485 



Abstract — Adult horseshoe crabs 

 (Limulus polyphemus) are the pre- 

 ferred bait in the U.S. east coast 

 whelk pot fishery, but their harvest 

 is being restricted because of severe 

 population declines in the Chesa- 

 peake and Delaware bays. To identify 

 other baits, the activity in the pal- 

 lial nerve of whelks was determined 

 during exposure of the osphradium 

 to odorant solutions prepared from 

 horseshoe crab eggs, horseshoe crab 

 hemolymph, and hard clam (Merce- 

 naria mercenaria) tissue. All three 

 elicited significant responses; bait 

 based on them may provide an alter- 

 native to the use of adult horseshoe 

 crabs, although extensive behavioral 

 testing remains to be done. Channeled 

 whelk did not respond to molecular 

 weight fractions (>3 kDa and <3 kDa) 

 prepared from horseshoe crab egg 

 odorant solutions but did respond 

 when the molecular weight fractions 

 were recombined. Whelks appear to 

 have broadly tuned chemoreceptors 

 and manufactured baits may need to 

 mimic the complex mixture of odor- 

 ants derived from natural sources. 



Activity in the pallial nerve of knobbed 

 iBusycon carica) and channeled 

 (Busycotypus canaliculatum) whelks 

 recorded during exposure of 

 the osphradium to odorant solutions 



Christopher Magel 



Virginia Institute of Marine Science 



P.O. Box 1346 



Gloucester Point, Virginia 23062 



Kirstin Wakerield 



Nancy Targett 



College of Marine and Earth Studies 

 University of Delaware 

 Lewes, Delaware 19958 



Richard Brill (contact author) 



Email address for R. Brill; rbrill (gvims.edu 



National Marine Fisfieries Service 



National Oceanic and Atmospheric Administration 



Northeast Fisheries Science Center 



Present address: Virginia Institute of Marine Science 



P.O. Box 1346 



Gloucester Point, Virginia 23062 



Manuscript submitted 13 February 2007 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 23 May 2007 by the Scientific Editor. 



Fish. Bull. 105:485-492 (2007). 



Knobbed and channeled whelks [Busy- 

 con carica and Busycotypus canalicu- 

 latum, respectively) are common in 

 inshore areas of the east coast of the 

 United States from Georgia to Mas- 

 sachusetts (Walker, 1988) and form 

 the basis of a substantial commercial 

 fishery. The currently preferred bait 

 in the pot fishery is adult horseshoe 

 crabs (Limulus polyphemus) (Fer- 

 rari and Targett, 2003). The directed 

 harvesting for bait has contributed to 

 severe population declines of horse- 

 shoe crabs in the Chesapeake and 

 Delaware bays (Berkson and Shuster, 

 1999) and increasingly stringent catch 

 restrictions are being implemented. 

 These restrictions include a morato- 

 rium on horseshoe crab harvest from 

 Delaware Bay (issued by the Delaware 

 Department of Natural Resources and 

 Environmental Control and the New 

 Jersey Department of Environmental 

 Protection in 2006). These restric- 

 tions are being promulgated in large 



measure because horseshoe crab eggs 

 are a primary food source for migra- 

 tory shorebirds, such as the red knot 

 iCalidris canutus), during their north- 

 ward spring migrations (Tsipoura and 

 Burger, 1999; Weidensaul, 2006). 

 Because of a continuing decline in the 

 breeding population of the red knot 

 (Morrison et al., 2004), the species 

 has been proposed for inclusion on the 

 Endangered Species List (Weidensaul, 

 2006). 



Work is underway to create alter- 

 native bait for the whelk pot fish- 

 ery (Ferrari and Targett, 2003). As 

 part of these efforts, the sensitivities 

 of knobbed and channeled whelks 

 to odorant solutions prepared from 

 horseshoe crab eggs, horseshoe crab 

 hemolymph, and hard clam (Merce- 

 naria mercenaria) tissue were exam- 

 ined. Odorant solutions prepared from 

 horseshoe crab eggs, and molecular 

 weight fractions of these, were tested 

 because they have been reported to 



