Commercial fishing:
• 500 species regularly caught
• Employs 200 million people worldwide
• In 2002 the world fishing fleet numbered
about four million vessels.
In 2005:
• 100 million tons taken
• $70 billion
Global Fish Catch
Emptying the oceans
• We are placing unprecedented pressure on
marine resources
- Half the world’s marine fish populations are fully
exploited
- 25% of fish population are overexploited and
heading to extinction
• Total fisheries catch leveled off after 1998,
despite increased fishing effort
- It is predicted that populations of all ocean species
we fish for today will collapse by the year 2048
Fish Population Estimates
800
80
Abundance
70
Harvest
600
50
400
40
30
200
20
10
0
1960
1970
1980
Year
1990
2000
Abundance
(kilograms/tow)
Harvest
(thousands of metric tons)
60
We have long overfished
• People began depleting sea life centuries ago
• Some species hunted to extinction: Steller’s sea cow, Atlantic
gray whale, Caribbean monk seal
• Overharvesting of Chesapeake Bay oyster beds led to the
collapse of its fishery, eutrophication, and hypoxia
• Decreased sea turtle populations causes overgrowth of sea
grass and can cause sea grass wasting disease
• People never imagined that groundfish could be depleted
- New approaches or technologies increased catch rates
Fishing Techniques
Fishing Methods
• Harpoon - whales, swordfish, bluefin tuna
• Pole and line - mahi-mahi and used for tuna
extensively in the 50‘s
• Longline - swordfish, tuna (pelagic); cod,
halibut (bottom)
• Trolling - salmon, albacore, mahi-mahi
• Drift (gill) netting - various pelagic fish
• Trawl - anchovies (pelagic); cod, halibut
(bottom)
• Purse seine - sardines, herring, mackerel
• Traps and Pots - Crabs, lobster, rock fish
Gillnetting
Uses curtains of
netting suspended
by a system of
floats and weights
Either anchored to
sea floor or float at
the sea surface
Netting is almost
invisible, fish swim
right into it; and
their gills get
caught
net size:
20 m x 65 km
Drift Netting
Driftnets have earned the
nickname “walls of death.”
•Large floating nets
•Unbreakable and invisible to
most sea species
•likely to entangle large pelagic
species:dolphins, whales,
sharks, turtles, and rays.
Longlining
•Longlines are horizontal sets of fishing hooks
•Set on the ocean floor: demersal longlines
•Set near the surface: pelagic longlines
•Longlines can be tens of kilometres long
•Can carry thousands of hooks
•Baited hooks are attached to the longline by short
lines called snoods that hang off the mainline.
•Not anchored; set to drift near the surface of the ocean
•Attached radio beacon tracks line to haul in catch
•Usually used to catch large tuna and billfish species.
•Anchored to the sea floor.
•Buoys mark line
•Same as Pelagic longline in all other respects
Purse seine
Animation
•Uses large wall of
netting to encircle
schools of fish
•Drawstring pulls
bottom of netting
closed, like a purse
•Herds schools of
fish into center
•Some purse
seines can
unintentionally
catch other animals
(dolphin caught
when fishing for
tuna)
Trawl
bottom
midwater
http://www.youtube.com/watch?v=bUHcD_jTgVA
Effects of Trawling on Coral Reefs
http://www.eea.europa.eu/publications/report_2002_0524_154909/regional-seas-around-europe/page111.html
Trawl from space
Gulf of Mexico, near Louisiana coast. Individual vessels can be seen as bright
spots at end of sediment trails. Other bright spots are fixed oil and gas production
platforms. One sediment trail can be traced for 27 km. Assuming a standard
trawling speed of 2.5 knots, sediment from this trawl is visibly persistent for nearly
6 hours. Water depth <20m. Large, indistinct bright blue patches at lower left and
upper right are cloud/haze. (Credit: Landsat)
Sonar
• Uses sound waves that
allow fishermen to
quickly locate fish
and/or see the bottom
• Targets specific species
Image: http://www.marinesonic.com
Factory Ship
Courtesy of Wikipedia Commons
Types: demersal (weighted bottom trawling)
-pelagic (mid-water trawling)
- pair trawling, two vessels, 500 metres apart, both pull
huge net with a mouth circumference of 900 meters
•Can haul in
LARGE
quantities of
fish
•Can process
and freeze fish
onboard
•Up to 60 - 70
meters long
•Can be at sea
for six weeks at
a time with a
crew of over 35
people.
Pole / Troll
•Uses fishing
pole and bait to
target fish
•Environmentally
responsible;
alternative to
longlining
•pole/troll
fishermen have
very low bycatch
rates.
Fisheries mismanagement
•
•
•
•
Overfishing
Commercial extinction
Bycatch (27 million metric tons annually)
Targeting smaller species on the low end of the
food chain
Fisheries Problems & Solutions
A. Maximum sustainable yield: maximum amount of
fish that can be harvested without depleting
future stocks
B. World‘s maximum sustainable yield estimated at
100 to 135 million metric tons
C. Present harvests are at about 100 million metric
tons
D. For fisheries where numbers available,
estimated that 45% are currently over-fished
E. A number of fisheries have already collapsed
(Anchovy fishery off Peru, Cod fishery in the N.
Atlantic)
Fisheries Problems & Solutions
F. Bycatch (or bykill): animals unintentionally killed during
harvest of the target species
Trawling: Bycatch in shrimp trawling is very high (125 to
830% of the catch is discarded as bycatch), turtles often
caught in trawls.
SOLUTION: trawls with trap doors to let turtles escape
•Allows smaller fish to be caught
•Allows turtles to escape
•Lowers incidence of bycatch
•Same concept as TEDs
•Hatch kept open with inflatables
Modern fishing fleets deplete marine
life rapidly
• Grand Banks cod have been fished for centuries
• Catches more than doubled with immense
industrial trawlers
- Record-high catches lasted only 10 years
Bycatch by Gear Type for 2002/2003
Purse seine: Tuna known to hang out under pods of
dolphins, nets set around pods of dolphins would result
in many drowning.
SOLUTIONS: Nets not set around dolphin pods and/or
employ — “backing down”, a technique that lowers
upper edge of net letting dolphins escape
Dolphins caught in tuna net
Fisheries Problems & Solutions
Driftnets: indiscriminate entangling of many sorts of
marine animals
SOLUTION: banned in oceanic fisheries (but some
countries still using them)
Fisheries Problems & Solutions
Long lining: Many albatross drown trying to snatch
bait from long lines being deployed. snagged on
hooks and pulled under.
SOLUTION: deploy in the dark or with special rig to
let line out under water.
Global swordfish catch
450
Ave. wt. in lbs
400
350
300
250
N. Atlantic
Swordfish
200
150
100
50
0
1817
1861
1900
year
1961
http://www.pifsc.noaa.gov/wpa
cfin/hi/dar/Pages/hi_fish_2.php
Artificial Reefs
Improve the local marine bio-density
1. attract schools of fish
2. providing habitats for the colonization
of commercially valuable species
3. improve the local inshore marine
harvest
May wash up
on beaches
tires
ship wrecks
construction rubble
Aquaculture
(marine agriculture)- farming
finfish, shellfish and algae under
favorable conditions
One of every four
fish eaten today was
raised in either a fw
or sw fish farm.
Aquaculture also produces:
• Bait fish
• Ornamental or aquarium fish
• Aquatic animals used to augment
natural populations
• Algae for chemical extraction
• Pearl oysters
History:
• 2000 years ago in Egypt, Rome, China
• <2000 years in Hawaii
• 600 years ago France developed mussel
aquaculture
• 500 years ago Europe developed the idea of
using pond fertilizer to promote plankton
growth
• 400 years ago China discovered that oysters
would grow on bamboo stakes
• 1960’s- Europe and U.S. catfish and salmon
Criteria for selecting species for
farming:
- inexpensive to grow
- grows quickly
- high sales price
- resistant to disease and parasites
Hawaii open ocean aquaculture
Mio, big eye tuna, yellow tail
$34.7 million in 2008
Industrialized fishing depletes populations
• Catch rates drop precipitously with industrialized fishing
- 90% of large-bodied fish and sharks are eliminated within 10
years
- Populations stabilize at 10% of their former levels
• Marine communities may have been very different before
industrial fishing
- Removing animals at higher trophic levels allows prey to
proliferate and change communities
Several factors mask declines
• Industrialized fishing has depleted stocks, global catch has
remained stable for the past 20 years
- Fishing fleets travel longer distances to reach less-fished
portions of the ocean
- Fleets spend more time fishing and have been setting out
more nets and lines, increasing effort to catch the same
number of fish
- Improved technologies: faster ships, sonar mapping,
satellite navigation, thermal sensing, aerial spotting
- Data supplied to international monitoring agencies may be
false
We are “fishing down the food chain”
• Figures on total global catch do not relate the species, age, and size
of fish harvested
• As fishing increases, the size and age of fish caught decline
- 10-year-old cod, once common, are now rare
• As species become too rare to fish, fleets target other species
- Shifting from large, desirable species to smaller, less desirable
ones
- Entails catching species at lower trophic levels
Consumer choices influence fishing practices
• Buy ecolabeled seafood
- Dolphin-safe tuna
• Consumers don’t know how their
seafood was caught
- Nonprofit organizations have
devised guides for consumers
- Best choices: farmed catfish and
caviar, sardines, Canadian snow crab
- Avoid: Atlantic cod, wild-caught
caviar, sharks, farmed salmon
The Big Question
• Fish Populations are declining
• The Human Population is increasing
exponentially
• What can be done to sustain fish as a viable
food resource for the human population?
• What YOU can do: Choose to eat
sustainably harvested seafood
Trade-Offs
Aquaculture
Advantages
Highly efficient
High yield in small
volume of water
Increased yields
through crossbreeding and genetic
engineering
Can reduce overharvesting of
conventional fisheries
Little use of fuel
Profit not tied to price
of oil
High profits
Disadvantages
Large inputs of land, feed,
And water needed
Produces large and
concentrated outputs of
waste
Aquaculture
Methods
Destroys mangrove forests
Increased grain production
needed to feed some
species
Fish can be killed by
pesticide runoff from
nearby cropland
Dense populations
vulnerable to disease
Tanks too contaminated to
use after about 5 years
Is Aquaculture
the Answer?
Solutions
More Sustainable Aquaculture
• Reduce use of fishmeal as a feed to reduce depletion of other fish
• Improve pollution management of aquaculture wastes
• Reduce escape of aquaculture species into the wild
• Restrict location of fish farms to reduce loss of mangrove forests and
other threatened areas
• Farm some aquaculture species (such as salmon and cobia) in deeply
submerged cages to protect them from wave action and predators and
allow dilution of wastes into the ocean
• Set up a system for certifying sustainable forms of aquaculture
Relevant Laws
• UN Law of the Seas
• Magnuson-Stevens Fisheries Management and
Conservation Act (Magnuson Act)
• Marine Sanctuaries Act
• Oceans Act of 2000
• Endangered Species Act (ESA)
• Convention on International Trade in Endangered
Species (CITES)
• Lacey Act of 1900
Laws Related to Fishery Management
• Magnuson Act
• UN Law of the Seas
- Nations have jurisdiction
over Exclusive Economic
Zones (200 Miles)
- Sea Floor sovereignty up to
12 miles offshore
- Allows for Individual
Transferable Quotas which
can be sold to others
- Establishes 200 mile fishing
area
- Set up regional councils that
- Set quotas
- Set size limits
- Set seasons
- Protects habitat
- Minimizes bycatch
- Rebuilds overfished stocks
Fisheries management
• Based on maximum sustained yield
- Maximal harvest while keeping fish available for the future
- Managers may limit the harvested or restrict gear used
• Despite management, stocks have plummeted
- It is time to rethink fisheries management
• Ecosystem-based management
- Shift away from species and toward the larger ecosystem
- Consider the impacts of fishing on habitat and species
interactions
- Set aside areas of oceans free from human interference
We can protect areas in the ocean
• Marine protected areas (MPAs) = established
along the coastlines of developed countries
- Still allow fishing or other extractive activities
• Marine reserves = areas where fishing is
prohibited
- Leave ecosystems intact, without human interference
- Improve fisheries, because young fish will disperse
into surrounding areas
• Many commercial, recreation fishers, and
businesses do not support reserves
Reserves work for both fish and fisheries
• Found that reserves do work as win-win solutions
• Overall benefits included…
- Boosting fish biomass
- Boosting total catch
- Increasing fish size
• Benefits inside reserve boundaries included…
- Rapid and long-term increases in marine organisms
- Decrease mortality and habitat destruction
- Lessen the likelihood of extirpation of species
Areas outside reserves also benefit
• Benefits included…
- A “spillover effect” when individuals of protected
species spread outside reserves
- Larvae of species protected within reserves “seed the
seas” outside reserves
- Improved fishing and ecotourism
How should reserves be designed?
• 20-50% of the ocean should be protected in no-take
reserves
- How large?
- How many?
- Where?
• Involving fishers is crucial to fisheries to determine the
answers
Laws Related to Habitat Protection
• Marine Sanctuaries
Act
• Oceans Act of 2000
- Established Presidential
Commission to
- Protects habitat of
marine organisms
- Examine Federal
Ocean Policy
- Protects animals from
being harvested in that
area
- Promote protection of
marine environments
- Prevent marine
pollution
Laws Related to Species Protection
• ESA
- Identifies and lists
endangered species
- Prohibits the harm or
harvesting of listed
species
- Protects habitat
• CITES
- Identifies and lists
endangered species
- Prohibits international
trade in listed species
• Lacey Act of 1900
- Prohibits sale of
illegally harvested
species
- Forces legal methods
Conclusion
• Oceans cover most of our planet and contain
diverse topography and ecosystems
• We are learning about the oceans and coastal
environments, intensifying our use of their
resources, and causing severe impacts
• Setting aside protected areas of the ocean can
serve to maintain natural systems and enhance
fisheries
• We may once again attain the ecological
systems that once flourished in our waters
QUESTION: Review
•
Which of the following does not mask the decline of
fisheries?
–
–
–
–
Fishing fleets travel longer distances
Fishing fleets spend more time fishing
Fishing fleets use traditional methods of fishing
Data supplied to monitoring agencies may be false
QUESTION: Review
•
Marine reserves have all the following benefits except:
–
–
–
–
Fishing increases in the reserve
The size of fish increases
Larvae can “seed” areas outside the reserve
Decreased mortality and habitat destruction
QUESTION: Interpreting Graphs and
Data
•What does this graph show about the future of global fisheries
catch?
a) China will be a major
player in applying fishing
pressure
b) China will be playing a
smaller role in applying
fishing pressure
c) The world will decrease its
fishing pressure
d) The U.S. is not included in
this graph
QUESTION: Interpreting Graphs and
Data
• Which conclusion can you draw from this graph?
a) Oceans today contain far
fewer fish
b) Oceans today contain far
more fish
c) It is easier to find fish today
d) There is little correlation
between fishing and fish
stocks
QUESTION: Viewpoints
•
If a developer wants to build a community on an estuary,
providing jobs but eliminating the marsh, what should be
done?
–
–
–
–
Let the developer build; we need the jobs
Let the developer build, but make him/her pay for any
damage from storms
Let the surrounding landowners vote whether to let
the developer build
Prevent the development; the potential damage is
too great
QUESTION: Viewpoints
•
Do you plan to alter your decisions about eating seafood?
–
–
Yes; I will be more selective about what I eat
No; I will continue to eat the same type and amount of
seafood as always