Zebra Mussel Monitoring Project (ZMMP)

Elm Fork Trinity River

River Status

Texas Parks and Wildlife Status: Positive

Zebra mussels or veligers (larva) have been detected on more than one occassion.

USGS Data Collection Activities

River Map

Blue triangles show USGS data-collection locations.

Zebra Mussel Detection Data

Larvae (Veliger) Detections
Most Recent Detection First Date Detected
06/18/2020 < 0.01 per Liter 10/09/2012

Larvae detection counts are averaged across all sampling sites.

Zebra mussels typically spawn in the spring and autumn as microscopic, free swimming larvae called 'veligers'. The USGS uses fine mesh nets to sample for larvae during the spawning season.

Adult or Juvenile Detections
Most Recent Detection First Date Detected
06/18/2020 10/09/2012

Adult detection counts are averaged across all sampling sites.

At the end of their larval stage, zebra mussels attach to a substrate and metamorphose into juveniles. The USGS conducts both visual and SCUBA inspections, and deploys artificial substrates as passive samplers, to get a estimate of the juvenile and adult zebra mussel populations.

Water Quality Data

Water-quality monitoring is important for studies of zebra mussel survival, growth, and reproduction. Water-quality data are also important for risk assessments for zebra mussel infestation.