One of DFO's scientists, Peter Olesiuk—and I have repeated it—did a back calculation of how big the seal population had to have been back around 1880, right after the second smallpox outbreak really decimated first nations people. That's based on adding back into the population, backward over time, the known removals by commercial harvesting and culling. That calculation indicates that there were about half as many seals around in 1880—even after most of the first nations hunting had stopped—as there are today.
There's a lot of uncertainty in any back calculation like that. The data aren't that good, and we don't know exactly how productive the animals were. However, from that and from calculations based on the size of the aboriginal population in B.C., their likely consumption rates and the occurrence of bones from these animals in their middens and things like that, all indications are that they probably kept the populations down to well below half of what they are today.