What's the difference between a california and a steller sea lion?

This is how you can tell the difference

adult steller sea lions are lighter tan or reddish brown in color versus the darker brown or black colored sea lion

a full grown male steller sea lion is at least three times a big as an adult male californian sealion

adult male stellers have a "mane" of thick furr around there neck. But adult male californian sea lions have a large bump extending from their forhead

stellar sea lions vocalizations sound like roars. And californian sea lions sound like barks

hope this helped =)