Quantitative effects of atyid shrimp (Decapoda: Atyidae) on the depositional environment in a tropical stream: Use of electricity for experimental exclusion.
Abstract: Effects of biotic (shrimp) and abiotic (discharge) factors on the
depositional environment were quantified in a montane stream in Puerto
Rico. Electricity was used experimentally to exclude large
(approximately >1 cm in length) biota without artificially
increasing sedimentation as in cage enclosure/exclosure experiments in
stream systems. Shrimp (>1 cm in length) were excluded from rock
substrata by semicircular fences hooked up to battery-powered fence
chargers which emitted continuous pulses of electricity. Unelectrified
control substrata had natural high densities of atyid shrimp.
Significantly greater masses of total sediment, fine and large organic
particles, and algal biovolume occurred in shrimp exclusion treatments
relative to controls. Shrimp exclusion treatments experienced slow and
steady accumulation of sediments under base flow conditions and a large
stepwise increase in sediment weight following a storm. No measurable
sediment accrued in the presence of natural densities of shrimp under
base flow conditions. Shrimp rapidly removed sediments that accrued
during the storm (440-620 g.m(2) dry mass(-1)), decreasing sediment
mass in control treatments to near prestorm levels (5-13 g.m(2) dry
mass(-1)) within 30 h. Atyid shrimp can significantly affect the
accumulation of organic and inorganic materials on rock substrata in
stream pools between high-discharge events.
Pringle, C. M., and G. A. Blake 1994. Quantitative effects of atyid shrimp (Decapoda: Atyidae) on the depositional environment in a tropical stream: Use of electricity for experimental exclusion. Canadian Journal of Fisheries and Aquatic Sciences 51: 1443-1450.
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