Silver Human Practices
The Plight of the Horseshoe Crab
Horseshoe crabs aren’t just used for bait. If you have every had a flu shot, known someone with a pacemaker or joint replacement, or given your pet a rabies vaccination, a debt of gratitude is owed to the horseshoe crab. All of these devices are quality checked for safety using a test that comes from the blood of the horseshoe crab. The blood of the crab is very sensitive to endotoxins, the blood from the crab is used commercially to develop the LAL and TAL test. The Limulus amebocyte lysate (LAL)test and was commercialized in the United States in the 1970s and in Asia, there is a similar test called TAL which takes its name from an Asian species of crab, Tachypleus tridentatus. Each year, almost half a million living horse crabs are use in the development of these pharmaceuticals- for these tests 30 percent or more of the blood of the horseshoe crab is taken. It is estimated that 10-15% of 500,000 crabs harvested on the Atlantic coast do not survive the bleeding process. The market for LAL is approximately $50 million, and since no synthetic substitute has the same accuracy as LAL, crab blood must be used it is just to important not to use.
Commercial Fishing
The best bait to attract eel and whelk, best known as conch, is horseshoe crabs. During the 1990s, harvest of the horseshoe crab increased coastwide, with a peak of nearly six million pounds in 1997. This swift increase in harvesting lead to the Atlantic States Marine Fisheries Commission representing 15 states from Maine to Florida to develop a horseshoe crab management plan. The ASMFC plan, was meet with vigorous opposition from commercial fishers, the plan, supported by conservation groups, was implemented in 2001. The plan established a state-by-state harvest quotas and establish a 1500-square mile federal horseshoe crab sanctuary in Delaware Bay. Despite restrictive measures taken in recent years, populations are not showing immediate increases. Mainly, because horseshoe crabs do not breed until they reach nine or more years of age, so as of now there has been no measurably increase.
Biomedical Use
Horseshoe crabs aren’t just used for bait. If you have every had a flu shot, known someone with a pacemaker or joint replacement, or given your pet a rabies vaccination, a debt of gratitude is owed to the horseshoe crab. All of these devices are quality checked for safety using a test that comes from the blood of the horseshoe crab. The blood of the crab is very sensitive to endotoxins, the blood from the crab is used commercially to develop the LAL and TAL test. The Limulus amebocyte lysate (LAL)test and was commercialized in the United States in the 1970s and in Asia, there is a similar test called TAL which takes its name from an Asian species of crab, Tachypleus tridentatus. Each year, almost half a million living horse crabs are use in the development of these pharmaceuticals- for these tests 30 percent or more of the blood of the horseshoe crab is taken. It is estimated that 10-15% of 500,000 crabs harvested on the Atlantic coast do not survive the bleeding process. The market for LAL is approximately $50 million, and since no synthetic substitute has the same accuracy as LAL, crab blood must be used it is just to important not to use.
Environmental Impact
Limuli play a vital role in the ecology of estuarine and coastal communities. Horseshoe crabs utilize autochthonous and allochthonous production from pelagic and benthic food webs. The horseshoe crab is an important part of many vertebrate predators diet. Benthic fish feed on horseshoe crab eggs and larvae, sharks feed on the smaller juveniles, and sea turtles feed on adults (Botton et al. 2003). Horseshoe crabs are dietary generalists, and adult crabs are ecologically important bivalve predators in some locations. The most notable predator–prey relationship involving horseshoe crabs is the migratory shorebird–horseshoe crab egg interaction.Eleven species, such as the more familiar red knot and the dowitcher, rely on horseshoe crab eggs for sustenance during their migration along the Atlantic Flyway. It is estimated that migrating birds may require 539 metric tons of eggs to full the trip to the Arctic summer range. Horseshoe crabs link an array of prey (bivalves and polychaete worms) and predators (fish, turtles, and birds), utilizing both autochthonous and allochthonous production from pelagic and benthic food webs.
Sources
Botton ML Shuster CN Jr Keinath J . 2003. Horseshoe crabs in a food web: Who eats whom. Pages. 33-153. in Shuster CN Jr, Barlow RB, Brockmann HJ, eds. The American Horseshoe Crab . Cambridge (MA): Harvard University Press.
Carmichael RH Rutecki D Annett B Gaines E Valiela I . 2004. Position of horseshoe crabs in estuarine food webs: N and C stable isotopic study of foraging ranges and diet composition. Journal of Experimental Marine Biology and Ecology . 299: 231-253.
Castro G Myers JP . 1993. Shorebird predation on eggs of horseshoe crabs during spring stopover on Delaware Bay. The Auk . 110: 927-930.
“Species Profile.” ASMFC Fisheries Focus. Vol 17, Issue 5. July 2008. .