Reproduction
Adult Silver Lampreys spawn when they reach 6-8 years of age(COSEWIC). Silver Lamprey spawn in the months of May and June, when water temperatures reach 50°F. Adult Silver Lamprey spawn by traveling up river were they can build nests and lay their eggs. Nests are build in parts of rivers that are riffled and contain sand or gravel bottoms(Ichthyomyzon unicuspis). Adult Silver Lampreys uses their mouths to move sand and gravel to build a nest(The Native Silver Lamprey). Silver Lamprey mate by the female attach herself to a rock while the male attaches himself to the females head. This allows the male to wrap his tail around the females body to bring their genital openings close together. For fertilization to take place the male and female vibrate to release the egg and sperm(Ichthyomyzon unicuspis). Female Silver Lamprey usually produce 10,800 eggs that are about 1mm in diameter(Ichthyomyzon unicuspis). After mating the adult Silver Lamprey die and the fertilized eggs hatch about two weeks after fertilization(COSEWIC).
Silver Lamprey go through indirect development which means that when they are born they are not in their adult form. They must go through a metamorphosis to go from there juvenile form to their adult form. After hatching Silver Lamprey's are in a larvae form and are called ammocetes(Ichthyomyzon unicuspis). After hatching ammocetes are blind and and toothless(Ichthyomyzon unicuspis). Ammocetes tend to drift to calmer water in the rivers that they are born in where they live in the soft muck and ooze at the bottom of the river. Unlike the adult form of Silver Lamprey's, the ammocetes are non-parasitic and filter feed on algae, drifting plankton and detritus(Smith 1985). Silver Lamprey stay as ammocetes for 4 to 7 years before going through a metamorphosis in late summer to fall. During the metamorphosis ammocetes form eyes and develop teeth so that they can enter into their parasitic form(COSEWIC). They remain in the river for the winter and in spring move to larger bodies of water to find larger host fish (Smith 1985). For more on fish that Silver Lamprey feed on check Nutrition.
The adult Silver Lamprey remain in large bodies of water living of host fish for 1 to 2 years before reaching sexual maturity. During sexual maturity the Silver Lamprey stops feeding and the male gonads reach maturity(COSEWIC). In the spring the lampreys migrate up rivers to build nests and mate. After mating the Silver Lampreys die(Smith 1985).
Small adult Silver Lamprey