Original paper

Distribution of juvenile crabs (Epilobocera sinuatifrons) in two Puerto Rican headwater streams: Effects of pool morphology and past land-use legacies

Zimmerman, Julie K.H. Covich

Abstract

Headwater streams in the Luquillo Mountains of Puerto Rico support eight species of omnivorous freshwater decapods. One of the most abundant predatory decapods is the freshwater crab, Epilobocera sinuatifrons. We studied the distribution and pool-habitat occupancy of juvenile E. sinuatifrons in two headwater streams located in the Forest Dynamics Plot of the Luquillo Long Term Ecological Research Site in northeastern Puerto Rico. We compared crab distributions along Quebrada Toronja, which was bordered by pasture more than 80 years ago, to distributions along a second stream, Quebrada Prieta, where the forest has remained intact and past disturbance was minimal. We tested the hypothesis that a legacy of past land-use had sufficiently modified the stream channel substrata and riparian forests along the Quebrada Toronja to the extent that juvenile crab abundance and habitat preferences would be affected. We selected nine study pools along 300m of Quebrada Prieta and eleven pools along 300 m of Quebrada Toronja, and periodically sampled each pool for juvenile crabs as well as physical habitat (water depth, volume, velocity and substrate characteristics). Juvenile crabs were abundant in all pools, but were more abundant along the Prieta, which also had greater variation in pool habitat compared to Toronja. Crab abundance in Prieta pools was correlated with higher water velocity and large substrate (boulders and rocks), whereas crabs in the Toronja were correlated with higher flows. This is the first report of habitat-specific distributions of neotropical freshwater crabs in response to past land uses.

Keywords

neotropical crabsomnivorous crabshabitat choiceland-use effects.