Diel horizontal migration of Mesopodopsis slabberi (Crustacea: Mysidacea) in Algoa Bay, southern Africa

Abstract

ABSTRACT. The mysid shrimp Mesopodopsis slabben (van Beneden), exhibited a die1 pattern of onshore-offshore movement off Sundays hver beach, South Africa. Shoreward migration at sunset resulted in the presence of relatively high numbers of mysids after dark behind the breaker line (ca 6 m water depth) compared to further offshore. At first light, M. slabberj migrated back to deeper water (> 15 m) where it remained during daylight. The nocturnal presence of mysids behind the breakers is interpreted as a response to increased concentrahon of phytoplankton, principally Anaulus australjs Drebes and Schulz, which outwelled from the inner surfzone through rip current activity. Consumption by M. slabberi was estimated to be 51 g C d-'. On an annual basis, this approximated to 70 % of total available carbon consumed by the nlacrofaunal trophic assemblage in the Sundays River surfzone.