Graham et at: Prosomal-width-to-weight relationships for Limulus polyphemus 
237 
72°0'0"W 71°0'0"W 70°0'0"W 
Figure 2 
Sites sampled for horseshoe crabs during the Horseshoe Crab Research Center (HCRC) trawl survey of inshore 
continental shelf waters between New York and Virginia (n = 50 sites) and from spawning surveys in New Jersey 
and Delaware (i.e. , Delaware Bay), and New Hampshire (i.e.. Great Bay), and from the Delaware commercial fishery 
(i.e., Delaware Bay). 
crabs. The ground gear on the flounder net was modi- 
fied with a Texas sweep, which has a chain line in- 
stead of a footrope, to effectively sample horseshoe 
crabs (Hata and Berkson, 2003; Hata and Berkson, 
2004). We recorded prosomal width (to the nearest 1 
mm), weight (to the nearest 10 g), sex, and maturity 
stage for all or a subsample of horseshoe crabs at each 
site. Maturity stage was classified into two groups: 
immature and mature. Male horseshoe crabs without 
modified pedipalps (claspers) were considered imma- 
ture and those with modified pedipalps were consid- 
ered mature (Hata and Berkson, 2004). Females with 
mating scars (i.e., indentations and abrasions on the 
dorsal surface of the opisthosoma resulting from the 
attached male) were categorized as mature. Maturity 
stage in newly molted females is not morphologically 
distinct, therefore some individuals had to be probed 
with an awl for evidence of eggs and determine the 
stage of maturity (Leschen et al., 2006). Females with 
eggs were categorized as mature (Hata and Berkson, 
2004). 
Prosomal-width-to-weight relationship 
We log-transformed the PW and weight measurements 
collected during the HCRC trawl survey and used a 
general linear model (PROC GLM, SAS, vers. 9.1, SAS 
Inst., Inc., Cary, NC) to test for significant differences 
in the PW, weight, and PW-weight relationship between 
sexes and maturity stages. The P-value of each family of 
comparisons was adjusted using a Bonferroni correction 
to protect the experimental-wise error rate. 
We combined all data (i.e., three spawning surveys, 
Delaware commercial fishery, HCRC trawl survey) to 
develop PW-weight regression equations for each group 
(i.e., mature males, mature females, immature males, 
