Semotilus corporalis

Geographic Range

Fallfish ( Semotilus corporalis ) are native only in the North America (Neartic region). The northern range of fallfish is as far north as the southern tip of the Hudson bay in Canada. The southern border of their range is the U.S border between Virginia and North Carolina. These fish range as far west as the Appalachian Mountains in the U.S and as far as Lake Superior in Canada. The eastern border reaches the Atlantic ocean, but does not include it.

In some parts of the range above (e.g., New York and Virginia), fallfish have been introduced into drainages.

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
  • native native

Habitat

Fallfish are most common in freshwater low-gradient streams with forest cover in riparian areas at elevations between 73 and 767 meters above sea level. These minnows are limited to temperatures between 6 and 27°C; however, temperatures below 15°C inhibit spawning. The young are often found in faster flowing currents, while older minnows can often be found in slower moving pools along the stream. Across all ages, pools are the preferred habitat. Fallfish live and forage in areas of the watershed that are around 30-50 cm deep.

Fallfish in northern parts of their geographic ranges also live in lentic habits (lakes), while those in the south are restricted to lotic habitats.

• Habitat Regions
• freshwater freshwater

• Aquatic Biomes
• rivers and streams

Physical Description

Adult fallfish are one of the largest minnows in the U.S and Canada growing to lengths between 155-431 millimeters in length and girth up to 80 millimeters. Upon maturity, fallfish weigh between 720 to 1800 grams. The females grow to longer lengths then their male counterparts reaching an average length of 166 mm where as males grow to lengths of 155 mm.

Fallfish heads are rounded and smooth due to a lack of scales. They have overhanging mouthing forming a snout and a characteristic large eye. Adult fallfish have thick, dark olive or golden-brown scales outlined in black running down their posterior spine. Their underbellies are covered in whitish-silver scales. Their tails (caudal fin) bend downward and are forked and contain about 19 bony rays. The tips of their caudal fin is black. Anterior to the caudal fin, there are 8 rays that form the anal fin. Both caudal and anal fins are generally the same color as the dorsal scales. Their dorsal fin is slightly inferior to the midpoint of their backs and contains 7 rays.

Pinder (2017) reports that males in breeding condition have tubercles on their heads, concentrated around their eyes and near their noses. Juveniles of this species have dark stripes along their lateral sides, reaching from head to tail. By maturity, this stripe disappears.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes shaped differently

Development

Like most fish, fallfish show indeterminate growth over their lifespan. Males reach maturity at around 3 years of age and the female counterparts at 4 years of age. Upon hatching, a yolk sack is left over on the fallfish larvae for 5 to 7 days and will eventually be absorbed once the larvae reach 9 mm in total body length. The fins of fallfish larvae are absent at hatching and usually don't develop until the larvae are at least 9 mm long. Once the larvae reach 9 to 11 mm total body length and fins are present, their mouths becomes functional. At this time scales become pigmented. The rays, or bony spines, of the fins develop around the time that the larvae reach 14 mm in total body length and pigmentation of the scales intensifies superior to the developing dorsal fin. The fins fully develop when the larvae are at lengths over 18 mm. At this time, scale platelets form around the caudal peduncle and spread anteriorly until the larvae reach 33 mm. These scales are pigmented dark olive to golden brown.

• Development - Life Cycle
• indeterminate growth indeterminate growth

Reproduction

Fallfish are polygynandrous communal breeders. In spawning, males display a nest building behavior upstream of ridges or pits in the stream bed. They spent 1-4 days collecting nearby pebbles forming a mound where the females' eggs will eventually lay. These pebble nests are around 30-50 cm wide and 10-20 cm high. They can be as large as 2 m in diameter, making it the largest nest made by any fish.

After construction, the nest-building male releases pheromones attracting nearby females in hope of reproduction. Other male fallfish can also be attracted to another's nest, forgoing building their own nest, in hopes of fertilizing eggs released by females. This is referred to as satellite male behavior. Younger males are known to display satellite behavior more often than the older males.

During reproduction, dominant nest building males, and one to two satellite, or subdominate, males swim alongside one of the females and bend their caudal peduncles along the urogenital opening superior to the anal fin.The dominant male's peduncle manages to reach the female, stimulating her to raise her head and lower her caudal fin. This action causes the female to release her eggs in to the nest below. Satellite males then rush into the pebble nest to compete over fertilizing the awaiting eggs. The female engages in this spawning activity with the males that present a pebble for the nest.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Fallfish are seasonal promiscuous breeders, with one breeding season per year. At this time, multiple females lay eggs in awaiting pebble nests, allowing for males to fertilize them. Nest-building and satellite males attract and spawn with multiple females between March and June. Fertilized eggs take 139 to 144 hours (average = 140 h) to develop and hatch at temperatures above 17 C. The number of offspring is varied depending on their communal breeding and satellite male reproductive success.

Independence is upon hatching (no parental care) and birth weights have no been reported. Males reach sexual maturity after 2 to 3 years, while their female counterparts reach sexual maturity after 3 to 4 years.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

Neither the male or female fallfish engage in any form of parental investment beyond the act of spawning. Despite this, nest-building males devote time to create rocky pebble nests in order to attract females for spawning, but leave the nest after the eggs are fertilized. The females swim away from the nest after they have laid their eggs.

• Parental Investment
• no parental involvement

Lifespan/Longevity

Fallfish are known to live for 3-8 years with a maximum lifespan reaching 10 years. No information has been found concerning whether fallfish have ever been kept in captivity.

Behavior

Fallfish are a dinural species of minnow. This means that they forage, reproduce and perform their other activities during the day time hours. These minnows are migratory; they migration follows of variety of factors such as food availability and water temperature. Fallfish thrive higher water temperatures around 20°C. The younger minnows are often found in faster moving currents where food is at greater availability, but this behavior opens them up to predation and human activities such as fishing.

They are primarily a solitary species being one of the top predators in their habitat. They usually interect with others of their species during spawning behaviors. Dominance in this species takes part in satellite nesting behaviors for reproduction.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• nomadic nomadic
• migratory migratory
• solitary solitary
• dominance hierarchies dominance hierarchies

Home Range

Fallfish are very mobile. They have no true home range besides access to their entire stream. Their movements can influenced by a variety of factors including water level, food availability, water temperature, reproductive mates.

Communication and Perception

Communication between fishes occurs using chemical messengers called pheromones which are released from their bodies. These pheromones travel through a medium, water in this case, and are received by specialized cells on other aquatic life. Their pheromones can be harmful, inhibitory, threatening or attractive. These chemical pheromones have been found to correlate with several aspects of fish behavior such as shoaling, homing migrating fish, alarm mechanisms, crowding controls and spawning. Fish use pheromones to condition the water quality to attract mates, prey or to repel others such as with an overcrowding factor. In spawning behaviors, males excrete an pheromone to attract female fish. The pheromone attracts the female to a waiting nest where the male would brush across the female releasing further pheromone to signal for the desire to spawn.

• Communication Channels
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Fallfish are omnivorous and are truly opportunistic feeders. Their known diets consist of plankton, aquatic and terrestrial insects, insect larvae, small crustaceans, fish, fish larvae, mollusks, leeches and algae. The consumption of algae, though surprising, is a staple food for most cyprinid species. Fallfish primarily hunt and forage nocturnally between tca 2100 - 0500 h, with the most activity around midnight. The wild brown trout ( Salmo trutta ) and brook trout ( Salvelinus fontinalis ) provide direct competition in the foraging habits of fallfish.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • eats eggs
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore
  • vermivore
• herbivore herbivore
  • algivore
• omnivore omnivore
• planktivore planktivore

• Animal Foods
• fish
• eggs
• insects
• terrestrial non-insect arthropods
• mollusks
• aquatic or marine worms
• aquatic crustaceans

• Plant Foods
• algae
• phytoplankton phytoplankton

Predation

Fallfish are known to fall prey to larger fallfish as well as northern pike ( Esox lucius ) and fish-eating birds such as ospreys ( Pandion haliaetus ) and the American herring gull ( Larus smithsonianus ).

Ecosystem Roles

Fallfish are commonly one of the top predators in their environments. In Virginia, Pinder (2017) notes that fallfish were typically the apex predator in their environs until some species of bass were introduced.

They are often found to be infect with four known genera of parasites: Neoechinorhynchi , Allcreadium , Dactylocyrus and Ergasilus . Members of the genus Neoechinorhynchi are parasitic worms from the phylum Acanthocephala that invade the bodies of fallfish. Parasitic crustaceans, Ergasilus , are also known as gill lice; they infect the gills of fallfish. Trematodes in the genus Dactylogyrus also infect the gills of freshwater fish. Allocreadium is a genus of trematode parasites that infect the intestines of marine fish.

Economic Importance for Humans: Positive

Fallfish promote ecotourism in the Great Lakes and other watersheds within their habitat. Fallfish are used as bait to catch larger fish. This promotes areas where fallfish frequent, inviting people to visit. In Virginia, they are promoted as a low-cost and typically local option for fishing. The taste of fallfish is much debated.

• Positive Impacts
• food food
• ecotourism ecotourism

Economic Importance for Humans: Negative

The presence of fallfish have no known negative impact on humans.

Conservation Status

Fallfish are listed as a species of "Least Concern" on the IUCN redlist. Fallfish have no special status on the U.S Endangered Species list, the CITES appendices and the state of Michigan list. There are no known ongoing conservation efforts concerning fallfish. They are currently no restrictions in the use of fallfish as bait.

Additional Links

Encyclopedia of Life

Contributors

jacob McCoy (author), Radford University, Alex Atwood (editor), Radford University, Lindsey Lee (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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