Transcript Fishing Methods Catch and Bycatch

Fishing = Harvesting = Predation
• Predator-Prey Interaction +with Humans as Predator
• Very high-tech huntinggathering
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Fast boats
Sonar, fish finders
Factory on-board
Midwater, bottom trawl
• Artisenal harvesting
– Coral reefs, intertidal
Exploited Populations
• Sustainable or overexploited?
– Small human populations: local depletion?
• Deforestation of Med/Iceland
• Oysters in Washington State
– Now:
• Larger human populations
• Global markets and distribution
• More people (# and %) in coastal zones
Fishing Methods
Catch and Bycatch
Fishing Effort:
The total fishing gear in use
for a specified period of time.
Fishing Power:
The catch which a
particular gear or vessel takes from
a given density of fish during a
certain time interval.
Bycatch:
Unintended catch of organisms not
part of the fishery being targeted.
Peruvian Anchovy
Peruvian Anchovy
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Small fish, live 3yr, spawn 1yr, caught 5mo+
School near surface
World’s largest fishery until 1972
Major fishery started in 1955
Catch doubled every year 1955-1961
Peak 1971 @ 12.3mt, 18% total fish catch
Peruvian Anchovy Cont’d
• Maximum Sustainable Yield estimated at
about 9 million tons/year
• Assumes no change in environment
• 1972 El Nino, no upwelling/nutrients
• 1972 few young, lots of adults, huge catch
• Crash of fishery, hasn’t recovered
• Huge economic consequences
Principles of Exploitation
• Below certain levels, populations resilient –
increase growth or survival to compensate for
fishing losses (removal of indivs)
• Above certain levels, local or global extinction of
the resource ($ or actual)
• Somewhere in middle, level of “maximum
sustainable yield” – hard to apply in the real
world
• Social resilience and precautionary principle?
Beyond Single-Species
Approaches
What about habitat, species
interactions, climate change?
A framework for fishing pressure
Kinds of Bycatch
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Fish of wrong (non-target) species
Fish that are of the wrong size
Fish that are of the wrong sex
Fish that are damaged (caused by
gear or predation in the gear)
Excess fish discarded when quota
reached
High-grading (low market value,
damaged, or poor quality fish)
Prohibited species - any species
which must by law be returned to
the sea (i.e. marine mammals,
turtles, birds, and other fish)
Population impacts vs economic
benefit
Some Solutions to Bycatch
• Selective Fishing Gear
– Turtle Excluder
Devices (TEDs)
– Deeper Longlines
• Integrating Fisheries
and Conservation
– MPAs and BFFF
– No take zones, goals?
• Product certification
Ecosystem Based Management
• The effect of the environment on the
resource (population biology and habitat!)
• The effect of resource exploitation on the
environment (food webs, energy)
• Complex ecosystems, uncertainty, tipping
points, and the precautionary principle
• The human factor – fishing communities,
cultures, practices, and economies
Other Issues to Consider
• Western Science vs Traditional Ecological
Knowledge
• Enforcement of Regulations and Rules
• Markets and Externalities (ITQs)
• Climate Change and Uncertainties of
Oceans’ ability to produce fish
• Social and ecological resilience, coupling!