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Maryland's Stream Life

Maryland has more than 16,000 miles of freshwater streams—an extensive system of waterways flowing downstream where (depending on their geography) they ultimately contribute freshwater to the Chesapeake Bay, the Atlantic Coastal Bays, the Ohio River, or the Delaware River. The condition of these streams is vitally important to downstream waters, but these streams also possess significant inherent value.

The diversity of stream habitats throughout Maryland—from the cold mountain streams of Western Maryland to the slow, dark swamps of the Eastern Shore—supports an amazing faunal diversity. This includes nearly 100 fish species, 16 native freshwater mussels, nine native crayfishes, eight stream salamanders, and hundreds of different aquatic insects and other benthic macroinvertebrates.

Maryland Biological Stream Survey

The Maryland Department of Natural Resources Maryland Biological Stream Survey (MBSS) was initiated in 1995 to provide the information necessary to evaluate the health of Maryland’s streams, to report on the diversity of life and habitats within them, and to inform stream ecological restoration and protection. The core of the MBSS consists of a statistical design that uses randomly selected stream locations throughout Maryland to provide a representative sample of overall stream health and biological diversity. In addition, a network of relatively intact “Sentinel Sites” provides a reference for comparing other streams and tracking variability in instream conditions due to factors such as climate and weather. Sampling also takes place at specific locations to evaluate specific management actions.

At each site, the MBSS collects data about fish, aquatic insects, and other macroinvertebrates, freshwater mussels, crayfish, amphibians, reptiles, and associated physical, chemical, and landscape information. The MBSS uses benthic macroinvertebrate and fish indices of biological integrity, specifically developed for Maryland streams with standard scientific methods, to assess stream ecological condition (often referred to as stream health).