Fisheries and Fishing Techniques

What are fisheries?

• A fishing ground for commercial fishing

Where are most fisheries concentrated?

• Most fisheries are concentrated over the continental shelf, in neritic waters. There is high net primary productivity and biodiversity here.

• Marine fisheries systems mainly exploit – shelves surrounding continents, to depth of 200 m– Deeper waters of tropical, temperate, polar areas.

• Here, fisheries dominant environmental change. – changes ecosystem biodiversity and functioning– habitat change from bottom trawling

What is maximum sustainable yield?

• The largest number of fish that can be harvested year after year without diminishing stocks (maintaining levels to carrying capacity of the ecosystem).

What is over exploitation?

• Over fishing or using a resource beyond its maximum sustainable yield.

Central Case: collapse of the cod fisheries

• No fish has more impact on human civilization than the Atlantic cod

• Eastern Canadians and U.S. fishermen have fished for cod for centuries

• Large ships and technology have destroyed the cod fishery

• Even protected stocks are not recovering– Prey may now be competing with,

and eating, young cod

How have techniques changed?

• The Industrial Revolution saw the advent of – steam trawlers – diesel engines– hydraulic winches– inboard refrigeration– echo-sounders– access to real-time oceanographic data

How have techniques changed?

• Fishing boats can rapidly locate, catch and process large quantities of fish

• They can also land them in better condition from longer distances

• The entire world ocean is now accessible to fishing fleets

The total global fisheries catch has increased

What are some Industrialized fishing techniques?

• Factory fishing = highly industrialized, huge vessels use powerful technologies to capture fish in huge volumes

– Even process and freeze their catches while at sea• Driftnets for schools of herring, sardines, mackerel, sharks• Longline fishing for tuna and swordfish • Trawling for pelagic fish and groundfish

Purse-Seining

Purse-Seine target species?

• Yellowfin Tuna• Porpoise bycatch (caught by accident and not

needed=causalty

Pots, Traps and Creels

Small traps baited with fish which are set down on the seabed to catch crabs, lobsters and other seafloor life.

U.S. Commercial Fishery Methods

What is subsistence fishing?

• Fishing to support your family and yourself. • Negatively impacted by industrialized fishing– Societal– Economic

• http://www.filmeducation.org/theendoftheline/senegal.html

• 'The thing is we're too good right now. Technologically, not a single hunted animal on this earth has a chance.'

Professor Jeffrey Hutchings

What is aquaculture?

• Humans rearing selected aquatic plants and animals for human consumption.

• Mariculture? = Marine aquaculture

What are some advantages and disadvantages of fish farming?

advantages

• Reduces pressure on wild fisheries

Disadvantages

• Mariculture is challenging due to physical and chemical components + larval stages and needs

• Can’t sustain human need for food

• Limited space

http://www.filmeducation.org/theendoftheline/fish_farming.html

What is fishing down the food chain?

• >30% U.S. fish stocks are overexploited• For >30% of the rest, insufficient information

to determine status• As one species becomes more rare, fishermen

turn to smaller, once-discarded species: “fishing down the food web” – causes changes in age structure and genetics of populations

We are “fishing down the food chain”

What are the economic consequences in the U.S.?

• NW: – >72,000 jobs lost due to decreasing salmon

populations– $500 million lost

• N Atlantic:– 20,000 jobs lost in 1990’s due to cod fishery

collapse– $350 million lost

How do we preserve the ocean’s fisheries?

• Marine reserves• Regulations• http://www.filmeducation.org/theendofthelin

e/marine_reserves.html

What is the Magnusen-Stevens Act of 1976?

• 200-mile EEZ• Regional Fishery Management Councils (RFMC’s)• Incentives for U.S. fishermen to upgrade vessels• Scientific and Statistical Committees (SSC) to

provide information for managers, but RFMC’s not required to follow their advice: overfishing and slow recovery of overfished stocks

Exclusive Economic Zone (EEZ)

• Countries have the rights to manage and extract resources from an area 200 nautical miles off the coast of its land

• Will include the continental shelf if it extends beyond 200 nautical miles.

• Can overlap, leading to dispute!• Cod Wars UK and Iceland• Areas outside of the EEZ are fair

game for countries to fish

Continued…

• Notes continued on Pollution