This work investigates the spatial distribution and abundance of the ichthyofauna along the saline gradient of the Lagoa do Peixe National Park in southern Brazil. This system is an intermittent lagoon connected to the ocean by a single opening, which allows the mixing of salt and fresh water into the lagoon. As a consequence the ichthyofauna was composed of limnetic, marine and estuarine-related species. The unusual location of the opening of the estuary, near the center of the system, lead to an uncommon spatial distribution of fish fauna, which shows pre-limnetic characteristics at both the north and south zones and estuarine-marine affinities in the middle of the Lagoon. Based on fish species composition the lagoon could be separated into four sub-systems: pre-limnetic shallow-waters, pre-limnetic deep-waters, estuarine shallow-waters and estuarine deep-waters. The Fish composition was characterized by a gradual replacement of marine estuarine related species by fresh water species followed by changes in the dominance of selected species. At the shallow waters the sub-systems also show a pronounced reduction in fish abundance from estuarine to fresh waters.
Estuary; ichthyofauna; conservation unit
