Relationships between the geometric dimensions and biomass of schools

Abstract

Acoustic measurements of the geometric dimensions and packing density of herring, sprat and saithe schools have been conducted by multi-beam sonars and echo integrator systems. Relationships between the reflected echo energy, the estimated school biomass and the school dimensions were established. The relationships seems quite similar for the three species and rather independent of the size of the fish. Seasonal and regional differences in schooling behaviour of herring were detected. School dimension-to-school biomass conversion may be a useful method for abundance estimation of pelagic species, and also for biomass measurements in capture situations.