Rhode Island’s Freshwater Mussels
By Branton Elleman, Seasonal Researcher, RI Division of Fish & Wildlife — Freshwater Fisheries
Ask a Rhode Islander what they know about mussels and you’re likely to get a recipe containing tomato, chorizo, and wine for our saltwater variety. But further inland, in the rivers, streams, and ponds throughout the state, are a whole assortment of freshwater mussel species. Not nearly as tasty to humans, they none the less serve as a key food source for local wildlife and important part of the underwater ecosystem.
Once the egg is fertilized, a freshwater mussel begins its life as a mere speck, being cast into the water column to drift in a larval form called glochidia. If these larvae come into contact with a suitable fish host, such as a salmonid, they attach themselves to gills or fins and ride along as an essentially harmless parasite. Once they reach a certain size, the now miniature-mussel will release itself from the fish and settle into the substrate to grow further. The conditions that a young mussel can tolerate depend on the species. Some need to find themselves in pristine flowing waters with loose sand or gravel to survive, while others can survive in still water with a silty bottom.
Each species has subtle differences in morphology, including shape, color, patterning, and thickness. Their shells are generally dark, but older specimens often show heavy abrasion on the buried side that reveals lighter shades of brown or even white. A mussel has a left and right valve (the term for the shell halves), connected by a hinge and flanked by its “beak,” or umbo. Often the hinge is aided by two types of “teeth.” These teeth help align the valves together when closed. Lateral teeth appear as long ridges parallel to the hinge and pseudocardinal teeth resemble little knuckles near the beak. Both usually come in odd-even arrangements that nest together when closed. But their exact number, placement, or even absence is a vital clue to determining the species of mussel. Therefore, outward appearance may not be enough to make a positive identification.
Once mature, a mussel may move about to find a more favorable spot. We have seen mussels crawl along the streambed during surveys, pushing and pulling themselves along with the help of a muscular foot they can slip out of their shell. You’d never call them fast, but at roughly a snail’s pace they’ll leave enough of a trail in the sand to notice. After settling on a location, either isolated or in large colonies, most mussels tend to burrow into the bottom and orient themselves vertically. They will then crack open their valves and expose their gills to the flowing water to filter feed.
Here they demonstrate perhaps their most valuable ecological service: filtration. As a mussel pulls water through its gills and internal organs, it absorbs nutrients to feed off of. Many pollutants or harmful organisms will also be filtered out from the water, either being stored in the mussel body tissue or expelled out in a harmless state. This feeding trait means freshwater mussels serve as an important indicator species. Their presence, or absence, can be a valuable clue as to the local water quality. Certain RI species, such as the Eastern Pearlshell, are especially sensitive to water quality and have seen significant decline as their cold water habitats degrade. This species among others, are listed as a species of greatest conservation need (SGCN) in Rhode Island. This classification further highlights their importance to watersheds and a need for targeted recovery efforts.
Rhode Island has eight (8) total documented species, but populations have seen a decline throughout the 20th century. Historically rich and diverse populations have dwindled due to the combined effects of pollution, habitat degradation, invasive species, and host species decline (such as river herring and trout). To better assess current population health and diversity, the Rhode Island Division of Fish and Wildlife has begun conducting mussel surveys. A small team of 2-3 researchers will wade sections of rivers and streams, visually searching the bottom for mussels with viewing boxes (called bathyscopes). When mussels are encountered, they are identified by species, measured for length and counted. With this data, biologists can track populations and species distribution in order to monitor for population decline and identify potential restoration opportunities.
So the next time you’re wading or swimming in one of the state’s rivers or ponds, keep an eye out for freshwater mussels. You may find a lone mollusk hidden amongst the rocks or come across beds thick enough to coat entire sections of the bottom. Try to tread lightly to protect living mussel colonies but feel free to examine empty shells left behind by predators. The Connecticut DEEP website even has a handy guide to freshwater mussels that conveniently includes all of our species.
Children Only Ponds
Children Only (14 years of age and younger):
- Frosty Hollow Pond - Exeter
- Lapham Pond - Burrillville
- *Scott Evans Memorial Pond
(Biscuit City) - S. Kingstown
- Seidel’s Pond - Cranston
- Silvy’s Pond - Cumberland
Children only ponds for the first two days of the trout
season (April 10th & 11th):
- Cass Pond - Woonsocket
- Ponderosa Park Pond - Little Compton
- Slater Park Pond - Pawtucket
Children Only Pond from April 10th through Memorial Day, May 31st:
- Lloyd Kenney Pond - Hopkinton*Wheelchair accessible.
Fishing Activities Requiring a Permit
Permits are required for organized fishing tournaments for state fishing and boating access areas and for the following private access areas: Johnson’s Pond (Flat River Reservoir) in Coventry, and Waterman Reservoir, Glocester. Permits are required for six (6) or more persons and/or three (3) or more boats. Applications for the issuance of a permit must be submitted to the Division a minimum of three (3) weeks prior to the tournament. An organization may cancel a permitted fishing activity without penalty as long as written notice of cancellation is received at least three (3) weeks prior to the event. Failure to provide timely written notice shall result in a one (1) year revocation of an organization’s eligibility to receive a permit for any organized fishing activity. Exceptions for unforeseen occurrences (e.g. weather, natural disaster) will apply at the discretion of the Division. The decision of revocation shall rest entirely with the Division. Permit applications may be obtained by contacting RIDEM Division of Fish and Wildlife, 277 Great Neck Road, West Kingston, RI 02892, Tel: (401) 789-7481. Applicants must complete all required information. The Division reserves the right to limit the number of activities per location, per day, time period, or deny a permit for reasons of overuse or conflict with other activities.
The applicant must indicate on the application whether the fishing activity is a ‘closed’ or an ‘open’ activity. A closed fishing activity is an event having a fixed or restricted number of participants. An open fishing activity is an event having an unrestricted number of participants.
If the tournament is closed, the number of boats, vehicles, and participants must be entered on the application. The permit must be retained on site by the sponsor along with the list of participants and boat registration numbers.
If the tournament is open, the names of all participants and registration numbers of each boat on the day of the tournament must be made available to RIDEM Division of Law Enforcement. An estimated count of all participants, vehicles and boats shall be forwarded to the Division at least five (5) days prior to the start of the tournament.
Regardless if a fishing tournament is ‘closed’ or ‘open’, the organization must provide a report to the Division within five (5) days of the termination of the tournament which includes: the number of hours fished, the number of boats, numbers of participants, and, as applicable, the total number of largemouth bass and smallmouth bass caught as well as the total weight of all largemouth bass and all smallmouth bass processed at weigh-in. This report may be sent as a letter to RIDEM Division of Fish and Wildlife or by completing the Bass Tournament Count Form. Failure to complete and submit the required information within five (5) days shall render the organization ineligible to conduct further organized fishing events for one year from the said event. Such revocation shall include any events for which a permit was previously issued.
Applicants requesting a permit for a municipal or private ramp shall be responsible to obtain additional permits for these areas, if necessary.
These regulations shall not be interpreted as superseding any special boat ramp or state management area regulations.
Permits along with lists of participants and boat registrations, if applicable, shall be available during the tournament for law enforcement purposes and must be clearly displayed in the windshield of the contact’s vehicle.
For more information, contact Alan Libby at email@example.com or 401-789-0281