Estuarine and mangrove systems and the nursery concept: which is which? The case of the Sine Saloum system (Senegal)

ISSN： 0923-4861

Source： Wetlands Ecology and Management, Vol.8, Iss.1, 2000-02, pp. : 37-51

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Abstract

The mangrove system of Sine Saloum in Senegal is characterized by the lack of permanent river flow, in the context of the Sahelian drought which began in the 70s. The main environmental consequence is that Sine Saloum has become a so called ‘reversed estuary’ with salinity increasing upstream and reaching 100‰ and more, with a mean salinity between 45–50‰. A three-year survey of the juvenile fish community was undertaken with the aim of verifying whether or not this environment is still suitable as a nursery area for exploited fish populations. The main sampling gear used were small fyke-nets in addition to gill nets and a limited rotenone sampling. One of the six mangrove stations included in the survey exhibited a relatively high species diversity. This station is the only one where salinity may reach levels as low as 25‰ at the end of the rainy season, although salinity is much higher in the upstream region near this station. Such a low salinity is likely due to an underground freshwater connection or underwater springs. These observations highlight the relative importance of estuaries and mangroves in the nursery function.