Freshwater mussels are one of the most rapidly declining animal groups in the country, with 55% of species extinct or imperiled.
It was a blustery winter morning when my brother and I donned our hip waders in search of tidewater muckets. I don’t often go looking for freshwater mussels in January, but sighting reports for muckets are somewhat rare, and I needed to confirm what Ben (a WCC volunteer and mussel enthusiast) had found while retrieving his muskrat traps.
As the name implies, the tidewater mucket (Leptodea ochracea) is often associated with tidewaters. In North America, the species ranges from the Savannah River drainage in Georgia, north to Nova Scotia. In New Jersey, the mussel is reported in the Delaware River from Trenton south to its lower tributaries, including Rancocas, Alloway and Menantico creeks. Until receiving Ben’s text message and photograph of what appeared to be a live mucket, I had never known the species to occur in NJ lakes.
The tidewater mucket is one of our state’s 12 native mussel species. Freshwater mussels are bivalves that inhabit rivers, creeks, lakes, and ponds. They spend much of their lives partially embedded in the substrate, filtering food (mostly plankton and bacteria) out of the water column. The water is pumped into the mussel by a siphon. As cilia move food towards the mouth, pollutants are also strained out, thus improving water quality and earning mussels the nickname “nature’s vacuum cleaners.” Because of their sensitivity to contaminants, they are excellent water quality indicators. Mussels also provide food for muskrats, raccoons, and other wildlife.
The water is higher and more turbid than we expected due to steady wind and previous day’s rain. Ben points out places near the sandy shore where he had discovered mucket shells. It isn’t long before our work pays off; after retrieving a dozen shells of a common species (Eastern floater) from the frigid water, we locate five of the heavier, more ovate shells of the tidewater mucket.
The tidewater mucket can be found in sand/silt and small gravel substrates. It has a yellowish to greenish-brown shell that usually doesn’t exceed three inches. The nacre, or inner mother-of-pearl shell layer, is iridescent pink or salmon-colored. The species can be confused with the yellow lampmussel, another Delaware River resident.
Because of their sensitivity to contaminants, they are excellent water quality indicators.
I am encouraged that Ben has found small shells, a sign that reproduction is occurring. Tidewater muckets spawn in late summer and release their larvae the following spring. Like most freshwater mussels, muckets require a host fish to complete their life cycle. The larvae, known as glochidia, are ejected from the female mussel’s excurrent siphon after developing from eggs held in the gills. Glochidia are microscopic and free-floating, and must attach to a particular fish species to survive. After several weeks of consuming vital nutrients, the newly transformed juvenile mussel drops off the fish. With any luck, this occurs over suitable habitat. The mussel burrows into the sediment, spending its first year of life hidden below the substrate. Although the mucket’s host fish is NJ is unknown, it is thought to be anadromous, migrating from the sea up rivers during certain times of the year.
Freshwater mussels are one of the most rapidly declining animal groups in the country, with 55% of species extinct or imperiled. Mussels are threatened by water quality and habitat degradation, dams (which can block host fish passage), and expansion of exotic mollusks. Since freshwater mussels are among the longest-lived animal groups on Earth (some species can live 100+ years!), declines are often overlooked. A population can be functionally extinct, with individuals surviving without reproducing. In NJ, nine species are listed as Endangered, Threatened or Special Concern. The tidewater mucket’s status is threatened.
On our next visit, the water temperature had dropped, and I suspect the muckets have buried under the substrate. We search for live individuals, and although Ben finds a filtering floater, muckets are nowhere to be seen. We walk to where he had spotted a large, live mucket days earlier. My fingers and toes are numb, and I make a mental note to buy a cheap pair of insulated hip waders. Then we see it, at first just a glint of gold; a fresh shell where the live mucket had been – apparently our mussel had become food for a hungry muskrat. As if on cue, glistening snowflakes cascade over the lake and dust the surrounding vegetation. It is time to go. But I’ll be back in spring, when muckets release their glochidia and can be easily spotted on the substrate. The work at this site, now confirmed tidewater mucket habitat, has only just begun.
By Jeanette Bowers-Altman, Principal Zoologist, NJ Endangered & Nongame Species Program
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