There are two species of fish in the body of water. The six eyed fish and bass. The bass fish need rain to reproduce while the six eyed fish do not. As rain falls both species thrive and reproduce. The six eyed fish has special gills that allow them to close and open them whenever they want.
However, as rain does not fall throughout the days the bass do not reproduce as much. But the six eyed fish do reproduce even without the rain.
Over the past three weeks there have been no rain and the water actually starts to decrease and the bass start to die off and the six eyed fish reproduce.
After the first month with no rain most of the water has gone and more land has appeared, and the six eyed fish still reproduce while the bass population decrease.
Still without any water from the rain the bass population has almost gone extinct with only one bass alive, while the six eyed fish keeps reproducing
After one year without any water the bass population has gone extinct and the six eyed fish is the most populated species of fish. Because of their special gills the six eyed fish could adapt to the less amount of water and reproduce without any trouble.