APES Ch 11 Textbook Notes - not complete

research frontier

marine aquatic systems are considered…

trawler

drag huge nets weighted down with heavy chains and steel plates like giant submerged bulldozers over ocean bottoms to harvest bottom fish and shellfish

• These reduce coral reef habitats to rubble and kill a variety of creatures on the bottom by crushing them, burying them in sediment, and exposing them to predators.

• Each year, thousands of trawlers scrape and disturb an area of ocean floor about 150 times larger than the area of forests that are clear-cut annually

freshwater fish species

51% of freshwater fish species—more than any other major type of species—are threatened with premature extinction

invasive species

species that are colonizing 84% of the world’s coastal waters

• arrive in ballast water or by consumers

• ex: asian swamp eel, purple loosestrife

overfishing

For thousands of years, humans in coastal areas have overharvested fishes, shellfish, seals, turtles, whales, and other rmarine mammals (Concept 11-1).

• Today’s fleets can deplete marine life much faster

• All nations are overfishing global oceans by 157%

fishprint

The area of ocean needed to sustain the consumption of an average person, a nation, or the world.

Commercial extinction

occurs when it is no longer profitable to continue fishing the affected species.

• Overfishing usually results in only a temporary depletion of fish stocks, as long as depleted areas and fisheries are allowed to recover.

• However, recovery times are increasing

• ex: Canada’s 500-year-old Atlantic cod fishery off the coast of Newfoundland collapsed and was closed. This put at least 20,000 fishers and fish processors out of work and severely damaged Newfoundland’s economy.

Predatory open-ocean fish

90% of these fish such as tuna, swordfish, and marlin have disappeared

Bycatch

Nontarget species caught through gigantic nets from fishing boats and long lines of hooks.

• Almost 1/3 of annual fish catch is nontarget species that are thrown overboard dead/dying

• Depleted population of species that play important roles

• Marine mammals such as seals, dolphins can be caught as well

Trawler, purse seine, long line, drift net

Fish farming methods

Trawler fishing

• Dragging funnel-shaped net held open at the neck along the ocean bottom

• Used to catch fishes and shellfish—especially shrimp, cod, flounder, and scallops—that live on or near the ocean floor.

• Scrapes up everything on ocean floor, destroys bottom habitats

purse seine fishing

• Used to catch surface-dwelling species such as tuna, mackerel, anchovies, and herring

• Spotter plane locates a school, then fishing vessel encloses it with a large net called a purse seine.

• Nets used to capture yellow fin tuna in the eastern tropical Pacific Ocean have killed large numbers of dolphins that swim on the surface above schools of tuna.

Longline fishing

Involves putting out lines up to 130 kilometers (80 miles) long, hung with thousands of baited hooks.

• Depths of the lines can be adjusted for open-ocean fish species such as swordfish, tuna, and sharks or bottom fishes such as halibut and cod.

• Also hook and kill large numbers endangered sea turtles, dolphins, and seabirds each year.

• Simple modifications to fishing gear and practices can decrease seabird deaths

Drift net fishing

Fish are caught by huge drifting nets that can hang as deep as 15 meters (50 feet) below the surface and extend to 64 kilometers (40 miles) long.

• This method can lead to overfishing of the desired species and may trap and kill large quantities of unwanted fish, marine mammals, sea turtles, and seabirds

• Banned in 1992 by UN