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Human impacts on Aquatic Biodiversity…. Our large aquatic footprint. Greatest Threat: Habitat Degradation. During the last century we’ve “lost” or damaged: ½ of the world’s coastal wetlands ¼ of the world’s coral reefs (another 70% by 2050) 1/3 of the world’s mangrove forest swamps - PowerPoint PPT Presentation
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Human impacts on Aquatic Biodiversity…
Our large aquatic footprint
Greatest Threat: Habitat Degradation
• During the last century we’ve “lost” or damaged:– ½ of the world’s coastal wetlands– ¼ of the world’s coral reefs (another 70% by
2050)– 1/3 of the world’s mangrove forest swamps– Many bottom habitats due to dredging and
trawler “fishing”
Gone Fishing…Fish Gone
• Overfishing: taking so many fish – too few left to maintain population
• Today’s fishing methods use– Sonar– GPS– Aircrafts
to find fish
Types of fishing:
1. Trawler: drag net on/near ocean floor• Weighed down • “clear cuts” everything on
ocean floor• Nets so big some could
swallow 12 jumbo jets
• LOTS of bycatch: non-target species “accidentally” caught.– Thrown back dead or dying
• T.E.D: Turtle Exclusion Device: a grid of bars with an opening at top/bottom of net; small animals pass through – large ones strike bars and are ejected.
2. Purse-Seine: surround school of fish with net and close net like a drawstring
More bycatch!!
3. Long-lining: put out lines up to 80 miles long with thousands of baited hooks
Even more bycatch!
• Reduce bycatch with longlining… Switch bait!– use of mackerel instead of squid
4. Drift-net fishing: transparent nets (up to 40 miles long and 50 feet deep) hang below surface, marine life becomes ensnared
Bycatch!
Alternatives?Fish farming - Aquaculture
advantages
• Efficient• High yield• Higher yield through cross breeding and
genetic engineering• Reduce overharvesting of conventional
(wild) fisheries• Little use of fuel – profits not tied to price
of oil• High profits
disadvantages• Large inputs of land, feed, and, water needed• Produces large and concentrated outputs of waste• Increased grain production needed to feed some species• Increased catch of other fish as food source• Fish susceptible to pesticide run-off• Dense populations susceptible to disease• Escaped farmed fish can infect wild populations (disease,
parasites, and genetics) – this is a recent headline:“40,000 Atlantic Salmon Escape Canadian Fish Farm Into the Pacific”
• Tanks/ponds/mangrove swamps too contaminated in a few short years (example: shrimp in the Mangrove swamps)
•Total world fisheries collapse by 2048??
ITQ’s
• A TAC (total allowable catch) is set – which is species specific
• “Shares” of the TAC are allocated to fishing vessel owners
• The owners can take their fish quota; or they can buy or sell shares from other owners.
• Difficult to enforce!
• TAC can’t be set too high!!
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