Learning bass guitar scales is the key to becoming a virtuoso player...
While teaching various bass guitar scales on the upright bass my teacher in college said this...
"I guarantee if you devote one hour of practice per day on two octave bass scales, you will become a virtuoso player in less than 5 years..."
The bass guitar fingering chart I use for all the scales are ones that were either taught to me in college, or, I've constructed my self over years of practice.
These are not set in stone!
The reason you practice scales in two octaves is to teach you how to get from one end of the bass guitar neck to the other as fast and as logically as possible.
There are many ways to do it.
You can experiment and make your own fingerings the key to a good one is in the "shifts".
When ever possible try to shift with your strongest finger... your index finger.
The more ways you practice getting from the bottom of the neck to the top, the faster you'll be able to think on the spot and be able to make a great bass riff.
The bass scales all start on G.
The means, SHIFT!