Fish usually need to be caught to be measured, but scientists from the Grouper Moon Project and Cayman Islands government have used video camera systems to collect an impressive 17-year dataset of Nassau Grouper lengths from Little Cayman. We combined this with information on growth and abundance to produce a comprehensive assessment of Nassau Grouper on Little Cayman. We found that Nassau Grouper recovered on Little Cayman largely thanks to one strong year class from 2011 spawning, 4-8x average. Length data from Cayman Brac also showed signs of a strong 2011 year class and substantial improvement in population status in recent years. Our analysis demonstrates that video camera systems are effective for monitoring protected fish spawning aggregations and are especially promising for situations where catch, effort, and invasive length data are unavailable.