The responses of larval fish to toxicants in subchronic toxicity tests may be modified by events and stressors not associated with the toxicants themselves. In the following work, three potential modifying factors related to larval fish growth, survival, and response to toxicant stress were investigated. Using four-day acute cadmium toxicity tests and seven-day subchronic toxicity tests, differences in the responses of larvae based on the age of the larvae, their exposure to methylene blue, and changes in environmental pH were determined. The age of larvae chosen for toxicity tests, 1 to 24 h old, 24 to 48 h, or 48 to 72 h, did not significantly affect the cadmium (Cd) LC_50S in acute tests or the larval growth or survival in subchronic tests. Prior methylene blue (MB) exposure in larval fish was. not found to affect the Cd LC₅₀ compared to unexposed larvae. However, in subchronic tests with industrial effluents, prior MB exposure resulted in lowered survival or lowered growth, but did not increase sensitivity to the effluent. Lowered growth and survival was observed in blue- dyed individuals from larval populations exposed to MB during the interval from hatch to test commencement. At 20°C, the acute toxicity of MB, as indicated by the LC_10S, was apparent at concentrations greater than 44 mg MB/L in 24 h. At the suggested fathead minnow culture temperature, 25°C, concentrations greater than 5.0 ppm were acutely toxic in 96 h. Chronic toxicity, determined at 25°C, was found at levels greater than 2.12 mg MB/L. Light intensity negatively affected MB chronic toxicity. Chronic values estimated by larval fish growth response were significantly lower in the test done under normal lab light compared to that done under very subdued light. Larval fathead minnows were sensitive to low pH stress based on the acid used to lower test solution pH. Hydrochloric acid was found least toxic to larvae at low PH; phosphoric acid was found most toxic. Larvae tolerated instantaneous changes in pH 2.0 units lower and 1.5 units higher than their culture water without any significant decrease in growth and survival as measured in 7 d. These results indicate that the pH tolerance range for larval fathead minnows, where no effects are seen on growth or survival, is greater than pH 6.0 and less than pH 9.5. / Master of Science

Campostoma anomalum roanokense, a new subspecies of C. anomalum in the James and Roanoke Rivers of Virginia, West Virginia, and North Carolina is compared to C. a. kanawhanum, the most closely related form, and to other similar forms. Three races of C. a. roanokense: a. South Fork Roanoke River Race, b. North Fork Roanoke River Race, and c. James River Race, are described and their relationships discussed. A Roanoke River endemic (Notropis cerasinus) taken from the New River drainage and the interrelationships of the three races of C. a. roanokense may indicate a more recent contact between the New and South Fork of the Roanoke River watersheds than has taken place between the New and the James River watersheds. / Master of Science

The presence of many human pharmaceuticals in the aquatic environment is now a worldwide concern and yet little is known of the chronic effects that these bioactive substances may be having on aquatic organisms. This study used mammalian pharmacodynamics to predict the mode of action of the 13-blocker, propranolol, on fish, in order to identify chronic effects in fathead minnows. β-blockers target β1- and β2-adrenergic receptors in humans and hence these receptors were characterised in the fathead minnow. It was found that fish possess β1- and β2-ARs that are structurally very similar to their mammalian counterparts. Further, the distributions of these two β-ARs in various organs of the fathead minnow were similar to those in mammals. Pair-breeding assays were conducted, in which fathead minnows were exposed to various concentrations of propranolol. To discover whether β-ARs had been up or down regulated by propranolol, molecular analysis was conducted on different tissues of the exposed fish using real-time polymerase-chain reactions (RT-PCR). Exposure of fathead minnows to propranolol caused acute toxicity at 10 mg/L. Propranolol caused a statistically significant decrease in reproduction at 1.0 mg/L, dose-related decreases in male weight, condition index and fatpad weight, and a dose-related increase in female GSI. Molecular analysis of βl- and β2-AR expression levels revealed a dose-related decrease in β2-AR expression in fathead liver and heart. LOEC and NOEC values were 0.1 mg/L and 0.01 mg/L, respectively. Propranolol plasma concentrations in fish exposed to water concentrations of 0.1 and 1.0 mg/L were greater than the human therapeutic concentration and hence these data very strongly support the fish plasma model proposed by Huggett et al. (2001).

Parasites exert substantial costs on their hosts. Thus, natural selection should favour behavioural defenses that reduce hosts’ exposure to parasites. This prediction has rarely been tested for aquatic hosts exposed to parasites. I designed experiments to test if fathead minnows could detect cercariae of the trematode, Ornithodiplostomum sp. and engage in antiparasite behaviours to avoid them. Minnows exposed to cercariae formed 20.1% tighter shoals compared to water controls. Further, minnows greatly reduced their overall activity, but only when they were exposed for a second time. The latter result is important because it provides the first indication that hosts can learn to avoid parasites. Lastly, I tested if epidermal club cells play a defensive role against cercariae. Club cells did not, but other components of the epidermis, probably mucus cells, decreased cercarial infectivity by 61-68%. My results show that fish can detect, learn, and ultimately avoid aquatic larval stages of parasites. / 105 leaves : ill. ; 29 cm.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Aug. 19, 2009). Bibliography: leaves 39-45.

D.Phil.

Used tires have the potential for becoming popular in pollution control media used in stormwater applications including pervious pavement sub bases, green roof growth media, and upflow filters. Using tire crumb to decrease nutrients can minimize impacts on ecology while reducing the human footprint left by used tires. However, if tire crumb is not examined for toxicity, the ecological balance could unknowingly be disrupted. This research tested the acute toxicity of tire crumb in aquatic systems by finding the Lethal Concentration for 50% kill (LC50). Using an extreme tire crumb load, P. promelas (fathead minnow) were exposed to leachates created with tire crumb and several different types of water including distilled water, tap water, and detention pond water. For distilled and tap water, the addition of tire crumb increased the survival of P. promelas. For detention pond water, the addition of tire crumb decreased the survival of P. promelas, though only enough to find an LC50 for detention pond water influenced immediately by stormwater runoff. An LC50 was found when 100 percent tire crumb filtrate is prepared with 25 grams of tire crumb per liter of detention pond water collected directly after a storm. The LC50 found is resultant of a tire crumb load significantly higher than what can be expected in the environment. Based on this research, tire crumb is considered non-threatening to aquatic fish and safe to use with detention pond water.

The hydrography of Utah may be thought of as being roughly divided into two large general drainage areas--, the Colorado River draining the eastern halt and southern portion ot the state and the Bonneville Drainage encompassing the remaining part of it. Earlier workers have listed eight genera and fourteen species of minnows occuring in Utah. Of these this report includes seven genera and ten species found within the borders of our state.

No description available.

This thesis explores the biology, ecology, and life-history styles of two closely-related redfin minnows, Pseudobarbus afer and P. asper (pisces; Cyprinidae), which both occur in the Gamtoos River system of South Africa. Five of the seven species of flexible-rayed redfin minnows are in the South African Red Data Book - Fishes. This investigation was designed to provide the data which would enable conservation authorities to manage the remaining populations of the Pseudobarbus species. A thorough understanding of the Gamtoos River system was necessary to properly interpret the findings of this study. The palaeo river systems and the changing climates since the break-up of Gondwanaland are discussed so that the present day environments could be considered as well as the past environmental changes. P. afer and P. asper occur in the Gamtoos River system with no physical barrier separating the two species. P. afer only occurs in the clear mountain streams of the Cape Fold Mountain Belt whereas P. asper occurs in the highly saline and turbid Karoo section of the system. P. afer were found to be the more precocial form of the sister species. They had bigger eggs, lower relative fecundity, shorter breeding season, lower gonadosomatic indices, larger first feeding larval fish, matured later and had a longer life-span than did P. asper, which had more altricial life-history attributes. They differ in their tradeoffs with P. asper devoting more resources earlier to reproduction and having a shorter lifespan. The improvement in the one aspect of fitness (early maturity) leads to the deterioration in another, namely lifespan. Both species undertake breeding migrations to riffle areas where they spawn in mid-channel immediately above a pool after an increase in water flow. P. afer and P. asper are non-guarders of their non-adhesive eggs and young, open substrate spawners on coarse substrates (rocks) and have photophobic free embryos. The breeding season is shorter for P. afer whereas P. asper can spawn as late as April and impoundment releases can induce them to spawn. A study of comparative neuroecology revealed that of the four groups of fish analyzed (males and females of both species) male P. afer had the largest brains, especially the optic lobes and cerebellum. P. asper females had the smallest brains. No neural compensation in the external gustatory centre, the facial lobe, was found for P. asper inhabiting the turbid waters. P. afer also had significantly larger eyes and longer barbels. P. afer males were also found to have the highest density and largest nuptial tubercles as well as the most pronounced breeding colouration. It was concluded that P. asper is the more derived of the sister species pair with regard to life-history attributes. It is further suggested that investment per offspring is important in determining the life-history trajectories. Paedomorphosis has occurred and by this mechanism variability has been restored to the redfin minnows in the Groot River which enables them to survive in the highly variable, intermittent Karoo stream. The more precocial P. afer do not require this variability in the more constant and predictable environment of the Wit River.