NOTE Walls and Berkson: Effects of blood extraction on Limulus polyphemus 



459 



10% during the first year after bleeding, and 11% during 

 the second year. Thompson (1998) estimated that mortal- 

 ity associated with LAL processing was 15% during the 

 first week following blood extraction by observing bled and 

 unbled horseshoe crabs in tanks in South Carolina. 



Each LAL producer has a unique bleeding method, meth- 

 od of capture, distance and method of travel to the bleed- 

 ing laboratory, a different holding time and conditions, and 

 method of return of the bled crab that is most appropriate 

 to that company's setting and situation. The results found 

 in this study reflect those of BioWhittaker and may not be 

 reflective of other companies' procedures. 



We examined the survival of the horseshoe crabs in a 

 controlled environment (tank), as opposed to their natural 

 environment. Our survival rate for horseshoe crabs may 

 not reflect the survival rate of horseshoe crabs returned 

 to the wild. Transfer and holding processes induce stress 

 on the horseshoe crabs. Thus, the survival of the bled 

 horseshoe crabs could be compromised by translocation 

 and confinement in tanks. However, the tank environment 

 may provide protection for horseshoe crabs when they are 

 in a weakened state and are more susceptible to predation 

 following blood-extraction. 



Further, this study looked only at newly matured male 

 horseshoe crabs in an attempt to minimize variation of ex- 

 ternal influences, so that the only difference between the 

 two groups was whether or not they underwent the blood 

 extraction process. Additional studies should examine dif- 

 ferences in mortality in other age and sex classes. 



The Food and Drug Administration estimates that 

 260,000 horseshoe crabs were caught, bled, and returned 

 by biomedical companies when last reported in 1997 

 (HCTC^). Assuming the 7.5% mortality rate found in 

 our study is applicable to each biomedical company, and 

 assuming that the number harvested for the biomedical 

 companies has stayed relatively constant, we estimate 

 that approximately 18,750 horseshoe crabs die yearly as 

 a result of the biomedical procedure. In comparison, the 

 commercial fishery reported landings of 5,543,000 pounds 

 in 1999 and 3,756,000 pounds reported in 2000, all with a 

 100% mortality rate (NMFS, 2002). In the overall picture 

 of the magnitude of horseshoe crabs caught and the associ- 

 ated mortality rates, it is evident that the bleeding process 

 has a substantially smaller impact than the commercial 

 fishery on the horseshoe crab population. However, infor- 

 mation on both biomedical and commercial fishery-induced 

 mortality are necessary to determine the total harvest mor- 

 tality of horseshoe crabs. 



The information presented in this study provides an 

 estimate of the postbleeding mortality rate, an element 



^ HCTC (Horseshoe Crab Technical Committee). 1998. Status 

 of the horseshoe crab (Limulus polyphemus) population of the 

 Atlantic coast, 9 p. + figures and tables. Horseshoe Crab Tech- 

 nical Committee, Atlantic States Marine Fisheries Commission. 

 Washington, D.C. 



of human-induced mortality on horseshoe crabs. This is 

 one critical piece of information required to conduct a 

 stock assessment and to develop an effective management 

 strategy. 



Acknowledgments 



The authors wish to thank Carl N. Shuster Jr. and William 

 McCormick for their helpful advice on the design of this 

 study. Michael Schwarz, Ryan Cool, and Michael Jahnke 

 of the Virginia Seafood Agricultural Research and Exten- 

 sion Center, a unit of Virginia Tech, provided the facilities 

 for holding the horseshoe crabs and maintained them. 

 Funding for this study was provided by BioWhittaker, 

 a CAMBREX company. We especially thank Tammy 

 Newcomb and Michael Vaughan for their helpful advice 

 throughout all stages of this study. 



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