Abstract :
Assessing human activities and understanding their interaction with seabirds constitute
important steps in the development of adequate conservation planning schemes. We evaluated
the spatial use of the marine environment by foraging Magellanic Penguins Spheniscus
magellanicus and Imperial Cormorants Phalacrocorax atriceps breeding at a newly designated
marine park in Golfo San Jorge, Argentina, to assess the potential spatial conflict between these
seabirds and commercial hake and shrimp trawl fisheries. GPS loggers were deployed on
45 adults of both species during the 2006 and 2007 breeding seasons. Distribution of hauls made
by hake and shrimp trawlers was obtained from the On-board Observer Program of Chubut
Province. Penguin foraging range varied between 25.8 and 120.1 km while cormorant foraging
range varied between 1.5 and 68.2 km. Distances travelled to fishing grounds were short for both
species (, 4.43 km) and, depending on the season, they spent a significant part of their time at
sea within waters used by both fisheries (penguins: 17.9–66.2%; cormorants: 46.0–89.0%). In
both years, foraging Magellanic Penguins and Imperial Cormorants showed a clear overlap with
operating vessels. The observed foraging patterns of penguins and cormorants suggest a high
probability of spatial conflict. Moreover, incidental mortality was regularly recorded in both
fisheries, at rates that varied between 0.02 and 0.34 individuals per haul depending on species
and fishery. Although one of the goals of the new marine park is the protection of Magellanic
Penguin and Imperial Cormorant populations, the defined boundaries do not appear to be
adequate for their effective protection. Results suggest the need to re-evaluate the spatial design
of the park and/or the definition of management actions in waters outside the park to minimise
negative effects on penguins and cormorants.
