A “Quintessential” Forage Fish: Understanding the Crucial Role of the Sand Lance
A new paper published in March 2020 in Fish and Fisheries reviews the state of knowledge and the research needed to update our understanding and population status of the sand lance, a zooplanktivorous fish that spans coastal temperate to polar waters in the Northern Hemisphere.
Scientists have insufficient or outdated information about the sand lance’s basic life history, population dynamics, and its ecological role as prey of many fish, birds, and marine mammals. This therefore limits our ability to understand the risks and vulnerabilities to this fish related to specific threats from changing climate and oceanographic patterns, as well as human activities such as commercial fisheries and offshore energy development. More than 20 scientists, managers, and conservation practitioners came together to explore gaps and the future research needed to inform knowledge and management of the small but important fish in the changing northwestern Atlantic Ocean environment (NWA).
What is a Sand Lance?
The sand lance, often referred to as a sand eel, is actually a zooplanktivorous fish (meaning that it eats tiny marine animals at the base of the food chain). In the NWA region, the two primary species are the Northern sand lance (Ammodytes dubius) and American sand lance (Ammodytes americanus). Sand lance are small in size and have an elongate body form that allows them to “dive” into sandy seabed sediments. The sand lance depends on the presence of clean, sandy substrates on the seafloor in relatively shallow water depths (less than 300 ft). The small (three to six inches long), wiggly fish spend their days feeding on zooplankton in the water column and bury themselves in the sand to hide from predators at night. Sand lance form dense schools that appear to fluctuate widely in abundance and distribution over seasonal, annual, and decadal scales.
The slender fish with a skinny snout is a favorite food of humpback whales (Megaptera novaeangliae), sharks, seals, seabirds, commercial fishes, and many other ocean predators. Overall, 72 regional predators including 45 species of fishes, 2 squids, 16 seabirds, and 9 marine mammals were reported to consume sand lance in the NWA region.
“Their shape makes them very attractive to many predators because they’re easy to swallow. Most marine predators don’t chew their food, rather they swallow their food whole. It’s like eating spaghetti instead of a meatball; there are no legs or spines to get caught in your mouth or throat. Even small seabird chicks can swallow large sand lance because they slide right down into the gullet,” said the study’s lead author, USGS scientist Michelle Staudinger.
Their abundance and distribution are linked to commercially valued fisheries such as Atlantic Cod (Gadus morhua) and Bluefin Tuna (Thunnus thynnus), as well as species of high conservation concern such as Humpback Whales and seabirds like Great Shearwaters (Puffinus gravis) and endangered Roseate Terns (Sterna dougallii).
Learn more about sand lance studies in: “The role of sand lance in the Northwest Atlantic ecosystem.” (pdf)
“We brought together experts from across the various resource management and research communities to summarize the current state of knowledge for these two regional species of sand lance; the Northern sand lance and the American sand lance. We wanted to also identify important information gaps,” said Michelle Staudinger, USGS scientist and lead author of the study. “The limited information we do have is from the 1970s and 1980s, and one of our concerns is that shifts in seasonal oceanographic conditions, circulation, and the phenology of lower trophic level species are affecting what were once considered to be established patterns in regional timing and availability of resources.”
According to the paper, the NWA region is experiencing rapid warming of coastal and ocean water temperatures due to climate change, with rates as high as 0.4–0.3 °C per decade since the 1980s. Regional warming has been observed during all seasons but most substantially during summer. These changes could have major effects on sand lance occurrence and subsequent impacts on commercial fisheries, seabirds, and other natural resources that depend on them.
“To the best of our knowledge this is the first comprehensive assessment of this fish species in the Northwestern Atlantic region. Results are intended to inform new research, and to help guide conservation and management efforts by regional Fishery Management Councils, regulatory agencies, fishing communities, conservation organizations, and coastal development groups, all of whom share responsibilities and interests in these fish and their predators throughout their range in continental shelf waters from North Carolina to Greenland,” said Staudinger.
The NWA is a highly dynamic ecosystem currently facing many varied impacts from climate change, fishing, aquaculture, offshore energy development, and altering nearshore and shoreline areas through activities such as sand mining and shoreline armoring. These anthropogenic activities have the potential to impact sand lance by one or a combination of threats— either directly through harvest or by degrading habitat, or indirectly through altered food web relationships. Depending on the vulnerability of these species to these stressors, there could be cascading indirect impacts on predators that could cause disturbances in the greater ecosystem with effects on dependent human-ecological systems. At the base of it all is the sand lance, which needs to be better understood and considered, especially when it comes to making policy decisions for management and conservation.
Read the University of Massachusetts Amherst news article, “At the Base of the Food Chain, a Small Fish Should Command Greater Notice, Researchers Say”.
Read the article in Fish and Fisheries titled, “The role of sand lances (Ammodytes sp.) in the Northwest Atlantic Ecosystem: A synthesis of current knowledge with implications for conservation and management.”
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