Patterns of growth and physical maturity in the western Mediterranean striped dolphin, Stenella coeruleoalba (Cetacea: Odontoceti)

Abstract

The growth and physical maturation of striped dolphins (Stenella coeruleoalba) of the northern section of the western Mediterranean Sea were studied. Fitted Gompertz growth curves indicate that females grow faster than males when they are young, but their growth ceases and the asymptotic length is attained earlier than in males. Asymptotic length was greater in males (200 cm) than in females (194 cm). Males reached vertebral physical maturity at 15–20 years old and females earlier, at 13–18 years old. Cranial maturity was apparently achieved at similar ages and body lengths. The radius and ulna, however, completed their ossification much earlier, again showing sexual dimorphism, with females maturing at a younger age (5–6 years) and smaller body length (160–175 cm) than males (8–9 years and 170–181 cm). Age-related parameters of physical maturation and growth determined for this population were similar to those estimated for the striped dolphins inhabiting Japanese waters, while length-related parameters differed markedly between the two conspecific populations. It is concluded that the only age- or length-related parameter associated with body growth or ossification of the skeleton that is liable to be affected by density-dependent forces is the body growth rate or, as a consequence, the age at attainment of sexual maturity.