Selenium and mercury in native and introduced fish species of patagonian lakes, Argentina.

A survey of mercury (Hg) and selenium (Se) contents was performed in fish collected from lakes located in two National Parks of the northern patagonian Andean range. Two native species, catfish (Diplomystes viedmensis) and creole perch (Percichthys trucha), and three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis), were caught from lakes Nahuel Huapi, Moreno, Traful, Espejo Chico, and Guillelmo belonging to Nahuel Huapi National Park and from lakes Futalaufquen and Rivadavia, Los Alerces National Park. In lake Moreno, fish diet items were analyzed and rainbow trout grown in a farm. Hg and Se were measured in muscle and liver tissues by instrumental neutron activation analysis. The average concentrations in muscle of Hg for all species, ages, and lakes are between 0.4 to 1.0 microg g(-1) dry weight (DW) with a few fish, mainly native, exceeding the United States Environmental Protection Agency health advisory for freshwater fish limited consumption, and from 0.8 to 1.5 microg g(-1) DW for Se. Average concentrations in liver of Hg in all species range from 0.4 to 0.9 microg g(-1) DW. Brown trout, the top predator in these lakes, showed the lowest average Hg burden in both tissues. Se concentrations in the liver of brown and rainbow trout, up to 279 microg g(-1) DW, are higher than those expected for nearly pristine lakes, exceeding 20 microg g(-1) DW, the threshold concentration associated with Se toxicity. These species show lower Hg contents in muscle, suggesting a possible detoxification of Hg by a Se-rich diet. Creole perch and velvet catfish livers have lower Se concentrations, with a narrower span of values (2.3 to 8.5 microg g(-1) and 3.3 to 5.5 microg g(-1) DW respectively).

Trace elements as fingerprint of lake of Provenance and of species of some native and exotic fish of northern Patagonian lakes.

A survey of trace element contents in fish muscle and liver was performed in different lakes of two northern Patagonian national parks: Nahuel Huapi and Los Alerces national parks. The aim of the work was to obtain the first set of reference data on elements that are not liable to be disturbed by human activities and to identify compositional patterns related to the species and site of collection. The species studied are native creole perch and velvet catfish and exotic brown trout, rainbow trout, and brook trout. The elements analyzed are Br, Cs, Fe, Rb, Se, Na, and Zn. Trace elements in muscle of brown trout, rainbow trout, and creole perch showed statistical patterns that allow one to identify the national park of origin, as well as which of the lakes (Traful, Espejo Chico, or the Nahuel Huapi-Moreno system) of the Nahuel Huapi National Park from which they come. Contents in the liver provide similar but less clear patterns than contents in muscle; however, in some particular cases, they provide additional information. Trace element contents in muscle are also good indicators of the species collected within a lake.

Water quality and fish surveys of Piedra del Aguila Reservoir 1993-1997

En este trabajo se presentan resultados del monitoreo bimestral que se realizó sobre la calidad del agua y los peces en el reservorio del Embalse Piedra del Aguila