Yes, Bass will eat other bass if hungry and given the opportunity. though they do protect their own offspring during the spawning process by fending off other predators until the fry are old enough...
I believe you mean to say "Does a double bass read from bass or treble clef?"
The answer to that is bassists almost always read bass clef. But very good bassists that play very high read treble clef...
By the term 'normal Basses', i assume that you mean acoustic/upright basses. In this case then yes, electric basses are played like you play a guitar except generally with the fingers as you do with...