Fisheries

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Fisheries

• Unlike other natural resources such as oil and
  gas, fish are a renewable resource.
• People in coastal regions have been using fish as
  a major food source for thousands of years.

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Fisheries, contd

• In 1997, the global fishery took 100.8 million
  tons of fish, crustaceans and molluscs.
• Fishing also employs 15 million people worldwide,
  but is the most dangerous job in the US (155
  deaths per 100,000 fishers).

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Fisheries, contd

• Of the thousands of species of marine organisms
  in the ocean, only 500 species are regularly
  caught as part of a commercial fishery.
• The largest commercial harvest is of the herring
  and its relatives (sardines, anchovies) which
  comprise a fifth of the worldwide catch of marine
  resources caught each year.

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Major Types of Commercial Fisheries
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Top 5 Fish Harvesters (1998)
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Fishing Methods

• Trawling (Dragging)
• the most common method of fishing
• a funnel-shaped net is towed behind the fishing
  vessel
• can be towed on the bottom to catch groundfish or
  at mid water to catch pelagic fish
• bottom dragging is very destructive to the
  benthic ecosystems

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Trawling
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Fishing Methods

• Gillnetting (Driftnetting)
• a passive fishing method
• a gillnet is a wall of netting set in a straight
  line, equipped with weights at the bottom and
  floats at the top
• fish swim through the net and are caught when
  their gills become entangled in the net, hence
  the name
• if the nets are allowed to drift freely, the
  method is called driftnetting

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Drift Net
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Fishing Methods

• Weirs
• a passive fishing method
• a weir is an enclosure made of nets and poles
  permanently attached to the bottom
• leader fences direct fish into the circular weir
  where they will swim in circles until they are
  purse seined out
• herring and sardines are often caught in weirs

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Weir Off Grand Manan
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Fishing Methods

• Other
• Lobster are caught with lobster pots - baited
  traps with funnel shaped openings allowing only
  one direction of travel - in!
• Scallops are caught by dredging - a metal frame
  with a net attached rakes the sandy bottom
• Squid and cod are often caught by jigging - a
  line of hooks are continually jerked to lure the
  fish to bite

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Lobster Pots
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Bykill

• animals that are unintentionally killed when
  desirable organisms are fished
• in many cases, bykill exceeds the target catch
• thousands of dolphins were bycaught in tuna nets
  until regulations changed the net design and ship
  maneuvers

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Trawling Bykill
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Drift Net Bykill
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Technology Improves Catches

• 75 of fishers are vast commercial fleets who
  find fish by using
• satellite sensors
• aerial photography
• scouting vessels
• sonar
• global positioning systems
• Huge factory ships follow along to can and freeze
  the fish as they are caught

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Declining Fish Populations

• Fish stocks worldwide have been declining many
  have collapsed, due to overfishing - too many
  fishers, too little fish
• Other reasons for declining numbers are
  mismanagement, habitat destruction, interference
  with breeding, increased ocean pollution