Dead fish are washing up along beaches on the Texas Gulf Coast, officials say.

(CNN) — This week, Texas beachgoers along the Gulf Coast may have observed a startling sight along the coastlines: possibly thousands of dead fish washed up on the sand.

One couple walking along Quintana Beach near Freeport, observed fish that were scattered for miles down the coast, according to CNN affiliate KSAT.

“Was hoping to take advantage of the flat surf and catch a quick limit of speckled trout, but things didn’t go as planned, unfortunately!” said Darrell Schoppe, who posted a video of the fish on Facebook, KSAT reported.

Other social media videos and photos showed piles of mostly small fish coating the beach’s edge during what wildlife officials have described as a “low dissolved oxygen event.”

The Gulf menhaden, which the National Oceanic and Atmospheric Administration says has the largest fishery yield in the Gulf of Mexico, has been the most-impacted species by this fish kill, according to wildlife officials.

Texas Parks and Wildlife’s Kills and Spills Team Region 3 investigated what’s happening along the coast, spokesperson Lerrin Johnson said in a statement to CNN.

The team of biologists examine fish and wildlife kills caused by natural events and pollution.

“Fish kills like this are common in the summer when temperatures increase,” Johnson said.

“If there isn’t enough oxygen in the water, fish can’t ‘breathe,’” she added.

Low dissolved oxygen, in many cases, is a natural occurrence, according to Johnson.

Patty Brinkmeyer, park supervisor at Quintana Beach County Park, told CNN there have likely been “hundreds of thousands” of fish washed up on a six-mile stretch of beach since she first observed the event Friday morning.

“You could literally see a straight-across mass of fish floating on the water,” Brinkmeyer said. “It looked like a big blanket.”

She’s worked at the park for 17 years and said this occurrence was the third time she’s observed any number of fish wash ashore.

“This is by far the most” she’s ever seen, Brinkmeyer said Saturday.

Colder water tends to hold more oxygen, and the warmer sea waters along Quintana Beach could have contributed to the killing of menhaden, park officials said on Facebook.

Before fish kill events occur, wildlife officials say fish can often be seen attempting to gulp at the water’s surface for oxygen during early morning hours.

“Some fish may also be lying on the bottom or at the edge of the water, “Johnson said in a statement.

Sunlight-driven photosynthesis causes increased dissolved oxygen during daylight hours, according to Johnson.

“Photosynthesis stops at night and may slow down on cloudy days, but plants and animals in the water continue to respire and consume free oxygen, decreasing the dissolved oxygen concentration,” she said.

Crews at Quintana Beach County Park, located on Quintana Island, were raking up whatever fish they could Saturday morning, according to the park’s Facebook page.

The post warned potential visitors not to expect the fish to be completely cleared away.

“Our recommendation is that you avoid the beach altogether until this event is over,” the post read, with park officials advising that no one entered the water.

“There are dead fish floating all around, that can’t be healthy,” Brinkmeyer said. “You don’t want to walk through that.”

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