Gelwick, Frances PPackard, Jane M2015-12-012017-04-072015-12-012017-04-072013-122013-12-06http://hdl.handle.net/1969.1/151923The Guadalupe Bass Micropterus treculii is native to the Texas Hill Country of central Texas. It is distributed across portions of the Brazos, Colorado, Guadalupe and San Antonio River basins. The Guadalupe Bass is threatened by hybridization with non-native smallmouth bass Micropterus dolomieu. Because pure bred Guadalupe Bass are increasingly harder to find in areas where Smallmouth Bass have become established, Texas Parks and Wildlife Department developed a captive spawning program for Guadalupe Bass for supplemental stocking to counter the influence of hybridization. To determine potential mechanisms influencing hybridization in Guadalupe Bass populations, objectives were: (1) characterize nesting habitat and behavior, (2) compare courtship behaviors in native and hatchery environments, and (3) identify behaviors potentially influencing genetic diversity in offspring of hatchery fish. Initial field studies included snorkeling and visual surveys conducted during September and November in 2012 in Gorman Creek, South Llano River, Pedernales River, and the Guadalupe River; no active nests or reproductive adult Guadalupe Bass were observed. During February through May of 2013, visual surveys were repeated at the four field sites. In addition courtship and spawning behavior of Guadalupe Bass were recorded at A.E. Wood Hatchery. In both hatchery and natural environments, previously undocumented reproductive behaviors were observed. Breeding color patterns of males and females became more differentiated, aggressive behavior of males included opercular flaring and jaw locking, and individual males courted multiple females simultaneously and syntopically at nest sites. Only 50% of the available nesting mats were used because of the monopolization of females and nest sites by a few males. Frequencies were significantly different for several male and female behaviors when comparing hatchery to natural environments. The prototypical courting and spawning sequence of the Guadalupe Bass were visually represented in kinematic diagrams. Although behavioral sequences were similar in hatchery and natural sites, certain transition probabilities differed. Potential mechanisms for hybridization were: similar color pattern changes in males and females of both species, female preference in both species for larger males, similar use of nesting habitat in both species, similar reproductive behavioral repertoire, and the monopolization of nesting sites and females by males.enGuadalupe BasscourtshipspawninghybridizationThesis