This paper documents attacks by the isopod Excorallana tricornis tricornis on Nassau grouper caught in Antillian fish traps during the post-spawning season of Spring 2005. These findings were documented during Grouper Moon research by REEF and Cayman Islands Department of the Environment staff. Fish were being trapped in order to acoustically tag individuals from sites around Little Cayman Island in order to better understand what percentage of reproductive-size individuals attend the aggregation each year. The paper discusses the apparent energetic costs associated with spawning. This work was also presented as a poster at the 56th Gulf and Caribbean Fisheries Institute Meeting in 2005, and a summary of the poster is posted online (POSTER).