Brent Vadopalas

SUMMER SEED MORTALITY OF THE PACIFIC OYSTER, CRASSOSTREA GIGAS THUNBERG GROWN IN TOMALES BAY, CALIFORNIA, USA: THE INFLUENCE OF OYSTER STOCK, PLANTING TIME, PATHOGENS, AND ENVIRONMENTAL STRESSORS

Abstract Summer seed mortality (SSM) has occurred yearly in Tomales Bay, California since 1993. SSM has resulted in up to 90% cumulative losses, and has been associated with extreme temperature, phytoplankton blooms, and an oyster herpesvirus. In this study, three stocks of Pacific oysters were planted at three sites in California (Inner Tomales Bay, Outer Tomales Bay, and Bodega Harbor) in October of 2000 (Fall) and April of 2001 (Spring) and monitored for mortality, growth, and health status. In April of 2001, a similar study was conducted in Totten Inlet, WA state using cohorts of oysters planted in California; animals were monitored for mortality and growth. Temperature data were collected at all sites; phytoplankton abundance data were collected at the California sites. Mortality occurred only at the Inner Tomales Bay site where losses were correlated with maximum temperatures (r = 0.949) and preferentially affected faster growing oysters (r = 0.916). Significant differences in cumulative mortality were identified among oysters stocks and two of the three oysters stocks planted in the fall outperformed their cohorts planted in the spring (P < 0.0001). Microscopic changes in connective tissue and digestive tubules are consistent with previous observations of herpesvirus infections in oysters including: diffuse to multifocal pertibular hemocyte infiltration, diapedesis, dilation of the digestive tubules, nuclear hypertrophy, and chromatin margination. Nuclear hypertrophy and chromatin margination, in particular, are suggestive of herpesvirus infections; these histological changes were rare indicating the need to use multiple diagnostic methods when oyster herpesviruses are suspected to cause SSM. Temperature maxima (∼25°C) experienced at the Inner Tomales Bay site are not considered extreme for Pacific oyster survival; the association between oyster herpesviruses and temperature in Tomales Bay, California is discussed.

THE PROPER NAME FOR THE GEODUCK: RESURRECTION OF PANOPEA GENEROSA GOULD, 1850, FROM THE SYNONYMY OF PANOPEA ABRUPTA (CONRAD, 1849) (BIVALVIA: MYOIDA: HIATELLIDAE)

In 1849, Conrad described, illustrated, and assigned the name Mya abrupta to a new species of fossil bivalve collected from Miocene deposits along the banks of the Columbia River near Astoria, Oregon, during the United States Exploring Expedition of 1838–1842 (Conrad, 1849: 723, pl. 17, fig. 5a, b, USNM 3608; Figs. 1–3). Conrad described it as: “Subelliptical, slightly ventricose, widely gaping posteriorly. Surface marked with concentric undulations. Beaks separated, nearly medial, slightly prominent. Anterior margin acute, orbiculate; posterior margin abrupt, arcuate, somewhat reflexed; basal (inferior) margin arcuate; dorsal margin short, straight, nearly parallel with the base.” In 1850, Gould described the valves of a new extant species collected from the Nisqually region of Puget Sound, Washington, during the same expedition and assigned it the name Panopea generosa (Gould, 1850: 215, USNM 5894; Figs. 4–7). Gould (1852: 385–386; 1860, pl. 34, fig. 507, 507a) later figured and expanded the description: “Shell large and ponderous, chalky white, of a somewhat quadrilateral form, the basal and hinge margins being nearly parallel; the posterior extremity broadly truncated a very little obliquely, and the anterior extremity broadly rounded; anteriorly it gapes slightly, but posteriorly it gapes broadly, and the valves are here somewhat everted. The surface is coarsely undulated concentrically, and covered by an obliquely, and somewhat plumosely wrinkled, dirty yellow epidermis. The beaks are sharp and prominent, placed near the middle of the superior margin; the anterior umbonal slope is tumid, the posterior a little compressed. The hinge is rather slender, having a single elevated, erect, obliquely triangular tooth in each MALACOLOGIA, 2010, 52(1): 169−173

Shell Shape Differences between Two Panopea Species and Phenotypic Variation Among P. Globosa at Different Sites using two Geometric Morphometrics Approaches

ABSTRACT Most previous studies identifying Panopea generosa and P. globose have used non-rigorous visual methods as well as older shell measurement techniques. Newer mathematical methods based on shell shape variation allow for more accurate identification of clam species, as well as modeling of phenotypic differences due to environmental effects in populations in different sites. Interspecific shell morphology for two Mexican geoduck clam species was analyzed from a total of five sites off both coasts of the Baja California peninsula. In addition, intraspecific analyses of shell morphology were conducted for one of the species, P. globosa, at four sites along its reported distribution. Two approaches were employed for the analyses: a novel approach based on radiating lines to characterize shell outlines, and a more traditional approach using internal shell landmarks. In general, the novel approach afforded greater fidelity in distinguishing inter- and intraspecific variation. Our results from both methods agree with original species descriptions, and showed that Bahía Magdalena geoducks are P. globosa, thus revealing a wider distribution than previous reports for this species. The outline and internal scars were highly discriminant between the two species. Shell shape of P. generosa was also less variable than that of P. globosa. Intraspecific analyses of P. globosa shell shape suggest an adaptive or phenotypic response to environmental conditions at each site. Our results may also be indicative of reproductive isolation between Pacific P. globosa at Bahía Magdalena and conspecifics in the Gulf of California.

OXYTETRACYCLINE AS A TOOL TO MANAGE AND PREVENT LOSSES OF THE ENDANGERED WHITE ABALONE, HALIOTIS SORENSENI, CAUSED BY WITHERING SYNDROME

Abstract Research and captive rearing programs targeted to restore the endangered white abalone, Haliotis sorensen, are being conducted in California and Washington state. Captive rearing, whereas successful, has demonstrated that this species is highly susceptible to withering syndrome (WS), a rickettsial disease of abalone; WS has not been demonstrated in remnant wild white abalone populations. Thus, WS may limit white abalone production and supplementation of captive abalone must include measures to preclude the introduction of WS into wild populations. Oxytetracycline (OTC) is approved for use in aquaculture and has been demonstrated to effectively reduce rickettsial loads, WS development, and associated losses. White abalone were medicated at 90.82 mg/kg of OTC daily for 20 days and the efficacy, elimination, and potential to protect against exposure to the WS rickettsia were examined. This study illustrated that OTC effectively eliminates rickettsial infections. High concentrations of OTC (1,089 ppm) were observed in the digestive gland after medication; depletion occurred over a prolonged period providing protection to rickettsial challenge in abalone with a mean of over 72 ppm in this tissue. These data highlight the need for further optimization of this drug for use in commercial and restoration aquaculture.

Genetic Aspects of Restoring Olympia Oysters and Other Native Bivalves: Balancing the Need for Action, Good Intentions, and the Risks of Making Things Worse

ABSTRACT As interest and efforts in ecological restoration of native bivalve populations grow, the genetic implications of various restoration strategies are often unclear to resource managers and restoration practitioners, even though genetic considerations are vital to the ultimate success or failure of restoration endeavors. In an effort to fill this void, we present an overview of the underlying genetic concepts, a brief review of documented examples of native mollusc populations impacted by hatchery production, and a summary of the potential genetic impacts of restoration activities ranging from eliminating ongoing negative impacts with minimal genetic effects to intentional genetic manipulation of extant populations. We emphasize throughout the importance of understanding how adaptive, quantitative genetic variation is distributed within and among populations and the limitations of studies that address only selectively neutral molecular genetic variation. We also describe a conceptual framework for making genetically sound management and restoration decisions based on historical and current ecological and genetic considerations. Finally, because fully-informed decisions require a great deal of difficult-to-obtain data, we make suggestions on how to prioritize future research and outline practical measures that can be implemented in the absence of rigorous genetic data to prevent inadvertent negative genetic impacts by well-intended restoration efforts.

Validation of Age Estimation in Geoduck Clams using the Bomb Radiocarbon Signal

ABSTRACT Geoduck clams (Panopea generosa Gould 1850) are large, deep-burrowing bivalves distributed from southeast Alaska to Baja California. This species supports a lucrative fishery in the states of Washington and Alaska, as well as in British Columbia, Canada, and geoduck aquaculture currently supplies approximately 30% of the market. To manage this species effectively, it is important to elucidate the population age structure. Geoduck ages are currently estimated by counting valve growth rings. We used bomb radiocarbon (14C) to validate geoduck age estimates derived from counts of growth bands in thin-sectioned valve inner hinge plates. Seven specimens with presumed birth years before, during, and after the bomb testing period (1957 to 1967) were sampled from the first 3–5 y of growth, and subsequently assayed for 14C using accelerator mass spectrometry. The 14C values from each of our specimens compared with reference 14C chronologies for the northeast Pacific were in accord at estimated birth years. The temporal concordance validates current age estimation methods, and provides a first record of marine bomb radiocarbon in Puget Sound.

Development and Optimization of Quantitative PCR Assays to Aid Ostrea lurida Carpenter 1864 Restoration Efforts

ABSTRACT The Olympia oyster (Ostrea lurida)† is a prime candidate for the development of a rapid, high throughput, species-specific larval identification and quantification assay. We developed O. lurida specific DNA primers and a fluorescently labeled probe that amplify a mitochondrial DNA region cytochrome oxidase 1 subunit (COI) to use in quantitative polymerase chain reaction (qPCR). We also developed qPCRs for the specific detection of Neotrypaea californiensis and Upogebia pugettensis, two burrowing shrimp species that have been shown to have a negative effect on oyster bed habitat. The primer and probes amplified only the target organisms. Using standard curves constructed from known quantities of larvae, we are able to rapidly and accurately identify and estimate unknown quantities of larvae. In blind tests, direct counts of O. lurida larvae did not significantly differ from qPCR estimates. DNA was fully liberated from up to 80 O. lurida larvae, and 10 N. californiensis larvae; PCRs were not inhibited as demonstrated by an internal positive control multiplexed into the qPCRs. Genetic based assays are an extremely useful method for sorting complex plankton samples that can be more time and cost effective than traditional microscopy techniques. Our qPCR assay may prove to be a valuable tool to monitor O. lurida restoration site productivity as well as increase our understanding of this critical life history stage.

Optimal chemical triploid induction in geoduck clams, Panopea abrupta, by 6-dimethylaminopurine

Abstract The development of geoduck culture techniques coupled with increased market demand during the past decade led to cultured intertidal geoduck beds, over which concerns have arisen regarding the potential genetic risk posed by the reproductive contribution of hatchery outplants to wild stocks. Although an ongoing study to determine the genetic stock structure of Puget Sound geoducks has yet to yield definitive results, sterile triploids would enable geoduck culture to proceed irrespective of any genetic differences found, and may increase rate of growth. At 15 °C and salinity of 30?,we evaluated the suitability of cytochalasin B (CB) and 6-dimethylaminopurine (6-DMAP) for triploid induction in geoducks. Parallel tests of induction agent, start time, duration, and concentration were conducted on the same gamete pool. We found optimal triploid induction (92%) and suitable survivorship (30%) resulted from a 600 µM 6-DMAP treatment. This work enables the future examination of the efficacy of triploid induction for conferring sterility and increasing growth rate in this commercially valuable species.

Temporal Genetic Similarity among Year-Classes of the Pacific Geoduck Clam (Panopea GenerosaGould 1850): a Species Exhibiting Spatial Genetic Patchiness

ABSTRACT A previous study revealed genetic differences among collections of the commercially exploited geoduck clam (Panopea generosa) in Puget Sound, WA, but this heterogeneity did not follow an isolation-by-distance model. In this study, we investigated whether these differences were ephemeral or stable and tested predictions of the sweepstakes recruitment hypothesis, in which individuals show a high variance in reproductive success. We genotyped 11 allozyme and 7 microsatellite loci in 2,021 geoducks from 2 sites in Puget Sound and aged individuals by counting annuli in thin-section chondrophores under light microscopy. Genotypic data were then collated by year-class to test predictions of the sweepstakes recruitment hypothesis with allele count rarefaction, year-class relatedness, and 3 estimators of efective population size (Ne) using temporal shifts in allele frequencies. Although estimates of Ne were similar among year-classes, spatial shifts in allele frequencies and year-class strengths were detected among stations at 1 site, indicating that patchy settlement may be the result of an interaction between larval behavior during dispersal and hydrology.

Low Juvenile Pinto Abalone Haliotis kamtschatkana kamtschatkana Abundance in the San Juan Archipelago, Washington State

Abstract To investigate contemporary pinto abalone Haliotis kamtschatkana kamtschatkana recruitment events and juvenile abundance, 66 abalone recruitment modules (ARMs) were deployed at two depths and three sites in the San Juan Archipelago (Washington State) that were historically inhabited by substantial abalone populations. Based on published studies from California and British Columbia, ARMs are proven tools for surveying juvenile pinto abalone abundance. Abalone recruitment modules provide complex habitat and protection from predation. The ARMs were surveyed in situ for juvenile abalone abundance six times over the course of 26 months. Only eight abalones were observed, including three juveniles that were less than 50 mm (shell length). The mean density of juvenile abalones inhabiting the ARMs across all three sites during the 2006 surveys was 0.012/m2. The absence of juvenile abalones within the ARMs, combined with sharp regional declines in adult pinto abalone abundance, suggests limited local recr...