Brighteye darter

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Brighteye darter
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Percidae
Genus: Etheostoma
Species: E. lynceum
Binomial name
Etheostoma lynceum
Hay, 1885

The brighteye darter, Etheostoma lynceum is one of the many darters to inhabit the streams and tributaries of the Mississippi River in Alabama, Kentucky, Louisiana, and Tennessee (one of the 324 fish species found in that state).

The brighteye darter is found in quick-flowing water, gravel riffles, and around tree litter.[2] This species uses these attributes of the stream where they reside to spawn in late February into May and even sometimes into June. Female reproduction maturity occurs in about a year.[3] This darter's main food supply is aquatic invertebrate larvae. Currently, no management plans are in place for Etheostoma lynceum, because of their great abundance and large distribution over several states. Rechannelization, where humans are moving the natural flow of water for their benefit, may cause declines, but the brighteye darter continues to persist in remaining suitable habitats.[4] Continued surveys of Etheostoma lynceum should be conducted in a biannual basis, preferably before and after spawning, to allow a count of individuals; it could be compared to reproductive success later in the year to see if rechannelization is causing a main threat or not. Along with these tests, water quality reports should be done, as well. Rechannelization may be causing too much sedimentation to form and removal of natural gravel and tree litter which the brighteye darter uses for cover and spawning.

Distribution

E. lynceum inhabits the lower, benthopelagic areas of freshwater streams and rivers. The brighteye darter is distributed in eastern tributaries of the Mississippi River from Louisiana north to western Tennessee and eastward along the Gulf Coast to the Escatawpa River system in the Mobile County.[5] It can also be found in the former Mississippi embayment in the western part of Kentucky, and in coastal drainages from the Escatawpa River in Alabama to the Mississippi River in Louisiana. Rechannelization may have extirpated them from some of their natural ranges into Alabama, but the brighteye darter has been able to find more suitable streams as they travel up the Mississippi River system.[6]

Ecology

The brighteye darter mainly feeds on invertebrates, mainly from flies (Chironomidae) such as the sand fly, the mucklehead, and the mufflehead.[7] The larval stages of these flies are an important component of the bottom of the aquatic ecosystem in which the brighteye darter resides. The darter will watch for the larval stage to erupt from its egg casing and eat it before it has time to swim off. These flies hatch year long and make up 75-80% of the darters' diets. In comparison to other darters to which the brighteye is related, it does not change food source from season to season. Other darters, such as Percina nigrofasciata, can change their diets with every season, thus having much more diverse diets. E. lynceum prefers clear, fast-flowing water, with gravel riffles. This type of habitat can be found in several places around the Mississippi River Basin. Regarding habitat change, the main problem is humans changing the way a stream flows or making the water too dirty for the darter to live well, thus causing problems for feeding and breeding.[8]

Lifecycle

The brighteye darter was first described by Hay in 1885. He noted it is closely related to the banded darter, E. zonale. Until the 1970's, most scientists thought the brighteye was just a genetic variation of the banded darter.

The brighteye reproduces from late February to May. The bright male coloring emerges then, as well as female maturity. The algae forming on the rocks of the streams makes a great adhesive area for the eggs of the female to attach. The clutch size and mass increases significantly in the spawning season, unlike the size of the egg. Ovulated eggs can be 1.2-1.5 mm in size.[9] After the darter hatches, growth is quick, and it reaches a maximum length of 65 mm. It takes the brighteye an average of one year for it to grow to maturity and be able to reproduce.[10]

Management

Currently, no management plan is in place for E. lynceum, mainly due to its ability to react to environmental stressors easily and its widespread distribution. It is also placed on the "Least Concern" list of the federally endangered species of United States. The brighteye darter is protected in the states where it is found, especially in Mississippi.[11] However, the main threat to the brighteye is stream rechannelization, mostly in Alabama. Rechannelization is described as the control and use of rivers for the benefit of humankind (controlling flooding, stabilizing areas species-specific management, or wetland drainage).[12] While this may seem like a good idea, it can actually worsen the natural habitat for many aquatic species. The main purpose of rechannelization of rivers is to straighten and deepen them to provide faster-moving water and ease of boat travel. However when this is done, extreme amounts of siltation and habitat destruction occurs.[13] The brighteye darter needs algae to spread its eggs and clear water for reproduction. If these two qualities are not present in a stream, the darter cannot flourish.

References

  1. ↑ NatureServe (2013). "Etheostoma lynceum". IUCN Red List of Threatened Species. Version 3.1. International Union for Conservation of Nature. Retrieved November 22, 2013. 
  2. ↑ Heins DC, Baker JA, Guill JM (2004) Seasonal and interannual components of intrapopulation variation in clutch size and egg size of a darter. Ecol Freshw Fish 13:258–265
  3. ↑ Heins, D. C. and Baker, J. A. 1993. Reproductive biology of the brighteye darter, Etheostoma lynceum (Teleostei: Percidae), from the Homochitto River, Mississippi. Ichthyological Explorations of Freshwaters 4: 11–20. [CSA]
  4. ↑ Geological Survey of Alabama. 2008. Brighteye Darter in Alabama. <www.outdooralabama.com>
  5. ↑ NatureServe (G. Hammerson) 2010. Etheostoma lynceum. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. <www.iucnredlist.org>. Downloaded on 26 September 2012.
  6. ↑ Hay. 1885. Etheostoma lynceum, The Brighteye Darter. <www.fishbase.org/summary/Etheostoma-lynceum.html>
  7. ↑ Alford JB, Beckett DC. 2007. Selective predation by four darter (Percidae) species on larval chironomids (Diptera) from a Mississippi stream. Environmental Biology of Fishes 78: 353–364.
  8. ↑ Schweizer PE, Matlack GR (2005) Annual variation in fish assemblages of watersheds with stable and changing land use. Am Midl Nat 153:293–308
  9. ↑ Heins, D. C. and Baker, J. A. 1993. Reproductive biology of the brighteye darter, Etheostoma lynceum (Teleostei: Percidae), from the Homochitto River, Mississippi. Ichthyological Explorations of Freshwaters 4: 11–20. [CSA]
  10. ↑ Ross, et al. 2001. Etheostoma lynceum. Mississippi Department of Wildlife, Fisheries, and Parks.
  11. ↑ Ross, et al. 2001. Etheostoma lynceum. Mississippi Department of Wildlife, Fisheries, and Parks.
  12. ↑ McGraw-Hill. 2002. River Engineering. <www.thefreedictionary.com>
  13. ↑ Brooker, M.P. 1985. The Impact of River Channelization. JSTOR: The Geographical Journal. Vol. 151, No. 1 (Mar., 1985), pp. 63-69
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