Ictalurus furcatus (Blue Catfish) provide trophy recreational fishing opportunities in Virginia's tidal rivers; however, potential ecological impacts are of concern. We used mark-recapture techniques and electrofishing in 2007 and 2014 to estimate Blue Catfish density and biomass in Powell Creek. A 66% decline in fish density occurred between 2007 (708 fish/ha) and 2014 (239 fish/ha) and biomass declined by 31% over the same timeframe (266 kg/ha to 185 kg/ha). These findings are supported by long-term monitoring trends in the tidal James River. Here, we provide: (1) data relative to temporal shifts in abundance and biomass, (2) data for use in subsequent population-dynamics analyses, and, (3) points of caution when assuming temporally static populations for introduced species. We demonstrated the feasibility of low-frequency electrofishing and mark—recapture methods to estimate Blue Catfish abundance, and recommend use of the approach where catfish abundance estimates are important.