Your Land & Water for November 2025
- jhansen49
- 2 days ago
- 4 min read
What's in this issue? A look into an often overlooked but extremely important native animal to our freshwater streams. The humble mussel!
The Freshwater Mussel-A Fascinating Animal
by Suzanne McCarthy
Do you know this animal? You may or may not have eaten mussels but, if you have, those were a marine species, like the clams we eat. Freshwater mussels are also a food source but for birds, otters, raccoons, and other wildlife. They may also have been eaten by native tribes in the past and were likely used by them for ornamentation and tools. But they differ from marine varieties in their habitat and life cycle, as well as their more limited abundance.
WHAT IS A MUSSEL?
Freshwater mussels are bivalves, like clams and oysters, having two halves to their hard shell with a soft body inside. They lack a head, eyes, ears, and limbs except for a single foot that they use to move and to burrow down into the mud or sandy bottom of the water body in which they live. They are filter feeders and use their gills to extract oxygen and microparticles from the water around them. An adult mussel can filter as much as 10 gallons of water per day.
You may never have seen a freshwater mussel because they live out of sight on the bottom of ponds and streams. However, there are almost 300 species found in North America, second only to Asia in variety. Twelve of those species live in New Jersey.
Because they filter the water in order to obtain food, mussels are excellent at removing impurities, including pollutants. They can sequester these substances, including heavy metals, along with excess carbon and nitrogen. This function makes them a valuable ecosystem player in the aquatic environment. However, they can be overwhelmed by pollutants, to which they have a low tolerance, and by changes in stream flow, temperature, and siltation.
AN UNUSUAL LIFE CYCLE
The freshwater mussel life cycle has evolved to maintain populations in river and still-water habitats. It does not depend on the larvae to drift and settle in new habitats like other bivalve mollusks. Instead, larval mussels depend on fish to find new habitats – they actually hitchhike on fish!
Male mussels release sperm into the water which is taken in by females nearby or downstream and the fertilized eggs develop inside the female’s brooding pouch. The larvae, when mature, (called glochidia) are then released into the water. They must find and attach to a particular species of fish (to head, fins, or gills, depending on the species) as a way to travel to other sites and to finish their development. They have only a few hours or days to do so or they will die. When they have fully developed, they release from the fish and drop to the substrate, usually without any harm to the fish. Once there, mussels can live for a very long time – 10, 20, or for some species, as much as 60 – 100 years.
THREATS TO MUSSELS
Freshwater mussels are one of the most rapidly declining animal groups in North America, with 55% of species recognized as extinct or imperiled. 44 species are listed as federally endangered, and 60 species are “threatened.” Of New Jersey’s 12 species, 9 are listed as either endangered, threatened, or of special concern. The causes of this decline are many, including degradation of their habitat, reductions in water quality or actual toxic spills, channelization of streams, loss of streambank trees, salt inflow from roads, construction of dams that limit fish movements, and expansion of competing exotics such as the zebra mussel and Asian clam.
STATE CONSERVATION STATUS OF FRESHWATER MUSSEL SPECIES [from delawareestuary/pdf/Restoration/Volunteer%20Guidebook.pdf]
CONSERVATION OF MUSSELS
There are numerous projects to maintain and expand existing mussel populations and to restore mussels where aquatic conditions have improved. In our area, the leading organization for this work is the Partnership for the Delaware Estuary (PDE), which works in collaboration with the NJ, PA, and DE Departments of Environmental Conservation/Protection. Populations of mature larvae are kept in baskets and other devices in local ponds, to enable their continued growth and subsequent restoration to streams. A hatchery to develop more larvae for the studies and restorations is planned, to be located at Bartram’s Gardens in Philadelphia on the Schuylkill River. All this work is part of PDE’s Mussels for Clean Water Initiative. See https://delawareestuary.org/science-and-research/mussels-clean-water-initiative
In New Jersey, young mussels are being raised by PDE at Tall Pines, the state park in Gloucester County, which is land that the South Jersey Land & Water Trust (SJLWT) worked very hard to preserve some years ago. Tall Pines has an active support group – the Friends of Tall Pines – which is made up of people who enjoy and want to protect and enhance Tall Pines and who organize many fun and valuable events at the park. See https://friendsoftallpinespreserve.org/. The mussels being “stored” at Tall Pines are the Eastern pondmussel (Sagittunio nasutas). If you want to learn how to identify freshwater mussels or help with any volunteer efforts going on, see PDE’s Identification Guide and Volunteer Survey Guidebook (https://s3.amazonaws.com/delawareestuary/pdf/Restoration/Volunteer%20Guidebook.pdf).
There are many other interesting facts about mussels, as there are also about the many little-known lowly creatures that inhabit our region. Who knew how surprising and beneficial they could be, until we began looking closely!
SOURCES
About Freshwater mussels. Xerces Society for Invertebrate Conservation. https://xerces.org/endangered-species/freshwater-mussels/about
Freshwater Mussels. NJ DEP - Fish & Wildlife. https://dep.nj.gov/njfw/wildlife/freshwater-mussels
Gentry M. J., Cheng, K. M., and Kreeger, D. A., 2024 Improving the Water Quality of Delaware Ponds by Stocking Freshwater Mussels that Filter Nutrient-Laden Particles. Partnership for the Delaware Estuary, Wilmington, DE. PDE Report No. 24-02.
Identification Guide and Volunteer Survey Guidebook. Partnership for The Delaware Estuary. https://s3.amazonaws.com/delawareestuary/pdf/Restoration/Volunteer%20Guidebook.pdf
Mussel. Wikipedia, The Free Encyclopedia. Sept. 2025. https://en.wikipedia.org/wiki/Mussel
Mussels for Clean Water Initiative Fact Sheet. Partnership for The Delaware Estuary. https://delawareestuary.org/science-and-research/mussels-clean-water-inititive.