polyphemus, in Pleasant Bay, Massachusetts

Transcription

1 Estuaries Vol. 27, No. 2, p April 2004 Magnitude of Harvest of Atlantic Horseshoe Crabs, Limulus polyphemus, in Pleasant Bay, Massachusetts DEBORAH RUTECKI, RUTH H. CARMICHAEL*, and IVAN VALIELA Boston University Marine Program, Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts ABSTRACT: Atlantic horseshoe crabs, Limulus polyphemus, are currently harvested for biomedical, scientific, and bait purposes. In recent years, changes in population abundance and magnitude of harvesting have raised concerns about the status of this resource. We found horseshoe crab harvest in Pleasant Bay, Massachusetts, was selective by sex and size. Biomedical harvest preferred larger individuals and females, the scientific harvest preferred smaller individuals and males, and the bait harvest preferred females. Total harvest for all purposes accounted for the mortality of 12% the adult population. Biomedical harvest accounted for the greatest loss of horseshoe crabs from Pleasant Bay, 11.6% of the total population. Although biomedical harvest had the lowest associated mortality rate ( 1015%), many more crabs were harvested from Pleasant Bay for biomedical purposes than for other uses. The scientific harvest accounted for the mortality of 0.4% of the population, and bait harvest accounted for the smallest mortality at 0.06% of the population. Harvest mortality rate was estimated to be lower in Pleasant Bay than in other Cape Cod areas and may be lower than natural mortality in the population. This study is the first qualitative investigation of commercial harvest on horseshoe crab populations and emphasizes that harvest pressures on different populations need to be individually evaluated. Introduction The Atlantic horseshoe crab, Limulus polyphemus, is found on the western Atlantic continental shelf and in estuaries from Maine to Yucatan (Shuster 1982). Mature horseshoe crabs migrate from deeper waters to low energy intertidal beaches to spawn from MarchJuly (Shuster and Botton 1985). Horseshoe crabs have high fecundity, with high egg and larval mortality (Loveland et al. 1996; Carmichael et al. 2003). They mature slowly, requiring 911 yr to reach sexual maturity (Shuster and Botton 1985; Sekiguchi 1988). Adult horseshoe crabs live to at least 19 yr of age (Botton and Ropes 1988) with a relatively low natural mortality (Loveland et al. 1996). Human activity generally accounts for the greatest mortality among adult horseshoe crabs (Atlantic State Marine Fisheries Commission [ASMFC] 1998) since spawning animals are readily accessible for harvesting from intertidal beaches and by trawling. Horseshoe crabs were hand-harvested and ground for use as fertilizer and livestock feed from the mid-1800s until the mid-1950s (Berkson and Shuster ). On average, an estimated 1.2 million horseshoe crabs were harvested annually in Delaware Bay between the 1870s and the 1920s (Fig. 1; Shuster and Botton 1985; Shuster 1996). A decline in Delaware Bay horseshoe crab abun- * Corresponding author; tele: 508/ ; rherrold@ bu.edu dance took place from the 1930s1960s (Fig. 2 top), coincidental with continuous intensive harvesting (Shuster and Botton 1985; Shuster 1996, ). During the 1970s some recovery in horseshoe crab abundance was seen in this population after a period of decreased harvest (Berkson and Shuster ). From some Cape Cod towns tried to eradicate horseshoe crabs, thought to be a predator of commercially important shellfish, by paying $0.03 bounties for horseshoe crab telsons (Fig. 2 middle; Harding 1961; Novitsky 1984). Today, horseshoe crabs are harvested for biomedical, scientific, and bait purposes. BIOMEDICAL INDUSTRY The biomedical industry harvests horseshoe crabs to obtain Limulus Amoebocyte Lysate (LAL). LAL is a clotting compound found in horseshoe crab blood cells that is a globally-used standard to test for pathogenic bacterial endotoxins (Novitsky 1984; ASMFC 1998). The number of horseshoe crabs harvested for the biomedical industry has nearly doubled from to since 1989 (ASMFC 1998). The biomedical industry may preferentially harvest female crabs with the assumption that they furnish more lysate (U.S. Fish and Wildlife Service [USFWS] 2002) because females are on average larger than males (Shuster 1982). As per regulations existing up to, bled crabs were released back into their native waters, typically within 72 hr of collection (Novitsky 1984) Estuarine Research Federation 179

2 180 D. Rutecki et al. Fig. 1. Harvested horseshoe crabs stacked on Bowers Beach, Delaware before being processed for fertilizer. Photo taken June 1924 (Delaware State Archives). Mortality of bled and released crabs is reportedly 815% (Rudloe 1983; Thompson 1998; Walls and Berkson, 2003). Other reports have suggested up to 20% mortality (Kurz and James-Pirri 2002), but results were inconclusive and these studies did not use crabs bled and released by biomedical facilities. SCIENTIFIC COLLECTION Horseshoe crabs harvested for scientific research are used as biomedical models in vision, cell biology, neurobiology, immunology, biochemistry, and drug development (Marine Biological Laboratory unpublished data). The number of horseshoe crabs harvested along the Atlantic coast for scientific and educational purposes is unknown (ASMFC 1998). 100% mortality is typically associated with scientific horseshoe crab collection since animals are usually sacrificed for research. Scientific collection may harvest more male horseshoe crabs than females because the isolation of optic nerve fibers is more difficult in gravid females (Passaglia et al. 1998). BAIT HARVEST Horseshoe crabs are used as bait in the whelk (Busycon sp.) and American eel (Anguilla rostrata) fisheries. Horseshoe crab use as bait reportedly increased from 7.2 t in 1970 to 3,100.5 t in 1998 (Fig. 2 bottom; ASMFC 1998; National Marine Fisheries Service [NMFS] ). Females are preferred for use as bait (ASMFC 1998) because they provide bait for one to four pots, whereas males provide bait for one to two pots (Manion et al. ). Eel fishermen also prefer egg-laden females due to the presumed chemical attractants found in the eggs (Ferrari and Targett 2003). There is growing concern among coastal resource managers and the public about the magnitude of crab harvests and impact of harvests on Fig. 2. Top: Estimated adult horseshoe crab abundance in Delaware Bay from the 1870s to 1990s (Shuster 1996). Data are the averages for each decade and were compiled from federal fisheries commercial harvest data and spawning surveys 1979 (Shuster ). Middle: Numbers of horseshoe crabs reported for bounty by the towns of Chatham, Orleans, and Harwich for most years from 1954 to 1968 for crabs from Pleasant Bay, Massachusetts (Annual Report of the Town of Chatham, Massachusetts reports of the shellfish warden ). Data for are not available. Bottom: Approximate United States commercial horseshoe crab landings, 1970 (ASMFC 1998; NMFS ). data are preliminary (NMFS unpublished data). population structure (Shuster 1996; ASMFC 1998; Berkson and Shuster ). Horseshoe crab abundance in Delaware Bay decreased by an order of magnitude between 1970 and 1990 (Michels 1996; Shuster 1996; Swan et al. 1996). Other data have been interpreted to show steep declines in other Atlantic coast areas, including Cape Cod, Massachusetts (Widener and Barlow ). No studies have examined the effect of commercial harvest on population structure. Sex ratios among natural populations have been suggested as a means of monitoring shifts in population structure that may result from sex-selective harvest (Shuster 1996). Most of the available data on horseshoe crab populations have been collected in Delaware Bay, with limited studies in other loca-

3 Harvest of Limulus polyphemus 181 TABLE 1. The total number of days crabs were delivered, number of days sampled, and total and average number of barrels of horseshoe crabs observed on sampling days at the biomedical producer, Associates of Cape Cod, from MayOctober during the harvest season. The average number of barrels day 1 for August was calculated by averaging the number of barrels observed on July and September sampling dates. Month Total Estimated Delivery Days Number of Sampling Days Number of Barrels Total Average Day 1 May June July August September October Fig. 3. Location of Pleasant Bay on Cape Cod, Massachusetts. The Cape Cod National Seashore boundary ( ) (RMP 1998), nearby Stage Harbor (a), and Barnstable Harbor (b) are also shown. tions, and the majority of research has focused on spawning populations (ASMFC 1998). While these studies provide valuable information on the movements and annual numbers of spawning individuals, they do not provide comprehensive data regarding the effect of harvesting on population abundance and structure. Scientific and bait harvest mortality and the impacts of total harvest on population structure and reproductive success are unknown. Pleasant Bay, the largest estuary on Cape Cod (Fig. 3), has an existing spawning population (Carmichael et al. 2003) with a history of harvest including bounties for telsons (Fig. 2 middle) and has been the site of biomedical, scientific, and bait hand-harvests since 1975 (Abrew 1975; Pleasant Bay Resource Management Plan (RMP) 1998). Harvests from Pleasant Bay are quantifiable from data available through the cooperation of the Associates of Cape Cod (ACC), the sole biomedical user of horseshoe crabs in this area, and the Marine Biological Laboratory (MBL), the sole user of Pleasant Bay crabs for research purposes. In addition, the Division of Marine Fisheries (DMF) of the Commonwealth of Massachusetts keeps records of bait harvest. Horseshoe crabs also have been harvested from other embayments on Cape Cod, including nearby Stage Harbor and Barnstable Harbor (Fig. 3; F. Germano personal communication). The purpose of this study was to determine the magnitude of the horseshoe crab harvest from Pleasant Bay, what segment of the horseshoe crab population is affected by each harvest, how harvest might affect the structure and reproductive success of the Pleasant Bay population, and to compare harvest pressure in Pleasant Bay with harvest pressure in two other Cape Cod embayments. Methods ESTIMATION OF HARVESTS We estimated harvest of horseshoe crabs in Pleasant Bay, for biomedical, scientific, and bait purposes between mid-may to mid-november. Biomedical Harvest To estimate the number of horseshoe crabs harvested for biomedical use, we evaluated catch brought into ACC. We collected data during 19 dates across the duration of the collecting season for ACC (MayOctober ). Horseshoe crabs are brought into ACC in large barrels each day during the collecting season. To estimate the number of horseshoe crabs taken during each sampling date, we counted crabs in approximately four randomly selected barrels to be able to calculate mean number of crabs per barrel, and counted the total number of barrels brought into the facility (Table 1). We then multiplied the mean number of crabs per barrel (25 4 crabs) by the number of barrels to estimate a total catch for each sampling date. To extrapolate the per-day harvest data obtained at each sampling day to the total seasonal catch, we multiplied the daily rate by the number of days

4 182 D. Rutecki et al. that horseshoe crabs were delivered to the ACC for each month during which harvest took place (Table 1). We then added the total monthly harvests across the season. For each step of these calculations we propagated error associated with averaged values according to Meyer (1975). To compare our estimated harvest to previous harvests, we obtained data on the number of crabs harvested for biomedical use from Pleasant Bay in (Harrington unpublished material). To assess whether the harvest targeted males and females, or animals of different size, we recorded sex and size of sampled crabs during each sampling day. We determined sex of adult horseshoe crabs by presence or absence of subchelate pedipalps (Loveland and Botton 1992) and the structure of genital pores (Shuster 1982; Sekiguchi 1988). To determine horseshoe crab size, we measured prosomal width (PW) (Riska 1981; Shuster 1982) to the nearest 1 mm. Scientific Harvest To determine the magnitude of scientific harvest from Pleasant Bay, collection data for to were obtained from Edward Enos at the Marine Resources Center, MBL, Woods Hole, Massachusetts. To see if collection of horseshoe crabs for scientific purposes selected for sex and size of horseshoe crabs, we recorded sex and size in the catch brought into the MBL facilities once a month from JuneNovember. Data was taken for 46.8% of the crabs harvested for scientific purposes, and extrapolated to the entire annual catch. Bait Harvest To determine the bait harvest from Pleasant Bay, we contacted the Massachusetts DMF and obtained the number and sex of horseshoe crabs landed for bait from, since we were unable to obtain information by directly interviewing individual fishermen. During these years, the DMF determined harvested areas and horseshoe crab use through catch reports (Germano personal communication). These data are available because state law requires fishermen to report monthly landings to the DMF. The data reports do not include size information for the bait harvest. HARVEST PRESSURE AND MORTALITY To obtain a rough estimation of the harvest relative to the stock of horseshoe crabs we simply compared the magnitude of harvest versus the existing population in Pleasant Bay. To extend the comparison beyond Pleasant Bay, we also report similar comparisons for two other estuaries. To assess harvest pressure and mortality in Pleasant Bay, we compared the magnitude of harvest for TABLE 2. Number of male and female horseshoe crabs harvested for biomedical, scientific, and bait purposes from Pleasant Bay in. Propagated standard error is provided for estimates of biomedical harvest. Males Females Total Biomedical Scientific Bait Total 11,180 2,665 43,245 10,277 54,425 12,942 1, , ,788 43,616 56,404 biomedical, scientific, and bait purposes from to the population data of Carmichael et al. (2003). We estimated harvest mortality using an expected loss of 1015% for the biomedical industry (Rudloe 1983; Thompson 1998; Walls and Berkson ), and assumed 100% mortality for scientific and bait harvests, except in when 300 crabs from the scientific harvest were returned to the Bay. We used the 1015% harvest mortality for our calculations to represent the most conservative estimates based on the entire biomedical process. To compare harvest pressure and mortality between Pleasant Bay and other Cape Cod areas, we collected data available in the Massachusetts DMF records for for two nearby embayments, Stage Harbor and Barnstable Harbor. Total population abundance for horseshoe crabs has not been determined for Stage and Barnstable Harbors; we assumed these embayments are capable of supporting the same density of crabs as Pleasant Bay. We compared the reported harvest for the three estuaries by adjusting the catch relative to area of the three different estuaries. There is no scientific harvest from Stage and Barnstable Harbors, and no data were available on biomedical harvest. Hence, our comparison is conservative since biomedical harvest, if any in these other areas, would increase harvest pressure compared to Pleasant Bay. Results HARVEST IN The biomedical industry accounted for the greatest number of horseshoe crabs harvested from Pleasant Bay in (Table 2). This harvest occurred from MayOctober and peaked during JulySeptember (Fig. 4 top). Scientific collection was the second largest harvest in Pleasant Bay and occurred from JuneNovember (Fig. 4 middle). The bait harvest was the smallest harvest taken from Pleasant Bay in (Fig. 4 bottom). Different segments of the Pleasant Bay horseshoe crab population were harvested for biomedical, scientific, and bait purposes. The biomedical harvest included more females than males (Fig. 4 top) with a male to female ratio of 0.3:1 (Fig. 5

5 Harvest of Limulus polyphemus 183 Fig. 4. Number of horseshoe crabs harvested for biomedical (top), scientific (middle), and bait (bottom) use each month for the Pleasant Bay harvest season. Error bars represent propagated error calculated from the standard deviation in the number of crabs per barrel and the number of barrels per day. No error was reported for the scientific and bait harvests since they were reported harvests and not estimated. Bait harvest data are from the Massachusetts Division of Marine Fisheries. Fig. 5. Size (prosomal width) frequency distribution of horseshoe crabs measured from the biomedical (top) and scientific harvests (middle), and from the natural population (bottom) (Carmichael et al. 2003). For each panel, mean PW is given for males (dark arrows) and females (light arrows), along with the total number of males and females and the sex ratio of sampled horseshoe crabs. The areas represent the PW range at which horseshoe crabs in Pleasant Bay reach sexual maturity. top). The animals harvested for this purpose were adults with a PW larger than 181 mm; males had a mean PW of mm ( SD) and females had a mean PW of mm (Fig. 5 top). The scientific collection always harvested an equal or greater number of males compared to females (Fig. 4 middle), with a male to female ratio of 8.3:1 (Fig. 5 middle). Harvested adult males had a mean PW of mm and harvested females had a mean PW of mm (Fig. 5 middle). Crabs harvested for scientific purposes overlapped in size with juveniles observed in the natural population (Fig. 5 middle). Juveniles represented approximately 0.8% of the scientific harvest. The bait harvest showed a male to female ratio of 0.5:1 (Fig. 4 bottom), indicating bait collectors harvested more female horseshoe crabs. Horseshoe crabs collected for biomedical and scientific purposes differed by size, with crabs collected for the biomedical industry being the largest. To determine whether crabs harvested for each purpose were selected significantly by size, we compared size of harvested crabs between industries and to crabs in the general population of Pleasant Bay (mean male PW of mm, mean female PW of mm). Males and females harvested for the biomedical industry were significantly larger than those harvested for scientific purposes and in the natural population (Table 3). Males harvested for scientific purposes were significantly smaller than males from the natural population. No significant difference was found between the females harvested for scientific purposes and the females of the natural population (Table 3). Hence, horseshoe crabs harvested for the biomedical industry are among the largest individuals in the Pleasant Bay population, while males harvested for scientific purposes are among the smallest.

6 184 D. Rutecki et al. TABLE 3. Results of Fisher s Protected Least Significant Difference (PLSD) post hoc tests done after one-way analysis of variance comparing mean prosomal widths of male and female horseshoe crabs harvested for biomedical and scientific purposes and in the general population in Pleasant Bay. n.s. not significant. p Value Fisher s PLSD Comparisons ( 0.05) Biomedical versus scientific Biomedical versus natural population Scientific versus natural population Males Females n.s. MAGNITUDE OF REMOVAL RELATED TO POPULATION NUMBER To roughly assess the amount of population loss due to harvest, we compared the biomedical, scientific, and bait harvest from Pleasant Bay relative to the total adult population ( individuals) in Pleasant Bay (Carmichael et al. 2003). The and total horseshoe crab harvests in Pleasant Bay resulted in the loss of approximately % of the adult population each year (Table 4). We estimated this loss by summing losses calculated from each individual harvest. The biomedical industry harvested approximately horseshoe crabs in, and in, representing 8.5% and 10.9% of the total population respectively (Table 4), with harvest mortality estimated at 1% of the population in and 2% TABLE 4. The number of crabs harvested, number lost due to harvest mortality, and percentage males and females lost from the total Pleasant Bay population due to harvest for biomedical, scientific, and bait purposes from. Juveniles harvested in the scientific collection were not included in these calculations. * indicates the Marine Resources Center returned 300 of these crabs to Pleasant Bay. indicates no data available. Year Biomedical Scientific Bait Total Number of crabs harvested 42,500 54,425 2,392 2,956* 1,708 Harvest mortality Total no. of crabs lost 4,2506,375 5,4438,164 Percentage of males lost Percentage of females lost ,392 2,656 1, Percentage of total crabs lost , , ,156 56,404 7,6069,731 7,42210, in (Table 4). The scientific collection harvest was approximately the same in and, representing about 0.5% of the population. Harvest declined in to 0.35% of the population, with 100% mortality, scientific harvest accounted for a % loss of the total population in Pleasant Bay. The bait harvest in Pleasant Bay declined by 86% between and. Assuming that the declared harvest represented the actual take, we calculated that the 100% mortality associated with these harvests resulted in loss of % of the population in these years. Pleasant Bay had an intermediate harvest pressure and the lowest harvest mortality rate relative to the other two estuaries for which we obtained harvest data (Table 5). Although the bait harvest pressures in Stage and Barnstable Harbors declined since, Stage Harbor had the highest harvest pressure and harvest mortality from. Barnstable Harbor had the lowest harvest pressure, but an intermediate mortality rate during these years. Discussion The biomedical harvest was considerably larger than the scientific and bait harvests in Pleasant Bay (Table 4). The Pleasant Bay biomedical harvest represented approximately 22% of the horseshoe crabs harvested by the biomedical industry along the Atlantic coast relative to the biomedical harvest of animals from the entire geographic range of the horseshoe crab (Manion et al. ). The relatively lower mortality (Table 5) in Pleasant Bay compared to harvest losses in the two other Cape Cod areas that have larger bait harvests results from the fact that biomedical crabs harvested from Pleasant Bay were returned to the water after bleeding. Scientific collection was the second largest harvester in Pleasant Bay (Fig. 4). The ASMFC considers harvest for scientific purposes to be minimal along the Atlantic coast (ASMFC 1998), but in Pleasant Bay, due to proximity of the Woods Hole scientific community, this harvest resulted in a higher removal than the bait harvest (Table 4). This result emphasizes that harvest pressures need

7 Harvest of Limulus polyphemus 185 TABLE 5. Horseshoe crab harvest pressure (number taken ha 1 ) and resulting harvest mortality (number lost ha 1 ) from for three Cape Cod areas. Data for Stage Harbor and Barnstable Harbor were provided by the Massachusetts Division of Marine Fisheries and represent bait landings only. indicates no data available. Number of Crabs ha 1 Harvest Location Total Area (ha) Harvest Mortality Harvest Mortality Harvest Mortality Pleasant Bay Stage Harbor Barnstable Harbor 2, , to be individually evaluated for horseshoe crab populations. Assessment at an embayment level along the Atlantic coast is necessary for regional and local management plans to further address the harvest intensity and sustainability in their areas. The bait harvest in Pleasant Bay declined because of several factors: the ASMFC mandatory 25% reduction in harvest, the closure of the eastern part of Pleasant Bay within the Cape Cod National Seashore (Fig. 3) to harvesting, and the use of bait bags by as much as 55% of the conch fisherman in Massachusetts (Germano personal communications) to potentially reduce bait catch by about 50% (Fisher unpublished data). The ASMFC mandated reduction in horseshoe crab harvest resulted in the decline of the Massachusetts horseshoe crab harvest from in to in (USFWS 2002; Germano personal communication). In addition, shifting sand and shallow water make navigating difficult in Pleasant Bay, especially at night, the time when most bait harvest occurs in this region. These navigational difficulties have made alternative locations more appealing than Pleasant Bay, including nearby Stage Harbor and Monomoy Island, which are easier to navigate (Germano personal communication). The biomedical, scientific, and bait industries harvested different size segments of the horseshoe crab population (Fig. 5) and selectively removed more female than male horseshoe crabs from Pleasant Bay (Table 4). The biomedical industry restricts harvest to animals larger than 181 mm, to avoid harvesting juvenile crabs (Novitsky personal communication). This size limit occurs at the mid to large end of the male size distribution and the small end of the female size distribution in the natural population (Fig. 5). Females are more likely to be harvested by the biomedical industry, as demonstrated by the large differences in sex ratio of the biomedical catch (0.3:1) compared to that of the natural population (2.3:1) (Carmichael et al. 2003). Selective harvesting of larger female horseshoe crabs could impact horseshoe crab fecundity if the number of eggs that a female produces varies with size or harvest stress. More research is needed on horseshoe crab fecundity to further address this issue. Although more females than males were harvested for the biomedical and bait harvests, it does not appear to have resulted in a substantial change in the sex ratio among adult horseshoe crabs in Pleasant Bay in the last several decades. A male to female ratio 2.5:1 was recorded among adult crabs in Pleasant Bay in 1953 (Shuster 1955), when there was no commercial harvest or crab bounty. This historical sex ratio was similar to the current sex ratio of 2.3:1 (Carmichael et al. 2003). These observations suggest that the natural horseshoe crab sex ratio may not be 1:1 in Pleasant Bay. The maledominated sex ratio observed in the Pleasant Bay adult horseshoe crab population may be related to another factor differentially affecting mortality between sexes. An example of such a situation is the reported differential mortality associated with continued male molting in spider crabs which show a 1:2.4 female-dominated sex ratio (Tester and Carey 1986), very similar to the sex ratio of adult horseshoe crabs in Pleasant Bay. Carmichael et al. (2003) found that female horseshoe crabs may molt more times throughout life than males, possibly explaining the male-dominated sex ratio in this population. The current harvest mortality in Pleasant Bay (Table 4) may be lower than natural mortality associated with spawning and disease. In 1986 Delaware Bay may have lost 10% of the adult horseshoe crab population ( crabs) in beach strandings during the spawning season (Botton and Loveland 1989). In 1977 a disease-related mass mortality event occurred at Slaughter Beach, Delaware. The loss appeared to equal the 1977 breeding population ( crabs) (Bang 1979; Shuster and Botton 1985). These losses are much greater than the 12% harvest mortality estimated for Pleasant Bay. Since natural mortality due to stranding and disease varies (Penn and Brockmann 1995), further investigation is needed to determine how natural mortality in the Pleasant Bay horseshoe crab population may compare to harvest mortality reported here.

8 186 D. Rutecki et al. Attempts at managing horseshoe crab populations need to reflect the harvest rates and population structures and abundances present. Horseshoe crab populations in other Cape Cod embayments with higher harvest pressure and mortality than Pleasant Bay, may be more greatly affected by commercial harvesting than the population in Pleasant Bay. Information is needed on the population abundance and structure, magnitude of harvest, and characteristics of crabs harvested in individual embayments to inform local management decisions. This study is the first qualitative investigation of commercial harvest on horseshoe crab populations and emphasizes that harvest pressures need to be individually evaluated for horseshoe crab populations on an embayment level. Similar data on harvested populations in other areas could be used to evaluate harvest impacts coast-wide and help managers assess what level of harvest may be sustainable, protecting the coast-wide horseshoe population while allowing continued access to this important multiple-use resource. ACKNOWLEDGMENTS This work was supported by the Friends of Pleasant Bay and the Boston University Humes Alumni Award. We thank Thomas Novitsky, Mick Dawson, Roger Withers, and the staff at the Associates of Cape Cod, Edward Enos and staff at the Marine Biological Laboratory, Marine Resources Center for cooperating in the assessments of the biomedical and scientific harvests, and Frank Germano at the Massachusetts Division of Marine Fisheries for information and insight into the Massachusetts harvests. We also thank Dr. Carl Shuster for providing difficult to acquire literature and Sara Grady and Brendan Annett who provided needed field assistance. LITERATURE CITED ABREW, K. 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9 Harvest of Limulus polyphemus 187 Crab Forum: Status of the Resource. University of Delaware Sea Grant College Program, Lewes, Delaware. SHUSTER,JR., C. N.. Two perspectives: Horseshoe crabs during 420 million years, worldwide, and in the past 150 years in the Delaware Bay area, p In J. T. Tanacredi (ed.), Limulus in the Limelight. Kluwer Academic/Plenum Publishers, New York. SHUSTER, JR., C. N. AND M. L. BOTTON A contribution to the population biology of horseshoe crabs, Limulus polyphemus (L.), in Delaware Bay. Estuaries 8: SWAN, B. L., W. R. HALL, JR., AND C. N. SHUSTER, JR Annual survey of horseshoe crab spawning activity along the shores of Delaware Bay: summary, p In J. Farrell and C. Martin (eds.), Proceeding of the Horseshoe Crab Forum: Status of the Resource. University of Delaware Sea Grant College Program, Lewes, Delaware. TESTER, P. A. AND A. G. CAREY Instar identification and life history aspects of juvenile deepwater spider crabs, Chionoecetes tanneri Rathbun. Fishery Bulletin 84: THOMPSON, M Assessments of the population biology and critical habitat for the horseshoe crab, Limulus polyphemus, in the South Atlantic Bight. M.S. Thesis, University of Charleston, Charleston, South Carolina. U.S. FISH AND WILDLIFE SERVICE (USFWS) Monomoy National Wildlife Refuge compatibility determination draft. February. Eastern Massachusetts National Wildlife Refuge Complex, Sudbury, Massachusetts. WALLS, E. A. AND J. BERKSON.. Effects of blood extraction on the mortality of the horseshoe crab, Limulus polyphemus. Virginia Journal of Science 51: WALLS, E. A. AND J. BERKSON Effects of blood extraction on horseshoe crabs (Limulus polyphemus). Fisheries Bulletin 101: WIDENER, J.W.AND R. B. J. BARLOW.. Decline of a horseshoe crab population on Cape Cod. Biological Bulletin 197: SOURCES OF UNPUBLISHED MATERIALS FISHER, R. Unpublished Data. Commercial Fisheries Specialist, Virginia Institute of Marine Science, College of William and Mary, Williamsburg, Virginia GERMANO, F. Personal Communication. Massachusetts Division of Marine Fisheries, Pocasset, Massachusetts HARRINGTON, J.. Declaration of Jay Harrington, U.S. District Court, District of Massachusetts, Civil Action No. 00-CV RWZ. MARINE BIOLOGICAL LABORATORY. Unpublished Data. Marine organisms at the MBL database. index.html NMFS. Unpublished Data. Commercial Fisheries Landings database. NOVITSKY, T. Personal Communication. Associates of Cape Cod, Falmouth, Massachusetts Submitted, October 25, 2002 Revised, June 11, 2003 Accepted, July 17, 2003