U.S. Navy Deploys Acoustic Sensors to Track Whales in Salish Sea

The Nanoose Bay test range facility, with a U.S. Navy Cape Flattery-class torpedo test vessel at the right (file image courtesy Ken Walker)

Published Feb 25, 2020 8:55 PM by The Maritime Executive

The U.S. Navy is adapting an acoustic sensor system in order to monitor marine mammals in the Nanoose Bay test range in the Strait of Georgia. The acoustic sensors will help in planning and conducting joint U.S.-Canadian naval testing activity to minimize impact on marine mammals, like the endangered southern resident killer whale. High-intensity underwater noise from military testing can harm marine mammals if they are too close.

The system - Marine Mammal Monitoring (M3R) - uses hydrophones and computer algorithms to detect, identify, and track marine mammals that might be approaching Navy testing ranges. Dr. Dawn Grebner, a bioacoustician at NUWC Keyport, said the system was originally developed by NUWC Newport in Rhode Island for deep water ranges. The decision to adapt M3R for the shallower Nanoose Range is designed to protect marine mammals and improve the Navy’s understanding of the animals’ behavior.

“The hope for the system is two-fold,” said Grebner.  “One is to improve real-time monitoring during range events, and the second is to obtain a long-term understanding of the presence of these species in terms of when they move through our range areas, and how long they remain, in order to ultimately improve our management of the environment.”

Currently, marine mammal monitoring consists of visual sightings, but this method is inconsistent due to changing weather conditions, sea states and how much time the animals are spending on the surface. M3R is not limited by these factors and may help increase detection of marine mammals before they approach the range.

“Multiple hydrophones in a non-linear array improve the ability to locate marine mammals,” said Grebner.  “For example, a whale call will appear at a fixed location, and as the animal moves through the water, we can see the location of the next call, so we are essentially tracking the animal."

The system was developed for deep water, Grebner says that it may be challenging to implement in the Salish Sea environment because it’s shallower than the ranges M3R was originally designed for. In addition, new detection algorithms need to be developed for Pacific Northwest species. 

“M3R technology will also allow us to acoustically detect species that are normally hard to find due to their own low profile.  Whether an animal migrates through here or lives here, its presence in specific areas is unpredictable on a daily or monthly basis," she said. "Long-term datasets from M3R will allow researchers to note patterns and, hopefully, even begin predicting some of these movements."