Performing Department
(N/A)
Non Technical Summary
Oyster farming provides significant social and economic values in coastal communities. More recently, there is growing awareness of its environmental value. Farmed oysters require minimal energy and feed, filter a significant volume of water, and remove carbon and nutrients from the sea at harvest. Growers, however, face increasingly urgent threats from environmental change, directly or indirectly attributable to climate change, that will likely become more significant in the future. These environmental stressors create the potential for large reductions in shellfish yields in the years ahead. Urgent research is needed to apply the knowledge in shellfish genetics and breeding to large-scale efforts to advance the aquaculture industry and improve farmed stock for oyster growers.There is growing evidence that crossbreeding, a breeding innovation contributing to the massive improvement for major land crops, can substantially improve yields for the Pacific oyster,the largest crop in theU.S. West Coast shellfish industry. The primary goal of this SBIR Phase II project is to develop non-GMO, hybrid oysters optimized for different growing conditions through crossbreeding and rigorous on-farm trials. Different hybrid oysters will be evaluated for the entire production cycle from developmental stages in the hatchery, through two growing seasons, to harvest. Experimental animals will be deployed at multiple farm sites to evaluate the impact of various ocean conditions on the performance of farmed stocks. This proposal builds on proven cases of hybrid vigor in marine bivalve shellfishand established facilities and resources of Pacific Hybreed. Anticipated outcomes of this research will provide the aquaculture industry optimized hybrid seedto capitalize on benefits of hybrid vigor and to establish important biological resources for the research community.
Animal Health Component
75%
Research Effort Categories
Basic
25%
Applied
75%
Developmental
(N/A)
Goals / Objectives
Our majorgoal for this SBIR Phase II project is to commercialize hybridoysters for the U.S. West Coast industry through crossbreeding and on-farm trials at multiple farm sites. Specific objectives include,(1) production ofthree cohorts of hybrid lines, with up to 40 new hybrid varieties in each cohort; (2) production oftwo cohorts of double-cross hybrid lines, with up to 10 double-hybrid varieties in each cohort; (3) evaluation of hybrid lines at farm sites in Alaska, California, and Washington during twogrowing seasons for field growth, survival,reproductiveconditions, and disease resistance.
Project Methods
Production of single-cross and double-cross hybrids.Single hybrids will be generated by diallel crosses of partially inbred lines. Up to 42 hybrid lines will be produced from each 7×7 diallel cross. We propose to conduct three production runs of single crosses, using inbred lines produced in 2023 in the Phase I project and those that we propose to produce in this Phase II project. Besides single hybrid production, two production runs of double-hybrid lines will be conducted in 2025 and 2026. For each double cross, two single-hybrid lines will be selected based on their yield performances and mated to produce a double-hybrid line. Predicted yield of each double hybrid will be calculated based on the average yield of the four single hybrids constituting the double-hybrid line and will be compared with the actual, on-farm yield.Larval rearing and juvenile nursery.Genotyped broodstock will first be conditioned under a temperature ramping protocol and supplied with microalgae. Once broodstock have reached proper spawning conditions, oysters will be shucked and female gametes removed directly from the gonad into filtered seawater. Eggs will be rinsed on a 20-μm screen prior to enumeration. Male oysters within each family line will be similarly spawned and sperm collected into microcentrifuge tubes kept on ice. Sperm cells will be added to seawater just prior to use. For a diallel cross, a minimum of 7 million eggs will be required from each female oyster, which will be crossed with males from each of the seven inbred lines. Eggs will be allocated to individual 1-liter beakers at a density of 1 million eggs l-1. A full factorial, diallel mating scheme will be conducted, whereby male and female parents from each inbred line are crossed in all possible 49 pairwise combinations.Fertilized eggs will be reared in 50-l cylindrical culture vessels containingseawater at 24°C. Larvae will be fed the alga Tisochrysis lutea starting at 1-day post-fertilization and augmented with algae Chaetoceros mulleri and Tetraselmis sp. as needed during later larval stages.Different species of microalgae will be collected into a header tank, from which algal feed will be supplied into larval culture vessels. Algal cell density in larval cultures will be maintained between 30,000 and 50,000 cells per mlthroughout the larval phase. Every two days, a complete water change will be conducted for all larval cultures.When the pediveliger stage of development is reached, larvae will be collected and induced to settle by exposing competent larvae for one hour to 25 µM epinephrine in 25°C seawater. Larvae will subsequently be screened out of the epinephrine solution and placed into a 'down-welling' setting silo. Each silo is fit with an appropriate mesh size and a downward stream of filtered seawater, containing microalgae for feed during metamorphosis. After newly set individuals have reached the size that can be retained on a 1-mm mesh screen, they will be transferred to 'up-welling' silos where juvenile oysters are fluidized by upward flow of filtered seawater through the mesh screen. Modified fiberglass tanks, each containing up-welling silos, are supplied continuously with seawater and algal feeds containing the same algal species for feeding larvae. Oysters will be maintained in this nursery until reaching 3 mm in shell height at which size they will be transferred and deployed at farm sites for yield assessments.On-farm trials.At ~3-mm shell heights, seed of each hybrid line will be allocated to four replicates per farm site. Each replicate will be weighed and counted and subsequently transferred to a seed rotating cylinder developed by PH researchers (3-mm mesh-size, 1-foot length). Each field cylinder will be stocked with 50 seed oysters and placed into field culture at test sites in Washington, California, and Alaska. A total of 800 oysters per family will be deployed in a randomized block design. For each cohort of hybrid lines, up to 672 cages will be deployed across sites. In the second year of the project, the number of cages will double to accommodate deployment of two cohorts produced in different years.In addition to evaluation of seed, yearlings of different hybrid lines will be monitored during the second field season. Oysters of each hybrid line will be stocked infour replicates and initial weights and counts measured. Growth, survival, shell morphometrics (width, length, and depth), and reproduction conditions will be evaluated at the end of the field season.For family lines out-planted at the California site, an additional sample of 10 oysters per family line will be collected for PCR and pathological evaluation ofOstreid herpesvirus-1 DNA.Statistical analyses.For evaluation of field performances for single hybrids, a Bayesian hierarchical modelwill be used to estimate components of variance in yield, including general combining ability, specific combining ability, and reciprocal effect. Performances of double hybrids will be predicted using modeled yields for each single hybrid line based on combining abilities of the inbred parents. Predicted double-hybrid yields will be compared with the actual yields observed in on-farm trials.Analysis of effects of farm sites on yield will be estimated using a general linear model (Final weight = initial weight + final count + family + site + family×site). For determination of uniformity, the Z statistics will be used to compare size distribution between hybrid lines and between hybrid lines and commodity seed grown on different farms.