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- Title
On the relative importance of pool morphology and woody debris to distributions of shrimp in a Puerto Rican headwater stream
- Authors
Covich, Alan P.; Black, Robert W.; Pyron, Mark
- Abstract
In this paper, we report the sizes and distributional orientation ofwoody debris in a headwater rainforest stream in the Luquillo Experimental Forest (LEF), Puerto Rico. We also provide results of a 4-month study of a wood addition experiment designed to increase cover for benthic macroinvertebrates (freshwater shrimp). We added branch-sizedwoody debris to 20 pools in three streams. We trapped four species of freshwater shrimp (two species of benthic detritivores and two predatory shrimp species) during each of the 4 months following wood additions. An analysis of pool morphology (maximum depth, surface area and volume) provided a useful predictor of shrimp abundances. In general, numbers of shrimps increased with sizes of stream pools. A repeated measures ANOVA demonstrated no effect of woody debris additions on total numbers of shrimp per pool area. Two detritivore species (Atya lanipes, a filter feeder and Xiphocaris elongata, a shredder) decreased in abundance with increased woody debris and there was no statistical relationship between woody debris additions and predators ( Macrobrachium carcinus and M. crenulatum). Small woody debris additions may have altered flow velocities that were important to filter-feeding Atya at the microhabitat scale, although the overall velocities within pools were not altered by wood additions. Lower numbers of Atya andXiphocaris in two of the three streams may result from the occurrence of two predaceous fishes (American eel and mountain mullet) and more predatory Macrobrachium in these streams. One likely interpretationof the results of this study is that the stream pools in these studyreaches had sufficient habitat structure provided by numerous rock crevices (among large rocks and boulders) to provide refuge from predators. Addition of woody debris did not add significantly to the existing structure. These results may not apply to stream channels with sand and gravel substrata where crevices and undercut banks are lackingand w
- Subjects
PUERTO Rico; RIVER ecology; SPECIES distribution
- Publication
Hydrobiologia, 1999, Vol 405, Issue 1-3, p207
- ISSN
0018-8158
- Publication type
Article