When I was a kid, I often walked to the Indian River Lagoon and just stood there in amazement watching the hundreds, if not thousands, of baby horseshoe crabs winding their way through the sands. They left circular trails, crossing over and over again…
Where were they going? What were they doing? Why were there so many?
Every once in a while, I would pick one up and place it carefully in the palm of my hand. Its sharp tail and prickly feet pushed against me. I watched in wonder at its strength as it bent in half. Once returned to the sand, the little crab went back to work immediately as if nothing had happened at all.
My mother had told me the horseshoe crabs were more ancient than the dinosaurs and had been here “forever.” “They are living fossils” she would say. “And they can live over 20 years and take 10 years just to mature.”
Although I picked them up with such care, today, forty years later, when I try to find them, they’re gone.
What happened to the horseshoe crabs of the Indian River Lagoon? How did a creature so ancient, resilient, and prevalent almost “disappear?”
Although there is quite a bit of literature on the Central Indian River Lagoon, I could not find much on the Southern Lagoon. Some of the best documentation came from Gretchen S. Ehlinger and Richard A. Tankersley. On line, they are cited multiple times for their paper “Reproductive Ecology of the American Horseshoe Crab, Limulus Polyphemus, in the Indian River Lagoon: An Overview.” I was also able to read “Evaluation of the Horseshoe Crab Fishery in the Indian River Lagoon Using Catch Data From Two Power Plants,” and a September 2014 “FPL Cape Canaveral Energy Center Horseshoe Crab Deterrent Fence Specifications” publication.
All of these lead to the following observations: decline of the species has been noted for around three decades. There have been UME’s or “Unexplained Mortality Events” where up to a 100,000 have died in the same area around the same time.
Factors that are related to their overall decline in the lagoon include intense coastal development, shoreline breeding grounds destruction, and unbridled human population growth; expansion of agriculture drainage watersheds into the IRL; deteriorating water quality; power plants sucking up as many as 100,000 a year into their intake canals; and over-fishing. The crabs are used as bait, collected for marine purposes, and more recently captured live and bled for their “blue-blood”that is invaluable to human health.
Unfortunately, for many years, the value and importance of the horseshoe crab was not recognized. For instance, Ehlinger and Tankersley note a one year study in the early 2000s at two Indian River Lagoon power plants that recorded a total of 39,097 crabs trapped on the intake screens at Cape Canaveral, and 53,121 at the Orland Utilities Plant. The scientists also mention a previous study from 1975 that estimated 69,662 at the Canaveral Plant, and 104,000 trapped annually at the Orlando Utilitility’s Indian River plant. “This alone could easily account for a decline in the Indian River population.” (Ehlinger and Tankersley 2007)
The St Lucie Power Plant located here in the southern lagoon did not agree to be part of the study and there is very little research one can now find on the subject.
In any case, the good news is that just recently the Cape Canaveral plant has installed a wall to protect the horseshoe crabs and science’s recognition of the species has people wanting them to come back.
The Florida Wildlife Commission notes:
“Horseshoe crabs are extremely important to the biomedical industry because their unique, copper-based blue blood contains a substance called “Limulus Amebocyte Lysate”, or “LAL”.This compound coagulates in the presence of small amounts of bacterial toxins and is used to test for sterility of medical equipment and virtually all injectable drugs. Anyone who has had an injection, vaccination, or surgery has benefitted from horseshoe crabs!”
…”in March 2000, a series of management measures for horseshoe crabs went into effect in Florida. The regulations required a license to harvest and set a limit on the number of animals each licensee could harvest per day (25 to 100 animals allowed per day per person depending on the permit). In 2002, a biomedical permitting rule created a mechanism to allow for biomedical collection.”
Personally, looking at these photos of the horseshoe crabs being bled is like a science fiction movie to me. Never as a kid would I have imagined my little friends with needles in their heads being milked for their blood.
….But if this is what is going to save them… I must say, if they could talk, I bet now is the strangest part of their 450 million year journey. In my mind, they will always be free and drawing circles in the sand.
Ehlinger and Tankersley: http://www.horseshoecrab.org/research/sites/default/files/DONE%20Ehlinger%20and%20Tankersley.pdf
FPL wall to protect marine life, central lagoon:
St Lucie Power Plant effects on IRL and environment: https://www.nrc.gov/docs/ML0214/ML021430397.pdf
Changing Global Perspectives on Horseshoe Crab Biology and Conservation Management: https://www.kobo.com/at/en/ebook/changing-global-perspectives-on-horseshoe-crab-biology-conservation-and-management
Bleeding Horseshoe Crabs for Human Health: http://www.americanpharmaceuticalreview.com/Featured-Articles/167236-The-Incredible-Horseshoe-Crab-Modern-Medicine-s-Unlikely-Dependence-on-a-Living-Fossil/
Ehlinger and Tankersley Links: