The goal of this project was to investigate and document the presence of disease agents in cultured and wild oyster populations throughout California. This is the first comprehensive survey to be conducted since that of Katkansky and Warner in the late 1960s to early 1970s (Katkansky and Warner, 1974). Particular emphasis was placed on detection of the agent of Denman Island Disease (Mikrocytos mackini, Farley et al., 1988). This pathogen of the Pacific oyster (Crassostrea gigas) was detected in the State of Washington in 2002, and many California oyster growers receive seed from Washington State. All major populations of farmed and feral commercial oysters and wild native oysters Ostrea lurida were targeted for sampling. Sufficient numbers from each population were collected so that relatively rare pathogens should have been detected when they are present.

Withering syndrome is a chronic, often fatal disease of multiple species of California abalone. It was first observed in the mid-1980s at the Channel Islands off Southern California and has since spread along the main coastline as far north as the San Francisco bay area. Recent research has demonstrated that the causative agent is a Rickettsiales-like prokaryote (WS-RLP, Friedman et al. 2000), and that WS expression is much more rapid and severe at elevated water temperatures (Moore et al. 2000). Aside from impacts on wild populations, WS has resulted in substantial losses in red abalone farms. As a result of these losses and our observation that the WS-RLP is sensitive to tetracyclines, we developed and oral administration of oxytetracycline in conjunction with researchers at The Abalone Farm, Inc.

The white abalone , Haliotis sorenseni, supported valuable commercial fisheries only 30 years ago. In 2002, this species became the first marine invertebrate in the United States to achieve federal endangered species status. The overall goal of this project was to collect life history, genetic and disease susceptibility data that to support recovery.

Withering syndrome (WS) is a catastrophic disease of both wild and cultured abalone caused by “Candidatus Xenohaliotis californiensis”, a Rickettsia-like procaryote (WS-RLP). Losses from this disease have severely hampered the abalone aquaculture industry and abalone restoration efforts in California. Oxytetracycline (OTC) was recently demonstrated to be an effective therapeutant for WS-RLP infections and associated losses due to WS. In addition, a long duration of protection (approximately one year) was noted anecdotally. Part one of this study examined the efficacy and pharmacokinetics of OTC treatment in red abalone, Haliotis rufescens, held at 13.4oC. Medication was administered orally in an artificial diet containing 1.85% active OTC at a rate of 103.4 mg/kg abalone for 10, 20 and 30 days. Control abalone were fed the same diet lacking OTC. Significant differences in prevalence and intensity of infection in both the post-esophagus and digestive gland were observed. Although the digestive gland from abalone medicated for 10 days and foot muscle from those medicated for 30 days was best described with a two-compartment model, pharmacokinetic trends were adequately described by a one-compartment model. Significant differences in OTC accumulation and depletion were observed among treatments. Animals medicated for 10 days accumulated significantly less than those medicated for 20 or 30 days. Despite this, terminal elimination rate constants were similar. Significantly less OTC was present in foot muscle samples relative to corresponding digestive gland samples. Estimated half-life values were similar among treatments for both foot muscle (10.7-13.4 d) and digestive gland (23.8-27.5 d) samples.

Once harvested commercially, the white abalone (Haliotis sorenseni) is in danger of extinction and since 2002 has been under the protection of the federal Endangered Species Act. Recent failed efforts to find remnant populations in the species’ historical deep-seafloor habitats underscore the animal’s scarcity. In the time between when the grant for the project was written and funded, NOAA Fisheries halted the collection of wild white abalone for research. It now appears that species recovery is either going to happen on its own over the course of several or more decades, or captive-bred white abalone will have to be outplanted in the wild. Outplanting is not without its own set of risks, as it may erode genetic diversity or introduce the withering syndrome pathogen into previously uninfected deep-water refuges. Just as worrisome is the potential to unknowingly introduce previously unknown pathogens.

The sabellid polychaete Terebrasabella heterouncinata (Fitzhugh & Rouse 1999) has a unique life history in which larvae settle on the edge of gastropod shells and rely on shell deposition to create a tube with an opening to the exterior. This worm was accidentally imported to California, USA on abalone from South Africa in the 1980s and spread with abalone shipments to most culture facilities and some public aquaria throughout the state. Its ability to infest California's native gastropods has sparked concern regarding potential establishment in intertidal habitats adjacent to facilities that held sabellid-positive abalone. We examined the ability of T. heterouncinata to transmit between individual turban snails, Tegula funebralis. We found that transmission between T.funebralis did occur, but at a significantly slower rate than that between red abalone Haliotis rufescens. During 2002 to 2006 native gastropods (turban snails and limpets) were collected at most sabellid-exposed sites and no T. heterouncinata were detected; it thus appears that this species has not become established in California. Freshwater exposure was examined as a method to kill T. heterouncinala in shell fragments that may remain after abalone are removed from production or display units. Freshwater immersion for up to 8 hours but not 16 or 32 h resulted in survival of adults and/or larvae resident in brood chambers. In a similar study, motile T. heterouncinata larvae were found to survive up to 32 see of freshwater exposure, whereas none survived a 64-sec exposure. These data can be used by abalone culture and display facilities to establish reliable sanitization procedures to prevent T. heterouncinata transmission or reinfestation.