An alternative echo-integrating method

An alternative method of estimating the number of individuals in marine populations by echo integration is presented. The method was published almost two decades ago by the same author and here it is reviewed and developed. The method is based on just two defined concepts, the Echo Abundance and the mean Echo-Value Constant, respectively. The ratio of these quantities is equal to the number of scattering individuals within a covered area. As the Echo Abundance is estimated by interpolating echo-integrator values over selected areas, the mean Echo-Value Constant can be estimated from representative resolved echoes and their detection angles from individuals in the population, as obtained by the split-beam echosounder system. Two types of estimators for the mean Echo-Value Constant are given and discussed theoretically with respect to their properties. The approach is described and discussed in relation to the conventional theory of abundance estimation by echo integration.