APES – Chapter 14: Wildlife, Fisheries, and Endangered Species
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Tommy Hicks
APES – 6th period
Case Study: Threats to Major World Fisheries
- Many species are on the brink of extinction
- The goal is to maintain/establish sustainable fisheries
o Maximum sustainable yield
- Commercially caught fish: roundnose grenadier, blue hake,
- Fish that are “by catch” are fish caught when catching other fish – they usually die
- These commercially caught fish have long lies and so when they are overharvested, they disappear
quickly
- Bottom trawlers – drag across ocean floor – destruction
- Decline corresponds to the timing of increased fishing
Wildlife, Fisheries, and Endangered Species
Common history of exploitation, management and conservation
When saving a species, what is it we really want to save?
o 1. A wild creature in a wild habitat, as a symbol to us of wilderness.
o 2. A wild creature in a managed habitat.
o 3. A population in a zoo.
o 4. Genetic material only.
Involves science and values
Many reasons for wishing to save endangered species.
Policies and actions differ widely depending on goal chosen.
Single-Species Wildlife Management
Conservation and management often viewed each species as a single population in isolation.
o 1. The population could be represented by a single number, its total size.
o 2. Undisturbed by human activities, a population would grow to a fixed size, called the “carrying
capacity”.
o 3. Environment, except for human-induced changes, is constant.
This perception illustrated by the S-shaped logistic growth equation.
Two goals resulted:
o 1. For a species we intend to harvest: maximum sustainable yield
o 2. For a species we intend to conserve: remain at its carrying capacity
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This approach failed.
o None of the assumptions were true.
o Population cannot be represented only by a single number.
o Do not remain at a fixed carrying capacity.
o The environment is not constant.
Necessary to include an ecosystem and landscape context for conservation and management.
New goals:
o For a species to be harvested: sustain a harvestable population in a sustainable ecosystem
o For a species that is threatened or endangered: minimum viable population
Logistic Growth Curve
Include the following ideas:
o A population that is small in relation to its resources grows at a nearly exponential rate.
o Competition among individuals in the population slows the growth rate.
o The greater the # of ind, the greater the competition and the slower the rate of growth.
o Eventually, a point is reached, called the “logistic carrying capacity”.
o At this level, the # of births in a unit time equals the number of deaths, and the population is
constant.
o A population can be described simply by its total #.
o Therefore, all individuals are equal.
o The environment is assumed to be constant.
Carrying Capacity
Has three definitions.
o 1. Logistical carrying capacity- the # of ind is just sufficient for the available resources.
o 2. An abundance at which a population can sustain itself w/o any detrimental effects that
would decrease the ability of that species to maintain that abundance.
o 3. Optimum sustainable population- the max pop that can be sustained indefinitely.
Logistic Growth Curve
Another key concept is that the population size that provides the max sustainable yield
o Exactly one-half of the carrying capacity.
o Other estimating MSY will lead to overharvesting.
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The Grizzly Bear
An endangered species
o US Fish and Wildlife Service must meet the requirements of ESA
o Became endangered as a result of hunting and habitat loss.
o Removed because dangerous to humans and livestock
Restore to what?
o Past abundance (this is unknown)
o Also lack good estimates of present abundance
 Estimates include 1,200 in contiguous states, 32,000 in Alaska and 25,000 in Canada
o Based on Lewis and Clarks records (and a number of assumptions)
 The # of grizzly bears in 1805 in the US was 12,000
o Another approach is to ask what the min viable pop is.
The American Bison
Brought close to extinction for 2 reasons
o Hunted to make coats that were fashionable in Europe.
o Killed as part of a warfare against the Plains peoples.
Bison have recovered
o Profitable for ranchers
o Currently 200,000- 300,000 Bison
Estimates of original herds range for 10s of millions to > 50 million
o After Civil War protest over the slaughter
15 years later only 1000+/- remained
Improved Approaches to Wildlife Management
Four principles of wildlife conservation
o A safety factor in terms of population size, to allow for limitations of knowledge and the
imperfections of procedures.
o Concern w/ the entire community of organisms and all the renewable resources.
o Maintenance of the ecosystem of which the wildlife are a part.
o Continual monitoring, analysis, and assessment.
Principles broaden the scope from a narrow focus on a single species to inclusion of the ecological
community and ecosystem.
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Time Series and Historical Range of Variation
Time serieso set of estimates over a # of years.
Historical range variationo the known range of abundance of a population of species over some past time interval
o E.g. American whooping crane
Age Structure as Useful Information
An additional key to successful wildlife management.
E.g. salmon from the Columbia River, WA
o Shift in catch towards younger ages, along with an overall decline in catch, suggests that the
fish were being exploited to a point at which they were not reaching older ages.
o Early sign of overexploitation
Harvests as an Estimate of Numbers
Another method of estimating animal populations is to use the # harvested.
Previous animal abundance can also be estimated by
o Catch per unit effort
 Assumes same effort by all per unit time (same tech)
 So if you know the total time spent in hunting and catch per unit effort, you can
estimate total pop
o E.g. bowhead whale
Fisheries
Fish are an important food source
o 16% of the world’s protein
Continental shelves provide 90% of fish harvest
o Areas of high algae production to support food chain
o Upwelling
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The world’s fish harvest has increased greatly since the middle of the 20 th century
o Increase in # of boats
o Improvements in technology
o Increases in aquaculture production
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The Decline of Fish Populations
Evidence that fish populations were declining came from the catch per unit effort.
o Suggests fishing depletes fish quickly
o About 80% decline in 15 years
Commercial fisheries are mining a resource not sustaining it.
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Chesapeake Bay
o Famous for oysters and crabs
o Breeding and spawning ground for many commercially valuable species
o Food webs very complex
o Also influenced by runoff, introductions, development, alteration in salinity
Crisis has arisen for one of the living resources most subjected to science-based management.
o Management based on logistic growth curve
o Fisheries subjected to the “tragedy of the commons”
Fishing gear can be destructive to habitat.
o Ground-trawling equipment destroys the ocean floor
o Long-line fishing kills sea turtles and other non-target surface animals
o Large tuna nets have killed dolphins.
Can Fishing Ever be Sustainable?
Few wild biological resources can sustain a harvest at a level that meets even low requirements for a
growing business.
We can turn to farming fish (aquaculture)
o Important food source in China, growing worldwide
o Can create environmental problems
 E.g. Atlantic salmon fisheries cause water pollution and loss of genetic diversity
The Current Status of Endangered Species
The # of species listed as threatened or endangered increasing
IUCN maintains a list known as the Red List
o 20% of all know mammals at risk
o 31% of amphibians
o 3% of fish
o 12.5% of plants recently extinct or endangered
The term endangered species as defined by the ESA
o “Any species which is in danger of extinction throughout all or a significant portion of its
range…”
o With the exception of insect pests
The term threatened species
o “Means any species which is likely to become an endangered species w/in the foreseeable
future throughout all or a significant portion of its range.”
How a Species Becomes Endangered and Extinct
Local extinction
o Occurs when a species disappears from a part of its range but persist elsewhere.
Global extinction
o Means a species can no longer be found anywhere
Rate of extinctions has varied over geologic time
o From 580 million years ago until industrial revolution about one species per year
o Rate of evolution of new species =or > the rate of extinction
o Average longevity of a species 10 million years
Other periods of “punctuated extinctions”
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How People Cause Extinctions and Affect Biological Diversity
By hunting or harvesting.
By disrupting or eliminating habitats.
By introducing exotic species.
By creating pollution.
The IUCN estimates 75% of the extinction of birds and mammals since 1600 have been caused by
humans.
o Current extinction rate estimated to be 1,000 times greater than extinction rate in Pleistocene
Good News
Species whose status has improved
o Elephant seal
o Sea otter
o Many bird species effects by DDT, including bald eagle, brown pelican, white pelican, osprey
and peregrine falcon.
o Blue whale
o Gray whale
Can a Species be too Abundant?
Sea lions now number 50,000 and have become a problem in S.F. and S.B. Harbors
Mountain lions in California
o Both mountain lion and human population growing
o People building in lion habitat
o Attacks more common
The Kirtland’s Warbler and Environmental Change
Many species are adapted to natural environmental change.
o If change eliminated the species can become endangered
Kirkland’s warbler in Michigan
o From 1951-1971 found to be declining
o Nest in jack-pine woodlands that are between 6-12 years old
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Jack pine adapted to fire
o Cones open only after they are heated
o Trees intolerant of shade
o Abundance of dead branches
Kirkland’s warbler requires change at short intervals
o Fire approximately every 20-30 years
Fire suppression became the practice in 1927 and area replaced with economically useful species.
Now the Recovery Plan calls for prescribed burns
Ecological Islands and Endangered Species
An ecological island
o an area that is biologically isolated, so a species living there cannot mix w/ any other population
of the same species.
 Mountain tops
 Ponds
 Real geographic islands
Almost every park is a biological island.
How large must an ecological island be to ensure survival of a species?
o Depends on species requirements
Using Spatial Relationships to Conserve Endangered Species
Red-cockaded woodpecker
o An endangered species
o Nests in old dead or dying pines
o Feeds on pine bark beetle which hare a pest to the tree
A new approach to conservation
o Overlay a map of one’s habitat requirements over a map of the other’s
o Co-occurrence can be compared and allow maintenance of all three specie