JanetMann, a biology professor at Georgetown University, is director of the Shark Bay Dolphin Research Project.
A sleek gray dolphin emerges, blows and glides beneath the surface, then another and another. Seventeen bottlenose dolphins, including several newborn calves and their mothers, swim closely together in the lower Potomac River. Although I have studied wild dolphins for more than 30 years, I didn’t really know they were so close to home until my husband and I bought a small cottage on Virginia’s Northern Neck, one of the most beautiful places I’ve seen — a mere two hours from the District.
In 2015, with a little help from Georgetown University and some foundation funds, we bought Ahoya, a small used skiff, and a camera and began systematic surveys of the lower Potomac waters with a team of undergraduate and graduate students — looking for dolphins.
Our first year, we had only a few survey trips but we identified about 200 dolphins based on their dorsal fin shapes and marks. In 2016, more than 400 individual dolphins graced the Potomac. Now, we are well over 500 and counting. We have had some groups with more than 100 individuals.
Scientists aren’t the only ones who get very excited about dolphins. A story in the Chesapeake Bay Journal about our work sparked many watermen, boaters, local government officials and other groups to contact us to tell us what they have seen or just to ask questions.
Bottlenose dolphins are apex predators, relying on fish and squid, and are what biologists call “bioindicators.” That means they tell us whether the environment is healthy. If there are a lot of fish, there will be dolphins. Commercial fisheries will also benefit. So while some fishers might be disappointed that the dolphins spirited away a few fish, dolphins have been a sign of good luck to watermen for centuries.
As apex predators, dolphins accumulate whatever toxins are in the fish and store them in their blubber. If there is chemical pollution, it winds up in fish and ends up in dolphins. (Humans store toxins in their fat tissue, too.) Unfortunately, the only way to offload these chemical cocktails is in their milk supply. In Florida, scientists found that firstborn offspring, who receive all the pollutants that their mother has accumulated, are much more likely to die than later-born offspring. As a female dolphin