Conservation Matters August 2013

The Texas Land, Water and Wildlife Connection

Freshwater mussels may be saved during drought by relocating

By Kathy Wythe

Freshwater mussels may be saved during drought by relocating

Researchers with the Texas A&M Institute of Renewable Natural Resources have found that relocating freshwater mussels may be an effective strategy for saving mussels populations impacted by drought or bridge construction activities in Texas.

In a pilot project studying for the first time the effectiveness of mussel relocation in Texas, Eric Tsakiris, research assistant, and Dr. Charles Randklev, a research scientist, relocated three species of mussels from a site in the lower San Saba River in Central Texas to a site upstream with similar species and habitat.

To-date, of the mussels recovered, 100 percent survived and grew, Tsakiris said.

“Short-term relocation is successful,” he said, “but long-term, we still don’t know. Most studies suggest monitoring the mussels after relocation for a minimum of one to two years to get an idea of how they are performing.”

“Although these are really promising results,” Randklev said, “This study was limited to three species and to the San Saba River. It needs to be replicated in different places within Texas with different species to evaluate whether relocation is truly an effective management tool.”

Freshwater mussels are important in the state’s streams and rivers, because they are indicators of stream health, Randklev said.

“Declining populations of mussels can mean that the stream health is deteriorating,” he said.

At the San Saba site, the team collected 80 individual mussels in July 2012 and another 40 in November 2012 and tagged the mussels so they could monitor the mussels’ survival and growth. For the 80 relocated in July, Tsakiris said 88 percent were recovered and 100 percent of those survived. Tsakiris, a graduate student in Texas A&M University’s wildlife and fisheries science department, will continue to monitor the 120 mussels for two years as part of his broader dissertation research project.

Randklev said this pilot study was done in response to a contingency plan developed by the Texas Parks and Wildlife Department and U.S. Fish and Wildlife Service during the drought in 2011 to explore conservation measures to alleviate potential impacts to mussels from the drought.

“The 2011 drought caused record-low flow levels in Texas streams, and many previously perennial streams went dry or became intermittent,” Randklev said. 

In addition to possibly being a mitigation tool during drought, Randklev said relocation may also be a viable option for the Texas Department of Transportation when working on bridges. Because some freshwater mussels are state-threatened or candidates for listing under the federal Endangered Species Act, the department must evaluate a site for the presence or absence of these species prior to construction or renovations of bridges.

Tsakiris and Randklev, along with the Texas Department of Transportation are studying the feasibility of temporarily relocating mussels to other locations while the transportation department works on the bridges.

“There are a lot of questions about survival and mortality when relocating mussels,” he said. “It is important to determine whether relocation is a viable option for drought or construction activities before any mussel species are formally listed,” he said.

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