Schooling Behaviour of Sardine<i>Sardinops Sagax</i>in False Bay, South Africa

Abstract

The schooling behaviour of sardine Sardinops sagax in False Bay on the south coast of South Africa was studied in October 1995 using high-resolution sonar and a hull-mounted, echo-integration unit. School formation and disintegration were studied, and school shape, packing density, swimming behaviour and inter- and intra-school event rates were quantified. Mean fish density was 29.5 fish m−3 (SD 46 fish m−3), but it varied between schools by a factor of about 100 (from 2 to 233 fish m−3). Tracked schools moved at average speeds of 0.67–1.59 m s−3. Schools changed shape on average every 2.08 minutes, and underwent either splits or merges with other schools on average every 5 minutes. Relationships between the geometric dimensions and biomass of the schools were established.