Eastern Pondmussel

(Ligumia nasuta)

Status: Special Concern (COSEWIC & ESA 2017)

Table of Contents:

Species Identification
Diet
Habitat and Range
Biology and Behaviour
Threats/Reasons for Being at Risk
Conservation and Recovery Strategies
How You Can Help

Photo by Robert Agulilar: https://flic.kr/p/21L9zud

Species Identification:

The Eastern Pondmussel is a medium-to-large sized freshwater mussel that can grow up to 10 cm long. Adults have dark brown or black shells, while juveniles have yellow-green shells. Their shell is rough with growth lines that look like the growth rings on a tree stump.

Diet:

Mussel larvae need to attach to a host fish in order to consume nutrients off their body until they are able to grow into juvenile mussels and drop off the fish host. It is not known which species of fish act as hosts. Once they are either juveniles or adults, their diet includes different types of bacteria and algae that is filtered from the water.

Juvenile Eastern Pondmussels

Map taken from Government of Canada: https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/eastern-pondmussel-2017.html#_01

Habitat and Range:

The Eastern Pondmussel is only found in Eastern North America, down from the lower Great Lakes through New York and New Hampshire, south to North Carolina. In Canada, there are only two known populations, both of which are in Ontario. They used to be one of the most common mussel species in the lower Great Lakes, but now they are only found in the delta area of Lake St. Clair and Lyn Creek, which is a small body of water in the upper St. Lawrence River. Eastern Pondmussel used to be listed as Endangered in Canada, but they were re-designated as Special Concern since both populations contain healthy numbers. New subpopulations have also been found scattered along the Great Lakes, which indicates this species is slowly recovering.

Eastern Pondmussels prefer sediment that has clay, silt, organics, sand, or gravel. They are typically found in sheltered areas of lakes or in slow-moving areas of rivers and canals.

Biology and Behaviour:

Like all mussels, the Eastern Pondmussel lives a sedentary lifestyle by burying themselves into the bottom of lakes or rivers. During mating season, males will release sperm into the water where downstream females will filter the sperm out of the water much like they do for food. Once formed into larvae, females must then find a suitable host fish to attach their young to. To attract fish for its larvae to attach to, the female Eastern Pondmussel produces a lure that looks like the wriggling legs of a swimming shrimp, called a glochidium. When a fish bites the lure, the female ejects her larvae, which have a better chance of attaching at such a close distance. Since Eastern Pondmussels only move up to a couple metres in their lifetime, dispersal of this species occurs in the larval stage, since they travel with their host fish until dropping off at the juvenile stage. Predators of the Eastern Pondmussel include muskrats, otters, raccoons, geese, ducks, fish, and humans.

Threats/ Reasons for being at Risk:

1. Invasive species: Zebra Mussels have decimated populations of freshwater mussels in the Lower Great Lakes by virtually eliminating historical habitat. Over 90% of historical records for the Eastern Pondmussel are from areas now infested with Zebra Mussel and are now inhabitable. The Zebra Mussel has been shown to directly reduce available food sources in the water column due to its siphoning ability. Zebra Mussels will directly attach to a mussel and prevent them from feeding and reproducing by covering their siphons. The weight of a Zebra Mussel will also deform the Eastern Pondmussel.

2. Turbidity, sediment and nutrient loading: High silt inputs can suffocate mussels by clogging gill structures and may also distrust reproductive functions by decreasing the likelihood of encountering a suitable host fish. Increased agricultural pressure has affected water quality resulting in increased turbidity and sediment loads. Nutrient loadings for freshwater mussels relate to eutrophication effects (algal blooms) that can result in oxygen depletion and algal toxins.

3. Contaminants and toxic substances: Mussels are sensitive to increased levels of sediment contamination and water pollution. They are primarily filter feeders, while juveniles remain buried in the sediment feeding on particles associated with the sediment. In both cases, filter feeding increases exposure to water and sediment-born contaminants like road salt, wastewater contaminants, arsenic and copper, mercury, and pesticides and fertilizers from farms.

4. Habitat loss and degradation: Destruction of habitat occurs through dredging, ditching and other forms of channelization. Modifications can result in the direct destruction of mussel habitat and lead to siltation and sand accumulation of local and downstream mussel beds. Damming of the stream channel has been shown to detrimentally affect mussels as reservoirs alter downstream flow patterns and distrust the natural thermal profiles of the watercourse which potentially separates mussels from their host fish.

Conservation and recovery strategies:

Since the Eastern Pondmussel is a species listed as Special Concern, there are no direct conservation and recovery efforts. The best strategy for the further recovery of this species is to control the spread of invasive Zebra Mussel populations, reduce or eliminate dredging in areas with known populations, and reduce the amount of environmental contaminants that leach into our waterways.

How can you help?

Stop the spread of invasive Zebra Mussels by keeping your boating and fishing equipment clean when travelling between water bodies.
Help improve mussel habitat and keep Ontario’s water safe and clean by maintaining natural vegetation next to creeks and rivers on your property- the roots of plants reduce erosion and can stop from washing into the river.
Farmers with lakes or rivers that border their fields should fence off shoreline areas to keep cattle (and their manure) out of the water.
Avoid using harmful chemicals on your property.