The Coamo River Basin stretches 38 kilometers from the mountainous region of the Coamo municipality to the coast of southern Puerto Rico, where it drains into the Caribbean Sea through the municipality of Santa Isabel. Classified as a dry forest by the Holdridge Lifezones System, the basin hosts a freshwater decapod community comprising ten shrimp species and one crab species. Among the species, the freshwater shrimp Micratya cooki Karge, Page & Klotz, 2013 stands as the most recently described and endemic to Puerto Rico. To assess the ecology of M. cooki, three sampling sites were selected downstream of the collection site described by Karge et al. 2013. Species richness, evenness, and diversity were calculated using Shannon’s Diversity Index, and statistical significance regarding M. cooki was determined using a two-way ANOVA. Of the 11 species of decapods reported for the Coamo River, eight species were found during samplings at all three sites, spanning the genera Atya, Macrobrachium, Potimirim, Xiphocaris, and Micratya. Preliminary results for M. cooki show statistical significance (p ≤ 0.05) in post-orbital carapace size, influenced by gravidity and site location. Additionally, variations in abundance and habitat preferences between upstream and downstream populations were noted, suggesting potential ecological adaptations or differences in environmental conditions within the basin. This study, to the best of our knowledge, constitutes the first ecological survey on the atyid shrimp M. cooki and the decapod community it inhabits, accentuating the importance of protecting the Coamo River Basin and other rivers in the dry forest region of Puerto Rico.