A history of whaling

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A history of whaling

• 10th Century records of whaling
• 1400-1700 Atlantic Arctic fishery targeting the
  right whale
• 1600-1900 the Pacific fishery
• more right whales
• 1800-1970s Sperm whale fishery
• Quantity of oil in a sperm whale made it an
  attractive target
• Innovation Possible to make margarine of almost
  100 percent whale oil.

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Sperm Whale (Physeter macrocephalus)
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• 1712 Americans hunt sperm whale

1860 Norwegians introduce steam-powered boats
and explosive harpoons Factory ships and newer
technologies more species, more oceans, more
countries
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Blue whale
Sei whale
Minke whale
Fin whale
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1946 17 nations signed a license where the
International Whaling Commission (IWC) set a
maximum catch in the Antarctic.

• 1949-1960 IWC sets annual fixed quotas for
  all whaling
• 1972 - the United Nations called for a cessation
  of whaling and the United States Congress passed
  an Endangered Species Act
• 1987 - whale sanctuaries were declared in the
  1970s and 80s, and a general moratorium on
  commercial whaling, adopted by the IWC in 1982,
  took effect in 1987

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Populations III Harvest Models
Clupea harengus
Odocoileus virginianus
Pinus sylvestris
Oncorhynchus tshawytscha
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Review

• r intrinsic or per capita growth rate
• dN/dt rN exponential growth
• NtN0ert
• (Were keeping it discrete)

Bye bye fuzzy duckling!!
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Rabbits in Australia invasive species can grow
exponentially at first
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Review

• Logistic growth S-shaped or sigmoid curve
• K carrying capacity
• Modify with unused component of K
• (K-N)/K (1-N/K) used interchangeably
• dN/dt rN(1-N/K)

Logistic growth r0.25 K100
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Review
Ceratotherium simum
Exponential
K100
Logistic
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Review
Environmental resistance
Exponential
K100
Logistic
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How do we use this information to create
harvesting quotas?
Two types of mortality Additive added
mortality causes a reduction in survival any
hunting is added mortality if we want to control
a population of invasives Compensatory added
mortality does not affect survival, up to a
threshold harvesting/ hunting is mortality that
would have happened anyway e.g. starvation,
predation, disease We assume that a
compensatory decrease in non-harvest mortality
occurs perhaps due to extra food availability
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K
Inflection point
K/2
Logistic growth r0.25 K100
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MSY Maximum Sustainable Yield
Logistic growth r0.25 K100
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K
K/2
MSY
Logistic growth r0.25 K100
OSY Optimal Sustainable Yield
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Problems with setting quotas
Estimating numbers is not easy hard to obtain
reliable MSY You cant just stop people that
easily noncompliance is a huge issue K varies
with environment MSY changes
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Factors that affect K

• Density-independent factors
• Weather (storms, cold, drought)
• Density-independent diseases (DDT poisoning)
• Density-dependent factors
• Food
• Space (territories, denning sites, nest cavities)
• Density-dependent epizootics (rabies, SARS)

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Trophic effects on K remove large fish, remove
fish waste, removes fertilizer, removes smaller
fish, up the food chain, less fish to catch
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Fixed Effort harvest
HqEN Yield efficiencyEffortPopulation
E2 gt E1 gt EMSY
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Hindsight always helps the Allee effect Low
population density is prone to sudden extinction
Fewer mating opportunities simply too few to
be fit enough
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• Peruvian anchoveta (Engraulis ringens)
• 1960-1972 worlds largest fishery
• MSY estimated at 10 million tonnes/year
• Expanded fishing fleet plus El Niño events meant
  collapse
• 20,000 people relied on it, so politically
  harmful to close
• Repeated collapses 1973, 1986 still not
  recovered.

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Making a better model

• Fish, deer, trees are not all one size or age
• We prefer adult or mature organisms
• Life-history events reproduction, growth occur
  at different times
• Next Lecture life-tables and age-structure