Factors Influencing the Recruitment of Juvenile Fishes into the Mhlanga Estuary |
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| Authors: | A KWhitfield |
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| Institution: | Zoology Department, University of NataI, P.O. Box 375, Pietermaritzburg 3200 |
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| Abstract: | The migration of juvenile fishes (<5 cm) into the temporarily open Mhlanga estuary was monitored to determine the effects of different opening periods on immigration. The estuary opened at the end of January 1978 following a nine month closed phase. Only two marine species were recorded entering the estuary in February, compared to 11 species in November 1978. The estuary was closed between April and September. The large November recruitment may be attributed to the abundance of juvenile fishes in the sea adjacent to the estuary, whereas by February very few juveniles were present in Natal inshore waters. Estuarine and freshwater fish species were found to breed inside the estuary during the closed phase when environmental conditions were relatively stable. Mechanisms employed by these species to prevent eggs and larvae from being swept out to sea are discussed, as are strategies used by marine species to ensure recruitment during the very short open phase of the estuary. |
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