Volunteers aid state’s effort in crab census

Lately I’ve come to feel like Kevin Costner in “Water World.” We’ve had so many rainy days, particularly when I’ve had the opportunity to get out, that webs have started to grow between my fingers and toes.

So it was appropriate that on Wednesday when I was to explore the upper reaches of the Bagaduce River in search of mating horseshoe crabs the heavens would open up and rain (again) on my parade. That’s why rain gear was invented, right?

The area we explored is above Bagaduce Falls and between Sedgwick and Brooksville. It’s a large bay fed by tidal waters that flow past Castine from Penobscot Bay. Our intrepid band included Andrea Iverson of Washington, a teacher and guide; Maggie Williams of Penobscot, a Downeast Audubon Chapter volunteer; and Karen Francoeur of Orono, owner of Castine Kayak Adventures and a Registered Maine Guide.

Williams and several volunteers who belong to the Bagaduce Water Watch are helping the Department of Marine Resources for the second year in its horseshoe crab census. Volunteers have also helped DMR do water quality and phytoplankton monitoring, Williams said. Look for the DMR report in the winter of 2003.

The last time any sort of crab census was done in Maine was 20 years ago, Peter Thayer, a resource scientist of the DMR told me. Since then there has been heavy fishing pressure on the crabs in the Delaware-Maryland area. They are used as bait for fresh water eels. The pressure was so great in the mid-Atlantic area that officials all but shut it down. In the past several years the fishing pressure increased in Maine, Thayer said.

Now there is a 25 crab-per-person, per-day limit and the DMR is trying to establish a base picture of Maine’s horseshoe crab population. It hopes to continue the count for several more years with help from volunteer groups.

We began our own exploration and introduction to Crab Counting 101 at Bagaduce Falls and paddled up current past some oyster pens.

Despite the rain, we had a pleasant paddle, talking about the beauty of the area and watching the wildlife. There were ospreys, an eagle, a belted king fisher, a few great blue herons, black back and herring gulls, cormorants, a couple of Caspian terns and a seal. About a mile upstream we began hugging the shoreline and spotting our prey. At first I’d overlook them. They look like mud-covered stones if you’re not sure what you’re supposed to be seeing. Then we got the knack and it wasn’t long before each of us would be pointing to yet another pair in the shallows.

And the key word here is pair, because that’s what’s going on. Horseshoe crabs come here, triggered by late spring and early summer new- and full-moon high tides. They come to shore from far at sea to lay and fertilize their eggs, just as they have for more than 350 million years. If you live farther east than Taunton Bay, you won’t get the opportunity to witness this annual mating migration, because that’s the northern limit of their range.

According to information I scavenged from the Internet, horseshoe crabs are arthropods which include the insects, spiders, true crabs, and centipedes. The males (about two-thirds the size of the females) attach themselves to the shell of the females with their claspers, a bulbous claw nearest the front of their bodies. In numerous instances we saw two males being dragged along.

Most of the females we observed made their way to shallow water where there is mud and short sea grass. There they lay the eggs that are fertilized by the attached male(s). Females may lay up to 20,000 eggs in one day and 90,000 in a year.

I didn’t see any of the eggs, but I learned they are about the size of a BB and blue-green in color. They swell to twice that size in a few days. According to Bio Bulletin (http://sciencebulletins.amph.org) the reason horeshoe crabs spawn at the new and full moon is that the tides are the highest and the eggs won’t be washed away in the next couple of weeks. “Nests are usually located close enough to the water to stay damp, but high enough for the sand to contain adequate oxygen. These factors, along with the temperature, determine how long it takes for the eggs to develop” into the larval stage. “In this state of development, they molt four times in the egg. Next the young “trilobyte larva” swims for about six days. It floats on its back and paddles along with its little gill plates. It will continue to grow by shedding its shell.”

With each molt it becomes more like the shape of the adult. A 1-year-old crab is about one inch. The young hatchlings stay close to the beach for two years before they join the adults in the deeper water on the Continental Shelf, the Web site said. It takes nine or 10 years for a male to become an adult and another year longer for females. They molt 16-17 times during that time. They increase in size 25-30 percent with each molt. Once they become adults, they will not molt anymore. Females might grow to be about 24 inches long and weigh up to 10 pounds. They live up to 20 years.

Here’s some more from the Web site: Horseshoe crabs are jawless. The mouth is essentially a hole into the esophagus with muscles that open and close this opening. The mouth is located at the base of the legs which effectively surround it. The first segments of the legs are enlarged and covered with thick and hard bristles pointing inward toward the mouth. These bristles (gnathobases) act like a set of grinding tools as the animal is walking and they are used to “chew” food and direct it toward the mouth where the chelicera then finish the job of pushing the material into the mouth.

Now, don’t you know more than you ever wanted to know about this annual visitor?

Just one more bit of trivia: The blood of a horseshoe crab (which turns blue when exposed to oxygen) is used to kill certain kinds of bacteria that are harmful to humans. The extract, named Limulus Amoebocyte Lysate is used to detect whether things that go into the human body – including injectable drugs, needles and heart valves – are free of dangerous edotoxin-producing bacteria.

I’ll bet you have more respect for the ugly critters now, don’t you!

We headed back to Bagaduce Falls to meet with volunteers Dot McMahon, Phillip Nesbitt and Sally Bishop, all of Penobscot, who were doing their daily crab count. Each day, for nine days around the high tide, they will have been walking shoreline upstream of the falls, counting horseshoe crabs. Nesbitt had the duty Wednesday of wading in the shallows looking for the critters. As I paddled up to him I couldn’t help but comment on how chilly the water must be. But to my surprise he had no complaints. Indeed, the water temperature was in the 60s, much warmer than the low 50s of Penobscot Bay. The smile on his face told me he wasn’t lying! In fact, he said, the water temperature was higher than the air temperature Thursday.

The group didn’t find many crabs this day. We decided to head to a small island down stream to check out the population. Francoeur, who had paddled the area before, said she’d seen the crabs there in years past. Sure enough, we counted 48. And as we made our way back to the falls, we counted another 25 or so.

To celebrate our first-ever crab count, Francoeur, Iverson and I took a quick ride through the incoming tidal rush under the bridge at Bagaduce Falls and then it was time to get dried out and warmed up.

Jeff Strout can be reached at 990-8202 or by e-mail at jstrout@bangordailynews.net