Backscattering properties of southern Baltic herring

Jakub Idczak; Natalia Kniaź-Kubacka

Backscattering properties of southern Baltic herring

Abstract

Reliable TS(L) relationship is required to improve acoustic algorithms of abundance
estimation of Baltic herring. The relationships, empirically obtained in different parts of the
Baltic Sea, produce up to 8 dB – difference in the herring TS. In order to develop an accurate
TS(L) relationship, it is important to analyze factors controlling the TS variability. The
possible impact of the regional difference in the swimbladder morphometry, critical in the
backscattering by fish, should be considered. The paper is addressed to the numerical
analysis of the backscattering properties of the southern Baltic herring. The input
morphometric data for the modelling were obtained basing on the X-ray image collection of
the herring individuals caught in the Polish coastal zone (ICES Subdivision 26) in November
2011. The optimal methodology of the morphometry study, including the fish catch, transport,
storage and the X-ray analysis has been developed. The backscattering sensitivity to the fish
morphometry and the width of fish orientation distribution was shown.