October 23, 2013 at 2:55 am #719MikeKeymaster
Horseshoe crab decline puzzles scientists
By Hoa Nguyen
Published June 19 2005
Before dinosaurs roamed the land, horseshoe crabs crawled the ocean
floor, always emerging on the beach this time of year to reproduce.
Few things have changed over the eons for the living fossil with the
distinctive armor-like shell, but recently, researchers have notice a
decline in their numbers that is worrisome.
“They’re really hard to kill,” said Jennifer Mattei, a professor and
biology department chairman at Sacred Heart University in
Fairfield. “They’re in decline and we don’t know why. That tells
people something is wrong.”
The decline had been noticed anecdotally, but first got the attention
of researchers in the late 1990s in Delaware Bay. One of the crabs’
predators, red knot shorebirds, weren’t visiting the bay to gorge on
horseshoe crab eggs as often as they had in the past. The bay had
been an annual feeding ground for the red knots, which double in size
to prepare for their long flight back north for the summer.
“One hypothesis is the birds are going to other places for food,”
said Brad Spear of the Atlantic States Marine Fisheries Commission, a
quasi-governmental group that gets funding from the federal
government and from 15 participating states to help manage marine
resources in the region.
That’s when researchers noticed that the absence of red knots seemed
to be linked to the dwindling horseshoe crab population.
In 1998, marine officials developed the first management plan for
horseshoe crabs, said Spear, who helped coordinate the interstate
“Population declines in one area may have an effect in other areas,”
In addition to asking states to monitor the horseshoe crab
population, the plan further limited the number of horseshoe crabs
that people could harvest. Crabs are harvested for use as bait in
conch and eel fishing and for the pharmaceutical industry, which
extracts the blood from the crab and use it to test for bacterial
contamination in drugs. The crab’s blood can be made to clot in the
presence of bacteria and is the fastest and most reliable way to
ensure intravenous drugs are bacteria-free.
In Connecticut, which also is a breeding ground for the crabs,
harvesting isn’t as popular as in other states, but there is evidence
the state has fewer horseshoe crabs than it once did.
Researchers said many people who live on the Connecticut coast have
stories about horseshoe crabs piled up on beaches in years past.
Although most people agree there are fewer crabs on the beaches now
than in past decades, researchers have little data beyond one or two
population surveys that catalog a broad swath of species along the
ocean floor. Horseshoe crabs aren’t researched much, probably because
they are so abundant and don’t have the economic value that seafood,
such as lobsters, do.
The data that do exist suggest that in the past few years, the
population may be slowly increasing in western Long Island Sound and
starting to recover in other parts of Connecticut.
“The numbers are going up,” said Penny Howell, senior fisheries
biologist for the Department of Environmental Protection. But this
isn’t necessarily good news. “Going up doesn’t mean great,” she
said. “The population in the ’60s and ’70s were far higher than they
In the past several years, Howell has been working to shore up better
population figures of the horseshoe crabs, recruiting volunteers to
help count them in different areas of the state.
The Greenwich Conservation Commission will be one of the volunteer
groups holding a horseshoe crab count this week at Greenwich Point
This time of year, horseshoe crabs come onto the beach. Female crabs
will find a spot to lay their eggs. Male crabs follow and pass over
the eggs to fertilize them.
“More of them will be on the beach during the full moon and the new
moon,” Mattei said, adding that the crabs use the full moon as their
There will be a full moon Tuesday night.
During mating season, female horseshoe crabs are in charge, while
male crabs cruise around looking for the right mate to hook onto.
He has special claws, they kind of look like boxing gloves,” Mattei
said. “He hooks onto the back of her shell.”
The pair can crawl around the ocean floor for about a month before
coming onto the beach to reproduce, she said.
Mattei is trying to advance her understanding of the animals’
behavior beyond their mating habits. She has been tagging horseshoe
crabs since 1998 to try to track them. So far, only a fraction of the
tagged crabs have yielded phone calls from people who have found them.
“We had some crazy returns,” she said of the Connecticut crabs she
tagged that have been found. A New York City park ranger found one in
Brooklyn, another was found in Rhode Island and a third crab tagged
in Milford was later spotted by a boy on Long Island.
With such limited data, many unanswered questions remain about the
animals, including how long they live. Researchers estimate that it
takes about 10 years for a crab to mature, but they guess that the
life expectancy is about 20 to 25 years, Mattei said.
“Do the adults come back to the same beach or do they disperse
randomly?” she asked. “We don’t even know how far they travel.”
Perhaps the most important unknown is whether their dwindling numbers
are an indication of a larger problem in the environment, and if so,
“They’ve survived everything,” Mattei said of the crabs. “I would
hate to see humans wipe them out.”
The forum ‘Strange Animal Deaths’ is closed to new topics and replies.