This paper evaluates population trends in Giant Pacific Octopus (GPO) in the Pacific Northwest using REEF Volunteer Fish Survey Project data and other data sources. The authors found large changes in GPO abundance linked to average water temperatures. GPO sighting frequencies ranged from a high of 39% to a low of 11%. For every additional degree increase of 4-year average temperatures, the Puget Sound GPO sighting frequency dropped about 19 points. That’s a loss of roughly 75% of typical diver sightings for every degree C. The authors also noted that, of the many datasets they used to conduct the analysis (including a transect study in Prince William Sound focused on GPO), the REEF dataset provided the most comprehensive set of information on GPO populations and provided the strongest correlation coefficients.