Fishes and environment in northwestern Argentina: from lowland to Puna.

MENNI, R; MIQUELARENA, A; VOLPEDO, A.V

HYDROBIOLOGIA

Kluwer Publisher Netherlands

Año: 2005 vol. 544 p. 34 - 49

0018-8158

The fish fauna and its relationships with physiography and climate were studied in northwestern Argentina from 21º30´S to 26º30´S and 63º30´W to 65º50´W, an area about 10,276 km2. Along a southeast-northwest gradient, the Chaco forest at low altitudes gives way to the Yungas cloud forest in highlands, and then, to an increasing desertic landscape, with xerophytic vegetation and scarce rainfall along the Grande River. Finally, extreme desert conditions prevail in the most northern part at the Puna plateau. Data on water chemistry were obtained from places from 400 to over 3800 m a.s.l. In all 3,278 fish specimens of 52 species were collected. Previous lists included 84 species. Only 19 were shared, meaning that 40 species are new for the area and/or particular localities. These results increase by a third the number of species in northwestern Argentina. The fish fauna was represented by eurytopic species of Paranensean genera as Astyanax, Bryconamericus and other characoids, mixed with locally distributed siluriforms. In hard conditions, species of Trichomycterus predominate. Species assemblages show a combination of a large number of species typical of, sometimes endemic or rather abundant in the area, combined with a few species of paranensean character. Fish assemblages were clearly defined by faunistic composition and distribution related with physiography and climate traits. A significant negative relationship is observed between species number and abundance with increasing altitude, and positive relationships exist with mean annual temperature and other climate traits. There are consistent differences between water chemistry traits preferred by different species. Diversity values (Shannon index) agree with the described pattern of increasing impoverishment of the fish fauna in northwestern Argentina, related with increasing altitude and dryness and decreasing temperature.