1. G.5 Population Ecology
Van Roekel
IB BIO II
4/29/15

2. Assessment Statements
G.5.1 Distinguish between r-strategies and k-strategies
G.5.2 Discuss the environmental strategies that favor either r-strategies or k- strategies
G.5.3 Describe 1 technique used to estimate population size of an animal species based on mark-release-recapture method
G.5.4 Describe the methods used to estimate the size of commercial fish stocks
G.5.5 Outline the concept of maximum sustainable yield in the conservation of fish stock
G.5.6 Discuss international measures that would promote conservation of fish

3. R-Strategies vs. K-strategies
Continuum of strategies for caring for species
R-Strategy – strategy of disposable offspring
Produce multiple (up to thousands) of eggs/offspring that need little care from parents
Insects, Zebra Muscles, etc…
K-Strategy – strategy of nurturing offspring
Organisms have fewer offspring and spend considerable time and energy caring for them
Elephants, Zebras, Humans
Some organisms fall in between the two extremes
Ducks – lay multiple eggs because some may be eaten by predators, but ducklings need parental care.

4. R-Strategies vs. K-strategies
Characteristic
R-strategy
K-Strategy
Life Span
Short
Long
Number of Offspring
Many
Few
Growth
Quickly
Slowly
Onset of Maturity
Early
Late – after a long period of parental care
Body Size
Typically Small
Typically Larger
Reproduction
Once during lifetime
More than once during lifetime
Parental Care
None
Very likely and in depth
Environment
Unstable
Stable

7. Environmental Conditions that favor R-strategy
Unstable environments favor organisms that produce many offspring as quickly as possible.
Many offspring can be lost to unpredictable forces
Few that remain can reproduce and carry on genes or species
Ecological disruptions favor r-strategists
Able to grow quickly and take advantage of disruption before other organisms
Plants on foredune, where shifting sand and salt spray cause unstable conditions use this strategy.
Weeds produce thousands of seeds and grow quickly to take advantage of unstable environments

8. Environmental Conditions that favor K-strategy
Stable environments favor organisms that care and nurture their offspring
Area is more predictable and less susceptible to unknown forces
More effective to invest resources in becoming more competitive
Mature dune is not susceptible to wind or salt spray and the soil has been built up over hundreds of years. Organisms invest more in being competitive in a stable environment to make the most of the available resources.

9. Capture-Mark-Recapture
Sampling technique that enables one to estimate the number of animals in an ecosystem
Catch some organisms within a population and mark them (tags, chips, etc.)
Release marked animals back into environment and allow them to interact w/ population
Recapture a second group of individuals from the same population, some will be marked, others will be unmarked
Use the proportion of marked to unmarked individuals to estimate size of population
The proportion of marked to unmarked individuals in second capture is equal to the proportion of originally marked individuals to whole population

11. Capture-Mark-Recapture formula (Lincoln Index)
Population Size (N) = (n1 x n2) / n3
Population Size = total population
n1= number marked in first sample
n2= total caught in second sample
n3= number marked in second sample

12. Example
Suppose you capture and mark 100 grasshoppers and release them back into the wild. Then you capture another 100 grasshoppers and 10 of them are marked. What is the estimated population size of grasshoppers?
N = (100 x 10) / 100
N = 1000 grasshoppers

13. Use of Lincoln Index Two Primary uses
Can be used to compare populations of different species at one time
Chart the change in a species of population over time

15. Limitations to Capture-Mark-Recapture
Take caution to avoid the following:
Marks may injure animals
Marks may make them more visible to predators
Marks may make them unattractive to opposite sex
Method assumes population is closed (meaning no immigration/emigration. This rarely happens)

16. Estimating Size of commercial fish stocks
For the North Atlantic Ocean, Scientists from ICES (International Council for Exploration of the Sea) are sampling fish, measuring:
Type of fish,
Age,
Length,
Breeding Conditions
Use information to predict size of commercial fishing stock

17. Estimating Size of commercial fish stocks – Gathering Information
From Fishers (collect info onboard fishing vessels)
Number and kinds of fish thrown back
Tagging and releasing fish
Questioning fishers about perception of catch
Reviewing logbook data, which gives catch-per-unit-effort (increased effort for same catch indicates a decrease in population numbers)

18. Estimating Size of commercial fish stocks – Gathering Information
From Research Vessels
Cast nets in hundreds of selected location (trawling) for samples
Echo sounders to locate schools of fish in order to determine biomass and numbers of fish populations
Calculating age by counting number of otoliths (ear bones), or measuring the rings of fish scales
Too few young fish indicates lack of spawning
Too few old fish indicates over-fishing
Using coded wire tags (capture-mark-recapture method) to estimate total population

19. Estimating Size of commercial fish stocks – Analyzing Date
Mathematical models are used to turn all this data into usable data that can be used by the fishing industry and governments to regulate and plan for the future of fish in the oceans and lakes.

20. Maximum Sustainable Yield
Maximum Sustainable Yield (MSY) is the highest proportion of fish that can be removed from the total population without jeopardizing the maximum yield in the future
If fish stock is too small, there are not enough adult fish to produce sufficient young fish.
Fishing from a stock that is too small leads to over-fishing
If fish stock is too large, the annual reproductive rates may be low because of increased competition for food.

22. International measures to promote conservation of fish
In 2006, it was found that all seafood species had declined by 29% in the last three years
If the trend continues, by 2048 there would be no more commercial fishing
The following would promote the conservation of fish and reverse the current decline

23. International measures to promote conservation of fish
Regulate bottom trawling of the ocean (strip mining of ocean floor)
Rebuild depleted fish populations as quickly as possible and pay attention to MSY
Eliminate wasteful and damaging fishing practices (trapping unwanted animals in fishing nets reduces biodiversity)
Enact strong national fishing quota programs according to MSY
Establish programs to develop less damaging fishing gear (shrimp nets that have trap doors to release unwanted animals)
Provide funds to improve scientific research which counts fish populations and monitors catch
Encourage relationships between fishers and scientists
Establish marine reserves and no-catch zones to improve biodiversity and increase fish stock in protected areas

24. International measures to promote conservation of fish-difficulties
Enforcement and monitoring such regulations is difficult
International trust does not exist to keep these practices functioning
Prices for fish around the world has risen
Encourages fishing for scarcer fish
Catching the big fish eliminates the specimens which lay the most eggs
Difficult to tell fishers to limit their catch when many are going out of business.