Where have all the right whales gone?

Duke University's Marine Geospatial Ecology Lab led a collaboration of 11 institutions in the United States that pooled 17 years of available visual survey data covering 9.7 million square kilometers of the U.S. Atlantic -- roughly the same area as the entire contiguous United States.

This information was coupled with auditory data from almost 500 hydrophone recorders in US Atlantic waters that captured whales' calls. Lining up visual and acoustic datasets for the first time, researchers built a statistical model to estimate the number of whales per square kilometer at different points in time. Researchers published their findings on March 20, 2024 in Marine Ecology Progress Series.

"The more accurate and detailed the mapping, the better chance we have to save dwindling numbers of right whales from preventable injury and fatality," said Patrick Halpin, director of Duke's Marine Geospatial Ecology Lab. The lab studies marine ecology, resource management, and ocean conservation, using data to inform ocean management and governance.

Other current real-time efforts to track and protect the whales from deadly encounters with human activities have been incomplete or ineffective. Electronic tagging can harm whale health, and it is infeasible to continuously monitor more than a small fraction of the population that way.

The statistical model is a revision of a 2016 model that predicts whale density from environmental data, like sea surface temperature. This latest version incorporates new data to reflect whales' changing migration and feeding patterns, including their presence in new areas that lack protection measures for marine life.

"With nearly three times more aerial survey data than we had before, and confirming evidence from the hydrophones, we were able to show how strongly the population has shifted its distribution," said Jason Roberts, a Duke research associate and lead author of the study.

Right whales maintain the health and balance of marine environments and the entire food web through their feeding habits. As climate change has reduced the population of their prey, whale migration patterns have become more unpredictable, increasing the chances that human activities, like commercial fishing, may harm whale health and chances of reproduction.

Using maps obtained by satellite ocean monitoring, or from physical ocean models like the recently published one, researchers can more accurately predict whale density across the U.S. east coast.