Yes those are all dead fish(Mostly small minnow etc..)
This pic was taken by my mother(Judy) who lives on Lake Granbury.
The Culprit: Blooming Golden Algae.
"Golden algae are naturally occurring and typically flourish in brackish water.
Under certain conditions, they can produce toxins that kill fish,
but they are not believed to harm humans, wildlife or livestock."
"Another golden algae outbreak hit the Brazos River basin last spring
as Possum Kingdom Lake and Lake Whitney had thousands of fish killed."
Info From http://www.star-telegram.com