American Horseshoe Crabs, Limulus polyphemus, in : Open Possibilities

Jaime Zaldı´ var-Rae, Rene´ Elı´ as Sapie´ n-Silva, Martha Rosales-Raya, and H. Jane Brockmann

Abstract Little is known about Mexican Limulus polyphemus, the southern- most population of the species. We present an overview of work on Mexican horseshoe crabs, their situation, and perceived threats and opportunities regarding the conservation of the species. Horseshoe crabs occur along the western, northern, and eastern coasts of the Yucata´ n peninsula, and are geneti- cally distinct from populations in the United States. Spawning aggregations and nests are found continuously throughout the year, commonly in protected lagoons where mangrove (Rhizophora mangle, Laguncularia racemosa, Avicen- nia germinans, and Conocarpus erectus) and sea grass (Thalassia testudinum) communities proliferate. Populations are thought to be dwindling since the 1960s and Limulus is listed as ‘‘in danger of extinction’’ in Mexican legislation since 1994. The most important localities are within protected areas. Direct exploitation is not an important threat, but coastline modification (especially of mangrove areas and coastal lagoons) for housing and tourism is a major concern. Additional potential threats are the oil industry and shrimp fishery in the southern , but their effects on horseshoe crab populations have not been assessed.

1 Introduction

Knowledge about the biology and ecology of Mexican Limulus polyphemus, the southernmost population of the species, is scant (Escalante et al. 1980; Gomez-´ Aguirre 1980; Bonilla-Gonza´ lez et al. 1986; Anderson and Shuster 2003). This chapter aims at providing an overview of the available information on the biology of horseshoe crabs in Mexico and our perspective on potential threats and opportunities for the study and conservation of these animals in Mexico.

J. Zaldı´ var-Rae (*) Laboratorio de Conducta Animal, Instituto de Ecologı´ a, Universidad Nacional Autonoma´ de Me´ xico, AP 70-275, CP 04510, Coyoaca´ n, Me´ xico, DF, Me´ xico e-mail: [email protected]

J.T. Tanacredi et al. (eds.), Biology and Conservation of Horseshoe Crabs, 97 DOI 10.1007/978-0-387-89959-6_6, Ó Springer ScienceþBusiness Media, LLC 2009

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1.1 The Study of Limulus polyphemus in Mexico: A Historical Account

The first description of horseshoe crabs in the Western world was provided by Friar Diego De Landa (1566; translated by Tozzer 1941) in his ‘‘Account of the Things of Yucata´ n.’’ Although he classified it as a fish, he clearly described the round shell, slender tail, and many legs of the horseshoe crab and used its Mayan name ‘‘Mex.’’ He also stated that the only edible part of the animal was its eggs, which were eaten by the Mayans. The next written accounts of Mexican horseshoe crabs date from the late 19th century. In them, Milne- Edwards (1879) and Ives (1891) mentioned that horseshoe crabs were abundant along the southern west coast of the Yucata´ n Peninsula in the Laguna de Te´ rminos, , and along the northern coast of Yucata´ n at Dzilam. Their presence along the coasts of the Yucata´ n Peninsula was later confirmed by Zarur-Menez (1961), Ramı´ rez et al. (1963), Gomez-Aguirre´ (1979), and Bonilla-Gonza´ lez et al. (1986). Occasional sightings in , on the western portion of the Gulf of Mexico, were reported by Cha´ vez and Mun˜ oz-Padilla (1975). Gonza´ lez-Guzma´ n et al. (1967), at the National Autonomous University of Mexico (UNAM), described the cytology of hemolymph collected from horseshoe crabs of Laguna de Te´ rminos, Campeche, and correctly inferred a role for amebocyte granules in the coagulation of hemolymph. Gonza´ lez-Guzma´ n et al. (1967) got their specimens from Dr. Samuel Gomez-Aguirre´ of UNAM’s Institute of Biology, who had begun his pioneer- ing work with populations in the southern Gulf of Mexico in 1964. Dr. Gomez’s´ interest in L. polyphemus spanned 40 years until his passing in 2006, and his work included the first calls for attention to a decline in Mexican horseshoe crab populations (Gomez-Aguirre´ 1979, 1980, 1983, 1985, 1993, 2002). Dr. Gomez´ also led several groups of Mexican biology students in the first morphometric studies of the species and quantified exuviae, dead, and live individuals along the coasts of the Yucata´ n Peninsula (Bonilla-Gonza´ lez et al., 1986; Barba- Macı´ as et al., 1988; A´ lvarez-An˜ orve et al., 1989; Gomez-Aguirre´ 1993; Gomez-Aguirre´ and Ya´ n˜ ez-Martı´ nez 1995). He also provided the first descrip- tions on particular aspects of the biology of Mexican horseshoe crabs (e.g. Gomez-Aguirre´ and Flores-Mora´ n 1987; Gomez-Aguirre´ et al., 1992).

2 Distribution and Habitat

Mexican populations of L. polyphemus are restricted to the coasts of the Yucata´ n Peninsula, between about 188N and 218N (Cha´ vez and Mun˜ oz-Padilla 1975; Gomez-Aguirre´ 1979; Va´ zquez-Garcı´ a and Villalobos-Figueroa 1980; Bonilla-Gonza´ lez et al., 1986), with rare sightings in Veracruz (Cha´ vez and Mun˜ oz-Padilla 1975; Fig. 1). In 1985, Dr. Gomez-Aguirre´ and his students found a population on the northern shore of Bahı´ a de la Ascension´ in Quintana

[email protected] American Horseshoe Crabs, Limulus polyphemus, in Mexico 99

Fig. 1 Distribution of American horseshoe crabs, Limulus polyphemus, in Mexico. Black and gray circles represent localities where mating aggregations have been recorded and localities where live or dead individuals or exuviae have been observed, respectively. Localities: LT=Laguna de Te´ rminos; 1= Isla Aguada, Cabrera and Isla Pa´ jaros; 2=Icahao and Champoton;´ 3=City of Campeche; 4=Isla Arena and Celestu´ n; 5=Progreso and Yucalpete´ n; 6=Dzilam de Bravo; 7=San Felipe and Rı´ o Lagartos; 8=Holbox; 9=Cancu´ n; 10=Bahı´ade la Ascension´

Roo, on the Caribbean coast of the Peninsula (Bonilla-Gonza´ lez et al., 1986), confirming an anecdotal account by Shuster (1979). This observation contra- dicts the speculation that the strong northward flowing Yucata´ n Current and the very narrow continental shelf on the Caribbean coast might prevent south- ward migrations from northern localities (Anderson and Shuster 2003). Most Mexican localities for horseshoe crabs are within coastal lagoons. Although rivers are scarce in the Yucata´ n Peninsula (Fig. 1), large volumes of underground fresh water flow into these coastal lagoons and create estuarine systems. Red, black, and white mangrove and buttonwood (Rhizophora mangle, Laguncularia racemosa, Avicennia germinans, and Conocarpus erectus, respec- tively) and vast seagrass beds (predominantly Thalassia testudinum) are com- mon in these coastal lagoons and estuaries, and L. polyphemus are commonly associated with these communities (Gomez-Aguirre´ 1979; Bonilla-Gonza´ lez et al., 1986; Barba-Macı´ as et al., 1988). Indeed, the presence of horseshoe crabs on the Caribbean coast of the Peninsula may be explained by coastal lagoons providing suitable habitats without exposure to strong currents and with the sheltering effect of the Mesoamerican Barrier Reef. These shallow water areas also provide valuable nursery grounds for juveniles, which require many years to mature.

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3 Morphometry

Following the pattern for the species, in Mexico male horseshoe crabs are significantly smaller than females, with inter-sexual size ratios of 0.73–0.80 (based on intergenal distances; RE Sapie´ n-Silva, unpublished data), similar to those observed in the United States (0.75–0.79 based on prosoma widths; Shuster 1979). There are significant differences in size between populations along the coasts of the peninsula: animals from Champoton´ are significantly larger than those from Laguna de Te´ rminos, while the latter are significantly larger than those from the area near Progreso, Rı´ o Lagartos, and Holbox (see Table 1). Differences between populations do not follow a latitudinal pattern (RE Sapie´ n-Silva, unpublished data) as has been described for U.S. populations (Shuster 1979; Riska 1981). Horseshoe crabs from Champoton´ are similar in size to those from Chesapeake Bay measured from Shuster (1979), while those from Rı´ o Lagartos are smaller than those from the Gulf coast of Florida (RE Sapie´ n-Silva, unpublished data). A similar pattern was detected by one of us (HJ Brockmann, unpublished data) upon comparing horseshoe crabs from San Felipe-Rı´ o Lagartos, western Florida, and Delaware Bay (Table 1). If size has a genetic basis, the size differences between Mexican populations may indicate limited gene flow among them.

4 Population Genetics

There seems to be no gene flow between the Yucata´ n populations and those in Florida (Anderson and Shuster 2003). This is supported by the findings from King et al. (2005) that the population at San Felipe-Rı´ o Lagartos (Fig. 1) on the northeastern coast of Yucata´ n is highly genetically differentiated from popula- tions in the United States. The San Felipe-Rı´ o Lagartos population also showed low genetic diversity and heterozygosity, suggesting that geographic isolation, small population size, and inbreeding may have spurred stochastic processes leading to a loss of diversity. King et al. (2005) suggested that the marked genetic differences between the Mexican and United States populations may warrant a taxonomic revision of the genus. An assessment of the genetic structure of Mexican populations has not yet been conducted.

5 Reproduction

In Mexico horseshoe crabs are known to breed from Campeche to northern Quintana Roo, particularly near the mouths of the Laguna de Te´ rminos (Punta Cabrera, Isla Aguada, and Isla Pa´ jaros; Gomez-Aguirre´ 1979; Bonilla-Gonza´ lez, et al. 1986; Rosales-Raya 1999), in the estuarine systems of Celestu´ n, Isla Arena

[email protected] mrcnHreheCrabs, Horseshoe American

Table 1 Sizes of horseshoe crabs from populations in Me´ xico, Florida, and Delaware Laguna de San Felipe-Rı´ o San Felipe-Rı´ o Delaware Measure (cm) Te´ rminosa Champoton´ a Progresoa Lagartosa Holboxa Lagartos b Floridab Bayb Females Prosoma width Mean – – – – – 18.8 21.6 25.5 SE 0.32 0.32 0.27 (N) (39) (30) (50) polyphemus, Limulus Interocular distance [email protected] Mean 11.05 14.0 10.2 10.5 10.4 10.8 13.8 16.1 SE 0.05 0.15 0.75 0.20 0.21 0.20 0.17 0.19 (N) (395) (37) (7) (40) (26) (39) (50) (50)

Males

Prosoma width 101 Mexico in Mean – – – – – 14.0 16.1 20.0 SE 0.14 0.17 0.16 (N) (55) (40) (75) Interocular distance Mean 7.9 9.7 8.3 7.7 7.5 7.7 9.7 12.0 SE 0.04 0.13 0.22 0.10 0.10 0.10 0.11 0.11 (N) (333) (27) (8) (44) (44) (55) (60) (75) aMeasured by R.E. Sapie´ n-Elı´ as from specimens collected in Laguna de Te´ rminos (southern Campeche coast), Champoton´ (central Campeche coast), San Felipe-Rı´ o Lagartos (on the northern Yucata´ n coast), and Holbox Island (northern Quintana Roo coast). bMeasured by H.J. Brockmann from specimens collected in San Felipe-Rı´ o Lagartos, Florida (Seahorse Key, on the west coast of Florida near Cedar Key, Levy County), and Delaware Bay (Bowers Beach, DE). 102 J. Zaldı´ var-Rae et al.

(M Rosales-Raya, personal observations), in the estuarine areas at the mouth of Rı´ o Lagartos (Brockmann, personal observations), on Holbox (R. Salazar- Gonza´ lez, personal communication), and at the mouth of the Champoton´ River (Rosales-Raya 1999). Juveniles were very abundant in the lagoon at Yucalpete´ n (Brockmann, personal observations) (see Fig. 1 for locations of these sites). Mating aggregations were also common in the City of Campeche in the late 1970s and early 1980s, but do not seem to occur nowadays (M Rosales- Raya, personal observations; Fig. 1). In the Yucata´ n Peninsula, horseshoe crabs spawn on small beaches limited by mangroves or on the edges of small man- grove islands. These are generally low-energy beaches with little slope, most of whose area is flooded during high tides. Organic matter abounds in the sub- strate and microbial decomposition is high in these beaches, as indicated by the common characteristic smell of hydrogen sulfide. These generally poor condi- tions for egg development may partly explain why densities of nesting aggrega- tions in Mexico (from tens to a couple hundred pairs at a time in a particular site) and overall abundances are very low in comparison with those in the United States. Also unlike the U.S. populations, Mexican horseshoe crabs seem to spawn throughout the year, at least in the Campeche populations (A´ lvarez-An˜ orve et al. 1989; Barba-Macı´as et al. 1988; Bonilla-Gonza´ lez et al. 1986; Rosales-Raya 1999). Little is known about the reproductive behavior of Mexican horseshoe crabs. Gomez-Aguirre´ et al. (1992) documented the sexual differentiation of a captive male collected in Laguna de Te´ rminos, which emerged from a molt with the first pair of pedipalps modified into claspers with the attenuated fixed claws char- acteristic of virgin males (Gomez-Aguirre´ et al. 1992; Brockmann 2003b). There is no size-based assortative mating in Mexican populations (RE Sapie´ n-Silva, unpublished data) and mating aggregations of many males and one female are uncommon in Mexico. In Laguna de Te´ rminos mating pairs are the rule and two males mating with the same female are rarely seen (RE Sapie´ n-Silva, M Rosales-Raya, personal observations). Horseshoe crabs require 8–10 years to develop from newly metamorphosed juveniles to adults (Shuster and Sekiguchi 2003). Juveniles spend their first 2–3 years in shallow inshore areas just off the breeding beaches, feeding on worms and small mollusks. Juvenile horseshoe crabs were observed in large numbers feeding in a shallow lagoon near Yucalpete´ n, swimming into and out of the lagoon with each high tide cycle (HJ Brockmann, unpublished data). Martha Rosales-Raya (1999) studied the geochemical characteristics of nests in three nesting beaches within the Laguna de Te´ rminos (Isla Aguada, Cabrera, and Isla Pa´ jaros) and one at the mouth of a small stream north of the Champoton´ River (Icahao). The percentage of silt-clay in substrates from these four sites did not exceed 40%, a composition considered suitable for nesting (Sekiguchi et al. 1977; Botton et al. 1988). Water salinity in nests increased with the proportion of silt-clay and very fine sand and consolidation of the substrate, and was as high as 59% in the most consolidated substrates (Isla Pa´ jaros). In addition, anaerobic conditions were common and nests were

[email protected] American Horseshoe Crabs, Limulus polyphemus, in Mexico 103 shallow (exposed to 12.4 cm deep) in these substrates. It was nevertheless puzzling that nest density on Isla Pa´ jaros was higher than in other locations with more benign conditions.

6 Ecological Relationships

There are no studies on the diet of Mexican horseshoe crabs, but several bivalve genera in the Yucata´ n Peninsula (see Garcı´ a-Cubas 1981; Gonza´ lez et al. 1991; and references therein) are likely constituents, based on what is known about horseshoe crab feeding preferences in Delaware and New Jersey (Botton 1984; Botton and Haskin 1984; Botton and Ropes 1989). Bonilla-Gonza´ lez et al. (1986) reported the presence of seagrass, Thalassia sp., leaves in the gut of a female specimen. Although there are no studies on the predators of Mexican horseshoe crabs and their eggs, many species of shorebirds that are known to feed upon horse- shoe crab eggs in spawning beaches of the United States (Wander and Dunne 1981; Botton and Loveland 1993; Clark et al. 1993; Botton et al. 1994, 2003) also occur on the coasts of the Yucata´ n Peninsula (see lists in MacKinnon 1992, 2005). We have observed laughing and ring-billed gulls (Larus atricilla, Larus delawarensis) and black vultures (Coragyps atratus) feeding on overturned horseshoe crabs and ants harvesting eggs from nests exposed after low tide (J Zaldı´ var-Rae and RE Elı´ as-Sapie´ n, personal observations). Nothing is known about the predators of adult horseshoe crabs in the Yucata´ n, but common predators elsewhere are also found here, including sea turtles (Seney and Musick 2007).

7 Status of Horseshoe Crabs in Mexico and Threats 7.1 Legal Status

Mexican law regards L. polyphemus as ‘‘in danger of extinction’’ since 1994 (SEMARNAP 1994; SEMARNAT 2002). This category overlaps IUCN’s ‘‘endangered’’ and ‘‘critically endangered’’ categories and includes species whose distribution or population size is drastically diminished or whose biolo- gical viability is at risk due to drastic modification or destruction of their habitat, over-exploitation, disease, or predation. Since 2005, the Mexican fed- eral agency in charge of programs to conserve species at risk is the Comision´ Nacional de A´ reas Naturales Protegidas (CONANP, National Commission for Natural Protected Areas), but so far no specific program for the protection and conservation of horseshoe crabs has been implemented.

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7.2 Human Use

Elderly locals report that when they were young they occasionally used female horseshoe crabs as food (M Rosales-Raya; unpublished data) cutting them open for their eggs (G Veronica Rios, unpublished data), and there are reports of the use of horseshoe crabs to feed pigs (Cha´ vez and Mun˜ oz-Padilla 1975). However, these uses have been rare to non-existent for several decades. The traditional octopus fishery (Octopus maya and Octopus vulgaris) of Campeche and Yucata´ n once relied on horseshoe crabs as bait (M Rosales-Raya; unpub- lished data). However, due to a growing international demand for octopus over the past 30 years (Pe´ rez-Pe´ rez et al. 2007, Herna´ ndez-Flores et al. 2001) and to the legal protected status of horseshoe crabs, fishermen now favor more abun- dant and commercially available bait such as spider crabs (Libinia dubia).

7.3 Shrimp Fishery

Given the income it generates, shrimp is the most important fishery in the Gulf of Mexico. Over 600 trawlers from ports in the five Mexican states of the Gulf of Mexico sail the continental shelf off the coasts of Campeche in Mexican waters to catch four species of peneid shrimp (Farfantepenaeus duorarum, Farfant- epenaeus aztecus, Litopenaeus setiferus, and Xiphopenaeus kroyeri), concentrat- ing on the waters just outside the Laguna de Te´ rminos (Ferna´ ndez-Me´ ndez et al. 2001). Trawling nets are designed to be dragged over the sea bottom and most of the trawling activity is carried out in shallow waters. This means that horseshoe crabs and other benthic organisms have likely been negatively affected for decades. However, no quantification of horseshoe crab by-catch or mortality due to trawling has been conducted.

7.4 Offshore Oil Industry

The area off the coast of Campeche, known as the Campeche Sound (Fig. 1), contains the largest and most important oil fields in Me´ xico. Since the discovery of these oil fields in the 1970s, production has steadily increased and now constitutes more than 80% of national crude oil (Garcı´ a-Cue´ llar et al. 2004). The environmental impact of oil industry activities in the Campeche Sound includes the dispersal of heavy metals, polycyclic aromatic hydrocarbons, sulfur oxides, nitrogen oxides, sulfuric acid, volatile organic compounds, and total petroleum compounds, with varying detrimental effects on marine ecosystems (Garcı´ a-Cue´ llar et al. 2004). The benthic communities suffer the most severe effects (Botello et al. 1996). Major oil spills during the 1980s had severe consequences in estuaries and coastal lagoons, damaging the reproduction and growth of populations of several important fisheries (Soto et al. 1982;

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Botello 1987; Botello et al. 1996). Fortunately, spills and their extent have been reduced since the 1990s and frequent environmental auditing of Petroleos´ Mexicanos (PEMEX), the national oil company, is contributing to the devel- opment of safer practices (Gue´ dez-Mozur et al. 2003; PEMEX 2000, 2002). The potential role of pollution from the oil industry on the decline of horse- shoe crab populations in Laguna de Te´ rminos has not been studied. However, this appears to be a valid hypothesis given that (a) the prevailing currents in the eastern Gulf of Mexico head south (Leipper 1954), possibly carrying and concentrating pollutants in the southern part of the gulf and Laguna de Te´ rminos; (b) horseshoe crabs use benthic habitats in coastal lagoons and estuaries, where dense crude precipitates and lingers; (c) exposure to oil affects juvenile development (Strobel and Brenowitz 1981); and (d) their diet is based on bivalves, which are known to bioaccumulate pollutants (e.g. Bryan 1979; Porte and Albaige´ s 1994; Bolning 1999; Gold-Bouchot et al. 2007).

7.5 Coastline Modification

The most widespread threat to horseshoe crabs in Mexico is shoreline modifica- tion. Coastal cities in the Yucata´ n Peninsula are experiencing rapid human population increases and, as a result, these cities are spreading into adjacent coastal areas to develop tourism, services, and housing infrastructure. Further coastline modification results from the construction of summer houses around coastal villages, to supply a growing market for second homes for those living in inland cities. In general, the increase in human population in coastal areas has caused the disappearance of nesting and nursery habitats for horseshoe crabs and the degradation of adjacent water bodies due to pollution from garbage and sewage, limited water fluxes, or the filling of coastal lagoons to expand city areas. Another example of shoreline modification is the use of artificial barriers to reduce the effects of sea erosion on certain beaches. Owners of beachfront property in these areas face an increased risk of their houses being destroyed by hurricanes and storm surge or due to the repeated action of high tides. To prevent this, artificial reefs made of rocks or plastic mesh tubing are being placed parallel to the wave line, in order to favor the deposition of sand on the beach-facing side of the barrier. This strategy has indeed reduced the energy of these beaches by reducing their slope and creating a smoother beach profile (SEMARNAT 2007; A´ lvarez-Del Rı´ o 2003). Horseshoe crabs use beach slope as a cue to get back to the sea after spawning, and a smooth beach profile may increase their probability of getting stranded (Brockmann 2003a). Additionally, the sand in most of Yucata´ n’s beaches is very fine, which provides a large surface area for microbial growth. Such growth creates anoxic conditions which impede egg development (Brockmann 2003a). Therefore, a gentle

[email protected] 106 J. Zaldı´ var-Rae et al. beach slope may exacerbate anoxia and unsuitability for egg development, because the substrate in the intertidal zone becomes water-saturated.

7.6 Rising Sea Levels

Beaches where horseshoe crabs used to spawn are eroding due to sea-level rise (M Rosales-Raya, personal observations). This is particularly evident on the west side of the Peninsula where erosion has resulted in the moving of the intertidal zone to unsuitable substrates. For instance, the former nesting site of Isla Pa´ jaros in Laguna de Te´ rminos used to be a thick mangrove islet that remained dry even at high tide for at least the past 30 years, but has now turned into a sparse group of trees, whose substrate is completely submerged even at low tide.

7.7 Tourism

Owing to its great appeal as a tourism destination and the resulting economic development, the Caribbean coast of the Yucata´ n Peninsula (state of Quintana Roo) is experiencing one of the highest rates of population increase in the world, and horseshoe crab populations in this area have already been affected. Large coastal lagoon systems where horseshoe crabs were usually found have already been severely damaged by sewage discharges, pollution by landfills, and the cutting of mangrove forests to build the hotel infrastructure. Pristine coastal lagoons and associated fresh water ‘‘cenotes’’ (sinkholes) are becoming coveted amenities for tourism projects in the area, and the potential damage to the small horseshoe crab populations they may harbor is yet to be established.

8 Opportunities

In spite of all the threats faced by horseshoe crab populations in Mexico, there are grounds for hope and opportunities to preserve populations that are still healthy, and restore those that have been damaged.

8.1 Education of the Local Public

Many people in the Yucata´ n Peninsula recognize horseshoe crabs, including thousands of families from inland cities and towns who spend their summer vacations in coastal communities. This creates the opportunity to educate a mixed ‘‘captive audience’’ of local and urban people (many of them children and youngsters) on why horseshoe crabs and their habitats are important and

[email protected] American Horseshoe Crabs, Limulus polyphemus, in Mexico 107 unique. These people are likely to transmit their knowledge to other citizens, increasing the base of moral, political, and financial support for further con- servation efforts.

8.2 Citizen Initiatives

There are a growing number of non-governmental organizations dealing with the conservation of coastal systems in the Yucata´ n Peninsula. Particularly, two of us (RE Sapie´ n-Silva, J Zaldı´ var-Rae) are now working with a group of young Mexican biologists to create a new non-governmental organization, among whose aims will be the conservation and restoration of horseshoe crab popula- tions and their habitats. We intend to achieve this through several strategic lines: (a) educating both urban and coastal local communities, (b) promoting sustainable development in coastal communities, (c) involving local commu- nities in conservation programs, (d) contributing to the scientific study of L. polyphemus in Mexico, (e) informing and counseling decision-makers on the status of horseshoe crabs and their habitats in Mexico, and (f) building alliances with governmental agencies, other national and international initia- tives, environmentally responsible companies, and other stakeholders.

8.3 Protected Areas

Many of the most important horseshoe crab localities are now within federal or state protected areas; particularly, parts of offshore horseshoe crab habitat and the nesting and nursery areas of Laguna de Te´ rminos, Celestu´ n, Rı´ o Lagartos, Isla Arena, and Holbox are within federal Areas for the Protection of Flora and Fauna or Biosphere Reserves managed by CONANP since the year 2000 (see map in www.conanp.gob.mx/sig/). CONANP has been developing a model of conservation based on the sustainable development of local communities within protected areas and their area of influence, and strongly encourages the involvement of local communities, academic institutions, non- governmental organizations, and the general public (SEMARNAT-CONANP 2007). As a result of increased awareness of environmental issues among Mexican society, federal and state budgets for conservation are steadily increas- ing, even in spite of budget cuts in other governmental areas. A large portion of these resources is going into hiring and training personnel, reinforcing the infrastructure, and building up the capacity for the operation of protected areas. In sum, the emerging governmental conservation policies, programs, and increasing governmental budgets should be incorporated in a strategy to protect and preserve horseshoe crab populations.

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8.4 Research and Higher Education Institutions

There are good conditions for carrying out research and developing collabora- tions with academic institutions and researchers in the Yucata´ n Peninsula and the rest of Mexico. Particularly, the Yucata´ n Peninsula hosts several national and state research institutions and universities, many with respectable infra- structures, including state-of-the-art communication technologies and equipment. Hundreds of local professionals in biology, natural resource man- agement, fisheries, environmental science, chemistry, and chemical and indus- trial engineering graduate from these institutions every year. With regard to horseshoe crab populations and their habitats, this wealth of human resources is as yet untapped to carry out research and conservation and monitoring programs, as well as to devise management schemes for healthy populations and habitats and to conduct mitigation and restoration actions in disturbed areas.

9 Gaps in Knowledge and Priority Actions

Finally, we would like to point out some priority work that needs to be done in the near future. In order to develop a baseline body of information to design a conservation strategy, carry out key actions, and evaluate their impact, we need to determine the population sizes offshore and how these relate to the numbers of live and dead animals and exuviae that can more easily be monitored along the shores. In addition, it is important to establish where the key recruitment, feeding, and juvenile development areas are. Devising protocols for particular populations and habitats will enable us to reinforce the capacity of officials in charge of protected areas by training them and establishing monitoring proce- dures that can be applied on a constant basis to evaluate the status of horseshoe crab populations. In order to determine management units for conservation and remediation of the damage that the populations may have suffered, information from population surveys will have to be coupled with that from studies of the genetic structure of Mexican populations. The molecular technologies and know-how to obtain these data are already available in Mexico. Obtaining and maintaining the support of local communities, particularly those groups making direct use of coastal areas and resources in the Yucata´ n Peninsula, is as important as obtaining scientific data and managing popula- tions. Therefore, it is paramount to start educating children and adults, especially while they are experiencing horseshoe crab habitats and coastal ecosystems first-hand. This includes educating children from coastal commu- nities to understand that they will be the future stewards and main benefici- aries of such resources. At the same time, it is necessary to train current natural resource owners and users in sustainable practices and to promote the

[email protected] American Horseshoe Crabs, Limulus polyphemus, in Mexico 109 diversification of their sources of income, so that they can improve their living conditions while reducing exploitation pressures on particular elements of ecosystems. A risk map for L. polyphemus in Mexico is needed, in order to identify the main threats and causes of disturbance to particular populations or manage- ment units and to achieve a more effective conservation and management strategy. Such an exercise will allow us to identify specific problems in parti- cular locations, opportunities and strengths to address them, the stakeholders involved, the key actions to be taken, the timescales for these actions, and the resources that will be required.

Acknowledgments The authors thank the Organizing Committee of the International Sym- posium on the Science and Conservation of Horseshoe Crabs for financial support to attend the meeting. M.L. Botton provided helpful comments on the manuscript. JZR received financial support from UNAM and H. Drummond, Instituto de Ecologı´ a, UNAM. MRR received a PROMEP MSc scholarship from the Mexican Secretarı´ a de Educacion´ Pu´ blica. Funding was provided by the National Science Foundation of the US and AAAS-WISC for HJB. Assistance with field collections was provided by G.V. Rı´ os, Centro Regional de Investigacion´ Pesquera, Yucalpete´ n, Yucata´ n Mexico.

References

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