Accuracy and Precision: Implications of Sample Design on Abundance Estimates

There is a greater ability to control the size of the area sampled in aquatic environments than in most terrestrial environments.  Increasing the sampled unit area should reduce the number of sites with zero catch.  Inversely, more sample units yield greater statistical power.  Thus, a trade-off exists with sampling limitations between zero-inflated data and statistical power.  We generated a computer-simulated environment to test the role of number of samples, sample unit area, number of organisms, and the home range size of the organism in the estimation of population sizes using N-mixture models.  Many sample units of small area provided estimates that were consistently closer to true abundance than sample scenarios with few sample units of large area.  However, sample scenarios with few sample units of large area provided more precise abundance estimates than abundance estimates derived from sample scenarios with many sample units of small area.  It is important to consider accuracy and precision of abundance estimates during the sample design process with study goals and objectives fully recognized, although and with consequence, consideration of accuracy and precision of abundance estimates is often an afterthought that occurs during the data analysis process.