Effects of in situ target spatial distributions on acoustic density estimates

One goal of acoustic-based abundance estimates is to accurately preserve spatial distributions of organism density and size within survey data. We simulated spatially random and spatially-autocorrelated fish density and cr 0, distributions to quantify variance in density, abundance. and backscattering cross-sectional a rea estimates, and to examine the sensitivity of abundance estimates to organism spatial distributions and methods of estimating acoustic size. Our results show that it is difficult to simul taneously estimate fish density and maintain accurate crbs· frequency distributions. Among our acoustic backscatter estimation methods. a weighted-mean from a local search window provided optimal estimates of density, abundance and crbs· Other methods tended to bias either crh, or density estimates. This analysis identifies the relative importance of variance sources when estimating organism density using spatial ly-i ndexed acoustic data.