Red Knots, Horseshoe Crabs Fading from Jersey Shore

Early indications are that numbers are down for horseshoe crabs spawning along the Delaware Bay beaches and also for Red Knots, who feast on horseshoe crab eggs before completing their 9,000-mile trek to breed in the Arctic tundra.
However, numbers are changing daily, therefore wildlife biologist Larry Niles, Ph.D., wants to be cautious about explaining what is occurring this season, and why.
Niles, who along with seven others, has been monitoring and counting the Red Knots, crabs and egg density at Reeds and Cooks beaches, and other spots along the New Jersey and Delaware sides of the Delaware Bay.
Conditions Not Ideal for Migration, Spawning
Niles said May 21 that there were about 8,000 Red Knots in the area, compared to 30,000 last year, at the same time. Things changed May 24. “Up until this morning, we had an unclear picture of what was happening with the shorebirds, and why,” Niles said. “There was one-fifth of the number we’ve had in previous years.”
“The last two weeks have had adverse wind conditions for migration,” he explained, regarding the potential reasons why the numbers are lower. “The water is unprecedentedly cold. It is usually in the high 50s at the beginning of May. The horseshoe crabs need the water temperature to be about 59 degrees for a good spawn, but it’s stayed cold since early May.
“Two days ago, we had a decent crab spawn, and this morning, there was a good spawn,” he said, “but have the birds bypassed us because there haven’t been many crab eggs? Has the spawn been delayed? Has the migration been delayed?”
“We found about 14,000 Red Knots on the New Jersey side of the bay this morning, so we’re not sure if they have just arrived or are hanging out in areas where we can’t get to them,” he said.
Red Knots Travel 9,000 Miles to Breed
Red Knots travel along the Atlantic Flyway, from Chile to the Arctic, where they breed, stopping along the Delaware Bay to refuel on horseshoe crab eggs. Niles said they typically weigh about 123 grams (4.3 ounces) when they reach the bay, hoping to gain about two grams per day (seven-tenths of an ounce) during a stay that could last for nearly two weeks.
Scientists have found that birds that weigh about 180 grams (6.3 ounces) have the best chance of surviving the trek to the Arctic and successfully breeding.
Knots Undergo Changes Along the Trek
One particularly well-traveled Red Knot has flown far enough to make it to the moon and back. Each year, this bird, banded with the number B95, undertakes the journey with its fellow Red Knots, as they undergo extensive physical changes to make the trip. Flight muscles enlarge while leg muscles shrink. Stomachs and gizzards decrease while fat mass increases by more than 50%.
“We found one bird this week that weighed 89 grams (3 ounces), so it really had burned muscle to get to the bay,” Niles said. “This could reflect the lower numbers of the overall population or the late spawning season.”
According to Eric Stiles, president and chief executive officer, New Jersey Audubon Society, the number of Red Knots migrating from Chile this year is lower along the eastern coastline.
“The Delaware Bay is the last stop before the birds fly to the Arctic,” he noted. “They need to time their migration for prime conditions to raise their young in the short window of summer before heading back to South America.”
COVID-19 Impacts Study Teams
Twenty-five sites in New Jersey and Delaware usually are visited over 12 nights during a season, usually around the full and new moons, when the horseshoe crabs tend to spawn. An average nest has about 4,000 eggs, and a female has about 20 nests per season.
The eggs initially are green and opaque, becoming more transparent as they grow. The scientists count males and females within a measured area to estimate egg density and overall numbers; the goal is that there are two males for every female. In 2019, they found six males for each female.
Because of COVID-19, many local organizations have ceased volunteer crab tagging events and, instead, are relying on Niles and his team for data. COVID-19 travel restrictions between states and countries, according to Niles, who owns Wildlife Restoration Partnerships, means the usual 25-person team was cut to seven this season, supplemented by experienced volunteers who sight birds by themselves or help monitor the beaches often closed to the public for the safety of the birds.
The seven have worked in two small teams, quarantined from each other, following social distancing and other safety measures required by the Department of Fish and Wildlife.
Flip Over Crabs, but Don’t Disturb Birds
“The Red Knots are particularly sensitive to disturbances,” Niles said, “especially as they gain weight. Photographers chasing the birds to get photos, or people disturbing their roped-off beach areas will cause them to stop feeding. Keep your distance.”
Volunteers from the Wetlands Institute, of Stone Harbor, are also turning over horseshoe crabs nightly, therefore they can lay their eggs on the sands and not be flipped over by the tides. Visitors to beach areas where spawning is occurring are encouraged to report any tagged crabs they find, and flip over any found on their backs; however, do not handle them by their fragile tails.
Numbers Indicate Ecosystem Health
The spawning/migratory season usually begins the first week of May and lasts through the second week of June, but, this year, Niles is unsure when it will end because of all the conditions, which haven’t been conducive to spawning so far.
“Maybe, the spawn has been delayed this year, maybe the numbers are smaller this year; we will have to see how this turns out,” he said. “We haven’t had periods of cold like this without the May warmth.”
Both Niles and Stiles said the numbers of Red Knots and horseshoe crabs are important because they are indicative of the health of the ecosystem, which, in turn, generates business revenue and jobs for commercial fisheries, sport fishing, wildlife watching, and other ecotourism-related businesses.
Stiles said in New Jersey, that translates to 143,000 jobs and $18.9 billion in revenue. For Cape May County, ecotourism generates $600 million in revenue, according to the 2019 County Tourism Report, and the county is among the Top 10 birding spots in the world.
Impacts Over the Years Change Outlook
Over the past decades, shore visitors in the 1980s may recall the “horseshoe crab eggs piling up along the Delaware Bayshore in many places a foot deep. Forage fish relied on eggs and larvae, as did bigger fish, who eat both eggs and forage fish,” Niles said. “Sportsfish prospered. Migratory birds came to the bay and left in good condition. Fishers, birders and other tourists came from all over the country and world.”
Niles said, in the 1980s, there were 50,000 horseshoe crab eggs within a square meter on the beaches, and today, there’s less than 10,000 per square meter. “On most beaches, it’s about 5,000 per square meter,” he said.
“For a short period of time, in the early 1990s, the Delaware Bay ecosystem flourished,” Niles continued. “Small horseshoe crab harvests provided some wealth directly to local fishers, as bait for small fisheries, but most of the jobs came from the vibrant sport fishery.”
“Weakfish, flounder, stripers and blue claw crabs consume abundant crab eggs at the same time they are producing. This natural fish-production system drew sport fishers, who filled the marinas and restaurants of bayshore communities, like Fortescue or Matt’s Landing,” he added.
“Now, overfishing threatens populations of shorebirds, horseshoe crabs, weakfish, striped bass and other species,” he continued. “In the last 20 years, agencies yielded too much to the big business of fishers against the interests of sport fishers, birders and the small businesses of rural communities. Although many threats exist, climate change chief among them; the bay can be restored with the re-imposition of the public will.”
Relying on Public Trust Doctrines
In other words, according to Niles, “the fish, horseshoe crabs and birds all belong to the public, and we rely on government and agencies to fulfill public trust doctrine mandates.” In the case of the Delaware Bay, agencies are adhering to the letter of the doctrine but miss the goal. The agencies keep horseshoe crabs stable, but at levels too low to support a thriving eco-system.”
“The same could be said for weakfish and stripers,” he said. “Why? Because businesses have greater influence than the public. Natural resources might belong to everyone, but businesses dominate.”
One example Niles noted was that horseshoe crabs are maintained at a low level to provide maximum bait for conch and American eel, both “overfished” fisheries.
“Meanwhile, international biomedical corporations extract blood from a half-million horseshoe crabs each year, fueling an investor-driven enterprise worth $400 million per year,” Niles said. “Crab blood is used to detect bacteria in the medical field. The Delaware Bay supports the largest population of horseshoe crabs in the world, and these companies do nothing to speed crab recovery.”
“They have almost no restriction on the number of crabs taken or the amount of blood that can be extracted,” he added. “There is little agency oversight and companies may keep their actions and information hidden from public view. They just make money.”
Restoring This Rich Legacy
According to Niles, the story of the horseshoe crab describes the problem.
“The horseshoe crab feeds fish populations with its ecosystem-supporting, annual spawn. This provides abundant resources for the businesses of the rural community. The fast recovery of a depleted horseshoe crab population would be best for the public, and a recent study shows it can happen in less than a decade,” Niles said.
“The united interests of the conservation public can turn this around in 10 years,” he stressed. “One decade of not killing horseshoe crabs, saving forage fish from low-profit exploitation, better control of finfish harvest, and restoring marsh and beach habitats would restore this rich legacy.”
To contact Karen Knight, email kknight@cmcherald.com.