5.8 - Impacts of Overfishing

Question 1

Fisheries and Fisheries Collapse

Answer 1

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

Problems with overfishing:
- Pop. may never recover from fishery collapse due to: decreased biodiversity, inability to find mates, inbreeding depression
- Decreases genetic biodiversity of fish populations & species biodiversity of ocean ecosystems if species are lost from ecosystem
- Economic consequences: lost income for fishermen, lost tourism dollars for communities

Question 2

Bottom Trawling

Answer 2

• Especially harmful fishing method that involves draggin a large net along ocean floor

Problems:
- Bycatch: unintended species like dolphins, whales, turtles caught in nets
- Stirs up ocean sediment (turbidity) & destroys coral reef structure
- Decreases biodiv. by killing non-target species & removing coral reef habitat

Question 3

Fishing down the food web and trophic cascade

Answer 3

• As we deplete large, predatory fisheries, we move down to smaller fish species
• Depletion of smaller fish pop. limits fishery recovery and decreases food supply of marine mammals & seabirds