Chapter 12

Sustaining Aquatic Biodiversity

2006 #4 GRoundfish harvest.pdf

Core Case Study: A Biological Roller Coaster Ride in Lake Victoria

• Lake Victoria has lost their endemic fish species to large introduced predatory fish.

Figure 12-1Figure 12-1

Core Case Study: A Biological Roller Coaster Ride in Lake

Victoria• Reasons for Lake Victoria’s loss of

biodiversity:– Introduction of Nile perch.– Lake experienced algal blooms from

nutrient runoff.– Invasion of water hyacinth has blocked

sunlight and deprived oxygen.– Nile perch is in decline because it has

eaten its own food supply.

AQUATIC BIODIVERSITY• We know fairly little about the biodiversity of

the world’s marine and freshwater systems.– The greatest marine biodiversity occurs in

coral reefs, estuaries and the deep ocean floor.

– Biodiversity is higher near the coast and surface because of habitat and food source variety.

• The world’s marine and freshwater systems provide important ecological and economic services.

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

• Human activities have destroyed, disrupted or degraded a large proportion of the world’s coastal, marine and freshwater ecosystems.– Approximately 20% of the world's coral reefs

have been destroyed.– During the past 100 years, sea levels have

risen 10-25 centimeters.– We have destroyed more than 1/3 of the

world’s mangrove forests for shipping lanes.

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

• Area of ocean before and after a trawler net, acting like a giant plow, scraped it.

Figure 12-2Figure 12-2

The Deep Sea Conservation Coalition - Multimedia

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

• Harmful invasive species are an increasing threat to marine and freshwater biodiversity.– Bioinvaders are blamed for about 2/3 of

fish extinctions in the U.S. between 1900-2000.

• Almost half of the world’s people live on or near a coastal zone and 80% of ocean water pollution comes from land-based human activities.

Population Growth and Pollution

• Each year plastic items dumped from ships and left as litter on beaches threaten marine life.

Figure 12-3Figure 12-3

Pollution Stock Footage - SD to HD High Definition Pollution Video Clips at Ocean Footage

Overfishing and Extinction: Gone Fishing, Fish Gone

• About 75% of the world’s commercially valuable marine fish species are over fished or fished near their sustainable limits.– Big fish are becoming scarce.– Smaller fish are next.– We throw away 30% of the fish we catch.– We needlessly kill sea mammals and birds.

Fig. 12-A, p. 255

Fish farming in cage

Trawler fishing

Spotter airplane

Sonar

Trawl flap

Trawl lines

Purse-seine fishing

Trawl bagFish school

Drift-net fishingLong line fishing

Lines with hooks

Fish caught by gills

Deep sea aquaculture cage

Float Buoy

Dolphins caught in purse seine net

Whale caught in drift net

Turtle caught in drift net

PROTECTING AND SUSTAINING MARINE BIODIVERSITY

• Laws, international treaties, and education can help reduce the premature extinction of marine species.

• Since 1989 the U.S. government has required offshore shrimp trawlers to use turtle exclusion devices.– Sea turtle tourism brings in almost three

times as much money as the sale of turtle products.

PROTECTING AND SUSTAINING MARINE BIODIVERSITY

• Six of the world’s seven major turtle species are threatened or endangered because of human activities.

Figure 12-4Figure 12-4

Case Study: The Florida Manatee and Water Hyacinths

• Manatee can eat unwanted Water Hyacinths.

• Endangered due to:– Habitat loss.– Entanglement from

fishing lines and nets.– Hit by speed boats.– Stress from cold.– Low reproductive rate

Figure 12-BFigure 12-B

Case Study: Commercial Whaling

• After many of the world’s whale species were overharvested, commercial whaling was banned in 1960, but the ban may be overturned.

Figure 12-6Figure 12-6

Case Study: Commercial

Whaling• Despite ban, Japan,

Norway, and Iceland kill about 1,300 whales of certain species for scientific purposes.– Although meat is still

sold commercially.

Figure 12-5Figure 12-5

Video: Japanese Hunt Humpback Whales

Tradition: Inuit Whale hunting | Versus Country Videos

Fig. 12-7, p. 261

SolutionsManaging Fisheries

Fishery Regulations

Set catch limits well below the maximum sustainable yield

Improve monitoring and enforcement of regulationsEconomic Approaches

Sharply reduce or eliminate fishing subsidies

Charge fees for harvesting fish and shellfish from publicly owned offshore waters

Certify sustainable fisheriesProtected Areas

Establish no-fishing areas

Establish more marine protected areas

Rely more on integrated coastal management

Consumer Information

Label sustainably harvested fish

Publicize overfished and threatened species

Bycatch

Use wide-meshed nets to allow escape of smaller fish

Use net escape devices for sea birds and sea turtles

Ban throwing edible and marketable fish back into the sea

Aquaculture

Restrict coastal locations for fish farms

Control pollution more strictly

Depend more on herbivorous fish species

Nonnative Invasions

Kill organisms in ship ballast water

Filter organisms from ship ballast water

Dump ballast water far at sea and replace with deep-sea water

PROTECTING, SUSTAINING, AND RESTORING WETLANDS

• Requiring government permits for filling or destroying U.S. wetlands has slowed their loss, but attempts to weaken this protection continue.

Figure 12-8Figure 12-8

Fig. 12-9, p. 264

Solutions

Protecting Wetlands

Legally protect existing wetlands

Steer development away from existing wetlands

Use mitigation banking only as a last resort

Require creation and evaluation of a new wetland before destroying an existing wetland

Restore degraded wetlands

Try to prevent and control invasions by nonnative species

Case Study: Restoring the Florida

Everglades• The world’s largest ecological restoration project

involves trying to undo some of the damage inflicted on the Everglades by human activities.– 90% of park’s wading birds have vanished.– Other vertebrate populations down 75-95%.– Large volumes of water that once flowed

through the park have been diverted for crops and cities.

– Runoff has caused noxious algal blooms.

Restoring the Florida

Everglades

• The project has been attempting to restore the Everglades and Florida water supplies.

Figure 12-10Figure 12-10

PROTECTING, SUSTAINING, AND RESTORING LAKES AND RIVERS

• Lakes are difficult to manage and are vulnerable to planned or unplanned introductions of nonnative species.

• For decades, invasions by nonnative species have caused major ecological and economic damage to North America’s Great lakes.– Sea lamprey, zebra mussel, quagga mussel,

Asian carp.

PROTECTING, SUSTAINING, AND RESTORING LAKES AND RIVERS

• We can help sustain freshwater fisheries by building and protecting populations of desirable species, preventing over-fishing, and decreasing populations of less desirable species.

• A federal law helps protect a tiny fraction of U.S. wild and scenic rivers from dams and other forms of development.– National Wild and Scenic Rivers Act

(1968).

Fig. 12-11, p. 267

• Deliver nutrients to sea to help sustain coastal fisheries

• Deposit silt that maintains deltas

• Purify water

• Renew and renourish wetlands

• Provide habitats for wildlife

Natural Capital

Ecological Services of Rivers

Video: Humpback Whales

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Video: Loggerhead Turtles

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Video: Salmons Swimming Upstream

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