Bay Grasses Decline to Lowest Levels in More than a Quarter Century
"Perfect Storm" of Pollution and Parasites Threatens Popular Sportfish

Bay Crabs Take a Hit

Worrisome news today about blue crabs, one of the Chesapeake Bay’s most iconic critters and object of the Bay’s most profitable commercial fishery.

The crab population in the Bay is down dramatically from a year ago, according to Virginia and Maryland fisheries managers. Total crab numbers dropped from about 765 million last year to about 300 million, largely because the number of juvenile crabs fell from nearly 600 million last year – a record high -- to 111 million in 2013, the Virginia Marine Resources Commission (VMRC) said.

What happened to all the baby crabs? Scientists think most of them became dinner for predators. Over the last year or two, the Bay has seen a huge increase in juvenile red drum, a fish with a voracious appetite. Scientists believe great numbers of “puppy drum” ate great numbers of “puppy crabs.”

“There is a good chance that these fish had an impact on last year’s record year class (of baby blue crabs),” said Rom Lipcius of the Virginia Institute of Marine Science in a Virginia press statement. “Puppy drum are opportunistic feeders and will target high density food sources, and juvenile crabs last year were found in high densities. I was expecting a reduced number of juvenile crabs this year. Lower spawning stock numbers in 2012 may have combined with environmental factors to dampen reproduction this year.”

SpongecrabEnvironmental and pollution factors do indeed play roles in Bay crab numbers from year to year. Microscopic crab larvae that hatch in the lower Bay are swept by tides out into the Atlantic Ocean, then depend upon favorable winds, weather, and tides to sweep them back into the Bay to grow and mature. Unfavorable weather conditions at critical times of the crab life cycle can mean a lean year for the Bay’s crab population.

And pollution in Bay waters continues to stunt the Bay’s underwater grasses, which offer critical shelter for baby blue crabs to hide from predators like red drum. A report earlier this week found Bay grasses down this year to only 48,000 acres, the lowest since 1985. Some of the grass losses are due to weather, but excess nutrient and sediment pollution also are big problems.

“Bay grasses provide essential habitat and shelter for juvenile crabs and have been significantly reduced in recent years,” Chesapeake Bay Foundation (CBF) President Will Baker said. “Reducing pollution, including better managing stormwater runoff before it gets into rivers and streams, will improve water quality, contribute to Bay grass revival, and improve habitat for crabs.

“While progress has been made to reduce pollution, the Chesapeake Bay remains a system dangerously out of balance. Implementing the states’ Clean Water Blueprints will finish the job of restoring the Bay.” Twocrabs

There also was some good news in this week’s crab report. The number of adult female crabs increased 50 percent, from about 95 million a year ago to 147 million this year.

Adult females are the cornerstone of a joint Virginia-Maryland crab population rebuilding program that began in 2008.

“It is important to keep today’s news in perspective,” said VMRC Commissioner Jack Travelstead. “Five years ago this fishery was declared a federal disaster. That is no longer the case. Overfishing is no longer occurring. A good fisheries management framework is in place. The stock is healthy. Spawning-age females are doing well. If it wasn’t for a disappointingly small reproductive year class that showed a loss of more than 450 million baby crabs, we would have much to celebrate.”

Here’s how CBF Senior Fisheries Scientist Bill Goldsborough put it:

"Fluctuations in crab abundance are driven by the number of adult females, weather’s impact on movement of juvenile crabs into the Bay, and the survival of young crabs. It is disappointing that after 2011’s strong reproduction that so many juvenile crabs fell victim to degraded habitat. Apparently, last year’s poor reproduction was due to unfavorable weather, which we can’t control, and low numbers of females, which we can.

“Fisheries management policies must be guided by sound science. CBF strongly encourages Maryland, Crabclaw
Virginia, and the Potomac River Fisheries Commission to continue the collaborative approach that has brought about the positive trends in the Bay blue crab population. CBF supports reducing the catch as necessary to avoid exceeding the target fishing rate and maintain sufficient numbers of female crabs, crucial to the long-term health of the population.”

Because of the lower overall number of crabs, Virginia, Maryland, and the Potomac River Fisheries Commission are considering additional harvest restrictions of 10 percent in 2013. Combined with more favorable weather conditions and continued efforts to reduce pollution, the new restrictions should lead to more crabs in years to come.

That will be good for the Bay, Bay watermen, and crab lovers everywhere.

Chuck Epes Chesapeake Bay Foundation


Feed You can follow this conversation by subscribing to the comment feed for this post.

The comments to this entry are closed.