Stone darter

Stone darter
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Percidae
Genus:	Etheostoma
Species:	E. derivativum
Binomial name
Etheostoma derivativum Page, Hardman & Near, 2003[2]

The Stone darter,^[3] Etheostoma derivativum, is found mostly in the Cumberland River drainage. It is one of the 324 fish species found in Tennessee.^[4]

Introduction

The Stone Darter (Etheostoma derivativum) is a Barcheek Darter found in the Cumberland River drainage of TN. This paper seeks to describe the species and its ecological context while providing insight to potential management of the species. The species is locally common in areas in North-central Tennessee, specifically the West Fork Stones River. It is also found in Southern parts of Kentucky. Little work has been done on the species in terms of ecology. Work has been completed on the sister species Etheostoma virgatum from which the Stone Darter was originally described as a separate species. Also, descriptions of life history have been completed on the Striped Darter (E. virgatum) that are very similar to the Stone Darter and caused the belief that the two were one species. It is important to manage this species because it is a branch in the evolutionary tree within Etheostoma. This suggests that the genus is adapting to different habitats and genetic drift is occurring in great enough proportions to cause the creation of a new species. In order to protect the evolutionary integrity of the species, we must manage the areas that they inhabit so that humans and invasive species have as little impact as possible. Currently, there is no management scheme in progress and the abundance of the species is large but it may not stay the same in the future. Recommendations to protect the species are made below along with general descriptions of their geographic distribution, ecology, and life history.

Geographic Distribution of Species

The Stone Darter is found within the lower Cumberland River drainage, Southern Kentucky, and North-Central Tennessee. Specimens have been collected in Todd and Logan counties in Kentucky and in the West Fork Stones River in Tennessee.^[2] Since the fish is found in the West Fork Stones River, it was given the common name, Stone Darter. Collections were also made in White Creek, Marrowbone Creek, Sycamore Creek, Louise Creek, Harpeth River, and Red River. It is native to these waters and is found year round.^[5] The distribution is very small because this species has only just been recognized as a divergent species from Etheostoma virgatum in the past 10 years. The stone darter inhabits shallow pools, the bases and margins of riffles, and/or the margins of rocky bands over gravel and sand with slab rocks present.^[6] Within the Cumberland River system, species in the subgenus Catonotus are separated and live in one-species segments which create an almost totally nonoverlapping mosaic in the Cumberland, Tennessee, and Green River systems.^[7] This small range can be heavily impacted by humans if it is not carefully managed. Disturbances like dams, pollution, and invasive species could potentially impact the distribution of the Stone Darter in a very negative way.

Ecology

Little work has been done on the ecology of the Stone Darter itself but some research has been completed for other darters within the Catonotus subgenus. A study of the teardrop darter found that its diet consisted mainly on cladocerans, chironomids, and copepods.^[8] Authors of this study noted that the major food items ingested by the teardrop darter were similar to those reported for other Catonotus species. Feeding activity in barcheek darters is greatest prior to the spawning season. The ecological position of darters is in large measure determined by their carnivorous diet, small body size, and short life span. Possible predators of the stone darter include the Grass Pickeral (Esox americanus), Banded Sculpin (Cottus carolinae), Water Snakes (Natrix spp.), and the Common Snapping Turtle (Chelydra serpentina). Avian predators include the Belted Kingfisher and the Little Green Heron.^[8] Habitat includes rocky pools of creeks and small to medium rivers;^[9] small bedrock creeks (under flat rocks), gravel bottom pools and gentle riffles of larger streams (small to medium rivers). In larger streams, this darter often is associated with emergent vegetation or occurs under tree roots or undercut banks; it also occurs in slower riffles and gravel pools with no cover.^[10] Habitat destruction can easily reduce the species abundance if the human population continues to encroach on native habitat of this species

Life History

The life histories of those darter species within the subgenus Catonotus have similar spawning behaviors. They spawn in shallow pools with little or no current and little body contact between the mates. Adult males occupy territories beneath stones where the eggs are attached to the underside of a covering rock. Females invert and deposit eggs on the ceiling and occasionally the guardian male will invert to a head-to-tail position and fertilize the eggs.^[11] Other reproductive characteristics have not been completed on the Stone Darter so we will use another example of a Catonotus darter, The Duskytail Darter, as a substitute. Males and females reach sexual maturity at one year of age. The adults generally live 12–24 months. Mean clutch size was 27 with females producing multiple clutches. Spawning occurred beneath slab-shaped stones from late April–June at water temperatures from 17-24 C.^[12] We can assume, for the purpose of this paper, that the Stone Darter has a similar life history to other darters within the subgenus Catonotus. It is important to keep the habitat of these darters pristine because even slight changes in water quality and habitat can have profound effects on their reproduction and life history.

Current Management

The Stone darter is described as a species of Least Concern by the IUCN red list. This means that the species does not qualify for any of the other designations because it is widespread and abundant. The justification for this assessment is as follows: despite the somewhat small extent of occurrence, listed as Least Concern in view of the substantial number of subpopulations, apparently large population size, apparently stable trend, and lack of major threats.^[13] Therefore, there is currently no management being done specifically for this species. However, managers of the Cumberland River system recognize that there are endemic species in the area and are managing the habitat to effectively protect them. The stone darter is under that umbrella of protection and management. Biological declines of the species are going to be most pronounced in areas where hybridization might be occurring. This hybridization causes further mixture of genes and a deviance from the Stone Darter’s genetic scheme which in the long run causes population levels and genetic integrity to decrease drastically. It is hard to manage against hybridization but much easier to influence decisions that people make when coming into contact with the Stone Darter. Education is an important way to tell people of their native species and get them to start caring for the fish and wildlife that they have in their area.

Management Recommendations

In order to manage the Stone Darter effectively, estimates of population sizes and abundance of species across their range need to be performed. This will give managers a greater understanding of how many Stone Darters there are and with what importance they should be given in their ecosystems. Also, further information should be collected on their life history and ecology so that managers can take into consideration biological factors which might have effects when making decisions. At the current time, the similarities between the Stone Darter and its Catonotus relatives are sufficient for making decisions but when the data is more fine-tuned to a particular species, decisions can have a better impact for the species in question. Also, education must be a key part of the future of this species. It is vital to inform the public of this endemic species so that they can take care of it when they interact with it and its environment. Once further studies have been completed, it will be acceptable to bring the species into the lab and study it more closely. In order to collect Stone Darter specimens, electroshockers or seines would be most effective due to their tendency to be found in hard to reach places or vegetation. It would be important to scout a stream for areas where the Stone Darter would most likely be found prior to going out and collecting them. One must look for the gravel bottom pools, gentle riffles, emergent vegetation, tree roots, and undercut banks. Sampling studies would further add to the data bank regarding population size. The Red River watershed in Tennessee would be a potential watershed to set aside for protection of the Stone Darter should the need arise.

References