483
Caeté Estuary, and the seasonal salinity fluctuation is the main factor structuring the
fish assemblages in the system (Barletta et al. 2005).
Most species captured by the artisanal and subsistence fisheries in this estuary
require estuarine conditions to complete their life cycle (Barletta et al. 2005). During
the dry season, hydrological conditions create a defined salinity gradient, and therefore estuarine and marine fish species fall along a horizontal gradient according to
their capacity to tolerate salinity variations (Figs. 16.1 and 16.2). During the rainy
season, freshwater runoff dramatically increases seaward, and salinity decreases in
the upper portion of the estuary, which is then favourable for euryhaline freshwater
fish species (Figs. 16.1 and 16.2) (Barletta et al. 2005).
Fig. 16.2 Patterns of average monthly rainfall and average water salinity in the Caeté Estuary. Red
dashed boxes ( ) represents the rainy season
16 Estuarine Ecoclines and the Associated Fauna: Ecological Information as the Basis…