During Spring Training 2022, Dr. Charles Randklev of Texas A&M National Resources Institute Dallas asked a class of TMNCPC members a critical question regarding the generally unseen mussels occurring in our state: Why care?
Trainees learned of the role freshwater mussels provide in structural habitat, stabilizing streams in high flow events, biofiltering and recycling nutrients while they clean the water. At 5-140 liters per mussel per day of filtration capacity, these ‘habitat engineers’ have been likened to wastewater treatment facilities. They are important members of Texas aquatic systems!
They are branded with names like ‘pistolgrip,’ ‘pigtoe,’ ‘healsplitter,’ and ‘fatmucket.’ Sessile creatures, they don’t move around much; it’s because of this that many species have seen steep declines. Changes in hydrology (adequate flow, damming, flooding), degradation of water quality, and increased siltation and sedimentation all diminish their ability to thrive. Mussels are ectothermic like other aquatic animals; summer heat will kill those not thermally buffered with sufficient water depth.
Loss of fish populations are adversely affecting their reproductive life cycles. Many species require specific host fish species onto which their larvae, glochidia (glo-KID-ee-uh), can attach, maturing in parasitic fashion until dropping off elsewhere as juveniles, then populating new places along the bottoms of our many rivers and streams as biofiltering adults.
In Texas, human development disturbs natural aquatic systems; our thirst for clean water necessitates conservation efforts and attention to these creatures! One of the most vulnerable groups of animals today, 15 species are now threatened in Texas, and 12 are being considered for the Endangered Species Act. Nationwide, 37 species of freshwater mussels are already presumed extinct (Master et al. 2000). The Texas Hornshell (Popenaias popeii), along the Pecos water system with confluence into the Rio Grande River, is already listed as endangered.
About the Header Image
(Photo credit: Shannon Westveer) The giant floater mussel (Pyganodon grandis) inhabits low velocity habitats in streams, rivers, lakes, and reservoirs, and is most often found in fine substrates such as silt and sand (Cummings and Mayer 1992; Downing et al. 2000; Whaley et al. 2004; NatureServe 2015). More tolerant of lower oxygen concentrations than most other mussels, it might explain why it is the most observed species in both Fort Bend County and in Texas according to Research Grade observations recorded through iNaturalist.
Learn More About Mussels
- iNaturalist.org | Research Grade Freshwater Mussels in Texas
- Texas A&M Natural Resources Institute Dallas | Mussels Research
- The Partnership for the Delaware Estuary | Side-by-Side Filtration Time Lapse Video