshes located along trop-ical coasts. The ponds are flooded with seawater, either naturally orartificially. When the sun evaporates the water, salt remains behind.The salt can then be mined for commercial use. Millions of yearsago, a shallow sea covered much of North America. The emergence

578 Marine Ecology

of the land and the evaporation of seawater left behind hugedeposits of salt, thousands of meters deep in some places. Some salt-producing states are New York, Louisiana, Texas, Michigan, andOhio.

One of the most valuable types of mineral deposits, called man-ganese nodules, lies on the ocean floor. (See Figure 23-4.) Thepotato-shaped nodules are usually more than 2000 meters deep,which makes them difficult to mine. They occur in various deep-sealocations around the world, although most are found in the PacificOcean around the equator. Manganese nodules have been scoopedup, at great expense, and brought to the surface to be analyzed. Thenodules contain not only manganese but also some iron, nickel,copper, and cobalt—all of which are important minerals for indus-try. When cut in two, the nodules show a ringlike pattern. Scien-tists are not sure how the nodules form, but they think that theygrow around fossils that settled on the ocean floor. Several industri-alized nations, including the United States, have already staked outexploratory claims in the Pacific Ocean.

In December 1982, at an international conference sponsored bythe United Nations in Jamaica, West Indies, 119 nations gatheredto sign the Law of the Sea treaty. This “constitution of the oceans”stipulated that nations with coastlines have sovereign rights overthe ocean and seafloor out to 333 km. The ocean beyond that is“the common heritage of mankind.” Any mining done beyond the


Figure 23-4 Manganesenodules, shown here on theseafloor, contain importantminerals.

333-km limit is managed by the United Nations to ensure thatexploitation does not occur and that mineral wealth is shared withthe poorer nations. The Law of the Sea treaty also urged all nationsto prevent and control marine pollution by “the best practicalmeans at their disposal.”

Freshwater and Desalination

More than 70 percent of Earth is covered by water, yet most of theworld has a limited amount of available freshwater. This is becauseabout 97 percent of all water is salt water. Most of the freshwater isfrozen at the poles. In fact, of the 3 percent that is freshwater, abouttwo-thirds is frozen. Thus, only 1 percent of all water on Earth isavailable as freshwater in a liquid state. Deserts, in particular, arecharacterized by long periods with little or no rainfall. In dry areassuch as North Africa, droughts often cause massive crop failures.Without food or water, many people and animals die of thirst andstarvation.

How can we increase the supply of freshwater to meet humanneeds? The greatest source of water on Earth is the ocean. Fresh-water can be produced from ocean water by removing the salt, in aprocess called desalination. In one method of desalination, calleda solar still, light passes through a transparent plastic or glass roofto warm the seawater inside. The seawater evaporates, leaving thesalt behind. The freshwater condenses on the underside of the roofand trickles down along the sides into a gutter where it is collectedand pumped through a pipe to a reservoir. (See Figure 23-5.) Onlyabout 1 liter of freshwater is produced per day from 1 square meterof water surface. Solar stills are built along coasts that receive ade-quate warmth and sunshine. They are used in regions of limitedfreshwater, such as Israel, Peru, and West Africa. More solar stillsare needed to meet increasing demands for freshwater around theworld.

A more recent innovation in desalination technology is reverseosmosis. In this process, which requires energy to work, water mol-ecules in a container of seawater are forced through a semi-perme-able membrane into a freshwater tank. Florida has more than 100desalination plants, and almost all of them use reverse osmosis.

580 Marine Ecology

The nation’s largest reverse osmosis desalination plant is located in Santa Barbara, California. It produces 26 million liters of fresh-water per day.

23.1 SECTION REVIEW

1. Why has the catch of important food fish declined dramaticallyin recent years?

2. Explain why fish can be a renewable natural resource, whereasfossil fuels are not.

3. Why are nations interested in harvesting manganese nodules?Why is it a difficult business venture?

23.2 FARMING THE SEA

Humans have always been hunters and gatherers, foraging on landand fishing at sea to provide for individual and collective needs. Ashuman society and technology progressed, people turned to raisinganimals and plants on land; that is, they started farming. Today,


Watervapor

Sun

Seawater

Seawater

Sea water

Seafloor

Freshwatercollector

Droplets of freshwater

Fresh-water

pipelineto shore

Freshwater

Figure 23-5 A solar still isused for the desalinationof ocean water.

more food is needed to feed the ever-increasing human population.Since overfishing has become a serious problem, people are lookingat alternative ways to obtain food from the sea. One such method isto “farm” the sea. The process of farming organisms from the sea iscalled mariculture. The farming of aquatic organisms, in general,is called aquaculture.

Mariculture of Invertebrates

Among the most convenient marine animals to farm are the mol-lusks, such as mussels and oysters. These sedentary shellfish natu-rally grow attached to substrates in large clusters in shallow water.Mariculture started in Japan with the raising of oysters along theshore. A female oyster produces more than 100 million eggs at asingle spawning. After fertilization, the eggs develop into swimminglarvae called veligers. The veligers attach to hard surfaces anddevelop into tiny oysters called spat, which are placed like seeds ona variety of substrates. After about 2 years of growth, the oystersmay be transferred to rafts in oyster ponds or placed on mud flatsfor fattening. In another 5 years, they are ready to be harvested.

Oysters are cultivated in vast numbers in the United States,France, and Japan and are the most profitable mollusks that arefarmed. How can oyster cultivation be so profitable? Oysters, whichfeed on phytoplankton, are sedentary and use their energy mostlyfor growth and reproduction. In addition, oysters have a continuousfood supply, as they filter-feed on plankton that is delivered byocean currents.

Techniques similar to those used in raising mussels are used inoyster mariculture. Mussel mariculture is particularly successful inSpain, France, Japan, and the Philippines. Mussels are also farmed inthe United States. The larvae of mussels attach and grow on ropesthat are placed near mussel beds in shallow areas. The ropes eitherdangle from wooden rafts coated with fiberglass or are wrappedaround poles stuck in the mud flats. After the mussels grow forabout a year, they are harvested. One acre of floating rafts can pro-duce more than 500 kg of mussel meat a year.

It was discovered recently that mussels can be harvested fromthe posts of oil platforms. At least one company in California hasmade a profitable business out of harvesting mussels from oil plat-

582 Marine Ecology

forms in the waters off Santa Barbara. Oil companies have cooper-ated in this venture, since the mussels damage the platforms andhave to be scraped off anyway. In the United States, mollusk farm-ing is still in its early stages. But if the demand for mollusks as afood item increases, many coastal areas can be used to raise themsuccessfully—provided the water quality is acceptable.

The crustaceans—lobsters, crabs, and shrimp—are more difficultto farm because, when raised together, these arthropods tend tofight. You may have seen live lobsters with their claws taped shutin a restaurant tank. Normally, lobsters must be kept in separate,large compartments, which makes them more expensive to raise.Mariculturists discovered that lobsters raised in warm water growfaster than those that grow in colder water in the wild. Several lob-ster farms have started to use the warm water that is dischargedfrom power plants. The mariculture of brackish and marine shrimpspecies has been more successful. These crustaceans grow fast andcan be raised in ponds. More research is needed to develop tech-niques that can produce crustaceans commercially.

Fish Aquaculture

Fish aquaculture has had a long and successful history. Fish farm-ing started in China more than 3000 years ago, with the rearing of alarge edible fish called carp, a relative of the goldfish. Today, a 1-acrepond can produce 12,700 kg of carp meat a year. This high yield is aresult of a method called polyculture, in which different species ofcarp—each consuming a different kind of food—are raised togetherin a pond. The grass carp feeds on rooted plants along the edge ofthe pond. The wastes produced by this fish cause plankton blooms.Some of the plankton remains settle to the bottom and accumulateas sediments that are fed on by invertebrates. The mud carp feeds onthe invertebrates. A third species of carp feeds on plankton that livesnear the water surface. (See Figure 23-6 on page 584.) Each species issuccessful because it eats a different type of food, thereby avoidingcompetition. As a result, the pond promotes maximum growth anda high rate of reproduction. Development of catfish farms in theUnited States is another example of fish aquaculture.

With wild stocks of saltwater fish declining each year, there isan increasing demand for fish mariculture, the farming of saltwater


fishes. The most widely cultured saltwater fish is the milkfish(Chanos chanos). The milkfish is an important food item in Asia.Milkfish spawn in coastal waters. After fertilization, the eggs developinto little fish called fry. The fry are caught in nets and transferred tosmall, shallow saltwater ponds along the coast. In one month, themilkfish grow to 7 cm in length and are transferred to larger salt-water ponds for fattening. After a year, the milkfish weigh about 1kg each. An acre of milkfish yields over 1 metric ton per year.

Freshwater fish aquaculture is generally more successful thanfish mariculture, because conditions for maximum yield—from fer-tilization to fattening—can be controlled more easily in ponds.However, the Japanese have been able to cultivate a popular saltwa-ter fish, the red sea bream (Chysophrys major), from fertilization tomaturity in closed saltwater ponds. Thousands of young adult seabreams have been released into the ocean to increase the wild stockduring a time of short supply.

Salmon are also farmed in the United States, Ireland, Norway,and Canada. In some cases, young salmon are reared in captivityand then released into the ocean, with the hope that they willreturn to spawn in the river where they were caught. However, thereturns have been very low. In salmon ranching, the fish are raisedin suspended cages, or pens, where they are fed well to ensure fast

584 Marine Ecology

Aquatic vegetation

Aquatic invertebrates

Plankton

Figure 23-6 Polyculture ofthree different carp speciesin a pond.

growth. This technique has been very successful. One drawback,however, is that the cages can become fouled with other organisms,and the sediments below the cages can become fouled with wasteproducts from the salmon. In Norway, in 1990, salmon ranchingproduction reached 100,00 metric tons per year. With such results,fish mariculture may have a very promising future. (See Figure 23-7.)

Seaweed Mariculture

While animal mariculture is a relatively new industry, the farmingof seaweeds, called seaweed mariculture, is already big business. Whoeats seaweed, you may ask? We all do, or at least we consume prod-ucts that come from seaweed. Many consumer goods are made withseaweed ingredients. The chemical called carrageenan, extractedfrom Irish moss seaweed, is used to make toothpaste, ice cream, andother food items. Carrageenan prevents the ingredients in theseproducts from separating.


Figure 23-7 Hybridstriped bass being farmedin California.

Another chemical, called algin, is extracted from the brown algakelp. Algin is used as a thickener and stabilizer in many foods, suchas cheese and ice cream. Kelp is harvested off the California coastfrom large barges that have rotating blades, which cut off the tops ofkelp just below the ocean surface. The same area can be continuallyharvested, since the kelp grows very rapidly.

Seaweeds have been farmed in China and Japan for hundredsof years. The most popular edible seaweeds are the green alga calledsea lettuce, traditionally used by Hawaiians in salads, and the pro-tein-rich red alga Porphyra, or nori, used to wrap boiled rice in Japan-ese cooking. These algae are grown and harvested in shallow coastalwaters. Together with the other seaweeds, they constitute a one-billion-dollar food industry in Asia. (Refer to Chapter 5 for moreinformation on algae and seaweed products.)

Seaweed harvesting is a growing industry in the United States.The demand for edible seaweed is increasing each year. Health foodstores carry a variety of seaweed food items, and cookbooks nowinclude seaweeds in their recipes. However, the success of seaweedmariculture may be limited in the future due to poor water qualityin most coastal areas. Seaweeds cannot be raised or harvested in pol-luted water—another good reason to clean up coastal waters.

23.2 SECTION REVIEW

1. Describe how mollusks, such as oysters, can be successfullyfarmed.

2. Describe mariculture of the milkfish. How is it different fromfreshwater carp aquaculture?

3. Why is seaweed mariculture an important food industry?

23.3 PROTECTING MARINE ANIMALS

The great auk (Pinguinus impennis) was last seen alive in 1844. Thismarine bird stood about 60 cm tall and looked like it was part duckand part penguin. (See Figure 23-8.) Although it was once abundantalong the North Atlantic coast, the great auk will not be seen againbecause it is extinct.

586 Marine Ecology

When a species becomes extinct, it no longer exists anywherein the world. How did the great auk become extinct? Great auksinhabited the shallow coastal waters near Newfoundland, Canada.Although fast-swimming while in pursuit of fish, on land theseseabirds were flightless, awkward, and easy prey for hungry sailors.As a result, by the mid-1850s the great auks were exterminated—hunted into extinction.

Since the 1600s, when European settlers first came to America,more than 500 animal species have become extinct. More thanthree times that many are now in danger of extinction in America.Some of these species are marine animals. Table 23-2 lists a fewseabird and marine mammal species that have become extinct as aresult of human activities within the past 250 years.


Figure 23-8 The greatauk, a large seabird, washunted to extinction.

TABLE 23-2 RECENTLY EXTINCT SEABIRDS AND MARINE MAMMALS

Species Date Last Seen Habitat

Steller’s sea cow 1768 Aleutian Islands

Great auk 1844 No. Atlantic Coast

Labrador duck 1875 No. Atlantic Coast

Sea mink 1880 Coast of Maine

Caribbean monk seal 1962 Caribbean Sea

Dusky seaside sparrow 1987 Atlantic Coast

Unfortunately, the extinction of animal species continues. Anexample of a marine animal found in American waters that isthreatened with extinction is the Florida (or West Indian) manatee.The manatee inhabits the rivers and waterways along Florida’s Gulfand Atlantic coasts (and the Caribbean Sea). During the winter,these mammals move into warm coastal rivers and graze on vegeta-tion. As summer approaches and the ocean warms, the manateesleave the protection of the inland rivers and migrate along thecoast. Many manatees get struck by power boats and are injured orkilled by the boat propellers. It is thought that some also die frompoisoning by red tide microorganisms. The rapid developmentalong Florida’s coast also has contributed to a decline in the mana-tee population, mainly due to a loss of habitat. (See Chapter 14 formore information on the manatee.)

Protective Legislation and Sanctuaries

In response to a growing awareness and concern about the plightof species, such as the manatee, that are threatened with extinction,the U.S. Congress passed the Wildlife Preservation Act in 1969, theMarine Mammal Protection Act in 1972, and the EndangeredSpecies Act in 1973. The 1972 act specifically protects such animalsas whales, dolphins, seals, manatees, and sea otters. The populationsof many of these animals had been decimated by human activities,such as whaling, fishing, and hunting for food and furs. Theseindustries had threatened the survival of many species. (See Chapter14.) The 1973 act is responsible for listing those species that are indanger of becoming extinct, so that actions can be taken to protectthem. More than 100 species of marine fish have been listed. Speciesthat are in more immediate risk of extinction are listed as endan-gered species; those that are in less immediate risk are listed asthreatened species. Table 23-3 provides a partial list of threatenedand endangered marine animals.

The Endangered Species Act forbids the import into the UnitedStates of any animal, or product from any animal, which is on thelist. It further prohibits the interstate trafficking of endangeredspecies and products obtained illegally in their country of origin.Thanks to the passage and enforcement of such laws, the popula-

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tions of several species that once seemed doomed have now recov-ered and bounced back from the edge of extinction.

One of the success stories in marine mammal conservation isthat of the California gray whale. The gray whale migrates along thePacific Coast, between its feeding grounds in the Arctic and breed-ing grounds in the Gulf of California. By 1910, the whaling industryhad reduced the population of gray whales to approximately 5000animals. The whale was declared an endangered species and pro-tected from hunting. As a result, its population has returned to amuch healthier number of approximately 22,000. The federal gov-ernment may even remove the gray whale from the endangeredspecies list. However, not all whale species that were formerlyhunted have recovered as well. The blue whale, for example, washunted so heavily that it may not be able to sustain its population,even though it is now protected.

In 1978, the Florida Manatee Sanctuary Act was established tostop the decline of the manatee population. One of the provisions


California whiteabalone

Florida sea slug

Atlantic bluefintuna

Short-nosedsturgeon

Round whitefish

Chinook salmon

Totoaba(seatrout)

Caribbeangroupers

Great whiteshark

Seahorses(>30 species)

No. Atlanticswordfish

Atlantic cod

Haddock

Coelacanth

Sea turtles:loggerhead,green,hawksbill,leatherback,Kemp’s ridley,olive ridley

Saltwatercrocodile(American)

Osprey

Bald eagle

Piping plover

Roseate tern

Common tern

California leasttern

Short-tailedalbatross

Wanderingalbatross

Eskimo curlew

Whales:bowhead,sperm, gray,finback, right,humpback,sei, blue

Gulf of Californiaharbor por-poise

California seaotter

Seals:Mediter-ranean monk,Hawaiianmonk,Guadalupefur seal

Steller’s sea lion

Manatee

TABLE 23-3 SOME THREATENED AND ENDANGERED MARINE ANIMALS

Mollusks Fish Reptiles Birds Mammals

of the act was the creation of sanctuaries that would eliminate orreduce human intrusion. (See Figure 23-9.) A speed limit of 8 kmper hour was set for boating in sanctuary areas. In addition, effortshave been undertaken to increase the manatee population in Floridathrough captive breeding and release programs. Manatee tourismprograms and marine reserves in Central America and theCaribbean region also have been developed to protect theseanimals.

Other endangered marine species would probably have becomeextinct if concerned citizens, local governments, and environmentalgroups had not taken action. Today, citizens are showing concernfor the plight of endangered and threatened species. The U.S. gov-ernment has responded to these concerns by establishing moresanctuaries. One of NOAA’s initiatives is the National Marine Sanc-tuary Program, which protects unique and biologically rich coastalenvironments. The marine sanctuaries are protected areas in whichno commercial activities are permitted. These sanctuaries are animportant conservation measure that provides safe habitats formarine organisms. For example, a marine sanctuary for humpbackwhales in Hawaiian waters protects their breeding and calvinggrounds. See Figure 23-10, which shows 13 designated and threeproposed national marine sanctuaries in U.S. waters.

One of the most significant conservation developments to occur

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Figure 23-9 Sanctuariessuch as this one wereestablished to protectmanatees from humanactivities.

in recent years has been the creation of land trusts and conservan-cies, which operate in every state. These nonprofit organizationswork with landowners to protect key habitats, such as farms andwetlands, and to prevent their being developed for any commercialuse other than agriculture or aquaculture. In 2002, a shellfish com-pany donated 4455 hectares (underwater) in the Great South Bayoff Long Island, New York, to the Nature Conservancy, a nonprofitorganization dedicated to preserving natural habitats. This two-mil-lion-dollar gift will be used by the Conservancy to develop maricul-ture of mollusks such as clams and scallops.

The struggle to preserve and protect the marine environmentcontinues. We now live in a single “global village” in which theoceans are important highways that connect us with one another. Ifone part of the world is exploited or polluted, other parts will beaffected. More laws may be necessary to prevent the degradation ofour marine environment. Respect for the environment and cooper-ation with other nations will help us achieve the goal of living inharmony with our marine world.


DESIGNATED SITESPROPOSED SITES

Flower Garden BanksFagatele Bay (American Samoa)Florida Keys(Looe Key, Key Largo)

Gray’s Reef

Thunder Bay

Northwest Straits

Olympic Coast

Cordell BankGulf of the Farallones

Monterey Bay

Channel Islands

Hawaiian IslandsHumpback Whale

MonitorNorfolk Canyon

StellwagenBank

Figure 23-10 Designatedand proposed marinesanctuaries in U.S. waters.

23.3 SECTION REVIEW

1. Why has the manatee become an endangered species?

2. What are some efforts that have been made to prevent theextinction of marine animals?

3. What activities threatened the survival of marine mammals?

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Laboratory Investigation 23

PROBLEM: How can we determine the status of the New England fishery?

SKILLS: Analyzing data from a table; constructing a graph.

MATERIALS: Graph paper, pencil, ruler.

PROCEDURE

1. Examine the data in Table 23-4, which show the average fish catch per trawl(in kilograms) in New England waters for select years from 1963 to 1993.

2. Use the information in the table to construct a line graph on your piece ofgraph paper. (You may also want to construct a bar graph for further com-parison.)

3. Mark an appropriate scale for the horizontal and vertical axes based on datain the table. Plot the data on the graph (you should have seven points.) Sur-round each point with a small circle and draw lines connecting the points.

Analyzing Fishery Data


TABLE 23-4 AVERAGE CATCH PER TRAWL (KG)

Year Fish Catch

1963 63.6

1968 35.0

1973 27.2

1978 36.4

1983 18.1

1988 13.6

1993 14.5

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OBSERVATIONS AND ANALYSES

1. How would you describe the status of the fishing industry in the New Eng-land region in 1963 versus the status in 1993?

2. Congress passed the Magnuson Act in 1976 to prevent foreign fishing boatsfrom working our coastal waters (out to 333 km). Based on the data in thegraph, how effective was this conservation measure in the short term? Howeffective was it in the long term?

3. After 1978, the U.S. fishing fleet grew rapidly. According to the graph, whateffect did a larger and more modernized fishing fleet have on the local fishstocks?

Answer the following questions on a separate sheet of paper.

Vocabulary

The following list contains all the boldface terms in this chapter.

aquaculture, conservation, desalination, endangered species,extinct, fisheries, gill net, long-lining, manganese nodules,mariculture, marine sanctuaries, maximum sustainable yield,minerals, natural resources, polyculture, purse seine net, stock,threatened species, trawling net

Fill In

Use one of the vocabulary terms listed above to complete each sentence.

1. The process of farming organisms from the sea is ____________________.

2. Freshwater can be produced from ocean water by ____________________.

3. The careful management of natural resources is called____________________.

4. Natural, inorganic substances formed in Earth’s crust are____________________.

5. The population of a food resource is referred to as its____________________.

Think and Write

Use the information in this chapter to respond to these items.

6. What are some conservation measures that help reduce over-fishing?

7. Explain how the polyculture technique of fish farming works.

8. Why is the establishment of marine sanctuaries so important?

Chapter 23 Review


Inquiry

Base your answers to questions 9 through 11 on the following graph andon your knowledge of marine science.

9. Based on the data in the graph, which statement is correct?a. Fewer tons of fish were caught in 1980 than in 1950.b. There was a general decrease in the amount of fish caughtbetween 1950 and 1990. c. The greatest amount of fish wascaught in 1990. d. The fish catch in 2000 was more thanfour times greater than in 1950.

10. The most appropriate title for this graph would bea. The increase in fish populations from 1950 to 2000.b. The effect of drift nets on fish populations. c. Trends inworldwide fish catch from 1950 to 2000. d. A comparison of fish species caught from 1950 to 2000.

11. Based on the data in the graph, which statement offers a valid conclusion? a. There are unlimited numbers of fish inthe sea. b. Ocean fish populations have been increasingsince 1950. c. The worldwide fish catch peaked around theyear 2000. d. Ocean fish populations have been decreasingsteadily since 1950.

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200019901980197019601950

90

80

70

60

50

40

30

20

10

0

100

Wor

ld F

ish

Cat

ch (

in m

mt)

Multiple Choice

Choose the response that best completes the sentence or answers thequestion.

Refer to Figure 23-5, on page 581, to answer the following question.

12. Based on the diagram of the solar still, which statement iscorrect? a. The salinity of the seawater in the still decreases.b. Radiant energy is not required for desalination.c. Freshwater is obtained from the condensation of watervapor. d. A transparent roof is usually not needed on a solar still.

13. Marine sanctuaries have been established to protect all thefollowing except a. safe habitats for marine organismsb. breeding and calving grounds of whales c. U.S. fishingrights within 333 km of our coast d. special areas in whichno commercial activities are permitted.

14. Overall, from about 1970 to 1990, the U.S. fishery catcha. steadily increased b. steadily decreased c. increased,then decreased d. remained constant.

15. Bottom-dwelling fish are usually caught by a. a trawling netb. surface long-lining c. a purse seine net d. a gill net.

16. Which is an accurate statement regarding the U.S. fisheryindustry? a. Overfishing led to a decrease in the catch ofsome bottom-dwelling species. b. The larger boats with hightechnology were unable to catch more fish. c. The U.S. isthe leading fishing nation in the world. d. The MagnusonAct increased the foreign catch in U.S. waters.

17. All of these natural resources are extracted from the oceanexcept a. gas b. manganese nodules c. oil d. coal.

18. An example of a renewable natural resource is a. oil b. gasc. flounder d. manganese nodules.

19. When the maximum sustainable yield of a fish species isexceeded, the a. fish stock begins to decline b. size of itsannual harvest increases c. fishing boats catch more fish pertrawl d. fishing boats use nets instead of long lines.

20. An example of an extinct marine species is the a. manateeb. blue whale c. coelacanth d. great auk.


21. An animal that is listed as endangered is a. sure to becomeextinct b. at high risk of becoming extinct c. at noimmediate risk of becoming extinct d. already extinct.

22. All of the following organisms are grown by mariculture excepta. seaweeds b. oysters c. seahorses d. salmon.

23. A method of desalination that is currently in use isa. melting icebergs into freshwater b. using filter paper toseparate freshwater from salt water c. using solar stills toevaporate seawater d. boiling ocean water into freshwater athydrothermal vents.

Research/Activity

■ Prepare a chart that lists several endangered, threatened, and/orextinct marine animals. Include a picture and brief descriptionof each animal and information on its habitat. Prepare a posterto exhibit at a school science fair.

■ Do research on the technology of a fish farm or other aquacul-ture operation. Then, using common materials, construct amodel of the farm. Write a brief description of how a fish farmworks.

598 Marine Ecology

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