Influence of the Agulhas Current on the distribution of lanternfish larvae off the southeast coast of Africa

Abstract

Spatial and temporal distribution patterns of lanternfish larvae along the southeast coast of Africa were analysed in relation to oceanographic conditions. Investigations werebased on the plankton collections made during winter, spring and summer months of 1990–1991. The warm southward-flowing Agulhas Current is the dominant large-scale oceanographic feature in the area. The number of species of myctophid larvae collected per cruise ranged from 35 to 38. The most abundant species differed from one season to the other.Afew species showed marked seasonality in their occurrence, e.g. Scopelopsis multipunclatiis only appeared in winter and Hygophum hygomii showed the highest abundances in winter. The majority of species occurred in relatively low concentrations during all three periods. Relatively large concentrations of lanternfish larvae of most species sometimes occurred very close inshore (especially in the north of thestudy area) in water depths of 50–100 m. This was related to shoreward intrusions ofAgulhas Current surface water. Low numbers of larvae of few species appeared on the inshore shelf of the southern sector of the study area, where cold central Indian Ocean water is forced onto the shelf by kinematic upwelling.