The frequency of brief droughts and the duration of longer droughts are expected to increase on many Caribbean islands, such as Puerto Rico. Extremely hot, dry periods reduce habitat accessibility and connectivity for migratory species in stream drainage networks. Steep elevational gradients limit the upstream migrations and dispersal of amphidromous crustaceans when barriers such as waterfalls, and cascades dry out. Understanding when to use freshwater shrimp for biomonitoring requires analysis of species-level vulnerability to drought and thermal stress. Differences in sizes and mobility of decapod crustaceans affect when and where each species can seek persistent stream pools during short- and long-term droughts. Large adult Macrobrachium carcinus, M. crenulatum, M. faustinus, and M. heterochirus can move longer distances than smaller individuals of Atya lanipes, and Xiphocaris elongata. M. carcinus can also move longer distances at night in dry stream channels because their large carapace retains moisture so their gills can use atmospheric oxygen. Individual-based models indicate that the distance between pools strongly predicts local shrimp movements during extremely low flow. Weekly sampling of shrimp at multiple pool sites documents that shrimp movement to upstream pools was restricted during extreme drought in 2015. Both upstream and downstream movements were altered during shorter droughts. These changes in distribution are useful for monitoring ecosystem services provided by shrimps and for anticipating changes in available local water supplies