It has been hypothesized that the geographical location of scallop beds in extensive shelf regions mirrors hydrographic structures (e.g. frontal systems) that favor the retention/concentration of pelagic larvae. Large, discontinuous concentrations of the Patagonian scallop (Zygochlamys patagonica) are known to have occurred recurrently (for more than 30 yr) at certain geographical locations over the extensive Patagonian shelf. These stocks, exploited since 1996, currently support one of the most important scallop fisheries in the world. Here, we investigate whether those aggregations are spatially coincidental with major frontal systems. Several pieces of information were used: historical survey data documenting the geographic distribution of the Patagonian scallop beds, catch and effort data from the commercial fleet, oceanographic data on frontal systems, and remote sensing imagery. We found that large-scale aggregations do match the location of three major and very different frontal systems in the southwestern Atlantic: the Shelf-Break Frontal System, the Northern Patagonia Frontal System, and the Southern Patagonia Frontal System. We describe the three frontal systems and their associated scallops fishing grounds and discuss which processes can contribute to sustaining the productivity of the scallop grounds in each case.

Colonial seabirds are central place foragers and likely to be subject to substantial competition for resources. Mechanisms proposed for reducing intra‐specific competition include differential inter‐sex area use mediated by adult choice. We used GPS loggers and dive recorders to study area use and dive depth in a total of 27 male and 26 female imperial cormorants Phalacrocorax atriceps breeding at a colony of some 6500 birds at Punta Leon, Chubut, Argentina during 2004 and 2005. Although time spent travelling and distances between the colony and foraging sites were similar for both sexes, males and females travelled away from their colony using routes virtually perpendicular to each other so that their foraging areas were distinctly different; females hunted close to the coast while males foraged offshore in deeper water. Consideration of foraging efficiency underwater, defined as the duration spent on the bottom divided by the dive cycle duration, showed that females were more efficient at depths < 40 m while males more efficient at depths > 40 m. We suggest that the substantial sexual dimorphism in this species may be responsible for the different depth‐linked foraging efficiencies and that selection for appropriate depths could lead to differential habitat use and putative differences in prey selection.

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. ResumenLa evaluació n de las actividades humanas y la comprensió n de su interacció n con las aves marinas son importantes para la elaboració n adecuada de esquemas de planificació n para la conservación. Se analizó el uso espacial del ambiente marino por parte de Pingü inos de Magallanes Spheniscus magellanicus y Cormoranes Imperiales Phalacrocorax atriceps reproduciendo en un parque marino recientemente creado en el Golfo San Jorge, Argentina. El objetivo fue evaluar el potencial conflicto espacial entre estas especies y las flotas arrastreras comerciales que operan sobre merluza y langostino. Se colocaron dispositivos GPS en 45 adultos de ambas especies durante las temporadas reproductivas 2006 y 2007. La distribució n de lances efectuados por los arrastreros merluceros y langostineros se obtuvo del Programa de Observadores a Bordo de la Provincia de Chubut. El rango de forrajeo de los pingü inos varió entre 25,8 y 120,1 km mientras que el de los cormoranes varió entre 1,5 y 68,2 km. En ambas especies, las distancias recorridas desde las colonias a las áreas de pesca fueron cortas (, 4,43 km) y, dependiendo del añ o, las aves pasaron una parte signific...

Many freshwater ecosystems and biotas around the world are threatened with extinction. Freshwater fishes, for example, are the most endangered vertebrates after amphibians. Exotic fish are widely recognized as a major disturbance agent for native fish. Evaluating the ecological effects of invaders presents many challenges and the problem is greatly augmented in parts of the world where the native fauna is poorly known and where exotic species are commonplace. We use the fish community of Patagonia, a small and distinct native biota dominated by exotic salmonids, as a case study to ask: what can we learn about the effects of exotic fish species from fragmentary or partial data and how do such data point the way to what needs to be learned? We review the available data and literature on the distribution and status of native and introduced fish. We compile a novel regional presence/absence species database, build fish distribution maps, describe distribution patterns of native and exotic species, and identify critical information voids. A comparative review of literature from Patagonia and Australasia, where a similar native and exotic fish fauna is found, helps us to identify research priorities and promising management strategies for the conservation of native fish fauna. We conclude that the main challenge for fish conservation in Patagonia is to identify management strategies that could preserve native species while maintaining the quality of salmonid fisheries.