The Perfect Prey by Bob Armstrong and Marge Hermans from Southeast Alaska's Natural World

Bob’s Recollections In May 1985 I was walking along the beach on back to the water and set it free. It was the first live north Douglas Island near Juneau when a small Pacific sand lance I had ever seen. My curiosity about silvery about six inches long plummeted down its ecology and behavior has led to some fascinating out of the sky and hit the ground nearly at my feet. discoveries over the ensuing years. I’ve learned that Startled, I looked up to see that a flying the sand lance may be not only one of the most overhead had dropped it. Luckily, I had my camera important fish in the North Pacific Ocean but also with me. I photographed the fish, then carried it the oceanic version of “the perfect prey.”

Sand lance are narrow, Pacific herring, eulachon, and walleye pollock, they occur in great numbers and At night or when silver-sided fish usually six to they are not travel in schools, providing a major food eight inches long. They are shaped much source for other oceanic creatures such feeding, Pacific like the long, steel-tipped spears carried sand lance burrow as , seabirds, and marine mam- by medieval knights, thus their common into the sand to mals. In Southeast Alaska sand lance are name sand “lance.” They have a pointed conserve energy the primary food of marbled murrelets, snout and a lower jaw that projects be- and escape from small, mottled brown seabirds commonly predators. This yond their upper jaw, making a nice tool seen on the water. sand lance is just for digging in the sand. A long dorsal fin extends along their backbone stopping At times sand lance make up more emerging from the than 50 percent of the diet of arctic sand under about just short of their forked tail. They look almost -like when they bend and curve , horned and tufted , com- three inches of mon murres, pigeon guillemots, king water. their narrow bodies as they swim through the water or wriggle across the sand. and coho salmon, , Dolly Varden, and several species of rockfish Sand lance are “forage .” Like in Southeast. Variations in the availabil- 98 ber of strategies to try to tip the scales toward survival in a fish-eat-fish world. During the day- time when they are feeding, they swim Black-legged kittiwakes are through the water among a number in what biologists of species that feed call a “selfish herd.” on sand lance in Crowding together Southeast Alaska. in large schools, they present poten- tial predators with a confusing sight— Richard MacIntosh a wall of wiggling bodies with eyes ity of sand lance greatly influence both peering out from all parts of it. This makes the survival and the breeding success of it difficult for predators such as murrelets many of these species. to zone in and pursue a single fish, and Besides being abundant, sand lance each individual fish has a better chance have other qualities that make them par- of survival because one of the many other ticularly valuable as prey for seabirds. fish around it may end up as lunch while They are high in body fat during sum- it swims free. mer, so they make neat high energy food What happens, though, is that mur- packages when birds such as arctic terns, relets often drive a whole school of fish puffins, and pigeon guillemots are trying to put on weight and feed their young. They’re just about the right size for the birds to feed to their chicks, and their sleek, slender shape makes them easy for chicks to swallow. A single two-ounce sand lance would provide little reward for a 250-pound harbor seal or a 30-ton , but a closely-packed school of thousands of wriggling fish is a potential banquet. So schools of sand lance attract seals, and they make many a meal for Southeast’s humpback whales, which may herd them together into a tight cluster by circling and blowing ever narrowing spirals of toward the surface of the water, where they bubbles in the water before plunging then become accessible to other predators A common raven feeds on a sand upward to engulf a bathtub-size mass of that can’t dive much below the surface lance it has dug up. closely-packed, squirming fish. after them. Serving as important prey is not a fate In what can sometimes turn into a that most species of accept will- “feeding frenzy,” large gulls land on the ingly, and sand lance have adopted a num- water and jab at the fish. Arctic terns and 99 Bonaparte gulls hover, then plunge into Wrangell. They found that during the day the water after them. Bald eagles swoop the sand lance swam out to the mouth down and grab them in their talons by the of the cove and schooled up with Pacific Burrowing sand fistful. And once again, the unfortunate herring to feed on tiny crustaceans car- lance attract a sand lance become easy prey for other ried by tidal currents. At night virtually flock of eagles creatures feeding and nesting during all the sand lance in the cove burrowed and gulls on Southeast’s short, intense summer. down into the cove’s only patch of loose, the Mendenhall Sand lance face another disadvan- coarse sand. (Everywhere else in the cove Wetlands near tage. Like bottom-dwelling fish such as the bottom was more silty or gravelly, or Juneau airport. sculpins and flatfish, sand lance do not was made up of finer sand.) have a to give them natural Other studies have come up with buoyancy. Unless they swim constantly, similar findings: sand lance burrow in they sink to the bottom. So at night, and areas that are not muddy, silty, or rocky, at times during the day when they are and where the sand is well drained and not feeding, sand lance conserve energy not too tightly packed. and hide from predators by burying When sand lance bury themselves themselves in the sand. in shallow, intertidal areas, they can be One catch to the strategy of burrow- exposed to air at extreme low tides. But ing is that, not surprisingly, sand lance the little fish seem to have physiological can burrow only in certain types of sub- mechanisms to deal with that, since they strate, so they are crowded together into can survive for at least five and a half a few suitable locations. hours in damp exposed sand. Exactly In 1978 Edmund Hobson and Lou how they do this is not known. Perhaps Barr from the National Marine Fisheries they can somehow use oxygen from the Service spent 10 days scuba diving to air. study sand lance in a cove at the head Even when they’re buried, sand of Steamer Bay on Etolin Island, south of lance inevitably attract predators. In deep

100 water, humpback whales may scuff the increasing fishing pressure in a number sea floor with their jaws to disturb sand of undeveloped countries, where they lance and flush them out of hiding. At low are harvested and shipped out to make tide when burrowing areas are exposed, food for farmed fish. This moves the nu- ravens and crows dig for the little fish, trients and energy encompassed in mas- scooping sand to the side with a twist of sive quantities of out of local their heads. ecosystems, often depleting them and In 1997 Mary Willson, then a research the crucial food supply for local people biologist at the Forest Service Pacific and wildlife. Northwest Research Station in Juneau, If this were to happen in Alaska it could made further studies of sand lance at have devastating effects on the more than Mendenhall River and at Berners Bay 100 species of wildlife that depend on the north of Juneau. She discovered that tiny sand lance for both survival and suc- ravens and crows could detect the buried cessful breeding and reproduction. The sand lance at low tide and were quite same could happen if seabeds, tidal areas, successful at excavating them. or wetlands are developed or disturbed She also found that ravens often carry without consideration for those crucial sand lance to their nests in nearby forests, areas where sand lance spawn and burrow

Adult sand lance are narrow, silver- sided fish about six to eight inches long.

or store them in trees near the nest. So sand lance no doubt occasionally become food for protection. for other forest animals such as Steller’s Much of the ocean life we depend on jays, shrews, and weasels. in Southeast and other parts of the North Lou Barr, who is both a fishery biolo- Pacific may rest on the slender back of a gist and commercial fisherman, told us small, easily frightened fish that spends of one bizarre instance when he found much of its time and energy trying to a fresh sand lance in the alpine while keep from being eaten. he was goat hunting above McGinnis Creek near Juneau. It had probably been dropped by an eagle or a raven. Although they are edible (and some folks say quite tasty), sand lance are not usually human prey in Southeast Alaska. As times change, however, that, too, may change. On a worldwide scale, as major fish populations have declined, the fish- ing activity has moved lower and lower on the food chain. Forage fish such as sand lance face 101 Bob’s Recollections An Avian Banquet

In 1987 my friend the late Pete Isleib of We were walking on the wetlands near Juneau and I found a sand lance burrowing Mendenhall River when we saw some 85 area on the Mendenhall Wetlands near the bald eagles feeding on something in a sandy Juneau airport. area not far from the mouth of the river. Through a spotting scope we were able to see that the eagles were walking around and rapidly moving their feet up and down, almost as if they were dancing. Hundreds of sand lance, apparently panicked by the activity, were popping up out of the sand and lying on the surface exhausted. (See photo above) The eagles were having a feast. Several years later my friend Mary Willson and I went out and saw Northwestern crows digging sand lance in the same area. They generally captured sand lance in eight digs or less. (See photo to left)

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