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Home range, spatial dynamics, and growth of Moapa dace (Moapa coriacea)
AuthorHereford, Mark Earl
AdvisorPeacock, Mary M.
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Moapa dace (Moapa coriacea) is an endangered thermophilic minnow (Family: Cyprinidae) native to the upper Muddy River which originates at geothermal springs in southeastern Nevada, USA. Historically Moapa dace occupied tributaries and the main stem of the Muddy River totaling 18 kilometers of stream habitat near the geothermal sources where water temperatures are between 26.0°C and 32.0°C. Due to habitat fragmentation, water diversion, and invasive species introductions during the early and mid-1900's Moapa dace populations drastically declined. In 1997, following the invasion of the non-native blue tilapia (Oreochromis aureus), a fish barrier was installed isolating three tributaries from the main stem of the Muddy River for the protection of native aquatic organisms above the barrier. During this study Moapa dace were restricted to stream habitat above this barrier totaling 2.8 kilometers. The goals of this study were to determine the home range size, spatial dynamics, and growth of Moapa dace in these three tributaries of the Muddy River. A mark-recapture method using baited minnow traps was implemented and genetic tagging of individuals based on their unique genotypes using ten polymorphic microsatellites was used to identify individuals over a three year period (October 2009 - September 2012). Using geographic information systems (GIS) I was able to demonstrate that home range density (number of individual home ranges per square meter) was most restricted in a fragmented tributary and home range density increased in a tributary immediately following stream habitat restoration. Mean home range length of individuals increased in the last year of this study (141.3 meters), was greatest in the largest tributary (215.2 meters), and was the least in the fragmented tributary (70.5 meters). Growth rates of Moapa dace drastically decline in individuals over 40 mm (fork length), are highest between May and July, and lowest between September and November. Using Fulton's body condition factor (K=W/L3) two distinct periods of low (January - March) and high (May - November) body condition were discovered. Growth rates and body condition were both significantly higher in individuals with home ranges over 25 meters. The results of this study suggest that Moapa dace will immediately occupy stream habitat that has been recently restored to increase stream velocities and re-emphasizes the importance of habitat connectivity as it relates to an individual's ability to maximize energy intake.