Koen Alonso et al : Food habits of Otaria flavescens 



251 



reira, 1982; George-Nascimento et al., 1985) have 

 reported the presence of gastrohths in this species, 

 and others (Taylor, 1993) have suggested functions 

 for them (food processing, buoyancy control, elimina- 

 tion of internal parasites, and alleviation of hunger). 



The marine ecosystem in Patagonia supports one 

 of the most intense fisheries in the world, with 

 approximately one million tons of catch per year 

 during the 1990s (Anonymous, 1996). South Ameri- 

 can sea lions are reported to be caught incidentally 

 in the trawl fisheries for Argentine hake iMerliiccius 

 hubbsi) and Argentine red shrimp iPleoticus miiel- 

 lerl) (Crespo et al., 1994, 1997). Some of the target 

 and bycatch species of these and other fisheries, such 

 as the Argentine shortfin squid (Illex argentinus) 

 fishery, are consumed by South American sea lions 

 (Crespo et al., 1997). The development of the fisher- 

 ies may have been one factor that slowed the recov- 

 ery of the South American sea lion population after 

 harvesting of this marine mammal species ended in 

 the mid 1960s (Crespo and Pedraza. 1991). 



The objectives of this research were to describe the 

 diet of South American sea lions off Patagonia, to 

 evaluate some hypotheses on the function of gastro- 

 hths, and to explore the possibility of trophic compe- 

 tition with commercial fisheries. 



southwestern 

 Atlantic Ocean 



• Rookeries 

 o Sampling sites 



Materials and methods 



Sample studied 



The total sample was composed of 59 stomachs from 

 28 males and 31 females, obtained in the periods 

 1982-1987 and 1990-1998 (Table 1). Most of the 

 1982-1987 sample (?! = 10) was collected in the north- 

 ern area of Patagonia (Fig. 1). These animals were 

 found dead on shore. The 1990-1998 sample in^AQ) 

 was collected in the northern and central Patagonian 

 areas (Fig. 1). During this period, the animals were 



Figure 1 



Study area, showing the two geographical 

 areas considered in this work: northern 

 and central Patagonia. The filled circles 

 indicate the location of rookeries of South 

 American sea lion and the empty circles 

 indicate sampling sites. 



obtained from two sources: shores where animals 

 were found dead ( 14 males and 24 females ) and fisher- 

 ies v/Iiere animals were caught incidentally (8 males 

 and 3 :. 'Table 1). Samples were clumped 



