Fish in the perch family (Percidae) are able to see and hear as well as detect vibrations in the water. Evidence for vision comes from female mate selection during the spawning season. Males with brighter coloration have a higher success rate at attaining a mate.
Communication Channels: visual
Perception Channels: visual ; tactile ; vibrations ; chemical
Least darter populations are in decline, though they are not formally recognized as threatened or endangered. Their conservation status is not evaluated by the IUCN Red List of Threatened Species. Major concerns to their population include habitat loss, pollution, invasive species, agricultural pesticides and deforestation. Efforts to conserve them are gaining recognition. In southern Minnesota, least darter populations were surveyed by the DNR and older populations have gone extinct due to anthropogenic development. New sites have been discovered in Minnesota; however, no plans have been established to mitigate the decline. In 2008, a conservation budget proposal in Arkansas listed objectives including monitoring population size, investigating extinction causes, and determining survival status and distribution. Their population is at risk because they are small fishes with a high dispersal between populations.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Male and female least darters grow at the same rate. They reach an average of 29 mm after one year and grow to approximately 34 mm by the second spawning season. Once fully developed, females are generally larger than males.
Least darters do not have any known negative impacts on humans.
Least darters do not provide any known economic benefits for humans.
Least darters are both predators and prey in their ecosystem. They are not known to become infected with any parasites.
The diet of least darters consists of micro-crustaceans, aquatic invertebrate larvae, copepods (Copepoda) and water fleas (Cladocera).
Animal Foods: insects; aquatic crustaceans; other marine invertebrates; zooplankton
Primary Diet: carnivore (Eats non-insect arthropods)
Least darters inhabit the Great Lakes and the Mississippi River Basin in the northern United States, as well as southern Ontario in Canada. They are also found in western Ohio, Illinois and Indiana, and in isolated areas of Oklahoma, Arkansas, Kansas and Missouri.
Biogeographic Regions: nearctic (Native )
Least darters thrive in bodies of water in temperate boreal forests and temperate grasslands. Grassland temperatures can range from -40 degrees F to 100 degrees F. Both of these biomes have relatively short summers and long winters. The aquatic environment that least darters require consists of sandy-bottomed streams and areas of dense vegetation. Organic sediments and silt are also preferred. Least darters require slow moving freshwater streams, ponds, and rivers that have dense vegetation. This habitat provides refuge from predators and a safe place for spawning. They choose shallow pools for optimal survival of offspring during the spawning season. After spawning, least darters return to deeper waters.
Average elevation: 1000 m.
Habitat Regions: temperate ; freshwater
Aquatic Biomes: lakes and ponds; rivers and streams; temporary pools
Most least darters do not survive past the first breeding season, and live only 13 to 14 months. Almost all that live a second year die shortly afterwards. However, 3-year-old least darters have been reported in the wild. Least darters in captivity tend to live longer.
Average lifespan
Status: wild: 3 years.
Range lifespan
Status: captivity: 0 to 3 years.
Average lifespan
Status: captivity: 2 years.
Typical lifespan
Status: wild: 13 to 14 months.
Average lifespan
Status: captivity: 2 years.
Least darters are part of the perch family. They are differentiated from other closely related species by their small size and species-specific coloration. Least darters appear much longer than they are wide, and their bodies are small and compressed. Their ctenoid scales are rough in texture. They are light olive in color with 6 to 12 black blotches along their spine. Several dark radiating lines can be observed originating from the eyes. Females are slightly larger than males. Females in the breeding season have yellow fins, while males develop orange or red spots on the dorsal fins. Male pelvic fins also become flushed with hues of red and orange.
Darker coloration on the spine of least darters known as counter-shading helps them blend into the habitat when viewed from above. The black blotches located on the spine are an example of coloration disruption. This allows the fish to blend in with their surroundings. This adaptation allows for predator evasion.
Range mass: 0.20 to 0.38 g.
Range length: 3.1 to 4.4 cm.
Average length: 4 cm.
Other Physical Features: ectothermic ; bilateral symmetry
Sexual Dimorphism: female larger; sexes colored or patterned differently; male more colorful
Predators of least darters include turtles (Testudines), birds, and larger fish. Depending on the location and fauna in the area the predation rate of least darters varies. However, due to their preference for high vegetation, they avoid many predators.
Known Predators:
The breeding season of least darters depends on location. In the southern regions of the United States, spawning begins in February. In northern regions from Illinois to Minnesota up into southern Canada, the mating season begins in late May and continues to late July. Males locate a territory of 5 to 10 cm and include one or two plants. In wild populations, territories have been observed as large as 30 cm. Males chase rival fish from their territory. This behavior usually consists of head-to-tail nudging. Once a female enters a male's territory for the purpose of mating, she approaches the vegetation. The males grasps her back with his pelvic fins, encouraging her to release her eggs. Immediately after she releases her eggs, males release milt to fertilize them. Females mate with multiple males.
During the spawning season, least daters undergo changes to make them more attractive to mates. They turn a darker green color and black blotches appear more visible. The anal fin and pelvic area turn a bright orange, while the dorsal and caudal fins turn a white color banded with gray.
Mating System: polyandrous
Least darters reach sexual maturity by the first spring after hatching. Males locate a territory and defend it from other males. Spawning begins once a female enters a male's territory. Males swim in a ritual-like fashion to entice the female to copulate. The female attaches her eggs to an aquatic substrate and exits the territory. Paternal care continues as the males remain territorial over the fertilized egg clutch. The eggs of a first-year spawning female are usually small and opaque white in color. Little to no parental care is given to the offspring. Males protect the eggs for a period of time after fertilization, but may leave before hatching in attempt to fertilize the clutch of another female.
Breeding interval: Least darters breed once per year and have 3 clutches.
Breeding season: Least darters breed from May to late July.
Range number of offspring: 80 to 200.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; sexual ; fertilization (External ); broadcast (group) spawning; oviparous
No maternal care is observed after spawning. Paternal care consists of territory protection until eggs hatch. Closely related darters (Percidae) either display paternal care or non-parental care. The paternal care shown by the least darter has been speculated to have evolved 3 separate times throughout the evolution of the darter family.
Parental Investment: male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male); pre-weaning/fledging (Protecting: Male)
