Journal of Plankton Research Vol.16 no. 12 pp. 1759-1780, 1994 Influence of the Agulhas Current on the distribution of lanternfish larvae off the southeast coast of Africa M.P.Olivar and L.E.Beckley 1 Institute) de Ciencias del Mar, Paseo Joan de Borbo sin, CSIC, Barcleona 08039, Spain and ' Oceanographic Research Institute, PO Box 10712, Marine Parade, Durban 4056, South Africa Abstract. Spatial and temporal distribution patterns of lanternfish larvae along the southeast coast of Africa were analysed in relation to oceanographic conditions. Investigations were based 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. A few 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 the study area) in water depths of 50-100 m. This was related to shoreward intrusions of Agulhas 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. Introduction Plankton studies of the Agulhas Current region (De Decker, 1973), and especially those on ichthyoplankton, are scarce (Beckley, 1986; Beckley and Van Ballegoyen, 1992). No previous works deal with lanternfish larvae of the southwest Indian Ocean and the only previous reference relating to neighbour- ing areas is the work of Pertseva-Ostroumova (1974). The most extensive zoogeographic analysis of lanternfish fauna of the Agulhas Current region was made by Hulley (1984), based on collections of adults and some juveniles. Nafpaktitis and Nafpaktitis (1969) and Nafpaktitis (1978) also deal with Indian Ocean lanternfish, but cover an area further east (60-65°E). Hulley (1984) suggested 'that distributional ranges of the breeding populations should be thoroughly investigated before any attempt at pattern analysis'. There has not been information available on this subject since the work of Hulley (1984), therefore the present study on the spatial and temporal distribution patterns of lanternfish larvae in relation to oceanographic conditions of the area is the first information available on the spawning of these species. Lanternfishes are a diverse oceanic group of fishes with a large biomass (Nafpaktitis and Nafpaktitis, 1969; Paxton, 1972; Moser et al., 1984); their larvae represent a high proportion of the total larvae collected in oceanic plankton samples of any region of the world (Ahlstrom et al., 1976). Some species are endemic to specific regions, others occur in disjunct areas, whilst others are widespread over the world's oceans (Krefft, 1974). However, these wide distributions may be due to passive transport by ocean currents and it is © Oxford University Press 1759