Q5s

Question 1

What is depletion sampling.

Answer 1

Used to determine the size of a population of mobile organisms within a small contained area.
Population is sampled repeatedly over a short space of time and sampled individuals are removed from the population.
Population size and CPUE will also decrease.
Applied to estimate size of fish population in small streams or ponds

Question 2

What is depletion curve

Answer 2

Plot CPUE against prior cumulative catch.

Question 3

Assumptions of depletion method of sampling

Answer 3

Population is closed
All individuals equally likely to be caught
Vulnerability to being captured stays constant
Sampling effort & conditions that could affect sampling remain constat during the sampling periof

Question 4

Préservation of macrobenthos

Answer 4

Most common fixing & preservative reagent is formaldehyde
Sold as 40% solution mixed with water known as formalin
-10% formalin
-4% formaldehyde
After initial fixation of tissue samples may be transferred into 70% ethanol

Question 5

Stratified sampling

Answer 5

A method of sampling involving the division of a population into smaller sun groups known as strata.
DIAGRAM

Question 6

Pseudoreplication

Answer 6

When replicate measurements are not fully independent of each other.
In experiment to test the fecundity in fish a polluted river and I polluted river was sampled once per week for 5 weeks during reproductive season.

Egg counts made on 100 female fish from each river on each sampling occasion.
To avoid pseudoreplication, more samples should be taken from more river sights.

Question 7

Why do some experiments need Positive & negative controls in experimental design.

Answer 7

Many exps require a control group which is as similar as possible to the treatment group, except for the treatment that is being applied.

Question 8

Example of negative control in experiment

Answer 8

Control group is not being manipulated
Exp: test effect of gum feed on hen shell thickness.
Control: hens fed normal feed as a negative control.

Question 9

Example of positive control in experiment

Answer 9

Control group manipulated in different way to treatment group.
Exp: grow bacteria on agar plate w/ antibiotic
Control: grow bacteria known to be resistant to antibiotic on plate.
If bacteria doesn’t grow -> problem with experiment set up.