Habitat associations of the sharpnose shiner Notropis oxyrhynchus in the upper Brazos River, Texas

ISSN： 0270-5060

Source： Journal of Freshwater Ecology, Vol.28, Iss.4, 2013-12, pp. : 453-461

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Abstract

Habitat associations of sharpnose shiner (Notropis oxyrhynchus) in the upper Brazos River, USA, were studied over a two-year period. We used generalized linear models with a logit link to assess the influence of individual physical and chemical habitat variables on the presence of sharpnose shiner at the microhabitat scale. Our models indicated that depth was the only habitat variable that significantly predicted sharpnose shiner presence during the first year of the study and that current velocity was the only variable that significantly predicted sharpnose shiner presence during the second year. Monthly plots of fitted regression estimates superimposed over frequency distributions for both significant variables revealed a distinct pattern of habitat use related to habitat availability. When only a narrow range of depths and current velocities was available, sharpnose shiner occurred more frequently in deeper and swifter microhabitats. In contrast, during periods with the greatest depths and current velocities, sharpnose shiner presence decreased with increasing depth and current velocity. Our results suggest that sharpnose shiner in the Brazos River exhibits habitat preferences but these preferences are conditional, based on the range of habitats available on a given date.