Answer:
More dark colored fish survived long enough to reproduce
Step-by-step explanation:
The rule of natural selection selection is that, survival is for the fittest.
For natural selection to occur, there must be a variation between the group of species and reproduction where the superior genes can be passed to the offsprings.
In this case, the variation was some fish were dark others were light colored.
When the water turned cloudy the dark colored fish were able to survive long enough to reproduce compared to the light colored fish.