What species is this skull from?
We found a very similar skull on a beach near Richardson Bay, Lasqueti BC. Decided it was a seal skull (locals agreed) See harbor seal skull: http://www.skullsunlimited.com/record_species.php?id=4726
I know guessing is frowned upon but given the small size of the skull and the relatively small inlet you've cited as a location, my best guess is it's the back half of a dolphin's skull. Probably Pacific White-Sided Dolphin (Lagenorhynchus obliquidens)
Sorry for the watermark. From Skulls Unlimited
^ The cheek-bones look pretty similar, but the snout and the pit on the side that superficially resembles an eye orbit have been broken off or caved in on your sample.
^ I can't find pictures of the underside of a skull without the mandible, but the hole in the bottom of yours might match the one on the very far right here, though I'm not sure about the bulges on the underside.
I can't be sure if its a complete match but my best proposal is that it's a juvenile dolphin skull.
I agree with Mark it is a seal, specifically the rear half of the skull.
That low flat profile of the skull combines with with a wide robust zygomatic is indicative of seals. The triangular and yet flat sagittal crest is also a dead giveaway. The orbits are high, large, poorly defined, and deeply recessed with only a narrow band between them that is indicative of seals. Check out a these seal skulls for comparison.
In the last one you can even see how you end up with only the rear portion as you do, as the rest is only weakly attached and the zygomatics are weakly fused at the center and tends to separate as well. I can't tell you the species but you definitely have a seal.