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Net survey: For quarter century, scientists have been counting creatures traveling Chesapeake Bay tributary

For fish, crabs and other creatures living in the Chesapeake Bay, the many creeks, rivers or subestuaries that feed the Chesapeake are enticing avenues to explore for food and refuge. These tributaries also provide important nursery and spawning habitat for many of the Bay’s aquatic residents. More than 25 years ago, researchers at the Smithsonian Environmental Research Center’s Fish and Invertebrate Ecology Lab began taking weekley surveys of the species that make their way in and out of Muddy Creek. This waterway flows through the center’s grounds in Edgewater, Md., and feeds into the Rhode River, which then feeds into the Chesapeake Bay.

View Muddy Creek and the Rhode River in a larger map

To survey the animals swimming up and down Muddy Creek, researchers use a fish weir—an expanse of nets, gates and boardwalks—that temporarily blocks aquatic traffic. Once a week, the researchers close the weir, set out the nets and identify and count all the species that get trapped. They began collecting data in 1983.

This type of fine-scale surveying, done on a weekly basis, is rare. It’s even more unique to have such long-term data. Many ecological studies are funded for just a few years at a time. These short time frames make it difficult for scientists to observe changes and patterns in species populations and composition.

In honor of the 2010 U.S. Census, staff at the Smithsonian Environmental Research Center have created this slide show of a recent spring survey. The salinity on this April day was fairly low and nearly a dozen golden shiners (a freshwater minnow) were caught along with several estuarine-resident and a few diadromous (fish that migrate between fresh and saltwater) species. Among the highlights: a sizeable snapping turtle, many white perch in spawning condition, juvenile American eels and a parasite.

Human activity and environmental conditions can affect which species are swimming in Muddy Creek. The water is brackish and salinity levels change seasonally and from year to year. During winter and early spring, when freshwater flow is usually the highest, researchers will generally catch more freshwater species like bluespotted and banded sunfish–-two protected species in Maryland. During periods of high salinity, researchers can catch many species indicative of the higher saline lower Bay such as red drum, spotted sea trout and Spanish mackerel. –Tina Tennessen


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