Ostrea lurida Carpenter 1864 is the only native oyster on the western North American coast, but it is functionally extinct in most of its historic range. Knowledge of environmental tolerances during larval development of O. lurida is minimal, which limits recovery strategies for this listed “species of special concern” (Species At Risk Act). The effects of rearing temperature (13, 17, 21°C), salinity (11, 15, 21, 24, 30, 31 psu) and food concentration (5x103, 1x104 and 5x104 algal cells/ml) on larval growth and development were investigated. Larvae were obtained from laboratory conditioned adults from Ladysmith Harbour, and the Gorge Waterway on Vancouver Island BC. At low temperature (13°C), salinity (15 psu) and food concentration (5x103 algal cells/ml) larvae did not grow or develop. Higher temperature, salinity and food concentration increased growth and developmental rates. Larvae reared at higher food densities and salinities, but not higher temperature, were larger when eyespots differentiated. / Graduate

The Olympia oyster, Ostrea lurida. was overharvested in the early 20th century and is now the focus of restoration efforts in estuaries along the west coast of North America. These efforts would be aided by a better understanding of larval abundance patterns, settlement behavior, and post-settlement performance of oysters in estuaries throughout its range. In Coos Bay, Oregon, all three of these components of the oyster life cycle were investigated at multiple sites. Like adult oysters, larvae were restricted to the upper portion of the bay, although larvae were supplied to sites in the upper bay where settlement was low. Settlement and post-settlement growth was highest at sites of high adult density. These results indicate that in O. lurida, as in many other marine invertebrates, the adult population is subject to bottlenecks at the larval and juvenile stage that can vary spatially. This thesis contains previously unpublished co-authored material. / 2014-12-16

xiii, 86 p. : ill. (some col.) / In the Pacific Northwest, populations of the Olympia oyster, Ostrea lurida, were once decimated by overharvesting and natural disasters. Their full recovery may now be limited by availability of hard substrata for larval settlement. I studied the timing of settlement and larval preferences for commonly available substrata, including conspecifics and the shells of Pacific oysters, Crassostrea gigas, which are often provided in restoration efforts. Settlement occurred from August-December with a peak in October. I found no significant settlement differences between live and dead oysters or between shells of Olympia or Pacific oysters. There was significantly higher settlement on bottoms of horizontal substrata than on tops. In the laboratory, larvae showed no clear preferences among various hard substrata. This lack of settlement preference has positive implications for restoration projects, since Pacific oyster shell is much easier to obtain and seems to be no less beneficial than the shells of conspecifics. / Committee in charge: Dr. Craig M. Young, Chairperson; Dr. Richard B. Emlet, Member; Dr. Steven S. Rumrill, Member

From January 2012 to December 2012 I collected adult oysters from two intertidal populations on a monthly basis in the Coos Bay estuary, Oregon for histological analysis of their gonads. Gametogenesis and spawning occur seasonally from May through September, when water temperatures exceed 14.5&deg C, with brooding oysters found from July through September. Oocyte diameters increased significantly from May to June, and from June to July within oyster populations at Haynes Inlet and Coalbank Slough, respectively. Male gametogenesis initiated in May at Haynes Inlet and in June at Coalbank Slough. Dry meat condition values increased significantly during periods of reproduction and decreased following the reproductive season's end. Condition index values for Coalbank Slough were consistently lower than those at Haynes Inlet, suggesting poor nutrition or physiological stress. Salinities below recorded physiological thresholds are believed to be the primary environmental factor influencing the discrepancy in reproductive activity at Coalbank Slough.

The United States Pacific Northwest is well known for its shellfish farming. Historically, commercial harvests were dominated by the native Olympia oyster, Ostrea lurida, but over-exploitation, habitat degradation, and competition and predation by non-native species has drastically depleted their densities and extirpated many local populations. As a result, shellfish aquaculture production has shifted to the introduced Pacific oyster, Crassostrea gigas. An underlying objective of this dissertation is the use of molecular genetics to improve our ability to accurately identifying optimal oyster broodstock for either restoration of Olympia oysters or farming of Pacific oysters. The ecological benefits provided by oysters as well as the Olympia oyster's historical significance, has motivated numerous restoration/supplementation efforts but these efforts are proceeding without a clear understanding of the genetic structure among extant populations, which could be substantial as a consequence of limited dispersal, local adaptation and/or anthropogenic impacts. To facilitate this understanding, we isolated and characterized 19 polymorphic microsatellites and used 8 of these to study the genetic structure of 2,712 individuals collected from 25 remnant Olympia oyster populations between the northern tip of Vancouver Island BC and Elkhorn Slough CA. Gene flow among geographically separated extant Olympia oyster populations is surprisingly limited for a marine invertebrate species whose free-swimming larvae are capable of planktonic dispersal as long as favorable water conditions exist. We found a significant correlation between geographic and genetic distances supporting the premise that coastal populations are isolated by distance. Genetic structure among remnant populations was not limited to broad geographic regions but was also present at sub-regional scales in both Puget Sound WA and San Francisco Bay CA. Until it can be determined whether genetically differentiated O. lurida populations are locally adapted, restoration projects and resource managers should be cautious of random mixing or transplantation of stocks where gene flow is restricted. As we transition from our Olympia oyster population analysis to our Pacific oyster quantitative analysis, we recognize that traditional quantitative trait locus (QTL) mapping strategies use crosses among inbred lines to create segregating populations. Unfortunately, even low levels of inbreeding in the Pacific oyster (Crassostrea gigas) can substantially depress economically important quantitative traits such as yield and survival, potentially complicating subsequent QTL analyses. To circumvent this problem, we constructed an integrated linkage map for Pacific oysters, consisting of 65 microsatellite (18 of which were previously unmapped) and 212 AFLP markers using a full-sib cross between phenotypically differentiated outbred families. We identified 10 linkage groups (LG1-LG10) spanning 710.48 cM, with an average genomic coverage of 91.39% and an average distance between markers of 2.62 cM. Average marker saturation was 27.7 per linkage group, ranging between 19 (LG9) and 36 markers (LG3). Using this map we identified 12 quantitative trait loci (QTLs) and 5 potential QTLs in the F1 outcross population of 236 full-sib Pacific oysters for four growth-related morphometric measures, including individual wet live weight, shell length, shell width and shell depth measured at four post-fertilization time points: plant-out (average age of 140 days), first year interim (average age of 358 days), second year interim (average age of 644 days) and harvest (average age of 950 days). Mapped QTLs and potential QTLs accounted for an average of 11.2% of the total phenotypic variation and ranged between 2.1 and 33.1%. Although QTL or potential QTL were mapped to all Pacific oyster linkage groups with the exception of LG2, LG8 and LG9, three groups (LG4, LG10 and LG5) were associated with three or more QTL or potential QTL. We conclude that alleles accounting for a significant proportion of the total phenotypic variation for morphometric measures that influence harvest yield remain segregating within the broodstock of West Coast Pacific oyster selective breeding programs. / Graduation date: 2012