Abstract

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Koehle, J.J. 2006. The effects of high temperature, low dissolved oxygen, and asian tapeworm infection on growth and survival of the Topeka shiner, Notropis topeka. M.S. Thesis, University of Minnesota. 44 pp.

Abstract:

The Topeka shiner (Notropis topeka) is an endangered fish species, historically described as inhabiting cool, headwater prairie streams. However, Topeka shiners recently have been found in off-channel habitats with high temperatures and low dissolved oxygen levels. To determine if Topeka shiners can tolerate conditions in these off-channel habitats for extended periods of time, I determined their critical thermal maximum (CTM), optimum temperature for growth, and lower lethal dissolved oxygen level (96hr LC50). Also, I studied the effects of reduced oxygen as well as Asian tapeworm infection (Bothriocephalus acheilognathi) on growth. Topeka shiners have a CTM of 39 C at a 31 C acclimation temperature and their optimum temperature for growth is about 27 C. Topeka shiners are capable of growth at dissolved oxygen concentrations as low as 2 mg L-1, but in some circumstances at a considerably lower rate than at dissolved oxygen concentrations at or above 4 mg L-1. Their 96-hour LC50 for dissolved oxygen at 26 C is 1.2 mg L-1. Finally, growth is reduced by the presence of Asian tapeworms. Asian tapeworm is not only a threat to fish health but use of infected fish in restoration programs is prohibited. Overall, temperature and oxygen are probably not responsible for Topeka shiner population declines and are not limiting factors in most off-channel habitats. Judging by the abundance of Topeka shiners in off-channel habitats, these habitats may be population sources, rather than sinks, and thus may be important to Topeka shiner populations.

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