The Department of Fisheries and Oceans in Canada just published their analysis of 13 population surveys conducted during the summers from 1971 to 2013.
They found that juveniles and adults (non-pups) increased at an average rate of 3.8% per year and pups increased at an average rate of 4.8% per year over that 42-year period. This resulted in a 4-fold increase in population size since protections were first instituted in 1970.
During the 2013 season, they estimate that approximately 39,000 Steller sea lions were present during the breeding season (over summer). Winter counts were higher, with an estimated 49,500 Stellers present in British Columbia waters, suggesting sea lions from Washington and Oregon may be displaced to Canada by California sea lions migrating north during the winter months, and some animals from Southeast Alaska moving southward during the winter months.
A more complete summary can be found at: http://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2018/2018_006-eng.html
The report: Olesiuk, P.F. 2018. Recent trends in Abundance of Steller Sea Lions (Eumetopias jubatus) in British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2018/006. v + 67 p., can be downloaded here.