Growth in body size of the Steller sea lion (Eumetopias jubatus)

Growth models (mass and length) were constructed for male (greater than or equal to1 year old), female (greater than or equal to1 year old), and pregn ant female Steller sea lions (Eumetopias jubatus) shot on rookeries or haul outs, or in coastal waters of southeastern Alaska, the Gulf of Alaska, or t he Bering Sea ice edge between 1976 and 1989. The Richards model best descr ibed growth in body length and mass. Females with fetuses were 3 cm longer and 28 kg heavier on average than females of the same age without fetuses. Males grew in length over a longer period than did females and exhibited a growth spurt in mass that coincided with sexual maturity between 5 and 7 ye ars of age. Average predicted standard lengths of males and females greater than or equal to 12 years of age were 3.04 and 2.32 m, respectively, and a verage predicted masses were 681 and 273 kg, respectively. Maximum recorded mass was 910 kg for an adult male. Males achieved 90% of their asymptotic length and mass by 8 and 9 years of age, respectively, compared with 4 and 13 years, respectively, for females. Residuals of the size-at-age models in dicated seasonal changes in growth rates. Young animals (<6, years old) and adult males grew little during the breeding season (May-July), and adult m ales did not resume growth until sometime after November.