Intensive exploitation on queen conch led to the species listing under CITES, forcing national and regional agencies to develop and implement management plans to certify sustainability, which frequently use shell-based minimum size limits. Yet, enforcement of these regulations requires landing the conch intact, and fishers argue that this reduces efficiency, while negatively affecting both diving and boating safety. This study examined the morphology of queen conch to establish if there are alternative measures useful for enforcing existing regulations without requiring the shells to be landed. In Puerto Rico, current management regulations include a 9-inch (22.86 cm) minimum shell length or 3/8-inch (9.5 mm) minimum lip thickness. From nine locations around Puerto Rico, conch were assessed for sex, maturity and 9 morphometric measurements. Regression analyses focused on differences between juveniles (no shell-lip), thin-lipped (< 10mm) adults and thick-lipped (10 mm) fully mature adults, and conch smaller or > 229 mm. Despite strong linear relationships, there were no clear patterns separating legally from illegally harvest conch, due to the large variability within and among conch from different areas. While no single factor could account for both shell length and lip-thickness, a combination of approaches could be used to approximate the legal status of harvested conch. These were a minimum operculum length of 2.75 inches (70 mm) or the presence of fully developed reproductive structures (verge/egg groove), with a maximum of 10% of the catch departing from these size-based criteria. Implementation would require training enforcement personnel to measure the operculum and to recognize the male/female sexual structures.