Thousands of dead fish wash ashore along Texas Gulf Coast

Thousands of dead fish washed up on the shores of the Texas Gulf Coast seemingly overnight this week. Lake Jackson resident Karri McKim was walking along the shores of Bryan Beach and Quintana Beach near Freeport, Texas to watch the sunrise on Friday morning when she came across the grim sight. Footage shared by McKim shows the hordes of dead fish extending for miles along the coastline.

The fish kill was investigated by the Texas Parks and Wildlife Department's Region 3 Kills and Spills Team, a group of biologists who investigate fish and wildlife kills resulting from pollution or natural events. The team determined that the event was caused by a low dissolved oxygen event, which is a common condition during the summer when temperatures rise. The species most impacted was Gulf menhaden.

Daily variations in dissolved oxygen concentration are related to photosynthesis and aerobic respiration. "Increased dissolved oxygen during the day is a result of photosynthesis which is driven by sunlight," Jensen said. "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."

Before kill events, you can often spot fish trying to get oxygen by gulping at the surface of the water early in the morning, Jensen said. "Some fish may also be lying on the bottom or at the edge of the water," he added.