Log books of whalers in the 1800s are now being used to better protect whales.
Whaling was big business in the 1830s and detailed records were kept.
Scientists are analysing documents relating to southern right whales and sperm whales.
The National Institute of Water and Atmospheric research says scientists using the data are able to predict modern habitat patterns of the two species.
NIWA says it should lead to more effective management.