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Wednesday, June 6, 2007 - 11:30 AM
251
The effects of a herbivorous fish Pseudogastromyzon myersi (Balitoridae) on benthic algae in Hong Kong streams
Yao Yang1, Yixin Zhang2, and David Dudgeon1. (1) Department of Ecology and Biodiversity, The University of Hong Kong, Hong Kong, Hong Kong, (2) Department of Biology, Texas State University, San Marcos, TX
Regular surveys and manipulative experiments were conducted to investigate the effects of the herbivorous fish Pseudogastromyzon myersi on benthic algae in pools of two shaded and two unshaded Hong Kong streams. Open and exclusion cages containing stones from the stream bed were employed to control the presence and absence of P. myersi. Stones collected from the stream bed (no cage treatment) were used to control for any potential cage effect.
Algal biomass in unshaded and shaded streams was rather similar, as were fish densities, with the exception of one shaded stream where P. myersi abundance was <50% that in the other 3 streams. ANOVA revealed that at the end of a 4-week experiment, algal biomass was significantly higher (60% and 70% on average) in the exclusion cages in the two unshaded streams but not in the two unshaded streams. There was no difference between open cage and no cage treatments, indicating the lack of cage effect and good experimental realism. Inorganic sediment accumulation was not generally different among any of the treatments. The results suggest that P. myersi grazing has a measurable impact on benthic algal biomass but not strong effect on sediment accumulation.
Algal biomass in unshaded and shaded streams was rather similar, as were fish densities, with the exception of one shaded stream where P. myersi abundance was <50% that in the other 3 streams. ANOVA revealed that at the end of a 4-week experiment, algal biomass was significantly higher (60% and 70% on average) in the exclusion cages in the two unshaded streams but not in the two unshaded streams. There was no difference between open cage and no cage treatments, indicating the lack of cage effect and good experimental realism. Inorganic sediment accumulation was not generally different among any of the treatments. The results suggest that P. myersi grazing has a measurable impact on benthic algal biomass but not strong effect on sediment accumulation.
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