Thesis (M.S.)--Marshall University, 2009. / Title from document title page. Includes abstract. Document formatted into pages: contains vii, 54 p. Includes bibliographical references p. 27-30.

Thesis submitted in partial fulfilment of the requirements for the degree Master of Technology: Nature Conservation in the Faculty of Applied Sciences at the Cape Peninsula University of Technology / In the Cape Floristic Region the Olifants- Doorn River (ODR) system is a known biodiversity hotspot in terms of endemic freshwater fish. Eight of the 10 described native freshwater fish species are endemic to this river system. One of the main threats to these fish is predation by introduced predatory fishes. Three species of alien invasive black bass (Micropterus salmoides, Micropterus dolomieu and Micropterus punctulatus) were introduced into the ODR system during the 1930s but prior to this study, their distribution and impacts had never been quantified on a system-wide basis. This study aimed to clarify the current distribution, distribution barriers, predatory impact and best management options for black bass in the ODR system. This was achieved by conducting a system-wide survey of 578 km of stream covering 41 tributaries in the ODR system. Black bass presence was tracked upstream within each tributary to its uppermost distribution point where physical barriers preventing further spread were identified and described. Fish species composition, abundance and size were recorded directly above and below these barriers to quantify black bass impact on the native fish. This research demonstrated that since introduction, natural and human assisted dispersal has facilitated not only the establishment of black bass in the Olifants and Doring main streams but also facilitated the invasions into 22 tributaries. Based on survey results it was estimated that 81.5 % of the ODR system that was previously occupied by native cyprinids is now invaded by black bass. Assessments of native fish abundance and size distribution above and below black bass invasion barriers demonstrated that in invaded tributaries only adults of larger cyprinids (Labeo seeberi, Labeobarbus capensis and Barbus serra) were able to co-occur with black bass species. Smaller fish such as juvenile L. seeberi, L. capensis and B. serra and native minnows (Barbus calidus, Pseudobarbus phlegethon and Barbus anoplus) were absent from the black bass invaded reaches. The findings of this catchment scale study are consistent with findings from other studies in the region. As a result, most native fishes are now restricted to streams above the natural barriers that limit the upstream invasions of black bass. Black bass eradication from invaded reaches is therefore necessary for habitat restoration. Effective eradication will however depend on the presence of barriers to prevent re-invasion from downstream sources. To better understand what constitutes the nature of such barriers, this study characterised the natural barriers that inhibited black bass invasions in 17 tributaries. Natural barriers comprised of 15 waterfalls, two cascades and one chute ranging in height from 0.49 m to 3.5 m with an average vertical drop of 1.21 ± 0.67 m. These findings suggest that black bass have poor jumping abilities and the recommended height of artificial barriers as part of a black bass management program should be between 80 and 100 cm depending on the size of the tributary. As a result, the presence of natural barriers or the construction of artificial barriers to prevent black bass invasions is considered a vital component of native fish conservation projects. Finally, the study assessed the feasibility of black bass eradication from the 22 invaded tributaries in the ODR system based on eight criterion covering aspects of biological, physical, anthropogenic and logistical importance. This assessment showed that effective eradication was most likely only feasible in seven tributaries. Prioritisation of these seven tributaries for black bass eradication based on the threatened status of the resident native species, the land-use in the respective catchments and the tributary length available for rehabilitation indicate that the Breekkrans, Biedouw and Thee Rivers should receive the highest priority.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 186-194).

Subspecies composition and genetic variation are important to the growth and survival of Largemouth Bass and information on these genetic characteristics is required for proper management of the species. In Puerto Rico, a genetic evaluation is needed to develop management plans for Puerto Rico reservoirs and maintain Florida Largemouth Bass at the Maricao Hatchery. Subspecies composition was characterized among reservoirs and the contemporary Maricao Hatchery broodstock in Puerto Rico, and metrics were compared between subspecies and hybrids among reservoir populations. Genetic variation and structure was determined and compared to Largemouth Bass populations in their native range. Florida subspecies were prevalent in all populations and non-introgressed subspecies seemed to be better adapted to the island than introgressed forms. Genetic diversity was lower in Puerto Rico populations and substantial genetic structure among populations was lacking. These results provide genetic information to guide future management and propagation of Largemouth Bass in Puerto Rico.

Two experiments were conducted to investigate the hypothesis that exotic macrophytes alter littoral zone habitat and impact fish that inhabit these areas. The pond experiment was conducted to explore impacts of exotic invasive plants on growth and condition of juvenile largemouth bass (Micropterus salmoides). The second experiment was conducted at a smaller scale in aquaria to simulate an invasion of hydrilla (Hydrilla verticillata) and its influence on juvenile bass foraging. Fish experienced slower growth in the hydrilla treatment than in the diverse, and the ability of bass to capture prey fish was impeded in hydrilla. Juvenile bass growth decreased in habitats containing hydrilla and is likely a result of increased difficulty in capturing quality prey items such as small fish. Results from the two experiments collectively supported my hypothesis that hydrilla growth altered the littoral zone habitat such that foraging was hindered and resulted in slower growth.

The Gray Fossil Site (GFS) preserves an early Pliocene sinkhole pond that accumulated a rich flora and vertebrate fauna. Fossils of fish are incredibly common at GFS, representing thousands of specimens recovered to date. Comparison with extant species reveals a depauperate freshwater fish fauna consisting of only two species: Lepomis sp. and Micropterus sp. The absence of fishes that are ubiquitous in modern streams suggests no perennial surface hydrologic connection between the Gray Fossil Site and the nearby Holston River. Limited opportunities for dispersal into the pond and deleterious conditions such as eutrophy and high competition may have resulted in this extremely low diversity. Examination of articulated and partially articulated GFS fish specimens show mild to moderate degrees of post-mortem disarticulation, suggesting slowed decay likely attributable to cool water temperatures and/or anoxic conditions within the hypolimnion. Preliminary examination of osteological thin sections suggests slow growth in GFS fishes.

Spawning time and habitat of largemouth bass, survival of embryos, and growth and food habits of fingerlings were studied in 1968 and 1969 at Wahweap Bay, Lake Powell. Spawning began in mid- to late-April, when mean daily water temperature at nesting depths was 14.4-15.0 Centigrade (58-59 Fahreheit), and continued until mid-June. Most spawning took place on the northeast shore of the bay. Sandstone rubble was the most commonly used bottom type for nesting, either at the base of ledges or around large sandstone boulders. Mean nest depth increased from 1.63 meter to 4.54 meters (5.36 feet to 14.90 feet) in 1968 and from 1.51 meter to 2.93 meters (4.96 feet to 9.60 feet) in 1969, because bass sought the protection of ledges and boulders covered by continually rising water. Nearly all embryos required 4 days to hatch, and survival to hatching was 80.4 percent and 92.2 percent for 1968 and 1969, respectively. Growth of fingerlings was similar in both years and most rapid prior to August 1 in both years. Fingerlings from the 1969 year-class were longer than those from the 1968 year-class before August 21. Total length of bass on August 21 was 68.0 millimeters in both years but 86.5 millimeters and 80.2 millimeters on October 1 in 1968 and 1969, respectively. Growth may have been influenced by total temperature experience during the early part of the growing season but not during the latter part. Fingerlings ate mostly crustaceans, insects, and fish. Size of organisms eaten increased with increase in fingerling length, and fingerling bass fed selectively on larger Crustacea. Numbers of nests located and numbers of young-of-the-year taken in beach-seine catches indicated that the 1968 year-class was stronger than 1969. Estimated numbers of bass per 92.9 meters2 (1,000 feet2 ) seined varied from 0.82 to 3.39 in 1968 and from 0.23 to 2.65 in 1969. An index to year-class strength may be obtained from seine catches at any time of the summer after brood dispersal, but indices obtained in this study must be validated by determing the contribution of each year-class to the creel.

The interactions between parasites, hosts, and the ecosystems they live in are complex and diverse. This can make predicting how they will respond to pressures like nutrient enrichment difficult. However, this endeavor is important, due to the far-reaching effects it has on ecosystems functioning, industries like aquaculture, and even human health. Even with the significance of this topic, there are key parts of the picture that have received little research attention. For this reason, I chose to study the effects of nutrient enrichment on parasite-host interactions at two different scales, first investigating the interaction directly between parasites and their host, and then manipulating experimental ponds to look at trophic effects. Using the theory of ecological stoichiometry as a conceptual framework allowed for comparison across the two investigations. In both studies, I used largemouth bass and the macro parasites of their digestive tract as my study system, due to the importance of largemouth bass as sport fish, their high trophic status, and diverse parasite assemblages. My first study examined the effects of eutrophication on parasite-host interactions occurring within the host. It centered on four hypotheses: 1) the nutrient content of different host tissues (infection sites) varies within and across hosts, 2) the nutrient contents of parasite genera differ from that of their host tissue(s), 3) the nutrient contents of parasite genera differ from one another, and 4) nutrient availability within specific host tissues is related to the nutrient content and abundance of parasite genera within tissues. I quantified the nutrient content (carbon (C), nitrogen (N), and phosphorous (P) and their ratios) of parasitic infracommunities in the tissues of the liver, stomach, pyloric caeca, intestines, and visceral mesentery of 30 largemouth bass (Micropterus salmoides). I found stoichiometric variation across host tissues and that fish collection site explained variation in pyloric caeca N:P ratios. Parasitic genera differed in their nutrient content with actively feeding parasite forms having higher %N and lower C:N ratios than encysted/non-reproductive forms. In addition, the %C of both actively feeding parasites varied across organs, and, for one genus, this variation reflected differences in host tissue %C. Finally, I found that the total number of actively feeding parasites in the pyloric caeca increased with that tissue’s N:P ratio. My results suggest that parasites encounter significant variation in nutrient availability within and across hosts, and that this variation can influence the nutrient content and abundance of some actively feeding parasites within specific tissues. To determine if the effects from my first study were a result of nutrient changes to host tissues or if they were an artifact of changes occurring at other trophic levels caused by nutrient addition, I conducted an experimental manipulation of a short trophic system. I applied two treatments, a fertilized treatment and a control, to 14 ponds stocked with largemouth bass. I hypothesized that adding a low N:P fertilizer to the ponds would result in fewer parasites in the pyloric caeca of the bass in accordance with findings from my previous work. Alternatively, I hypothesized that indirect changes to intermediate hosts would be responsible for changes in parasite abundance. To measure the effects of nutrient additions on multiple trophic levels, samples of fine particulate organic matter (FPOM), benthic invertebrates, and vertebrate prey were taken from each pond. Stocked bass were retrieved and dissected to obtain samples for nutrient analysis from their pyloric caeca, and to quantify parasite abundances. My treatment was able to affect the %P, C:N, C:P, and N:P of the FPOM in the ponds. Benthic invertebrate biomass was negatively correlated with FPOM %P. I did not find a direct effect of benthic invertebrates on vertebrate prey species, but fertilized ponds had a smaller decrease in the number of vertebrate prey over the course of the experiment. Counterintuitively, the %N of the pyloric caeca of fish in the fertilized ponds decreased, and the %C and C:N increased in relation to the number of vertebrate prey, but %P did not change. The treatment status of the pond and the nutrients of the pyloric caeca did not affect the number of parasites that were found, but parasite numbers were positively associated with prey fish. This result would suggest the number of intermediate hosts, in this case, prey fish, is the determining factor for parasitic loads in the bass I collected. The indirect effects of trophic interaction and the direct effects of changes to host and parasite dynamics both play important roles in predicting the outcome of eutrophication on disease. The conflicting results of these two studies highlight the need for in-depth knowledge of the systems being affected by nutrient additions.

In most Puerto Rico reservoirs, Largemouth Bass Micropterus salmoides are typically fast-growing with distributions composed of distinct year-classes. Cerrillos Reservoir, however, displays the classic characteristics of a crowded bass population common in temperate lakes and ponds with fish stockpiling into a single modal distribution of slow-growing fish. This developed shortly after stocking in 1997, with the population quickly expanding to carrying capacity. Consequently, relative weight declined from above 100 to about 80 and the population was mostly composed of fish <=350 mm. A protected slot limit (356-508 mm) was implemented; however, limited effort and angler attitudes towards harvest of small bass prevented the success of this regulation, which was subsequently removed. In this dissertation, I examined the efficacy of using targeted management harvests for improving growth, size structure, and condition of Largemouth Bass in Cerrillos Reservoir. I used bioenergetics modeling to simulate the effects of targeted harvests. I predicted annual consumption of stock and quality-sized Largemouth Bass and used these estimates to model the effects of population reduction on consumption and growth of remaining bass. To validate the model, experimental removals of Largemouth Bass from the crowded size classes (200-380 mm) were conducted in 2012 and 2013. In these two years, I removed 20% and 22% of the total biomass, respectively. Following the experimental removals, mean condition of Largemouth Bass increased from 83 to 90, and increases were observed in all Largemouth Bass size categories. The reduction in predator abundance resulted in increased prey availability and smaller size structure of sunfish (Lepomis spp.) and tilapia (Coptodon and Oreochromis spp.) populations. I concluded that reducing Largemouth Bass abundance in Cerrillos Reservoir can move population dynamics toward desired management outcomes, but these actions must continue indefinitely to achieve success and sustainability. Annual management harvests are feasible but impractical, so I recommend increasing angler harvest and implementing management efforts designed to limit recruitment (e.g., shoreline rotenone application) to achieve management goals.