By now, a quarter-million tiny horseshoe crab hatchlings have made themselves at home in the mud of the Cape May Canal and nearby waters, where they will spend the winter.
The hatchlings, about half the size of a pinkie fingernail, were part of an ongoing experiment at Rutgers University's Aquaculture Innovation Center in Lower Township designed to better understand how to increase the crab population in the Delaware Bay.
The idea is simple: collect wild eggs and let those eggs hatch in the safety of a tank, away from predators or extreme weather. The goal also is to better understand the life cycle of an ecologically critical and commercially important species at the center of intense political debate.
"What we're trying here with the release is to get them through that first three- to four-month period, when predation is extremely high and mortality is extremely high," said Michael De Luca, director of the Aquaculture Innovation Center.
Last year, researchers at the center hatched a few thousand eggs, partially to study the early life cycle of the horseshoe crab and partially as an experiment to see if they could raise the eggs through the critical few months. The project was a success, and this year the center vastly expanded the effort. Using a grant from the DuPont Clear Into the Future program, researchers hatched more than 250,000 eggs they collected off a Delaware Bay beach in early June.
Typically, about 10 percent of the hatchlings die every time they molt, said Caitlin O'Brien, a research technician who uses the crabs as an environmental education lesson for area schoolchildren and the general public.
One of the difficulties, De Luca said, is that horseshoe crab hatchlings are rather secretive for the first few months of their lives. They hide in the mud or under the sand and, for about three months and three molts, live off their yolk sac, which comes with them from their egg.
While the vast majority of the hatchlings were released so they could burrow into the mud for the winter, the center will keep a group of the hatchlings to tag and observe for one year.
"This gives us a chance to figure out what their overwintering situation is," O'Brien said.
Finding a way to increase the number of horseshoe crabs has been a priority for researchers and wildlife conservationists, particularly as numerous migratory shorebird populations that rely on vast amounts of the eggs every spring have dwindled. Commercial harvesting of the crabs, for use as bait for the conch fishery as well as the catch and release done by the medical industry, has caused the crab population to crash.
New Jersey has a moratorium in place for harvesting of the crabs, and wildlife surveys through Delaware's Department of Natural Resources and Environmental Control show a tiny increase of the number of juveniles during the past few years. However, the crab takes about nine years to sexually mature.
Last month, the U.S. Fish and Wildlife Service proposed listing the red knot as a federally threatened species, citing fewer horseshoe crab eggs available for the birds to eat every spring as they stop off along the Delaware Bay on their journey to the Canadian Arctic.
These are all important lessons for students in classrooms learning about the environment, De Luca said. And that's why a handful of students from Cape May Technical School spent a few hours on a recent Saturday morning touring the center and helping with the release.
Learning about what researchers do at the center and how that affects the world around him were among the many lessons Joshua Musick, 15, said he learned before he helped O'Brien release one of the adult males that spent the summer living in a tank.
"This is, like, real life natural sciences," he said, "and it's really cool to get the experience."
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