Relationships between off-bottom bivalve aquaculture and the Magellanic steamer duck Tachyeres pteneres in southern Chile

Abstract

The interactions between aquaculture farms and endemic marine birds in the Northern Hemisphere have been a recurrent topic in the past decades. In the Northern Hemisphere, shellfish aquaculture farms have diverse effects on wildlife populations, and the substantial predation on mussels by birds can lead to culling of the birds by farm managers. In this work, we assessed the interaction between Chilean blue mussel Mytilus chilensis farms and the Magellanic steamer duck Tachyeres pteneres, an endemic duck of southern Chile whose population is thought to be declining. In particular, we assessed the importance of the Chilean blue mussel in the Magellanic steamer duck's diet, and we estimated the magnitude of losses to aquaculture due to predation by the ducks. Between March 1988 and February 1989, observations and sampling collections were performed around a bivalve aquaculture farm in Yaldad Bay (Chiloé Island, Chile). In contrast to what happens in the Northern Hemisphere, we infer that Chilean blue mussel farms do not promote the increase of the Magellanic steamer duck population in Chile: the population dynamics appear to be responding to other habitat variables. Moreover, our estimate for the losses due to predation was less than 1.6% of the annual farm production in Chile. Despite the fact that sampling was done almost 30 years ago, this study is the most recent one investigating the ecology and social behaviour of the Magellanic steamer duck and its relationship with bivalve aquaculture.