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

• A LOT 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

- bycatch!!

Purse-Seiner Tuna Fishing

3. Long-lining: put out lines up to 80 miles long with thousands of baited hooks

Bycatch still a problem…

“Sea Turtles Accidentally Caught by a Fishing Boat”

• One solution to 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??

• Yes – according to a team of international ecologists AND economists!

“But the issue isn't just having seafood on our plates. Ocean species filter toxins from the water. They protect shorelines. And they reduce the risks of algae blooms such as the red tide.”

“A large and increasing proportion of our population lives close to the coast; thus the loss of services such as flood control and waste detoxification can have disastrous consequences," Worm and colleagues say.

(November 3rd issue of Science)

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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