The State of Florida wants you to peep on mating horseshoe crabs.
Relax. It's for science!
Ecologists have only a vague understanding of how horseshoe crabs are doing, especially in Florida. So the Florida Fish and Wildlife Conservation Commission is urging people to report sightings of the prehistoric crabs mating. That way they'll know the most important horseshoe crab spawning habitats to protect, News 6 partner Florida Today reports.
"These sightings are extremely valuable because we can't cover the whole Florida coastline," said Claire Crowley, research scientist at the Fish and Wildlife Research Institute in St. Petersburg.
These fearsome-looking prehistoric creatures have survived multiple global mass extinction events. The fear, though, is they may not survive us. They're already endangered in Japan. And recent research shows they appear to be facing extinction in other areas, mostly due to encroachment on their beach habitats, pollution and over harvesting for everything from food to medicine.
Chitin, a substance found in their shells, can be used to make hair sprays, contact lenses, skin creams, antacids, surgical sutures, and products that promote weight-loss or lower blood pressure. Chitin also is used to remove metals and chemicals from wastewater.
The Chinese consider horseshoe crabs a delicacy. Fishermen use them for bait.
But the importance of the species goes way beyond its commercial value. Horseshoe crabs play a vital role in the Indian River Lagoon and other marine food webs in Florida. Fish, shorebirds and turtles rely upon their eggs for food. They are scavengers, cleaning waters and recycling nutrients. They are a virtual nanny, carrying on their backs and bellies the offspring of many other marine creatures. Their very presence is a barometer of coastal health.
To protect the crab's unique benefits to humans and the food web, biologists want us to watch these crustaceans as they go about the business of making baby crabs.
Horseshoe crabs mate year-round, but more frequently in March and April, the prime time when they get all moonstruck. They mate close to high tide, just before or after a full or new moon. That's the best chance to spot them, within three days of a new or full moon.
New moon was on Wednesday, March 6, and the next full moon is Thursday, March 21.The crab's eggs can't survive in all the Indian River Lagoon's low-oxygen muck sediments that have built up over decades due to fertilizer, sewage spills and leaking.
At risk of vanishing in some areas
These ancient crabs are often referred to as the "living fossil," because of its distant relation to the extinct trilobites. They crawled Earth before the dinosaurs, much in the same form we seem them today. They are actually more insect than crab, and are considered distant cousins of spiders and scorpions.
Although they've been around almost 450 million years, biologists know little about Florida populations. The public's sighting information helps researchers target spawning beaches for the Florida Horseshoe Crab Watch Program, a citizen science initiative to collect scientifically accurate data statewide.
What is known about their status is a mixed bag. A 2016 federal study that examined horseshoe crabs in six regions of the United States concluded the species is "vulnerable to local extirpation and that the degree and extent of risk varies among and within the (six) regions."
A group of researchers — which included the U.S. Geological Survey, the University of Florida, and Sacred Heart University — found an elevated risk of horseshoe crabs going extinct in the Gulf of Maine region because of limited habitat, and in New England because of over-harvest. Populations in the Mid-Atlantic and Delaware Bay regions were stable, the study found.
In the Florida Atlantic region, the study showed mixed trends among various areas, with populations shrinking for poorly understood reasons in coastal bays and estuaries. Some have pointed to the advent of more frequent and severe toxic algae blooms in coastal waters.
The crab's geographic range is too vast to merit a threatened risk category for the species, the researchers wrote, but habitat loss remains a concern.
"Breeding appears to have stopped at some historical locations," they wrote about Florida crabs.
The problem in Florida, the researchers said, is that it has been hard to determine exactly where horseshoe crab populations are thriving and where they are not. In general they seem to be suffering from over exploitation by crab fishermen and habitat loss, or they are being killed at power plants where they can get sucked into the cooling equipment.
Locally, harvesters have been seen in past years hauling off truckloads of horseshoe crabs from the lagoon.
In 1999, for reasons scientists can't explain, an estimated 100,000 horseshoe crabs in the northern lagoon and southern Mosquito Lagoon died off, leading some researchers from the Florida Institute of Technology and the U.S. Army Corps of Engineers to conclude that the lagoon may no longer be suitable habitat for horseshoe crabs.
Crab eggs can't survive in all the Indian River Lagoon's low-oxygen muck sediments that have built up over decades due to fertilizer, sewage spills and leaking septic tanks.
But there have been recent signs of the crab's recovery in the lagoon.
"We do see mass spawning events in the lagoon, and it's extremely promising," Crowley said. "We recently had 8,500 crabs in the lagoon!"
Florida Power & Light Co. says it has helped populations in the lagoon by installing a barrier that stops 99 percent of the crabs from getting sucked into its Canaveral plant.
During mating season, the smaller males swim back and forth along the shoreline, waiting for the larger females. He latches onto her back. The females lay up to 30,000 eggs, which the males then fertilize. Other "satellite" males butt in on the couples, also to fertilize the eggs.
Crowley, the researcher with the FWC, said one challenge to the species is that the crabs take a long time to reach maturity, about 10 years for females and nine years for males.
Because the females lay so many eggs that other species rely on, biologists urge people to flip over any horseshoe crab they see turned over on its shell. Grab them from the sides, however, not the tail, which has photoreceptors that help the crab steer.
But probably the horseshoe crab's biggest hurdle, biologists say, is armoring of the coastline with seawalls, rip-rap rocks and other obstructions. Those can block the crabs from reaching a smooth sand surface.
Florida began the public's horseshoe crab sighting program in April 2002. As of December 2017, FWC received 4,051 reports of horseshoe crabs. The program originated from the Atlantic States Marine Fisheries Commission, a consortium of several states, which requires all Atlantic states to identify the crab's spawning beaches.
"It provides a huge amount of information for us," Crowley said. "It's really an easy thing to do when folks are out enjoying themselves."
Report horseshoe crab spawning:
You can download the free FWC Reporter app on Apple or Android smartphones or tablets from the App Store and Google Play. Or they can e-mail the information tohorseshoe@MyFWC.com, or call it in to a toll-free number: 866-252-9326.