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This project focused on the relationship between instream flows and smallmouth buffalo (Ictiobus bubalus) recruitment in the Gulf Coastal Plain of Texas. The flow regime is the dominant factor in lotic systems and, consequently, the relationship between instream flows, including impacts to natural flow regimes, and life-history is a subject of growing interest. Smallmouth buffalo is a good model to investigate the relationship between river flows and variable interannual recruitment success of periodic life-history strategist fish species. Smallmouth buffalo were collected from the Brazos, Colorado, and Guadalupe Rivers of Texas, U.S.A., and otoliths were extracted from individuals in the field and sectioned and photographed in the lab. Photographs of sectioned otoliths were used to estimate age and thus the year in which the individual was spawned by counting back from the time of capture. Population age structure (i.e. a ‘state' or condition at a point in time) was used to infer effects of flow variation on a rates-based process (i.e. recruitment). After controlling for mortality using recruitment index values, interannual variation in recruitment was modeled using multiple components of the flow regime quantified as indicators of hydrologic alteration (IHA) variables based on daily discharge data from USGS gaging stations in each river system. Model selection followed a two-tier approach, first fitting models using only flow attributes associated with the spawning season then adding additional informative parameters from the pre-spawn and post-spawn periods. The primary finding from model selection was that duration of high flow pulses during the spawning season is a critical component of the flow regime associated with successful Smallmouth Buffalo recruitment. These findings have implications for river management and conservation of ecological integrity, in particular populations of periodic life-history strategist species.

The Ogallala Formation is an accumulation of fluvial and lacustrine sediments deposited in the high plains of North America during the middle Miocene to early Pliocene. Most famous for its highly diverse mammalian fauna, the Ogallala Formation also represents an important record for aquatic taxa as well, including in Oklahoma Atractosteus, ?Esox, Ictalurus, Micropterus, ?Aplodinotus, Alligator, turtles, mollusks, freshwater sponges, and diatoms. Here, I describe a new species of buffalo fish (genus Ictiobus) based on a fossil from the Late Miocene (Clarendonian) of western Oklahoma. This specimen was found in a diatomite derived from a brackish lake (due to underlying Permian salt beds), discovered in approximate articulation, upside down, and lacking the caudal half of the postcranial skeleton. The skull preserves roughly 28 elements, along with remnants of the dorsal spines, fin rays, and multiple cycloid scales covering portions of the skeleton. The opercular series on each side lay open, with the dorsal skull bones (frontal, parietal, and supraoccipital) remaining in full articulation. The dentary, premaxilla, and other rostral skull bones are deflected laterally and preserved next to elements of the skull roof. Generally, the bones are well-preserved except where a dense root mass plane has intersected the skeleton and top of the skull. The genus Ictiobus is represented by five extant species: I. bubalus, I. cyprinellus, I. labiosus, I. meridionalis, and I. niger, ranging from Central America to Canada, as well as one Pliocene species, I. aguilerai from Hidalgo, Mexico. The new Oklahoma species can be differentiated from the living and fossil species based on its serrated cleithrum, the large shelf on the anterior end of the gnathic ramus, and the sharp angular interior margin of the preopercle. The addition of this new species adds valuable data for the early evolution of the genus, including potentially important implications for the biogeography of living Ictiobus. I. phyllisae n. sp. is the oldest known species of Ictiobus; it is most closely related to fossil I. aguilerai; the two form a clade with extant I. bubalus. Given the Clarendonian age (about 12 Ma) of I. phyllisae n. sp., initial cladogenesis within Ictiobus began well back in the Miocene.

Several species of fishes have been introduced into the Santa Clara River system in southern California, including Catostomus santaanae (Santa Ana sucker), Catostomus fumeiventris (Owens sucker), Gila orcutti (arroyo chub), and Pimephales promelas (fathead minnow). These species are known to inhabit similar ecological niches but little is known about their associated parasite fauna. Two C. fumeiventris, 35 C. santaanae, 63 hybrid catostomids, 214 G. orcutti, and 18 P. promelas were collected and necropsied in the summers of 2017 and 2018. Nine macroparasite taxa were harvested including seven native, and two nonnative parasites Schyzocotyle acheilognathi (Asian fish tapeworm) and Lernaea cyprinacea (anchor worm). Prevalence and intensity of parasites were not related to the genetic history of these catostomids. This is the first host-association record for G. orcutti with Gyrodactylus sp., S. acheilognathi, diplostomid metacercariae, Rhabdochona sp, Contracaecum sp., and larval acuariid cysts and for P. promelas with larval acuariid cysts.

Abstract: Extant catostomid fishes occupy diverse aquatic ecosystems and niches in North America (NA). Less than 3% of catostomid taxonomic richness, or two species, are found outside of NA in Asia. Such adjunct and unbalanced distribution pattern has been established since the late Oligocene, when catostomids disappeared from Asia and became common fishes in NA. Eocene catostomids, representing the oldest fossil records of this family, reached relatively high taxonomic richness in both NA and Asia, and thus are critical to understand evolution of catostomids. This thesis is a study of about 3000 specimens of Eocene catostomids and problematic catostomids. Osteology of 33 extant catostomid species and 11 other otophysans are examined for comparison. Morphological characters are acquired through microscopic examination and CT scans. Cladistic analyses using the parsimony criterion are performed in PAUP 4b10 and TNT 1.5, and explored in MrBayes on XSEDE (3.2.6) using model-based Bayesian inferences through the CIPRES Science Gateway. Analyses of body shape changes and variations of Eocene catostomids are performed using the landmark-based geometric morphometric method. Body shapes of laterally preserved complete fish are captured using surface scanning and digitized with landmarks in TPS utility and TPS dig2, then analysed in MorphoJ 1.06C. First, taxonomy is clarified for Eocene catostomids and problematic catostomids. Of the NA taxa, Amyzon gosiutense, a previously hypothesized junior synonym of A. aggregatum, retains its specific status based on a suite of osteological features. “NewGenus” brevipinne is revised from the nominal Amyzon brevipinne and represents the first known shallow bodied, small sized, fluvial-sediment derived, and loach-like catostomid genus. Of the Asian taxa, Jianghanichthys hubeiensis, which was firstly assigned to Osteochilus of Cyprinidae and later Catostomidae, is suggested to be a stem cypriniform based on osteological comparison and phylogenetic analysis. The first fossil family of Cypriniformes, Jianghanichthyidae, is erected to contain the species. Additional problematic catostomids, which were described as Eocene Osteochilus from south China, are assigned to Jianghanichthyidae and combined into two species: Jianghanichthys sanshuiensis and J. linliensis. New species Amyzon kishenehnicum and Jianghanichthys huachongensis are described from NA and Asia, respectively. Second, the systematic position and intrarelationships of Eocene catostomids were largely unresolved before this study, although they are critical to understand the evolution of the family and Cypriniformes. Three sets of phylogenetic analyses based on different character sets are performed. The first set vouches that Jianghanichthys doesn't belong to any known cypriniform family, but is a basal clade. The second set finds that Amyzon is a basal clade of Catostomidae instead of a member in the Ictiobinae. The third suite of analyses is optimized by maximally utilizing Eocene species and creating an osteological character list. These analyses suggest that most Eocene catostomids (except Plesiomyxocyprinus) were stem taxa of Catostomidae, and “NewGenus” brevipinne represented the most basal clade. Also, known species of Amyzon are not monophyletic, with Asian A. hunanense and NA A. commune being distinctive basal clades. Another Asian genus Plesiomyxocyprinus is sister to all extant catostomids except ictiobines. Third, Eocene catostomids possess similar general appearances and have highly overlapped meristic and morphometric characters, which caused had taxonomic confusion. Quantitative anatomical comparison in this study (geometric morphometrics) finds significant body shape differences between jianghanichthyids and sampled catostomids, A. aggregatum versus A. gosiutense, and A. aggregatum versus A. kishenehnicum. Regression analysis on Procrustes coordinates and centroid sizes shows that allometry does not significantly affect body shapes differences among well-sampled catostomids and jianghanichthyids. Phylogenetically mapped morphospace indicates evolutionary trajectories and trends of body shape changes are congruent to phylogenetic branches of Eocene catostomids and jianghanichthyids. In sum, all unambiguous oldest cypriniforms are included for discussion (Catostomidae, and Jianghanichthyidae of this study plus Cyprinidae). The only area that all oldest cypriniforms are found is south Asia, which suggests that area is the hotspot of origin and cladogenesis of Cypriniformes. Central Asia, including north China, Mongolia, Kazakhstan, and Fareast Russia, where the last remains of catostomid fossils in Asia recorded cyprinids' dispersal route, is a gateway leading to the dispersal events eastward to NA through Beringia and westward to Europe. The mosaic distribution of the Asian taxa across the phylogeny suggests multiple episodes of intercontinental dispersals during the early evolution of catostomids, probably through the freshwater connections of Beringia before the middle Eocene.

Hiwassee River tributaries were frequently occupied by adult sicklefin redhorse Moxostoma sp. during the spawning season; lower reaches of tributaries and Hiwassee River were primarily occupied during the postspawning season; and lower reaches of Hiwassee River were most heavily used during winter. Sicklefin redhorse selected annual, seasonal, and spawning microhabitat non-randomly. Sicklefin redhorse generally were associated with swift thalweg currents, shallow depths, and coarse substrates (e.g., boulder and bedrock) supporting river weed Podostemum ceratophyllum. However, different microhabitats were selected seasonally and during spawning. During 2007, mean daily water temperature for observed sicklefin redhorse spawning was 17.5 °C (11.0–21.1 °C). Male and female sicklefin redhorse conducted spawning migrations simultaneously; however, males tended to occupy spawning tributaries longer than females. All sicklefin redhorse that conducted spawning migrations in both 2006 and 2007 demonstrated spawning tributary fidelity. Foraging was the most common behavior observed for adult sicklefin redhorse with bedrock being the dominant foraging substrate annually. Sicklefin redhorse reproductive behavior was atypical for the genus Moxostoma. An undescribed repetitious post-spawning digging behavior was observed for spawning females. Spawning substrate samples reveal that very coarse gravel and small cobble were dominant spawning substrates. My results increase knowledge pertaining to reproductive ecology, seasonal behavior, and suggest critical management issues important to the life history of the sicklefin redhorse. The spawning migration of black redhorse Moxostoma duquesnei, golden redhorse Moxostoma erythrurum, river redhorse Moxostoma carinatum, sicklefin redhorse and silver redhorse Moxostoma anisurum was sampled with resistance board weirs and prepositioned areal electrofishers (PAEs) during the spring of 2006 and 2007 in Valley River, North Carolina. Spawning was observed for all five redhorse species in 2007 at water temperatures generally ranging from 8–21 °C and mean daily Valley River flows ranging from 1.7–4.5 m3/s. Silver redhorse migrated and spawned first followed by black redhorse, sicklefin redhorse, golden redhorse, and river redhorse with considerable overlap occurring. Male golden redhorse and river redhorse displayed agonistic behavior and spawning site fidelity, while female sicklefin redhorse displayed site fidelity. Silver redhorse and river redhorse were not significantly different (P > 0.05) in size (i.e., total length and weight), while the other redhorse species exhibited a morphological interspecific significant difference (P < 0.05). The spawning migration chronology between males and females was significantly different (P < 0.05) for black redhorse and sicklefin redhorse and not significantly different (P > 0.05) for the other three species; however, spawning migration bounds for both sexes of all five species were similar. All five species typically selected spawning microhabitat non-randomly. Interspecific redhorse spawning site microhabitats were generally significantly different (P < 0.05) due to deviation of one or two species. My findings suggest that seasonal, habitat, and ethological reproductive isolating are functioning within Hiwassee Basin; however, indicate that anthropogenic activities and alterations have the ability to diminish or remove these reproductive barriers. I compared resistance board weirs and prepositioned areal electrofishers to determine gear efficiency for migrating potamodromous fishes. Fish species richness and diversity were higher for PAE total catch, while weir catch had higher species dominance. Total PAE catch by number was much higher than total weir catch; however, PAE total biomass was lower than weir total biomass. Weirs generally did not demonstrate a velocity bias, while PAEs did. On average, PAE mortality was five times higher than weir mortality. My results will assist fisheries managers in selecting the most appropriate gear to address research and management objectives when sampling medium-sized rivers.

Gill rakers in the fish family Catostomidae (Teleostei: Ostariophysi: Cypriniformes) are examined in functional, allometric, and evolutionary contexts. Catostomids are predominantly benthic feeders. Individuals take in a mouthful of substrate and prey, reject the substrate, but selectively retain the prey. Original observations and comparisons with work on Cyprinus carpio indicate that during prey processing the branchial basket and rakers of catostomids function by moving toward the palatal organ (muscular pad suspended from the roof of the pharynx) while bulges form on the surface of the palatal organ, pinching prey between palatal organ and rakers. Water currents then wash away the substrate. A dozen raker parameters were measured in Catostomus commersonii (19--429 mmSL), Ictiobus bubalus (25--309 mmSL), Erimyzon sucetta (41--194 mmSL), and Hypentelium nigricans (39--197 mmSL). Rakers are added until approximately 100 mmSL. Allometric changes in raker number and size are not correlated with ontogenetic niche shifts. Size of the fish is the best predictor of raker parameters, although the exact ontogenetic trajectory may change when rakers are no longer added. Characteristics of the rakers were analyzed within the framework of a phylogeny and comparisons were made between apomorphic (derived) and plesiomorphic states while taking into consideration hypothesized selective regimes. This Homology Approach takes advantage of the individuality of the Catostomini and Moxostomatini lineages to compare evolution as change over time. Twenty-six catostomid species and two cyprinid species were chosen to represent the phylogenetic, morphological, and ecological diversity. Raker width and length of knobs on the surface of the rakers are correlated with prey size, which is consistent with hypothesized action of natural selection. Distance between rakers and distance between knobs are correlated with substrate size, which is consistent with hypothesized action of natural selection. Unknown factors influenced knob height. Raker length and height are correlated with pharynx size. Lateral projections were found to be hypertrophied in some taxa that could effectively sieve prey from the medium. Multiple factors, including phylogenetically inherited traits and natural selection, influenced the evolution of catostomid gill rakers uniquely in different lineages.