Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 89-105). Also available via the Internet.

Once historically widespread throughout the Willamette and Umpqua River drainages, the Willamette Oregon chub is now restricted to scattered populations along 15 miles of the Middle Fork of the Willamette River whereas the Umpqua Oregon chub is still widely distributed. The decline in the Willamette drainage was more severe because changes in the physical and biological habitat were more severe when compared to the Umpqua drainage. The Willamette Oregon chub may be more sensitive to environmental degradations than the Umpqua Oregon chub. The difference in sensitivity to degradation is a result of ecological differences between Willamette and Umpqua Oregon chub. Willamette Oregon chub inhabited areas with primarily very little if any current, fed in the water column, and spawned in aquatic vegetation. Umpqua Oregon chub inhabited areas with primarily slow water velocities, fed on benthic prey, and spawned over gravel substrate. Because Willamette Oregon chub inhabit slackwater habitats they may be more sensitive to water velocity increases and exotic species, whereas Umpqua Oregon chub have a habitat refuge in relatively faster water velocity habitats. Willamette Oregon chub larval stages are described and illustrated. The following combination of characters distinguish Willamette Oregon chub larvae from other cyprinid larvae found in the Willamette drainage: 33-37 myomeres, preanal length of 52-61%, and absence of snout pigment. Willamette Oregon chub larvae generally congregated in nearshore areas, in the upper layers of the water column, in shallow water. They fed primarily in the water column, and ate primarily rotifers and cladocerans. / Graduation date: 1989

No description available.

No description available.

Electrophoretic variation in 12 proteins encoded by 16 loci was analyzed to compare the genetic relationships of 18 natural populations representing two species of stoneroller minnows, Campostoma anomalum and C. oligolepis. Ten of the loci were monomorphic and fixed for the same allele in all populations of both species. One locus, Mdh-2, was found to separate both species. Mean heterozygosity for both species was 0.072. Estimates of levels of inbreeding indicated this phenomenon is operating in C. anomalum to structure the populations genetically. Mean genic identity (I) between the two species was high, 0.887, indicating the taxa are closely related. Nevertheless, data accumulated point to the conclusion that the two species maintain electrophoretic variation in 12 proteins encoded by 16 loci was analyzed to compare the genetic relationships of 18 natural populations representing two species of stoneroller minnows, Campostoma anomalum and C. oligolepis. Ten of the loci were monomorphic and fixed for the same allele in all populations of both species. One locus, Mdh-2, was found to separate both species. Mean heterozygosity for both species was 0.072. Estimates of levels of inbreeding indicated this phenomenon is operating in C. anomalum to structure the populations genetically. Mean genic identity (I) between the two species was high, 0.887, indicating the taxa are closely related. Nevertheless, data accumulated point to the conclusion that the two species maintain their genetic integrity throughout their ranges. their genetic integrity throughout their ranges.

No description available.

Oviposition-site decisions can have disproportionate effects on offspring survival and success, and while the effects of these decisions are frequently investigated, the processes underpinning these decisions and the cues used are often less well understood. The aim of this thesis was to understand the mechanisms associated with making oviposition decisions, and their consequences, using the European bitterling (Rhodeus amarus), a small freshwater fish that lays its eggs in the gills of freshwater mussels. Using an artificial mussel, females were shown to respond to dissolved oxygen, relating to offspring survival, while males attend to water flow velocity, with implications for sperm competition. Oviposition decisions by either sex were unaffected by olfactory cues associated with sperm release, though males and females were responsive to visual cues associated with ejaculation. An analysis of the placement of eggs within the mussel gills by females failed to show evidence of “handedness”, though there was a tendency to place eggs in a mussel's inner gills, which may be adaptive in avoiding competition with the mussel's embryos. Male response to oviposition sites showed inter-population variation, with males from a population with high levels of mean crowding showing an elevated frequency of mussel inspection and probability of ejaculation. Males also increased the frequency of mussel inspection in response to the presence of a gravid female, suggesting a role for sperm competition and fertility assurance. Social network analysis was used to investigate how male interactions affect oviposition decisions. This approach showed that male mating tactics could be understood by quantifying how males distributed their sperm among oviposition sites. Findings are discussed in the context of our understanding of the bitterling mating system and research on oviposition-site decisions.

In this study 883 specimens of the woundfin minnow (Plagopterus argentissimus Cope) from the Virgin River in Utah, were weighed and measured. Ratios of body measurements to standard length, and gonad weight to total weight were calculated. From the gonad weight:total weight ratios it was determined that woundfins spawn during a period from April through June, and that the first significant gonad development is during the third year of life. Several body proportions such as, snout length, gape, upper jaw length and peduncle depth grew nearly isometrically. Growth of other body proportions was more or less allometric. Head length, body depth and mouth length showed gradual changes. Pectoral fin length, eye length and total length showed rather marked allometry. The ratio of dorsal fin height to dorsal fin length also showed rather marked allometry.

Traditional herbicide formulations such as Roundup® contain the active ingredient glyphosate paired with the non-ionic surfactant polyethoxylated tallow amine (POEA). The impacts of POEA in aquatic environments are uncertain. In this study the environmental fate and effects of POEA was evaluated. A mesocosm field study confirmed that POEA dissipated rapidly from the water, but was persisted in the sediment; biological effects were negligible. In the laboratory, histological analysis of gills did not indicate negative effects on gill function in Pimephales promelas exposed to POEA. Proliferation of mucous cells in gills was significantly greater following 7 days of exposure. Liver histology appeared normal following exposures. Mean thiobarbituric reactive substances (TBARS) doubled in minnow livers exposed to 10 µg.L-1 POEA for 7 days; however was not statistically significant. The present study indicates that POEA may persist in sediment and may influence benthic communities over the long term. / May 2016

Fathead minnows (Pimephales promelas) were exposed to mercury (1.69, 6.79, and 13. 57 µg/l HgCl2; 10 d exposure) and afterwards tested using various metrics of foraging ability while feeding in a vegetated habitat. Among the foraging metrics were foraging efficiency, capture speed, and the ability to learn and retain information regarding habitat characteristics. Comparisons with control fish and fish from the two highest exposure groups revealed consistent performance deficits in foraging efficiency and capture speed. However, no treatment effects on learning were detected. In determining the underlying proximate cause of the foraging deficits, it is believed that the greater pause time exhibited by treatment fish while foraging was the main cause of treatment differences. In the future, behavioral studies will continue to allow toxicity testing of environmentally relevant variables such as those used by behavioral ecologists. Such tests, when combined with tests of field collected specimens, could prove powerful in linking laboratory toxicity to toxicity in wild populations. / Master of Science