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Couesius plumbeusChub minnow(Also: Moose lake minnow; Plumbeus minnow)

By Annalise Povolo

Geographic Range

Lake chub (Couesius plumbeus) have the widest northern distribution of any North American minnow. They can be found widely throughout Canada. In the north-temperate latitudes of the United States, they inhabit the upper reaches of the Missouri River Basin, the Great Lakes region, and the northern Atlantic slope drainages, with presence in eastern Iowa, northern Nebraska, and north-central Colorado as a glacial relict. (Becker, 1983; Bestegen, et al., 1991; Stasiak, 2006; Wells, 1980)

Habitat

Lake chub prefer cool, shallow waters, however, they can thrive in a wide variety of environments and are found in both streams and lakes of all sizes throughout their range. They more commonly inhabit lakes in the southern portion of their range, and rivers in the northern portion. In lakes, they are often found near shores over sandy bottoms with occasional large-sized boulders. In streams they are more commonly found at river-mouths, at depths of about 1 meter or less. (Becker, 1983)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Lake chub have an elongated body with a nearly round cross section. Their dorsal fin originates over the pelvic fin and the lateral line is complete. Their back and upper sides are lead gray. They are silver to silver-white below the lateral line, with the occasional darkened scales on their sides, giving them a distinct speckled appearance, which is easy to identify in the field. Their snout is bluntly rounded and slightly overhangs their mouth. Their mouth is large, almost reaching the anterior margin of their eyes, with a long prominent barbell in each corner. They also have hooked pharyngeal teeth and short gillrakers. (Becker, 1983; Brown, et al., 1970)

Lake chub exhibit sexual dimorphism. Males generally have larger pectoral fins, which are long and subcircular with a gap between the end of the pectoral fin and the origin of the pelvic fin that is about half the length of the pectoral fin. During breeding, males show a faint rosy color at the corner of the mouth, on the upper lip, and above the lip groove. In addition, the upper angle of opercle extends into the opercular cavity. Likewise, the base of the pelvic fin displays a rosy spot, the side of the body above the paired and anal fins has a 3 to 6 mm wide faint rosy stripe, and there is a distinct black lateral stripe during courtship. Females are generally larger and have short, ovate pectoral fins with a gap of about three-fourths the length of the pectoral fin between the end of the pectoral fin and the origin of the pelvic fin. During breeding, females display a rosy color about the base of the pectoral fin and have a silvery peritoneum. In both sexes, tubercles appear during breeding, with males displaying fine tubercles on the top of the head, opercles, cheeks, edges of scales of the back, scales of the sides to the lateral line, breast, caudal peduncle, and the rays of the pectoral and pelvic fins. Females appear similar; however, the male is less heavily tuberculate, only displaying tubercles on the anterior-most rays of the paired fins. (Becker, 1983; Brown, et al., 1970)

  • Sexual Dimorphism
  • female larger
  • Average length
    127 mm
    5.00 in

Development

Lake chub eggs are demersal and non-adhesive, with a dark golden yolk. They have a narrow perivitelline space that is only visible on one side. These eggs range in diameter from 1.8 to 2.4 mm after fertilization. The larvae have 26 to 28 preanal myomeres and a row of melanophores anteriorly descending across the lateral surface of the breast. Newly hatched larvae range in length from 5.8 to 6.4 mm, and have small pectoral buds, formed functional mouth parts, an inflated posterior gas bladder chamber, formed anterior chamber, ossified first caudal fin rays, formed first dorsal fin rays, anal fin rays, and pelvic fin rays. There is rapid change in larvae body proportions, this growth is rapid until the larvae reaches about 9 mm and the rate of growth lessens. Lake chub generally reach maturation at age three and very few live beyond the age of four, although lake chub older than four have been found. (Becker, 1983; Fuiman and Baker, 1981)

Reproduction

During spawning, male lake chub actively pursue females to induce mating. When a female is near a spawning-ready male or males, the males charge her from beneath and tenaciously nose her vent region, forcing the female upward, sometimes resulting in her breaking the water surface. The male then swims next to the female's operculum, and if multiple males are still present, they swim side by side to compete for a position next to the female. During this courtship process, the male's lateral body stripe becomes darker and more distinct, and their mouth opens and closes rapidly. This process continues until the female swims to a rock, when the remaining male forces himself against her, vibrating vigorously until the eggs are extruded from her, resulting in immediate fertilization by the male. (Brown, et al., 1970)

Lake chub spawning occurs in the spring at lower latitudes and later in the summer in higher latitudes. Lake chub have the ability to spawn in a diverse range of habitats and substrates, including river shallows, along rocky shores, in lake shoals, and on silt, leaves, gravel, or rocks. However, they most frequently enter creeks and streams or travel along lakeshores to spawn, although river-breeding chub do not intermingle with lake-breeding chub. Spawning migrations can range from less than 0.8 km (0.5 miles) to up to 1.6 km (1 mi). Temperature is a major factor in regards to sperm development, as low temperatures (5-12°C, 41-53.6°F) during the winter before spawning are necessary for normal gonadal proliferation and the formation of the primary spermatocytes. Temperatures higher than these can result in premature sperm production, or even termination. At the other end of the process, if temperatures are too high after spawning the disappearance of spermatids and sperm can occur, as well as a rapid regression of the testis. (Becker, 1983; Brown, et al., 1970; Stasiak, 2006)

  • Breeding interval
    Breeding generally occurs several times per minute, however, each act of spawning only lasts about one second.
  • Breeding season
    Depending on the region, lake chub spawning occurs during the spring or summer months.
  • Range number of offspring
    800 to 2400
  • Range time to hatching
    8 to 10 days
  • Average age at sexual or reproductive maturity (female)
    Age class III years
  • Average age at sexual or reproductive maturity (male)
    Age class III years

There has been no evidence of parental care of eggs or juveniles by lake chub, nor has any nest construction been documented. (Becker, 1983)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Very few lake chub live past the age of four years. However, their average lifespan is about five years and they have been known to live up to seven years. Female lake chub are thought to grow faster and live longer than males. (Coad, et al., 1995; Scott and Crossman, 1973)

  • Range lifespan
    Status: wild
    7 (high) years
  • Average lifespan
    Status: wild
    4 years

Behavior

Lake chub are a social species that aggregate in large schools and migrate to spawning grounds together in the spring, but shift to deeper waters in the summer for cooler temperatures. This species is considered diurnal. However, during times of migration, when diurnal predators are more aware of their presence, lake chub may become active during the night, presumably to avoid predation. This change shows possible flexibility in their activity patterns. (Reebs, 2001; Smith, 2010)

Home Range

These fish migrate for spawning each year. These migrations can range from less than 0.8 km (0.5 miles) to up to 1.6 km (1 mi). (Becker, 1983; Brown, et al., 1970; Stasiak, 2006)

Communication and Perception

Lake chub are thought to lack external taste buds, therefore perception is achieved through the use of vision. (Davis and Miller, 1967)

Food Habits

Young lake chub consume small aquatic crustaceans such as cladocerans and copepods. These crustaceans remain in their diet as they grow older; however, older lake chub primarily consume insects, although some individuals also consume small amounts of snails and fish eggs. Because lake chub have an almost complete lack of external taste buds, they are most likely obligatory sight feeders. (Becker, 1983; Davis and Miller, 1967)

  • Animal Foods
  • fish
  • eggs
  • insects
  • aquatic crustaceans

Predation

Known predators of lake chub include both predatory fishes and birds such as lake trout, burbot, walleyes, and northern pike, as well as mergansers, kingfishers, and common loons. They also have several mammalian predators such as minks, martens, otters, fishers, and raccoons. To avoid such predators in areas where they are especially susceptible to predation, such as streams during spawning, these diurnal fish have been known to be more active during the night. Lake chub larvae and juveniles also have their own predators, including diving beetles, giant water bugs, and dragonflies. (Coad, et al., 1995; Reebs, 2001; Scott and Crossman, 1973; Stasiak, 2006)

Ecosystem Roles

Lake chub have often been found as hosts to many types of small parasites including the larval form of trematodes (Diplostomulum and Posthodiplostomum minimum), the adult form of nematodes (Rhabdochona), acanthocephalans (Echinorhynchus salmonis), Protozoa, cestodes, glochidia, and crustaceans (Ergasilus caeruleus). In many cases, lake chub actually act as an intermediate host, with the final development phase taking place in birds and other fishes. (Scott and Crossman, 1973)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Lake chub have been beneficial to humans for food both directly and indirectly. They are directly beneficial as commonly used live bait for early spring fishing, especially in Canada. In addition, smaller lake chub are often caught and eaten under the mistaken impression that they are smelt. (Coad, et al., 1995; Scott and Crossman, 1973)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Brook trout anglers frequently complain that lake chub interfere with their angling, as they often catch lake chub instead of brook trout. (Becker, 1983)

Conservation Status

According to the IUCN Red List, lake chub are a species of least concern due to the large extent of their occurrence, the large number of subpopulations, their large population size, their apparently stable population trends, and their lack of major threats. (NatureServe, 2013)

Contributors

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

Glossary

Nearctic

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

insectivore

An animal that eats mainly insects or spiders.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

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

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

sexual

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

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

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).

visual

uses sight to communicate

References

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

Bestegen, K., K. Fausch, S. Riley. 1991. Rediscovery of a relict southern population of Lake Chub, Couesius plumbeus, in Colorado. The Southwestern Naturalist, 31/1: 125-127.

Brown, J., U. Hammer, G. Koshinsky. 1970. Breeding biology of the lake chub, Couesius plumbeus, at Lac la Ronge, Saskatchewan. Journal of the Fisheries Board of Canada, 27/6: 1005-1015.

Coad, B., H. Waszczuk, I. Labignan. 1995. Encyclopedia of Canadian Fishes. Waterdown, Ontario: Canadian Museum of Nature and Canadian Sportfishing Productions Inc.

Davis, B., R. Miller. 1967. Brain patterns in minnows of the genus Hybopsis in relation to feeding habits and habitat. Copeia, 1: 1-39.

Fuiman, L., J. Baker. 1981. Larval stages of the lake chub, Couesius plumbeus. Canadian Journal of Zoology, 59/2: 218-224.

NatureServe, 2013. "IUCN Redlist of Threatened Species" (On-line). Couesius plumbeus. Accessed July 21, 2014 at http://www.iucnredlist.org/details/202072/0.

Reebs, S. 2001. Fish Behavior in the Aquarium and in the Wild. United States of America: Cornell University Press.

Scott, W., E. Crossman. 1973. Lake chub: Couesius plumbeus (agassiz). Pp. 401-406 in Freshwater Fishes of Canada, Vol. 184, 1 Edition. Canada: The Bryant Press Limited.

Smith, G. 2010. Guide to Great Lakes Fishes. United States of America: The University of Michigan Press.

Stasiak, R. 2006. "USDA Forest Service, Rocky Mountain Region" (On-line). Lake Chub (Couesius plumbeus): A Technical Conservation Assessment. Accessed December 03, 2013 at http://www.fs.fed.us/r2/projects/scp/assessments/lakechub.pdf.

Wells, A. 1980. Couesius plumbeus (Agassiz), Lake Chub. Pp. 854 in D Lee, ed. Atlas of North American Freshwater Fishes, Vol. 1980, 12 Edition. Raleigh, North Carolina: North Carolina State Museum of Natural History.

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