The fish fauna of river basins at Discovery Coast, extreme southern Bahia State, Brazil

Abstract

Hydrological richness of coastal river basins at Discovery Coast contrasts with the poorly known freshwater fish fauna. For recognition of local fish fauna, twenty nine localities were evaluated in rivers and rivulets. 35 species, including historical and recent records, belonging to 17 families in 8 orders were found. Most of the fish caught belong to the Ostariophysi, with 23 species captured, followed by the Perciformes (5 species), Anguilliformes and Cyprinodontiformes (2 species each), and also Gasterosteiformes and Synbranchiformes (1species each). The only exotic species recognized to the river basins was Oreochromis niloticus. Distributional evaluation of species on coastal river basins at Discovery Coast was provided through PAE methodology based on quadracts. The four irregular quadracts were drawn for the distinct ecorregions: Cumuruxatiba, Cahy, Corumbau and Caraíva. For evaluation of endemisms a matrix was built, through softwares Winclada and NONA, with the distributional information of 30 local freshwater fish species. Based on the analyzed data, a unique parcimonious tree was found, avoiding the use of a consensus cladogram. The area cladogram found contained 36 steps, consistency index (CI) 83 and retention index (RI) 62. The distributional data analysis of species defined the Caraíva river basin as a basal area relative to the remaining ecorregions, that together form a monophyletic clade. The areas of Cumuruxatiba and Cahy were considered as closely related, and the sister group to the Corumbau ecorregion. A high regional endemism was recognized for the study area. Endangered species, such as Mimagoniates sylvicola and Rachoviscus graciliceps were recorded for the basin, as well as species characteristic of vegetated environments, as Acentronichthys leptos and Aspidoras virgulatus.