Photo Essay: The blue crab winter dredge survey completes its course
A two-state effort finds out how many blue crabs live in the Chesapeake Bay
By Will Parson |
From December to March, assessing the health of the Chesapeake Bay’s blue crab population means long stints on the water for scientists from the Virginia Institute of Marine Science (VIMS). Every year the blue crab winter dredge survey samples 1,500 randomly-chosen sites divided equally between Virginia and Maryland waters, in a partnership between VIMS and the Fisheries Service of the Maryland Department of Natural Resources (DNR). The data provides a bay-wide estimate of blue crab populations that helps agencies determine how many can be harvested without hampering the recovery of one of the Chesapeake Bay’s defining resources.
After a clear, calm sunrise in the second week of March, the VIMS team left their headquarters in Gloucester Point, Virginia, with 742 of 750 sites under their belt. Their boat, the R/V Bay Eagle, is their home during trips lasting up to four days at a time. With just eight sites left to sample using their six-foot-wide crab dredge, this would be a relatively short day—the last one of the season.
“That sort of puts a smile on our face,” said Mike Seebo, a VIMS marine scientist who has worked on the winter dredge survey since its second winter in 1990.
Marine Scientist Gabrielle Saluta, right, and Research Specialist Alison Smith pull blue crabs from the dredge near the mouth of the York River in Virginia.
The dredge relies on the blue crab’s winter behavior of burrowing into the mud and lying dormant when the temperature drops below 45 to 50 degrees Fahrenheit. When the crabs wake up in the coming months, the mature females will migrate to lower-salinity spawning grounds in the Bay’s tributaries, a journey of up to 150 miles for crabs reaching the northernmost habitats.
And many of the crabs will end up harvested, steamed and covered in Old Bay seasoning. For one of the region’s mainstays, the numbers coming from the survey teams will be highly awaited.
See how the process unfolds in our video from the Maryland half of the winter dredge survey.
Seebo records numbers of blue crab as well as bycatch, location and water quality data.
Marine Scientist Katie Knick pushes a crab dredge into position while the team hauls up a dredge sample.
Saluta, left, examines a peppermint shrimp held by Seebo. Dredge bycatch can include small fish, plants and invertebrates like hydroids, tunicates and clams.
Saluta, top, and Smith tie tags to blue crabs for an ongoing program that yields information on blue crab mortality, longevity and migrations. Anyone who catches a tagged crab can earn a $20 reward by calling in and then filling out a data sheet mailed to them.
Saluta returns tagged blue crabs to the lower stretch of the Chesapeake Bay.
From left, Smith, Saluta and Knick wait as a dredge is performed. At every site the six-foot-wide dredge travels at three knots for 60 seconds, and the team records GPS data to measures the distance traveled.
Sluggish from the cold, a male blue crab rests on the deck of the R/V Bay Eagle after being pulled from the mud of the Chesapeake Bay. The winter dredge survey operates as blue crabs remain dormant in the mud, before water temperatures rise.
Seebo collects a blue crab caught at a sample site.
From left, Knick makes a sandwich while taking a lunch break with Smith and Saluta aboard the R/V Bay Eagle. "One thing to look forward to is food—so we try to eat well," Seebo said.
Seebo hoses off the deck of the R/V Bay Eagle after the completion of sampling on the last day of the blue crab winter dredge survey. “It’s sort of bittersweet—as soon as [the weather] starts getting pleasant and nice we stop,” Seebo said.
Keith Mayer of VIMS unloads gear from the R/V Bay Eagle at the end of the last day of the blue crab winter dredge survey in Gloucester Point, Va., on March 8, 2016.
To view more photos, visit the Chesapeake Bay Program’s Flickr page