Distribution, abundance and seasonal changes of South American fur seals, Arctocephalus australis, along the coasts of Argentina.

CRESPO, E.A.; SCHIAVINI, A.; PEREZ, F. H.; CAPPOZZO, H.L

European Cetacean Society Conference Guide & Abstracts

Universitat de Valencia

Lugar: Valencia; Año: 1999 p. 26 - 26

This paper summarises new information on distribution, abundance and seasonal variation of South American Fur Seals along the coasts of Argentina. Fur Seal rookeries have been surveyed after 50 years for the whole coast and after 25 years for Chubut coast. From 1994 to 1998 the rookeries were surveyed by means of land, boat and aerial surveys in which the individuals were censused on location and by means of photographs. The individuals were classified in adult males and females, juveniles, pups and unidentified individuals. Considering the 17 rookeries along the coast, the population is close to 20,000 individuals with a maximum concentration around the breeding season between December and February. The largest rookery is located at Isla Rasa (Chubut) with around 60% of the total population in Argentina and with a seasonal variation ranging from 2,000 to 12,000 individuals. The next one are located at Isla Escondida ranging between 600 and 2,300 individuals. Isla de los Estados (Tierra del Fuego) with seven rookeries accounts for more than  3,000 individuals. Chubut islands were monitored in 1946-1949, 1972 and 1994-1998. A clear increase is shown and a rough estimate would be around 8% annually. Females were recorded with pups only at Isla Escondida but the number detected (around 200) would not account by itself for the total population estimated for the coast. Isla Rasa, which was surveyed for several years between November and February did not show reproductive social structure, reproductive behaviour among the individuals or females lactating pups. In fact, it is populated by juveniles and few adult individuals. A potential inmigration factor from other Southwestern Atlantic rookeries should be considered. The results presented in this paper, shows a clear change with respect to previous information. They establish an important base for monitoring the population trend of one of the species reduced almost to extinction during the XVIII and XIX centuries in the southern oceans.