Crab deep sea pipe
THE WEATHER TOOK A DOWNTURN, and white-topped waves tossed around the Hannah Boden. It was September 2014, and the fishing vessel was motoring along the Atlantic coastline of Virginia, hunting for a type of crustacean called the Atlantic deep-sea red crab ( Chaceon quinquedens ). These crustaceans live in the depths of Norfolk Canyon, a submarine gorge that begins about 60 miles off the mouth of the Chesapeake Bay and extends far below the ocean’s surface.
On board the boat, crustacean biologist Bradley Stevens struggled to keep his gear from scattering across the bucking deck. The scientist had hitched a ride in order to collect samples of the same crabs. He was no stranger to bad weather. Stevens had worked for more than 20 years as a fisheries biologist in Alaska where he kept an eye on populations of king crabs, monster crustaceans that live in the Bering Sea. There, he spent days out on the water, sailing on the sorts of boats made famous on Deadliest Catch, the reality show that depicts the rough seas and dangerous conditions that fishing crews face on the Bering Sea. But the conditions onboard the Hannah Boden were worse.
“We had eight-foot waves, and the wind was blowing,” says Stevens, now a professor at the University of Maryland Eastern Shore in Princess Anne. “I thought to myself, ‘Why am I doing this? Why did I leave Alaska to come here and do this?'”
It was a good question: the biologist is among the few scientists who study Atlantic red crabs. These crustaceans, with orangish-red shells and spindly legs, are bigger than the blue crabs ( Callinectes sapidus ) living in the Chesapeake Bay. But, as Stevens’s journey on the Hannah Boden shows, they’re also hard to get to. The crabs scuttle along the sea floor at depths of 600 feet to more than a mile below the surface. And unlike their shelled relatives in the Bay, red crabs are virtual unknowns: what they eat, how they reproduce, and what role they play in the deep sea’s ecology are all unanswered questions.
Stevens is trying to gather basic data about how red crabs eke out a living in the cold ocean. He hopes this information will become useful as red crabs face a number of challenges in the future. Those challenges include warming ocean temperatures and fishing pressure from boats like the Hannah Boden, which procure crabmeat for a niche seafood market.
Red crabs “are so poorly studied, and that means there are lots of things we can learn,” Stevens says. “Sometimes just getting your hands on them can give you new information.”
You can think of these elusive animals as Maryland’s other big crab. One of several related species of crustaceans that live in various deep stretches of the Atlantic, red crabs flank the edge of the continental shelf from Nova Scotia south to the Gulf of Mexico. Blue crabs are called swimming crabs because they can use their paddle-like rear legs to propel themselves through the water. But red crabs have no choice but to walk along the seafloor. Most live at greater depths than do the king crabs Stevens studied in Alaska, surviving in habitats that are “at the frontiers of our understanding” of the oceans, says Richard Wahle, a marine biologist at the University of Maine.
This sparse environment makes the Chesapeake Bay look like a spa: at these depths, there’s little to no light to navigate by, and water temperatures hover around 38 degrees Fahrenheit. Sustenance can be hard to come by, too, says Wahle, who has also studied red crabs. Like other deep-sea animals, these crustaceans often depend on food that sinks down from the surface. The carcasses of dead whales, for example, serve up a nutrition bonanza that the crabs can sniff out from long distances away. “They’re very tuned into their chemical environment,” he says. “They can hone in on these sources of food like oases in the desert.”
Scientists have made sporadic attempts to view red crabs in their natural habitat. For a study published in 2008, Wahle used a camera towed on an underwater sled to capture images of red crabs scuttling about in the deep. But such efforts are expensive and few and far between. Which is why, for Bradley Stevens, the Okeanos Explorer presented a new opportunity.
Stevens got help in fall 2014 from the crew of the research vessel, which is operated by the National Oceanic and Atmospheric Administration (NOAA). The Okeanos Explorer participated in a series of research expeditions in recent years that investigated the Atlantic’s deep-sea habitats (see The Grand Canyons off Our Coast). The Okeanos crew lowered a camera-equipped, remotely operated underwater vehicle, or ROV, on nine dives that probed the Atlantic’s underwater gorges, including Norfolk Canyon. This robotic explorer was more maneuverable than Wahle’s sled-mounted camera. The ROV could swivel and home in on objects of interest and pipe its video footage live to computers on land.
Stevens, who had moved to Maryland in 2009, saw a chance to collect valuable data on red crabs. He assigned his students to watch the mission footage in two-hour shifts as it streamed in real-time on their lab computer. Each dive started at 8 a.m. and wrapped up at around 4:30 p.m., and for those hours, Stevens and his students stayed glued to the computer screen.
As the ROV explored the underwater canyons, the students spied expanses of muddy bottom and sites where corals clung to rocky cliff faces. If the students spotted a crab, they sent a message to the Okeanos team, which recorded the observation in the mission’s official log.
“When they were doing the dives in the Norfolk Canyon, it was super interesting because there were red crabs all the time,” says Stephanie Martinez-Rivera, a graduate student in Stevens’s lab who participated in the watch.
Some of the most important information that Stevens and his students collected, however, was basic data: where the red crabs lived and under what water temperatures. Such information is critical, Stevens says, because the oceans are changing. Even in the cold depths where red crabs live, water temperatures are likely to heat up in the coming decades because of climate change. That, in turn, could have consequences for red crabs. Warming waters could force the crustaceans into new habitats or shift when they time key events in their lives, such as when they reproduce.
It’s a phenomenon that scientists have seen before: every summer around July, American lobsters ( Homarus americanus ) in New England stage a mass migration from their deeper water habitats toward the shore. In 2012, however, an ocean heat wave hit the East Coast, and lobsters wound up making their move three weeks earlier than normal. That year, commercial fishermen caught a record number of crustaceans. Without basic data, however, scientists would have no idea if something similar happened to red crabs.
“I’m hoping that we’ll be able to set some baselines and look back on them in 20 or 30 years and say, ‘Oh, these cycles have changed,’ or ‘the temperature environment has changed,'” Stevens says.
But warming waters aren’t the only uncertainty in the red crab’s future. Another comes in the form of a crab trap.
Like the crustacean biologist, Jon Williams got his start with king crabs in Alaska. In his case, he was harvesting them from boats in the Bering Sea. Looking for work a little closer to home, the Maine native got a job in the mid-1990s working for a relatively new industry: the red crab fishery. Today, Captain Williams owns the Atlantic Red Crab Company, the sole harvester of deep-sea red crabs in North America.
His operation is a modest one: the company operates four boats, which sail throughout the year. Three of them are based in New Bedford, Massachusetts, while the fourth — the same Hannah Boden that carried Stevens into the fall storm — docked in Newport News, Virginia, in 2014 and 2015. The four boats target deep-sea habitats between New England and the Mid-Atlantic Bight, including canyons off the coast of Maryland.
Some of the gear differs, but hunting for red crabs is similar work to harvesting king crabs. Williams’s crews drop lines of 150 crab traps, bigger than those used by crabbers in the Bay, down to the sea floor. When his crew pulls the traps back up, they can collect thousands of crabs in a single go. Every year, his boats bring in about three million pounds of red crabs valued at roughly $3 million. That’s a small sum compared the $50 million worth of blue crabs caught annually by watermen in Maryland.Crustacean biologist Bradley Stevens struggled to keep his gear from scattering across the bucking deck. The scientist had hitched a ride on the Hannah Boden in order to collect samples of the Atlantic deep-sea red crab. Chesapeake Quarterly, Maryland Sea Grant’s quarterly magazine, reports on research, extension, education and other Chesapeake Bay issues and activities of interest to the marine community. It is produced and funded by this program, which receives support from the National Oceanic and Atmospheric Administration. Editors, Michael W. Fincham and Jeffrey Brainard; Production Editor and Art Director, Sandy Rodgers.
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