Searching for species identifiers in multifrequency target strength variability

Abstract

Acoustic research has shown that the species of some schooling fish can be assigned based solely on measurement parameters from acoustic returns. For single targets, this process is complicated by the high variability of in-situ target strength (TS) measurements. Attempts at speciation based on the patterns of TS variability were confounded by interactions between acoustic frequency and fish directivity. Initial attempts at defining speciation parameters based on multifrequency target strength measures look promising. This paper reports on the results of simultaneously measuring the in-situ target strength of fish at 38-, 120-, and 420-kHz acoustic frequencies, and proposes the definition of several speciation parameters.