Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Includes bibliographic references.

Although the evolutionary implications of natural differences in flow regime have been well-studied, the evolutionary implications of anthropogenic modification of flow regime are not well understood. To begin to characterize the evolutionary consequences of dam construction for small stream fishes, I conducted four related studies focused on the blacktail shiner (Cyprinella venusta). First, to characterize natural variation in body shape related to stream characteristics, I assessed the extent to which body shape corresponded to three environmental factors, phylogeny, and body size. Morphology was predominantly associated with variation in mean annual runoff; phylogeny was also a strong predictor of morphology. In contrast to previous studies that emphasize the importance of water velocity, these findings indicate that morphological variation is tightly linked to more complex aspects of hydrology and evolutionary history. Second, to initially characterize variation in body shape associated with dam construction, I compared the body shape of C. venusta from pairs of river and reservoir sites. River populations differ from reservoir populations in several aspects of morphology, demonstrating that reservoir characteristics drive changes in the morphology fish populations. Third, to characterize the pace and trajectory of phenotypic responses to impoundment, I examined a chronosequence of museum specimens originating from a reservoir and nearby stream. The rate of change in larger individuals was greatest in the first 15 years following impoundment, with less pronounced shifts in smaller individuals and no shift in the morphology of stream individuals. These results indicate that morphological responses to impoundment are decadal-scale and attenuate. Fourth, to determine if impoundment-related morphological shifts are genetically determined and are functionally significant, I conducted swimming performance trials with common garden C. venusta originating from reservoir and stream parents. Common garden juveniles exhibited differences in morphology similar to those between wild-caught individuals, indicating that morphological divergence following impoundment is an outcome of rapid evolutionary change. Offspring did not differ in swimming performance, suggesting that morphological evolution may be driven by reproductive or trophic shifts following impoundment. Together, these studies demonstrate that impoundment is a potent evolutionary force on fishes, but the mechanisms by which it does so remain relatively unknown. / acase@tulane.edu

Biological invasions are a global threat to aquatic biodiversity. Of particular concern are invasive freshwater fishes because they have high establishment rates, and introductions can result in the displacement and extirpation of native species through a range of processes including competition and hybridization. Though it is well known that invasive freshwater fishes commonly spread following introduction events, little is known about how fast and far they may move. Additionally, observations of hybridization involving invasive stream fishes have been linked to elevated turbidity; however, the extent to which impaired water clarity influences reproductive isolation among invasive and native species remains poorly understood. To better understand how invasive freshwater fishes disperse, and how turbidity affects reproductive isolation between native and non-native species, I carried out a series of three related studies. First, I evaluated genetic variation across the native and invasive ranges of red shiner (Cyprinella lutrensis), throughout the United States. Second, I characterized genetic variation and clinal stability across a hybrid swarm involving native blacktail shiner (Cyprinella venusta stigmatura) and invasive red shiner in the Upper Coosa River Basin (UCRB), USA. Third, I examined whether turbidity influences pre-mating social interactions between invasive red shiner and native blacktail shiner. MtDNA haplotypes from native range populations of red shiner form four divergent lineages and suggest that introduced populations in the western and eastern US originate from dissimilar genetic lineages. I also recovered a previously undescribed lineage of Cyprinella that has been cryptically introduced into the western US. Examination of the hybrid swarm in the UCRB revealed that the proportion of hybrids increased between 2005 and 2011, and that the hybrid swarm is continuing to expand both upstream and downstream. Under turbid conditions, I found that pre-mating social interactions increased, and that native blacktail shiner females are especially likely to interact with invasive red shiner males. Localized control or removal may be effective in managing non-native red shiner; further monitoring, however, is needed to help identify additional factors contributing to hybrid swarm movement. Furthermore, integrating knowledge of species behavior into management planning could help deter the further establishment and spread of invasive red shiner. / acase@tulane.edu

The goal of this research was to develop captive propagation methods for the Federally threatened spotfin chub, Cyprinella monacha, and yellowfin madtom, Noturus flavipinnis, by using closely related, but unthreatened species, to evaluate potential techniques. The surrogate species used were the whitetail shiner, Cyprinella galactura, and the margined madtom, Noturus insignis. I investigated methods to promote gonadal maturation, induce spawning, and rear larvae of these fishes. Captive whitetail shiners developed mature gonads under a variety of temperature and photoperiod conditions. Spawning condition was maintained for over two years when they were held at constant warm temperature (≈ 24 C) and long photoperiod (16 h light). Whitetail shiners did not readily spawn in aquaria, but were induced to spawn by hormonal injection with human chorionic gonadotropin (hCG) and carp pituitary extract (CPE) at mean dosages of 1688 I.U./kg and 20 mg/kg, respectively, or with luteinizing hormone releasing hormone analogue (LHRHa) and domperidone at mean dosages of 363 µg/kg and 36 mg/kg, respectively. Most females spawned within 30 h of the first injection. Stripped ova were effectively wet-spawned, and larvae hatched in 8 d at 25 C. I obtained a mean hatch rate of 55 %, but lack of swimbladder inflation resulted in very poor survival of several batches of eggs. Larvae began feeding within 2 d of hatching, and survival rates of 50 to 90 % after 16 d were obtained when larvae were fed twice daily on a diet of brine shrimp nauplii at a rate of ≈ 10/L/d, and a commercially prepared larval fish diet at a rate of ≈ 14 mg/L/d. Changing photoperiod, but not temperature, was required to induce oocyte maturation in most captive female margined madtoms. Sperm production in mature male madtoms was enigmatic; motile sperm were observed only once. Plasma testosterone concentrations in males peaked just prior to the spawning season at 6.5 ng/mL, but levels were not correlated with male gonadosomatic values. Plasma 17β-estradiol levels in females peaked just prior to the spawning season at 15 ng/mL, and were correlated with gonadosomatic values. Captive margined madtoms did not tank spawn unless they were hormonally injected with hCG and CPE at mean dosages of 5256 I.U./kg and 58 mg/kg, respectively, or with LHRHa and domperidone at mean dosages of 554 µg/kg and 55 mg/kg, respectively. Most females ovulated within 78 h of the first injection. Inclusion of more than one breeding pair per tank inhibited tank spawning. Embryos did not develop in 55 % of tank-spawned ova, or from any strip-spawned ova. Parents consumed spawned egg masses if they remained with the nest. Hatch rates > 65 % were obtained by suspending egg masses in a large-mesh basket over turbulent aeration at 28 to 30 C. Larvae hatched in 7 d at 28 C. Survival rates > 50 % after 15 d were obtained when larvae were fed salmon starter twice daily at a rate of 20 mg/L/d, and tanks were thoroughly cleaned daily. / Ph. D.