Episodic events: the effects of cyclonic flushing on the ichthyoplankton of St. Lucia estuary on the southeast coast of Africa
Martin, T.J.; Cyrus, D.P.; Forbes, A.T. (1992). Episodic events: the effects of cyclonic flushing on the ichthyoplankton of St. Lucia estuary on the southeast coast of Africa. Neth. J. Sea Res. 30: 273-278. https://dx.doi.org/10.1016/0077-7579(92)90065-M
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406
Also appears in:
Heip, C.H.R.; Nienhuis, P.H.; Pollen-Lindeboom, P.R. (Ed.) (1992). Proceedings of the 26th European Marine Biology Symposium: Biological Effects of Disturbances on Estuarine and Coastal Marine Environments, 17-21 September 1991, Yerseke, The Netherlands. Netherlands Journal of Sea Research, 30. Netherlands Institute for Sea Research: Texel. 299 pp., more
The St Lucia estuarine system is the largest of its kind in Africa. Torrential rains from Cyclone Domoina during late January 1984, followed two weeks later by Cyclone Imboa, caused extensive flooding of the St Lucia system reducing salinities from a maximum of S=60 to S=5 over a period of two weeks. The effects of this disturbance on the ichthyoplankton were monitored 3 km from the estuary mouth over the following ten months when physical conditions in the system began to stabilize. These data are compared with ichthyoplankton catch data collected at the same site immediately before the cyclones from March 1982 until January 1984. Results showed that flooding had relatively long-term effects on the distribution and numbers of some estuarine resident and marine migrant species which utilize the estuary as a nursery ground. The frequency of occurrence and proportional density of the estuarine resident Gilchristella aestuarius increased after the floods while that of Croilia mossambica and Gobius acutipennis decreased. No changes in the proportional densities of other estuarine resident species were noted. Increases were recorded in proportional densities of marine migrant species Elops machnata, Leiognathus equula, Johnius dussumierii and Pomadasys olivaceum, while proportional densities of Solea bleekeri and Rhabdosargus sarba decreased. The ecological significance of environmental disturbances in the St Lucia estuary by episodic flooding and its effect on the distribution and abundance of estuarine resident species and marine migrant species are discussed.
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