Using fish assemblages to understand environmental connectivity and usage. A contribution to the conservation of the Yucatan Wetland

Abstract

The Yucatan tidal wetland (YTW), located in the southeastern portion of the Gulf of Mexico is an extensive, heterogeneous, seasonally flooded area with a high diversity and richness, but urbanization is changing the ecosystem and, therefore, could change the functions it provides. Two important functions of the wetlands have been highlighted, its function as a nursery and the transfer of biomass to other ecosystems. To corroborate those functions, the percentage of juveniles and the links of the fish assemblage with other ecosystems need to be registered. In the present study, the fish assemblage of the YTW was analyzed to determine: (1) zonation; (2) assemblage and trophic structure; (3) environmental constraints on the fish assemblage, and (4) usage and connectivity of the ecosystem. Fifty-one stations were analyzed and segregated into three zones: Z1, the coastline, characterized by oxygenated and high salinity waters, and the highest fish richness and trophic diversity. Its fish assemblage is constituted by species associated with marine (31%), brackish (30%), reef (22%), and freshwater (17%) ecosystems, with 50% of the population registered as juveniles and 33% in the first-maturity size. Z2, the brackish environment, presents average fish richness and trophic diversity and physicochemical variation, its fish assemblage is constituted by species associated to freshwater (44%), brackish (34%), marine (15%), and reef (7%) ecosystems, with 43% of the population registered in first-maturity size and 33% in juveniles sizes. Z3, the freshwater environment, characterized by low oxygen levels and salinity, low fish richness and trophic diversity and the highest biomass. Its fish assemblage is constituted by species associated with freshwater (65%), brackish (34.5%), and marine (0.5%) ecosystems, with 80% of the population registered in adult sizes. The nursery, refuge, and feeding ground functions of the YTW and the transfer of biomass, via individuals, to other ecosystems were corroborated. It can be concluded that the YTW presents an intricate trophic and functional relationship among zones and ecosystems surrounding it; thus, the detrimental impacts in the YTW will produce negative effects in the near aquatic ecosystems. Therefore, it is of priority importance to ensure that the urban development plans of the YTW ensure the connection between zones, the clean input of freshwater, and the natural flow between the sea and the YTW.