Marine consumption of anadromous trout in the South Atlantic Ocean

JAVIER CIANCIO; MIGUEL PASCUAL

Washington DC

Congreso; International Marine Conservation Congress; 2009

George Mason University

  Throughout the 20th century, several species of salmonids were introduced into Patagonia from the Northern Hemisphere, becoming the salmonids aquaculture in fiords of south Chile one of the most important economic activity in the region. These human actions have driven to a colonization of most of Patagonia freshwater basins by anadromous salmonids, been the established populations in continuous expansion. The effect of salmonid freshwater introduction has been broadly evaluated but is very little what we know about the marine impact of anadromous species. While these populations provide exceptional sport fisheries, they also raise concerns about what their effect could be on the coastal marine environment. Rainbow (Oncorhynchus mykiss) and brown trout (Salmo trutta) are the most conspicuous introduced salmonids in the region and anadromous populations of both species are restricted to the southern part of Patagonia.  In this work we use stable isotopes analysis to evaluate the trophic position and diet of rainbow and brown trout at sea, and use a bioenergetics model to estimate the marine consumption of actual populations. We also compare the salmonids consumption to the abundance of preys and the consumption of potential competitors. Considering the total marine consumption of the actual population, they appear not to be a hazard to prey and other top predators in the South Atlantic. This scenario could change if we consider local impacts, like predation on invertebrates larvae on estuaries, and if the anadromous species continue invading and expanding their populations.