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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology I
EXTREME FLOW FLOWS IN PERENNIAL MONTANE TROPICAL STREAMS: EFFECTS ON MIGRATORY FRESHWATER SHRIMP.
A.P. Covich1, T.A. Crowl2, and F.N. Scatena3. 1Fishery and Wildlife Biology, Colorado State University, Fort Collins, Colorado, USA 80523, 2Department of Aquatic, Watershed, and Earth Sciences, Utah State University, Logan, Utah, USA 84322, 3International Institute of Tropical Forestry, U.S.D.A. Forest Service and University of Puerto Rico, Rio Piedras, Puerto Rico, USA 00928
Perennial rainforest streams characterize the Luquillo Mountains of Puerto Rico. However, unusually low rainfall in 1994 caused pools to be reduced in volume. Some headwater riffles dried out completely, resulting in disconnected pools and reductions in accessible habitats. We sampled shrimp populations bimonthly from 305 to 480 m in elevation along 1200 m of Quebrada Prieta, a second-order stream in the Luquillo Experimental Forest. Following contraction of pools, densities of Atya lanipes increased from 22 to 75 shrimp m-2 of pool area and Xiphocaris elongata increased from 5 to 14 shrimp m-2. A smaller percentage of adults of both species were gravid during the drought. Following the drought (1995-1998), densities of both shrimp species and reproductive activity of Atya returned to pre-drought (1990-1993) levels. The percent of gravid Xiphocaris remained lower than in the pre-drought period. Droughts coupled with increasing societal demands for fresh water leads to extreme low flows and negatively affects the shrimps’ ability to migrate from estuaries to headwater pools. Increased intensity and duration of drought in the Caribbean could limit upstream migrations of shrimps and reduce the abundance of shrimps in many headwaters. Some of these accessible streams are also increasingly subject to harvest by recreational visitors and local residents.
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