Folks who are wondering how a session bassist could do it without sight reading skills need to understand that pop music sessions rarely work from formal charts in standard notation. In order for a bassist to be required to read a chart, that would necessitate someone charting the bass line in advance. And that just doesn't happen all that often in pop music (the rare pop bands like Steely Dan or Frank Zappa being the exception). The bassist in a pop music session usually listens to a solo voice/instrument version, or perhaps some live or recorded guide tracks, and looks at a lead sheet for chord progression. They discuss with the BL/producer/arranger what the overall feel and goal is for the track. Then they come up with some ideas and start going for it, while the session leader comments and filters the line, either approving the ideas or making suggestions along the way. Sometimes there is a pre-written signature bass line integral to the song, and that gets demonstrated for the bassist on piano or guitar. As soon as everyone is on the same page, they roll for takes. A musician like Pino, in addition to having an uncanny ability to augment the song in a positive way, can wrap up this process relatively quickly, saving a lot of time and money, which is another reason he's so in-demand for both studio and stage work. He has an incredibly good intuitive knowledge of his instrument, a wide musical vocabulary, great ears, and excellent memory.
I have no idea where Pino stands as a sight reader of standard notation, but as others have mentioned, in his line of work, I doubt it's called for all that often.