Biotechnology From the Perspective of Intensive Hybrid Striped Bass Aquaculture

Mark E. Westerman, James M. Carlberg, and Jon C. Van Olst

Kent SeaTech Corporation

11125 Flintkote Avenue, Ste.J

San Diego, CA 92121

mwesterman@kentseatech.com

Summary

Culture of hybrid striped bass (HSB: Morone saxatilis x M. chrysops) is a rapidly expanding component of U.S. aquaculture production and has potential to parallel the phenomenal success achieved in aquaculture of the closely related European seabass in the Mediterranean. Intensive culture of HSB presents many challenges and opportunities for integration of biotechnology with modern production technologies to enhance product value and quality, farm productivity, and environmental safety. At present, the industry is largely dependent on wild broodstock for fingerling production. Genetically superior domesticated broodstocks and reliable year-round fingerling production are required to continue expansion. Accomplishing this goal will require development of genetic markers and maps, along with breeding and maintenance of domesticated, genetically selected broodstock and germplasms. This will require the formation of consortia of industry, academic, and government participants with significant funding and in-kind contributions. Biotechnological approaches may be particularly relevant in the areas of immunology, pathology, diagnostics, epidemiology, and vaccine development. Safe, cost-effective vaccines and novel delivery strategies are critical for prevention of disease and limiting antibiotic usage in intensive aquaculture. Microbial mutagenesis and genomics/proteomics approaches should increase our understanding of pathogen virulence and accelerate characterization of strains and targets for both traditional and recombinant vaccines. Development of precision transgenic and reproductive control technologies should lead to safe, nutritious aquaculture products warranting consumer and environmentalist acceptance. Realization of the potential benefits of biotechnology to intensive aquaculture will require rational and well-defined science-based guidelines for development, certification, and regulation of recombinant animal health products and transgenic organisms. Widespread public education and rational debate on modern biotechnology and transgenics is recommended.

Keywords: aquaculture, biotechnology, intensive culture, hybrid striped bass, broodstock, selective breeding, genetic improvement, genomics, animal health, vaccines

Background and Significance

The complex nature of intensive aquaculture presents serious challenges and opportunities for modern biotechnology to play a role in enhancing aquaculture product quality and value to the consumer while lowering costs of production, and addressing environmental and safety concerns. One serious challenge to the successful application of biotechnology in aquaculture of most species is the lack of basic biological research in many areas critical to intensive production of aquatic species. This is particularly true for genetics, reproductive/developmental biology, immunology, physiology, nutrition, and animal health. Herein, however, lies an opportunity for application of biotechnological approaches to accelerate discoveries in basic research and their application to commercial aquaculture. Identification and citation of all the potential applications of biotechnology to intensive aquaculture is beyond the scope of this discussion. Instead, we will highlight a few key areas where we believe biotechnology can profoundly impact the intensive finfish aquaculture industry over a ten-year horizon. We will address these issues from the perspective of intensive HSB culture with the caveat that our recommendations should apply equally to other species raised in intensive systems, and in many areas, species produced in extensive culture systems.

High density, intensive culture of HSB in recirculating systems is a capital-intensive business. This technology developed from the observation that producing HSB under controlled conditions allows significant economic benefits due to environmental control and increased production efficiency that could not be achieved in extensive pond-based systems. Intensive aquaculture technologies employing modern water treatment and recirculation methodologies allow efficient and environmentally responsible use of land and limited water resources, especially when integrated with agriculture production. However, in order to be profitable, the capital-intensive nature of this production approach requires a relatively delicate balance between production schedules and high stocking densities, feeding rates, water quality, and disease prevention. Refinement of reproductive manipulation strategies in Morone sp. will allow development of genetically superior broodstock and fingerlings that are selected for performance in intensive culture. Selective breeding, along with advances in larval nutrition, diagnostics, and safe, cost-effective vaccines and therapeutics will secure the success of this resource-efficient approach to aquaculture production.

Broodstock development and genetic improvement. Integration of modern biotechnology approaches with the successful research and development strategies learned from decades of previous and ongoing USDA funded research on production animal genetics in cattle, pigs, and chickens, should allow rapid advances in aquaculture species to be achieved. This synergy will be particularly relevant in genetic marker development, linkage and physical mapping, QTL identification, marker-assisted selective breeding, and comparative genomics. Significant progress in the area of genomics and selective breeding has already been achieved in key aquaculture species such as catfish, trout, oysters, tilapia, and shrimp. However, at present a majority of producers in the HSB industry (as well as many other cultured species) are dependent on fingerlings produced from wild broodstocks. This approach to fingerling production has been sufficient to this point, but cannot support the rapidly expanding industry in the future. A selective breeding program based on partially domesticated and pedigreed broodstocks developed by university and industry is essential for development of genetically superior HSB fingerlings for aquaculture production. Wide variance for growth rate, feed conversion efficiency, tolerance of culture conditions, disease resistance, and other key traits suggests that performance of both striped bass and white bass will respond significantly to selective breeding programs. Genetic marker and map development, in parallel with "common garden" selection experiments conducted with multiple genotyped families in intensive and extensive commercial systems are important first steps in identifying families with desirable system-specific production traits. Rapid assessment of larval growth and cellular responses to formulated feeds via molecular methods can accelerate intensive fingerling production efforts based on genetically superior broodstocks. Other approaches to broodstock development such as sex reversal for production of monosex populations will also play a role in intensive aquaculture in coming years. Sex-specific genetic markers would be useful to accelerate these approaches to broodstock development.

Transgenic approaches to broodstock development. It is generally believed that transgenic approaches to development of healthy, value added aquaculture products that are grown in controlled aquaculture systems, will eventually be considered safe and desirable by a majority of U.S. consumers and regulatory agencies. In addition, it is thought that development of transgenic aquaculture strains will be a matter of necessity for many developing countries. The key to development of transgenic technology in the U.S. will be pursuing approaches that directly benefit the consumer by providing a stable supply of healthier and cheaper foods, while assuring environmental safety. Development of stem cell technology and precision genetic manipulation through cloning and homologous/molecular recombination with same species constructs may address many safety and consumer issues. Novel approaches to preserving gametes and embryos and genetic methods of inducing sterility may play key roles in insuring environmental safety of transgenic species. Widespread public education and extension efforts, along with rational public debate, are crucial first steps for this process. Support for development of novel transgenic approaches and transgenic safety research, along with widespread dissemination of results is recommended

Aquatic animal health in intensive aquaculture. Aquatic animal health is arguably the most important aspect of intensive finfish aquaculture in which modern biotechnology can play a major role. In HSB, bacterial diseases such as Streptococcus iniae can profoundly impact the economics of intensive culture through direct mortalities, and through effects on food conversion efficiency and growth. At present, only two antibiotics are approved for use in aquaculture and these have little efficacy for many diseases. In addition, the identity, biology, and virulence mechanisms, of most important aquaculture pathogens are poorly understood or unknown. Furthermore, in many species little or nothing is known of the animals' innate, humoral, or cell-mediated immune responses to infection. Modern approaches to understanding the cultured organisms' immune responses and the effects of high density culture is essential to integrated animal health programs. DNA sequencing is becoming a cost-effective approach to molecular identification and epidemiology of pathogens in some intensive aquaculture settings, but rapid and reliable diagnostic approaches are required. Bacterial molecular genetics approaches using gene expression, proteomics, and mutagenesis have great promise to contribute to our understanding mechanisms of bacterial virulence and identifying targets for vaccine development

The inherent drawbacks and costs of antibiotic usage in intensive aquaculture have led to increased interest in the development of vaccines and vaccination as a routine part of an animal health program. In Norway, increased vaccine use in salmon has had positive impacts on the environment, due to a significant reduction in antibiotic usage. However, vaccine developers have been slow to focus on the aquaculture industry and few approved vaccines are available, even for the most prevalent pathogens. Widespread adoption of routine vaccination will require development of safe, cost-effective vaccines and vaccine delivery systems. Long lasting oral or immersion vaccination of fingerlings prior to stocking into production systems would greatly benefit intensive HSB aquaculture. Traditional and modified bacterins or formalin-inactivated whole cell suspensions of bacteria currently are the focus of many vaccine developers, since they are cost-effective to develop and utilize in aquaculture. However, a more important consideration in some cases, is the cost and time involved in the approval process. Consideration of expediency rather than efficacy may be inhibiting development and utilization of alternative, and possibly more efficacious vaccines, such as live-attenuated, recombinant, and DNA vaccines. Clearly defined procedures for development and certification of novel biotech animal health products along with sufficient human resources for review of new applications will be critical to timely development of vaccines for aquaculture.

Conclusions and Recommendations

Intensive aquaculture presents serious challenges and opportunities for the application of modern biotechnology. With many species, basic infrastructure and research is needed to realize the benefits of biotechnological approaches. The USDA can positively affect development of the U.S. aquaculture industry by fostering multifaceted collaborations, graduate/postdoctoral training, and both basic and advanced research using modern biotechnology approaches.

Short term (1-3 years)

-Identify and support development of key species of importance to the U.S. aquaculture industry based on sound economic analysis involving U.S. costs of production and global competition

-Provide extramural funding and/or agency facilities (and human resources) for domestication and maintenance of valuable aquaculture broodstocks and their germplasms

-Organize and support industry/university/government research consortiums with expertise and essential resources dedicated to selective breeding and animal health of key species

-Restore private organizations as qualified recipients for USDA IFAFS or similar USDA funding initiatives

-Support development of mapping reference families for construction of linkage maps of economically important aquaculture species

-Support development of large numbers of informative genetic markers and medium to high density linkage maps of economically important species

-Support and conduct research on advanced fingerling and seed stock production technology and development of biotech tools that will accelerate these efforts

-Support and conduct research on aquatic animal immunology and health

-Support research and development of functional genomics/proteomics approaches to vaccine development and study of pathogen virulence

-Support research and development of recombinant protein and DNA vaccines and their safety

-Establish rational and well-defined science-based guidelines for development, certification, and regulation of recombinant vaccines, adjuvants, and biologics

-Dedicate more human resources for review and certification of vaccines and related products

-Support industry/university graduate fellowships and postdoctoral training for biotechnology in aquaculture

-Develop rapid response, small grant funding programs for high impact exploratory research in biotechnology by industry and university researchers

-Initiate and promote widespread public education and rational public debate on the potential benefits and risks of transgenic technologies for the U.S. consumer

Mid-term (4-7 years)

-Identify quantitative trait loci (QTL) associated with important intensive production traits and begin marker-assisted selective breeding based on these traits

-Construct large-insert (BAC) libraries and physical maps of important aquaculture genomes

-Support comparative genomics studies to identify regions of synteny between aquaculture species and between other production animal species

-Develop and test gene expression and microarry approaches for studies of animal performance, nutrition, diagnostics, epidemiology, pathogen virulence, and disease

-Develop databases and comparative software tools allowing comparison of the genomes of key species and pathogenic microbes.

-Conduct and support research on fish embryonic stem cells and precision transgenic approaches that can benefit consumers and the environment

Long-term (8-10)

-Review progress in application of biotechnology to aquaculture and adapt research and funding priorities to assimilate recent advances in medical and agriculture biotechnology