Body growth and reproductive parameters of common dolphins from the Southwestern Atlantic

Abstract

Common dolphins, Delphinus delphis, in the southwestern Atlantic Ocean are subject to incidental mortality in fishing gear. However, no information on trends in abundance or estimates of bycatch mortality are available to evaluate the impact of this threat on the population. This study presents estimates of life history parameters using postmortem data obtained over a 17-year period in Argentina. Ages were determined for 93 specimens, and reproductive organ samples were examined (n = 89). Immature animals ranged from 0 to 6 years in females and from 0 to 9 years in males. Mature animals ranged from 7 to 21 years in females and from 6 to 23 years in males. The asymptotic body length (L∞) described by a Gompertz model fit to age-length data was 196 cm, 95% CI [192.45, 199.76] for females and 210.75 cm, 95% CI [206.64, 215.30] for males and was attained at 14 years in females and 15 years in males. Comparison to other populations showed that L∞ were shorter than estimates from New Zealand, similar to L∞ from eastern North Atlantic, and longer than estimates from North Pacific common dolphins. Lmax reported here were shorter than New Zealand ones but similar to those previously reported from other populations.