User blog comment:Jamintheinfinite/Subnautica Creature Evolution/@comment-35546951-20181012164522/@comment-28450065-20181012192257

It says that the creature was "eel-like in structure". That does not make it a relative of the eels living today.

The electric EEL from Earth is not even an eel yet is also eel-like in structure.

For further proof of this within the game, look at the Crabsnake. It is definitely eel-like in structure, but there is no mention of a relation to the other eels.

Kharaa not being on the planet doesn't mean it didn't run out of food either. The food source of the species could have disappeared for many reasons. But there's no for or against that.