For certain shellfish species, a mechanical harvester has the potential to greatly reduce harvesting costs. Traditionally, hand rakes are used in shellfish harvesting in British Columbia. In order to determine if it is environmentally feasible to use a mechanical harvester, an environmental assessment on mechanical harvesting and traditional harvesting needs to occur for comparison. In July 2008, a preliminary oceanographic assessment was conducted at three study sites in Baynes Sound. Each of the three study sites contained a mechanical and manual harvest plot and reference stations. Sampling stations were established at fixed positions within each plot and at four positions along a downstream transect (following the dominant current direction.) Surveys were conducted 24 hours pre-harvest, immediately post-harvest, and 24 hours post-harvest. Parameters included in situ sediment sulphides, eH (REDOX), sediment grain size (SGS), visual condition (digital imagery), sedimentation (silt flux) and sediment macro-fauna. Results show only localized environmental effects associated with each harvest approach; with no significant difference documented between the manual and mechanical harvesting methods on the study beaches. These results indicate the use of a mechanical shellfish harvester is as environmentally sound as the traditional method of hand harvesting, and poses no additional environmental risks. Introducing mechanization in shellfish harvesting will allow shellfish producers to reduce costs and increase profits, making the British Columbian shellfish industry more competitive with other suppliers. / Graduate

Thesis (Ph. D.)--University of Washington. / Bibliography: l. [144]-150.

Thesis (Ph.D.)--University of Western Australia, 2007.

Growth of Corbicula fluminea was monitored in the laboratory. Three experiments were conducted. Experiment I utilized three substrates and one food type. Experiment II utilized three substrates and two food types. Experiments I and II were conducted to determine if substrate type or food type effected growth. Experiment III used no substrates, one food type and was conducted to determine growth response to different types of water. Clams were maintained in three substrates: sand, gravel and clay. Clams were also maintained without substrate. Growth was monitored by measuring shell length (mm) and recording the weight (mg) of clams over a period of thirty days. At the end of the test period data were evaluated for normality and homogeneity.

No description available.

Meiofauna are an abundant, diverse and important component of the marine biota, however, much of their ecology has been neglected. Despite their high densities, meiofaunal abundance is often patchy. Meiofauna present in high numbers at one site will often be less abundant in seemingly similar adjacent sites. What factors govern this variability? How readily do these animals colonize new patches? How do various biological and environmental factors affect meiofaunal colonization rate and resulting assemblage structure? The response of meiofauna to changes in abiotic factors, including sediment grain size, depth, exposure and distance from the ocean floor, was quite variable. Often one factor would affect certain taxa and not others. Even slight increases in depth resulted in drastic declines of harpacticoid copepods while nematodes were unaffected. Meiofauna were also fewer in sediments with large interstitial spaces. Some meiofauna were most abundant in sediments placed closer to the ocean floor. Other taxa colonized distant substrata as rapidly as they did substrate located closer to the ocean floor. This suggested differences between taxa in their rates of active dispersal. The effects of macrofauna on meiofauna have been debated. In particular, how do clams affect the colonization and assemblage structure of meiofauna? Certain characteristics of clams were isolated and evaluated: feeding behaviour, bioturbation rate/depth and metabolic byproducts. Clams that caused the greatest meiofauna declines were shallow burrowing deposit-feeders. Constant disturbance to the upper sediment by these clams was likely responsible for meiofaunal impact. Conversely, suspensionfeeding clams that passed quickly to deeper sediment and remained stationary had little impact on meiofauna. Finally, a survey of local marine nematodes added nine genera new to Canada and 24 genera new to British Columbia. A review was also compiled that shows nematodes and other meiofauna have been neglected for much of Canada. Although these small and abundant animals are quick to colonize even distant habitats they are quite sensitive to cues from the surrounding biotic and abiotic environment. This sensitivity combined with their ease of collection make meiofauna a valuable asset to any number of ecological investigations. / Ecology

Typescript. Bibliography: leaves 46-47.

Thesis (M.E.S.)--The Evergreen State College, 2008. / Title from title screen (viewed 10/21/2009). Includes bibliographical references (leaves 62-72).

No description available.

Axinopsida serricata (Bivalvia) is abundant in coastal waters of British Columbia subjected to natural and anthropogenic disturbance. To investigate the monitoring potential of histological lesions, field populations were sampled in Holberg Inlet and Quatsino Sound, British Columbia, from benthic habitats affected by the submarine discharge of copper-mine tailings, and from a reference site in Mill Bay, Saanich Inlet. Based on a quantitative analysis of the digestive gland, ctenidia, kidney, gonad and stomach, the relationship between histological variation and site, size, season, sex and parasitism was explored. The relationship between occurrence of histological lesions in this species and further ecological consequences of mine-tailings discharge was also explored by comparing population characteristics of clams living in deposited tailings with clams from the reference site. Between-sample differences were observed in the structure of digestive tubule digestive cells, digestive ducts, ctenidial frontal cells, laterofrontal cells, and abfrontal mucocytes, kidney concretions, and stomach epithelial cells. The pattern of differences in tissue structure between samples reflected proximity of the collection site to the mine-tailings discharge and seasonally-dependent reproductive activity. Simultaneous examination of six of the tissue variables (using a principal components analysis) showed that clams collected from three stations in Lower Holberg Inlet which were in closer proximity to the tailings discharge pipe were distinguishable from clams collected from the reference site, upper Holberg Inlet, and Quatsino Sound. Tissue structural variability in A. serricata was not influenced by sex, or ectoparasitism by a flagellate. Tissue variables were not causally related to clam size (and thus of age and duration of exposure). In spite of the notorious natural plasticity of molluscan tissues, the variability can be partitioned to provide a very effective interpretation of exposure to stressors. Based on an increased abundance in degraded habitats, A. serricata, and the superfamily Lucinacea in general, have been described as r-selected or opportunistic species. An investigation of life-history traits showed that A. serricata has a maximum longevity of five years or longer, exhibits sporadic growth primarily in the summer months, and is an iteroparous, gonochoristic broadcast spawner with gamete release occurring primarily in November. The observed life span of the clam and presence of ova which are very large (maximum diameter is approximately 100 μm) and yolk-rich for a broadcast spawner are somewhat at odds with the contention that A. serricata is an r-selected species. Tissue variations which occurred in the digestive tubules and ctenidia with increased incidence and severity closer to the tailings discharge pipe are similar to histopathological effects in molluscs as described by others. However, there is no evidence that tissue lesions in A. serricata negatively affect fecundity, growth, or abundance. The sub-population sampled closest to the discharge pipe is in a state of decline, but this is due to the absence of recruitment since 1986, rather than increased mortality in the established population. The apparent decoupling of tissue-level and population-level effects may be due to a time lag in manifestation of decreased fitness at the population level, selection of stress-tolerant individuals in response to the stressor, a strategy of neglect of somatic maintenance and repair, or some other mechanism. It is possible that A. serricata and other small Thyasirids have an evolutionary history which provides pre-adaptation to environmental stressors. / Graduate