PhD candidate Tammy Silva grew up near the beach and has always felt a connection with the ocean. “I have a fascination and interest in everything that lives in it,” she said. As a high school student, Tammy completed an elective marine science class and served as a volunteer at the Buttonwood Park Zoo. Her interests and pursuits in science and conservation led her to enroll in the marine science PhD program in the Biology Department at UMass Dartmouth.
Now four years into her studies, Tammy is collaborating on a research project with the Woods Hole Oceanographic Institution to understand the occurrence patterns of toothed whales (in terms of time and space) in Massachusetts Bay, which includes the Stellwagen Bank National Marine Sanctuary, a federally protected area. Toothed whales are top predators and likely play key roles in structuring and maintaining healthy ecosystems. They are also vulnerable to human activities and previous studies have shown that toothed whales can be negatively impacted by human activities like ship noise, fishing, and pollution.
“There are four main species of toothed whales in Massachusetts Bay – the Atlantic white-sided dolphin, harbor porpoise, pilot whale, and the common dolphin,” said Tammy. “We know these animals visit Massachusetts Bay, but we don’t know if and how they influence our ecosystem health, or how they might be impacted by our activities. Massachusetts Bay is an important place for humans, too, and there is a lot of year-round human activity in Massachusetts Bay. The first step in understanding these larger issues is to answer a couple of basic questions: when and where are toothed whales in Massachusetts Bay?”
To answer these questions, Tammy uses ocean gliders (also known as an underwater autonomous vehicles) equipped with underwater microphones, which can be deployed in the ocean to record and study animal occurrence. The method of studying animal occurrence by monitoring their vocalizations is called passive acoustic monitoring (PAM). “The idea behind PAM is that we are listening for animals instead of going out and looking for them. If an animal is present in the Bay, and it’s vocalizing and we can record it, we know when and where our glider was when we recorded it and we can use that to study when and where dolphins are in the Bay.” There are lots of benefits to using PAM to study animal occurrence instead of visual surveys.
Researchers can monitor continuously for periods of weeks to months, during periods of inclement weather, and during any time of day. These opportunities are not possible with visual surveys. “We are able to gather more data and potentially learn more with PAM than we could with visual surveys,” said Tammy. “What we’re finding is that animals are present, perhaps, in Massachusetts Bay more than we thought.” In conducting her research, Tammy found that toothed whales were detected approximately 75 percent of the days they were monitored. “This tells us that toothed whales are here a lot, which means Massachusetts Bay could be an important habitat for them. A frequent presence in Massachusetts Bay also means more potential exposure to human activities.”
Massachusetts Bay is a valuable ecosystem to many marine species, as well as humans. Understanding how toothed whales use Massachusetts Bay is vital to understanding how their presence may influence the health of this ecosystem and how those of us who live, work, or play in, on or near Massachusetts Bay can work to protect these animals and their habitats for future generations.
Related project and funding
In addition to her project with the Woods Hole Oceanographic Institution, Tammy is working with Dr. Gavin Fay, Assistant Professor of Fisheries Oceanography at UMass Dartmouth’s School for Marine Science & Technology, on habitat modeling toothed whale species. She is also a recipient of the NOAA Dr. Nancy Foster Scholarship, a four-year doctoral scholarship, which Tammy said provides amazing support for graduate students. “A benefit of being at UMassD is that there are a lot of up and coming women in the marine science program, and there’s a lot of support here.”