Schooling behaviour of sardine Sardinops sagax in False Bay, South Africa

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.