ANNAPOLIS – With a decline in the Chesapeake Bay’s underwater grasses, scientists are worried about the fate of the blue crab this year.
Bill Goldsborough, director of the fisheries program for the Chesapeake Bay Foundation, said there may be a “significant decrease” in the overall bay-wide catch this year as a result of a 25 percent drop in bay grasses, or submerged aquatic vegetation, over the past year.
“Grasses are an essential habitat for blue crabs,” said Goldsborough. “If there aren’t enough underwater grasses then they don’t have enough protection and there is more loss to predation.”
Juvenile and soft crabs use the grasses to hide from predators like rockfish and sandbar sharks. Without the vegetation, the juvenile crabs could be eaten before they are able to grow up, according to Goldsborough.
The bay grasses decrease in 2006 was due to a dry spring followed by a heavy rainfall in June, according to a survey released Wednesday by the Chesapeake Bay Program. The dry weather raised salinity levels and the subsequent rainfall muddied up the bay, reducing sunlight.
The bay grass loss is especially important for the work of Dr. Yonathan Zohar, director of the University of Maryland Biotechnology Institute’s Center of Marine Biotechnology. He is researching the breeding cycles of blue crabs, which he hatches in his lab and then releases into the bay.
“The overall long-term picture is that it reduces the nursery habitats which will result in less crabs making it to maturity either in the wild or the crabs that we release,” said Zohar.
Zohar has released the crabs he breeds into these nursery habitats – or grassy bay areas – each spring for the last five years.
But the Department of Natural Resources says the issue is still too soon to call. Harley Spier, a fisheries manager at DNR says there are too many components that affect blue crab populations and the department does not plan to change any of the crabbing regulations for this season which opens April 1.
Spier says there have been instances in the past where bay grasses have declined but crab populations have remained stable. Although the grasses provide the best hiding place for the crustacean, submerged logs and muddy spots on the bottom also provide sufficient cover.
Zohar is currently releasing his juvenile crabs into different types of environments such as muddy areas, although he says bay grasses are the best.
Professor Robert Orth of the Virginia Institute of Marine Science says the declining bay grasses could be an example of the growing threat of global warming and how it may affect the bay.
“Ten years ago people would have never said global warming was a problem. Global warming is now part of the picture especially for eelgrass,” said Orth.
Eelgrass, a common species all over the bay, likes cooler temperatures. The summer of 2005 was one of the hottest on record and killed much of the eelgrass in the southern portions of the bay. The grasses, which are relatively fast growing, did not grow back in 2006, according to the survey.
However, Larry Simns, president of the Maryland Waterman’s Association, is not very worried about the crab population. “We worry about the overall health of the bay,” said Simns. “We are not too worried about the crab population because it is pretty healthy right now, although this could affect future populations.”