The Galveston County Daily News reported Wednesday that experts blame low levels of dissolved oxygen for the fish kill in Lake Madeline.
The Texas Parks and Wildlife Department says the fish kill was first reported Saturday at the Galveston lake, which connects to Offatts Bayou.
Department biologist Steven Mitchell says an algae bloom was spotted at the boat ramp. Mitchell says that was likely caused by an unknown nutrient present in the water.
Mitchell estimates about 15,000 Gulf menhaden died. Other species, including red fish and speckled trout, died in smaller numbers.