Edwards Aquifer Authority takes action following reports of growing parasite problem in San Marcos and Comal rivers


The Edwards Aquifer Authority is responding to reports of a growing parasite problem with a plan to survey the situation in the Comal River.

Community Impact Newspaper in July published a report about how a parasite named Haplorchis pumilio is threatening fish, such as the endangered fountain darter, in the San Marcos and Comal rivers.

Carried by an invasive Asian snail, the larvae of the parasite penetrate the skin of the fish, causing trauma and inflammation that affects their ability to swim.

Now, through a partnership with the city of New Braunfels, the aquifer authority will examine concentrations of the parasite in the Comal River system.

Michael De La Garza, the senior director of communications and development for the EAA, said no such study has yet been planned for the San Marcos River system.

“Additionally, we have instructed our partners at U.S. Fish & Wildlife Service to provide us with the costs to examine wild caught fountain darters for Haplorchis as part of annual routine fish health screening,” De La Garza wrote in an email.

Population surveys have been conducted of the endangered fish in both rivers for 20 years as part of the Edwards Aquifer Habitat Conservation Plan, but the aquifer authority had not specifically monitored the presence of Haplorchis.

De La Garza said the conservation plan includes methods in place to collect data on fountain darter populations in the San Marcos and Comal rivers.

“Our biological monitoring has shown no drop off in fountain darter populations,” he added.

Researchers at Texas State University, including parasitologist David Huffman and graduate student Allison Scott, had expressed concerns about the long term effects of Haplorchis on local fish populations.

“I think the prudent thing to do is to establish a monitoring program to keep track of this and develop some experiments with snail removal or something so that when a drought comes, we’ll be ready for it, instead of walking out there one day and seeing that almost all the fish are dead,” Huffman said in May.

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