Empirical acoustic TS - Length relationship for Torpedo Scad (Megalaspis cordyla)

Abstract

One of the main challenge in fish stock assessment with acoustic method is how to improve the accuracy of the estimated acoustic target strength (TS) of the fish under investigation. Various factors contribute to the bias in acoustic TS, namely the high diversity of fish species, body shape, orientation and size. It is therefore necessary to have a database of acoustics TS of fish on a particular species, size (length), and orientation as a reference to be used in grouping and in estimating the over all TS-length relationship of the species. In this paper we reported the result of in situ TS measurements of Torpedo Scad (Megalaspiscordyla). The TS data analysis is performed numerically through the best-fit technique to establish the relationship between length, object orientation, and TS. The TS-length relationship obtained for Torpedo Scad (Megalaspis cordyla) is TS = 20 log (FL)-53.68.This relationship could be used to eliminate bias in the fish stock assessment by acoustic method.