Good news arrived last month well in advance of Memorial Day weekend, the unofficial start of summer and, at least in these parts, its requisite crab feasts. The Chesapeake Bay's blue crab population appears to be on an uptick, having recovered somewhat from a disastrous 2014.
The annual winter dredge survey which looks at 1,500 sites in Maryland and Virginia has revealed there were a lot more crabs buried in the mud this winter than last, which, when extrapolated, translates into an estimated 411 million crabs living in local waters. That would represent a 38 percent increase from last year, which was a bit of surprise given how the harsh winter weather with its subfreezing temperatures took its toll on the population — a 28 percent mortality rate in icy Maryland alone.
Perhaps more important, the female crab population rebounded particularly well, up from 68.5 million last year to 101 million this year. As a single female can produce between 750,000 and 2 million eggs at a time (and rarely lacks for fertilization), preserving the Chesapeake Bay's population of mature females, or sooks, is considered vital.
Yet it would seem premature for the Maryland Department of Natural Resources to seriously consider lifting harvest restrictions imposed after last year's disheartening drop in crabs. Since the winter dredge survey started in 1990, crabs have generally been more abundant, peaking at more than 800 million in some years. And experts warn that pre-1990 might have been far better — that even 800 million may constitute a bit of a slump in a larger context.
Watermen aren't chiefly to blame for the decline in blue crabs today or for the past half-century or more. The bigger culprits remain the rise of pollution and the loss of important habitat like underwater grasses that protect baby crabs. But alas, until people living in the watershed clean up their act — reducing the growing problem of nutrient-laden stormwater runoff, for instance — harvest restrictions are the best tool available to make sure there will be crabs in future years and that the species won't fall off the map.
Ask anyone who makes their living on the water, there have always been big variations in the crab harvest from year to year. Historically, that's largely because of the uncertainties of crab reproduction — at the larval stage, the tiny organisms depend on favorable winds and currents at the mouth of the Chesapeake Bay to keep them from drifting out to the Atlantic.
But the chances of successful reproduction have diminished mostly because of man-made factors. Increasingly, scientists suspect global warming may play a role in raising water temperatures and changing currents in a way that has worked against crab reproduction. Increasing levels of nitrogen and phosphorus cause algae blooms, a drop in dissolved oxygen and a loss of aquatic vegetation and the benthic organisms the shellfish need to survive. The result? Crabs have fewer places to live, feed and reproduce.
Meanwhile, watermen are more dependent on crabs for their livelihood as the stocks of other seafood fare like oysters, clams and striped bass have suffered as well. That's made it tough for those who make a living on the water — and one reason why a total moratorium on crabbing has never been justified. The hardship it would cause to communities like Smith Island and Crisfield would be nothing short of devastating.
Still, it's reasonable to be encouraged by the survey results. The species has exceeded expectations — if only modestly — and Marylanders can dine on steamed crabs this summer without guilt (aside from the calories involved). But caution is in order. The numbers could easily fall again, and given the bay's poor water quality, the ability of crabs to bounce back is less certain than ever.
That's why Maryland and Virginia need to continue to find ways to reduce pollution not only from stormwater runoff but from agriculture, sewage treatment plants, failing septic systems, development and other sources. Crabs may not be the perfect barometer of the Chesapeake's health, but they're certainly one that captures the public's attention. Like the bay, the species has demonstrated a resiliency but not an unlimited one.