Giant Salvinia

Previously Funded Aquatic Invasive Species Research

Zebra Mussels

Impacts of zebra mussels on native mussels and population dynamics and downstream dispersal of zebra mussels.

Texas State University

Zebra mussels have the potential to negatively affect Texas’ native mussel species, many of which are listed as threatened or endangered species. This study surveyed native mussel populations to study zebra mussel fouling of their shells and the health of native mussels in infested areas. Laboratory tests were used to examine the impacts of zebra mussel die-offs and fouling on native mussels. Additionally, the project continued analysis of the population dynamics of zebra mussels in Canyon Lake and their spread downstream in the Guadalupe River.

Project Final Report

Growth, survival and reproductive success of zebra mussels in Texas lakes

Texas Christian University

Water chemistry plays an important role in the success of zebra mussel invasions. This research project evaluated how variable water chemistry conditions (for example, calcium concentration) in lakes across the state impact the growth and survival of zebra mussels. Previous studies have shown that calcium is critical for survival and growth of adult zebra mussels. This study examines whether calcium levels affect zebra mussel egg fertilization, development of larvae, and growth of juveniles and adults.

Project Final Report

Measuring the risk of zebra mussel invasion in lakes downstream of infested lakes

Texas Tech University, Texas State University, US Army Corps of Engineers – Engineer Research and Development Center

Risk assessments based on predictive models that utilized environmental data coupled with DNA sampling helped determine which Texas lakes are at greatest risk of invasion by zebra mussels and were used to help guide zebra mussel early detection sampling.

Zebra mussel growth, reproduction, and invasion in Texas lakes.

University of Texas at Arlington

Research findings indicated that zebra mussels can decline in abundance in some lakes given certain environmental conditions exist, including extended periods of low pH and low water oxygen levels. Zebra mussel abundance can also be cyclical as their populations increase and decrease over time.

Aquatic Plants

Combating invasive aquatic plants by manual removal and planting of native aquatic plants

University of Texas at San Antonio, Edwards Aquifer Authority, City of San Marcos, US Fish and Wildlife Service – San Marcos Aquatic Resources Center

Hydrilla is one of the most common invasive aquatic plants in the upper San Marcos River, which is home to endangered Texas wild rice—a submerged aquatic plant—and Fountain Darters. This research examined whether planting Texas wild rice and other native aquatic plants after hydrilla is manually removed can help to improve the effectiveness of hydrilla management efforts. This study also evaluated whether planting of native species can suppress or outcompete the invasive hydrilla.

Project Final Report

Development of several new biological compounds in the laboratory to be used in management of giant salvinia.

Stephen F. Austin University

Giant salvinia is currently one of the most problematic aquatic plants in Texas due to its ability to develop dense mats that impact habitat for native fish and wildlife and impede boater access. This research developed natural ‘endocide’ compounds extracted from the giant salvinia plant itself. Testing showed that the endocides poisoned or inhibited growth of other giant salvinia. More research is needed to assess whether endocides have potential for helping to manage giant salvinia.


Introduction of non-native fishes in Texas streams

Stephen F. Austin University, Texas A&M University – College Station

Bait-bucket introductions of non-native fishes are widespread in freshwater ecosystems in the US. This may be how two coastal fish species—the Sheepshead Minnow and the Gulf Killifish—were introduced into inland freshwaters outside of their native range in Texas where they may have negative effects on imperiled native fish species. Researchers conducted bait shop surveys in Texas to learn more about the fish species being sold and whether this is a potential introduction pathway for these two invasive species. Field studies in the Brazos and Red rivers evaluated the status of populations of these invasive fishes and how they may affect the native aquatic ecosystem. Additionally, an ecological model was developed to map current and possible future introductions of these species across Texas river basins.

Project Final Report

Evaluating research gaps related to tilapia in Texas

Texas Tech University

Invasive tilapia have been found in some Texas waters and can escape from ponds built on creeks. Researchers assessed the risk this invasive species poses to imperiled native fishes by reviewing published science and developing a computer model of areas in Texas that would be suitable for them to survive. This study contributed to review of regulations for exotic species that seek to prevent harmful impacts on native ecosystems.

Mapping the geographic range of bigheaded carp in Texas

Texas Tech University

Current regulations prohibit movement of live nongame fish in areas in Texas where invasive bigheaded carp have been found in the past to prevent them from being spread by bait bucket transfers. Researchers and TPWD biologists surveyed for these invasive fish using electrofishing and tested for their DNA in the environment. No live bigheaded carp or their DNA were found in new areas. This suggests that these prevention efforts have been effective to prevent these invasive fishes from expanding their range in Texas waters.

Age and reproductive status for invasive catfish in Landa Lake

Texas A&M University – College Station

Methods were explored for more effective management of invasive suckermouth catfish in Texas and information on catfish age, growth and reproduction was collected to assist future control efforts.