Growth and age at sexual maturity of South American sea lions

GRANDI, M. FLORENCIA; DANS, SILVANA L.; GARCÍA, NÉSTOR A.; CRESPO, ENRIQUE A.

MAMMALIAN BIOLOGY

ELSEVIER GMBH

Año: 2010 vol. 75 p. 427 - 436

1616-5047

The average age at sexual maturity (ASM) is an important parameter for evaluating the reproductive potential orstatus of a population. South American sea lions, Otaria flavescens in Patagonia (Argentina) were exploited andreduced to less than 10% of pre-exploitation numbers. At present, the population is recovering at a rate of 6%. In thispaper, we studied growth and age at sexual maturity of South American sea lions in the south-western south Atlanticby examining 219 individuals (females and males) collected between 1989-2008. Individuals were aged by countinggrowth layer groups in tooth sections, standard body length was measured and male and female reproductive organswere examined macroscopically and histologically to establish individual sexual maturity. Maximum recorded lengthfor males and females was 264 cm and 200 cm, respectively, and maximum ages 19 and 21 yrs. ASM defined as the agewhere 50% of females are mature, was estimated at 4.870.5 years old, corresponding to a mean SL of 147 cm, about81% of their asymptotic length. First observed ovulation occurred during the 4th year, first birth may occur between 4and 5 years old. Males physiologically mature between 4-6 years, but the size of the testes shows that all males becamesexually mature by the age of 9 years when they reach a mean SL of 212 cm, about 86% of their asymptotic bodylength. The present information on ASM and growth of O. flavescens will improve the development of populationdynamics models, to investigate the impact of recovering sea lions populations on its marine environment, as well as itstrophic interactions with commercial fisheries.Keywords: Otaria flavescens; Average age at sexual maturity; Body growth; Patagonia