Miller—Chapter 13-6

Fisheries
 3rd
major food producing system
 Definition: Concentrations of particular
aquatic species suitable for commercial
harvesting in given ocean area or inland
body of water
Examples: Cod, tuna, mackerel, sardine,
anchovy, crab, shrimp, oyster, clam, squid,
octopus
Most of (99%) catch is taken from coastal
waters (as a result disrupted/polluted)

Fishing Industrialization
 Fleets use:
Satellite positioning
equipment
Sonar
Huge nets
Spotter planes
Factory ships that can
process and freeze their
catches

Types of Fish
 Demersal: Mostly bottom-
dwelling
 Pelagic: Surface-dwelling
 Crustaceans: Hard
exoskeleton
 Mollusks: Live in hard
shell

Harvesting Methods
 To catch demersal and
shellfish (shrimp)
 Drag funnel-shaped net
held open at the neck along
the ocean bottom
 Destroys bottom habitats
 Nets big enough for 12
jumbo jets
 Small fish escape, but
other species (seals,
turtles) can be trapped
 Bycatch (other throwback
species) get released
 To catch pelagic species,
such as tuna (feed near
surface in schools)
 Looks like a large
drawstring purse to trap
fish
 Can also kill other species,
ex: dolphins, which swim
near surface with fish
species

Harvesting Methods
 Put out lines of 80 mile-long
hung with thousands of baited
hooks to catch open-ocean
fish species (swordfish, tuna,
sharks)
 Can hook pilot whales,
dolphins, turtles and sea-
feeding bird, the albatross.
 Uses huge drifting nets that
hang about 15 meters below
surface and are up to 34 miles
long
 Can lead to overfishing
 Traps/Kills large quantities of
unwanted species, like
longlining.
 US has banned nets longer
than 1.6 miles in international
waters
 Compliance is voluntary, difficult
to monitor fishing fleets and now
more longlines are used which
are also dangerous

Harvesting Methods

Fishing
 The remaining 1% comes from aquaculture
and inland freshwater lakes/ponds, rivers
 Between 1950-1982, the commercial fish
catch has increased 5-fold.
Since ‘82, catch amount has slowed down and
will continue to decline…Why?
 Want to achieve a “sustainable yield”
The size of the annual catch that could be
harvested indefinitely without a decline in the
population of a species
○ Challenges: Hard to monitor mobile populations
and populations shifts year-to-year due to climate,
pollution and other factors

Overfishing
 Taking so many of the fish that too little
breeding stock if left to maintain
numbers (exceeds its sustainable yield)
If continues, can lead to commercial
extinction
Too many fishing boats pursuing too few
fish (tragedy of the commons)
Leads to a lot of political disputes (over 100
disputes about rights between countries)
There are 14 fisheries that are so depleted it
would take 20 years for them to replenish
the stocks if they halted everything now

Overfishing Problem

Other Problems
 Degradation/destruction/pollution of
wetlands, estuaries, coral reeds, salt
marshes, mangroves
 Projected global warming because there
will be warmer ocean waters that would
degrade or destroy coral reeds, enhance
effects from habitat degradation
 Thinning of ozone causes more UV
radiation penetrating into the water
 El Nino warming patterns

A possible answer:
Aquaculture
 Fish/shellfish are raised for food, supplies.
*China is leader in this practice.
 Two types:
Fish farming: Cultivates fish in a controlled
environment (coastal/inland pond/lake/rice paddy)
and harvest them when they reach desired size
Fish ranching: Holding anadromous (breed in
freshwater) species such as salmon, live in captivity
for their first few years of their lives (fenced in areas,
lagoons, estuaries) then release them and harvest
when adults return to spawn
 Typical fish species: Carp, catfish, tilapia,
milkfish, clams and oysters

Aquaculture
 Some countries (China) combine with agriculture.
They use pig manure and other waste to fertilize
aquaculture ponds, promoting growth of
phytoplankton to feed species
 Used to stock for game fish purposes or to raise the
expensive fish and shellfish
 90% of all oysters
 40% salmon (75% in US)
 50% of internationally traded shrimp and prawns
 65% freshwater fish sold in marketplace
 Catfish is leading product in US (Mississippi, Louisiana, Arkansas,
Alabama)
 Some studies show that aquaculture has worsened
the problem for fisheries by:
 Raising demand for some ocean fish (anchovies) that are
ground into fish meal and fed to aquaculture species
 Create vast amounts of waste in the coastal areas

Aquaculture
ADVANTAGES DISADVANTAGES
 Highly efficient
 High yield in small volume of
water
 Increase yield through
crossbreeding and genetic
engineering
 Can reduce overharvesting of
conventional fisheries
 Little use of fuel
 Profits not tied to price of oil
 High profits
 Large inputs of land, feed and
water needed
 Produces large and
concentrated outputs of waste
 Destroys mangrove forests
 Increased grain production
needed to feed some species
 Fish can be killed by pesticide
runoff from nearby cropland
 Dense populations are
vulnerable to diseases
 Tanks too contaminated to
use after about 5 years