As an AI language model, my knowledge cutoff is in September 2021, so I may not have the most up-to-date information on recent events. However, up until my last update, I don’t have specific information about a massive fish die-off on the Texas coast. It’s possible that the event you’re referring to occurred after my knowledge cutoff date or that it may not have received widespread attention in the available sources.

Massive fish die-offs can have various causes, including natural factors and human activities. Some potential causes could include:

1. Algal Blooms: Certain types of harmful algal blooms, such as red tides or blue-green algae blooms, can produce toxins that are harmful to fish and other marine organisms. These toxins can cause mass fish mortality when fish consume contaminated water or organisms that have ingested the toxins.

2. Oxygen Depletion: In some cases, fish die-offs can occur due to oxygen depletion in the water. Factors such as pollution, excessive nutrient runoff, or changes in water temperature can lead to low oxygen levels, making it difficult for fish to survive.

3. Disease Outbreaks: Fish populations can be susceptible to various diseases, and under certain conditions, outbreaks can occur, leading to mass mortality events. Bacterial, viral, or parasitic infections can spread rapidly among fish populations, especially in overcrowded or stressed environments.

4. Pollution: Pollution, such as chemical spills or runoff from agricultural or industrial activities, can have detrimental effects on fish and other aquatic organisms. Exposure to high levels of pollutants can cause fish mortality directly or indirectly by damaging their habitats and food sources.

5. Extreme Weather Events: Severe weather events, such as hurricanes, storms, or sudden temperature fluctuations, can impact fish populations. Extreme changes in water temperature, salinity, or oxygen levels during these events can lead to stress and mortality among fish.

To get the most accurate and up-to-date information on the specific incident you’re referring to, I recommend checking local news sources or official reports from relevant environmental agencies or organizations in Texas.