Abstract
ABSTRACT The ichthyofauna of the Río Acahuapa was analyzed sampling 17 sites that included the basin main channel and its tributaries. Fish were collected using dip-nets, seine-nets and electrofishing. Fish standard length and species abundance were recorded. Species origin and salinity tolerance criteria were used to classify fish species. Water physicochemical variables, habitat structure and sampling sites elevation were recorded. A total of 33 fish species were registered, 12.1% are primary, 45.5% are secondary and 42.4% are of marine derivation. Fish species richness declined with increase of elevation (R2=0.55, p=0.0006). Two assemblages of fishes were identified: the first one associated to sites of low elevations (19-184 masl), composed mainly of secondary and marine-estuarine fish species related with high temperature, water velocity, river width, dissolved oxygen and low sand and silt substrate cover; the second one associated to sites of middle and higher elevations (185-519 masl), composed by primary and secondary freshwater fishes related with high pH, logs and rocks substrate cover. In summary, elevation and environmental variables contributed to the composition and distribution of fish in the Río Acahuapa.
Highlights
The topographic and climatic conditions are important determining geomorphological traits of a basin (Winemiller et al, 2008)
Lack of studies of freshwater fishes in some countries of Central America has created gaps in information that limit the scope of studies in the region (Miller, 1966; Albert, Miller, 1995; Matamoros et al, 2012)
The Río Acahuapa has an important number of freshwater fish species
Summary
The topographic and climatic conditions are important determining geomorphological traits of a basin (Winemiller et al, 2008). Fishes adapted to high water velocities habitats, will occur in rapids zones of the rivers, while species that cannot tolerate high water velocities habitats, will occur in zones of backwaters or pools (Bussing, López, 1977) Likewise, many of these geomorphological characteristics of the basin are influencing water physicochemical factors, such as: dissolved oxygen, pH, temperature, salinity, and conductivity, which can have an effect on fish communities (Bussing, López, 1977; Wootton, 1992). Landscape factors such as the watershed area or land-use activities can be strongly correlated with the composition, structure, and distribution of species (Schlosser, 1991; Esselman, Allan, 2010; Junqueira et al, 2016)
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