The use of an adaptive acoustic-survey design to estimate the abundance of highly skewed fish populations

Abstract

Abstract Harbitz, A., Ona, E., and Pennington, M. 2009. The use of an adaptive acoustic-survey design to estimate the abundance of highly skewed fish populations. – ICES Journal of Marine Science, 66: 1349–1354. The uncertainty (relative root-mean-square error) of abundance estimates based on a simple and easily implemented adaptive design for an acoustic survey is examined. The study is limited to surveys with parallel transects and independent observations with extremely skewed distributions. The adaptive approach defines a stratum for each conventional observation and how to take additional observations in that stratum when the acoustic density exceeds a predetermined threshold. The cost (sailing distance) of each added observation is about three times that of a conventional observation. This method was demonstrated using high-resolution transect data from a herring (Clupea harengus) acoustic survey conducted in 2006 off the north coast of Norway. The primary sampling unit for this winter survey was 5 nautical miles, and the usual distance between transects was 20 nautical miles. The results indicate that an adaptive survey design would substantially reduce the root-mean-square error of the abundance estimates compared with that of the conventional survey design.