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New hope for Red Knots

Biologist Larry Niles
Biologist Larry Niles places a flag on a knot’s leg. Photo by Ilya Raskin

Ready the cannon!

Each spring, scientists and volunteers stationed along New Jersey’s Delaware Bay beaches capture hundreds of knots, counting and measuring them and placing numbered bands on the birds’ legs. The markers allow biologists to track individual knots.

Red Knot captures are conducted with cannon nets. When a flock of knots lands on a stretch of beach, researchers are waiting in nearby sand dunes. With muffled booms, cannons buried in the sand throw a long net over the birds. The biologists and their assistants jump up from hiding positions behind the dunes, then rush to pull the heavy netting out of the water and up the beach.

“Go, go, go!” yells Niles as a net that’s just been fired begins to drift downward, gently covering Red Knots as well as Ruddy Turnstones and Semipalmated Sandpipers.

“The Red Knot is the poster child for all these shorebirds,” says DEP biologist Amanda Dey, who leads the Red Knot project. She, Niles, and Australian ornithologist Clive Minton, who developed the cannon-netting technique now in use worldwide, quickly retrieve the birds and place them in special holding containers marked for each species.

All are banded and released unharmed.

The first comprehensive survey of Red Knots on Delaware Bay took place in 1981. Since 1986, it has been conducted annually by DEP biologists, making it one of the longest-running surveys of shorebirds in North America. The bird’s numbers have fallen dramatically, from a high of more than 90,000 in 1989 to 40,000 in 1997 to about 20,000 each year of this decade. A bright spot is the 2018 peak-count number: 32,930.

All is far from well in the world of the rufa knot. According to U.S. Fish and Wildlife Service reports, the rufa race has declined by almost 85 percent. Once, so many of the birds arrived at rest stops on Cape Cod that ornithologist Arthur Cleveland Bent, quoting an 1893 source in his Life Histories of North American Shorebirds, referred to them as “so gregarious they would collect in places in exceedingly large numbers, estimates of which were useless.”

The precipitous drop of the past 30 years has led to the listing of the rufa race as threatened under the U.S. Endangered Species Act. Scientists believe that decreased food availability is a main culprit. In New Jersey, for example, horseshoe crab eggs, which once numbered 100,000 or more in each square meter of beach, now total just a few thousand per square meter.

Overharvested and overbled

“No turn around,” reads the sign at a crossroads near Fortescue Beach,
New Jersey, along Delaware Bay. Indeed, for knots, turnstones, sand­pipers, and other shorebirds, their flight north could be a one-way ticket — if they arrive.

The taking of horseshoe crabs is regulated by the Atlantic States Marine Fisheries Commission, which has imposed limits on the fishery to allow the crabs to recover. The Carl N. Shuster Jr. Horseshoe Crab Sanctuary, which encompasses waters from south of Atlantic City, New Jersey, to just north of Ocean City, Maryland, also helps protect Delaware Bay horseshoe crabs. The sanctuary is named for horseshoe crab scientist Carl N. Shuster Jr., who conducted extensive research on the crabs.

On the state level, says Dey, “New Jersey has taken some of the most direct actions in the Mid-Atlantic to conserve horseshoe crabs and Red Knots,” including a moratorium on harvesting horseshoe crabs until crab eggs — and knots — have increased.

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In states such as Florida, a limited horseshoe crab bait and biomedical use fishery is still allowed. The crabs are collected by drug companies for the enzyme Limulus amebocyte lysate (LAL) in their blood, used to test injectable drugs and medical devices for harmful bacterial endotoxins. The endotoxins can cause life-threatening illnesses, including toxic shock.

To obtain LAL, the pharma industry works through processing facilities, which in 2016 amassed 426,195 crabs. They’re bled at processing plants like Associates of Cape Cod in East Falmouth, Massachusetts, and Charles River Laboratories in Charleston, South Carolina, then returned to the sea. How many survive? No one knows, but scientists like Niles suspect the number is lower than believed. He and others also question why processing companies don’t share their crab mortality data.

In Asia, where other horseshoe crab species are bled for LAL, the mortality rate is a stunning 100 percent, according to the Ecological Research & Development Group, a conservation organization headquartered in Dover, Delaware.

The effect of bleeding on U.S. East Coast crabs is difficult to track, but it’s likely an important factor in Red Knots’ decline, researchers believe. “Whether for bait or for blood,” says Niles, “the taking of horseshoe crabs robs Red Knots of the fuel needed for long-distance journeys.”

Horshoe Crabs Delaware Bay
COMING ASHORE: Horseshoe crabs crawl onto Delaware Bay beach in mid-May to mate and lay eggs. Photo by Greg Breese/U.S. Fish and Wildlife Service

Synthetic alternative

Perhaps the best news for both horseshoe crabs and birds is an announcement by pharmaceutical giant Eli Lilly that the company is switching from horseshoe crab blood for medical testing to a synthetic compound called Recombinant Factor C (rFC). Jay Bolden, a senior biologist at Lilly’s Global Quality Laboratories in Indianapolis, hopes other drug companies will follow Lilly’s lead.

“Despite the fact that rFC was first commercially available nearly 15 years ago, the broad use of rFC by the pharmaceutical industry has long been lagging,” wrote Bolden and Kelly Smith, also at Lilly, in a paper published in 2017 in the PDA Journal of Pharmaceutical Science and Technology. “Lilly is a leader in the sustainable production of therapeutics,” says Bolden, “and we believe that rFC provides a much more sustainable testing process.”

Scientists have found that rFC also causes fewer false positive results and is cost-effective. The use of rFC is allowed under U.S. Food and Drug Administration guidelines. Now the FDA has approved the first drug tested with rFC. Emgality, as it’s called, is manufactured by Lilly and is used to treat migraine headaches.

Findings reported in a 2018 paper in the journal PeerJ show that substituting LAL with synthetically produced rFC could reduce the use of horseshoe crab blood by 90 percent. “That’s a lot more crabs left alive and a lot more eggs for Red Knots,” says Niles. Adds Ryan Phelan, a co-author of the PeerJ paper and executive director of Revive & Restore, an organization that brings new biotech tools to conservation, “Transitioning away from the bleeding of horseshoe crabs to a readily available synthetic alternative is a win-win situation for crabs, birds, and people.”

Banded Red Knot
ON THE MOVE: A Red Knot is released after being banded and tagged on a New Jersey beach. Photo by Ilya Raskin

Turning point?

In 2017, around 35 percent of Red Knots left Delaware Bay at a weight that would power them to their breeding grounds: 180 grams, or about 6 ounces. “That’s a big improvement over the 15 percent that reached that level a decade ago,” says Niles, “but there’s still a long way to go.” Researchers think that 60 percent is the minimum necessary to return the rufa Red Knot to its healthy status.

“Red Knots won’t get there, though, unless horseshoe crabs rebound,” says Niles.

Although Limulus polyphemus ranges along the east coast from the Yucatan to Maine, “only in Delaware Bay is there a population of millions of adult horseshoe crabs, unmatched anywhere,” writes biological oceanographer Carl Shuster in The Delaware Bay Area, U.S.A.: A Unique Habitat of the American Horseshoe Crab, a chapter in a 2015 book about horseshoe crab biology, conservation and management.

How long will the bay retain its status as a haven for horseshoe crabs and Red Knots? The answer depends on how well crabs and knots weather wind, wave — and us.

  Originally Published

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Cheryl Lyn Dybas

Cheryl Lyn Dybas

Cheryl Lyn Dybas is an ecologist and science journalist and a Fellow of the International League of Conservation Writers. She often writes about birds and their habitats. Her work has appeared in such publications as Canadian Geographic, Ocean Geographic, Scientific American, and BBC Wildlife. She has been a featured speaker on science journalism and conservation biology, and serves on the committees of several international scientific societies.

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