A model for estimating distributions of fish school target strengths

Abstract

A model has been developed to estimate the distribution of fish school target strengths for any schooling species. The model has both biological and acoustic components. The biological component estimates distributions of school size and density for a given species. A discrete spectrum of nondimensionalized school densitites, developed by combining and synthesizing the results of experimental studies on intraschool spacing, is utilized to estimate school density distributions. Discrete spectra of school sizes based on empirical knowledge and assumptions of school growth and reduction are utilized to estimate school size distributions. The acoustic component combines estimates of target strengths of individual fish with numbers of fish insonified to calculate school target strengths at any aspect for a school of given size and density. Multiple scattering is neglected, but attenuation through the school is accounted for by the use of shadowing factors. Provision is made for schools which are not totally insonified due to limitations of sonar beamwidth or pulse length. Comparison to available experimental data indicates that the model produces a reasonable estimate of target strength distributions.A model has been developed to estimate the distribution of fish school target strengths for any schooling species. The model has both biological and acoustic components. The biological component estimates distributions of school size and density for a given species. A discrete spectrum of nondimensionalized school densitites, developed by combining and synthesizing the results of experimental studies on intraschool spacing, is utilized to estimate school density distributions. Discrete spectra of school sizes based on empirical knowledge and assumptions of school growth and reduction are utilized to estimate school size distributions. The acoustic component combines estimates of target strengths of individual fish with numbers of fish insonified to calculate school target strengths at any aspect for a school of given size and density. Multiple scattering is neglected, but attenuation through the school is accounted for by the use of shadowing factors. Provision is made for schools which are not totally in...