Hands-On Fish Management: Using Manual Removal to Restructure a Crowded Largemouth Bass Population in Puerto Rico

Largemouth Bass Micropterus salmoides floridanus were stocked in Cerrillos Reservoir in 1997. Within three years, relative weight declined from above 100 to ~80 and the population displayed characteristics of overcrowding, with much of the population composed of fish ≤ 350mm. A protected slot limit (356-508mm) was implemented in 2003 to encourage harvest of smaller bass, protect intermediate-sized bass, and allow for occasional harvest of trophy bass. However, limited effort and angler attitudes towards harvest of small bass maintained the bass crowded situation in the reservoir. Therefore, the regulation was removed early in 2011. Because overcrowding persisted, we conducted an experimental removal of fish from the crowded size classes (200-380mm) in 2012. We removed 2,333 Largemouth Bass equaling 26% of the crowded biomass and 20% of the total biomass. Preliminary data suggest Largemouth Bass condition has improved, with average relative weight increasing from 81 to 87within seven months post-removal. Population sampling in spring 2013 will confirm if the Largemouth Bass population responded to the experimental removal. Computer simulation models will be used to predict population response to various harvest strategies to determine if mechanical removals of Largemouth Bass are a viable management strategy to prevent Largemouth Bass crowding within the reservoir.