Monitoring Populations

Question 1

What are indicator species?

Answer 1

• Susceptible and favoured indicator species can be used to monitor an ecosystem; their presence, absence or abundance can give information on environmental qualities, e.g. presence of a pollutant.
• Absence or reduced population indicates a species is susceptible to some factor in the environment.
• Abundance or increased population indicates it is favoured by the conditions.

Question 2

Describe mark and recapture.

Answer 2

N = estimate of total population
M = no. captured, marked and released in first sample
C = no. captured in second sample
R = no. of marked recaptures in second sample

N = MC/R

Question 3

Describe marking.

Answer 3

• The method of marking and subsequent observations must minimise the impact on the study species.
• It should not interfere with the individual’s normal behaviour or make it more conspicuous to predators.
• However, it must be clear in order to permit subsequent observations.

Question 4

What are methods of marking?

Answer 4

• Banding
• Tagging
• Surgical implantation
• Painting
• Hair clipping

Question 5

What are the assumptions of mark and recpature?

Answer 5

• all individuals have an equal chance of capture
• that there is no immigration or emigration
• individuals that are marked and released can mix fully and randomly with the total population
• there is no birth or death