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Chapter 13
Sustaining Aquatic Food
Resources and
Biodiversity
Chapter Overview Questions
 What
do we know about aquatic biodiversity,
and what is its economic and ecological
importance?
 How are human activities affecting aquatic
biodiversity?
 How can we protect and sustain marine
biodiversity?
 How can we manage and sustain the world’s
marine fisheries?
Chapter Overview Questions (cont’d)
 How
can we protect, sustain, and restore
wetlands?
 How can we protect, sustain, and restore
lakes, rivers, and freshwater fisheries?
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 12-1
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 12-2
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 12-3
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.
Fish farming
in cage
Trawl flap
Trawler
fishing
Spotter airplane
Sonar
Purse-seine fishing
Trawl
lines
Trawl bag
Long line
fishing
Fish
school
Drift-net fishing
Float Buoy
Lines with
hooks
Deep sea
aquaculture cage
Fish caught
by gills
Fig. 12-A, p. 255
Why is it Difficult to Protect Aquatic
Biodiversity?
 Rapid
increasing human impacts, the
invisibility of problems, citizen unawareness,
and lack of legal jurisdiction hinder protection
of aquatic biodiversity.



Human ecological footprint is expanding.
Much of the damage to oceans is not visible to
most people.
Many people incorrectly view the oceans as an
inexhaustible resource.
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 o human
activities.
Figure 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-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 12-6
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 12-5
Toothed whales
Sperm
whale
with
squid
Killer whale
Narwhal
Bottlenose dolphin
Baleen whales
Blue whale
Fin whale
Bowhead
whale
Right
whale
Sei whale
Humpback
whale
Gray whale
Minke whale
Fig. 12-5, p. 258
How Would You Vote?
 Should
carefully controlled commercial
whaling be resumed for species with
populations of 1 million or more?


No. The hunting of whales is no longer
necessary and simply encourages disrespect for
these intelligent giants.
Yes. Some whale species have recovered and
products from them are valuable resources for
humans.
PROTECTING AND SUSTAINING
MARINE BIODIVERSITY
 Fully
protected marine reserves make up less
than 0.3% of the world’s ocean area.

Studies show that fish populations double, size
grows by almost a third, reproduction triples and
species diversity increases by almost one fourth.
 Some
communities work together to develop
integrated plans for managing their coastal
areas.
Revamping Ocean Policy
 Two
recent studies called for an overhaul of
U.S. ocean policy and management.






Develop unified national policy.
Double federal budget for ocean research.
Centralize the National Oceans Agency.
Set up network of marine reserves.
Reorient fisheries management towards
ecosystem function.
Increase public awareness.
MANAGING AND SUSTAINING
MARINE FISHERIES
 There
are a number of ways to manage
marine fisheries more sustainably and protect
marine biodiversity.
 Some fishing communities regulate fish
harvests on their own and others work with
the government to regulate them.

Modern fisheries have weakened the ability of
many coastal communities to regulate their own
fisheries.
Solutions
Managing Fisheries
Fishery Regulations
Bycatch
Set catch limits well below the
maximum sustainable yield
Use wide-meshed nets to allow
escape of smaller fish
Improve monitoring and enforcement
of regulations
Economic Approaches
Use net escape devices for sea
birds and sea turtles
Sharply reduce or eliminate fishing
subsidies
Ban throwing edible and
marketable fish back into the sea
Aquaculture
Charge fees for harvesting fish and shellfish
from publicly owned offshore waters
Restrict coastal locations for fish
farms
Certify sustainable fisheries
Protected Areas
Control pollution more strictly
Establish no-fishing areas
Depend more on herbivorous fish
species
Establish more marine protected areas
Nonnative Invasions
Rely more on integrated coastal
management
Kill organisms in ship ballast water
Consumer Information
Label sustainably harvested fish
Publicize overfished and threatened species
Filter organisms from ship ballast
water
Dump ballast water far at sea and
replace with deep-sea water
Fig. 12-7, p. 261
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 12-8
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
Fig. 12-9, p. 264
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 12-10
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
 Dams
can provide many human benefits but
can also disrupt some of the ecological
services that rivers provide.



119 dams on Columbia River have sharply
reduced (94% drop) populations of wild salmon.
U.S. government has spent $3 billion in
unsuccessful efforts to save the salmon.
Removing hydroelectric dams will restore native
spawning grounds.
How Would You Vote?

Should federal efforts to rebuild wild salmon
populations in the Columbia River Basin be
abandoned?


a. No. Restoring salmon populations is critical for the
environmental health of the river and surrounding
forests.
b. Yes. The restoration program would create
unnecessary and severe economic hardships for
local residents.
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).
Natural Capital
Ecological Services of Rivers
• Deliver nutrients to sea to help sustain
coastal fisheries
• Deposit silt that maintains deltas
• Purify water
• Renew and renourish wetlands
• Provide habitats for wildlife
Fig. 12-11, p. 267