Artículo Composición de las capturas y descartes generados en la pesca de merluza común Merluccius hubbsi y langostino patagónicoPleoticus muelleri: un caso de estudio en la flota fresquera de altura del Golfo San Jorge, Chubut, ArgentinaCatches composition and discards generated by hake Merluccius hubbsi and shrimp Pleoticus muelleri fisheries: a case of study in the high-sea ice trawlers of San Jorge Gulf, Chubut, Argentina Abstract.-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 Jorge Gulf Argentine Patagonia, operates a fleet whose target specie is the hake Merluccius hubbsi, alternating with red shrimp Pleoticus muelleri. The information for this study covers a period of 10 years (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) and was collected by the On-board Observer Program of the Chubut Province (POBCh). Were identified a total of 90 taxa, 33 invertebrates, 34 osteichthyes and 22 chondrichthyes. Multivariate analysis indicated differences in the composition of the catch when the target species was shrimp or hake. When the target species was the hake catch composition varied by fishing areas, this pattern was not observed when the target species was the shrimp, with different numbers of taxa in the northern and central Gulf (north: hake 79 taxa, shrimp 71, center: hake 60 taxa, shrimp 50). The utilization of different species caught when the fleet operated on hake was integral, however when the fleet operated on shrimp most of the taxa were discarded. This study characterized the composition of the fleet catches at San Jorge Gulf, described the species caught when the fleet operates on hake or shrimp, analyzes the frequency of occurrence and abundance and describes the use of different taxa identified. Key words: Catches composition, Merluccius hubbsi, Pleoticus muelleri, ice-trawlers fleet, San Jorge GulfResumen.-La pesca de arrastre de fondo es el arte más utilizado a nivel mundial generando grandes cantidades de descarte por la captura incidental de una amplia variedad de especies. En el Golfo San Jorge en la Patagonia Argentina, opera una flota fresquera de altura cuya especie objetivo es la merluza Merluccius hubbsi, alternando con mareas a langostino Pleoticus muelleri. La información para el presente estudio abarca un periodo de 10 años (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) y fue obtenida por el Programa de Observadores a Bordo de la Provincia del Chubut (POBCh). Se identificaron un total de 90 taxones, 33 invertebrados, 34 peces óseos y 22 peces cartilaginosos. Los análisis multivariados describen 2 agrupamientos, el primero cuando la especie objetivo fue la merluza y el otro cuando la especie objetivo fue langostino. Cuando la especie objetivo fue la merluza la composición de las capturas varió según las áreas de pesca aunque no se observó este patrón cuando la especie objetivo fue el langostino, con distintos números de taxones el norte y el centro d...

We assessed the potential overlap in diet composition of the kelp gull Larus dominicanus and the threatened Olrog's gull L. atlanticus breeding syntopically at Bahía San Blas, Argentina, during two breeding seasons (2006 and 2007). Diet was studied using regurgitated pellets (180 per species and year) and chick stomach samples obtained through the water offloading technique (60 per species only in 2007). Kelp gulls fed on at least 18 prey types. Fish was the most important diet component (73.3-85%, depending on breeding stage and year), mainly stripped weakfish Cynoscion guatucupa (63.3-75%). Crustaceans were the main prey encountered in Olrog's gull diet, particularly the crabs Neohelice granulata and Cyrtograpsus altimanus, with frequencies of occurrence of over 98% at all breeding stages. Fish in Olrog's gulls diet were only recorded in the old chick stage and in less than 3.3% of samples, while the occurrence of crustaceans in kelp gull diet throughout the study period was never greater than 13%. The specialised crab-based diet of Olrog's gulls contrasts sharply with the generalist and opportunistic diet of the kelp gull. The characteristics of prey remains and the large size of stripped weakfish found in kelp gull diet samples suggest they were obtained from coastal sport and artisanal fisheries. Future studies should monitor the consumption of fish waste by kelp gulls as a function of changes in fishing effort, and assess the dietary overlap between both gull species in coastal sectors where breeding birds have no access to this human-derived food source.

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