Friday, May 23, 2014

Getting crabby on Raritan Bay

I have a lot of respect for horseshoe crabs, in a "prehistoric creature that fascinates me" kind of way. They're survivors, having roamed the ocean floor for at least 300 million years. As other species have evolved and others have gone extinct, these helmet-shelled arthropods have largely stayed the same and managed to survive.

To be honest, though, they kind of freak me out. They're not the most attractive creatures out there, and, well, they're creepy. Most of the time, the only onshore sign of them is their molted shells, but in the spring, they're very active. Coming up the beach and out of the water, they lay and fertilize their eggs in damp sand, looking like some sort of automated armored toy as they move. I can appreciate their efforts, as their eggs play an important role in the larger ecosystem. After the crabs spawn and return to the water, the endangered Red Knot and other migratory shorebirds feed on them, regaining energy they need to continue their treks to breeding grounds far to the north. The remaining fertilized eggs develop into larvae and then baby horseshoe crabs, continuing the cycle of life.

The other day, I was just about done with a visit to Sandy Hook when I decided to check out the bayside beaches toward the south end of the hook. Out beyond the grassy dunes, I discovered nearly a dozen stranded horseshoe crabs, laying on their backs. They'd apparently been rolled over by the waves lapping up against the beach.

Since they were larger, I assumed them to be females, which made their survival all the more important. As the Bayshore Regional Watershed Council has discovered through their survey of Raritan and Sandy Hook Bays, the ratio of male to female horseshoe crabs in those waters is seriously out of whack. Where a natural ratio is about five to 10 males for every female, the bay region's population is about 20 to one. The issue becomes even more critical when you consider that they generally don't mature as adults until the age of 12, leaving them with about six years of fertility before they die at around age 18.

Scientists aren't sure what's causing the disparity in the genders, though the theory is that humans are playing a role. It's illegal to harvest horseshoe crabs in New Jersey, but it isn't in New York, where individuals can capture up to five a day for personal use. Egg-bearing females are especially prized as bait for eel and whelk fishing. Considering that Staten Island has a considerable shoreline on Raritan Bay, the answer may be right there.

As I was standing on the beach at Sandy Hook, I knew nothing about the troubling male-female ratio, just that the individuals stranded there clearly needed help. While there was a small chance of them being righted eventually by the gentle waves, it was more likely that they'd be picked at by gulls. Despite my squeamishness, I figured I had to be the one to turn them over, but there was no way I was going to pick them up. Nudging them over with my booted toe didn't seem right either, so I looked for a stick to do the trick. Fortunately a good sized driftwood branch was sitting on the beach nearby, perfectly bent to provide the right amount of leverage.

The first crab I approached was still wriggling her legs, apparently trying to build up enough momentum to roll over. Using the branch, I gently rolled her upright, and she rapidly walked back into the approaching waves. The next one wasn't as animated, but her book gills were panting, showing signs of life. She flipped over easily with a little help and was on her way. Another had stuck her spiny tail straight up, perhaps attempting to use it to right herself with no success. She was breathing, too, and responded well once I got her right-side up.

It looked as if I'd gotten there in time to help out all of the beached horseshoe crabs -- every one of them made her way back into the water after she got back on her feet.

I share this story not for any kind of praise but to share a simple way that we all can make a positive impact on the survival of horseshoe crabs and, by extension, endangered shorebirds. If you're on the beach and you see an overturned horseshoe crab, don't assume it's a molted shell or already dead. Check to see if it's alive (the moving gills are a good indicator). Then carefully flip it over by the shell, avoiding the scratchy, pointy tail. And remember: though it may look creepy, it's harmless. It's just a survivor of another age who's continuing to keep our ecosystem alive.



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