Increase in harvest an oyster shell game


Motor: Results of highly efficient power dredging can distort notion of mollusk's health.

February 25, 2005|By Tom Horton | Tom Horton,SUN STAFF

What do Maryland's oysters have in common with Major League Baseball?

Both need asterisks.

With baseball, you need the footnote, the fine print, to let us know baseball's outsized home run production in recent years might have something to do with players being on steroids.

Similarly, oysters need an asterisk to let us know that this year's much-improved production of bivalves might have something to do with watermen mostly being - so to speak - on steroids.

We're not talking substance abuse; rather a landmark conversion to highly effective power dredging in an industry the state has always regulated by limiting harvesters mostly to less-efficient sail power and stationary tonging.

This winter's oyster harvest is on track to double* (please note asterisk) last year's historic low of 26,000 bushels. That doesn't mean oysters are back, not given the fact that harvests during the last few decades were in the millions or hundreds of thousands of bushels.

But it is a remarkable turnaround, good news for watermen and seafood processors. But what about for the oyster?

How much does the "improved" oyster production just represent "improved" harvest methods, rather than a comeback of oysters?

Chris Judy, a veteran oyster manager at Maryland's Department of Natural Resources, discounts the effects of power dredging.

The upturn in harvests, he says, is largely genuine, reflecting a return to wetter years, following droughts earlier this decade.

Wet years mean more freshwater flows into the bay, lowering salinity and depressing the impact of oyster diseases that have played a huge role in the oyster's overall demise since the 1950s.

Power dredging or no, there's no way we'd be seeing a doubling of harvests this year unless many more oysters were surviving the diseases due to fresher water, Judy says.

DNR doesn't think the harvest needs an asterisk.

There's little doubt that improved survival is a big factor in this winter's improved numbers. But it's hard to discount power dredging.

"When you're faced with the crash of a species, you don't make it easier to catch them," says Roger Newell, a University of Maryland oyster scientist.

And we have clearly made it easier. Rough estimates provided by DNR show the following oyster harvest breakdown this year, by types of gear:

Power dredging - dragging toothed, iron dredges behind motorized work boats - appears to be bringing in 75 percent of this winter's oysters.

Another 5 percent comes from skipjacks, and that effectively is also power dredging, as these historic sailcraft seldom oyster anymore unless it's on the two days of the week they are permitted to use powered "push boats."

The remaining 20 percent of the harvest is distributed about equally between divers and hydraulic - or patent - tongers (9 percent each), according to DNR's estimates.

Both of these are stationary harvesting methods, which don't work unless there's a fairly dense population of oysters.

Power dredgers, on the other hand, can plow many acres of bay bottom in short order, taking oysters even where they are thinly spread.

Hand tonging, the way most oysters traditionally were taken from the bay, is now accounting for an estimated 2 percent of the harvest.

DNR's Judy concedes power dredging "is more effective," but argues that his agency's interviews with watermen show patent tongers taking about the same harvests, per boat, as power dredgers.

He says the totals wouldn't be all that different this winter even without any use of power.

My own interviews with watermen, hardly amounting to a formal survey, indicate that many wouldn't even be out there trying if not for power dredging.

Power dredging was banned in Maryland in 1867, and allowed only on a very limited basis until recently. Between 1999 and 2003, DNR and legislators allowed watermen to dramatically expand power dredging to nearly a quarter of the Maryland bay (power dredging has also expanded in Virginia's portion).

DNR is negotiating with watermen to further expand the use of power into other portions of the bay.

There is nothing inherently wrong with the use of power dredging - though in some areas it might be damaging to the bottom, something DNR seems to realize.

In theory, you could have a single, large power boat doing all the oystering, if that's the way you wanted to produce the harvest.

But you would have to set limits on catches accordingly - manage things very differently than when you had lots of small, inefficient harvesters (i.e. sail and tongs).

And I worry that DNR has allowed a large-scale and probably permanent change in the way oysters are caught, but has not thought through the management implications.

I worry that the next time environmental conditions change to favor the oyster diseases, the following trough in harvest numbers may make last winter's pathetic 26,000 bushels look good.

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