Composition and seasonal variation in the diet of the South American sea lion (<i>Otaria flavescens</i>) from Quequén, Argentina

Abstract

Diet seasonality in South American sea lions, Otaria flavescens, was studied using 252 scats from a male-exclusive haul-out site located in Puerto Quequén (38º37'S, 58º50'W) Argentina during 2001. Prey species were identified from hard remains and their relative importance was assessed considering frequency of occurrence, abundance and biomass. The main prey consumed by sea lions were teleost fish (20 species), followed by cephalopods (four species) and crustaceans. The raneya, Raneya fluminensis, was the most frequent prey year-round, and the most abundant in autumn and winter. The Argentine anchovy, Engraulis anchoita, and the stripped weakfish, Cynoscion guatucupa, were the most abundant prey in spring and summer, respectively. Seasonal differences in the sizes consumed were only found for C. guatucupa. The sea lions from Puerto Quequén showed a diverse diet, mainly feeding on demersal and pelagic prey. Our study fills a geographical gap on the seasonal variation of the diet of South American sea lions. Two main patterns emerged from studies conducted along the geographic range of the species: (1) O. flavescens is a generalist and opportunist feeder, preying on a wide range of species; mainly those of pelagic and demersal habits, (2) South American sea lions change the frequency and/or specific composition of their diet seasonally, possibly as a result of changes in the relative availability of each species in the environment.Resumen: La variación estacional en la dieta del león marino de América del Sur, Otaria flavescens, fue estudiada a partir de 252 heces recolectadas en una colonia no reproductiva de machos localizada en Puerto Quequén (38º37'S, 58º50'O) Argentina durante el año 2001. Las presas fueron identificadas a nivel de especie a partir de restos duros y su importancia relativa fue evaluada a partir del cálculo de la frecuencia de ocurrencia, la abundancia y la biomasa. Las principales presas consumidas por los leones marinos fueron peces (20 especies), cefalópodos (cuatro especies) y crustáceos. La raneya, Raneya fluminensis, fue la presa más frecuente durante todo el año y la más abundante en otoño e invierno. La anchoíta, Engraulis anchoita, y la pescadilla de red, Cynoscion guatucupa, fueron las presas mas abundantes en primavera y verano respectivamente. Diferencias estacionales en las tallas de las presas consumidas se encontraron sólo en C. guatucupa. Los leones marinos de Puerto Quequén muestran una dieta diversa, consumiendo principalmente especies demersales y pelágicas. Nuestro estudio completa un espacio geográfico con datos sobre la dieta y contribuye al estudio de la variación estacional de la misma en los leones marinos de América del Sur. Así, se completan los estudios a lo largo de casi todo el rango de distribución geográfica. Dos conclusiones principales surgen a partir del presente estudio: (1) O. flavescens es un predador generalista y oportunista que consume un amplio rango de especies, principalmente aquellas de hábitos pelágico y demersal, (2) Los leones marinos d...

Diet of the South American sea lion Otaria flavescens during the summer season at Río Negro, Patagonia, Argentina

“…South American sea lions seem to be generalist and opportunistic predators, with fish being the main prey group, followed by cephalopods and crustaceans (Thompson et al 1998, Koen Alonso et al 2000, Bustos et al 2012. However, studies on the diet of Otaria flavescens populations distributed along the Argentine coast are scarce, and most of them reported only preliminary results (Koen Alonso et al 2000, Suárez et al 2005, Romero et al 2011, Bustos et al 2012). These studies were based on stable isotope techniques and the analysis of stomach contents and scats.…”

Variation in the isotopic composition of striped weakfish Cynoscion guatucupa of the Southwest Atlantic Ocean in response to dietary shifts

“…We provide mean values of isotopic composition for different size classes of C. guatucupa that could be used as input data in future studies of food webs since this species represent an important prey of different marine mammals and seabirds from the area (Petracci et al, 2004;Suarez et al, 2005;Paso Viola et al, 2014). These results also contribute to the study of the diet of the striped weakfish as reinforced previous classical studies of diet based on analysis of stomach content, providing valuable information on the variation in the isotopic composition in response to dietary shifts of one of the most important fishery resources from the Southwest Atlantic Ocean.…”

“…This stock was severely depleted from 1995 to 2006 (Aubone et al, 2006), decreasing its yields of the artisanal fishing fleet in Bahía Blanca estuary, which finally collapsed between 2000and 2004(Lopez Cazorla et al, 2014. Moreover, this species is still an important prey of different species of marine predators (Suarez et al, 2005;Paso Viola et al, 2014).…”

redictive regression equations were generated to estimate total length of the stripped weakfish (C. guatucupa) using skull and pectoral girdle bones, specific body and otolith lengths

“…16(1): 89-93, 2014ISSN 1514-5158 (impresa) ISSN 1853 Estimación de la longitud de la pescadilla de red (Cynoscion guatucupa) (Actinopterygii: Sciaenidae) utilizando relaciones morfométricas de huesos del cráneo y de la cintura escapular, otolitos y medidas específicas del cuerpo bido a su baja tasa de digestión, los huesos del cráneo y de la cintura escapular se convierten en una alternativa o complemento al uso de los otolitos en estudios sobre dieta (Hansel et al, 1988;Scharf et al, 1997Scharf et al, , 1998Gosztonyi et al, 2007;González Zevallos et al, 2010, Perez comesaña et al, 2014. La pescadilla de red Cynoscion guatucupa (cuvier, 1830), es un pez demersal y de hábitos costeros que se distribuye desde los 22º 35' S en costas del Brasil hasta los 43º S en aguas de Argentina (cousseau & Perrotta, 1998), constituye una presa importante para depredadores tope como el lobo marino sudamericano (Otaria byronia), el delfín franciscana (Pontoporia blainvillei), el tiburón gatuzo (Mustelus schmitti), el tiburón gatopardo (Notorhynchus cepedianus), el tiburón bacota (Carcharhinus brachyurus), el tiburón cazón (Galeorhinus galeus, el tiburón escalandrún (Carcharias taurus), el tiburón ángel (Squatina guggenheim) y la raya (Atlantoraja castelanaui) (rodríguez et al, 2002;Lucífora, 2003;Lucífora et al, 2005Lucífora et al, , 2006Vögler et al, 2003;Suárez et al, 2005; Perez comesaña, datos inéditos).…”