Where the Humpback Feeds
Exploring National Marine Sanctuaries
By Rachel Plunkett
“All Nature is linked together by invisible bonds and every organic creature, however low, however feeble, however dependent, is necessary to the well-being of some other among the myriad forms of life.”George Perkins Marsh, “Man and Nature” (1864)
One of the most beloved marine mammals in the world—the humpback whale—graces the waters of Stellwagen Bank National Marine Sanctuary during the spring, summer, and fall months each year in large numbers. Although whales such as humpback, finback, and right whales are massive in size, they are not invincible to threats from humankind. Large ship strikes and entanglement in fishing gear are two of the greatest direct threats to whales in the area.
In an effort to reduce threats to endangered whales in the sanctuary, researchers started investigating where and when whales spend their time. If vessel traffic and whales are occupying the same areas, then certainly it would be more sensible to move the shipping lanes than it would be to ask the whales to move. The collaborative study relied on data from 25 years of more than 250,000 whale sightings and resulted in a 12-degree northward adjustment of the existing Boston Traffic Separation Scheme shipping lanes in 2007. This shift resulted in an 81% decrease in risk of ship strikes for all baleen whale species in the sanctuary, while having a minimal impact on travel time for vessels.
But that wasn’t the only conservation success that came from these datasets. Throughout the shipping lane study, researchers had discovered that the whereabouts of humpbacks had a lot to do with the distribution of schools of small pencil-like fish called sand lance. Sand lance are a type of forage fish, about 3-6 inches in size, that can be found—as the name implies—in sandy habitats. But, as anyone who’s wedged their toes into the soft white sand of the Bahamas and the coarser brown sand of New Jersey’s beaches knows, not all sand is created equal. In fact, sand ranges from 0.06 millimeters for very fine sand (about one-fifth the grain size of a grain of table salt), to the diameter of the tip of a fresh crayon (2 millimeters). Because they spend a lot of time buried in the seafloor, sand lance prefer a specific type of sand that is coarse enough to hold lots of oxygen between the grains, but soft enough to allow them to burrow quickly. The sand at Stellwagen Bank is just right, which explains why these fish prefer to concentrate here.
In the Northwest Atlantic, These tiny fish are a favorite food of humpback whales and another species of ecological importance, great shearwaters (Ardenna gravis). They also sustain commercially important fisheries such as Atlantic cod (Gadus morhua) and bluefin tuna (Thunnus thynnus). The data from the shipping lane studies led to further studies on the overlap of sand lance, humpbacks, and shearwaters, and the results showed that the predators go where the sand lance are. Really, you could say that sand lance are the backbone of Stellwagen Bank National Marine Sanctuary, sustaining the charismatic wildlife that people flock from all over the world to see, and the livelihoods of local fishermen and ecotourism companies.
According to Stellwagen Bank National Marine Sanctuary Research Ecologist, Dave Wiley, sand lance are the unsung heroes of the sanctuary and much of the Gulf of Maine. “Sand lance are high in fat content and can be found in large schools, making them an ideal forage fish for a variety of predators. In fact, over 70 species in the Northwest Atlantic are known to consume them. In addition, their slender body form makes it easy for seabird chicks to swallow them, kind of like slurping spaghetti, so they are of particular importance for chick growth and survival.”
Effective ecosystem management requires in-depth information on how marine species are using habitats and the environmental factors that affect animal behaviors and relationships. This collaborative research on sand lance and the wildlife that rely on them led to a multidisciplinary workshop in 2017 that resulted in an important review paper on sand lance biology and significance in the ecosystem. From 2018 to 2020, the Bureau of Ocean Energy Management (BOEM) funded an in-depth study of sand lance in and around the sanctuary, which further illustrated the ecologic and economic value of sand lance. As a result, in 2020 Massachusetts limited daily sand lance landings to 200 pounds per person, thereby discouraging the development of a commercial fishery for sand lance, which is the largest single species fishery in the North Sea. Rhode Island adopted the same regulations in 2021, with other northeast states considering similar actions. These are some of the first forage fish regulations in New England and the only to protect sand lance.
What About Climate Change?
These studies on sand lance, seabirds, and whales at Stellwagen Bank National Marine Sanctuary over the last decade, combined with climate change data, have given a new sense of vulnerability of the ecosystem. More recently, studies by researchers at Woods Hole Oceanographic Institution, Stellwagen Bank National Marine Sanctuary, NOAA’s Northeast Fisheries Science Center, University of Rhode Island, Boston University, and the University of Connecticut have found a correlation showing that climate change may lead to a decline in the availability of sand lance in the Gulf of Maine. The sand lance’s primary food source—a tiny marine zooplankter called Calanus finmarchicus—thrives in the cold northern waters. As ocean temperatures continue to rise, more heat is transported by the Gulf Stream from the tropics toward the North Atlantic, causing C. finmarchicus populations to decline. A reduction in the amount of food available at the bottom of this food web could have cascading effects up food chains—impacting sand lance, shearwaters, humpback whales, and commercially-valuable fish as well.
Remember how sand lance are very picky about sand? There’s a reason why their habitat specificity is so important. “Sand lance are potentially quite vulnerable to climate change because they’re kind of stuck in one habitat,” said Wiley. As the food web studies indicated, “if sand lance disappear due to habitat loss or climate change, we could lose much of what makes Stellwagen Bank National Marine Sanctuary a national treasure, which is why this work continues.”
Rachel Plunkett is the writer/editor for NOAA’s Office of National Marine Sanctuaries