Monday, November 19, 2007
The Chesapeake Bay's famous blue crabs - feisty crustaceans that are both a regional symbol and a multimillion-dollar catch - are hovering at historically low population levels, scientists say, as pollution, climate change, and overfishing threaten the bay's ultimate survivor.
This fall, a committee of federal and state scientists found that the crab's population was at its second-lowest level in 17 years, having fallen to about one-third the population of 1993. They forecast that the current crabbing season, which ends Dec. 15 in Maryland, will produce one of the lowest harvests since 1945.
This year's numbers are particularly distressing, scientists say, because they signal that a baywide effort to save the crab begun in 2001 is falling short.
Governments promised to clean the Chesapeake's waters by 2010. But that effort is far off track, leaving "dead zones" where crabs can't breathe.
Maryland and Virginia have changed their laws to cut back the bay's crab harvest. But watermen have repeatedly been allowed to take too many of the valuable shellfish, scientists say. The watermen, meanwhile, say they're being unfairly blamed.
"Now it appears that even the hardy blue crab is approaching its breaking point," said Howard Ernst, a professor at the US Naval Academy and a critic of government efforts to protect the Chesapeake. If the crab's population drops further, Ernst said, "what we ultimately lose is not only a resource, but a unique and irreplaceable cultural heritage."
In the 1990s, the crab's population began to fall off rapidly. Since 2000, it has been at a historically low ebb.
There were about 852 million crabs in the bay in 1993, but there are now about 273 million, according to the committee of federal and state scientists, which issued a report in September....
And the immediate future doesn't look much better. The number of crabs less than a year old, a crucial indicator of how the population will look in the next year or two, fell last winter to its lowest level in 15 years.
The reasons for the decline probably include climate change, because the water now is often too warm for a grass species the crabs use as shelter.
But the causes also include two problems that governments have promised - and failed - to fix.
One is the water. Rain washes down manure, treated sewage, and suburban fertilizer, which cause algae blooms that remove oxygen from the bay's water. Low-oxygen "dead zones" can kill crabs or push them out of their preferred habitat.
State and federal governments promised to clean up the pollution by 2010. Now officials say the effort, led by the Environmental Protection Agency, is far behind schedule....
Maryland and Virginia, which share the bay, sought to limit the catch in 2001, with rules about what days watermen could work and the minimum size of crabs they could keep.
But, though the harvest went down, crabbers were still able to catch what scientists say is an unhealthy number of crabs in 2001, 2002, and 2004. And they're on pace to do it again this year, according to a recent estimate. The reason: Crab catches have declined, but the total number of crabs has dropped even faster...