Reproduction of photographically identified fin whales, Balaenoptera physalus, from the Gulf of Maine

The authors photographically identified 534 individual fin whales in the Gulf of Maine from 1980-1988, including 64 females and 40 young. Individual females showed strong site fidelity to either the N or S Gulf of Maine, suggesting substock separation on the feeding range. Gross annual rates of reproduction (proportion of individuals that were young-of-the-year) ranged from 0.03-0.12 (mean 0.08) among years. Greater proportions of young were observed in samples from the southern Gulf of Maine (mean 0.12) than in the northern Gulf of Maine (0.05). Greater proportions of females also were observed in the southern Gulf of Maine (mean 0.22) than in the northern Gulf (0.10). Average time between consecutive births was 2.71 yr, which represented a crude birth rate of 0.37 young per mature female per year. A potential mean interval of birthing of 2.24 yr was estimated. -from Authors