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The humble horseshoe crab is a reminder of prehistoric times. Public Radio International’s Living on Earth recently devoted a segment to this curious character.

From the transcript of the show …

Steve Curwood: “For healthy oceans, it’s not enough to protect just the top of the food chain – the cod or halibut or swordfish we eat. The bottom of the food chain is vital too. That could be the plankton or the tiny forage fish eaten by many species – or it could be the extraordinary prehistoric-looking horseshoe crab.

“These helmet-shaped arthropods have been around for millions of years, and up and down the east coast of the US, volunteers come out to count them as the females come ashore to spawn. On Cape Cod, as Karen Zusi reports, scientists and volunteers are tagging and labeling the crabs to help conserve them.”

Karen Zusi: “There are a lot of reasons why someone might appreciate the lowly horseshoe crab. Eel and conch fishermen use them as bait, and medical companies draw blood from the animals. Horseshoe crab blood will clot in the presence of bacteria, so these companies can use the crab’s blood to make sure vaccines and medical implants are free of germs. Their blood is worth sixty thousand dollars a gallon.

“But horseshoe crab populations are dropping. To preserve them, scientists and volunteers on Cape Cod are wading into the water to count and tag the animals.

“Special labels help them keep track [says] Mark Faherty, the science coordinator at Audubon’s Wellfleet Bay Sanctuary. …

“The Massachusetts Audubon Society just recruited graduate student Michael Long to lead their newest horseshoe crab study. With researchers from the University of Massachusetts, he will be tagging the crabs this summer with a telemetry [label], glued onto the crab’s shell.”

Faherty: “My acoustic study is going to be putting on acoustic receivers out in the bay, and acoustic markers on the crabs. The receivers have about a 600-meter detection radius so anytime a crab that’s marked with an acoustic receiver comes within 600 meters of that receiver, it will mark where it is. So based on where each crab pings, you can kind of track its movements around the bay.”

Zusi: “None of this would be possible without the Audubon Society’s volunteers. They come from all walks of life.

“At an Audubon horseshoe crab conference, Long organizes new volunteers to help him count horseshoe crabs on the beach, and Faherty trains them in the basic survey procedures. …

“Once they got down to business, the volunteers were trained to divide the beach into small sections, count the horseshoe crabs, and record all of their information. The volunteers go out to survey when female crabs are coming to lay their eggs in the sand. Males follow to fertilize the eggs after they’re laid.”

Faherty: “The male crabs you quickly learn to recognize because they’re by themselves. They will mate with a model, if you make a model of a horseshoe crab — the males will congregate around it. They’ll spawn. They’ll spawn with your boot. These are just hormonally-charged animals that are ready to mate with anything. Females are not lonely for long in the horseshoe crab world.”

More here on the effort to study and protect horseshoe crabs.

Photo: Peter Massas, Flickr CC BY-SA 2.0
A horseshoe crab floats by the shore on Union Beach in New Jersey. The species is listed as Near Threatened by the International Union for the Conservation of Nature.

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