A Close Look At The Sand Lance

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Catching a dawn low tide for clamming on Cape Cod earlier this month, I set out across a large expanse of sand flat with a bucket and rake, and my eye on the farthest and lowest portion of bottomland left exposed by the pull of the sun and moon.I wasn’t the only one up early to take advantage of the new moon low tide: Flocks of several species of plovers in their winter plumage were already working the wet edges of the flats, where a new and short-lived boundary between terra firma and the bay had been exposed.

Some time and a few clams later, a strange flash of silver in the grooved wake of the rake caught my eye. I bent down to investigate. There, in the saturated grainy sand, a small fish wiggled beneath the surface and out of sight. I was able to retrieve the 3-inch-long, eel-like creature for a closer look, and recognized it as the sand lance (Ammodytes sp.).

I’d read accounts of this unusual fish surprising clammers, with dozens of them surfacing suddenly from the wet sand flats when disturbed. One description, written in 1884, is often mentioned in the literature and is based on an incident near where I was: When the author stuck his clam hoe into the sand, “a great section of the beach in Provincetown Harbor became alive with dancing forms of dozens of these agile fishes.”

The sand lance is a very slender fish with a dramatically elongated body, a small head with a sharply pointed snout, a lower jaw that protrudes quite a bit beyond the upper, and a small, deeply forked tail. Other distinctive characteristics are its single long, low, spineless dorsal fin (not readily seen among specimens in hand) and a lack of teeth. It also lacks a swim bladder, an adaptation that apparently enables it to more easily burrow into bottom sediments. The only fishes that one might confuse with the sand lances are young eels.

According to one of my references, “Bigelow and Schroeder’s Fishes of the Gulf of Maine,” “confusion also surrounds species recognition within this group … For example, 23 nominal species have been described in the genus Ammodytes. However, only six species are currently recognized, two of which occur in the western North Atlantic.”

Those two are the inshore sand lance (Ammodytes americanus) and the offshore sand lance (A. dubious). Based on location, the species I found was most likely the former, but the offshore species has been regularly captured inshore. Renowned ichthyologists Bigelow and Schroeder actually questioned the validity of the two western North Atlantic species, and I wonder if the scientist credited with naming the offshore species “dubious” also had his doubts.

Long Island is well within the geographic range of both species, which covers the inshore and offshore waters from Chesapeake Bay north to Hudson Bay and Greenland. But over the course of 25 years of seining for marine creatures as part of nature programs on the South Fork, I’ve only captured one specimen. Pete and Judy Weis, marine biologists who have been doing marine seining programs for South Fork Natural History Society since the 1980s, reported that they have never captured a sand lance.

Sand lances are also called sand eels, especially among fishermen who use them, as well as artificial replicas of them, as bait for game fishes. They not only resemble eels but they swim as eels do, with lateral undulations of their slender bodies. They also share the eels’ habit of burrowing in the sand, leading the way with their pointed snouts and either leaving part of their body protruding or burying themselves until completely out of sight.

November marks the start of their spawning season, which runs into March and mainly occurs on the inner half of the continental shelf over sand and gravel bottoms. Another interesting fact shared with eels is that natural spawning has not been observed. The eggs are demersal; that is, they sink to the bottom of the water column, and are adhesive.

Incubation on bottom sediments is unusually long. Depending on water temperature, eggs hatch in 30 to 80 days. The larvae are planktonic for their first two or three months, feeding mainly on phytoplankton, but also eggs of marine invertebrates, and copepods as they grow in size. Another unusual feature is the fact that the time of hatching coincides with a dearth of phytoplankton.

At 3 months old, they are approximately 1.4 inches in length, and their diet has shifted to one with proportionately more copepods and less phytoplankton. At this time they also begin to display schooling behavior (sometimes joining schools of similar-sized Atlantic herring), as well as burrowing behavior, the latter being an adaptive strategy to avoid predatory fish.

Unlike the eel, which is a nocturnal predator, the sand lance was thought to feed exclusively during the daylight hours. But recent research revealed they feed both day and night. As they develop, they gradually move farther offshore. That may seem an odd direction for these small 1-to-2-inch-long juvenile fish to take in late winter, but that direction brings them closer to the Gulf Stream, and warmer water.

There is some evidence that mature sand lances will spend most of the winter dormant, buried in bottom sediments.

Sand lances are mature and ready to reproduce at 2 years of age. They can live for up to 9 years, and can reach 15 inches in length, but studies have shown that 1-to-3-year-old fish dominate most populations.

This fish resource has not been extensively exploited commercially in the northwestern Atlantic, and sand lance populations are robust here. There was a dramatic increase in their populations in the 1970s, peaking in 1981. This population explosion and subsequent decline was found to correlate to stocks of mackerel and herring, both major predators of sand lance, declining in the 1970s and rebounding in the late 1980s.

Mackerel and herring are not the only predators of sand lance: Cod, hake, flounder, haddock, terns, porpoises, fin and humpback whales, and harp seals all feast heartily on the prolific baitfish. Research has shown that 45 species of marine fishes, 40 species of birds and 12 species of marine mammals utilize sand lance in their diets. As such, this species (not unlike the Atlantic silversides) provides a major link in the marine ecosystem between the zooplankton community and many other levels in the food chain.

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