IN THE SOUTH-WEST INDIAN OCEAN* SUMMARYWaters of the southern African east coast are characterized by the Agulhas Current and related circulatory systems, a narrow continental shelf, the entry of many rivers into the sea and pronounced longshore sediment transport. An attempt is made to elucidate the response of marine life and in particular planktonic organisms, spiny lobsters, marine turtles, sharks, and estuarine and marine teleost fishes to this environmental regime. OPSOMMINGDie waters van die suidelike ooskus van Afrika word gekenmerk deur die Agulhasstroom en verwante patrone van watersirkulasie, 'n smal vastelandsplat, die invloei van ' n groot getal riviere en grootskaalse sedimentvervoer parallel met die kus. In hierdie referaat word gepoog om die reaksie van mariene organismes, veral plankton, krewe, seeskilpaaie, haaie, en estuariene-en mariene teleost visse tot hierdie omgewingsregime uiteen te sit.

The filtration rate of Perna perna (L.) at the approximate annual mean local water temperature (20 "C) is high, being 2.7 X I O -~ (shell length in mm)'-86 1 h-' or 8.85 (dry flesh weight in 1 h-'. It was found to be able to filter latex particles down to at least 0.46 pm in diameter, these being roughly the mean size of free coccoid bacteria in the study area. Its mean assimilation efficiency, determined by the Conover method, was 61 % on a natural diet of particles < 100 p m in diameter which had a mean organic content of 3.16 mg 1-'. The faeces production rate was also established and an energy budget for P. perna is discussed in the light of available data.

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Visual censusing methods were employed over 2 consecutive years to estimate density and biomass of the ichthyofauna on a rocky littoral reef. A total of 66 teleost and 2 elasmobranch species was recorded of which 10 accounted for over 98 % of the total mean dry biomass of 15.1 g m-'. The only truly resident species were Scartella cristata and Pictiblennius cornutus which together comprised more than two thirds of the total biomass. Besides the blennies. Sarpa salpa was most important in terms of mean biomass (1.1 g m-2) and Pornadasys olivaceum in terms of mean density (0.9 m-2) Carnivores far outnumbered both herbivores and omnivores but the latter predominated in terms of biomass. It is concluded that shallow reefs on the east coast of South Africa, such as the one studied, represent an important source of concentrated food production to inshore teleosts. Caloric values are given for 18 teleost species.