Conservation of fishing ground

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Conservation of fishing ground

• Rivers,oceans and lakes constitute fishing
  grounds
• To conserve fishing grounds, indiscriminate
  fishing should be discouraged.
• If no. of fish removed from a population exceeds
  the no. of young fish reaching maturity, the
  population will decline.
• E.g.Over-fishing of herring in the North Sea
• 1965 1.3million tonnes of herring were caught
  in the North Sea
• 1977 catch diminished to 44 000tonnes i.e. 3
  of 1965 catch

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Conservation

• Fisheries Management

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Big Fish DeclineThe Straits Times , May 17 2003
5 or more fish caught fewer than 5 fish
caught
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Big Fish Decline

• Big fish tuna, cod, halibut, skates, flounder,
  marlin, swordfish, sharks
• Since industrialised fishing began in 1950s, the
  global ocean has lost over 90 of its big fish.
  Nature magazine.
• Large fish have also declined in size. The blue
  marlin now reaches one fifth its size in the
  1950s.
• If current fishing practices continue, the world
  will face serious
• economic disruptions
• food shortages in seafood-dependent developing
  nations
• lasting damage to marine ecosystems.

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• Whaling has reduced population of many whale
  species to endangered levels.
• Measures of conservation
• 1. Ban use of drift nets ? prevents
  indiscriminate trapping of all forms of sea life
• 2. Fix mesh size of nets ? only mature fish above
  certain size are caught, young fish are left to
  breed
• 3. Regulate size of fishing boats in fishing
  grounds
• 4. Limit fishing periods --- impose closed
  seasons when no fishing is allowed
• 5. Ban harvesting of endangered species
• 6. Raise endangered species in hatcheries and
  release them into fishing grounds where fish
  population is decreasing

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Checking net size
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• Fish farming
• If well managed can provide valuable protein
  without damage to environment and at reduced
  cost.
• If poorly managed can cause pollution and disturb
  natural communities.
• Inland fish farms freshwater ponds, used water
  from farms should be passed through settling
  tanks to precipitate organic debris before
  returning water to rivers to prevent pollution
  and eutrophication.

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Inland fish farm
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• Offshore fish farms
• Fish cages should be moved frequently to prevent
  settling of fish faeces on the sea bed below
  which affects the local ecosystem.
• Escaped fish may breed with wild stock and weaken
  population as farmed fish usually have
  characteristics that are unlikely to be
  beneficial in the natural environment.
• Disease spread easily in monocultures where
  single species is grown at high density. Escaped
  diseased fish may spread disease to wild stock.
• Antibiotics used by fish farmers to control
  diseases may lead to pathogens developing
  immunity and also put antibiotics into human food
  chain.

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Offshore fish farm
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ACE

• Now that you have completed the materials for
  this topic, you may attempt the Webquest activity
  on Nassau Grouper (Refer to Main Lesson Schedule).