Transcript Unit 4 Fisheries and Aquaculture Review Part 1

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Georges Bank
East Scotian Shelf
Grand Banks
Type of Organisms
Examples
Groundfish
Cod, Haddock, Hake
Pelagic Fish
Sardine, Anchovy, Herring, Mackerel, Tuna
Crustaceans
Crab, Lobster, Shrimp, Krill
Molluscs
Oysters, Mussels, Clams. Squid, Scallops
Stern trawler fishing: After sonar on the trawler finds the fish,
they’re captured by a trawl net more than 122 meters (400
feet) wide. The largest nets extend about 0.8 kilometer behind
the towing vessel and are large enough to hold a dozen 747
jetliners.
• Exploitation of marine organisms for sustenance, profit, or fun.
Why do we fish?
• Survival- many costal
communities, particularly in
developing countries, fish as a
primary food source.
• Recreation- fishing for fun.
• Profit- commercial exploitation
as a means of earning a
livelihood.
What are some of the effects of fishing on
humans?
• Sociology- in some places people need to fish to survive, in many
others they simply want to fish as a mode of recreation.
• Economics- individuals and regions can be dependent on fishing as
a source of income.
• Ecology- natural systems are easily disrupted by fishing.
Today’s Fisheries Are Not Sustainable
• Maximum sustainable yield – maximum amount of
any species that can be harvested without affecting
future yields
• Overfished – status assigned to fish stocks that have
been harvested so there is not enough breeding stock
left for replenishment
• Commercial extinction – depletion of a species to the
point where it is no longer profitable to harvest
• By Catch – animals unintentionally killed when other
species are being harvested
What is “over fishing”?
• Removal of organisms from the marine environment by
humans at a rate which cannot be sustained by the local
ecosystem and therefore significantly alters natural
ecosystem.
or
• Fishing a population faster than it can replace itself; the
population decreases in size as a result.
How big is the problem?
• The world marine catch is nearly 100 million tonnes
per year.
• 27 millon tonnes of by-catch (almost 1/3 of total
catch) is thrown back dead into the ocean
Larger shrimps fetch a
higher price, there is an
incentive for discarding
smaller fish as shown
left.
Over - Whaling continues
• Much more complicated than reduction of
one species
• Trophic interactions
• Examples: Salmon, killer whale, sea
otter
• Change in ecosystem structure
• Loss of biodiversity
• By-catch is all non-target species caught with target
species whether retained then sold or discarded
• Example: Dolphins caught in tuna nets.
• Often a problem with widespread use of unselective
fishing gear
• Bottom trawling disturbs everything on the ocean floor!
Now What?
• How can we fish only to an extent which does not significantly alter it and the natural
system in which it occurs?
• Widely varying degrees of opinion
• Estimating populations
• Estimating catch
• Predicting population
change based on…
• catch.
• environmental statistics
• limited knowledge of life history.
• Tends to err on the side of over harvest (should err on side of
caution  Cautionary Principle)
• Doesn’t always consider ecology
Gulf of Maine fishermen face 6-month cod ban
• Regulation and laws control the total allowable catch (TAC)
• Effective regulation should be consistent with biology; scientist
recommendations should be taken into account.
• International Compliance
• Conservation of marine fisheries impacts peoples
livelihoods, survival, and recreation.
• Influences the marine and terrestrial environments.
• It is everyone's responsibility!!