5.8

• Fisheries: populations of fish used for commercial fishing
• Fishery collapse: when overfishing causes 90% population decline in a fishery

  • Population may never recover from collapse due to decreased biodiversity, inability to find mates, inbreeding depression
  • Economic consequences: lost income for fishermen, lost tourism dollars for communities
• Bottom trawling: harmful fishing method that involves dragging a large net along the ocean floor

  • Bycatch: unintended species like dolphins, whales, turtles caught in nets
  • Stirs up ocean sediment and destroys coral reef structure
  • Decreases biodiversity by killing non-target species and removing coral reef habitat
• Long-line fishing: fishing line with many hooks extended for long distances and allowed to drift

  • Bycatch
  • Ghost fishing: continuous, unintended catch of fish
• Gill nets: Large nets stretching for miles, allowed to drift

  • Mesh size my selectively deplete certain age/size classes
  • Bycatch
  • Ghost fishing
• Purse seines: Large nets are drawn up like a drawstring purse

  • Catches large quantities of fish
  • Bycatch
• Sonar: sound waves used to locate fish

  • Allows ships to locate large schools quickly
  • targets specific species
• • As we deplete large, predatory fisheries, we move down to smaller fish species
  • Depletion of smaller population limits fishery recovery and decreases food supply of marine mammals and seabirds