An initial simple model of the revised stock structure hypothesis for South African sardine

Four alternative simple models of a revised stock structure hypothesis for South African sardine are considered. These models exclude any commercial catch as an initial step. This hypothesis assumes Cool Temperate Sardine (CTS) are found off the west coast only, with some CTS moving at age 1 to the east coast (outside the modelled area). Warm Temperate Sardine (WTS) are found off the west and south coasts, with passive transport of some WTS spawning products from the south coast to the west coast and active movement of WTS from the west coast back to their preferred habitat on the south coast. The model provides a reasonable fit to the data with west to south movement and west coast recruitment being estimated at presumed realistic levels if the proportion of WTS recruits which are passively transported from the south to the west coasts to vary annually.