Ichthyomyzon unicuspisSilver lamprey

Geographic Range

Silver lampreys are found in southern Canada and the northern United States. In Canada, they are found in rivers and lakes of Ontario and Quebec. In the United States, they can be found from Minnesota to Vermont, and as far south as Kentucky. Their range is centered in the Great Lakes and any tributaries or outflows, as well as the Ohio, Mississippi, St. Lawrence, and Hudson Rivers. (Renaud, et al., 2009; Werner, 2004)


Silver lampreys are found in large, clear rivers and lakes. Their habitats often coincide with those of their large host fishes including flathead catfish, northern pike, paddlefish, and lake sturgeon. During spawning in the spring, silver lampreys inhabit clear, medium to large-sized rivers with gravel and sandy substrates. The range of inhabited depths is highly variable. During their parasitic adult stage, silver lampreys live in lakes, however, as ammocoetes they live in rivers and streams. (Becker, 1983; Manion and Hanson, 1980)

  • Aquatic Biomes
  • pelagic
  • lakes and ponds
  • rivers and streams

Physical Description

Silver lampreys have a single, continuous dorsal fin with a shallow notch in the middle. This dorsal fin is connected to a short, round caudal fin. They do not have jaws and instead have an oral disc with sharp, unicuspid teeth. Their skeletons are cartilaginous. The ammocoetes of silver lampreys are indistinguishable from ammocoetes of northern brook lampreys. The ammocoetes are brown to gray-brown on their back, sides, and on a narrow strip at the base of the caudal peduncle. They also have a pale median line along their backs. Most young adults have a tan coloration and are lighter on their stomachs than on their backs, although some individuals have a slate coloration at this stage. Mature adults range from blue to blue-gray on their sides and back, and black, grey, or blue on their bellies. Individuals that reach over 150 mm in total length become slightly darker around their lateral line sense organs and on the underside of the branchial region. Even when this occurs, they still have far less black pigment in those areas than chestnut lampreys. (Becker, 1983; Werner, 2004)

  • Range mass
    1.6 to 104.1 g
    0.06 to 3.67 oz
  • Average mass
    28.4 g
    1.00 oz
  • Range length
    103 to 326 mm
    4.06 to 12.83 in
  • Average length
    211 mm
    8.31 in


Larvae hatch approximately 5 days after the eggs are deposited into the nest. These larvae are referred to as ammocoetes. When the eggs hatch and the ammocoetes leave the nest, they drift downstream and burrow into substrates of sand, muck, and organic debris. Once the ammocoetes have burrowed into the substrate, they can filter feed from the water column. Particles that are filtered and consumed from the water column include algae, diatoms, pollen, and protozoa. Individuals remain in that life stage roughly four to seven years. Metamorphosis occurs at the end of the four to seven year period, during which the ammocoetes are fossorial. Using stored nutrients, and especially lipids, larval lampreys transform into adult lampreys. Hormonal initiation is thought to control the process, but the system has not been adequately studied. (Becker, 1983; Rovainen, 1996)


Parasitic adult lampreys move upstream to spawn. Males initiate nest building and are assisted by a female. Nests must be built in a unidirectional flow of water, with velocities between 0.5 and 1.5 meters per second and at depths of 13 to 170 cm. The water temperature can range from approximately 10 to 26.1°C. Moderately-sized gravel, roughly 3 cm in diameter, can be used for nest construction. The nests are roughly 30 cm in diameter and have a cavity depth of 11 cm. Nest building usually takes one to three days. Once the nest is complete, the male and female spawn. Sea lampreys build their nests in deeper, swifter moving waters. Due to the nest sharing that occurs between these species, silver lampreys will nest in deeper than usual waters when such nests are present. Silver lampreys are also known to take part is mass spawning, in which multiple individuals spawn in one nest. Sometimes individuals spawn in a nest that has already been constructed, often by sea lampreys. Multiple individuals and lamprey species can be found in these nests as sea lampreys tend to build larger nests on average. In Michigan, silver lampreys have been found in nests with sea lampreys and American brook lampreys. In Wisconsin, nest associations of silver lampreys have only been found with sea lampreys. Male silver lampreys are not as competitive as male sea lampreys, which have a mostly monogamous mating system. (Cochran and Lyons, 2004; Cochran, et al., 2008; Manion and Hanson, 1980; Werner, 2004)

As the water temperature increases during spring, adult silver lampreys move upstream in rivers to spawn. Once nest construction is complete, the female attaches her oral disc to one of the rocks in the nest. The male attaches himself to the female's head and arranges his body so that their genital pores are in close proximity. The male and female simultaneously release eggs and sperm, and the non-buoyant eggs sink to the bottom of the nest. (Manion and Hanson, 1980)

  • Breeding interval
    Silver lampreys only spawn once and die shortly after.
  • Breeding season
    Silver lampreys spawn from April to July.

Silver lampreys die shortly after spawning. No parental involvement or care is observed within this species. (Manion and Hanson, 1980)

  • Parental Investment
  • no parental involvement


Their lifespan can range from 5 to 9 years, from ammocoete through metamorphosis to a parasitic adult. Silver lampreys actually spend a majority of their life fossorial as an ammocoete before metamorphosis. After metamorphosis, silver lampreys live about 1 to 2 years in their parasitic form before spawning and dying. (Werner, 2004)

  • Typical lifespan
    Status: wild
    5 to 9 years


Silver lampreys spend roughly three quarters of their lifetime burrowed in riverbeds as filter feeding ammocoetes. The rest of their life is parasitic, in which free-swimming individuals attach to a large host fish to feed on their blood and bodily fluids. Because of these characteristics, especially as ammocoetes before metamorphosis, silver lampreys have few intraspecies interactions other than during reproduction. Likewise, interspecies interactions only occur at times in which silver lampreys are attached to hosts for feeding. One study found a majority of parasitic attacks by individuals occurred at night, suggesting that silver lampreys are more nocturnal than diurnal. This may be due to the decreased risk of predation in the dark as opposed to attachments in daylight. (Cochran, 1986)

Home Range

Individuals of this species do not have a home range. Once silver lampreys are attached to a host fish, they are dispersed to wherever the host fish goes. More specifically, these lampreys have been observed attached to lake sturgeon during their migration and spawning season. This can aid silver lampreys in transportation upstream to their preferred spawning habitat. (Cochran, et al., 2003)

Communication and Perception

Since silver lampreys are solitary and primarily interact with other species while feeding, their senses are developed more for perception and less for communication. Individuals use electroreception while foraging. As predators of other fish, silver lampreys might be able to use low-frequency electric fields produced by prey for prey localization. As these fields are weak, they would be detectable within < 10 centimeters. This suggests that electroreception would be used in the final stages of localizing prey. Chemoreceptors and mechanoreceptors are also utilized by silver lampreys. Chemoreceptors may be highly implicated for the initiation of feeding. In addition to these senses, individuals of this species have very well-developed eyes with an egg-shaped lens. (Bodznick and Preston, 1983; Collin and Fritzsch, 1992; Kawasaki and Rovainen, 1988)

Food Habits

Silver lampreys utilize different feeding strategies as larval ammocoetes versus their parasitic adult phase. As an ammocoete, silver lampreys filter feed from the bottom of rivers, feeding on algae, pollen, diatoms, and protozoa. This style of feeding is facilitated by the unidirectional flow of water through their mouth, which exits through their branchial pores. These particles are captured on the mucous strands in the pharynx, while water free of debris exits the individual. In their parasitic stage, silver lampreys attach themselves with their teeth and oral disc to a large host fish. Their sharp unicupsid teeth can cut through the flesh of their prey. With their sucker-like mouth, individuals feed on fish flesh where attached, but they mainly feed on blood and bodily fluids. The rates of parasitic feeding and growth are highest between June and September. Their host species include lake sturgeon, Atlantic sturgeon, paddlefish, longnose gar, goldfish, common carp, longnose suckers, white suckers, black buffalo, brown bullhead, northern pike, muskellunge, lake whitefish, brook trout, lake trout, white bass, striped bass, rock bass, smallmouth bass, and walleye. (Becker, 1983; Renaud, 2002; Rovainen, 1996)

  • Animal Foods
  • fish
  • blood
  • body fluids


Eggs, ammocoetes, and small adult lampreys are preyed upon by a large variety of piscivorous fish. In one documented case, a gull was observed feeding on a silver lamprey on the Fox River in Wisconsin. Silver lampreys have few strategies adapted to avoiding predators, as they are top predators themselves. These lampreys may be nocturnal to avoid predation. (Becker, 1983; Cochran and Marks, 1995; Cochran, 1986)

Ecosystem Roles

Larval ammocoetes have an important role in nutrient spiraling in rivers. In consuming algae, pollen, diatoms, detritus, and protozoa, ammocoetes are helping to break down coarse particulate organic matter (CPOM) into fine particulate organic matter (FPOM) and dissolved organic matter (DOM). Once processed, the nutrients can be utilized by other organisms downriver from the ammocoete. In their parasitic stage, silver lampreys may play a role in controlling populations of large host fishes. (Dodds and Whiles, 2010)

Species Used as Host

Economic Importance for Humans: Positive

These fish have little economic importance to humans. Ammocoetes and small adults of this species can be used as bait by sport fisherman to catch fish such as black bass and catfish. They are not a marketable fish for consumption. The primary impact of silver lampreys is within the natural aquatic ecosystem. (Becker, 1983)

Economic Importance for Humans: Negative

Lampreys are parasitic on large fish, which are often popular sport and game fish. Even though silver lampreys are parasitic, they do not threaten sport fishing as much as invasive sea lampreys. Silver lampreys are a native species and occur in popular fishing sites. Fishing seems unaffected, even when large numbers of lamprey are present. This suggests that silver lampreys have no negative effects on humans. (Becker, 1983)

Conservation Status

Populations are relatively stable but may be declining in areas populated by sea lampreys. Silver lampreys are listed as endangered in Nebraska and South Dakota, and are rare in West Virginia. One conservation technique may include decreasing populations of sea lampreys with the use of lampricides. Also, barriers such as dams, which block access to spawning sites should be removed or circumvented. (Becker, 1983; Renaud, 1997)


Chelsea Blumbergs (author), University of Michigan-Ann Arbor, Jeff Schaeffer (editor), University of Michigan-Ann Arbor, Lauren Sallan (editor), University of Michigan-Ann Arbor, Leila Siciliano Martina (editor), Animal Diversity Web Staff.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


uses electric signals to communicate

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


mainly lives in water that is not salty.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


Having one mate at a time.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


an animal that mainly eats blood

seasonal breeding

breeding is confined to a particular season


offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


uses sight to communicate


Becker, G. 1983. Fishes of Wisconsin. Madison, WI: University of Wisconsin Press.

Bodznick, D., D. Preston. 1983. Physiological characterization of electroreceptors in the lampreys Ichthyomyzon unicuspis and Petromyzon marinus. Journal of Comparative Physiology, 152: 209-217.

Cochran, P. 1986. The daily timing of lamprey attacks. Environmental Biology of Fishes, 16: 325-329.

Cochran, P., D. Bloom, R. Wagner. 2008. Alternative Reproductive Behaviors in Lampreys and their Significance. Journal of Freshwater Ecology, 23: 437-444.

Cochran, P., J. Lyons. 2004. Field and Laboratory Observations on the Ecology and Behavior of the Silver Lamprey (Ichthyomyzon unicuspis) in Wisconsin. Journal of Freshwater Ecology, 19: 245-253.

Cochran, P., J. Lyons, M. Gehl. 2003. Parasitic attachments by overwintering silver lampreys, Ichthyomyzon unicuspis, and chestnut lampreys, Ichthyomyzon castaneus. Environmental Biology of Fishes, 68: 65-71.

Cochran, P., J. Marks. 1995. Biology of the Silver Lamprey, Ichthyomyzon unicuspis, in Green Bay and the Lower Fox River, with a Comparison to the Sea Lamprey, Petromyzon marinus. Copeia, 1995: 409-421.

Collin, S., B. Fritzsch. 1992. Observations on the shape of the lens in the eye of the silver lamprey, Ichthyomyzon unicuspis. Canadian Journal of Zoology, 71: 34-41.

Dodds, W., M. Whiles. 2010. Freshwater Ecology, Second Edition: Concepts and Environmental Application of Limnology. Burlington, MA: Elsevier.

Kawasaki, R., C. Rovainen. 1988. Feeding Behavior by Parasitic Phase Lampreys, Ichthyomyzon unicuspis. Brain Behavior and Evolution, 32: 317-329.

Manion, P., L. Hanson. 1980. Spawning Behavior and Fecundity of Lampreys from the Upper Three Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences, 37: 1635-1640.

Renaud, C. 1997. Conservation status of Northern Hemisphere lampreys (Petromyzontidae). Journal of Applied Ichthyology, 13: 143-148.

Renaud, C. 2002. The Muskellunge, Esox masquinongy, as a host for the Silver Lamprey, Ichthyomyzon unicuspis, in the Ottawa River, Ontario/Quebec. Canadian Field Naturalist, 116: 433-440.

Renaud, C., M. Docker, N. Mandrak. 2009. Taxonomy, Distribution, and Conservation of Lampreys in Canada. American Fisheries Society Symposium, 72: 1-18.

Rovainen, C. 1996. Feeding and Breathing in Lampreys. Brain, Behavior and Evolution, 48: 297-305.

Werner, R. 2004. Freshwater Fishes of the United States: A Field Guide. Syracuse, NY: Syracuse University Press.