Laurel Dace (Chrosomus saylori) - Hannah Lee

Laurel Dace

Chrosomus saylori

What are Laurel Dace?

Taxonomy

Categorized under the Cyprinidae family, Laurel Dace are small fish endemic to the Tennessee River Basin. Their subfamily is Leuciscinae.

Morphology

Laurel Dace are known to reach approximately 6.2 centimeters. They are most recognized through their distinct coloring. Both males and females have a silvery body, painted with two continuous black lateral stripes and a red belly. During mating season, males experience increased pigmentation; their bellies turn intense scarlet and their stripes become rich black. Their fins also develop a yellow and orange hue.

Apart from their color, the gender of Laurel Dace can be identified through the shape of their fins. Males have rounded pectoral fins and females have pectoral pointed fins.

Laurel Dace (A) compared to closely related Clinch Dace (B).
The only noticeable morphological difference is the intensity of pigmentation
and the top lateral stripe. The Laurel Dace's stripe does not
fully connect to the caudal fine like the Clinch Dace's.

Laurel Dace also has distinct morphological feeding traits. Strong characteristics include a large mouth, short digestive tract, and low number of pharyngeal teeth. These traits suggest that Laurel Dace consume macroinvertebrates, algae, and other plant materials. Based on a study on the closely related Clinch Dace (Chrosomus sp. cf. saylori), it is also assumed that Laurel Dace primarily drift feed.

A typical Dace stream is cold, slow
moving, and vulnerable
because of its small size.

Habitat

Laurel Dace are native to the Tennessee River Basin. They commonly reside in the headwater tributaries of Walden Ridge, which is near the eastern edge of the Cumberland Plateau. They are historically found in seven different streams which are a part of three independent water systems: the Soddy Creek System, Sale Creek System, and Piney River System. They are freshwater fish, surrounded by vegetation such as mountain laurel, rhododendron, pines, and eastern hemlock. They are normally found in cold, clear pools or slow running bodies of water from undercut banks. The maximum water temperature of Laurel Dace is 26°C (78.8°F). Within these bodies of water, there are three main substrates: cobble, rubble, and boulders.

How has their geographical distribution/population changed?

Distribution

The most noticeable change in Laurel Dace distribution is their shrinking range. The species is historically found in seven streams along the Tennessee River Basin, but it is not only found in six. These seven streams can be categorized into three different water systems. The Soddy Creek System is an independent stream and is the most southern habitat unit. The Sale Creek System is composed of Rock Creek, Cupp Creek and Roaring Creek. These creeks also have their own subsections. The Piney River System, the most north Laurel Dace habitat units, include Youngs Creek, Bumbee Creek, and Moccasin Creek.

In 1976, Laurel Dace were found in all three systems. By 1991, all samplings and efforts to collect Laurel Dace in Laurel Branch (which is a part of Rock Creek) failed. The continued absence of Laurel Dace in Laurel Branch has led specialists to believe the species were extirpated from one of their primary locations.

There is also room to believe Laurel Dace will be extirpated from other locations as well. In 2004, only one juvenile Laurel Dace was found in Soddy Creek. Laurel Dace have also not been successfully collected in Cupp Creek since 1996.

Population

There is no conclusive population estimates available for Laurel Dace because of private land holdings. Private land holdings restrict surveyors and their ability to investigate and observe streams such as Bumbee Creek. While there has not been updated information on the state of species survival in the Soddy Creek System and Sale Creek System, many specialists believe the Laurel Dace are at high risk of extirpation.

Are Laurel Dace endangered?

On August 9^th, 2011, the U.S. Fish and Wildlife Service listed Laurel Dace as endangered species under the Endangered Species Act of 1973. The following year, they designated critical habitat to Laurel Dace.

Under the Tennessee Wildlife Resources Agency, Laurel Dace are listed with a recovery priority number of 5. This listing means that Laurel Dace have a high degree of threat and low recovery potential.

Why are Laurel Dace endangered?

Inherent Species Characteristics

There are several inherent species characteristics that greatly limit Laurel Dace survival. Laurel Dace also naturally have small population and geographical distribution. The species’ small population and range make is more susceptible to loss in genetic variation due to genetic drift. Common effects of this characteristic include inbreeding depression and a narrow range of physical tolerance. The Laurel Dace’s inability to quickly adapt to environmental changes makes it vulnerable and consequently, reduces the fitness of the species.

External Pressures and Influencers

Along with the species’ natural characteristics, external factors also contribute to its potential extinction. The most obvious and prevalent threat to Laurel Dace is the use of surrounding land for human activities. The implementation of roads, residential areas, and farm land in (and near) habitat tributaries has accelerated the introduction of siltation and sedimentation, increase in water temperature, and curtailment of riparian vegetation. Changes in silt and sediment structures in Laurel Dace habitats affect the species’ reproduction, feeding, and physiology. Siltation and sedimentation directly affects visibility, which reduces visual cues in mating and predation. It can also clog gills, which significantly decreases species fitness. The increase in water temperature through anthropogenic climate change results in the decrease of dissolved oxygen, which is essential to survival. Removing surrounding vegetation such as eastern hemlock, mountain laurel, and pines affects light filtration, water temperature, and stream flow.

In addition to changes in the structural format of Laurel Dace habitats, nonnative species may have contributed the population’s decline. The introduction of nonnative species such as the Green Sunfish, Bluegill, and Largemouth Bass has potentially affected Laurel Dace through predation and resource competition. While there is no conclusive evidence that these species have directly influenced the trajectory of Laurel Dace survival, studies have observed a negative correlation between nonnative species and Laurel Dace populations.

Another factor is the inadequacy of existing laws and regulations. Under the Tennessee Nongame and Endangered or Threatened Wildlife Species Conservation Act of 1974, Laurel Dace are offered some protection. The Clean Water Act and the Tennessee Water Quality Control Act aim to improve water quality and limit habitat degradation. Despite these laws, sedimentation continues to be problematic. Evidence of the inadequacy of current policies can be seen through the Tennessee Department of Environment and Conservation’s decision to put Laurel Branch and Soddy Creek on a list of streams affected by non-irrigated crop production sedimentation.

What are the main goals of this species’ recovery plan?

In the federal recovery plan for Laurel Dace, efforts aim to “ensure viable populations exist in all streams where the species is known to have occurred historically” through the conservation of existing populations and restoration and protection of habitats. Historical locations include Piney River System (Bumbee, Moccasin, and Youngs Creeks), Soddy Creek System, and Sale Creek System (Cupp Creek, Laurel and Horn Branch).

Enforcing current laws, policies, and regulations to protect water quality is also vital to the survival of Laurel Dace. The recovery plan will also work with Tennessee conservation organization partners to inform citizens about Laurel Dace. In these efforts, the U.S. Fish and Wildlife Service will educate the public on how to make changes to benefit the lives of endangered aquatic species. They plan on encouraging agricultural, forestry, and construction businesses to optimize their practices for the sustainability suitable habitats. Since there is currently no detailed life history report on Laurel Dace, the Service looks to conduct extensive research on a captive population. A detailed life history report would allow the Service to better understand (their environmental stressors and threats) and support the existing Laurel Dace.

The Laurel Dace Recovery Plan can be outlined through eight points:

1. Protect Laurel Dace habitat via land acquisition, conservation easements, or other mechanisms to reduce threats to instream and riparian habitat.
2. Map suitable habitat in streams where Laurel Dace are extant or occurred historically, identify streams on Walden Ridge with suitable habitat but no known records of occurrence, and periodically conduct surveys for previously undetected populations and to determine whether populations are still extant in occupied streams.
3. Develop a program to monitor trends in distribution and demographic structure of Laurel Dace populations, habitat conditions, and land use in catchments of Laurel Dace streams.
4. Conduct baseline genetic analysis and establish protocol for periodic monitoring to detect trends in genetic variation and structure among populations.
5. Determine life history, interspecies interactions, and tolerance to environmental stressors of the Laurel Dace, and conduct population viability analysis.
6. Evaluate stream crossings as fish passage barriers or nonpoint pollutant sources and reduce impact if necessary.
7. Establish protocols and plan for captive propagation to support research and reintroduction or augmentation.
8. Develop informational materials and conduct outreach to encourage public participation in Laurel Dace recovery effort.

The U.S. Fish and Wildlife service has estimated a necessary fund of $1,828,500 to downlist Laurel Dace from endangered to threatened.

What can we do to help Laurel Dace?

The endangerment of Laurel Dace is a highly specialized topic. There are currently no explicit programs dedicated to Laurel Dace (or explicit legislations). The best way to contribute is to donate to the U.S. Fish and Wildlife Service and specify which species fund you would like to support. 

Spreading awareness on endangered species such as the Laurel Dace is also important. Many endangered species are underrepresented in society; sharing information is vital to making a difference. Through the Southern Trout Magazine and Clinch Chronicle, the public is slowly being exposed to Dace populations.

References

George, Anna L., Kuhajda, Bernard R., and Neely, David A. Recovery Plan for the Laurel Dace

(Chrosomus saylori). Chattanooga: Tennessee Aquarium Conservation Institute, 2016.

“Laurel Dace.” Tennessee Aquarium, www.tnaqua.org/protecting-animals/laurel-dace.

Moore, Micheal. “Here Today, Gone Tomorrow.” Clinch Chronicle: Science for the

Conservation of the Clinch Dace, 11 February 2015, https://clinchchronicle.wordpress.com/2015/02/11/here-today-gone-today/. Accessed 5 March 2018.

Orth, Donald. Ontogenetic and Comparative Morphology of Clinch Dace (Chrosomus sp. cf.

saylori). Copeia, 31 December 2013.

Skelton, C. E. 1997. Status survey of the Laurel Dace (Phoxinus sp.) on Walden Ridge and

adjacent areas in East Tennessee. Final Report for the U.S. Fish and Wildlife Service, Contract No. 1448-0004-95-9121. 32 pp.

Skelton, C. E. 2001. New Dace of the Genus Phoxinus (Cyprinidae: Cypriniformes) from the

Tennessee River Drainage, Tennessee. Copeia 2001(1):118-128.