250 



Abstract.— Food habits of the South 

 American sea lion (Otaria flavescens) 

 off Patagonia were studied by means 

 of stomach content analysis. The sam- 

 ples were collected during 1982-1987 

 and 1990-1998 in northern and central 

 Patagonia. The samples (/!=59) came 

 from individuals found dead on beaches 

 and from animals recovered in inciden- 

 tal catches of the fishery. Forty-one prey 

 species (including fishes, cephalopods, 

 crustaceans, gastropods, polychetes, 

 sponges, and tunicates) were identi- 

 fied; most important were Argentine 

 hake (Merluccius hubbsi), red octopus 

 {Enteroctopus megalocyathus), Argen- 

 tine shortfin squid illlex argentinus), 

 "raneya" iRaneya brasiliensisK Patago- 

 nian squid (Loligogahi), and Argentine 

 anchovy (Engraulis anchoita). Differ- 

 ences in diet were found between sexes 

 but not between geographical area of 

 sampling, period of sampling, or source 

 of samples. Females fed mostly on ben- 

 thic species, whereas males fed mostly 

 on demersal-pelagic species. The differ- 

 ence in diet between sexes was asso- 

 ciated with different feeding grounds 

 or different home ranges and could 

 be produced by different constraints 

 in the feeding behavior of each sex. 

 These different constraints and restric- 

 tions could lead females to feed in more 

 coastal and shallower waters than those 

 waters where males feed. Some of the 

 important prey were commercial spe- 

 cies (Argentine hake, Argentine short- 

 fin squid, Patagonian squid I consumed 

 at both commercial and noncommer- 

 cial sizes by sea lions. The presence 

 of gastroliths was independent of the 

 presence of stomach parasites; how- 

 ever, gastrolith weight was positively 

 correlated with individual sea lion's 

 length, indicating that gastroliths could 

 be involved in buoyancy control. In sum- 

 mary, these stomach content analyses 

 indicate that South American sea lions 

 feed primarily on demersal and ben- 

 thic species and, in general terms, use 

 resources according to their environ- 

 mental availability. 



Food habits of the South American sea lion, 

 Otan'a flavescens^ off Patagonia, Argentina 



Mariano Koen Alonso 

 Enrique A. Crespo 



Susana N. Pedraza 



Centre Nacional Patagonico (CONICET) 

 and Universidad Nacional de la Patagonia 

 Boulevard Brown 3600 

 (9120) Puerto Madryn. Chubut, Argentina 

 E-mail address koenigcenpateduar 



Nestor A. Garcia 



Centre Nacional Patagonico (CONICET) 



Boulevard Brown 3600 



(9120) Puerto Madryn. Chubut, Argentina 



Mariano A. Coscarella 



Centre Nacional Patagonico (CONICET) 

 and Universidad Nacional de la Patagonia 

 Boulevard Brown 3600 

 (9120) Puerto Madryn, Chubut, Argentina 



Manuscript accepted 9 August 1999. 

 Fish. Bull. 98:250-263 (20001. 



The South American sea hon (Otaria 

 flavescens) is one of the most common 

 and abundant marine mammal spe- 

 cies in the southwestern Atlantic 

 and is distributed along the coasts of 

 South America from Peru to south- 

 em Brazil in both the Pacific and 

 Atlantic Oceans ( Vaz Ferreira, 1982; 

 CrespoM. Most investigations on 

 South American sea lions have been 

 focused on social behavior, breeding 

 biology, and population dynamics 

 (Vaz Ferreira, 1982; Campagna and 

 Le Boeuf, 1988; Cappozzo et al., 

 1991; Crespo and Pedraza, 1991; 

 CrespoM. Recent research has pro- 

 vided new data on the interactions 

 between South American sea lions 

 and fisheries (Crespo et al., 1994, 

 1997), on population size and trends 

 (Reyes et al., 1999; Dans et al.^), 

 and on diving behavior of lactating 

 females (Werner and Campagna, 

 1995). 



South American sea lions are con- 

 sidered opportunistic and broad- 

 spectrum feeders, feeding on fish, 

 squid, crustaceans, and occasionally 



on sea birds (Vaz Ferreira, 1982; 

 George-Nascimento et al., 1985; 

 Crespo et al., 1997). In Chilean 

 waters, their most important prey 

 are the Patagonian grenadier iMac- 

 ruronus magellanicus ) and the king- 

 clip (Genypterus spp.); no relation- 

 ship has been found between pred- 

 ator and prey sizes (George-Nasci- 

 mento et al., 1985). For Patagonian 

 waters, only preliminary informa- 

 tion has been published about feed- 

 ing (Crespo et al., 1997). Several 

 studies (Hamilton, 1934; Vaz Fer- 



' Crespo, E. A. 1988. Dinamica pobla- 

 cional del lobo marino del sur Otaria 

 flavescens (Shaw, 1800) en el norte del lito- 

 ral patagonico. Doctoral thesis, Facultad 

 de Cs. Exactas y Naturales, Universidad 

 Nacional de Buenos Aires, Buenos Aires, 

 Argentina, 298 p. 



- Dans, S., E. A. Crespo, S. Pedraza, R. Gon- 

 zalez, and N. Garcia. 1996. Estructura 

 y tendencia de los apostaderos de lobos 

 marines de un pelo iOtaria flai-escens) en 

 el norte de Patagonia. Informes Tecnicos 

 del Plan de Manejo Integrado de la Zona 

 Costera Patagonica. Fundacion Patago- 

 nia Natural (Puerto Madryn, Argentina) 

 1.3:1-21. 



