John Page Williams, Senior Naturalist, is
one of the Chesapeake Bay Foundation’s
longest-serving staff members.
device reduced the harvest for bait enough to meet the
commission’s guidelines for sustainability.
Ironically, U.S. human population growth causes other
harvest pressure. It turns out that the horseshoe crabs’ blood
amebocytes (like our white blood cells) are highly sensitive to
contaminants and clot around them to disable them. Since the
1970s, medical providers have used an extract of horseshoe
blood for testing every injectable or implantable healthcare
product, such as a vaccine (or my new right shoulder joint)
to make sure it is free from bacterial contaminants that can
cause serious reactions from our immune systems.
There are watermen on the Atlantic coast that fish for
horseshoe crabs for medical use. Technicians at specialized
labs bleed the crabs through the membrane in the joint
between the two body sections. Then the watermen take
them back out for release in the area where they were
caught, after marking them to avoid recapture for a year to
allow them to rebuild their blood supplies. There are four
companies producing the extract—one each in Virginia,
Maryland, Massachusetts, and South Carolina. The problem
with this otherwise lifesaving fishery is that crab release
mortality is about 15 percent, despite highly refined handling
and extraction procedures. At present, harvest mortality is
sustainable in South Carolina, Virginia, and Maryland but above
ASMFC’s management threshold in New England. Moreover, as
our population grows and ages, the demand for testing grows.
No wonder a race is on to develop a synthetic alternative, but
there is none in sight yet.
Why do we want to make sure our horseshoe crabs survive
and prosper? For one thing, because they have as much a
right to be here as we do, with millions of years of history
behind them. In that time, they have fitted into our oceans’
food webs, tapping the vast benthic food source and
providing food for other creatures. In our part of the Atlantic,
their major large predator is the loggerhead sea turtle. But
there is more. Let’s return to those shorebirds.
Part of the Food Web
Horseshoe crabs bring calories, proteins, and high-energy
oils from ocean and Bay floor to the shore, where they lay
prodigious numbers of eggs, more than needed for the species
to survive. Spring mating season occurs around the full moons
of May (the 29th this year) and June (the 28th this year), in
high tides along the beaches. This timing coincides with the
amazing long-range migrations of at least eleven species of
sandpipers, plovers, and other shorebirds such as the red knot,
en route from South American wintering grounds to northern
latitudes, including the Arctic. Mid-Atlantic beaches offer
these birds stopovers for high-calorie feeding on horseshoe
crab eggs in a loud frenzy remarkable to behold. Cape May,
New Jersey, at the mouth of Delaware Bay, attracts the
greatest numbers of crabs and birds, but there are plenty more
sites there and around the Chesapeake.
This drama will be playing out as you read this issue of
Save the Bay.