Data from: An integrated approach to historical population assessment of the great whales: case of the New Zealand southern right whale

Accurate estimation of historical abundance provides an essential baseline for judging the recovery of the great whales. This is particularly challenging for whales hunted prior to 20th century modern whaling, as population level catch records are often incomplete. Assessments of whale recovery using pre-modern exploitation indices are therefore rare, despite the intensive, global nature of 19th century whaling. Right whales (Eubalaena spp.) were particularly exploited: slow swimmers with strong fidelity to sheltered calving bays, the species made predictable and easy targets. Here we present the first integrated population-level assessment of the whaling impact and pre-exploitation abundance of a right whale, the New Zealand southern right whale (E. australis). In this assessment we use a Bayesian population dynamics model integrating multiple data-sources: 19th century catches, genetic constraints on bottleneck size, and individual sightings histories informing abundance and trend. Different catch allocation scenarios are explored to account for uncertainty in the population’s offshore distribution. From a pre-exploitation abundance of 28,800-47,100 whales, 19th century hunting reduced the population to ~15-20 mature females between 1914 and 1926. Today, it stands at <12% of pre-exploitation abundance. Despite the challenges of reconstructing historical catches and population boundaries, conservation efforts of historically exploited species benefit from targets for ecological restoration.