Thesis (Ph. D.)--University of Hong Kong, 1978.

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: [44]-53)

Thesis (M.Sc. Biological Sciences)--University of Waikato, 2008. / Title from PDF cover (viewed March 12, 2009) Includes bibliographical references (p. 63-73)

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.

Many freshwater mussels are imperiled, due to a number of interrelated factors such as habitat alteration, degradation of water quality, and impoundments. The Golden Orb mussel (Quadrula aurea, I. Lea, 1859) is endemic to the state of Texas and is currently a candidate for the endangered species list, as the number of known populations has been declining in recent years. Little is currently known about Q. aurea aside from basic distribution data. This study is focused on evaluating a combination of macro-habitat and micro-habitat variables to determine their influence on the distribution and density of this species. Macro-habitat variables, including dominant land cover, surface geology, and soil erodibility factor, did not have a significant relationship with mussel distributions. The best model of micro-habitat variables that impacts the Q. aurea distributions is comprised of relative substrate stability (RSS) at moderate flows and current velocity at low flows. For all mussel species in this study, current velocity at low flows is the primary variable that influences distribution. Q. aurea are associated with habitats where larger sediment particles (large gravel and cobble) help to stabilize the substrate in areas with higher current velocities. An understanding of the preferred habitats for Q. aurea can be used to help focus conservation efforts and practices.

Metallothioneins are ubiquitous sulphur-rich heavy metal binding proteins whose biosynthesis is induced in response to a variety of agents, including heavy metals. A number of isoforms of metallothionein are known to be induced by heavy metals in the common mussel Mytilus edulis, and recently interest has centred on the nature of these proteins and their possible utility as pollution indicator agents. Cadmium-induced metallotheioneins were isolated from mussels by procedures which included gel permeation and anion-exchange chromatography. They were shown to comprise two molecular mass classes of 10 and 20KDa. The 10kDa class was resolved by anion-exchange into four components designated 10-I, 10-II, 1--III and 10-IV. The 20kDa class was similarly resolved into three components designated 20-I, 20-II and 20-III. The amino acid sequences of each of the components in both of the classes were determined. This involved digestion with a variety of proteinases and separation of the resulting peptides. The abundance of crysteines in these mussel metallotheioneins necessitated their derivatisation with methyl-p-nitrobenzenesulphonate to generate the S-methyl derivative of cysteine which has been found to be suitable for peptide mapping by HPLC and sequence analysis by automated methods. The components of the 20kDa class were shown to possess linked peptides consisting of 71 amino acids, which were distinct from the 72 amino acid peptides of the 10kDa class. It is suggested that the two monomers in the 20kDa proteins are linked via S-Cd-S bonding, i.e. a bridging cadmium ion. The various components within both classes exhibited homology, particularly with regard to the location of the cysteine residues, to metallothioneins from other species, including mammals. On the basis of this homology these proteins were classified as class I metallothioneins.

Contemporary efforts to conserve and restore the marine environment are centred on regulating anthropogenic activities in defined ocean areas through marine protected areas (MPAs). This spatially explicit approach is contingent upon a good understanding of the biology and distribution of species. However, our understanding of many rare and threatened benthic species, for which conservation MPAs are currently being designated, is poor. The fan mussel, Atrina fragilis (Pennant 1777), a rare and vulnerable sessile benthic species that shows a reduced distribution compared to historical accounts, was used as a case species. Identifying the larvae of sessile benthic species is an essential first step in informing their conservation. Here, the first description of larva belonging to A. fragilis is presented along with key life-history traits. A point process modelling framework appropriate for the analysis of presence-only data, along with techniques to address both observer bias and uncertainties with historical occurrence records, were employed to successfully predict the distribution of A. fragilis, revealing potentially important drivers in its current distribution. The transport of A. fragilis larva, taking into account key aspects of life-history, habitat suitability and fine scale hydrodynamics, was modelled to investigate potential levels of connectivity within the Scottish sea area, allowing the potential supply of larvae to areas of suitable habitat and the Scottish MPA network to be evaluated. To date there has been no consideration of the likely effectiveness of measures in most inshore MPAs. Here we assessed the siting of MPAs in relation to fishing intensity and seabed ruggedness on the west coast of Scotland. The results suggest little reduction in fishing pressure is effected by current restrictions on activity in the subset of MPAs investigated, with protection principally being applied to rugged areas that may already act as natural refugia for vulnerable benthic species such as A. fragilis.

The specific activity of ⁶⁵Zn (nanocuries ⁶⁵Zn/g total Zn) was determined in various organs of the common coastal mussel, Mytilus californianus Conrad, collected from six locations along the Pacific Coast. These organs included the gills, mantle, foot, reproductive organs, adductor muscle, and viscera. After ashing and dissolving with nitric acid (8 M), each tissue was analyzed for ⁶⁵Zn by gamma-ray spectrometry. The determination of total zinc concentrations of the various organs was accomplished by atomic absorption spectrophotometry as well as by neutron activation analysis. Variable amounts of both stable zinc and radioactive ⁶⁵Zn were observed within the specific tissues from a given location. The ⁶⁵Zn specific activities of the tissues of organisms from a particular station however, tended to be uniform, at least within the uncertainty of the measurements. Both radiozinc and ⁶⁵Zn specific activity decreased with distance from the Columbia River mouth, whereas the stable zinc tended to remain uniform for a specific tissue. Tissues high in radiozinc were also high in stable zinc and conversely. An estimate of the input specific activity from the mussel' environment (food and/or water) was calculated from a simple model resulting in a value similar to zooplankton values sampled from within the Columbia River plume. Comparison of the concentrations of zinc determined by neutron activation with those determined by atomic absorption spectrophotometry indicated a linear relationship between the two methods. Results of atomic absorption measurements were approximately 27% larger than the results of neutron activation analysis, indicating the presence of a systematic error. The higher values attained by atomic absorption are attributed to evaporation during storage of the ash solution which would lead to an increase in zinc concentration. In considering the two methods of analysis, economy of both time and expenses favors the atomic absorption method over that of neutron activation. / Graduation date: 1971