Snubnose darter

Snubnose darter
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Percidae
Genus:	Etheostoma
Species:	E. simoterum
Binomial name
Etheostoma simoterum (Cope, 1868)

The common name of Etheostoma simoterum is the snubnose darter. It is one of the 324 fish species found in Tennessee.

Introduction

The following is a proposed conservation management plan for the snubnose darter Etheostoma simoterum. Two subspecies are recognized including the Cumberland snubnose darter Etheostoma simoterum atripinne and the Tennessee snubnose darter Etheostoma simoterum simoterum. The historical and current range of E. simoterum atripinne includes the Lower Tennessee River drainage unit and the Cumberland River drainage unit. The historical range of E. simoterum simoterum includes the Lower and Upper Tennessee River units, and it has been introduced into both the Licking Big Sandy Creek River unit and the Kanawha-New-Guyandotte-Little Kanawha River unit. Intergradation between the two subspecies occurs in the Lower Tennessee River unit. The mean standard length of Etheostoma simoterum is 45 mm, the reported average clutch size is 152, and the maximum age is less than 2 years. The snubnose darter inhabits riffles and rock-bottomed pools in streams with low turbidity. As of 2000, Etheostoma simoterum was listed as currently stable, meaning that it is widespread and not in need of any immediate conservation action.

Geographic Distribution

Etheostoma simoterum is native to the Tennessee River and Cumberland River drainages of Tennessee, Virginia, Kentucky, North Carolina, Georgia and Alabama. Warren et al. described the distribution of the freshwater fish native to the Southern United States by drainage basin. The historical range of Etheostoma simoterum simoterum includes the Upper and Lower Tennessee River drainage units. The historical range of Etheostoma simoterum atripinne includes the Lower Tennessee River and Cumberland River drainage units. Intergradation between the two subspecies occurs in the Lower Tennessee River unit. Etheostoma simoterum simoterum has been introduced into both the Licking Big Sandy and Kanawha-New-Guyandotte-Little Kanawha River units.

Ecology

Snubnose darters inhabit flowing bedrock or gravel-bottomed pools with moderate current in small to medium streams. They have been observed spawning in streams with water temperature ranging from 11 to 18 degrees Celsius. Etheostoma simoterum prefers a habitat with no vegetation or light algae. Snubnose darters are rarely found in water with high turbidity or where the substrate has been impacted by siltation, and human activities such as dam building or destruction of riparian buffers may lead to increased siltation thereby threatening darter populations.

Adults and juveniles are invertivorous. Examination of the stomach contents of 45 individuals broken into 4 size classes showed that midge larvae of the family Chironomidae makes up the bulk of the diet. Depending on size class, between 80% and 100% of examined stomachs contained midge larvae. Mayfly naiads, caddisfly larvae, copepods and cladocerans were also major contributors to overall stomach content. Consumption of food is highest in April, corresponding with the peak of spawning, while food consumption is much lower during months of temperature extremes and decreased activity such as January and July.

Large darters are susceptible to internal parasitism by flukes and nematodes. External parasites such as black spot disease caused by the fluke metacercariae and piscicolid leeches also affect snubnose darters.

Life History

Etheostoma simoterum reach sexual maturity at an age of 1 year and only survive for one breeding season, which occurs in April to early May. The darter breeds in bedrock pools and crevices with low siltation. The testes of breeding males gradually begin to increase in size in January and reach their peak in April. Males also begin to develop bright breeding colors in January, and by April all males are deep green to blue-green with red dorsal fins and red spots along the body. Breeding females do not change in color, but they may be slightly brighter in tone. Mature eggs are transparent, contain oil droplets and are an average of 1.2 mm in diameter. One study showed that the number of mature eggs per female ranges from 110 to 240 by April. Males court females by displaying erect fins and bright breeding colors. A female responds to this display by leading the male to an appropriate site for egg deposition such as a large stone or, more rarely, a gravel bed. The pair vibrates together, and after one or two eggs are released and fertilized by the male, the pair may move to another acceptable site to repeat the spawning act. However, snubnose darters are often promiscuous and may move on to find other mates instead. There is no parental care such as egg guarding after spawning. Snubnose darters survive to a maximum age of 18 months.

Current Management

Etheostoma simoterum is listed as currently stable, which Warren et al. define as “a species or subspecies whose distribution is widespread and stable or a species or subspecies that may have declined in portions of its range but is not in need of immediate conservation management actions.” Based on certain life history parameters, the American Fisheries Society lists Etheostoma simoterum as highly resilient with low vulnerability.

Habitat degradation and fragmentation are generally to blame for the decline of native fish in the southern United States. While Etheostoma simoterum is currently listed as stable, continued human population growth will lead to increased demands on natural resources and even greater challenges for species in the region. Stream channelization, sedimentation and impoundment, which are often the major threats to species’ viability, will likely increase as the human demand for land, water, and energy increases with population growth. Because the range of Etheostoma simoterum is isolated to only five drainage basins in a single region, even localized habitat destruction could severely threaten the viability of the species. Unfortunately, all of the states in which Etheostoma simoterum exists are currently listed in the “extreme risk” to ecosystems category by a national assessment based on the level of developmental pressure and the number of currently threatened species and ecosystems.

Certain characteristics of a species can make it disproportionately more susceptible to human threats. Studies have shown, for example, that species such as Etheostoma simoterum who specialize in benthic habitats in small to medium-sized rivers are more likely to be threatened by human activities.

Another detriment to fish in the southern United States is that the watersheds that support the greatest numbers of species are largely associated with privately owned land. Therefore, the vast majority of fish species in the southern states do not inhabit waters protected by federal ownership.

Management Recommendations

Because Etheostoma simoterum is not currently at high risk for extinction, it does not need to be considered a top priority for focused conservation efforts. However, taking a more holistic watershed approach to management may protect Etheostoma simoterum from future threat.

References

• Froese, Rainer. 2010. Etheostoma simoterum. http://www.fishbase.org/Summary/SpeciesSummary.php?ID=3466. (Accessed: November 20, 2011).
• Fuller, Pam, and Matt Neilson. 2011. ‘’Etheostoma simoterum’’. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.

http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=817 RevisionDate: 8/5/2011.

• Heins, David C. 2001. Variation in Clutch Size and Ovum Size of the Snubnose Darter, Etheostoma simoterum (Cope), from Two Populations in Tennessee. The American Midland Naturalist 145: 74-79.
• Hulsey, Darrin. Hulsey Lab Fish List. http://www.bio.utk.edu/hulseylab/Fishlist.html. (Accessed: November 20, 2011.)
• NatureServe. 2008. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, Virginia. Available at http://www.tnfish.org/SpeciesFishInformation_TWRA/Research/SnubnoseDarterEtheostomaSimoterum_NatureServeExplorer.pdf. (Accessed: November 20, 2011).
• Page, Lawrence M., and Richard L. Mayden. 1981. The Life History of the Tennessee Snubnose Darter, Etheostoma simoterum, in Brush Creek, Tennessee. Illinois Natural History Survey: Biological Notes 117: 1-11. http://www.archive.org/stream/lifehistoryoften117page#page/n3/mode/2up. (Accessed: November 20, 2011).
• Paine, M.D. 1990. Life history tactics of darters (Percidae: Etheostomatiini) and their relationship with body size, reproductive behaviour, latitude and rarity. Journal of Fish Biology 37: 473-488.
• Porterfield, Jean C. 1998. Spawning behavior of snubnose darters (Percidae) in natural and laboratory environments. Environmental Biology of Fishes 53: 413-419.
• Warren, Melvin L., Brooks M. Burr, Stephen J. Walsh, Henry L. Bart, Jr., Robert C. Cashner, David A. Etnier, Byron J. Freeman, Bernard R Kuhajda, Richard L. Mayden, Henry W. Robison, Stephen T. Ross, and Wayne C. Starnes. 2000. Diversity, Distribution, and Conservation Status of the Native Freshwater Fishes of the Southern United States. Fisheries 25: 7-31.