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December 22, 2014
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Hidden Treasures of the Delaware

Mussels contribute to water quality and clarity through their filtering capacity. Clear water in the righthand tank containing mussels after less than an hour as compared to the original turbid water in the lefthand tank.
Photo by Jacob Rash, Virginia Tech


North America was once home to 297 species of freshwater mussels, by far the highest diversity in the world. Today, they’re the most rapidly declining animal group in the U.S., over 70% of which are either extinct, endangered, threatened, or potentially justifying federal protection. The majority of the Delaware River’s species (9 of 12 species) fall into the categories of critically imperiled/endangered (dwarf wedgemussel brook floater mussel); imperiled/threatened (eastern pearlshell, alewife floater, triangle floater, yellow lampmussel, and eastern lampmussel); or vulnerable/species of concern (eastern floater, squawfoot or creeper mussel) on either the state or federal levels, due to population declines range wide. Some species once found throughout the Delaware now only survive in certain sections. Only one species in the system (eastern elliptio) has consensus as being secure, though their numbers decline dramatically below some problematic tributaries in which water quality is known to be impaired.

There aren’t many rivers left like the Delaware. As the last major river on the Atlantic Coast undammed the entire length of its main stem (330 miles), it provides unparalleled access to the full range of habitats for nearly all migratory fish species of this seaboard, and retains ecological integrity that is exceptional among the large river systems of the mid-Atlantic and Northeastern United States. It functions still as other rivers did prior to dams, with a pulse of life (in the form of sea-run migratory fish) that ascends its waters and nourishes its inhabitants, timed perfectly to provide for wildlife such as hungry bald eagles feeding their growing young. An accompanying downstream pulse later in the season benefits an array of marine species, balancing an age-old cycle of biomass interchange and completing an important ecological link.