Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (levaes 151-161). Also available via the Internet.

Thesis (M.S.) in Wildlife Ecology--University of Maine, 2004. / Includes vita. Includes bibliographical references (leaves 65-76).

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on Apr. 20, 2009). Includes bibliographical references.

No description available.

No description available.

The population, reproductive biology and physical habitat requirements of endangered freshwater pearl mussel (<I>Margaritifera margaritifera</I> (L.)) populations in Scotland were investigated. Surveys of viable populations revealed overall densities, based on 1m² quadrat counts, of 0.27-7.98 mussels.m^-2. Total estimates for rivers, based on extrapolations of 50m transect counts, ranged from 2,000 to 0.9-3.7 million mussels. The expected predominance of young mussels was not achieved in any population. In order to test a hypothesis that juveniles were under-represented in samples, six populations first studied in 1984/85 were re-investigated in 1996/97. The relative numbers of 11-20y old individuals found in 1996/7 were consistently larger than those of 1-10y olds found a decade earlier. This provides strong evidence of sampling bias. <I>M.margaritifera</I> grow in an approximately asymptotic fashion and the von Bertalanffy equation is an appropriate descriptor. Growth may be influenced by temperature. In general, large mussels grow in large, cold rivers and vice versa; although there are exceptions, which suggest that additional factors may be involved. The timing of annual reproduction seems to be related to temperature. Mussels in the warmest rivers tend to spawn earliest. The prevalence and magnitude of natural parasitic mussel larval (glochidial) infections in wild salmon (<I>Salmo salar</I> L.) and trout (<I>S.trutta</I> L.) stocks were comparable to those reported elsewhere. Older fish seem to be less susceptible to glochidiosis than 0+ fish. Some trout stocks appear to be under-utilised by <I>M.margaritifera</I>, possibly due to differences in behaviour and/or place of origin. River bed substratum characteristics appear to be the best physical parameters for describing <I>M.margaritifera</I> habitat. Boulder-stabilised refugia, which contain enough sand/gravel for borrowing, are ideal habitats for juveniles.

The age structures of several populations have been recorded at ten year intervals for the past 20 years.  The changes in the age structures of these populations indicate that small mussels are often under recorded due to sampling bias.  Some populations show unchanged age structures indicating that levels of recruitment have been maintained, whereas others show aging population structures, with very few young mussels being recruited to the population. The habitat requirements were modelled using a number of techniques.  All the models indicate that, in Scotland, physical habitat parameters are the most important for determining habitat suitability at the between river scale.  Models of habitat requirements for juvenile mussels indicate that the sediment variables, particularly the amount of silt present, are most important, while models for adult mussels also include macrohabitat variables.  However, the resolution of these models is compromised by the effects of pearl fishing, which has reduced the densities or removed mussels from areas of otherwise suitable habitat, thus resulting in a lack of differentiation between suitable and non suitable sites. The genetic diversity and differentiation within and between populations was examined and showed that Scotland contains some populations with a high genetic diversity when compared to other populations studied in Europe.  Some populations, however, were shown to be lacking diversity, and had a small effective population size, making them vulnerable to the effects of inbreeding depression and genetic drift.  Differentiation between rivers showed that rivers geographically close were not always the most genetically similar.  This may have implications during translocation or restocking programmes. Recommendations are made for future conservation efforts.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 85-90). Also available via the Internet.

Thesis (Ph. D.)--Johns Hopkins University, 1916. / Cover title. Vita. "Reprinted from the Journal of experimental zoölogy, vol. 21, no. 3, October, 1916." "Literature cited": p. 424.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 88-99). Also available via the Internet.