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Sustaining Fisheries and Catching Fish. Brian Diaz Braulio Socarras. The Food We Rely On. Many people rely on fisheries for food.

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sustaining fisheries and catching fish

Sustaining Fisheries and Catching Fish

Brian Diaz


the food we rely on
The Food We Rely On
  • Many people rely on fisheries for food.
  • Fish and shellfish supply about 7% of the global food supply and are the primary source of animal protein to 1 billion people (about 15% of the human population), mostly in developing countries.
  • High demand= many fish species have become overharvested.
  • As fisheries become depleted, those species that used to rely of the fish die off as well.

fishing down the food chain
Fishing Down the Food Chain
  • Cod, tuna, and snapper are top carnivores in ocean food webs.
  • As they are depleted, lower trophic level fish are caught for food. These smaller fish are usually much more undesirable.
  • The UN says that overall trophic levels in fisheries have decreased.
  • As these lower trophic level fish die off, so does the fishing business (like the North Atlantic cod fisheries).

sustaining fisheries
Sustaining Fisheries
  • Few countries manage their fisheries in a sustainable manner.
  • Potential solutions include:
    • Making “no-take” zones, where fishing is not permitted
      • Fish are plentiful here
      • When populations are high enough here, large fish go back to fishing zones.
      • No take zones are a recovery mechanism.

  • Aquaculture means raising fish and shellfish as crops instead of hunting them. It is the world’s fastest-growing food production.
  • There are two kinds:
    • Fish farming: cultivating fish in a controlled environment
    • Fish ranching: Raising fish young, releasing them, and recapturing them when they grow and return to spawn. (Salmon)
  • Aquaculture is highly efficient and has little use of fuel, but it requires a lot of land, feed, and water. It also produces concentrated waste. Tanks become too contaminated to use after about 5 years.

methods of fishing trawler fishing
Methods of Fishing (Trawler fishing)
  • Trawler fishing is used to catch food species on the ocean bottom. A funnel shaped net help open at the neck is dragged along the bottom.
  • These nets capture everything on the ocean bottom, not just target species. They cause enormous damage to the sea environment and are huge, meaning they can take up large amounts of fish.
  • A lot of bycatch

purse seining and longlining
Purse seining and Longlining
  • Purse saining catches surface fish like tuna and anchovies. After finding a large school of fish, a purse like net closes up (drawstring purse), capturing the fish. Dolphins are sometimes captured.
  • Longlining involves putting out fishing lines that are 80 mile long, with thousands of baited hooks. These hooks catch swordfish, tuna, and sharks. They also may catch sea turtles, albatrosses (birds), and occasionally dolphins.

dfrift net fishing
Dfrift-net Fishing
  • Drift nets that are as long as 40 miles are set out. Anything that gets into contact with the net quickly becomes entangled. These include huge amounts of prey species and bycatch (including marine mammals and sea turtles).
  • The UN banned drift nets longer than 1.6 miles long in 1992. Still, long nets are used because compliance is only voluntary.

overfishing and bycatch what our oceans should be like
Overfishing and Bycatch/ What our Oceans Should be like

5 important points
5 Important points
  • 7% of the global food supply comes from fish and shellfish and over 1 billion people rely on fisheries for food.
  • As overfishing of top predator fish occurs, they are replaced by lower trophic level species.
  • Aquaculture may be an alternative hunting wild fish, but they produce contaminants and infected water as well as require a lot of resources.
  • The four main fishing methods are trawling, purse-seining, drift-nets, and longlining.
  • These methods can catch a lot of desirable fish, but cause overfishing and large amounts of bycatch.
  • Living in the Environment (Tyler Miller)
  • “Purple Environmental Book”