Splendid darter

Splendid darter
Conservation status
Least Concern  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Percidae
Genus:	Etheostoma
Species:	E. barrenense
Binomial name
Etheostoma barrenense Burr & Page, 1982

The splendid darter, Etheostoma barrenense, is a species of fish endemic to the Barren River system in south- central Kentucky and in north-central Tennessee.^[1] The Barren River is a system of the Ohio River drainage and this species is usually found in small rocky pools on the sides of creeks and rivers.^[2] It is one of the 324 fish species found in Tennessee.^[3]

The Splendid Darter is currently listed as a species that the state of Tennessee should be taking steps to protect. It, like many other darter species, inhabits a single small river system and exhibit specialized reproductive behaviors that are only supported by a particular type of environment.^[4] This small river system is vulnerable to even the slightest changes, be they natural or anthropogenic, putting inhabitants of the system at risk.^[4] The two most influential landscape features affecting the current distribution of E. barrenense are land use/land cover patterns and soil composition.^[1] As such, these two phenomena must be closely monitored in the following years in order to ensure the safety of the splendid darter and all other species found in the Barren River system.

The current existence and continuing development of dams in Tennessee is one of the most pressing issues affecting freshwater environments and preventing many species of fish from migrating properly.^[5] This occurrence, along with diminishing habitat size and the introduction of toxic waster (including chemical and physical substances) post great threats to countless animal species all over the world. By addressing these and other issues, and effectively managing our natural resources we can ensure that currently endangered species like Etheostoma barrenense never become extinct.

Geographic Distribution of Species

E. barrenense is found only in the Barren River system of southern central Kentucky and northern central Tennessee; this system is a part of the Ohio River drainage. The range of this species is between 5000 – 20,000 square kilometers which is relatively small.^[6] E. barrenense is not thought to have either spread or shrunk its distribution since it was described in 1982, but there is very little data on its dispersal and other movements; some larvae may drift along with the current, but ultimately, the species has remained in its small range.^[6] The Splendid Darter has a tendency to spend most of its life in deep, rocky pools and the riffles of small creeks and rivers as well as streams.^[7]

The geographic distribution of E. barrenense and other darter species is extremely important to the way the species passes on its genes to subsequent generations. Much of the isolation that remains between closely related species of darters is due to brilliant nuptial coloring and behavioral isolation, ensuring that mates of the same species are attracted to one another.^[8] Since many of these species live in sympatric populations, there must be a mechanism such as this, allowing the genes of different species to remain isolated. Without the occurrence of this phenomenon, the very genes which define the species could be compromised, endangering its existence.^[9]

Ecology

The splendid darter is a bentho-pelagic fish that occupies a freshwater habitat with a frequency of occurrence from 21 to 80.^[2] Research has not yet revealed the specific dieting habits, competitors or predators of E. barrenense, but studies of other darter species show that the splendid darter is likely insectivorous and at times consumed by larger predatory fish.^[10][11] These invertivorous fish spend most of their time feeding on the bottoms and sides of streams.^[6]

Most species of Etheostoma exhibit unique nuptial coloration and E. barrenense is no exception. It is thought that reproductive isolation and sexual selection between species maintain these diverse color patterns as these fish are often found in sympatric populations.^[6][12]

Life History

E. barrenense reaches sexual maturity at around one year, but the majority of breeding individuals sampled are between two and three years old.^[13] Typical mating pairs include a two-year-old female and a three-year-old male. Breeding occurs once a year, normally from March to June in Kentucky and March to May in Tennessee.^[6] The average life span of this species is only three years, so most individuals may breed once or twice before they die. No individuals have been known to live beyond three years, but it is possible that some may.^{[citation needed]}

Most species of Etheostoma exhibit unique nuptial coloration and E. barrenense is no exception. It is thought that reproductive isolation and sexual selection between species maintains these diverse color patterns as these fish are often found living in sympatry with closely related species.^[4] Breeding is an interesting phenomenon; males establish floating territories in deep pools and females approach these microhabitats where both fish will press against inclined stones in order to lay their eggs. Many eggs are laid at one time, but they are usually produced individually on separate, vertical rocks in slightly flowing currents. This dispersing of the eggs increases the chance of survival for at least a few of the E. barrenense offspring. The eggs are spherical, translucent and adhesive, providing them a greater opportunity to survive as they are attached to a vertical wall and often difficult to detect.^[13]

Current Management

On a conservation level, Etheostoma barrenense is considered secure using the NatureServe conservation status both nationally and globally, but vulnerable on a state scale in Tennessee.^[6] However, the International Union for the Conservation of Nature (IUCN) has not evaluated the conservation status of this species, so there is some debate surrounding just how threatened it may be.^[2] We have just cause to assume that for now, the species is stable.^[6][14] However, increasing anthropogenic change in the area may be leading to the future detriment of not only the splendid darter, but all other wildlife inhabiting this small ecosystem in the southeastern United States. E. barrenense is considered a species that warrants protection in Tennessee, but not throughout its range, so perhaps it is time to ensure that we are protecting its future.^[4]

Geographic extent, habitat specificity – the number of habitat types in which a species is known to exist – and local population size are good criterion to use as a basis for species rarity and according to these three dimensions, the splendid darter is extremely rare.^[12] This characteristic alone is enough to warrant protection of the species, yet there are no current management practices in place specific to the conservation of the splendid darter.^[14]

In addition to its rarity, several other factors have the potential to contribute to a decline in splendid darter abundance. These include, but are not limited to, hybridization with closely related species, habitat destruction or modification and the threat of invasive species. Perhaps there are no current threats impeding the survival of E. barrenense, but monitoring of this species will likely be necessary if we hope to ensure its future existence.

Management Recommendations

There are an estimated 10,000 individuals of Etheostoma barrenense across its native range in Kentucky and Tennessee.^[6] This number seems stable, but anthropogenic changes and potential hybridization are risks that cannot be ignored. For now, the splendid darter is safe, but close monitoring of the species is necessary if we hope to prevent future dwindling of these numbers. If a significant decrease is seen, we must then take steps to prevent a decline from occurring.

In order to monitor the species, it is recommended that sampling be done in both Kentucky and Tennessee at least once a year and in several different locations. We know that the splendid darter occupies many different streams and tributaries, so a solid random sampling from various areas will be necessary to properly assess and record the abundance of E. barrenense individuals each year. By using both seine and electroshock capture methods in each of the sampling areas, we can create a consistent and viable report of abundance, allowing us to monitor species numbers and be properly prepared if there is ever a drop in their numbers.

In the event that abundance does decrease, more drastic measures should be taken to ensure the existence of the splendid darter. A good way to prevent future harm to a declining species is to set aside specific areas to protect. This can be done by preventing fishing in a particular stream or pool, allowing the species living there to be largely undisturbed. This technique has been used in many cases and has been mostly effective, but other man-made disturbances, such as dams and bridges, can also effect the distribution and success of this species.

References

Wikispecies has information related to: Etheostoma barrenense

Wikimedia Commons has media related to Splendid darter.

Further reading

• Hopkins, Robert L.; Whiles, Matt R. (2011). "The importance of land use/land cover data in fish and mussel conservation planning". Annales de Limnologie 47 (3): 199–209. doi:10.1051/limn/2011026. 
• Page, Lawrence M.; Burr, Brooks M. (1991). A Field Guide to Freshwater Fishes: North America North of Mexico. Peterson Field Guides. Boston: Houghton Mifflin. ISBN 978-0-395-35307-3. 
• Warren, Melvin L.; Burr, Brooks M.; Walsh, Stephen J.; Bart, Henry L.; Cashner, Robert C.; Etnier, David A.; Freeman, Byron J.; Kuhajda, Bernard R.; Mayden, Richard L.; Robison, Henry W.; Ross, Stephen T.; Starnes, Wayne C. (2000). "Diversity, Distribution, and Conservation Status of the Native Freshwater Fishes of the Southern United States". Fisheries 25 (10): 7–31. doi:10.1577/1548-8446(2000)025<0007:DDACSO>2.0.CO;2. 
• Weddle, Gordon K.; Cone, David K. (1997). "Gyrodactylus rafinesqueii sp. n. (Monogenea) from Etheostoma rafinesquei (Percidae) in Kentucky, with a Review of the Taxonomy and Host Specificity of Species of Gyrodactylus from Etheostomatid Fishes in North America". Journal of the Helminthological Society of Washington 64 (1): 17–24. INIST:2631739.