Biodiversity of riverine fish: Patterns in species association with habitat and the divergence of species
2002
Beamish, F.W.H.(Burapha University, Chon Buri (Thailand). Faculty of Science. Department of Biology)
Ecological information has been collected for lotic regions from three watersheds, Huai Kayeng, Huai Ban Rai and Huai Phacham Mai, in Thong Pha Phum between March and July, 2002. The 26 sites were selected from first (n=8), second (1), third (8) and fourth (1) order streams and ranged in area from 2 to over 300 square m with a mean (+-SD) of 118+-85 square m. Physical and chemical characteristics measured include stream width, depth, velocity, discharge, riparian cover and composition, light intensity at the water's surface, substrate particle size and organic content, temperature, true color, turbidity, conductivity, total hardness, pH, oxygen, ammonia, nitrite, nitrate, phosphate, total phosphorus, total iron, silica and alkalinity, with most displaying a wide concentration range. Silica is particularly high. Total fish abundance, estimated from sequential electrofishing passes over an enclosed habitat, varied from 0.2 to 16.4 fish/ square m with a mean (+-SD) of 2.3+-3.3 fish/ square m, equivalent to 899+-1791 fish/100 m of stream length, regardless of width. Biodiversity was positively related to stream width and ranged from 1 to 18, with a mean of 1+-4 species/site. Overall 51 fish species have been identified with a few not yet identified. Temporal changes in fish assemblage structure is being examined through changes in diet and morphology, especially within feeding guilds. Benthic invertebrate composition and structure is being examined also at each site from five randomly located Surber samples as well as from collections made by drift and dip net. Over 60 insect taxa have been recorded along with significant numbers of mollusks and decapods. Currently, these taxa are undergoing finer classification, ideally to the level of species or genus. Highest and lowest invertebrate diversity and density have been 37 and 10 taxa and 1472 and 175 individuals/ square m, respectively.
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