Diego González-Zevallos

Spatial overlap between foraging seabirds and trawl fisheries: implications for the effectiveness of a marine protected area at Golfo San Jorge, Argentina

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.

Caracterización de las principales pesquerías del golfo San Jorge Patagonia, Argentina

RESUMEN. En el golfo San Jorge se desarrollan varias actividades economicas de relevancia, entre ellas dos pesquerias industriales: la pesqueria de merluza comun (Merluccius hubbsi Marini, 1933) y la pesqueria de langostino patagonico (Pleoticus muelleri Bate, 1888), ambas se solapan espacial y temporalmente. En la pesqueria de merluza del golfo San Jorge opera una flota fresquera de altura, compuesta por unas 20 embarcaciones, y una flota costera, compuesta por unas 30 embarcaciones. En esta pesqueria se pesca alrededor del 10% de lo capturado en el stock sur de merluza. En la pesqueria de langostino del golfo San Jorge opera una flota congeladora tangonera compuesta por 80 embarcaciones, responsable de mas del 75% de los desembarques de langostino realizados en la Republica Argentina. Ambas pesquerias tienen como principal problema la captura incidental de merluza, en una de sus principales areas de cria. En el presente trabajo se describe el manejo actual en las pesquerias del golfo San Jorge, el cual consiste principalmente en cierres espaciales y temporales para la pesca de langostino, y zonificaciones por estrato de flota para la merluza. En ninguna de las dos pesquerias descriptas se han tomado medidas que reduzcan eficazmente la captura incidental. Palabras clave: pesquerias, merluza comun, langostino patagonico, descarte, golfo San Jorge, Argentina. Characterization of the main fisheries in San Jorge Gulf, Patagonia, Argentina

Composición de las capturas y descartes generados en la pesca de merluza común Merluccius hubbsi y langostino patagónico Pleoticus muelleri: un caso de estudio en la flota fresquera de altura del Golfo San Jorge, Chubut, Argentina

The bottom trawling is the word most used fishing art generating large amounts of discards and incidental captures with a wide variety of species. In the San...

Estimación de la longitud utilizando relaciones morfométricas de huesos del cráneo, cintura escapular, otolitos y medidas específicas del cuerpo en Merluccius hubbsi en aguas patagónicas

Merluccius hubbsi is the fish with the largest distributional range along the Argentinian Shelf and one of the most relevant species in the diet of many top predators in the Southwest Atlantic Ocean. Predictive regression equations were calculated to estimate total length using head and pectoral girdle bones lengths and specific body measurements. The 166 specimens studied were obtained in January and February 2008 by coastal hake trawlers operating at Chubut Province, Argentina. Ln- transformed data gave the best fits in the equations obtained. The present study supports the use of head and pectoral girdle bones as an alternative method to identify M. hubbsi and predict its length.

Relevance of forage fish in the diet of Magellanic penguins breeding in northern Patagonia, Argentina

ABSTRACT We quantified the trophic niche of Magellanic penguins (Spheniscus magellanicus) breeding and moulting in Golfo San Jorge, Argentina, through conventional stomach content and stable isotope analysis. A total of 112 adults were flushed during the early and late chick stages of 2011 and 2012 at Isla Vernacci Norte, and at least 15 prey taxa were found, including fishes, cephalopods, crustaceans and polychaetes. Overall, Argentine anchovy (Engraulis anchoita) showed the highest contribution in terms of importance by mass (68.1–85.3%, depending on chick stage and year), except for the old chick stage in 2011 when the shortfin squid (Illex argentinus) was the main prey consumed (56.0%). Based on carbon and nitrogen isotopic values from a total of 256 blood samples, corresponding to young and old chicks and to adults of both sexes sampled throughout the incubation, chick and moult stages at the above mentioned colony and years, Bayesian mixing model outputs showed that Argentine anchovy was always the main prey (48–86%). Bayesian mixing model outputs obtained from adults of both sexes and their chicks during the late chick stage of 2013 at Isla Vernacci Norte, Isla Tova and Isla Leones also showed that Argentine anchovy was the main prey consumed. This is the first comprehensive assessment of Magellanic penguin diet composition in northern Patagonia, quantifying the relative contribution of prey in the diet of adults and chicks at different stages of the annual cycle and years, and confirms the relevance of a forage fish such as the Argentine anchovy in its trophic ecology.