Llano River Fish Population Recovering After Historic Flooding in 2018

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AUSTIN – After finding more than 18 species of fish during a recent sampling trip on the Llano River, the Texas Parks and Wildlife Department’s Inland Fisheries staff are encouraged to see fish populations rebounding following historic flooding in October 2018.

“In 2018 the Llano River was greatly affected by a 100-yr flood that significantly altered its fish habitat,” said John Botros, TPWD River Access Program Coordinator. “Many anglers and local landowners expressed concern to us about the status of the fish population following this catastrophic flooding. While the abundance of fish in the river is lower than it was before the flood, we are happy to report that fish populations are showing signs of recovery.”

During a multi-day sampling trip with the Llano River Watershed Alliance in March 2019, staff used standard fish sampling techniques to assess the fish population on four stretches of the Llano River primarily near the department’s leased public fishing and boating access sites. Although fish were caught throughout the river, biologists found a significant difference in abundance and diversity between the main stem of the Llano River and the South Llano River near Junction.

“The most abundant and diverse populations of fish were found on the stretch of the Llano River near the city of Junction and on the South Llano River,” Botros said. “This stretch appears to be less affected by the flood. We caught multiple species of minnows, suckers and game fish, including largemouth bass and our state fish, Guadalupe bass. Anglers visiting the area this year will likely have higher fishing success focusing on this stretch of the river.”

On the main stem of the Llano River upstream of Castell to Schneider Slab Rd (CR 103) in Llano County, biologists found fish abundance to be much lower than upstream near Junction. Botros said although few game fish were caught – mostly largemouth bass – the fish were considerably larger than those caught from the South Llano River.

 “Although fish abundance on the mainstream Llano River appeared low, this was to be expected since a near-historic flood occurred only a few months prior,” Botros said. “Fish tend to be displaced during large flood events, and it takes time for them to repopulate. Flooding is a natural part of river systems and the fish that live there are adapted to handle it; however, it may take a couple of years for populations to return to pre-flood conditions after a flood this large.  Spring and early summer is when the bass and catfish in Llano River spawn, so we expect juveniles produced by these remaining adults will bolster populations throughout the river by this fall.”

While it will take time for the fish to repopulate in the Llano River to pre-flood levels, fisheries biologists found good habitat in portions of the river, including fallen trees and re-emerging aquatic vegetation. Woody debris in the river channel and along the banks, and aquatic vegetation will provide cover for juvenile fish, along with the added benefit of helping to stabilize banks and trap sediment from future flood events.

TPWD River Studies Program staff also reported recovery of aquatic invertebrate populations, which play an important role in the aquatic foodweb and form a direct link between the organic and inorganic materials in the river and the food for fish, amphibians, aquatic birds, and other riverine organisms.

“We have been collecting aquatic invertebrates from the Llano River for the past few months to understand the effects of a catastrophic flood on invertebrate communities and post-flood recovery,” said Archis Grubh, TPWD Aquatic Ecologist. “Although floods can negatively affect the invertebrate populations, they are highly resilient and can return to preflood numbers quickly. So far we have seen steady repopulation of the invertebrate community, which means plentiful food is available for juvenile sport fish.”

With habitat and a recovering aquatic invertebrate population, biologists are optimistic that fish populations will continue to rebound barring any additional catastrophic flooding. Follow-up fish and aquatic invertebrate surveys are planned for fall 2019, along with surveys to monitor for aquatic invasive species that often spread during flood events. Landowners and visitors to the Llano River can assist TPWD with aquatic invasive species monitoring by reporting sightings of Arundo (giant cane) or elephant ear to aquaticinvasives@tpwd.texas.gov or by taking a photo and posting it on iNaturalist.

TPWD also encourages landowners to assist in the Llano River’s recovery by taking care of sensitive riparian areas adjacent to the river. Recommendations include avoiding any debris cleanup that utilizes heavy equipment which could compact soils, damage stabilizing vegetation, and exacerbate erosion during future floods, planting native vegetation along the river banks and letting trees and other woody debris along river banks remain in place.

“We paddled most of the river between Junction and Schneider Slab Rd and anglers shouldn’t hesitate to visit the river this year for an enjoyable and scenic paddling and fishing experience,” Botros said. “River flows are good this spring and while the flood decreased the abundance of fish, the river is still very much alive, and well on the way to a full recovery.”

Anglers can find public fishing and  paddling access at five TPWD leased sites, including the South Llano River at County Road 150 and the main stem Llano River at Pete’s Pecan Patch, Maso-Llan Road, Castell Crossing and HR Seventh Heaven. Find more information and maps at: https://tpwd.texas.gov/fishboat/fish/recreational/rivers/lease_access/.

More information on the Llano River flood of 2018, including details on changes to aquatic and riparian habitats can be found on the Llano River Watershed Alliance’s website here.