Ciscoes (Coregonus species, and of all of them, ciscoes occur most often in shallow waters and shoals. In Wisconsin, populations tend to be concentrated in northern waters. Specific Wisconsin localities include the Mississippi River, Lake Michigan, and Lake Superior drainage basins. Ciscoes are common in Wisconsin’s northern inland lakes but are rare in Madison-area lakes. ("Distribution and abundance of the lake herring (Coregonus artedi) in Michigan", 1995; "Lake Herring, Coregonus artedi", 2014; Becker, 1983; Luna, 2014; Todd and Smith, 2011)) are confined to the Nearctic region. These fish are distributed throughout Canada and the northern United States. Localities include the St. Lawrence Seaway and the Great Lakes. In a north-south direction, ciscoes range from the upper Mississippi drainage in the United States to the Northwest Territories and Alberta in Canada. Ciscoes occur throughout the Great Lakes. In Michigan, most inland lake populations occur in the southern portion of the state, from Oakland County, south to Cass County. Lake Superior is the only lake where ciscoes are abundant; low populations are characteristic of lakes Erie, Michigan, Ontario, and Huron. There are many
Ciscoes occur in pelagic, cold-water Great Lakes and inland lake environments. During the winter months, they move into shallow coastal waters to spawn, but then return to deeper waters in the spring. Ciscoes are rarely found in waters above 17 to 18ºC. They can live in lakes with surface areas ranging from 20 to 19,000 acres, but are mostly found in lakes with an average surface area of 100 acres and depths of at least 10 m. Cisco-rich lakes tend to be oligotrophic. ("Distribution and abundance of the lake herring (Coregonus artedi) in Michigan", 1995; "Lake Herring, Coregonus artedi", 2014; Becker, 1983; Wells, 1968)
Ciscoes have an average length of 267 mm; they are elongated, nearly round in cross section. They are silvery in color and are usually recognized by their 44 to 52 gill rakers. Their dorsal fins have around 9 to 11 rays and their scales are moderately sized. The lower jaw is either shorter than, or the same length as the upper jaw, and two flaps exist between the nostrils. Identifying ciscoes can be difficult due to the several morphologically similar species within the Coregonus genus; while genetically distinct, the six currently recognized Coregonus species exhibit fewer differences from one another than is typically required to distinguish separate taxa. ("Distribution and abundance of the lake herring (Coregonus artedi) in Michigan", 1995; "Lake Herring, Coregonus artedi", 2014; Bailey, et al., 2004; Becker, 1983; Koelz, 1929)
Since ciscoes spawn in the winter, their eggs develop slowly and typically hatch in the spring as surface ice begins to thaw. Cisco fry usually live in shallow bays until they are around one month old, and usually mature within 1 to 4 years. ("Lake Herring, Coregonus artedi", 2014; Becker, 1983)
Ciscoes aggregate for spawning as temperatures decrease in the fall. Males typically arrive at the spawning grounds before females and are also the first ones to leave. ("Lake Herring, Coregonus artedi", 2014)
Ciscoes usually spawn in late November to mid-December in near-shore waters that are around 5 to 6ºC. Spawning rates tend to peak when temperatures fall below 4ºC. Eggs are deposited at night on top of rocky substrates. While spawning, ciscoes can be seen jumping and splashing. (Becker, 1983)
After eggs are deposited in near-shore environments, they are abandoned by the parents. ("Lake Herring, Coregonus artedi", 2014)
Ciscoes have an average lifespan of 6 to 10 years, with a maximum age of 13 years. Interestingly, their scales may be used to estimate their age. ("Lake Herring, Coregonus artedi", 2014; Scott and Crossman, 1998)
Ciscoes move constantly. These fish form schools during the day, but disperse during the night. Schools, which are usually around 1 to 2.3 meters tall, tend to form well below the light threshold at which their primary predators, lake trout are able to detect prey. The stomachs of ciscoes are usually fuller during the day, likewise, stomach fullness increases with school size, suggesting schooling aids in predator protection as well as foraging. ("Lake Herring, Coregonus artedi", 2014; Milne, et al., 2005)
Ciscoes usually live their entire life within a few kilometers of where they hatched, though in some cases, individuals may travel about 81 km from where they hatched. (Becker, 1983; Smith and Van Oosten, 1940)
Very little is currently known about the methods of communication used among ciscoes. However, their social nature and ability to move as a school implies the use of intraspecific communication.
When the waters they inhabit freeze over, ciscoes can perform vertical diurnal movements to feed under the ice at night. As planktivores, they typically feed on algae and small crustaceans (Cladocera, Copepoda, and Mysis); infrequently they feed on mollusks, insect larvae, and small fish. Young individuals typically need light in order to find their prey. Fry feed on algae and zooplankton, while adults tend to feed on crustaceans and aquatic insects. ("Lake Herring, Coregonus artedi", 2014)
Schooling is the primary means by which ciscoes avoid predators like lake trout. Other predators include northern pike, yellow perch, walleye, sea lamprey, rainbow trout, and burbot. ("Lake Herring, Coregonus artedi", 2014; Anderson and Smith, 1971)
As a main source of prey for lake trout, yellow perch, walleye, and northern pike, ciscoes play a key role in the Great Lakes ecosystem. However, between 1930 and 1960, over-exploitation, pollution, and competition with non-native species like rainbow smelt decimated their populations. As the number of rainbow smelt climb in inland lakes, the population of ciscoes plummet and disappear completely in areas where rainbow smelt eat their fry and fingerlings. Great Lake populations, along with native predator-prey relationships have yet to rebound. Around 1963, lake trout were nearly wiped out of the area once cisco populations began their most significant collapse. From 1943 to 1963, lake trout populations declined from around four million pounds to close to zero, while populations of ciscoes declined from 19 million pounds in 1943 to around six million pounds in 1963. ("Lake Herring", 2014; "Lake Herring, Coregonus artedi", 2014; Anderson and Smith, 1971; Gunderson, 2004)
Historically, ciscoes are one of the most commercially important fish in the Great Lakes; in the 1940s, cisco fisheries were producing around 19 million pounds annually. (Gunderson, 2004)
There are no known negative impacts of ciscoes on humans.
Severe over-exploitation of ciscoes from 1930 to 1960, as well as competition with invasive rainbow trout, resulted in dramatic population declines. Other potential competitors include alewives and bloaters. However, rainbow trout populations collapsed in the 1970s, and since that time, ciscoes have been slowly rebounding. The greatest current threat to cisco populations in the Great Lakes is eutrophication. This causes oxygen depletion in lower lake strata, forcing ciscoes into shallower, warmer parts of the water column. These higher temperatures, particularly during the summer months, cause large numbers of the fish to die. Because ciscoes are so sensitive to temperature fluctuations, their responses to eutrophication are thought to be a good indicator of the adverse effects of global warming. In the 1950s, cisco eggs were incapable of hatching in the lower Green Bay due to the incredibly low dissolved oxygen levels (2 mg/L). Currently, cisco egg survival in the Green Bay is around 65%, with a dissolved oxygen level of 11.2 mg/L. These levels are well above the dissolved oxygen needed for cisco eggs to hatch. The St. Mary's River, which runs from Ontario to Michigan, currently exhibits dissolved oxygen levels of 12.7 mg/L, with an egg survival rate of 64%. Recently, the Michigan Department of Natural Resources has implemented a cisco recovery plan for Lake Huron. Since overfishing is no longer a problem, it is thought that competition with rainbow smelt and alewives has kept cisco populations low. One of the motivations for restoring cisco populations is to control alewife populations. Alewives predate on the fry of fish like the economically important lake trout, and it is thought that more abundant cisco populations will help combat this. (Luna, 2014; "Strategy and Options for Promoting the Rehabilitation of Cisco in Lake Huron", 2007; Anderson and Smith, 1971; Becker, 1983; Madenjian, et al., 2011)
Lucas Joel (author), University of Michigan-Ann Arbor, Jeff Schaeffer (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.
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
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
An animal that eats mainly plants or parts of plants.
An animal that eats mainly insects or spiders.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
an animal that mainly eats plankton
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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