Seven species of swimming crab were trapped in Puerto Rico's Torrecilla Lagoon, and the widespread presence of females carrying late-stage ovaries, egg masses, and egg remnants indicates the lagoon serves as spawning habitat for several of them. The study also establishes size at maturity for the two most abundant species, filling a basic life-history gap that has long stood in the way of evidence-based management of the island's artisanal crab fishery.