programs Natural Resources

Freshwater Mussels - East Texas

Louisiana pigtoe, triangle pigtoe, Texas heelsplitter


Recent research – although limited – shows the freshwater mussels of East Texas have declined in number, most likely because of historical over-harvesting, habitat degradation, loss of host fish species and the introduction of non-native invasive mussel species. While it is clear there are fewer mussels overall, it is not obvious how specific species of mussels are doing. Further, recent genetic work shows the original classification of mussel species in East Texas may need to be corrected.

The U.S. Fish and Wildlife Service (FWS) is now conducting species status assessments for these species and expects to publish its proposed listing decisions before the end of 2020. The science team consists of state and federal mussel experts including FWS and Texas Parks and Wildlife (TPWD). The Texas Comptroller of Public Accounts (CPA) holds a supporting role on the team to ensure FWS receives current scientific information and reports for its analysis and to help facilitate stakeholder engagement.

Research Description

In 2014, the Texas Comptroller of Public Accounts (CPA) contracted with the University of Texas at Tyler (UTT) to conduct surveys to determine the East Texas freshwater mussels’ distribution, range, abundance, habitat preferences and areas of high conservation value. Researchers selected survey sites by modeling the species’ distribution using data collected from previous multi-year studies, then performed field studies to verify the modeling.

The project defined habitat types and developed a standard survey protocol. This protocol can then be used in future surveys to refine knowledge about the species’ habitat preferences over time. In addition, the researchers evaluated the native mussels’ responses to various environmental factors and threats, including ammonia levels and sedimentation and the impacts from non-native invasive zebra mussels, and conducted genetic studies.

UTT submitted final reports and data for this research to CPA and FWS, which can be found on the sidebar of this page.

At the conclusion of these reports the FWS asked the CPA to help with surveys in areas of the state researchers were not able to visit. Specifically, the FWS wanted to know about the status of heelsplitters in reservoirs of East Texas and the Louisiana pigtoe in the Lower Neches River.

The results of these surveys will be available in December 2019.

Why This Research Matters

Freshwater mussels are a food source for birds, fish, turtles and all sorts of mammals, and, as filter feeders, mussels help clean the waters in which they live by collecting bacteria and algae, as well as accumulating contaminants in their soft tissues. Because they have limited mobility and are typically long lived, freshwater mussels are sensitive to environmental changes and can serve as bio-indicators of water quality and overall ecosystem health.

Research during the past several years indicates these mussel populations are in decline. However, there were significant knowledge gaps, including a limited understanding of the species’ range and habitat needs. A listing of some or all of these species could affect water users, landowners and businesses that rely on freshwater sources or conduct activities in or adjacent to mussel habitat.

The UTT research provides essential information needed for the listing and critical habitat decisions. Prior to this effort, even basic information about the species’ locations and biology was unavailable. The survey data, habitat models and genetic results will be especially important for informing FWS’ decisions and determining voluntary conservation actions.