These migratory shrimp were filmed in the Peje River, along the border of La Selva Biological Station in April of 2009 by aquatic ecologist Dr. Marcia Snyder. She studied them by measuring their habitat preferences, densities, growth rates and secondary production. She used capture mark recapture technique to estimate their densities and growth rates. Shrimp are largely nocturnal to avoid predators that like to eat them including otters, caiman and fish. During the day, they are often found hiding under rocks or leaves. They are strong swimmers, migrating more than 50 km to reach this site from the ocean and have well developed escape mechanisms, as are displayed at the end of this video.
Migratory shrimps are an important component of the aquatic fauna in many regions of the new and old world tropics. Freshwater shrimps are speciose (655 species) and are distributed in every biogeographic province in the world. Atyidae and Palaemonidae families are the most numerically dominant of the freshwater shrimp species, which comprise 25% of the Caridea sub-order. Fifty-three species of Macrobrachium (Palaemoinidae) occur in the neotropics. The majority of Macrobrachium spp. display a form of diadromy know as amphidromy; their larvae require saltwater to develop even though they spend most of their lives in freshwater. Amphidromous shrimp are functionally important components of stream ecosystems and play key roles in food web stability, organic matter processing, and nutrient cycling. The shrimp in the video, Macrobrachium olfersi and Macrobrachium carcinus can be found from Brazil up through Central American and into lower North America (e.g. Florida and Texas). They are usually nocturnally active and exhibit cryptic coloration. M. olfersi and M. carcinus are omnivorous and their diet can include algae, insects, detritus and fish.