GameStop shares are going nuts, thanks to Pokemon Go

GameStop is going nuts, thanks to Pokémon Go.

Shares of the video-game retailer jumped by as much as 7% in trading on Monday after CEO Paul Raines told CNBC that sales at stores that are gyms in the app are up 100%.

The location-based game uses augmented reality to guide players in finding Pokémon. It quickly surged to the top of app-store rankings.

Gyms are real-world places where players can take their Pokémon for battles. Raines said there were 462 stores this past weekend that were Poké gyms.

Across the board, Pokémon merchandise sales are "up significantly," Raines said, in what's traditionally a weak time of the year for video gaming.

GameStop rose to as high as $30.21 per share, the highest level since May. Bloomberg noted that it was the biggest one-day gain for the stock since May 2015.

GameStop shares have fallen 35% over the last 12 months. Last November, the stock plunged after the company reported weaker-than-expected quarterly results on sluggish software and hardware sales.

Pokémon Go has been even better for its maker. Nintendo's stock surge in the days after the game's release added as much as $9 billion to the company's market value.

Here's a chart showing the rise in GameStop shares on Monday: