Diet of the exotic Rainbow Trout in the critical habitat of the threatened Hooded Grebe

LANCELOTTI, JULIO L.; BANDIERI, LUCAS M.; PASCUAL, MIGUEL A.

KNOWLEDGE AND MANAGEMENT OF AQUATIC ECOSYSTEMS

EDP SCIENCES S A

Lugar: Paris; Año: 2015 vol. 26

1961-9502

The lakes of the basaltic plateaus of Patagonia represent the only repro-ductive habitat for the critically endangered Hooded Grebe (Podiceps gal-lardoi). More than 50 of these naturally fishless lakes have been stockedwith the exotic Rainbow Trout (Oncorhynchus mykiss). While the avail-able information suggests that the diet composition of trout and HoodedGrebes could overlap, to date no formal studies of the diet of RainbowTrout in these aquatic environments have been published. We charac-terized the diet of trout in one of the primary reproductive areas of theHooded Grebe based on the analysis of the gut contents of 177 individ-uals, from 9 lakes. Amphipods were clearly the most dominant group ofprey, quantified as frequency of occurrence and proportion by weight. Thecondition factor of trout and the abundance of amphipods in the stomachcontents showed a functional relationship, suggesting that the wellness of trout depends on the availability of this prey. Amphipods also represent a primary prey for the Hooded Grebe, suggesting a strong dietary overlap with the trout. The presence of trout may generate processes of compe- tition that could affect the survival of the Hooded Grebe. This interaction may be particularly relevant in large vegetated lakes, where the Hooded Grebe reproduces.