The Silver Lamprey is a long, eel-shaped fish that is relatively small in size. Adult Silver Lamprey only grow to about 9-39 cm long. Like all lamprey species, the Silver Lamprey does not have a jaw or typical mouth. Instead, they have a large disc-like mouth with rows of teeth capable of sucking and latching onto host fish. Adults are dark brown or grey with silver/blue bellies, while juveniles are yellow or tan-grey. It is very hard to distinguish between lamprey species, experts must use fin and teeth arrangements in order to correctly identify them.
Lampreys are parasitic species that latch onto host fish and feed off their flesh and bodily fluids. There have been up to 23 documented host species for the Silver Lamprey to feed on, which includes Sturgeon, Trout, Carp, Muskie, Pike, Bass, Walleye, and Perch. They prefer to feed on blood rather than flesh, and they are more attracted to larger fish species. For the most part, Silver Lampreys are non-lethal feeders. They will latch onto a fish until and slowly feed from them until they have had their fill, and then they will release them with minimal injuries. However, growing Silver Lamprey have been reported to have more host mortalities than fully grown adults.
Biology and Behaviour:
Silver Lamprey only spawn once during their lifetime. Once they reach sexual maturity around 6 years of age, they will head to their spawning grounds to breed before dying. During the spring when water temperatures get above 10°C, sexually mature Silver Lamprey will head to their spawning grounds up large rivers. They will actually use the scent of bile acids that are excreted by larval lamprey in order to choose which spawning grounds they would like to travel to. Once they arrive, Silver Lamprey couples will build a nest out of stones and dig a depression in the sand or gravel about 8 cm deep. The male will attach himself to the head of the female to remain in place to fertilize the eggs as she lays them. Silver Lamprey will also communally spawn in one nest- researchers have found up to 10 pairs in just one area! Females will lay anywhere between 12,000 and 30,000 eggs, which hatch in 2-3 weeks.
Once larvae emerge from the eggs, they will travel downstream and burrow into the sand or gravel and create U-shaped burrows to live in for 4-7 years. The larvae will consume nearby algae, pollen, bacteria, and small invertebrates. After several years in their burrows, the larvae will morph into adult lampreys throughout the winter, and emerge in the spring to head to lakes or larger rivers to begin their parasitic phase. They use their suction cup-like mouths to latch onto various host fish for 12-20 months until they are ready to spawn and eventually die.
Various fish species will feed on the eggs and larvae of the Silver Lamprey, and Walleye, Brown Trout, and Northern Pike are known predators of the adult Silver Lamprey. During spawning season in the shallow water, adult lamprey can also be picked off by small mammals and birds.
Conservation and recovery strategies:
Since the Silver Lamprey is only listed as Special Concern for the Great Lakes - St. Lawrence population, and the Saskatchewan - Nelson River population has not been researched enough, there are no direct protection, conservation, or recovery strategies in place for this species. Initial recovery strategies should be further research on the Silver Lamprey population and habitat in Canada in order to better determine actual numbers and their preferred habitat. Recovery and conservation strategies should also look at minimizing threats, such as reducing habitat changes, creating safe passages around dams and minimizing changes in water flow, removing the use of lampricide in known Silver Lamprey habitats, and reducing agricultural runoff and shoreline development.
COSEWIC. 2011. COSEWIC assessment and status report on the Silver Lamprey, Great Lakes - Upper St. Lawrence populations and Saskatchewan - Nelson Rivers populations Ichthyomyzon unicuspis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii + 55 pp. https://wildlife-species.canada.ca/species-risk-registry/virtual_sara/files/cosewic/sr_silver_lamprey_0911_eng.pdf
Government of Ontario. 2018. Silver Lamprey. Retrieved from: https://www.ontario.ca/page/silver-lamprey
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