The soft shell clam’s meek return to Maryland waters is a bright spot on the Chesapeake Bay landscape. But an increase in the number of watermen going after them has renewed some fears that the nascent fishery could choke itself off before reaching its full potential.During hydraulic dredging, a suction tube vacuums sediment onto a conveyer belt from which watermen pick out the clams and release the rest back to the water. The process disturbs the bottom and can generate a sediment plume, both of which have the potential to harm the underwater grasses that are often located nearby. (Tyler Campbell)

Also called white clams, manos, longnecks and steamers, soft shell clams had all but disappeared from Bay waters, where they had been the source of a thriving fishery in the 1950s and ’60s. After decades of little-to-no soft shells in most areas, the clams have rallied the last five years, particularly in Maryland’s Eastern Shore rivers. And the number of clammers dredging for them has risen, too.

While watermen contend that poor water quality and bad weather have driven the shellfish’s downfall in the past, some river advocates wonder whether the clamor to harvest them — without an overall assessment of the population — has contributed as well. And some are asking whether an increased harvest, which relies on dredging to extract clams from the bottom, could have local impacts on water quality and the Bay’s underwater grasses.

Elle Bassett, the Miles-Wye Riverkeeper, said she can almost measure the increase in soft shells by the number of boats dredging in Eastern Bay, leaving plumes of stirred-up sediment suspended in their wake. But each time soft shells reappear, no one is sure how long they’ll stick around before a combination of factors beat them back to modest numbers.

“At what point do we start to try to avoid that massive drop-off while also getting the ecological benefits of this soft-shell clam?” Bassett asked.

The up-and-down nature of the beleaguered clam population merits more study, Bassett said. She and others in the ShoreRivers consortium of riverkeepers would like to see the state conduct an environmental assessment of the soft shell clam population to consider how many can be sustainably harvested each year.

Watermen are permitted to harvest soft shells year-round, with a daily catch limit of 8 bushels in the summer and 15 in the winter — limits that haven’t changed with fluctuations in the clam population. The clams have to be a minimum of 2 inches across. Virginia has yet to recover a viable population of soft shells or a market for them after the clam declined in the 1970s after Tropical Storm Agnes and the arrival of a parasite called Perkinsus chesapeaki, which went on to infect soft shells in Maryland in the 1990s.

Soft shells research waned with the industry decades ago, but scientists know that they filter water much like oysters and provide food for other species. In a 2011 report, the Maryland Department of Natural Resources estimated that soft shell clams once constituted at least 35 percent of the state’s large bivalve population, which includes oysters, razor clams and hard clams.

Razor and hard clams also are harvested by hydraulic dredge, though watermen are limited to where they can use the equipment that was introduced to Maryland in the early 1950s. The Maryland legislature banned hydraulic clam dredging in the state’s Atlantic coastal bays near Ocean City in 2007, a contentious decision at the time that shuttered that region’s clamming industry.

James Thomas with a load of razor clams at Bryantown Landing on the Wye River. He, like others, moved on to harvesting razor clams, sold as crab bait, after finding few soft shells in late summer. (Dave Harp)The technique used to harvest clams is called hydraulic dredging: a suction tube vacuums sediment onto a conveyer belt from which watermen pick out the clams and release the rest back to the water. The process disturbs the bottom and can generate a sediment plume, both of which have the potential to harm the underwater grasses that are often located nearby. Grasses and clams grow in similar conditions and their habitats can overlap, although grasses typically grow in shallower areas than soft shell clams.

Dave Blazer, the DNR’s fisheries service director, said the change in the coastal bays came after the number of boats running small portions of the coastline for hard clams quadrupled over a short period, scouring grass beds in some areas. He said the circumstances in the mid-Bay are different — even in years when the number of boats going after soft shells skyrockets.

“There’s a lot of space in the Bay, and clamming has been around for 60 or 70 years,” Blazer said. “There’s going to be isolated conflicts, but the Bay’s a big area, and I think we can accommodate a lot of these activities.”

The DNR completed a review of scientific studies on the environmental impact of hydraulic dredging in 2001, and it details some of the differences between dredging off the coast versus in the Bay and its rivers (though most of the research focused on coastal bays). In both cases, “the direct impact of dredging in seagrasses is catastrophic,” the report states. The indirect effects of dredging, such as the plumes of sediment left behind and their impact on nearby grass beds, “are less clear.”

Potential impacts on the aquatic ecosystem were nearly a moot point when there were hardly any clams to harvest. As recently as 2013 and 2014, according to DNR data, there were just eight watermen bringing in 278 bushels of soft shells in Maryland. But when that number rose to 31 boats harvesting 17,468 bushels of the clams two years later, river advocates began to take notice.

Over the same five-year period, the Bay’s underwater grasses have expanded their reach at a record-breaking clip, flourishing under improved water conditions. Maryland law does not allow hydraulic dredges to be used in grass beds, but those rules could be more difficult to enforce if both grasses and soft shell clam harvests expand.

The ShoreRivers group is closely watching the grass beds that the DNR marks as off-limits to dredging to ensure that they match surveys of grass beds conducted by the Virginia Institute of Marine Science, alleging they have not aligned in the past.

Rebecca Golden, program manager for resource assessment services at the DNR, said that the department is discussing how a variety of human activities, including hydraulic dredging, interact with the grasses as their acreage grows. A workgroup at the state-federal Chesapeake Bay Program, for example, is looking at whether the laws regulating activities around grass beds are protective enough.

The DNR is required to mark off protection zones for the grass beds as they are mapped by aerial surveys. Areas that have grasses or have had them in the last three years are off-limits to hydraulic dredging, bottom dredging and harvest by shinnecock rake. They are also to be marked with landmarks and buoys.

Blazer said the agency is in the process of completing update of those protection zones for 2019, which will be posted publicly. The updates are included in the information packet that comes with a new clamming license, along with notices about shoreline setbacks or natural oyster beds that are also off-limits to the equipment.

The number of licenses doled out for soft shell clams has risen steadily the last five years as word of their comeback spread, though only about half of the watermen who get a license end up reporting back with a harvest. The number of people who declared their intent to harvest soft shells rose from 85 in the 2015–16 season to 170 the next year, with about half reporting a harvest each year. The harvest numbers were not yet available for the 2017–18 season, but Blazer said that 179 declared an intent to harvest soft shells, and he expects about half did.

This season was shaping up to be a banner year for both Bay grasses and soft shell clams, which were once a food staple in the Bay but are now mostly sold to markets in New England. But heavy rain that started in July left the habitats where soft shells grow deluged with freshwater and sediment. The clams, which prefer higher salinity, had “gotten hammered” by the time the DNR went out for a survey later that month, Blazer said. During surveys, the grasses appeared to have suffered from the deluge as well.

“Our folks did not see that many [soft-shell] clams, and those they did find were stressed,” Blazer said, though there were small clams among them that could bounce back for future harvests. “We’re in the southern range of where these clams are [on the East Coast]. If the environmental conditions are right, they’ll be here in good numbers. But if it’s not, they’ll disappear for a couple of years.”

James Thomas, an Eastern Shore waterman, said that he, like many others, moved on to harvesting razor clams, sold as crab bait, in other parts of the Bay after finding few soft shells in late summer. But he doesn’t think dredging, which has been taking place in the Bay since midcentury, is contributing to the rise-and-fall cycle of soft shells.

“Mother Nature can do more in 30 minutes than we can do with a clam rig in five years,” said Thomas, 34.

He said that his great-grandfather, Medford Thomas, was one of the pioneers of the state’s clamming business in the 1940s. His family continued the tradition through the boom years when hundreds, not dozens, of boats were dredging the Bay for soft shells, and through the bust years when there were none to be found.

“The soft shells made a comeback, but that was due to water quality,” Thomas said. “Fix the water quality and the Bay will fix itself.”

Thomas said that grass beds are something clammers would want to avoid even if there weren’t regulations requiring it, because the grasses clog the equipment and are cumbersome to remove. But some studies included in the DNR’s review found that, even when the dredge stays out of the beds, the plume of sediment they leave behind could have an impact. Silt and clay particles common in river bottoms can remain suspended in the water longer than sand, particularly when the harvest takes place in shallow areas.

The report found that little information was available about the broader impact of dredging on the habitats where clams live, but many of the impacts are mitigated by preventing the dredge from being used in grass beds.

Bassett said each of these factors should be considered in setting more precise parameters for the boom-and-bust fishery.

“It’s hard to do a stock assessment of [soft shells], but I’m not aware of any studies that have even tried,” Bassett said, noting that hard clams in the state’s coastal bays are regulated by a fishery management plan. “Every harvest we have in the Bay should be looked at: How does it benefit the economy and the ecology?”