Meeting Abstract
Reliable estimates of baleen whale growth rates are difficult to obtain when sampling populations at low densities and/or in complex habitats. We evaluate baleen whale population dynamics by analyzing progesterone in baleen whale waxy earplugs (N = 11, total lamina = 835, age range = 13 – 63 years). To identify pregnancies, we calculated percent change in progesterone from the previous lamina, ranked these points, then assigned the top 30% of points as pregnancies. From these pregnancies, we estimated age at first pregnancy, pregnancy intervals, and pregnancy rate. Our results matched well with published calving intervals, age at first birth, and birth rate. Next, we compared multiple individuals for age-specific fecundity (aligned by age). Our results demonstrated, for the first time, age-specific fecundity in fin whales (n = 3, total lamina = 117) and reproductive senescence beginning at 25 years, theoretically reaching zero fecundity at 55.5 years. Finally, we modeled the average rate of increase (ROI) of fin whales using a ROI model which includes age-specific fecundity and reproductive senescence. Compared to the standard ROI model, our results suggest a 19.7% reduction in future population size when projecting the ROI from each model forward to the year 2050. Using a model that incorporates age-specific fecundity and reproductive senescence is important to effective management and can be used to assess how exposures to stressors can impact vital rates of baleen whale populations over the long-term.
