Diet of breeding Neotropic cormorants at the Carrileufu River, Patagonia: is there any impact on recreational fish resources?

CASAUX R.,; RAMÓN A. ; TARTARA A.; BORRELL V.; GONC R.

ARDEOLA

SOC ESPANOLA ORNITOLGIA

Año: 2012 vol. 59 p. 279 - 289

0570-7358

SUMMARY.?Some cormorant species are perceived as negatively interacting with fish resources butconclusive evidence supporting such suggestions are scarce. Here we studied the diet of the neotropiccormorant and assessed its impact on recreational fish resources.A total of 33 pellets (regurgitated casts)and 73 regurgitations produced by the Neotropic cormorant were collected between 19 October 2006and 24 February 2007 at a colony on the Carrileufu River, Patagonia, Argentina. Fish (94.3%) were themost abundant prey, followed by crustaceans (5.1%) and molluscs (0.6%). The Patagonian silversideOdontesthes hatcheri was the most frequent fish prey, followed by the rainbow trout Oncorhynchusmykiss and the creole perch Percichthys trucha. The contribution of fish species to the diet variedthroughout the breeding season. The fish intake estimate for the colony based on parameters drawn fromprevious studies was 4.708 tons, which represents a consumption of 41,504 fish specimens. Nativespecies were the major component of the cormorant diet, comprising 75.7% of the specimens and 73.2%of the biomass consumed during the course of the breeding season. Given fish availability andproductivity within the study area, the impact on recreational fish resources by Neotropic cormorants canbe estimated to be of minor importance.