Abundance of Boyeria vinosa larvae in the Enoree River basin, USA: chemical, physical, and biological correlates (Odonata: Aeshnidae)

Abstract

Boyeria vinosa is a common anisopteran in the southeastern United States. Here we describe relationships between the abundance of B. vinosa larvae and the chemical, physical and biological properties of the Enoree River of South Carolina and nine of its tributary stream systems. Chemical profiles were conducted weekly for seven weeks at 63 sites in May-July 1999 and at 64 sites in May-July 2000. Fish, salamanders, crayfish, and odonate larvae were collected once at each site by electrofishing and seining, and were counted, sorted, and preserved. The abundance (number/sample) of B. vinosa was positively correlated with stream means for pH, bicarbonate, silicon, magnesium, and calcium (p < 0.01). Also, B. vinosa were more abundant in streams with a higher frequency of sandy bottoms sites (r = 0.622, p = 0.05). At the site scale, sites with B. vinosa had significantly more crayfish, fish, and other odonates, higher pH, and dissolved oxygen, and less chloride than sites without B. vinosa (Mann-Whitney U tests, p < 0.05). Where B. vinosa were present, abundance was positively correlated with fish abundance, odonate abundance, pH, conductivity, and concentrations of sodium, calcium, magnesium, bicarbonate, bromine, silicon, and aluminum (p < 0.05). As such, larval abundance of B. vinosa was strongly correlated with chemical and physical parameters at both site and stream scales, but only covaried with the abundance of other organisms at the site scale. Larval abundance did not correlate with the abundance of predatory centrarchid fish at either scale.

Keywords: Odonata, dragonfly, Boyeria, habitat selection, water quality, water pollution

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