Macrobrachium carcinus is one of the only aquatic predators in headwater Puerto Rican streams and may play an important role in structuring stream communities. Local artisanal shrimpers have targeted this shrimp for generations. Although this shrimp may be both ecologically and culturally important to the island of Puerto Rico, little is known about its population biology or its rate of harvest. We sampled sites across three watersheds in Puerto Rico and found that M. carcinus is widely distributed in moderate abundances. We initiated a population estimate using mark-recapture methods and recaptured 21 of 127 marked in the Río Espíritu Santo suggesting high pool fidelity. We also conducted a focus group survey with 22 fishermen and asked questions regarding their fishing habits. Fishermen primarily target M. carcinus and two fish species. On average, they fish seven times per month and harvest 4.6 pounds of fish and shrimp per outing. We also accompanied shrimpers, and found that they can catch up to four predatory shrimp per hour that range in size from 35 to 105 mm carapace length. Further research is necessary to estimate population size, parameterize a population model, and estimate overall harvest rates.