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Pre-Meeting Background Material for the 2011 International Workshop On Pre-meeting background material for the 2011 International Workshop on the Science and Conservation of Asian Horseshoe Crabs (13-16 June 2011, Hong Kong, China] Carl N. Shuster Jr. NOTE: Because I will not be able to attend the workshop, this paper is intended for distribution to participants ahead of time so that if any questions arise on it or other topics, they can be sent to me before 30 April 2011 so that I can respond prior to the workshop. In addition, a video keynote address will be presented at the workshop. SUGGESTIONS: In preparation of background material for the workshop I: Used Biology and Conservation of Horseshoe Crabs (2009), The American Horseshoe Crab (2003), and Biology of Horseshoe Crabs (1988) as guides; Assembled and read recent papers on populations (viz.: papers co-authored by David R. Smith et al.; Winston Watson III et al., etc.); Assembled and read recent papers on habitat (viz.: Jackson, Nordstrom 2009; Jackson, Smith, Nordstrom 2008; Jackson, Nordstrom, Smith 2002; etc.); Prepared the attached background information, based primarily on what authors have sent to me (my thanks to them, as I do not frequently get to libraries) and some internet searches. Within the past two decades there probably have been more publications on Limulus polyphemus than in all previous years on a wide range of topics including spawning, fecundity, egg transport, population dynamics, distribution and migrations, fossil species, and habitat changes, etc. So much, it seems to me, that much effort will be needed to assimilate what has accumulated. Developed a table of questions and answers pertaining to Limulus, as a guide to preparation of what would be more pertinent to the Asian species. The following material may not be the information that you expected or hoped for. If so, I am willing to attempt to provide it and to answer questions on Limulus, prior to the workshop. Please send questions to [email protected] before 30 April 2011. 1 Limulus polyphemus as a Model for the Conservation of Horseshoe Crabs Carl N. Shuster Jr. Virginia Institute/School of Marine Science, The College of William & Mary March 2011 PROLOGUE I am honored and humbled by the invitation to keynote ways in which Limulus might serve as a model for the conservation of Asian horseshoe crabs. This is a challenge because we are in an upward trend of research on Limulus that is related, in part, to conservation and management of the species and there are so many others who are well-aware and involved in Limulus conservation issues. One such expert, the late Dr. Robert B. Barlow, known for his many contributions to understanding vision, circadian rhythms, and spawning in Limulus would probably advise up to look after the “little ones” – meaning, of course, populations of lesser numbers of horseshoe crabs. He would speak emotionally but accurately and succinctly of his experience in having his research population wiped out by commercial harvesting (Weiner and Barlow 1999); (Figure1). Due to his incisive insights and his many contributions on Limulus, I respectfully request that this workshop be dedicated to the memory of Dr. Robert B. Barlow. 2 INTRODUCTION A call for international coordination in the pursuit of the conservation and management of horseshoe crabs was a theme of the symposium held in 2007 at Dowling College, U.S.A. (Tanacredi et al. 2009). It and the report of its panel on horseshoe crab management (Berkson et al. 2009) were direct precursors to this workshop. The panel, comprised of representatives from five countries, responded to eight questions prepared by Berkson. They generally agreed that: Basic data necessary for assessment of the status of the horseshoe crab populations had not been collected. Habitat degradation and loss was the primary threat to the populations. Primary focus must be on protecting spawning and nursery habitats. A citizenry educated on the importance of the crabs, especially the policymakers, is essential. Information and lessons learned during research and management in other countries should be made more directly available through regularly scheduled meetings. Funding should be sought, especially at the ecosystem-level. In contrast to the general unanimity on the first seven questions, opinions regarding the future of horseshoe crab conservation ranged from pessimism (Taiwan and China), to cautious optimism (India), to guarded optimism because there was still time to thwart some major threats (Mexico), to outright optimism (USA) due to successful coordination of coastwise management by the Atlantic States Marine Fisheries Commission. Defining Conservation Everyone “knows” what conservation is, but do we agree on a definition? As a country boy, trained at a land grant college, it is perhaps natural that I emerged as a believer in conservation as the wise use of a resource. That may not be the concept applicable to the goals of this workshop. In any case, I believe we should define the term. As part of the discussion I would point out that we may not be able to save all populations of horseshoe crabs. If not, is the information obtained and recorded on a population an adjunct to saving it or at least remembering it? 3 Scope of the Following Material Participants of this workshop most likely will be called upon to evaluate available information on the Asian species, determine what else should be obtained, and then decide, at the very least, what actions could be taken to conserve and protect the Asian horseshoe crabs. This paper calls attention to what has been learned about the science, conservation, and management of Limulus populations that may provide a useful background for the development of a conservation strategy for the Indo-Pacific horseshoe crabs. It concentrates on the first two of the four workshop themes (Populations, Habitats, Exploitation/Utilization, and Public Consensus). Why Look To Limulus? The suggestion that Limulus polyphemus, the American horseshoe crab, can serve as a model for the conservation of the Indo-Pacific species is based on a large amount of scientific information on the natural history and ecology of Limulus polyphemus, as well as programs to manage its populations. This information and experience provides a sufficient background to begin the discussion on conservation, despite major differences in the natural and political patterns of the distribution of Limulus and that of the Indo-Pacific species. One glance at the distribution of the Asiatic species is sufficient to appreciate the dedication of Dr. Sekiguchi and his colleagues in the difficult task of mapping and studying such diversely situated populations (Figure 2). Even a casual inspection of the figure suggests that the number of horseshoe crab populations around Borneo is an invitation for an in depth study, particularly due to the presence of all three Asiatic species. There is a long history of research on the Asiatic species, especially Tachypleus tridentatus, exemplified by an excellent treatise on the Biology of Horseshoe Crabs edited by Koichi Sekiguchi (1988). Thus the challenge is to select and utilize what is pertinent from our collective experiences. Much research on Limulus has occurred in recent years; even a summary of that research would create a book. Because I have selected items emphasizing populations and habitats that illustrate or contribute to the conservation theme of this workshop, this selection does not evenly reflect all that is available. 4 In contrast, all of the populations L. polyphemus, except the more ancient ones on the Yucatan peninsula, are located within the boundaries of the United States of America and relatively easy to get to. Because the sequence of spawning along the coast is staggered, being slightly later and later as one travels northward, it is possible to observe the spawning of a majority of the populations on the Atlantic coast from Florida to Maine in one summer (Figure 3). In another summer, the Gulf of Mexico population, from Florida to the Mississippi delta, could be examined, including an expedition to Yucatan. These distributions have the distinct advantage of not only that of relative accessibility but also the opportunity to quickly observe many populations along an appreciable environmental gradient, from about 21o to 44o N, during one or two spawning seasons. In a world-wide search Mikkelsen (1988) has also contributed to observations on distribution of the four species. An important difference between managing/conserving the American and the Asiatic species of horseshoe crabs is that fewer nations and jurisdictions are involved in North America. POPULATIONS There are at least two guiding principles when considering the ecology of horseshoe crabs -- they are environmental generalists and they exist in discrete populations. Generally the adaptation of horseshoe crabs to their habitat or environmental factors have been subjects of prime interest (see Towle and Henry 2003). Recently questions have been raised about the genetic viability of populations have been raised (Faurby et al. 2010). Perhaps more closely pertinent topics are considered here: population size; distribution limits including influence of abundance; egg size and spawning events, etc. Environmental Generalists. Horseshoe crabs are capable of adapting/adjusting to and surviving manifold variations in their environment (Eldredge 1991, Loveland et al. 1997). They are also rugged, not only in relation to the hydroclimate but also to physical impact due to occasional high energy waves, dredges, and loggerhead turtles that 5 bash/dent or rip away part of their carapace; healing often follows even extensive wounds. It can be argued that, in addition to their physiological capacity to adjust to estuarine conditions, their survival as a group is due to an architecturally solid, three-part body design with two articulations – a piano-hinge between the first and second parts and a universal joint between the telson and the mid-part. The lineally arranged thirteen, multi-articulated appendages all operate under the carapace, as in a caisson, protected from outside interferences and capable of carrying out, more effectively, such functions as burrowing, spawning, feeding, and locomotion.
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