Exam 2- Conservation Biology

What is genetic drift?

Random fluctuation of gene frequencies over time due to chance.

Why does genetic drift have stronger effects in some populations?

Because it is stronger in small populations.

What is a genetic bottleneck?

A sharp reduction in population size that reduces genetic diversity.

What is the founder effect?

When a new population is established with gene frequencies different from the original population.

What is inbreeding?

Mating between closely related individuals.

What is inbreeding depression?

Reduction in fitness due to inbreeding.

Name major problems small populations face.

Environmental stochasticity, demographic stochasticity, Allee effects, inbreeding depression, genetic drift.

What is environmental stochasticity?

Random environmental fluctuations that affect populations.

What is demographic stochasticity?

Random variation in birth and death rates.

What are Allee effects?

Reduced population growth at low population sizes.

Why are small populations more vulnerable to stochastic effects?

Random effects have a larger proportional impact in small populations.

What is the extinction vortex?

Downward spiral where multiple factors reinforce each other, driving a population to extinction.

Name factors contributing to the extinction vortex.

Habitat loss, overexploitation, invasive species, stochasticity, Allee effects.

Why is the extinction vortex dangerous?

Populations may not recover naturally below critical thresholds.

What happened to the American heath hen by 1870?

Mainland populations went extinct due to hunting; ~300 left on Martha’s Vineyard.

What reduced the population to 150 by 1890?

Cats and poaching.

What caused further decline to 70 by 1900?

Inbreeding problems.

What events caused decline from 1916–1920 despite a reserve?

Forest fire, harsh winters, disease, hawk predation.

How many birds remained by 1927?

13 (11 males, 2 females).

Who was Ben?

The last male heath hen.

When did Ben die?

March 11, 1932.

Why might habitat restoration alone fail to recover populations?

Because populations can fall into the extinction vortex.

What is the species name of the Hainan gibbon?

Nomascus hainanus.

How did the population change from 2003 to 2025?

Increased from ~13 to 42 individuals.

Why was there no inbreeding depression in such a small population?

A bottleneck ~20,000 years ago purged deleterious alleles.

What is genetic purging?

Removal of harmful alleles through selection in inbred populations.

Why is genetic diversity high in Hainan gibbons?

Two distinct lineages began interbreeding.

Why do cheetahs have low genetic variation?

A severe bottleneck a few thousand years ago.

What does this show about inbreeding?

Long-term inbreeding can purge harmful alleles.

What is MVP?

Smallest population size with a high probability of persistence.

What was the original MVP definition?

99% chance of survival for 1,000 years (Schaffer 1981).

What is the modern MVP standard?

95% chance over 50–100 years.

Is there a universal MVP number?

No; population success depends on context.

Give examples where size alone didn’t predict success.

Marbled murrelets (~10,000 declining) vs. Puerto Rican parrots (<1,000 thriving).

What is the scientific name of the black-footed ferret?

Mustela nigripes.

What do they eat?

Prairie dogs (obligate predators).

What caused ferret declines?

Agriculture, grazing, poisoning, disease (Sylvatic plague).

How many ferrets were captured for breeding?

18 individuals (7 founders).

How can inbreeding be minimized in captive breeding?

Track genetic lineages and ensure all individuals reproduce.

How many ferrets have been bred since 1986?

Over 11,000.

How many have been reintroduced?

Over 4,500.

What is genetic rescue?

Increasing genetic diversity to prevent extinction.

How was cloning used in ferret conservation?

Clones created from frozen 1988 samples; tripled genetic variation.

What is overexploitation?

Harvesting faster than a resource can replenish.

Who believed fisheries were inexhaustible?

Thomas Huxley (1883).

Why was that incorrect?

Industrial fishing drastically increased efficiency.

Which growth model is most relevant to fisheries?

Logistic growth.

When does population grow fastest?

At intermediate sizes.

What is Maximum Sustainable Yield (MSY)?

Largest harvest that can be sustained indefinitely; harvest = recruitment.

What happens if harvest exceeds growth?

Population declines toward extinction.

What are the risks of MSY?

Requires precise estimates; environmental variability makes it risky.

Name safer harvesting strategies.

Conservative fixed quota, proportional harvest, fixed escape, marine protected areas (MPAs).

What is aquaculture?

Farming aquatic organisms; market value $204 billion.

Why do fisheries collapse even with MSY theory?

Uncertainty, environmental variability, poor estimates, tragedy of the commons.

If a population = 500 and growth = 100, what is the population next year without harvest?

600.

If population = 600, growth = 90, harvest = 60, what is next year’s population?

630.

What stable population results from harvesting 60/year?

800 (growth = harvest).

What is fixed quota harvesting?

Removing a constant number each year.

What is the risk of fixed quota harvesting?

Can drive population to extinction if too high.

What happens to population size with higher harvest rates?

Lower stable population.

What happens if harvest exceeds growth?

Population declines to extinction.

Why is MSY risky in real-world fisheries?

Requires precise estimates; small errors can collapse populations.

Give a real-world example where quotas caused collapse.

Whale harvesting.

Why is fisheries management difficult?

Fish are hard to count and environments vary.

What happens if environment worsens but harvest remains constant?

Population declines.

What happens if environment improves after overharvesting?

Previous harvest may exceed sustainable levels, causing decline.

Key quote about counting fish?

“Counting fish is like counting trees except fish are invisible and move.”

What is the tragedy of the commons?

Individuals benefit from exploiting a shared resource, but costs are shared, leading to overuse.

Give examples of the tragedy of the commons.

Fishing, grazing, pollution.

What is a subsistence fishery?

Fishing for personal or family consumption; low-tech, small-scale, not sold.

What percentage of global catch do small-scale commercial fisheries produce?

40%.

What percentage of the workforce do they employ?

90%.

Key characteristics of small-scale fisheries?

Low capital, high labor, small boats, nearshore, short trips.

What are large-scale fisheries also called?

Industrial fisheries.

What percentage of global fishing effort is trawling?

53%.

Key characteristics of large-scale fisheries?

High capital, mechanized, large vessels (>24 m), offshore, global markets.

What is a recreational fishery?

Fishing for sport or leisure; significant economic and cultural impact.

How has technology impacted fishing?

Increased efficiency and scale dramatically.

What does vessel tracking (AIS) show?

Global fishing activity distribution.

What happens at low fishing pressure economically?

High profits.

What happens as more fishers join?

Increased fishing pressure and declining fish populations.

When does fishing stop in an unregulated system?

When profits disappear due to overfishing.

Why is regulation necessary?

To prevent resource collapse.

How is profit calculated?

Benefits – costs.

Why is MSY not equal to maximum profit?

Costs affect profitability.

How can profits increase without overharvesting?

By reducing costs (e.g., fuel, gear, labor).

What is rational overfishing?

Harvesting unsustainably for short-term profit.

Why might fishers overfish intentionally?

To maximize profit before collapse.

What happens after collapse in rational overfishing?

Fishers move to new populations.

How can cooperation improve fisheries?

Shares benefits, reduces competition, prevents overfishing.

What is a fishing cooperative?

A group that shares quotas and manages resources.

What are TURFs?

Territorial Use Rights for Fishing.

Benefits of TURFs?

Incentivize conservation and sustainability.

Give an example of TURFs or cooperatives in action.

Baja California.

What is aquaculture?

Farming aquatic organisms.

Market value of aquaculture?

$204 billion.

Why is aquaculture important?

May replace wild fisheries, reduce pressure on wild populations.

Why do fisheries collapse even with MSY theory?

Uncertainty, environmental variability, poor estimates, tragedy of the commons.

What is the safest harvesting strategy overall?

Conservative or adaptive strategies, not maximum exploitation.

Why is regulation necessary?

Prevent tragedy of the commons and resource collapse.