Management of Horseshoe Crabs

In response to a question I asked Jane Brockmann (see below) about what she found to be one of the most interesting aspects of horseshoe crabs, she responded:         

          "A really interesting aspect of this whole issue is that the management of horseshoe crabs is actually very special and interesting. Horseshoe crabs are in no real danger, there are a lot of horseshoe crabs. What is in danger is this "bird/ horseshoe crab" phenomenon that you have in Delaware Bay and in some other places where there are so many horseshoe crabs that they dig up each other’s eggs and there are eggs strewn on the beach.  The migrating shorebirds feed on those excavated eggs. You just get these masses of birds on the beach and it is really something to see! In this system you are actually managing horseshoe crabs for the birds.  The management of nearly all other species is not like this. When you manage striped bass or blue crabs, or something like that, you’re managing blue crabs for blue crabs and you manage their harvest. You allow the harvesters to take the blue crabs up to a certain point.  Most populations of animals are density dependent, so if you get up to a certain population level and then they just don’t increase because all they’re doing is competing with each other, well, when a population is at that level then you can harvest out those extra ones and it actually doesn’t harm the population at all. This is a density dependant effect. So normally you manage a population, and an intelligent management of a population is right at this density dependant number. Well, with horseshoe crabs you have to manage them well beyond density dependence because that’s what creates the phenomenon of their digging up each other’s eggs. There’s so many of them, of course their numbers aren’t going to increase because they are digging up each other’s eggs, but that’s the resource that you’re actually managing for. I don’t know of any other management that’s like this. It’s a very special thing."

Climate Change & Horseshoe Crabs

     This past November I had the honor of interviewing Dr. Jane Brockmann of the University of Florida.  Dr. Brockmann is also one of the editors (along with Carl Shuster and the late Bob Barlow) of the classic book "The American Horseshoe Crab."  Here are her responses to two of my questions:

There was an article that was bouncing around the Internet a couple months ago - various permutations on the climate change and its effect on horseshoe crabs. I’m wondering if you had any views on that, pro or con.

     Sea level is definitely rising and horseshoe crabs are very dependent on having good beaches for laying their eggs.  There are a wide array of things that make a beach good, but they do need a beach or some kind of well oxygenated sand in which to lay their eggs and that’s what this annual migration is all about. Of course, sea level rise has happened many times in the past and horseshoe crabs, of course, have survived all of them, very nicely. However, this sea level rise is different in the sense that there is now development behind the beaches, even in places like Delaware, where they have done a wonderful job of preserving the coastline, and Georgia, too. If the sealevel rises enough, then it’s going to flood those beaches. Now in the past, that’s been fine, because that beach sand was just moved further up the shoreline and they had beaches in ten miles from the previous shoreline, but now we’re not going to allow that to happen; we’re going to be putting up raised land and blocks of various sorts and we’re going to lose beaches (they are not going to re-form as they have in the past). I think it is very worrisome that we will lose our beaches and because of our development, there’s really no place for a new beach to form farther inland. So I think it is a big worry, yes. I’m from Florida, so a good chunk of that state is going to be lost and our beautiful beaches are going to be lost. It is definitely going to be difficult for the shorebirds and the horseshoe crabs.

You see a negative impact here? Both for the crabs and the birds?

     I think it’s very likely [that there will be an impact from global warming]. Shorebirds are also feeding in estuarine areas and those estuaries are going to be inundated with sea level rise.. It’s a big problem. And then, with these species, such as the red knot that nest so far north, I think the warming of the northern areas is also going to have an effect on their ability to reproduce. Red knots nest as far north as you can find land and those animals are definitely going to be affected by increasing temperatures. It’s going to affect the insects they feed on; it’s going to affect their nesting sites; it’s going to affect their migration; sea level rise and global warming are definitely going to affect these species.

Please note:  Other questions from this interview (and Dr. Brockmann's responses) will be posted on this blog in the near future.  Please stay tuned.

Welcome Crab-ologists!

Simply put – this is a blog all about horseshoe crabs…everything you’d ever want to know or read.  The blog will include an eclectic array of data, information, research, fascinating people, fascinating facts, surveys, on-site observations, anatomy, people, perspectives, opinions, controversies, the movers and shakers, and all the stuff we’ve come to love (and come to know) about these sometimes enigmatic, yet always intriguing, creatures.  I’ve already had the pleasure of interviewing some of the leading figures in horseshoe crab research and horseshoe crab conservation - you’ll hear their voices in this blog.  I’ll provide you with some scientific explorations of horseshoe crab habitats and behaviors.  We’ll take a look at their ancestry and their future, as well as some of the inevitable controversies.  We’ll travel to magical places throughout the Delaware Bay, up and down the eastern seaboard, and around the world.  In short, no stone will be left unturned and no horseshoe crab will be left undiscovered.  I invite your comments, your ideas, your perspectives, your thoughts, your arguments, and your contributions to this blog.  I’d like to expand and enlarge the community of “crab-ologists” and share all the wonders of this ancient lifeform with a wide and varied audience.  Come join us for a magnificent and extraordinary journey!

One Summer Evening

We were an eclectic troop of teachers, businesspeople, housewives, artists, novelists, plumbers, lawyers, ecologists, accountants, children’s authors, and social workers.  Led by Glenn Gauvry of the Ecological Research & Development Group (ERDG), we had each signed up to witness one of nature’s most spectacular rites of spring – an orgy of arthropods.  The annual mating call had sounded and tens of thousands of ancient creatures had heeded its siren echoes – scraping their way up out of the depths to frolic in front of several wide-eyed voyeurs who were recording their every move and every action.

            I guess if you want to have group sex, an isolated beach in Delaware is as good a place as any.

            As we strolled up the beach we watched transfixed as couples mated on every stretch of sandy real estate they could find.  Almost alien in appearance, these sub-marine “tanks” plowed their way out of the water, up the beach, and into each other with all the delicacy of a frenzied herd of bull elephants drunk on fermented fruits.  There were the usual twosomes and threesomes, and occasionally we would come across a foursome, a fivesome, and even one over-stimulated sixsome – a coupling which, I am sure, would have put most adult film stars to shame.  Cameras clicked and notes were scribbled as we traipsed through rippling waves to watch these critters perform – each of them totally oblivious to our presence and each totally absorbed in a ritual propelled by tides and temperatures and hormones…forces as old as time itself.

For millennia after millennia these crabs and their ancestors have been locked in an eternal embrace – passing their genes and their ancestry from one generation to the next.  Each of us knew we were short-term witnesses to a perpetual spectacle that has been taking place since, well, since almost forever – a spectacle full of awe and mystery and the passion of persistence.

It is, most hopefully, a never-ending story.