Balcones Spike (Fusconaia iheringi)

Balcones Spike
Photo courtesy of Charles Randklev

Historically, freshwater mussels were collected commercially for food, pearls and button making.

Harvesting is now regulated, and the Balcones Spike, or Fusconaia iheringi, could soon be federally protected.

Protection Status

The Balcones Spike is currently a state-listed threatened species. However, it’s also currently under review for federal protection under the Endangered Species Act.

The Brazos River Authority’s Environmental Services Department regularly monitors different fish and wildlife species, including freshwater mussels, as a way of tracking the health of the Brazos River basin ecosystem.


Freshwater mussels are an indicator of a healthy aquatic system. They are filter feeders and thus contribute to water clarity and quality by removing plankton and pollutants from the water.

The sudden disappearance of mussels in an area not recently subject to prolonged drought often indicates water pollution problems.

Commercial harvesting is regulated by the Texas Parks and Wildlife Department and requires a license and annual reporting to the department.

Balcones Spike Distribution Map
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The Balcones Spike is most commonly observed in riffles and runs within streams and rivers, with sporadic observations in other habitats. Within the Brazos River basin, the Balcones Spike is currently known to reside in the Little River, San Gabriel River, and Brushy Creek.

Life Cycle

Like other native freshwater unionids, Balcones Spike parasitize on host fish during the larval stage, receiving nutrition and transport from the host until dropping off as fully developed juveniles, according to the Journal of the North American Benthological Society. Confirmed fish hosts include Blacktail Shiner and Red Shiner (Dudding et al. 2019).

Like all freshwater mussels, the Balcones Spike is relatively inactive and capable of moving only small distances. Their primary mode of moving or colonizing new areas is accomplished by the movement of the fish hosts or by high flow events that wash adult mussels from their current location and move them downstream.

Balcones Spike in the lower Guadalupe River have been found to breed from February to June (Dudding et al. 2019).

Ongoing Research

A significant amount of research is done on freshwater mussels. Agencies across the state are researching them, including the U.S. Fish and Wildlife Service, the Texas Comptroller of Public Accounts, the TPWD, and the Brazos River Authority.

Several universities also are researching freshwater mussels, including Texas A&M University, Texas State University, Baylor University, the University of Texas at Tyler, and Auburn University. These studies include surveys to identify new populations, genetic investigations, and tolerance studies.

The TPWD also maintains the Texas Mussel Watch Program, where members of the public can submit their observations of mussels to help gain a better understanding of the distribution and status of mussels.

In addition to regulating commercial harvesting of mussels, the TPWD also regulates the take of mussels by individuals by requiring a fishing license and freshwater fishing endorsement.

In August 2020, the Brazos River Authority submitted a Candidate Conservation Agreement with Assurances to the U.S. Fish and Wildlife Service for consideration, in which the BRA commits to performing voluntary conservation activities aimed at reducing threats to the Balcones Spike in the Brazos basin. It is anticipated that this agreement will be executed sometime in 2021.

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  • Barnhart, M.C., W.R. Haag, and R.N. Williams. 2008. Adaptations to host infection and larval parasitism Unionoida. Journal of the North American Benthological Society. 27:370-394.
  • Dudding, J., Hart, M., Khan, J., Robertson, C.R., Lopez, R. and Randklev, C.R., 2019. Host Fish Associations for Two Highly Imperiled Mussel Species from the Southwestern United States: Cyclonaias necki (Guadalupe Orb) and Fusconaia mitchelli (False Spike). Freshwater Mollusk Biology and Conservation, 22(1), pp.12-19.
  • Fritts, A.K., M.W. Fritts, S.A. Carleton, and R.B. Bringolf. 2012. Shifts in stable isotope signatures of Freshwater mussel glochidia during attachment to host fish. Journal of Molluscan Studies 79:163-167.