Silver Lamprey
Ichthyomyzon unicuspis
What are Lampreys?
Lampreys are a true ancient wonder of the natural world that live right here in Ontario. Often mistaken for snakes or eels, lampreys are in fact a family of fish that evolved over 300 million years ago and actually pre-date dinosaurs in the fossil record.
Considered one of the most ancient vertebrates alive today, they have a cartilaginous skeleton that supports their long, slender body. Like other fishes, they have gills, but they appear as pore-like openings. They also lack jaws, scales, pectoral, and pelvic fins. Adult lampreys are characterized by a circular sucking mouth with rows of teeth and a toothed tongue – the shape and arrangement of their teeth is a helpful identifying feature of the different species. Three of the five lamprey species found in Ontario are parasitic, using their mouth to attach to fish, rasping through the skin to feed on blood and other bodily fluids. The parasitic nature of this behaviour is reflected in the scientific name of the lamprey genus Ichthyomyzon: Ichthys = fish and myzo = to suck.
Species Description
The Silver Lamprey adults are brown or blue-grey with a lighter belly and have an elongated body that can grow up to 9 to 39cm in length. Adults have a large, round jawless mouth, sharp teeth, and a dorsal fin with two lobes joined by a wide membrane.
Lifecycle
Adult lampreys migrate upstream from the cooler waters of lakes to spawn, often returning to their natal river. Lamprey excavate shallow nests in gravelly riffles by carrying stones in their mouth. Once spawning concludes, the adults die and the eggs hatch into worm-like larvae, known as ammocoetes, that burrow into the substrate where they reside for 4 to 7 years. Ammocoetes do not have eyes or teeth, they are filter-feeders.
After undergoing metamorphosis into their adult form, the lamprey move into larger waterbodies to start their parasitic life stage during which they attach to different host fish to feed. This phase lasts for 1 to 2 years while they sexually mature.
Ammocoetes: (pronounced “ammo-seets”) the larval life stage of lamprey. The larvae burrow into the substrate, lack teeth, are not parasitic, filter feeders that have rudimentary eyes.
In Greek, this name is descriptive and translates to: ammos = sand and koites = dwelling.
Metamorphosis: the process of transformation from an immature form to a mature (adult) form.
Distribution in the Sydenham
Silver Lamprey are found in freshwaters of eastern North America. In Canada, they have been recorded in Ontario, Quebec, and Manitoba.
There is limited information available on the abundance of Silver Lamprey as there has been little sampling effort targeted at this species. Although, there is believed to be a relatively abundant population in Lake St. Clair. Biologists and anglers report encountering a high number of lamprey scars or Silver Lamprey attachments to Lake Sturgeon and Muskellunge in Lake St. Clair.
Between 1989 and 2007, lamprey larvae from the genus Ichthyomyzon were detected in the Sydenham River. The St. Clair Region Conservation Authority has 10 records of Silver Lamprey from in their fish database since 1979, most recently from 2016.
Threats to the Silver Lamprey
Many threats have caused the listing of this living fossil as a species at risk, particularly, habitat loss, in-stream barriers to migration like dams, sedimentation, chemical pollution from herbicides, competition with the invasive Sea Lamprey as well as lampricides used to control Sea Lamprey populations.