Goldline Darter

Goldline Darter The goldline darter (Percina aurolineata) is a threatened fish native only to the Cahaba River watershed in Alabama in Bibb, Jefferson, and Shelby Counties and the Coosawattee River watershed in Georgia. Percina means "small perch" and aurolineata means "gold lined." Darters are a very diverse group of fish (about 230 species) that are only found in North America (mostly in the southeastern United States). Darters are generally small (few species exceed three inches in length) and live on the bottom of shallow sections of streams and rivers. Males of many darter species develop bright colors on their bodies to attract females during the spring mating season.

The goldline darter was described by ichthyologists Royal D. Suttkus and John S. Ramsey in 1967. It attains a maximum length of about 3 inches (~7.5 centimeters). It has eight or nine connected rounded blotches on each side and a dark broken stripe on each side of its back. It is somewhat similar in appearance to the closely related blackbanded darter (Percina nigrofasciata), which is very common in the Cahaba. The goldline darter has round blotches on its side with a thin broken stripe above, whereas the blackbanded darter has tall irregular vertical stripes on its side and does not have a stripe on each side of its back.

In Alabama, the goldline darter occurs in the Cahaba River proper, the lower Little Cahaba River, Shultz Creek, and Shades Creek. Previously thought to be extirpated in the upper Cahaba watershed, specimens were collected near Helena (Jefferson and Shelby Counties) in 2018 and 2021. It is unclear whether this discovery represents a recent increase in the species' range or a previously undiscovered subpopulation. Many ichthyologists believe that the goldline darter once occurred throughout the entire Mobile basin watershed but was extirpated over the centuries as a result of habitat degradation. The two isolated populations in the Cahaba and Coosawattee appear to have exchanged genes with each other in the recent past, suggesting a once-continuous distribution. No other isolated populations have been found outside the Cahaba and Coosawattee, however. Although the true historic range of this species is unknown, the goldline darter almost certainly had a more extensive distribution in the past.

Goldline darters usually occupy riffle habitats (shallow areas of streams with swift water) and runs (deep areas with swift water) of large streams and rivers and are often found living among cobbles and clusters of aquatic plants such riverweed (Podostemum ceratophyllum) or water willow (Justicia americana). They eat aquatic insects, apparently relying heavily on midge larvae.

Biologists know relatively little about the goldline darter's life cycle but have found evidence suggesting that they spawn in the spring. Males become territorial during the spawning season and chase other males away. They then attempt to impress potential mates by swimming near them and raising their dark-colored dorsal fins, like how a male peacock uses its plumage. A female impressed by a male will select a spawning site in sand or gravel on the bottom of the stream and lower herself against the substrate. The male then mounts the female and clutches her with his fins. The female releases eggs into the substrate and the male releases milt (sperm) on top of them. Both parents then leave the spawning site and provide no care for their young. Fertilized eggs are very small (about 0.07 inches or ~.2 centimeters wide) and are colorless or translucent orange with dark speckles. Newly hatched larvae are about 0.25 inches (~.6 centimeters) long. Larvae typically obtain pigmentation characteristic of adults at 0.75 inches (~2 centimeters) long.

Because of the goldline darter's specific habitat requirements, it is extremely vulnerable to habitat degradation. Like many darters, goldline darters require clean water with abundant cobbles and gravel. Areas that have undergone deforestation are more susceptible to erosion, which washes silt into rivers. This silt covers the rocks that goldline darters rely on for shelter and food (rocks and the crevices created by them provide habitat for many of the aquatic insects that darters eat). Thus, habitat loss is likely the largest threat to the continued existence of this species in Alabama. Additionally, cattle that enter areas near streams often trample or consume the bank-side vegetation, causing severe erosion and sedimentation that buries the rocky substrate. Negative changes to water quality are also a source of concern for this species. The Cahaba historically received large amounts of untreated wastewater when municipal input exceeded the processing capacity of treatment plants. Strip mining and methane extraction (lucrative enterprises in central Alabama given its large coal deposits) have also caused degraded water quality in the Cahaba and created concerns for its species. Water quality issues can result in inputs of chemicals toxic to aquatic life and drops in the level of dissolved oxygen, which makes it very difficult for pollution-sensitive fish to survive. These concerns prompted the U.S. Fish and Wildlife Service to list the goldline darter as federally threatened in 1992. This legal designation indicates that a species is at risk of becoming endangered and provides special protections above those covered by normal non-game laws.

Further conservation actions will likely focus on mitigating sediment deposits in the Cahaba, ensuring adequate water quality, and surveying the river to monitor the status of its goldline darter population. Habitat acquisition and preservation in surrounding areas can help prevent deforestation of the watershed, which can in turn prevent excess sediment from entering the Cahaba. Exclusion of cattle from goldline darter habitat and adjacent stream banks can help ensure that streams have suitable habitat for these sensitive, bottom-dwelling fish. Fish ecologists also recommend maintaining river connections between isolated subpopulations so that they can continue to interbreed.

Further Reading

  • Albanese, Brett, Thomas Litts, Mieko Camp, and Deborah Weiler. “Using Occupancy and Species Distribution Models to Assess the Conservation Status and Habitat Use of the Goldline Darter (Percina aurolineata) in Georgia, USA.” Ecology of Freshwater Fish 23 (July 2014): 347-359.
  • Rakes, Patrick L., and J.R. Shute. “Developing Propagation and Culture Protocols for the Cahaba Shiner, Notropis cahabae, and the Goldline Darter, Percina aurolineata.” American Currents 28 (Fall 2002): 11-28.
  • U.S. Fish and Wildlife Service. Endangered and Threatened Wildlife and Plants; Threatened Status for Two Fish, the goldline darter (Percina aurolineata) and Blue Shiner (Cyprinella caerulea). Federal Register 57(78): 14786-14790.

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