Tropical island watersheds are typically less diverse than watersheds on larger mainlands (Covich and McDowell 1996). These unique environments are home to a host of diadromous species, which spend different life stages in salt and fresh water. Located in northeastern Puerto Rico, the Caribbean National Forest receives an average of 300-400 centimeters of precipitation annually and supports a number of watersheds. As one of the largest, the Río Espíritu Santo is important for human recreation and water supply. This watershed is home to predaceous eels, omnivorous mullets, four species of gobiid fishes, two species of grazing gastropods, eleven species of decapod crustaceans (ten shrimp and one crab species), and over sixty species of aquatic insects (Covich and McDowell 1996). Distributions of these species are limited by the placement of waterfalls along streams and by competition, predation, and resource availability (Covich and McDowell 1996). Because of high, often unpredictable precipitation in the area, the Río Espíritu Santo and its tributaries are prone to frequent floods, and the species that inhabit the area are adapted to highly variable conditions in flow regimes. Three genera of decapod shrimp have been observed in Puerto Rican watersheds. These shrimp are amphidromous, a term that describes species that spend portions of their lives in both salt and fresh water for purposes other than breeding. Typically, adult shrimp release their eggs in high mountain streams, after which they wash downstream into estuaries and hatch into larvae. After metamorphosis, these larvae migrate into higher elevation rivers and streams where they spend the majority of their lives (March et al. 1998). Many of these shrimp species have developed the ability to move on land during migration, and are capable of navigating over the many waterfalls that characterize these streams (Covich and McDowell 1996). Their dependence on a variety of habitat types over their life cycle makes these shrimp especially vulnerable to changes in flow regimes and human alteration of the watershed. Five species of Macrobrachium are found in Puerto Rico (M. acanthus, M. carcinus, M. crenulatum, M. faustinum, and M. heterochirus). Macrobrachium are omnivorous and are known to consume algae, detritus, insects, and smaller shrimp as food (Covich and McDowell 1996, March et al. 2002, March and Pringle 2003). Urban development and human water use are expanding rapidly in Puerto Rico. As the human population grows, it is important to determine present and future effects of roads, dams, fishing, and other recreational activities on watersheds. Macrobrachium carcinus is the largest species of shrimp in Puerto Rico, and its predatory nature and use of a variety of habitats over its lifespan make it an ideal indicator of watershed health. Efforts to quantify and monitor this species will be useful in assessing future impacts as well as furthering current scientific knowledge. Macrobrachium carcinus is highly regarded by fishermen, who use traps, hooks and lines, nets, spears, spear guns, and poisons (such as bleach) to capture it (Greathouse et al. 2005). A few methods have been successfully used to capture Macrobrachium for data collection, but no previous effort has been made to determine the relative efficiencies of such methods, most of which involve the use of modified traps built for fish. Local fishermen usually employ burnt coconut as bait for the large shrimp, while researchers favor cat food for its ease of use. As part of this study, we compared the relative efficiencies of two different trap types (modified minnow traps and wire mesh traps crafted by local fishermen) and three bait types (chicken intestines, cat food, and burnt coconut) for capturing Macrobrachium carcinus. Due to input from experienced local fishermen, we hypothesized that burnt coconut would be superior to the other bait types in terms of total number of M. carcinus captured.