Marine Sampling Methods and Techniques

Sampling

Counting animals/plants.

Abundance

Total number.

Density

Total number in set area.

Mark-recapture Survey

A method involving capturing, marking, releasing, and recapturing individuals to estimate population size.

Assumptions of Mark-recapture Method

Closed, stable population, random mixing of individuals, constant capture rate, marks stay and do not affect individuals, need to recapture high number of individuals.

M

Number of marked animals released.

S

Total animals caught second time.

R

Number marked animals recaught.

N

Estimated population size.

Distance Sampling

A method involving placing equally spaced transects, detecting individuals, measuring distances, and calculating abundance.

Assumptions of Distance Sampling

All animals are detected on the transect, detection probability declines away from transect, objects are detected at their initial location, accurate measure of distance, transects randomly placed in habitat.

Area under rectangle

Max. frequency x max. distance.

Area under curve

Width of distances x height of curve.

All animals detected

Area under rectangle = 9 x 4 = 36.

Actual individuals detected

Area under curve = 0.5 x (10+8+6+5+3+2+1+0.5) = 31.25.

Pa

How likely you are to find the birds.

Mark-recapture formula