Estimates of Blue Whale Growth and Reproductive Parameters From Historical Whaling Data

ABSTRACT During 20th‐century whaling, blue whales ( Balaenoptera musculus ) were hunted to near extinction. Biological data, such as earplugs and ovarian corpora, were collected during whaling and provide information about key demographic parameters that can inform population status. We compiled earplug age data ( n = 2037) and estimated age‐length relationships using Bayesian models for Antarctic, eastern North Pacific (ENP), and pygmy blue whales. We estimated the asymptotic length for females to be 21.8 m (95% credible interval: 21.5–22.2 m) for pygmy, 23.7 m (22.7–24.6 m) for ENP, and 26.6 m (26.1–27.1 m) for Antarctic blue whales, while males were shorter with asymptotic lengths of 21.2 m (20.9–21.5 m) for pygmy, 22.5 m (21.2–23.7 m) for ENP, and 24.3 m (23.7–25.0 m) for Antarctic blue whales. In addition, we modeled relationships between age and number of ovarian corpora for pygmy and ENP blue whales, estimating that corpora are added every 2.9 years for pygmy and 2.7 years for ENP blue whales. We also estimated that female pygmy blue whales are sexually mature at 9.3 (5.6–10.7) years and female ENP blue whales at 8.6 (3.4–10.4) years. These estimates provide a historical baseline to assess changes in growth and reproduction for blue whales.