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Greenside darter

Etheostoma blennioides

What do they look like?

Greenside darters are olive-green with dark spots. They have large eyes and a rounded snout. They have two dorsal fins and their pectoral fins are large and well-developed. Greenside darters can be distinguished from other darter species by their larger size and different coloration.

  • Sexual Dimorphism
  • male larger
  • male more colorful
  • Average length
    76 mm
    2.99 in

Where do they live?

Greenside darters are restricted to a few major watersheds of North America. The range extends from New York west to Kansas and south to Alabama, mostly within the Mississippi River and its tributaries. Greenside darters are also found in the Lake St. Clair and Thames River system in southwestern Ontario, Canada. Greenside darters are most common in creeks and rivers in east-central North America.

What kind of habitat do they need?

Greenside darters spend their lives on the bottoms of rivers, streams and lakes. They live in deeply ridged habitats consisting of cobble and loose boulders covered by thin, thread-like green algae upon which they lay their eggs. These fish also prefer moderate to fast-moving water that is mostly clear.

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

How do they grow?

Eggs are laid on algae and after hatching no more parental protection is given. Greenside darters are very delicate when they first hatch, and even very small changes in feeding or water quality can cause death. They begin feeding on plankton 8 days after hatching and after about 2 weeks the fry start going to the bottom of the body of water and acting like adults. Their initial growth is rapid but generally greenside darters are short lived and typically survive for up to three years.

How do they reproduce?

Both sexes of greenside darters reach sexual maturity and spawn in the spring 1 year after hatching. Breeding only occurs when the water temperature has reached a certain level and spawning is also restricted to specific areas. Greenside darters spawn in pairs, but will ultimately spawn with many different partners over the course of one breeding season. Spawning lasts for a 4-5 week period. Males perform an elaborate ritual to establish dominance and claim territory, but the female will choose the actual spawning site.

The breeding season of greenside darters is from April to June and spawning activity peaks in May. Males select a small area to defend as their mating territory, and then proceed to initiate spawning through elaborate courtship dances. Once a pair is formed, the female selects a site in algae and waits for a suitable male to arrive. The two mate and the fertilized eggs are algae just near where it attaches to the rock. A pair may spawn more than once at short time intervals. Both sexes will also spawn with many different partners over the breeding season. (Miller, 1968; Muller, 2000; Radabaugh, 1989; Smith, 1985)

  • Breeding season
    April to June
  • Range number of offspring
    370 to 1400
  • Average time to hatching
    19 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    365 days
  • Average age at sexual or reproductive maturity (male)
    1 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    365 days

Most darters provide little or no parental care other than attaching their fertilized eggs to the bases of algae where they are less visible to predators. Sometimes males have been observed guarding fertilized eggs, but this may become more difficult over the course of the spawning season as these males continue to mate with multiple females.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • male

How long do they live?

Greenside darters typically live up to 3 or 4 years in the wild. Lack of food and habitat can limit growth and survival. Too much sediment smothers eggs and decreases the abundance of common prey items, such as mayflies. This may also affect darter reproduction by blocking light needed for algae to grow in darter spawning habitats.

  • Range lifespan
    Status: wild
    5 (high) years
  • Average lifespan
    Status: wild
    3 years
  • Average lifespan
    Status: wild
    3 years
  • Average lifespan
    Status: captivity
    5 years

How do they behave?

Home Range

During the spawning season, each male will select and defend a small area 100 centimenters in diameter or less.

How do they communicate with each other?

Like many other perch, darters communicate mainly through body color. Males use their bright colors to intimidate other males and to court females. Females may also signal to males through changes in body.

  • Communication Channels
  • visual

What do they eat?

Greenside darters feed on aquatic insects from 1 to 6 mm in size, but their diet changes depending on the season and what kind of prey are available. They mostly eat midge larvae, but they also eat mayfly, stonefly, and blackfly larvae.

  • Animal Foods
  • insects

What eats them and how do they avoid being eaten?

Smallmouth bass and several kinds of trout (brook, brown, and rainbow) prey on darters. Common mergansers also eat greenside darters along their migration route.

Many darters avoid being preyed on by other fish through a behavior known as "freezing" -- when a predator is present, the fish will stop moving for a little while. Freezing is the best strategy for non-breeding males because their color blends in with the surroundings. In greenside darters, the bright green breeding color of males also helps to camouflage them.

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Besides serving as both predators and prey in their ecosystems, greenside darters are also important in the reproduction of several freshwater mussels, including endangered species. Microscopic mussel larvae, also known as glochidia, attach to the gills of certain fish, including greenside darter, immediately after they are released into the water. Because mussels cannot swim, the fish provides their means of transportation and distribution into other areas of the stream.

Do they cause problems?

There are no known adverse effects of E. blennioides on humans.

How do they interact with us?

While greenside darters have no commerical value and are not regarded as a sport fish, they are often used as aquarium species. They are also useful for scientific investigations of ecology.

  • Ways that people benefit from these animals:
  • pet trade
  • research and education

Are they endangered?

Although greenside darters are not officially listed as endangered or threatened, they are considered vulnerable in Canada and rare in Kansas and Mississippi.


Sharon Graham (author), University of Michigan-Ann Arbor, William Fink (editor, instructor), University of Michigan-Ann Arbor, Renee Sherman Mulcrone (editor).


2004. "Discover Life in America" (On-line). Greenside darter. Accessed October 25, 2004 at

2003. "Upper Thames River Conservation Authority" (On-line). More on Freshwater Mussels. Accessed October 28, 2004 at

Bailey, R., W. Latta, G. Smith. 2004. An Atlas of Michigan Fishes. Ann Arbor, MI: Miscellaneous PUblications, Museum of Zoology University of Michigan.

Bunt, C., S. Cooke, R. McKinley. 1998. Creation and maintenance of habitat downstram from a weir for the greenside darter, Etheostoma blennioides -- a rare fish in Canada. Environmental Biology of Fishes, 51 (3): 297-308.

Dalton, K. 1991. Status of the Greenside Darter, Etheostoma blennioides, in Canada. Canadian Field-Naturalist, 105 (2): 173-178.

Englert, J., B. Seghers. 1983. Predation by fish and common mersangers on darters (Pisces: Percidae) in the Thames River Watershed of southwestern Ontario. Canadian Field Naturalist, 97 (2): 218-219.

Gray, E., J. Boltz, K. Kellogg, J. Stauffer. 1997. Food Resource Partitioning by NIne Sympatric Darter Species. Transactions of the American Fisheries Society, 126 (5): 822-840.

Hlohowskyj, I., A. White. 1983. Food Resource Partitioning and Selectivity by the Greenside, Rainbow, and Fantail Darters (Pisces: Percidae). Ohio Journal of Science, 83 (4): 201-208.

Jenkins, R., N. Burkhead. 1993. Freshwater Fishes of Virginia. Bethesda, Maryland: American Fisheries Society.

Katula, R. 2000. "Tropical Fish Hobbyist" (On-line). The Captive Maintenance of Darters. Accessed October 28, 2004 at

McFarland, K., R. Strange. 2003. "Percis III: The Third International Percid Fish Syposium" (On-line). Evolution of Color and Contrast Communication of Darters. Accessed October 28, 2004 at

Miller, R. 1968. A Systematic Study of the Greenside Darter, Etheostoma blennioides Rafinesque (Pisces: Percidae). Copeia, 1: 1-40.

Muller, B. 2000. Spawning and Raising the Greenside Darter, Etheostoma blennioides, with a Note on the Eggs of the Rainbow Darter, E. caeruleum . American Currents, 26 (2): 11-12.

Radabaugh, D. 1989. Seasonal Color Changes and Shifting Antipredator Tactics in Darters. Journal of Fish Biology, 34: 679-685.

Scott, , Grossman. 1998. Freshwater Fishes of Canada. Ontario, Canada: Galt House Publishing.

Shiels, A. 2003. "Pennsylvania Fish and Boat Commission" (On-line). Pennsylvania's Dynamic Darters. Accessed October 28, 2004 at

Smith, C. 1985. The Inland Fishes of New York State. New York, NY: New York State Department of Environmental Co..

Wynes, D., T. Wissing. 1982. Resource Sharing Among Darters in an Ohio Stream. American Midland Naturalist, 107 (2): 294-304.

University of Michigan Museum of ZoologyNational Science Foundation

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Graham, S. 2004. "Etheostoma blennioides" (On-line), Animal Diversity Web. Accessed May 22, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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