Naval Undersea Warfare Center (NUWC) Division, Keyport, has adopted Marine Mammal Monitoring (M3R) underwater acoustic sensor system for use in a testing range in the northwest Salish Sea operated jointly by the U.S. Navy and Canadian Forces Maritime Experimental & Test Ranges (CFMETR).
M3R utilizes a system of hydrophones and computer algorithms to detect, identify, and track marine mammals that might be approaching Navy testing ranges, enabling Navy personnel to avoid potentially injuring the animals.
Dr. Dawn Grebner, a bioacoustician at NUWC Keyport, said the system was originally developed by NUWC Newport in Rhode Island for deep water ranges. He said the decision to adapt M3R for the shallower Nanoose Range in the northwest Salish Sea is designed to both 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, meaning people are on the lookout for whales, porpoises, etc. Multiple factors can negatively impact visual monitoring including weather conditions, sea states and whether or not the animals themselves spend enough time on the surface to be spotted in the first place. Using a combination of hydrophones and hyper-fast algorithms, M3R has the potential to negate those limitations and increase detection of marine mammals before they approach a range’s waters.
Stephen McCormick, range engineer for CFMETR, said: “When I first took the job at the Canadian test range, I learned that one of my duties was ensuring that we were in keeping with regulations and orders regarding marine mammal mitigation. At the time, our only way to assess the presence of marine mammals was a visual search. I started researching acoustic detection of whales using hydrophones. I came across a passive acoustic detection paper online by Dr. Susan Jarvis and Dave Moretti from NUWC Newport in Rhode Island, so I contacted the authors.”
McCormick and Grebner met while studying the M3R system used at a Navy range off San Diego. They decided M3R was a tool that would be effective if adapted for the shallower waters of the Salish Sea where the Nanoose Range is located. The system will be fielded by first placing a series of non-linear hydrophone arrays on the sea floor, and then linking those sensors to the computer system.
“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. This will assist range personnel to know if animals are approaching and, if so, how close they are to us.”
M3R requires a computer processing system that will record new data from the array of underwater sensors while analyzing that data in real time. The system will alert engineers to the incoming presence of a marine mammal. It is hoped M3R will eventually enable the prediction of when marine mammals are likely to transit testing range waters.
“Challenges may occur with implementing the M3R system due to the Salish Sea environment because it’s shallower than the ranges M3R was originally designed for,” said Grebner. “Some species-specific detection algorithms need to be developed for the animals in our area and added to the M3R’s database. That will allow us to quickly identify the mammals we hear. Also, since the water is shallower, localization accuracy may need to be recalibrated due to the difference sea floor depth can have on sound transmission.”
Grebner said improving the ability to detect, track and eventually predict the movement of marine mammals is critical to protecting the habitats of these creatures. The kind of high-intensity acoustic noise often associated with testing can harm marine mammals if they are too close.
“The technology will allow us to keep track of which species are present on a daily, monthly and seasonal basis,” added Grebner. “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. Long-term datasets from M3R will allow researchers to note patterns and, hopefully, even begin predicting some of these movements. The mere fact we can better detect them and adjust our activities means we’re equipped to both protect the marine mammals and accomplish the missions we use the test ranges for.”
McCormick said a successful demonstration in the Nanoose Range could also lead to further Canadian use of the technology.
“There are a few ranges on the east and west coast of Canada that could benefit from this system. We first need to demonstrate success here with detection, localization and classification,” said McCormick. “After that, it will be up to the science community to generate the research needed to shape our decisions and responsible use of the ranges.”