The average length of a Rainbow Mussel is 8 cm. They have a laterally-compressed, elongate-elliptical shape, and they are yellow, yellow-green, or brown in colour. The inside of their shell is iridescent which gives them a rainbow colour. The shell surface is covered with numerous narrow and wide broken dark green lines. While males and females look very similar, male shells are more bluntly pointed and females are more broadly rounded. Rainbow Mussels are also the only Mussel species that has a lure that looks like a crayfish. This lure is used by females to attract host fish to attach their young to.
Rainbow Mussels- like all Mussels, are filter feeders which means they eat bacteria and algae by filtering it out of the water. Mussel larvae need to attach to a host fish in order to consume nutrients off their body. This occurs until they are able to grow into juvenile mussels and drop off the fish host.
Biology and Behaviour:
Rainbow Mussels are sedentary, they bury themselves in the bottom of lakes and rivers, only moving up to a couple of metres in their lifetime. 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 young have 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 Rainbow Mussel produces a special lure that looks like a crayfish to attract host fish. The closer the host fish comes to the Mussel, the easier it is for her to attach her young. Host fish are generally Striped Shiner (Luxilus chrysocephalus), Streamline Chub (Erimystax dissimilis), Smallmouth Bass (Micropterus dolomieu), Largemouth Bass (Micropterus salmoides), Green Sunfish (Lepomis cyanellus), Bluebreast Darter (Etheostoma camurum), Greenside Darter (Etheostoma blennioides), Rainbow Darter (Etheostoma caeruleum) and Yellow Perch (Perca flavescens). Rainbow Mussels are preyed upon by river otters, mink, and muskrat.
Conservation and recovery strategies:
Rainbow Mussels are protected under the Ontario Endangered Species Act, Provincial Policy Statement of Planning Act and Aggregate Resources Act, Ontario Lakes and Rivers Improvement Act, and the Federal Fisheries Act (Ontario Fishery Regulations). The Federal Fisheries Act is important for mussel protection, since permits are needed to collect mussels in Ontario which reduces the amount of harvesting that can impact small local populations. OMAFRA also has a Voluntary Land-stewardship Program that works with landowners to reduce erosion, especially for shorelines near agricultural fields.
COSEWIC 2006. COSEWIC assessment and status report on the Rainbow mussel Villosa iris in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 38 pp. https://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_rainbow_mussel_e.pdf
COSEWIC. 2015. COSEWIC assessment and status report on the Rainbow Villosa iris in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xii + 82 pp. https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/rainbow-2015.html
Government of Ontario. 2014. Rainbow. Retrieved from: https://www.ontario.ca/page/rainbow-mussel
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