Blog by Joe Reynolds, Coastal Naturalist
Photo by Joe Reynolds.
Intro by Alison M. Jones, NWNL Director: To honor last week’s Endangered Species Day, we’re posting Joe’s blog on horseshoe crabs which are “Near-Threatened” per Endangered Species International.
My children grew up on Long Island Sound mesmerized by the spring tide of these prehistoric, armored invertebrates. Since they’re now rarely seen on those shores, I couldn’t resist a bit of further research and adding some Editorial Notes!
Author and coastal naturalist Joe Reynolds is also an activist — and he can count. NWNL applauds his monitoring of these “upside-down skillets with tails.” I look forward to joining his next full-moon count in Raritan Bay! Check Joe’s blog with pictures, video and stories of wildlife from Sandy Hook Bay, Raritan Bay and Lower New York Bay: http://www.nyharbornature.com
“Selfie” provided by Joe Reynolds.
WHAT’S HAPPENING UNDERFOOT?
Watch where you step this spring! Horseshoe crabs (Limulus polyphemus) are beginning to crawl ashore on beaches around Sandy Hook Bay, Raritan Bay, Jamaica Bay, and other shallow estuarine sites around New York Harbor. They mate on full and new moon evenings in May and June.
Yet another spawning season for horseshoe crabs has commenced, an annual rite of spring that goes back 450 million years. For Jurassic Park movie fans, that’s 230 million years before the first dinosaur! [Ed note: They even survived the Permian extinctions when 95% of all marine species disappeared.)
Known as “living fossils,” horseshoe crabs are harmless, ancient creatures effectively unchanged through time. Horseshoe crabs are more closely related to spiders and scorpions than to crabs. However, as marine arthropods, they are really a prehistoric family of animals unto themselves.
In late April, horseshoe crabs begin to migrate from deeper ocean waters into estuaries to breed. First on the beach are often males, waiting for available females. What follows is like a primitive singles bar, minus a colorful tiki bar. But alcohol isn’t needed here.
Photo by Joe Reynolds.
When a single female crab crawls out of the surf, she releases chemical cues called “pheromones” that help attract a breeding male. He then grasps her from behind with special appendages shaped like tiny boxing gloves on the end of his front walking legs. With her male in tow, she moves through the intertidal zone – a beach area that is above water at low tide and under water at high tide. There they deposit and fertilize 60,000 to 120,000 lime-green eggs in batches in wet sand.
In 2 to 4 weeks the eggs hatch. The size of a human fingernail, the young are a near–replica of an adult, though tail-less. The small crabs head straight to the water where they will grow in sandy shallow areas of the estuary. It takes 8 to 12 years for a crab to sexually mature and migrate back to bay beaches to breed.
THE VALUE OF HORSESHOE CRABS
Who would guess horseshoe crabs are critical to migratory shorebirds? But, yes, the fatty eggs of horseshoe crabs provide an important food source for many migratory shorebirds, including red knots (Calidris canutus), ruddy turnstones (Arenaria interpres), and sanderlings (Calidris alba), as they pause in their northward journeys to breed in the Arctic.
[ED Note: The red knot (part of the sandpiper family) makes one of the longest migrations of any bird: 15,000 km (9,300 mi) from Tierra del Fuego in S. America to the Arctic. On their mid-Atlantic stop, they re-energize and fatten up by feasting on what was a superabundant supply of horseshoe crab eggs. Red knots were numerous in N. America until masses were shot in the 1880’s. With further declines since the 1960’s, they are a “threatened species,” per the Endangered Species Act. So healthy horseshoe crab populations are critical to red knot survival. (Citation: http://www.audubon.org/field-guide/bird/red-knot)]
Red knot. Photo by Dick Daniels, in Creative Commons.
STEWARDS STUDYING THEIR DECLINE
Although the world’s largest spawning horseshoe crab populations are in Delaware Bay, the busy New York Harbor has crabs too. Few people welcome them; but those that do, know when and where to find them by the dozens, hundreds, or even thousands along the shore.
Our Bayshore Regional Watershed Council is an environmental group dedicated to improving water quality and restoring the wildlife habitat of Raritan Bay and Sandy Hook Bay. Since 2009, our volunteers have counted horseshoe crab populations along the southern shore of NY Harbor in Monmouth County, NJ. Our goal is to note their spawning population and ascertain if it is stable, increasing or decreasing.
Volunteers tagging a horseshoe crab to monitor its New York Harbor location. Photo provided by Joe Reynolds.
So far our study shows a horseshoe crab population that is less than robust. There’s been a steady decline in adult females. In 2009, the Watershed Council counted 495 female crabs (singles and mating) across 1,000 feet of beach at five sites in Raritan and Sandy Hook Bays. Yet, in 2016 only 217 female crabs were counted at the same sites. (Ed: minus 50% in 7 years). The single female population decreased from 96 to 15 during this time period. (Ed: minus 85%)
Surprisingly, male populations are growing. In 2009, there were 679 male crabs at monitoring locations (single and mating) in Raritan and Sandy Hook Bays. This increased in 2016 to 1,016 (Ed: plus about 75%). The single males also increased: from 251 to 769 (Ed: plus 300%)
This great inequality between sexes affects their spawning. It takes two to make a baby! Swimming pairs (crabs seeking a place to lay eggs) decreased from 265 in 2009 to 130 in 2016 (Ed: minus 50% in 7 years). Burrowed pairs (crabs in the process of laying eggs) decreased from 276 to only 50 pairs in 2016. (Ed: minus 80%)
Lemon Creek Park, Staten Island, NY, on the Raritan Bay. Photo by Alison M. Jones.
HUMAN OVER-HARVEST of HORSESHOE CRABS
What could cause such a dire decline in females? Humans and money, of course. Increased harvesting of horseshoe crabs in NY waters threatens their population. NY is the only state on the U.S. Atlantic Coast without a horseshoe-crab harvest moratorium during their breeding period.
Females are repeatedly harvested more than males since they are about 30% bigger and thus have more meat. Adult females also often carry eggs, which will make better bait.
Since 2009, NY State’s commercial quota for horseshoe crabs has been around 150,000 crabs. Some come from NJ’s Raritan Bay and the south shore of Long Island. But an undetermined amount of crabs in NY Harbor are being harvested illegally.
In 2013, two men from Brooklyn were arrested for stealing 200 horseshoe crabs from an island locally known as the Ruffle Bar in Jamaica Bay, Queens. They were charged with taking wildlife without a permit and disturbing wildlife breeding practices in a National Park.
On April 30, 2017, a woman was arrested in Jamaica Bay for illegally harvesting 7 horseshoe crabs. She told U.S. Park Police she was harvesting crabs for her business. The body parts of horseshoe crabs command a high price in some parts of the world since they are considered an aphrodisiac for men.
Horseshoe crabs are also used as bait for the American eel and channel whelk (aka conch) which are highly valued by Asians and Europeans. U.S. harvesters use body parts of female horseshoe crabs as bait for eel and whelk. Thus female horseshoe crabs are supplying global seafood needs. In 20 years, the price for 1 horseshoe crab has jumped from 25 cents to over $5.
Photo by Joe Reynolds.
Horseshoe crabs are also harvested by the medical industry for their copper-based blood which turns blue when exposed to air. Horseshoe crab blood has remarkable antibacterial properties that insure no impurities exist in medicines. The U.S. Food and Drug Administration (FDA) requires all intravenous drugs, vaccines and medical devices that come in contact with the human body (i.e., replacement hips, hearts, knees or pacemakers) to be tested by crab’s blood for bacterial toxins associated with toxic shock syndrome, meningitis and typhoid. Millions in the US survive each year due to the clotting characteristics of horseshoe crabs’ blue blood.
Unfortunately medical benefits for humans don’t benefit the crabs. Horseshoe crabs are to be caught; bled with about 30% of their blood taken; and then returned to waters where they were found. But according to author Alexis Madrigal, “Between 10 and 30 percent of the bled animals, according to varying estimates, actually die.” In addition, “bleeding a female horseshoe crab may make it less likely to mate, even if it doesn’t kill it.” (The Blood Harvest, The Atlantic, Feb 26, 2014)
Environmental scientists John Tanacredi and Sixto Portilla say many crabs taken from NY waters to be bled are often not returned to NY. Research on horseshoe crabs from Brooklyn to Montauk from 2003 to 2014 showed that numerous crabs harvested in NY and taken to MA to be bled were often released in local Cape Cod waters, not NY as required by permits. “Many of those animals are re-harvested for bait and sold back to NY fishermen at an average cost of $5/crab.” (Horseshoe Crab Biology, Conservation and Management, 2015)
South Beach on Raritan Bay Estuary, Staten Island, New York. Photo by Alison M. Jones.
IMPACTS OF HARVESTING HORSESHOE CRABS
It’s not an easy life in New York Harbor. The legal and illegal harvesting of horseshoe crabs, especially females, has limited their distribution and breeding, resulting in localized population declines. Horseshoe crabs could disappear locally if nothing is done to safeguard them in NY waters.
NJ instituted a moratorium on harvesting horseshoe crabs in 2007, but not NY where people can still harvest crabs. This puts the crab population under severe threat in the Lower New York, Raritan and Sandy Hook Bays.
Tagged horseshoe crab. Photo by Joe Reynolds.
YOU CAN HELP!
Please email both Governor Cuomo (click here) and the NY State Department of Environmental Conservation (click here) to ask for greater protection of horseshoe crabs. NY State must restrict harvests in local waters, especially of female crabs. We need Albany to protect these prehistoric animals — before it’s too late.
Also, please share the plight of horseshoe crabs with friends and family. The more who are aware of the threat to horseshoe crabs, the more likely we can ensure their survival in the Raritan, Sandy Hook and Jamaica Bays.
If greater awareness and public support is coupled with greater conservation efforts, then these Ancient Mariners of New York Harbor can fill the beaches for many spring seasons to come. Let’s make sure they endure for another 450 million years!
Fisherman at confluence of eastern shore of Cheesequake Creek Inlet with Raritan Bay, Raritan River Basin, New Jersey. Photo by Alison M. Jones.
NWNL Recommended Reading:
Safina, Carl. The View from Lazy Point: A Natural Year in an Unnatural World. New York: Henry Holt and Company, 2011. One hundred miles east of NY’s Manhattan, the author found a beach house that let him “see the whole world in the view from Lazy Point” – or at least the whole beauty and connected magic of the natural world in which we live. In this renowned conservationist’s observations and pleas for us to adopt a “sea ethos,” he tells of spawning, antedeluvian horseshoe crabs, bluefish, sea ducks and menhaden. He also weaves in tales from afar of brown bears and coral reefs to further deepen our appreciation of nature.
Sargent. Bill. Crab Wars: A Tale of Horseshoe Crabs, Bioterrorism and Human Health. Lebanon NH: University Press of New England, 2006. Social justice and ethics are raised by human medical needs for the blood of these crabs that evolved 300 million years ago. This is a tale of the conflicts between scientific progress and our dwindling natural resources.
For children, Grades 1-4: Crenson, Victoria. Horseshoe Crabs and Shorebirds: The Story of a Foodweb. New York City: Two Lions, 2014. With charming watercolor illustrations, this book shares nature’s amazing connections between a small red-chested bird from the southern tip of S. America with the salty eggs of large, armored crabs on mid-North Atlantic beaches.
Joe Reynolds Recommended Reading:
Fredricks, Anthony D. Horseshoe Crab: Biography of a Survivor. Washington, DC: Ruka Press, 2012.
Cramer, Deborah. The Narrow Edge: A Tiny Bird, An Ancient Crab & An Epic Journey. New Haven, CT: Yale University Press, 2015.
McCully, Betsy. City at the Water’s Edge: A Natural History of New York. New Haven, CT: Rivergate Press, 2006.
Waldman, John. Heartbeats in the Much. Guilford, CT: The Lyons Press, 2000.
MacKenzie, Clyde L. The Fisheries of Raritan Bay. New Brunswick, NJ: Rutgers University Press, 1992.