Location: Pacific Shellfish Research Unit
2020 Annual Report
Objectives
The long-term goal of this project is to develop an improved understanding of the ecology of bivalve shellfish aquaculture in the estuarine environment in order to increase production by reducing mortality while ensuring that culture practices are sustainable and environmentally acceptable. Bivalves are reared on privately owned or leased tidelands in US West Coast (USWC) estuaries. This project addresses several sources of juvenile mortality and quantifies them at the estuarine landscape scale. Sub-objective 1A advances previous work on annual recruitment of larval and juvenile burrowing shrimp pests by determining whether management practices on aquaculture beds influence shrimp recruitment and subsequent survival. Juvenile shellfish are also subject to emerging pathogens like ostreid herpes virus that have the potential to severely impact oyster farming and to changing water chemistry which is known to cause problems with shell formation and growth of larvae in the hatchery, but has largely unknown effects on juveniles thereafter. Subobjective 1B aims to monitor juvenile oyster growth and mortality along estuarine gradients and determine whether planting practices can improve oyster growth and survival. Finally, USWC shellfish production is also constrained by regulatory actions regarding siting shellfish farms in the estuarine environment. Subobjectives 1C and 1D seek to model the interaction between shellfish culture production, burrowing shrimp and aquatic vegetation at the estuarine seascape scale and describe the function of these habitats for managed species of estuarine fish and invertebrates.
Objective 1: Develop management practices for shellfish aquaculture that reduce juvenile mortality and optimize estuarine habitat function.
Subobjective 1A: Quantify and model burrowing shrimp recruitment patterns to shellfish beds in West Coast estuaries to determine whether various bed management practices influence shrimp recruitment and survival at the landscape scale. (Dumbauld)
Subobjective 1B: Quantify juvenile oyster growth and mortality at the landscape scale comparing habitats and locations as potential factors that reduce effects of stressors including reduced carbonate saturation states and disease vectors. (Dumbauld)
Subobjective 1C: Quantify the effects of oyster aquaculture and burrowing shrimp on aquatic vegetation and verify models developed to examine this interaction at the estuarine landscape scale using new tools. (Dumbauld)
Subobjective 1D: Quantify the function of intertidal habitats including oyster aquaculture for managed species of fish and invertebrates at the landscape scale.(Dumbauld)
Objective 2: Advance and implement genome-enabled improvement technologies for the Pacific oyster.
Approach
Conduct research to understand the ecology of bivalve shellfish aquaculture in the estuarine environment in order to reduce mortality and increase production while ensuring that culture practices are sustainable and environmentally acceptable. Evaluate several sources of juvenile oyster mortality and quantify effects at the estuarine landscape scale by: 1) examining annual recruitment of larval and juvenile burrowing shrimp pests to determine whether management practices on aquaculture beds influence shrimp recruitment and survival, and 2) monitoring juvenile oyster growth and mortality along estuarine gradients and determining whether planting practices can improve oyster growth and survival in the face of emerging pathogens like ostreid herpes virus and altered seawater water chemistry that have the potential to severely impact oyster farming. Develop a multidisciplinary approach in collaboration with Oregon State University, University of Washington, and other scientists to model the interaction between shellfish culture production, burrowing shrimp and aquatic vegetation at the estuarine seascape scale and describe the function of these estuarine habitats for managed species of estuarine fish and invertebrates. Work with outreach and extension personnel to transfer technology to managers and shellfish industry.
Progress Report
This report documents progress for project 2072-63000-005-00D, "Improving the Sustainability and Productivity of Shellfish Culture in Pacific Estuaries." It replaces and continues research from projects 2072-31000-005-00D, "Genetic Improvement of Oyster Stocks for the Pacific Northwest," and project 2072-63000-004-00D, "Developing Methods to Improve Survival and Maximize Productivity and Sustainability of Pacific Shellfish Aquaculture," which were merged.
Progress towards the Sub-objective 1A included choosing sites for and implementing a survey of burrowing shrimp populations on shellfish aquaculture beds in two estuaries where previous annual surveys have occurred in dense shrimp colonies for the last 10 years. The study compares the recruitment of juvenile burrowing shrimp to shellfish culture beds with that to dense colonies of shrimp outside these culture areas. Subsequent surveys will then be conducted to follow shrimp survival over time to determine whether culture practices themselves might influence both of these processes. We also established some transects across tide heights at two locations in Willapa Bay, Washington, where we are monitoring predation on shrimp by staghorn sculpins and the presence of a nematode parasite in the shrimp. Baseline information on shellfish and older shrimp is present in both of these surveys, but shrimp recruitment and subsequent survival won’t be assessed until late fall 2020 and spring 2021 respectively.
Sub-objective 1B focuses on juvenile oyster mortality and/or reduced growth due to ocean acidification (OA) and the oyster herpes virus (OsHv-1). Progress was made on examining both of these factors in 2020. Most documented effects of OA have been shown to affect oyster larvae during initial shell formation or at metamorphosis when they settle to become juveniles or seed. The U.S. West Coast aquaculture industry has adapted to this problem by buffering and changing water chemistry in shellfish hatcheries, but seed may still be vulnerable and researchers have shown that eelgrass, an estuarine plant, can modify water chemistry and its effects on these spat via photosynthesis and carbon dioxide (C02) uptake. ARS researchers deployed oysters at locations along the estuary gradient in water chemistry and found that the effect of eelgrass might be site-specific because other factors such as food concentration and presence of fouling organisms also varied by location. Progress in 2020 included analyzing data from an experiment conducted in 2019 to examine the effect of eelgrass on oyster survival and growth in two estuaries with potentially different gradients and collecting additional data on environmental parameters and site characteristics.
Progress was made towards examining OsHv-1 as a source of juvenile oyster mortality, which is also part of Sub-objective 1B. This included designing and initiating a “sentinel’ program to track the presence of this virus in juvenile oysters deployed at five locations from San Diego Bay, California, to Totten Inlet, Washington. A susceptible family of genetically uniform hybrid oysters was chosen to be deployed at all sites making mortalities detectible if the virus was present. The study design allows for mortality to be compared to that observed in a second family of disease resistant oysters deployed in Tomales Bay, California (where one strain of the virus is present), and Willapa Bay (where no virus has been recorded). Plantings at these two sites were made alongside a larger group of families where the selective breeding program continues to be implemented. Oysters were spawned in April, raised in the Oregon State University (OSU) Molluscan Broodstock Program (MBP) hatchery, and shipped to cooperating shellfish growers who will assist by monitoring mortality and shipping a subset of oysters to project collaborators for virus detection and enumeration at approximately two week intervals over the summer. Sentinel deployment locations were chosen to be adjacent to other long-term monitoring efforts so that environmental parameters could be assessed and samples will be assessed for the presence of bacteria that have been associated with OsHv-1 mortality in other countries.
Progress towards Sub-objective 1C concerns the use of intertidal estuarine habitats including oyster aquaculture by fish and invertebrates. Research involved a re-examination of spatial models previously used to predict eelgrass cover in Willapa Bay and quantify its interaction with shellfish aquaculture at the estuarine landscape scale so that the interaction with burrowing shrimp could also be quantified. Spatial data collected for burrowing shrimp presence across the whole estuary in 2006 and across sub-areas within the estuary in subsequent years was incorporated into the model. An effort to collect and ground truth new bay-wide aerial photography was initiated and collaborations established to collect data for regions of the estuary using new angle of view (AOV) photography platforms. This is important because regulations developed by management agencies to protect eelgrass as essential nursery habitat for commercially valuable fish, like English sole and salmon, restrict expansion of new shellfish culture in areas where eelgrass is present and permits for existing culture operations where eelgrass is present in Washington state have been recently challenged. These regulations do not currently consider aquaculture as habitat and instead simply minimize its potential effect on eelgrass. This research will be immediately useful for permitting decisions regarding both current and proposed expansion of aquaculture in U.S. West Coast estuaries.
Finally, progress was made on research to utilize quantitative and molecular genetics techniques to improve the performance of cultured Pacific oysters in the face of OA and OsHv-1 in U.S. West Coast aquaculture. A third generation of OsHv-1 disease resistant families was selected, paired matings made in the hatchery, and juvenile oysters planted in Tomales Bay and Willapa Bay. Growth and survival will be evaluated and compared with non-selected controls at selected time-points in both estuaries. Laboratory evaluations exposing oyster spat to known viral strains from France and Australia, will be trialed and conducted at an OSU quarantine facility in Corvallis, Oregon. A second experiment to evaluate the effects of acidified seawater on pooled families of larval oysters and spat in the hatchery was initiated to determine additional effects of hatchery conditions (especially algae and bacteria). Progress also continued towards assembly of a new high quality genome for the Pacific oyster.
Accomplishments
