Percina squamata

Introduction

The species of darter being described on this page is Percina squamata (common name: olive darter). It is one of the 324 fish species found in Tennessee[11]. A monitoring plan of the olive darter will be discussed, as well as geographical range, ecology, life history and current management. Their geographic range is dispersed among headwaters of the Tennessee River system from the Holston River system (Watauga River) downstream as far as the Hiwassee River system, including the Emory River, in North Carolina, Tennessee, and Georgia; and the middle Cumberland River drainage below the falls, primarily in the Rockcastle River and Big South Fork, in Kentucky and Tennessee [4]. The olive darter is strictly an Insectivorous darter growing up to 5 inches in length and only living for up to 4 years. Female maturity is reached at 2 years old and they have a brood size of 1,500 in order to make up for the lack of a brood guarder. Eggs are dispersed out in the open and then fall down into rock-gravel [6]. The olive darter depends on good water quality and fast-water habitats in upland streams. Impoundments have reduced available habitat for the olive darter, and remaining free-flowing mountain streams are vulnerable to degradation by excessive inputs of silt and sediment. Conservation of the olive darter will require eliminating stream pollution.

Geographic distribution

The olive darter is restricted to small to medium sized streams and rivers in the upper-most portions of the Tennessee River and Cumberland River systems in Tennessee, Kentucky, North Carolina, and Georgia. In Georgia, Percina squamata is only known from the Toccoa and Little Tennessee River systems [4]. Within the Cumberland and Tennessee River systems this species occurs in Big South Fork, Coopers Creek, Betty’s Creek Rockcastle River [6], Holston River (Watauga River), and Hiawassee River [7]. Percina squamata relies on good water quality and fast-water habitats in order to survive. The largest tributaries of the Toccoa and Nottely rivers in Georgia are very similar, having clear, cold water and rocky substrates [2], ideal conditions for the olive darter.

Ecology

Olive darters are invertivores/insectivores [7] primarily feeding on benthic aquatic insects, including caddisflies and mayflies [4]. In general, darters feed opportunistically on immature insects; few taxa are consumed in greater proportions than they were found in the environment [1]. This species of darter, like many others, inhabits high-gradient streams with moderate to torrential current over rubble and boulders, deeper downstream portions of gravel riffles in streams of moderate gradient, and sometimes shallow pools with gravel or rock bottoms [7]. Being very habitat specific, it is necessary for humans to have as little influence on the streams that this species inhabits. Human activities, particularly habitat destruction and species introductions, are resulting in increased homogenization of once unique biogeographic regions [9]. Failure of Best Management Practices (BMPs) for forestry and agriculture, failure to control soil erosion from construction sites and bridge crossings, and increased stormwater runoff from developing urban and industrial areas have degraded the stream quality and pose a significant threat to the olive darters [4]. Runoff and siltation caused by increasing habitat destruction raises the temperature of the water in many streams causing a change in the microclimate needed for the inhabitants of olive darters. This leads to loss of population.

Life History

The maximum lifespan of the olive darter is around four years with an average lifespan of three years. This darter reaches sexual maturity halfway through its life at two years [6]. Reproductive condition of adults and the timing of young-of-year recruitment indicate a May–July spawning season [4]. They spawn in rock-gravel shoals [6] where the female will drop her eggs and the males fertilize the eggs. This reproductive strategy allows for protection of the brood without the use of a brood guarder [6]. Nearly 1,500 eggs are in a single brood [6] allowing for a higher chance of survival. This is a common reproductive strategy for many darters. At full maturity the male will reach about 5 cm [6] and the female will only be slightly smaller.

Current Management

Currently P. squamata is a vulnerable species with a rank of 1 meaning that its vulnerability is caused by present or threatened destruction, modification, or reduction of a taxon’s habitat or range [10]. Streams are a very dynamic ecosystem that can be thrown off by even the slightest change to its environment. Humans are largely and almost fully to blame for the increasing loss of the olive darter. The lacks of Best Management Practices as well as construction of dams, road crossings and weirs are anthropogenic barriers [3] that are leading to the destruction of stream habitats. The presence of these barriers causes stream fragmentation and loss of the natural flow of the stream. The stream above the dam oftentimes becomes a lake and is quickly sediment, while the streams below the dam become dry stream beds [8]. If below the dam doesn’t become a dry stream bed, chances are that it will become genetically isolated as well as cut off from spawning grounds, food, protection and required water flow velocity. Though not human caused, olive darter habitat is also becoming threatened due to the hemlock woolly adelgid [4]. Hemlocks are a shade tolerant species that usually grow in moist areas, such as along streamside riparian zones. The adelgid kills a vast amount of Eastern hemlock trees (Tsuga canadensis) leading to siltation.

Management Recommendations

Human activities related to land development on a large scale are continually altering the habitat of the olive darter [5]. In order to be able to better manage the olive darter for the future, better BMP’s will be needed. To be able to know what type of practices should take place, more research and information on these darters will need to be gathered. Snorkeling to compare and observe habitat health. When waters are too shallow to snorkel, electrofishing will be the method of sampling. Sampling should take place monthly and at least in 20 locations in multiple streams throughout the olive darters native region. Sampled streams would include ones that have had construction nearby and ones that have had little to no anthropogenic factors causing possible loss of population. If we want to see the olive darter survive, we will have to eliminate sediment runoff form land-disturbing activities such as roadway and housing construction, maintain forested buffers along stream banks, eliminate inputs of contaminants such as fertilizers and pesticides, and maintaining natural patters of streamflow [4]. For the loss of hemlock trees, treatment can be provided and more trees should be planted. We also should set aside some public land for the conservation and continued existence of the olive darter.

References

1.Gray, Ellen Van Snik, J.M. Boltz, K.A. Kellogg & J.R. Stauffer Jr. “Food Resource Partitioning by Nine Sympatric Darter Species.” Transactions of the American Fisheries Society (1997):126:5, 822-840.

2.Hitch, Robert K. & Etnier, David A. “Fishes of the Hiwassee River System-Ecological and Taxonomic Considerations”. (1974): 49:3, 81-112.

3.Roberts, James H., Angermeier, Paul L. & Hallerman, Eric M. “Distance, dams and drift: what structures populations of an endangered, benthic stream fish?” Freshwater Biology (2013): 58, 2050-2064.

4.Freeman, Byron J. & Albanese B. (1999-2011). http://www.georgiawildlife.com/SpeciesInfo/Fish.

5.Pratt, Anne E. & Lauer, Thomas E. “Habitat Use and Separation among Congeneric Darter Species.” Transactions of the American Fisheries Society (2013): 142:2, 568-577.

6.http://www.globalspecies.org/ntaxa/661223#cite_1

7.Nature Serve. (2009). http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Percina+squamata+.

8.Johnson. R., Haight, L.T., & Simpson. J.M. “Endangered Species vs. Endangered Habitats: A Concept.” 68-80.

9.Scott, Mark C. & Helfman, Gene S. “Native Invasions, Homogenization, and the Mismeasure of the Integrity of Fish Assemblages.” Fisheries (2001): 26:11.

10.Jelks, Howard L., Walsh, Stephen J., et al. “Conservation Status of Imperiled North American Freshwater and Diadromous Fishes.” Fisheries (2008): 33:8.

11. http://www.bio.utk.edu/hulseylab/Fishlist.html