Stable isotope profiles of partially migratory salmonid populations in Atlantic rivers of Patagonia

JAVIER CIANCIO; MIGUEL PASCUAL; FLORENCIA BOTTO; SARA O´NEAL; MARCELA AMAYA; OSCAR IRIBARNE

JOURNAL OF FISH BIOLOGY

Blackwell

Año: 2008 vol. 72 p. 1708 - 1719

0022-1112

 In the present study, profiles of stable isotope composition were characterized for two species (brown trout Salmo trutta Linnaeus and rainbow trout Oncorhynchusmykiss Walbaum) with partially migratory populations in rivers along the latitudinal gradient of Patagonia. The effects of factors (e.g. ontogeny of fishes, location, species, and fasting) that may influence the stable isotope analysis (SIA) were evaluated, as was SIA evaluated as a tool to assign individual fish to their corresponding ecotype.  Anadromous fishes exhibited enriched 15N (15.2 ± 1 SD) and 13C (-19.2 ± 1.3 SD) relative to resident fishes’ 15N (8.8 ± 1.1 SD) and  13C (-23.2 ± 2.5 SD). For both species, the difference in δ 15N was larger between resident (range 6.8-10.7 ‰) and anadromous (range 14.3-17.8 ‰) fishes than that for  13C. Values of 13C, while not as dramatically contrasting in rainbow trout, provide a powerful anadromy marker for brown trout in the region. Increases were found in both 15N and in  13C during the spawning migration of anadromous rainbow trout, most likely due to fasting. Differences in stable isotopes between location, size, and species were found, suggesting different stable isotopes base levels in fresh water environments and different trophic levels and feeding location of anadromous populations. The overriding effect of ecotype on isotope signatures for both species across sampling locations points to SIA as a powerful tool for ecotype discrimination in Patagonian Rivers