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2007
Volume 5, Number 4
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Counting
Blue Crabs
in Winter

Back

Miller, with his quiet manner and steady focus, played a central role in providing the group with understandable estimates of Bay crab stocks and fishing pressure. He led meetings of researchers from different laboratories around the Bay to reach an important consensus: that there was a point at which fishing pressure could threaten the blue crab, and we were right on that danger line.

In countless meetings Miller presented this warning to politicians, to environmentalists, to watermen. The force of this and other scientific information led the Bi-State Committee in 2001 to issue an Action Plan for managing the Bay's blue crab fishery. The plan called for establishing the first-ever Baywide thresholds for the blue crab fishery.

"It was remarkable to see Tom Miller's evolution," says Ann Swanson, Executive Director of the Chesapeake Bay Commission. "Just to see how much he grew in terms of explaining these complex ideas in his head, and how he was able to express all those ideas in a way that people could understand."

Miller gives a lot of credit for the success of BBCAC and the work that followed it to the strong state and federal funding support that researchers have received and to the good science that's come out of it. "We wouldn't be having this conversation," he says, "without all this work that's gone on for the last ten years."

Though Miller is a modest man, and declines to take credit for the importance of his role in the crab debate, in 2001 UMCES presented him with the President's Award for Excellence in the Application of Science.

In 2005 Miller and other researchers released a new analysis of Bay crab stocks, funded by the Chesapeake Bay Office of the National Oceanic and Atmospheric Administration (NOAA). This assessment confirmed that fishing pressure on the Bay's blue crab stock had reached dangerous levels during the late 1990s and early 2000s.

Correcting for changes in past recordkeeping, the researchers found that the biggest catch of blue crabs occurred back in 1966, and the lowest came in 2001. In fact, 2000, 2001, and 2002 catches were all at the bottom of the list. Miller and his colleagues found that fishing pressure — at its worst when stocks are low and fishing effort is high — crossed into the danger zone three times: in 2001, 2002, and 2004.

In Miller's words, in the years immediately prior to 2005 we had been "skating on thin ice." In 2005 fishing pressure dropped below the target, and the stock size increased enough to move away from the precautionary zone (see graph at left).

Even with recent improvement in the stock, the Bay's blue crab population continues to linger below the long-term average.

Having spent more than a decade laboring to understand the blue crab population, Miller still worries about how we manage the Chesapeake's great crab factory. In particular, he asks, when will we establish a well-thought-out target for fishing pressure, a level that will allow productive harvests without threatening the crab stock?

In fisheries science a target represents where you do want to go, in contrast to a threshold, which defines where you don't want to go.

The thresholds drawn by BBCAC set the limits of fishing pressure and of stock size. BBCAC also set a target that would keep fishing pressure comfortably below the danger line — and preserve 20 percent of the spawning stock to ensure future generations of blue crabs.

The thresholds and the target were major accomplishments, says Miller, but he still isn't fully satisfied. The target may be right in terms of general stock dynamics, he says, but he's disappointed that it doesn't do more. "What kind of fishery do we want to manage for?" he asks. "Do we want more hard crabs or more soft crabs? Do we want more protection of females? In certain places? At certain times?"

His biggest disappointment is that in the Chesapeake Bay, and especially with BBCAC no longer funded, there is no effective forum for discussing these issues or making these choices. "We need to move forward collaboratively [working with the watermen]," he says. "This is our biggest challenge."


End Game

Aboard the Mydra Ann, the crew hauls the Virginia dredge over the roller and onto the wide stern. Weber and Brown each grab a side of the net and spill oyster shells onto the platform, but this time there are a few live oysters in the pile and dangling from the net two good-sized male crabs. Weber pulls them off and sets them down so Walstrum can measure and weigh them.

The bigger one measures 159 mm (over 6 inches) from spine to spine and weighs in at 272 grams (almost 10 ounces) — definitely a keeper if this were summertime and you were stocking up for a crab feast. But this is a survey, not a hunt, and Walstrum flicks the Jimmie crabs back into the water. Will they survive? Hard to say, he says. Walstrum believes that the smaller the crab the better chance it has. Then again, the water's not too cold so far this winter — with any luck the crabs will seek the mud and wait for spring.

The Mydra Ann, almost 14 feet wide and powered by a 375-horsepower Caterpillar diesel, steams steadily from station to station through one-foot seas. When headed up-wind, the cuddy cabin helps to block cold spray thrown back from the bow. Inside the cabin a heater keeps the crew warm between stations, though it's not too cold today. Not like some days, when they endure freezing rain or snow. According to the crew, it has to blow a gale before they'll call off a survey trip.

It's also unlike other days when a single dredge may bring up as many as a 100 crabs. On those runs Morris has to power around in circles until they can count and measure them all.

The next scrape is not one of those big hits, but a half dozen crabs come aboard, including a male with a bent claw and a large female (called a sook). Though the winter dredge survey cannot tell us why these crabs have come to the deeps off Kent Island, it provides us with the concrete particulars. It shows, without prejudice, where the females are in winter, where the males are. Because hibernating crabs don't move, it allows the design of a random survey, plotted over miles of Bay bottom.

The results have been remarkable. Thanks to the winter dredge survey resource managers now have some confidence that they can approximate how many crabs (see graph, p. 10), and of what size and sex, inhabit the Chesapeake Bay.

Despite our new knowledge, mysteries remain. We still can't determine the age of blue crabs, and we still don't know how old they get. We don't fully understand the effects on blue crab stocks of prolonged periods of low dissolved oxygen or dying Bay grasses. Most importantly, researchers are not certain what's happening to female crabs in the Chesapeake. While the winter dredge survey shows female crab numbers evening out, an annual assessment by VIMS shows a disturbing picture of decline that has lasted more than a decade. (See The Case of the Missing Females)

As Roger Morris powers the Mydra Ann back to the Kent Narrows marina, he too voices concern. He knows a half dozen watermen who have left the crab business and gone to work on tugboats. It's a steady job and it keeps them on the water. "The water is all they know," he says.

Morris sees fewer and fewer young people going into commercial fishing, and as he turns into his slip he says, "Just look at the boats in this marina. They're all run down. It's a shame."

Working the water, he says, "it's history."

And yet there are still blue crabs in the Chesapeake. Sooks still migrate toward the sea each fall, and a new crop of crabs moves up the Bay each spring, spreading into countless rivers and creeks, where even children can catch them with a chicken neck. So far blue crabs keep playing their role in the food web, as key predators and scavengers. And as long as there are blue crabs in the Bay, we have to believe that there will be men like Morris who, despite the economic odds, will go out to catch them. This is because one mystery surrounding blue crabs remains — how they take whatever they find on the bottom of the Bay and through some divine alchemy transmute it into the sweetest seafood. If we can find the right balance between catching crabs and conserving them, we can only hope that this magic will endure.


For More Information

Blue Crabs in the Chesapeake (Maryland Sea Grant)
www.mdsg.umd.edu/crabs
Annual Blue Crab Status Reports and publications from the Chesapeake Bay Commission
www.chesbay.state.va.us/bluecrab.htm
General Background from the Chesapeake Bay Program
www.chesapeakebay.net/crabshell.htm
Blue crab research at SERC
www.serc.si.edu/labs/fish_invert_ecology/index.jsp
Blue crab research at COMB
www.umbi.umd.edu/~comb/programs/aquaculture/bluecrab.html
Stock Assessment Report
hjort.cbl.umces.edu/crabs/Assessment05.html
About the Bi-State Blue Crab Advisory Committee
www.chesbay.state.va.us/archives.html
Maryland Crabbing Information and Regulations
www.dnr.state.md.us/fisheries/crab/crabindex.html
Virginia Regulations
www.mrc.virginia.gov
Virginia Trawl Survey
www.fisheries.vims.edu/trawlseine/mainpage.htm
Paper on the Bi-State Blue Crab Advisory Committee:
Betsi Beem. 2006. Planning to Learn: Blue Crab Policymaking in the Chesapeake Bay. Coastal Management, 34:167-182.
Elizabeth North holding a jar of crab larvae

A team of researchers, led by Elizabeth North (shown above with a jar containing crab larvae), is currently tracking tiny blue crabs that drift offshore and then journey back into the Chesapeake and Delaware bays. Learn more about this regional effort supported by the Sea Grant programs of Maryland, Delaware, and Virginia at northweb.hpl.umces.edu/research/BlueCrab_SG.htm.

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