Random vs Systematic Sampling:
- Systematic Sampling: they used a grid of 64 equally spaced points, the location of initial point was randomly selected. basically, they divded the survey area into 64 equal boxes. They then randomly chose a point in one box, and then collected the sample at the same relative location in each of the 64 boxes. I think that this was continued (i.e. they generated another regular grid of 64 points) until they had 1000 points in total.
- Random: start with 64 stations, then add random stations and use an allgorithm to see how long it takes to travel from each station to the next one. They continued adding random stations until they reached a maximum time limit (making the number of sample locations variable).
They ran these two survey types on two different simulated oceans of fish. One ocean had high variability and low spatial autocorrelation (don't know what that is), and the other had low variability and high correlation. (each ocean had 1x10^7 fish).
The random sample did a better job estimating the population in the high variability ocean, but the systematic sample did a better job with low variability. Implies that sample method selection should correlate to spatial distribution of fish. ("Further investigation of a wider range of surfaces with different properties should help to refine the parameters that influence the point at which different survey strategies are more effcient estimators...")