Contemplate the vastness of the Grand Canyon, but picture it beneath the sea, where marine ecosystems are thriving, fragile coral is growing, and biological phenomena rarely seen anywhere else in the world are occurring.

Because, about 75 to 100 miles off the coast of New Jersey -- where the continental shelf divides shallow coastal waters from the deep sea -- a tale of two canyons is in play involving these geological hot spots.

The Baltimore Canyon and the Hudson Canyon, both considered national treasures, are among about 70 such areas along the mid-Atlantic coastline that are prized by fishermen for their rich species diversity and abundance of marine life.

"The canyons are where the fish are ... they're important resources that support our fisheries," said Michael Luisi, chairman of the Mid-Atlantic Fisheries Management Council, a Dover, Del.-based fishery management group representing the interests of commercial fishermen from New York to North Carolina.

But late last year, two aquariums filed applications with the National Oceanic and Atmospheric Administration (NOAA) to have the Baltimore and Hudson Canyons designated as national marine sanctuaries.  Earlier in 2016, a similar application for the same designation was filed to preserve the Norfolk Canyon, off Virginia.

Though all three applications state that the intention of the designation is not to limit commercial or recreational fishing access to the canyons, various groups expressed opposition.

The United States has 13 such federal marine sanctuaries, and the designation creates a sort of underwater national park that protects important ecosystems from oil drilling, marine mining, and other activities, and affords opportunities for recreation and scientific study.

The National Aquarium in Baltimore said it wanted to create a partnership between the city's educational and scientific communities to expose young people, particularly in underserved  urban areas, to ocean-exploration technologies and potential careers through a "robust set" of education programs. Representatives from marine industries, technology companies, and educational institutions had already begun to form a consortium supporting the idea.

But the aquarium withdrew its application recently, and fishery groups last month applauded the move, saying they would rather preserve their industry.

Baltimore Canyon -- about 80 miles southeast of Cape May -- is a 28-mile-long, five-mile-wide area that contains fragile, slow-growing deep sea corals not typically found in other mid-Atlantic habits. Naturalists say the habitats are so vulnerable that if they are damaged, they could take four centuries to replace. The corals appear to be the linchpin in a canyon dense with biologically important nutrients and natural chemicals that support a robust food web of bacteria, mussels, sponges, anemones, crabs, lobsters, and fish.

Perhaps equally important was the recent discovery in the canyon of the only methane cold seep in the mid-Atlantic -- one of the largest on the East Coast.

The deep-sea corals and the rare methane seep "form the basis of a unique ecosystem that nourishes and supports a rich food chain extending upward more than a mile into the water column," according to the National Aquarium's NOAA application.

Officials at the National Aquarium declined to be interviewed, but in a statement issued Feb. 1, its CEO, John Racanelli, said that after "careful consideration," the aquarium withdrew its nomination because the "timing is not right ... although we believe national marine sanctuary designation would provide an unprecedented opportunity to protect a national treasure and inspire young minds."

Racanelli said the aquarium plans to spend two years gathering additional "community input" and may submit another nomination for protection of the Baltimore Canyon in the future.

In a statement issued Friday, Racanelli reiterated that the aquarium had never sought to support "restrictions or limitations on any current activities in the Baltimore Canyon area, including commercial and recreational fishing."

Officials at the Wildlife Conservation Society's New York Aquarium say it is continuing to fully support its application for the 400-mile wide Hudson Canyon to become a protected marine sanctuary.  Formed more than 10,000 years ago during the last ice age, it is the largest undersea canyon on the East Coast and one of the largest in the world.

"Designating the Hudson Canyon ... provides an opportunity to permanently prohibit oil, gas, and mineral exploration and extraction from this sensitive habitat," said John Calvelli, the World Conservation Society's executive vice president for public affairs. "This will not only protect wildlife but also benefit commercial and recreational fisheries that depend on this productive ecosystem."

Some fisheries advocates don't see it that way.

"Our concern is always about having more restrictions and more regulations placed upon our industry," said Luisi, of the fisheries council. "Right now, these applications say they only want to restrict drilling and mineral extraction, but a year from now, as more and more people get involved in this process of creating a sanctuary, that focus could change, and the next thing you know, they are looking at trawling nets and lobster pots on the sea floor as a threat to that environment."

Dan Sullivan, 42, of Cape May, who has worked on commercial trawlers since he was "a kid," said the idea of "limiting the canyons in any way feels like a squeeze to fishermen."

Sullivan, who was at Cape May harbor, had just gotten off a three-day trip to a canyon last week and was seeking another voyage out to sea. "This is our livelihood ... anything that could affect it worries me," he said.

New Jersey legislators called the Baltimore Canyon application withdrawal a "big win" for the state's fishing and tourism industries.

"With our recreational and commercial fishing industry under constant attack from Washington bureaucrats, this is certainly welcome news for our region," U.S. Rep. Frank LoBiondo (D., N.J.) said in a statement. "I remain committed to fighting against such arbitrary restrictions on our fishermen."

Through a spokesman, LoBiondo declined further comment on the issue.

But others contend that not preserving the canyons could ultimately lead not only to environmental issues, but also a blow to the region's economy.

"By blocking this designation, the fishing industry is being selfish and only hurting themselves in the long run," said Jeff Tittel, director of the New Jersey Sierra Club.

Not creating the sanctuaries could lead to such activities as oil drilling and seismic testing off the coast -- and, ultimately, oil spills and other environmental issues that could decimate fish and other wildlife populations, Tittel said.

"Only a little bit of oil could jeopardize our coast, our multibillion-dollar fishing industry, and our tourism industry," Tittel said.