Overfishing and the State of the Worlds Fisheries

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Overfishing and the State of the Worlds Fisheries

• Marine Biology
• May 2006

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The worlds commercial fleet

• According to UN FAO/World Bank
• 50 trawlers caught 20 of the worlds fish
• 1 of 3.5M fishing boats account for more than
  half of world wide catch
• 10 of the worlds 15M fishers are employed on
  large scale commercial vessels that receive
  almost all of the 25-50B in world wide
  government subsidies
• The large scale industrial fishing fleet has
  increased 22 since 1991 largely driven by
  subsidies
• Since 1975, the size of the fleet has expanded 2X
  faster than rise in catches
• 125B/yr is spent to catch 70B worth of fish.
  Most of the difference are these subsidies
• Many say these subsidies promote overfishinggee,
  ya think?

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The Worlds Fisheries Fleet

• Dominated by huge industrial fishing fleets that
  using sophisticated sonar, huge nets, spotter
  planes, and ships that can process and freeze
  their catch at sea (55 of commercial catch comes
  from the ocean)
• 99 of the above is caught from coastal waters.
• Aquaculture33 of catch
• Inland freshwater12 of catch
• 1/3 of world harvest is used as animal feed, fish
  meal and oils

Spotter airplane
Trawler fishing
Fish farming in cage
Purse-seine fishing
Sonar
trawl flap
trawl lines
trawl bag
Long line fishing
Fish caught by gills
buoy
Lines with hooks
float
Drift-net fishing
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Drift Net Fishing

• Drift net fishing on the high seas beyond the
  exclusive economic zone of any nation was banned
  in 1991 by the UN General Assembly because of its
  potential to harm all fish stocks and marine
  animals.
• This type of fishing involves the use of a net,
  up to twenty miles in extent, that is generally
  anchored to a boat and left to float with the
  tide.
• The net is set out at night and pulled in at
  sunrise, making it difficult for aircraft
  surveillance to catch them in the act.
• On average, a drift net vessel can scoop up half
  a ton of fish per day.
• Method often results in an over harvesting and
  waste of large populations of non-commercial
  marine species (by-catch) by its effect of
  sweeping the ocean clean. The by-catch also
  includes marine mammals and seabirds.

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Depths of water fished in this manner typically
range from 15m to 140m with some fisheries going
as deep as 1800m Lengths of nets can vary from
between 50m to 200m and lengths of fleets from
between 300m and 3000m. The amount of netting
being fished, whether deployed in the water
column or set on the seabed, at any one time can
range from between 2km and 30km. Soak times, the
time that a fleet is left on the seabed to fish,
can range from a 6 hour tidal soak up to 72
hours.
Most selective type
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A trammel net consists of three layers of net. A
slack, small mesh, inner panel of netting is
sandwiched between two outer layers of netting,
which are taught and have a larger mesh size.
Trammel nets are used to catch demersal, benthic
and pelagic speciesHIGH LEVELS OF DISCARD
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LONGLINING
The length of longlines can range from a few
hundred meters in coastal fisheries, to more than
100 km in large-scale mechanized fisheries, to
which thousands of hooks can be attached.
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Purse Seining Methods
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Trawler Fishing/Bottom Trawling
Stop here
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Bottom/Benthic Trawling Equipment
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Untrawled vs. Trawled
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Bottom Trawling

• Bottom trawling involves dragging huge, heavy
  nets along the sea floor. Large metal plates and
  rubber wheels attached to these nets move along
  the bottom and crush nearly everything in their
  path.
• Bottom trawling and dredging reduce habitat
• complexity.
• Repeated trawling and dredging change seafloor
  communities.
• Bottom trawling reduces the productivity of
  seafloor habitats.
• Marine species that live in stable environments,
  such as deep water corals and sponges, are
  generally more susceptible to damage.
• All evidence indicates that deep water lifeforms
  are very slow to recover from such damage, taking
  decades to hundreds of years - if they recover at
  all.
• Major threat to deep sea/marine biodiversity
• If allowed to continue, the bottom trawlers of
  the high seas will destroy deep sea species,
  before we have even discovered much of what is
  out there. Like clear cutting old growth forests
• Outright destroys increases turbidity and
  smothers deep sea corals etc

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Examples of Overfished Species

• Rockfish (aka Pacific Red Snapper)
• Live to 100yrs and dont breed until they are 7
  to 20 years old Bottom trawling gear is used
• Orange Roughy (NZ, Aus, NE Atlantic)
• Lives to 100yrs, dont breed until at least 20
  years old bottom trawling used
• Chilean Seabass (Chile, NZ, Aus, S. Atlantic)
• Half of them in market are caught illegally
  lives 40 years and breeds late in life
• Atlantic Cod (New England)
• Some species are so overfished they are now
  threatened or endangered bottom trawling gear
  used
• Sharks (by catch in so many areas)
• Most dont reproduce quickly enough to keep up
  with global demand for meat and fins 50 million
  sharks are killed each year for their fins alone!
  Mercury contamination a problem!

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The sad state of affairsthe damage

• According to UN FAO and others
• 90 of large fish populations have been
  exterminated in the last 50yrs
• 70 of global fish stocks are fully exploited,
  overexploited, or depleted
• For 200 major fish resources, 35 are overfished,
  25 are being fished to max. potential, and 40
  are in development phase.
• Hence, 60 of worlds stocks require immediate
  and appropriate management measures
• Fisheries rely on relatively few species
• 22 species at over 100K ton/yr five groups make
  up 50 of global fisheries
• Fisheries are increasingly targeting smaller
  lower value pelagic species (b/c large predatory
  fish are mostly gone) that eat lower on food
  chain and are more subject to fluctuations in
  annual productivity
• 2.3 Billion pounds of by-catch in USA alone in
  2000
• World wide 1/4 of total catch is throw overboard
  as by-catch
• Shrimp trawlers discard 85 of their catch making
  it arguably the most environmentally harmful
  fish a person can consume
• According to USFWS
• 14 species (20 of worlds fish) are so
  overfished that if there was an immediate halt,
  it could take up to 20 years for recovery

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Overfishing and Habitat Degradation and its
connection to declines in fish harvests

• Potentially renewable
• Sustainable Yield
• Difficult to determine in mobile populations
• Yearly variability due to several factors
• Harvesting surplus of one species could have
  trophic impacts on others
• Overfishing
• Over time can lead to commercial extinction
• Also increases by catch (27M metric tons/yr)

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Major Threats to Fisheries

• Too many boats!
• Destruction of coastal habitats (important
  breeding and nursery grounds)
• 80-90 of all fish caught within 200mi of coast
• Pollution
• Chemical, nutrient, sediment runoff
• Global warming
• Decline of coral reefs
• Ozone depletion
• Increasing population growth (esp. on coast!)

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Trends in Fisheries Production over time

• Between 1950 and 1999, annual commercial fish
  catch (salt fw) increased almost X5
• Per capita increase of seafood more than doubled
• Since 1982, the annual commercial fish catch has
  increased very little and per capita fish catch
  has been falling since 1992
• Due in large part to overfishing, pollution,
  habitat loss, and population growth especially in
  the coastal zone (50 of world lives here)

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Fig 16-19
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Is Aquaculture the Answer?

• ()Often promoted in press as a good way to boost
  global production while taking pressure off
  overharvested marine fisheries
• (-) Significant loss of sensitive coastal
  ecosystems, lots of issues with untreated waste
  fouling the water antibiotic contamination, use
  of fish meal depletes seas to feed aquaculture
  fish, parasites and disease from farmed species
  can spread to wild fish populations
• 1.5 million hectares of mangroves converted to
  shrimp farms
• 2lbs of wild fish to grow 1lb of shrimp
• Currently supplies 1/3 of commercial harvest
• 90 of oysters, 40 of salmon (75 in US), 65 of
  fw fish
• China is the world leader (68 output)
• Mostly grain fed or fish meal vs. phytoplankton
  in aquaculture systems in developing countries
• Farms vs. Ranches (anadromous species)

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Figure 16-22
Farmed fish are fed 5 pounds of fish meal
(by-catch) for every pound of fish flesh produced
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How do we move towards sustainability?

• Improved Fishery Regulation Management
• Reduce commercial fleet
• Set, monitor, and enforce fishery quotas well
  below MSY
• Reduce by-catch
• Establish no fishing area and marine protected
  areas to facilitate recovery and genetic
  diversity
• Strengthen commitment to biodiversity by
  improving coastal management and land use that
  promote sustainable fishing and ecological
  integrity
• Economic Approaches
• Sharply reduce or eliminate subsidies
• Impose User-pay fees for public waters and use
  the to fund fishery management
• Public Awareness and Consumer Info
• Aquaculture
• Restrict locations to avoid destruction of
  mangroves etc
• Enact stricter pollution regulations
• Increase production of herbivorous fish vs. fish
  meal fed fish

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What can you do?

• Be an educated consumer!
• Ask where the fish comes from and how it is
  caught!
• Use seafood guides to avoid overfished species,
  to choose sustainably caught fish, and to avoid
  fish laden with mercury!
• Seafood Guides here
• Great info at Seafood Alliance