Download The Horseshoe Crab

The Horseshoe Crab
An Ecological Keystone in Delaware Bay
Outline
• Life history
• Ecological significance of the species
• Uses throughout history
– From Native American to big industry
• Current uses and issues surrounding the
species
• Ongoing research to alleviate pressures
on the species
In the beginning…
• Lineage pre-dates the dinosaur era
– Pre-dates flying insects
– Pre-dates flowering plants
Eggs and trilobite stage
• 14 day developmenthatching time
• Extremely vulnerable to
predation
Juvenile stage
• Maturing to adulthood
takes about 10 years and
14 molts!
• Ages 1-10 live in
Delaware bay or on the
continental shelf
Adulthood
The Horseshoe Crab Spawn
• Occurring primarily in Spring and Summer
– Activity peaks in June
– Around full and new moons
• Each female may lay up to 88,000 eggs
annually
• Egg predation - the base of the food web
Ecology
• Native range from Maine
to the Yucatan
• Population centered
around Delaware Bay
• Spawn in estuaries
– Need well oxygenated sandy beaches
– Low energy waves
Biological Importance of the
Horseshoe Crab
• Horseshoe crab eggs are important to migratory
birds
• Red knot
– Uses eggs to
refuel on their
journey to the
arctic
– 95,000 visited the Delaware bay in 1989
– Only 16,000 in 2003
Early uses of the Horseshoe Crab
• Native Americans
– Ate muscle tissue
– Used telsons as spear tips
– First to use horseshoe crabs as fertilizer
• Early Americans
– 1800’s - collection for farm use as fertilizer or
hog or poultry feed
The first over-harvest
• Between 1920’s to the 1950’s harvest
exploded as the fertilizer business went big
Current uses
• Population rebounded from the 50’s to the
80’s
• LAL and the medical industry
• With horseshoe crabs abundant again…
– Use as bait in the eel and whelk industries in
the late 1980’s
Biomedical uses
• Limulus amebocyte lysate
(LAL)
– A suite of proteins that
aggressively gel in the
presence of bacterial
endotoxins
– Ensures the sterility of
intravenous drugs and
medical devices to be
placed in the body
The biomedical
industry is
required to
release the
horseshoe crabs
back into the wild
after bleeding.
Studies show
only 10%
mortality.
Declining crab populations
http://www.dnrec.state.de.us/fw/hcrabs/larry%20niles%20presentation.pdf
Inconsistent data collection
ASFMC - Horseshoe Crab 2004 Stock Assessment Report
Why the rapid decline?
• While the biomedical industry catches and
releases, the eel and whelk fisheries are a
100% mortality harvest.
– 1 female crab per eel pot
– 1-2 male crab per whelk pot
Managing the horseshoe crab
• 1998 ASMFC multi-state management plan
– No harvest limits recommended (lack of data)
– DE and NJ voluntarily reduced limits
• Addendums I-III
– Established a horseshoe
crab sanctuary at the mouth
of the Delaware bay
– Created a quota transfers
between states
– Created a closed season
during peak spawning
Current harvest
moratorium for both
Delaware and New
Jersey waters
Ongoing research
• Artificial bait for both eel and whelk
– Find out why horseshoe crabs are so effective
at catching both eel and whelk
• Core questions
– Are the attractants the same for both species?
– If not, isolation of the attractant from the
horseshoe crab becomes even more difficult.
Laboratory bioassays
• Whelk
– Modified
trap design
Drain
Eel traps
– Flume
tank
design
Water input
• Eel
The road ahead
• Hope to have a preliminary bait in the
water by April/May 2007
– Field trials during this time to refine bait
• Attractant
• Delivery matrix
Questions?