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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
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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: • 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
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
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)
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!!
