Thousands of dead fish wash up on Texas coast: What is ‘fish kill’ and why it happens

Tens of thousands of dead fish have washed up on the Gulf Coast of Texas due to low oxygen levels in the water. When seas warm up, oxygen is released into the air potentially leading to mass suffocation events like this 🌊🐟🌡️ #ActOnClimate pic.twitter.com/8yMUDFeGOP

— Lewis Pugh Foundation (@LewisPughFDN) June 14, 2023

Among the dead fish covering the shores were mostly menhaden but there were also some sharks, trout, bass, catfish and stingrays, according to The Washington Post. Residents told the newspaper that they had never seen that many dead fish in their lives.

So what led to the massive die-off of fish in Texas?

Officials of the Quintana Beach County Park on June 10 said the incident took place due to a phenomenon called “fish kill”. It is the sudden and unexpected death of many fish or other aquatic animals over a short period and mostly within a particular area. It occurs mainly due to low levels of dissolved oxygen in the water that causes suffocation of the fish.

A combination of factors led to the occurrence of the Texas fish kill.

First was the warm water. When sea surface temperatures rise, it becomes difficult for the fish to breathe as oxygen dissolves easily in colder water in comparison to warmer water. Things take a turn for the worse when a school of fish gets trapped in shallow water, which gets warmer more quickly. “This causes fish to act more erratically, which in turn, further depletes the oxygen from the water.,” officials mentioned in the post. Low oxygen levels could ultimately lead to the death of the fish.

Another factor that contributed to the Texas fish kill was calm seas. Experts suggest that one of the ways for oxygen to enter the water is by mixing with wind and waves. But in the past few weeks, the waves along the Texas Gulf Coast have been very calm, causing the depletion of dissolved oxygen.

One more problem was the overcast weather in Texas. Officials pointed out that due to cloudy skies, phytoplankton were unable to carry out the process of photosynthesis, which is another way of producing oxygen in the water. Photosynthesis is driven by sunlight and it slows down on cloudy days, resulting in decreased dissolved oxygen concentration.

Is the fish kill phenomenon unusual?

No, it isn’t. In fact, Texas experiences fish kills every year during summers, when the temperatures of the sea surface rise. The phenomenon causes the death of mostly menhaden, much like this time, which serve as food for other fish — this is a crucial part of the region’s ecosystem.

What is the impact of climate change on fish kill?

Although experts haven’t found any relation between Texas fish kill and climate change, they say that with rising temperatures of oceans, such incidents will become more prevalent. Warmer oceans will lead to less dissolved oxygen levels, causing more death of fish.

Speaking to NPR, Katie St Clair, the manager of the sea life facility at Texas A&M University at Galveston, said, “Water can only hold so much oxygen at certain temperatures, and certainly we know that seawater temperatures are rising… It is concerning and something that needs to be monitored.”

Warming of the oceans, however, has multiple adverse effects. Studies have found that fish like sardines, pilchards and herring will become smaller in size and not be able to move to better environments. Researchers have also noted that some fish species have started to leave their natural habitat in search of cooler waters, which has disrupted the fish industry.