Biologists Hope to Solve the Robust Redhorse Mystery

RALEIGH, N.C. (March 16) – Deep within the murky waters of the Yadkin/PeeDee River lurks a mystery. The robust redhorse, seen only once in North Carolina since 1870, resurfaced in the PeeDee River four years ago much to the surprise and delight of fisheries biologists, many of whom had only heard or seen pictures of the extremely rare fish.

Wayne Starnes, curator of fishes at the N.C. Museum of Natural Sciences, holds a robust redhorse found in the PeeDee River in May 2001. Media: A hi-res version of this image may be downloaded here. Photo credit: Progress Energy

This spring, biologists with the N.C. Wildlife Resources Commission, in collaboration with other cooperators, are sampling the Yadkin/PeeDee River to determine if the female specimen found below Blewett Falls Reservoir in 2000 and a second female found nearby the following spring, are part of a larger population in North Carolina.

Collecting the robust redhorse is difficult. Biologists believe the secretive fish spends most of its life in large rivers where it inhabits deep, snag-filled pools with moderate water flows.

Using non-lethal electrofishing techniques, biologists hope to collect several specimens while the fish are in shallower water, spawning on gravel beds. Radio transmitters inserted into the fish will allow biologists to track the fish’s movements and help them understand the fish’s preferred habitats. They also hope the tagged fish will lead them to possible locations of other robust redhorse populations.

Biologists will use captured specimens to help them understand the species’ life history as well as assess the status of robust redhorse populations in the Yadkin/PeeDee River, said Ryan Heise, the Commission’s aquatic nongame biologist for the Yadkin/PeeDee River.

“By removing scales from the side of a fish, we can estimate the age of the fish. If young fish and old fish are caught, it means the fish are reproducing successfully,” Heise said. “This age information, combined with data on length and weight, can tell us how fast the fish grow and help us estimate a maximum size and age.”

Tissue samples taken from captured specimens can reveal genetic information that may help biologists determine how closely Yadkin/PeeDee River robust redhorse populations are related to robust redhorse populations in other southeastern rivers.

Biologists believe the robust redhorse, first discovered in the Yadkin River in 1870, was once common in the river and may have been present as far upstream as Winston-Salem. However, the species remained a mystery, unknown to biologists until two individuals were captured nearly 100 years later. In 1980, one robust redhorse was captured in the Savannah River in Georgia. In 1985, another robust redhorse was captured in the Pee Dee River in North Carolina. The identification of these redhorses was not clear until more specimens were collected in 1991 in Georgia. While sightings have been sporadic, wild populations exist in several rivers in South Carolina, Georgia and North Carolina.

The reasons for the robust redhorse’s decline are due to many factors. Sedimentation from development, altered river flows and blocked passages from dam constructions, as well as predation from transplanted, large catfish species have all played a part in the robust redhorse’s population decline.

“In order to spawn, the robust redhorse requires clean, silt-free gravel on river bottoms. Unfortunately, large-scale land clearing related to agriculture and urbanization has led to massive sedimentation in rivers and streams while dam construction has impounded once suitable spawning sites and eliminated access to others,” Heise said. “Also, the robust redhorse has fallen victim to introduced predatory fishes, such as the flathead and blue catfish, which will eat virtually anything, including the redhorse itself and freshwater mollusks – a food source for the redhorse.”

The robust redhorse, a large, long-lived member of the redhorse sucker family, can reach 30 inches in length and weigh up to 17 pounds. Its thick, robust body with rose-colored fins and a fleshy lower lip give the fish its colorful name.

While biologists have learned much about the robust redhorse since its discovery, they still have many questions about its habitat, life history and survival for the future. The two specimens collected in 2000 and 2001 were exciting discoveries and represented a significant development for members of the Robust Redhorse Conservation Committee (RRCC), which was formed in 1995 to improve the status of the robust redhorse throughout its former range.

The RRCC is composed of 13 private and public entities including hydro-power interests, conservation groups, the U.S. Fish and Wildlife Service, the Wildlife Commission and other state/federal agencies in Georgia and South Carolina. Members of the committee are tasked with determining the biological reasons behind the fish’s decline and restoring the species to a sustainable level.

Research and management for the robust redhorse in North Carolina are funded through the Nongame and Endangered Wildlife Fund, which is the primary source of state funds for the Commission’s Faunal Diversity and Aquatic Nongame programs. The Commission uses this fund, which supports non-game species research and management, to generate matching money for federal grants.

You can support this effort as well as other nongame species research and management projects in North Carolina through the Tax Check-off for Nongame and Endangered Wildlife. This tax check-off allows taxpayers to designate part or all of their state tax refunds to this fund. Since 1984, taxpayers have given $6,933,382 for wildlife conservation through this funding mechanism.

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