MEPS 575:195-206 (2017)  -  DOI: https://doi.org/10.3354/meps12211

ABSTRACT: Humpback whales were hunted almost to extinction in the 20th century, providing an opportunity to measure their post-exploitation population growth rates. Variation in growth rates may be related to many factors, and little work has been done to understand the differences among populations. First, we provided an estimate of the growth rate for the Brazilian breeding stock of humpback whales using models that consider imperfect detection applied to a long-term and broad-scale dataset collected through systematic aerial surveys. Then, a review of the literature on the population growth rates of this species worldwide and a meta-analysis were conducted to explore the differences in growth rates and their determinants. A finite growth rate of 12% yr^-1 (95% CI = 8-16%; CV = 17%) for the population wintering in Brazil was estimated from aerial surveys conducted from 2002 to 2011 and may be regarded as an empirical estimate of its intrinsic growth rate. The meta-analysis shows that there are geographical differences in growth rates, with substantial heterogeneity among studies. Growth rates of populations in the Northern Hemisphere are predicted to be lower than those in the Southern Hemisphere. The geographical differences in population parameters may be explained by spatial variability in productivity and prey availability, human impact and distinct hunting histories. Moreover, the differences in population growth rates are linked to genetic variability, with populations with higher haplotype diversity growing at faster rates. Long-term studies on dynamics of baleen whale populations reduced by whaling are invaluable to investigate the population growth and regulation of these cetaceans.

KEY WORDS: Megaptera novaeangliae · Population dynamics · Population growth rate · Exponential growth · Distance sampling · Meta-analysis