Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains vii, 54 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

The geographic range of the panmictic American eel (Anguilla rostrata) has contracted in recent years because of the pronounced decline in recruitment of glass eels and elvers to the Laurentian Basin. In consequence, the American eel was assessed in 2006 as a species of special concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). The evident sensitivity of American eel status to elver recruitment highlights the importance of understanding both the mechanisms contributing to the delivery of glass eels from the Sargasso Sea to continental waters and mortality following their recruitment to coastal and inland waterways. The potential for variability in environmental quality at localized geographic scales to affect American eel productivity and hence the status of the species and the fisheries it supports is not fully understood. The Atlantic coast of Nova Scotia is an ideal location to examine the relationship between water quality and American eel productivity. Within Nova Scotia there is wide natural variation in freshwater pH, which has been further increased in recent years by the effects of acid precipitation. This variation occurs over a small geographic range of several hundred kilometres that overlaps an area of high elver influx. As low environmental pH is known to adversely affect aquatic ecosystems, it has been identified as a possible threat to elver survival. In this study, the effect of low pH on elver survival was examined in both laboratory and field based trials using wild glass eel/elvers that were captured upon entry to fresh water. Trials examined the mortality rate of elvers at pH levels within the range of 4.0 - 7.0 over a 10 day period. The relationship between elver development and mortality at low pH was also examined through pigmentation analysis. Laboratory and field based studies resulted in zero mortality among elvers in natural and artificial acidic environments with pH levels as low as 4.0., thus indicating that the American eel is fully acid tolerant upon initial migration into fresh water. Sub-lethal effects of acidification were explored by examining the hematological parameters of river resident yellow-phase American eels exposed to varying levels of acidity in the laboratory. The level of acidification proved not to be a factor in determining both hematocrit and blood plasma osmolarity levels, as there were no significant differences in these variables between eels exposed to acidic conditions and those exposed to control neutral pH conditions. These results suggest that through the use of a highly effective mechanism for regulating blood ion concentration, the eel is able to tolerate low pH conditions.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Nancy M. Targett and Timothy E. Targett, College of Marine and Earth Studies; Pamela J. Green, Dept. of Plant & Soil Science. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains vii, 32 p. : ill., map (part col.) Includes abstract. Includes bibliographical references.

Species’ distributions are influenced by abiotic and biotic factors but direct comparison of their relative importance is difficult, particularly when working with complex, multi-species datasets. Here, we present a flexible method to compare abiotic and biotic influences at common scales. First, data representing abiotic and biotic factors are collected using a combination of geographic information system, remotely sensed, and species’ functional trait data. Next, the relative influences of each predictor variable on the occurrence of a focal species are compared. Specifically, ‘sample’ data from sites of known occurrence are compared with ‘background’ data (i.e. pseudo-absence data collected at sites where occurrence is unknown, combined with sample data). Predictor variables that may have the strongest influence on the focal species are identified as those where sample data are clearly distinct from the corresponding background distribution. To demonstrate the method, effects of hydrology, physical habitat, and co-occurring fish functional traits are assessed relative to the contemporary (1950 – 1990) distribution of the American Eel (Anguilla rostrata) in six Mid-Atlantic (USA) rivers. We find that Eel distribution has likely been influenced by the functional characteristics of co-occurring fishes and by local dam density, but not by other physical habitat or hydrologic factors.

No description available.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vii, 67 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves 90-100).

No description available.

Recruitment of American eels (Anguilla rostrata) to Lake Ontario has declined rapidly over the past few decades. The commercial yellow eel fishery in Lake Ontario was closed in 2004 due to a lack of eel abundance. Researchers have been attempting to ascertain the reasons for the decline, although thus far, without definitive answers. In this thesis, the question of chemical contamination is addressed as it relates to female eel spawner quality. Spatial concentration trends of halogenated persistent organic pollutants (POPs) are described in eels collected from across eastern Canada, as well as temporal concentration trends in eels collected from a historically important area of northeastern Lake Ontario, Canada. Chlorinated POPs in eels, namely, organochlorinated pesticides, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans are all significantly less than historic values which peaked in the 1960-70s. Measured concentrations of chlorinated POPs in eels from Lake Ontario have decreased by up to 3-fold over the past three decades, and exceeded toxicity thresholds historically for surrogate species (European eel and lake trout). Thus, chlorinated POPs may have had an effect on spawner quality. Concentrations of legacy POPs in eels were dependent on their origin, with eels from highly urbanized and industrialized areas having significantly higher concentrations than eels captured in less developed regions. Similar trends were observed for polybrominated diphenyl ethers and chlorinated norbornene flame retardants. A number of emerging brominated compounds were also measured in these eels by non-target analysis including bromophenols, bromobenzenes, and bromoanisoles. This thesis demonstrates that eels are an ideal species to investigate local sources of pollution, and provide chemical data that may be used in the future, when more toxicity information is available for eels, to assess the health risks posed by accumulated chemical contaminants. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-05-23 09:27:59.593