Horseshoe crabs have been walking along the bottom of our oceans, bays, and sounds for millions of years. Their 10 legs, hidden beneath their flat dome-shaped exoskeleton and characteristically long tail, have carried them up and down shores in silence in May and June to lay their eggs, though many of those eggs don’t hatch.

Fishermen along the Atlantic coast wait for the female horseshoe crabs to come and lay their eggs above the high-tide line. It is then that they are taken from their habitats and used as eel and whelk bait. It seems at first glance that this is a callous harvesting, but when looked at closer, a simple chain reaction of supply and demand is at play.

Ancestors of the horseshoe crab have been around for 450 million years, which is 200 million years before the dinosaurs even roamed the earth. Horseshoe crabs are frequently referred to as a living fossil, yet now in 2014 their existence has come to be in jeopardy. There are four species of horseshoe crabs, however, the North American Limulus Polyphemus are “near threatened,” according to Endangered Species International.

Horseshoe crabs in North America can be found from Nova Scotia in Canada to the Yucatan Peninsula in Mexico. In New York, they are found year-round in the Long Island Sound, Great South Bay, and other areas along the coast of New York.

“If horseshoe crabs aren’t put on the endangered list, I believe that changes on their regulations could change things greatly. Species numbers would rebound if they simply weren’t harvested during their mating season,” Brian Hochstrasser, a Fisheries Observer for the National Marines Fisheries Service, a division of the National Oceanic and Atmospheric Administration (NOAA), told Medical Daily.

“But we can look at how lobster populations are regulated and have rebounded greatly in recent years up north. There, they have slot limits where individuals under a certain size, premature of breeding age and large individuals that produce thousands of times more and healthier eggs and genes than recently mature animals are released. This keeps the viable breeding females out in the wild,” Hochstrasser explained.

The horseshoe crabs make their way to shore for spawning season, usually in May and June during full moons when the tide is at its highest. Thousands of large females make their way onto the shore while males hold onto the back of their shells, so once the eggs are laid, the males can easily fertilize them.

A female can lay 90,000 eggs in one season, but only 10 offspring survive to grow and return to the water and complete the cycle. This is an optimal time for fishermen to harvest the crabs. It wasn’t always like this, though. Since the collapse of the lobster industry, many lobster fishermen made a natural progression to eel fishing for revenue, which brought the demand for horseshoe crabs up.

“They looked for another route to support themselves and chose whelk and eel fishing,” Edward Warner Jr., a commercial fishermen of Long Island’s Peconic and Shinnecock bays, whose family has been in the fishing industry for six generations, told Medical Daily.

Warner catches fluke and other fish, along with the horseshoe crabs. The problem with the horseshoe crabs, he believes, is not only the water quality but also newly built bulkheads and other construction that doesn’t allow horseshoe crabs to make it safely to shores to lay their eggs.

Horseshoe crabs aren’t just fished for the bait, however. Horseshoe crabs’ blood is extremely important to the biomedical industry because their unique blue cooper-based blood contains a substance called Limulus Amebocyte Lysat (LAL). This ancient substance thickens with Bacterial toxins, which is what makes it useful for testing the sterility of medical equipment and virtually all intravenous drugs.

The blood is notably blue because of the hemocyanin in copper, while human blood is red because of the hemoglobin from iron, which is why we don’t have the important blood-clotting protein. If anything leaks into their blood, the protein would trigger a clotting response and seal the bacteria or foreign substance from entering the rest of their system.

There is no other procedure that could test the purity of medicines with the same accuracy as the LAL test. and federal law requires any medical device that is inserted or injected into a human body must use LAL to test for bacterial contamination, according to the National Institutes of Health. Horseshoe crabs have played a vital role for anyone that has ever had an injectable medication. There is also research performed on the compound eye of the horseshoe crab, which has led to a better understanding of human eye vision.

For the past 30 years, the medical and research industry have been receiving live horseshoe crab deliveries from fishermen. The horseshoe crabs’ biomedical use has increased by an estimated 611,800 crabs captured in 2012, according to the Atlantic States Marine Fisheries Commission. There are only four labs in the world that extracts one-third of each horseshoe crab’s blood for research before they regenerate and are returned to the wild.

The Director of Research at Endosafe extracting lab in Charleston, N.C., Dr. Norman Wainwright calls this a “primitive antibiotic.” The blood is only found in horseshoe crabs and is so medically and financially valuable that only one-quart of horseshoe crab blood is worth $15,000 dollars.

“I used to cut up horseshoe crabs into fourths for bait. I can’t imagine how many hundreds of thousands of dollars just washed away in my hands,” long-time Southampton fishermen Tom Rutyna, told Medical Daily.

Aside from the medical benefits of the horseshoe crab, the crabs also remain as an invaluable part of the ecosystem. The Atlantic States Marine Fisheries Commission made established state-by-state quotas in all Atlantic states for horseshoe crabs harvested for bait. These regulations were enacted in the late 2000 in response to the decline in the horseshoe crab population.

“There has been a drastic decrease in horseshoe crab populations in Mount Sinai Harbor that I have observed in my lifetime,” Hochstrasser, who grew up on the north shore of Long Island, said.

Since the laws were enacted, the University of Delaware working alongside DNREC, DuPont scientists and commercial fisheries developed bait that is equally as effective but uses less horseshoe crab meat. They found that the eel and whelk are attracted to the protein in horseshoe crab eggs so instead of using an entire horseshoe crab, the bait is quartered and placed in a special mesh bag so only one horseshoe crab is needed.

This both decreases the amount of horseshoe crabs used and the expense it costs fishermen to use horseshoe crabs as bait. The enforced limit is predicted to reduce the amount of horseshoe crab used per bait from one full male to one-eighth to one-sixteenth of crab per catch. Brown seaweed, kelp, baking soda, citric acid and other food-grade chemicals are used as fillers and the ingredients are then compacted in a slab.

“There are also endangered birds whose migrations have historically relied on the horseshoe crab eggs for food and now that there are a lack of them, they are decreasing the numbers of these endangered birds even more. The birds like the red knot, but also many other threatened shore birds rely on the eggs as an important food source,” Hochstrasser said.

Nearly half a million shorebirds, including the endangered birds such as the red knot bird, rely on horseshoe crab eggs during their migration, according to the New York Times. The decline of the red knot population is just one example of how the decrease of horseshoe crabs can easily upset the balance of the ecosystem. If the red knots couldn’t consume enough horseshoe crab eggs during their two-week migration in the Delaware Bay, some of them wouldn’t be able to survive their 9,000 mile trip back to the Canadian Arctic.

“I remember wave after wave of horseshoe crabs. Up towards Westhampton there would be thousands of them if you looked down in five feet of water,” Rutyna recalled. “We would fill our 16-foot boat and the one behind it. It was ten cents for the female and a nickel for a male.”

Rutyna grew up in Southampton, N.Y., a town filled with bays and marinas located on the south fork of Long Island where he watched the horseshoe crab population deplete over last 30 years. His grandfather, who was on the Board of Trustees for Southampton, spent a majority of his life on the water where he taught Rutyna respect for the wildlife.

“Sometimes as a kid you could put on a snorkel and look down and see horseshoe crabs by the thousands,” Rutyna said. “It would be hard not to bump into them so we’d drop an anchor down and see them moving across the floor where the water was ‘clear as gin’ my grandfather would say.”

To save the horseshoe crabs from complete extinction, scientists all over the world want to include them in the Schedule IV of the Wildlife Act, which would label the crabs as an endangered species. If it goes through, the Act will check the improper use of horseshoe crabs for various purposes, which includes capturing them for bait or harming them.

“The number one killer of wildlife is environmental devastation,” Rutyna said.