Texas Parks & Wildlife Magazine   


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Mystery Solved — What Killed Freddy the Fish?

When detectives discovered the lifeless body of Freddy, the striped bass, they searched for other dead fish in the area. Often, where there’s one, investigators find others. And they did. Detectives now had an official “fish kill” on their hands.

Greg Conley, a pollution biologist with the Texas Parks and Wildlife Department’s Kills and Spills Team, specializes in solving fish kills, so he took over Freddy’s case.

Conley solved the mystery: Freddy and his friends died of nonpoint source pollution. Lime in the soil at a construction site had been carried by runoff to the stream where the fish lived.

Lime? But, but … isn’t that a harmless little green fruit? Well, yes. But it’s also a white powder put into the soil to make dirt stronger so houses won’t budge after they’re built.

Here’s what Conley believes happened:

A crazy storm came, creating major runoff from a place where workers were getting the dirt ready to build new houses. Oh, what a mess that storm made!

From this construction site, the rain washed away a bunch of dirt into storm drains. Have you ever noticed those places in the street where all the extra water goes? Well, those are storm drains, and all the water heads there. Clean, gross, yucky, trashy … all that water goes directly into creeks and streams.

So right into the storm drains went all that muddy water from the construction site … goosh … moosh … sloosh … then right into the creeks and streams went all that muddy water from the construction site ... goosh … moosh … sloosh …

But plain old muddy water didn’t kill Freddy and his friends. Nope. Remember, how that dirt also had white powder in it called “lime”? Well, when runoff brought the dirt with the lime into the stream, that’s what killed Freddy and the others.

Yep, unfortunately for them, that lime-laden water surged straight at them. And they had no idea of the danger headed their way! No one could warn them, “Hey you guys get outta there! There’s nonpoint source pollution coming at you! Swim!”

The lime changed something in the water called “pH.” It made the pH go too high, too fast, and the fishes’ bodies just couldn’t handle it. When pH in the water changes way too quickly it kills fish. Freddy and the other striped bass died, and created a mystery for us to solve.

But now we know what killed Freddy the Fish.

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