Over-Fishing: Impacts, Implications, and Resolutions
Transcript Over-Fishing: Impacts, Implications, and Resolutions
What is “fishing”?
• Exploitation of marine organisms for
sustenance, profit, or fun.
– Fish- cod, halibut, salmon, redfish, stripped bass…
• Mollusks- clams, scallops, oysters, abalone…
• Crustaceans- crabs, shrimp, lobster…
– Reptiles- turtles
– Mammals- whales
Why do we fish?
• Survival- many costal
in developing countries,
fish as a primary food
• Recreation- fishing for
• 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
• Ecology- natural systems are easily
disrupted by fishing.
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
• 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
Larger shrimps fetch a higher
price, there is an incentive for
discarding smaller fish as shown
What are some consequences of
• Much more complicated than
reduction of one species
• Trophic interactions
– Examples: Salmon, killer
whale, sea otter
• Change in ecosystem
• Loss of biodiversity
Consequences…By - Catch!
By-catch is all non-target species caught with
target species whether retained then sold or
• One example of by-catch is dolphins caught in
• Often a problem with widespread use of
unselective fishing gear
• Bottom trawling disturbs everything on the ocean
Collapse of the North Atlantic Cod
– Canadian cod stock severely depleted by
local and distant water fleets
– Canada declared Extended Fisheries
Jurisdiction in 1979 to control and rebuild the
– Expected a rise in Total Allowable Catch
(TAC) by 1985
– Instead the fishery continued to decline and
effectively closed in 1992
– Fishing mortality exceeded sustainable level
– Stocks never achieved 50% of predicted total
– Canadian fleet over harvested cod
• Upper limit was used to calculate harvest
quota every year
• When upper limit became insufficient to
economically support fishery quota was
• Short term economic gain won out over
• Biologists could see the catastrophe
happening and were powerless to stop it
• Long term economic loss (closure of
fishery) far outweighs short term benefit
– Economy loses more
• 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…
– environmental statistics
– limited knowledge of life history.
• Tends to err on the side of over harvest
• Doesn’t always consider ecology
• Marine Protected Areas
– Effective if:
• Large enough
• Protect source populations
• Effectively enforced
– Currently well below 1% of marine systems
are protected by MPA’s
• Through regulation and laws control the
total allowable catch
• Effective regulation should be consistent
• International Compliance
• Increasing evidence suggests impacts of
• Conservation of marine fisheries impacts
peoples livelihoods, survival, and
• It influences the marine and terrestrial
• It is everyone's responsibility.
Case Study: The Impact of
***Please put all answers on looseleaf!
• Vocab: list the definition of the following
fishstock, net growth rate,
MSY, TAC, OSY
• Do case study but omit “l” and “m”
• Do only question #2 from Questions for
Application and Further Research