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December 09, 2016
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Hidden Treasures of the Delaware

This beautiful green-rayed specimen of an eastern elliptio mussel exhibits a color variation found in some juveniles from the Delaware and Neversink Rivers. Eastern elliptios make up the greatest animal biomass in the Delaware, and are the only mussel species here with consensus on their conservation status being “Secure.”
Photo by Erik Silldorff, DRBC

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.