OXFORD — — "Fish on!" called P.J. Klavon, as he reached for a trap hauled from the placid waters of the Tred Avon River. Inside the black metal cage wriggled a single white perch, a safe distance from a blue crab.
The fish weren't exactly jumping last week into the Bay Commitment, a 41-foot research vessel owned by the National Oceanic and Atmospheric Administration. After a morning's work collecting more than 100 traps set in the river the day before, the vessel's crew had seen barely a half-bushel of crabs, fewer than two dozen fish and a single eel. Klavon, a lieutenant junior grade in NOAA's uniformed service, didn't have many opportunities to sing out.
Fortunately for these trappers, they were fishing for science, not a living. And all their catch went back into the water to live another day after being painstakingly measured and tallied.
The Tred Avon is targeted for a $14.3 million oyster restoration effort, jointly underwritten by Maryland and the federal government, to begin later this year. The NOAA vessel has been fishing the river monthly from spring through fall since last year to see how many fish and crabs hang out in the water near Oxford.
"We're trying to determine if oyster reef restoration increases the numbers and diversity of fish," said David G. Bruce, an ecologist with NOAA's Chesapeake Bay office. "What are the benefits, aside from increasing the numbers of oysters, provided by this very large federal and state effort?"
Of course, Bruce acknowledged, every fisherman worth his salt knows there's a greater likelihood of catching fish around viable reefs. Research has shown how vessels sunk in the Atlantic Ocean have become havens for all kinds of marine life, as fish find food and places to hide in the nooks and crannies of underwater structures.
But the ecological impacts of rebuilding reefs in the bay have not been as thoroughly documented or quantified, Bruce said. Such knowledge could prove useful as policymakers work to complete an ambitious, costly and as-yet-unproved strategy for rebuilding the Chesapeake's depleted oyster population.
Ravaged by more than a century of overharvesting and by diseases in more recent decades, the bay's oysters have staged a partial comeback in recent years, largely because of favorable weather trends. The recovery, however, has been spotty, as many of the reefs on which the bivalves once grew have been lost over time, smothered in silt.
State and federal agencies are trying to jump-start the oyster restoration in 10 Maryland rivers and tidal creeks by 2025. They are building reefs with bargeloads of rocks and old shells, then planting hundreds of millions of hatchery-reared baby oysters on the new structures as well as on surviving reefs that have sparse shellfish populations. The targeted bay tributaries all were put off limits from commercial oystering under a 2010 plan by the administration of Gov. Martin O'Malley to expand sanctuaries for the shellfish while encouraging oyster farming and working toward a more sustainable public fishery.
The first to get a makeover under the plan was Harris Creek, an offshoot of the Choptank River near St. Michaels, where the Army Corps of Engineers is in the final stages of establishing 377 acres of oyster bars, depositing nearly 400,000 tons of granite and old clam shells at various places on the bottom to form new reefs, providing the hard surfaces to which the bivalves need to attach.
Maryland's Department of Natural Resources, meanwhile, has taken the lead on restoring 342 acres of reefs in the Little Choptank River, in that case using fossilized oyster shells from Florida because there aren't enough fresh shells available.
The move has been controversial, as commercial watermen — already unhappy about losing the ability to harvest oysters in the expanded sanctuaries — complained that the fossil shells were caked with dirt that was clouding the water and potentially harming fish and shellfish. State officials responded that the sediment was only a small percentage of what was being dumped overboard and did not pose any hazards or threaten the oysters to be planted there.
The Tred Avon is third in line. Plans are to restore 191 acres of reefs there and plant 860 million "seed" oysters spawned at the University of Maryland's Horn Point hatchery near Cambridge.
Scientists have been commissioned to monitor the restored reefs and see how the oysters survive and spread through natural reproduction to other areas. The Tred Avon, however, is the first site where officials are trying to assess the benefits of the effort to other bay fish.
Since last year, researchers have been stringing a variety of fish and crab traps in 18 lines under water, to check fish abundance and diversity over both existing oyster reefs and sandy bottom. Once the restoration work is done, they plan to return for three more years of sampling to see what has changed.
The preliminary sampling isn't finished yet, but so far, Bruce said, there doesn't appear to be much difference in the number of fish and crabs caught over existing, thinly populated oyster reefs and barren bottom.
On last week's fishing excursion, many traps came up empty, despite the powerful allure of ground-up menhaden and razor clams inserted in each as bait. Madison Fort, a Texas A&M fisheries biology major interning with NOAA this summer, dutifully tallied zeros for the empty traps.
The relatively cool weather this spring and summer may be affecting some fish, suggested Andrew Turner, a fisheries specialist with Versar, a private consulting firm, who's working with NOAA. He noted there had been more crabbers working the river last year this time, and there had been more spot, a popular bait fish, caught then, too.
Turner and other researchers think that, in time, the fish population will change with the new reefs, which should offer more spaces for small fish and crabs to hide. But the scientists hope their labors — and the pain from an occasional crab pinch — pay off in more quantifiable ways.
"Everybody can tell you that reefs attract fish, said Howard Townsend, a NOAA ecologist at the joint state-federal fisheries laboratory at Oxford. The goal is to use data from the Tred Avon and other projects to refine a computer model of how reefs in the bay alter the ecosystem, he explained.
"Our ultimate goal is to be able to measure the benefits," Townsend said, and to parse out what the impacts are for commercial and recreational fishing, tourism and other activities which depend on a healthy bay. "We want to understand those benefits, ultimately, in terms of dollars and jobs."