By: Linnea K. Andersen, Jason Abernathy, David L. Berlinsky, Greg Bolton, Matthew M. Booker, Russell J. Borski, Travis Brown, David Cerino, Michael Ciaramella, Robert W. Clark, Michael O. Frinsko, S. Adam Fuller, Steve Gabel, Bartholomew W. Green, Eric Herbst, Ronald G. Hodson, Michael Hopper, Linas W. Kenter, Frank Lopez, Andrew S. McGinty, Barry Nash, Matthew Parker, Stacey Pigg, Steve Rawles, Kenneth Riley, Marc J. Turano, Carl D. Webster, Charles R. Weirich, Eugene Won, L. Curry Woods III, Benjamin J. Reading, StriperHub *
This review article developed by researchers and collaborators at the North Carolina State University and contributors from other four states analyses the current status of striped bass aquaculture and its potential as a U.S. aquaculture industry, primarily from an Atlantic state perspective. This summarized version focuses on sections two and three, which describe the standard methods and tools available for striped bass culture and present the future directions of the striped bass aquaculture industry, including the challenges towards establishing a culture industry for this species, as well as the launch of the new StriperHub consortium.
Only one-third of global aquaculture products are raised in marine waters, which presents an opportunity for industry expansion, as these marine resources and species are currently underutilized in the United States and other countries (Froehlich, Gentry, & Halpern,2018). The expansion of marine finfish production is hindered by the limited number of appropriate species choices. Atlantic salmon, Salmo salar and red drum, Sciaenops ocellatus are currently the only finfish species endemic to the United States that are cultured in significant quantities in coastal environments, and presently there is no appreciable aquaculture production of any premium white-fleshed marine finfish species, such as the striped bass, in the country.
Candidate aquaculture species identified by the National Oceanic and Atmospheric Administration (NOAA) must command a premium price, have high consumer demand, and successfully adapt to rearing in localized environments for profitable production. The striped bass meets all these criteria and therefore has great potential for commercialization in the United States (Reading, 2017; Reading, Hinshaw, & Watanabe, 2014).
Striped bass culture methods and tools
Most cultured fishes in the United States, and the world, originate from wild-caught fish or fish that are not domesticated or selectively bred for genetic improvement (Gjedrem & Baranski, 2010; Knibb, 2000; Teletchea & Fontaine, 2014). A domesticated line of striped bass originally obtained from six distinct geographic stocks has been bred in captivity for six generations as part of the National Program for Genetic Improvement and Selective Breeding for the Hybrid Striped Bass Industry (Garber & Sullivan, 2006; Hodson et al., 1999; Reading, McGinty, et al., 2018; Woods III, 2001).
“Except for salmonids, this is the only marine aquaculture finfish species in the United States with an established domestic strain of fish available to producers and currently being used for commercial production.”
Genetic improvement of finfish broodstock is a critical advancement for aquaculture industry success. Breeding programs provide selectively bred fish for optimal culture and performance traits, such as disease resistance, growth rate, efficiency, acceptance of prepared diets, and tolerance to crowding and stress conditions, among many others.
Performance gains of domesticated fish can be dramatic in comparison to their wild-origin counterparts. For example, gains in body weight at harvest are estimated to be approximately 14% per generation of selectively bred Atlantic salmon (Gjedrem, 2010). Similarly, domesticated strains of striped bass have been shown to have superior performance for some culture traits (Reading, McGinty, et al., 2018).
There are marked improvements in domestic striped bass growth performance between filial generations captively bred over the last 17 years as evaluated by weight at age. For example, sixth-generation captive-bred domestic striped bass (F6) are about twice the size of third-generation fish (F3) by Age 2, and fifth-generation (F5) female striped bass are about 46% larger than F3 female striped bass at the age of 4 years (see Figure 2).
“Candidate aquaculture species identified by the National Oceanic and Atmospheric Administration (NOAA) must command a premium price, have high consumer demand, and successfully adapt to rearing in localized environments for profitable production.”
When considering the average improvement in domestic striped bass growth performance for each captive-bred generation, we see 33.8% growth gain between F3 and F4, 26.9% growth gain between F4 and F5, and 24.0% growth gain between F5 and F6. These are fish reared in outdoor tanks and pools at semi-commercial density.
The timeframe required for domestic striped bass to grow to about 1,000 g (2.20 lb) in these conditions, which is the desired market size for the hybrid striped bass, has been dramatically reduced by 69% through breeding between the F3 and F6 generations (see Figure 3). Furthermore, the time to grow to the desired market size of 1.36 kg (3 lb), which was identified as a target for white-fleshed marine fish such as striped bass, is about 32 months for F3 generation, 29 months for F4 generation, 28 months for F5 generation, and 24 months for F6 generation fish.
“Recent studies have demonstrated that female reproductive potential in the domesticated striped bass is superior to that of equal-sized females captured from the wild using a manual strip spawning method.”
Thus, selective breeding has taken the F3 generation fish, which were not economically feasible to grow to this market size over a 32-month timeframe, to within the economically viable timeframe of 24 months or less by the F6 generation of breeding. Overall, this is a 75% reduction in the grow-out time to market obtained through just three generations of selective breeding. The F7 generation of domestic striped bass, first created in 2020, will likely have further improved growth performance over the next four or so years.
Recent studies have demonstrated that female reproductive potential in the domesticated striped bass is superior to that of equal-sized females captured from the wild using a manual strip spawning method (Locke, Sugg, Sullivan, & Turano, 2013). Additionally, domestic striped bass have an improved dress-out weight (0.5–4.0% increase compared with wild-origin fish (Reading, McGinty, et al., 2018), and, importantly, a 13–25% significantly better feed conversion efficiency (p < .05), with feed conversion ratio (FCR) values <1.1 (Kenter, Kovach, Woods III, Reading, & Berlinsky, 2018).
The presumed FCR for striped bass raised at commercial density is approximately 1.5 or slightly higher. Collectively, this domestic striped bass broodstock program has produced a fish suitable for commercial grow-out economics. However, the use of wild-origin striped bass stocks may be critical for offshore culture in some regions due to escapement concerns (e.g., Northeast Atlantic and Gulf of Mexico), and as such, it is important to extend reproduction and larviculture technology of these fish to those regions as appropriate for the U.S. striped bass aquaculture industry to thrive.
Reproduction and larviculture
A major constraint to the culture of any marine fish species is the complexity of larval rearing and the ability to produce a reliable source of juveniles for culture (Planas & Cunha, 1999). However, this bottleneck has already been addressed in the culture of striped bass, which have comparatively simple requirements for larviculture and are similar to that of salmonids, one of the only successful marine finfish aquaculture industries in the United States. (Editor’s note: for full background on the early stages and development of the research on this topic, please access the full version of this article cited and linked at the end of this content).
Larval striped bass can be raised to fingerlings at a commercial scale in earthen ponds using natural productivity through fertilization (Harrell, 1997; Ludwig, 1999). This infrastructure is currently in place at many aquaculture operations utilizing pond systems, particularly at commercial hybrid striped bass fingerling operations.
Pond sizes for larviculture are typically smaller than for grow out and, therefore, not available at all commercial hybrid striped bass rearing facilities. Intensive larval rearing for fingerling production in tank systems is generally constrained to the use of live feeds, and challenges are not as well described as compared to other life stages. Further research on commercially scalable methods of intensive larval rearing is needed and is currently being conducted. Collectively, the larval and juvenile seed-stock supply for striped bass is presently achievable at a commercial scale in the United States.
Rearing and grow out
Striped bass have been shown to adapt well and exhibit high survival in RAS technologies and cages. Laboratory-scale RAS studies show that striped bass exhibit equivalent growth performance in freshwater, brackish, and saltwater environments (Kenter et al., 2018).
Experimental-scale studies of striped bass in cage culture show that fish grow better than hybrid striped bass in brackish water with little impact on survivorship (Woods, Kerby, & Huish, 1983). Significant progress has been made on growth biology in striped bass including seasonally based feeding protocols; characterization of growout temperature (Harrell, 1992); demonstration that a range of salinities are equally effective in regulating growth (Harrell, 1992; Kenter et al., 2018); nutrient requirements, endocrine and growth physiology (Picha et al., 2009, 2014; Picha, Turano, Beckman, & Borski, 2008; Picha, Turano, Tipsmark, & Borski, 2008; Won & Borski, 2013); and experimental scale studies suggesting a potential for culture of 1.36– 2.27 kg (3.00 5.00 lb) fish.
“Clarity on policies relevant to commercial aquaculture (e.g., production, product transport) is also imperative to developing a striped bass aquaculture industry.”
However, none of this research has provided insight into commercial scaling or stocking densities typical of intensive culture requirements or economic analyses for the full production cycle from egg to plate of domestic or wild striped bass. Currently, data suggest that striped bass can be grown in cages and under RAS at different salinities. Despite this work, one major constraint has been a lack of demonstration that striped bass can be economically cultured at commercial scale.
Genomic resources and tools
The striped bass is a priority species for the United States Department of Agriculture (USDA) National Animal Genome Research Support Program (NRSP-8), and as such considerable progress in establishing genomic resources for striped bass has been accomplished. The striped bass genome assembly was recently updated (2019) through a combinatorial approach of short-read sequencing (Illumina, San Diego, CA), long-read sequencing (Pacific Biosciences, Menlo Park, CA), and Chicago® and Dovetail™ Hi-C + HiRise™ scaffolding (Dovetail Genomics, Scotts Valley, CA).
This genome assembly (NCSU_SB_2.0) is publicly available under GenBank accession GCA_004916995.1 and is currently in the annotation pipeline. This genome assembly has a total sequence length of 598,109,5477 base pairs and consists of 629 scaffolds (Abdelrahman et al., 2017; Andersen, Baltzegar, Fuller, Abernathy, & Reading, 2019; Reading, McGinty, et al., 2018).
“The Striper Hub is a Sea Grant-supported network that was formed to facilitate striped bass aquaculture. The hub aims to overcome barriers to industry development and expansion by demonstrating and promoting commercial-level culture, economics, and marketing of U.S. striped bass.”
Other genomic resources available for striped bass include a medium-density genetic linkage map of 289 polymorphic microsatellite DNA markers (Liu et al., 2012), 23,000 unigene sequences from a multi-tissue transcriptome (Li, Beck, Fuller, & Peatman, 2014; GenBank accession GBAA00000000), and a well-annotated transcriptome of 11,200 unigene sequences derived from ovary representative of all stages of oocyte growth and maturation (Reading et al., 2012; GenBank accession SRX007394).
A number of studies have reported the development of microsatellite DNA markers for striped bass (Brown, Baltazar, & Hamilton, 2005; Couch et al., 2006; Han, Li, Leclerc, Hays, & Ely, 2000; Rexroad et al., 2006; Skalski, Couch, Garber, Weir, & Sullivan, 2006). Epigenetic studies on striped bass are limited to sperm methylation profiles and their correlation to fertility (Woods III et al., 2018).
Additional resources are also available for closely related Moronids including a reference genome sequence assembly for white bass (Abernathy et al., 2019), the multi-tissue transcriptome of 22,000 unigene sequences for white bass (Li et al., 2014; GenBank accession GAZY00000000), and 1,730 unigene sequences for white perch (Morone americana) (Schilling et al., 2014; GenBank accession GAQS00000000).
These resources collectively provide excellent tools for selective breeding, marker-assisted selection, and domestication, as well as for functional studies on the biology and aquaculture of striped bass. For example, the genome and transcriptome data empower proteomic analyses (Andersen et al., 2019; Reading et al., 2012, 2013; Schilling et al., 2014, 2015; Schilling, Loziuk, Muddiman, Daniels, & Reading, 2015; Williams, Reading, Amano, et al., 2014).
Future directions and challenges
Striped bass is an aquaculture species that is well-positioned for commercial production. The current extent of consumer visibility, established market size and product price-point, knowledge of the biology and culture, and infrastructure for commercial seed production and rearing of striped bass all support the likelihood of its success as an aquaculture industry.
Furthermore, the fish is euryhaline, which means it can be reared in fresh, brackish, or marine water in coastal and inland systems throughout the United States. Culture methods of striped bass are well established, and therefore, no major hurdles remain regarding the technology to produce the fish.
Recent efforts have established a reliable hatchery larval production system, which in the past has been considered a bottleneck to commercial-scale production (McCraren, 1984). One of the only limitations to developing a striped bass industry is the lack of current commercial U.S. producers and data to support the economic viability of commercial production.
Barriers and opportunities
Significant barriers remain primarily the full commercial-scale demonstration and detailed economics of production and marketing to show that striped bass aquaculture is solvent. Development and expansion of the striped bass aquaculture industry in the United States has great potential if the following conditions are addressed:
- 1. Identifying domestic producers for commercial production and providing adequate fish to consistently supply seafood markets;
- 2. Demonstrating profitability through production, marketing, processing, and economics;
- 3. Clarification and general reduction of regulatory permitting and licensing procedures; and
- 4. Promoting comprehensive extension education, technical training, marketing, and product visibility to consumers and stakeholders.
Establishing a conglomerate group of stakeholders and partners would enable a centralized demonstration of the technologies and outreach necessary to commercialize striped bass production. This would include demonstrating the culture of adequate volumes of fish for commercialization and marketing using diverse aquaculture systems (pond, cage, and RAS or combinations thereof), developing business models for demonstrating profitability, and establishing extension activities to disseminate this information.
Current finfish aquaculture infrastructure can provide support for producing and marketing striped bass at a commercial scale. Collaboration with social scientists and seafood distributors to better understand seafood marketing, consumer preferences, market depth, supply and demand, retail pricing, and the provision of additional outreach about striped bass aquaculture are also crucial (Pigg & Reading, 2018; Ryan et al., 2018).
Venture capital investment will be required for the next phase of industry development and upscaling once commercial striped bass production and marketing has been demonstrated. Additionally, engagement in extensive outreach, including extension programming and technology transfer, is required to provide the necessary aquaculture and marketing training tools to support the growth of this industry. This would include working with state NOAA Sea Grant programs along with the USDA and state cooperative extension agents at Land Grant Universities in the region to address social, behavioral, economic, and policy priorities associated with striped bass aquaculture.
“Clarity on policies relevant to commercial aquaculture (e.g., production, product transport) is also imperative to developing a striped bass aquaculture industry. Presidential Executive Order 13921, 2020 (“Promoting American Seafood Competitiveness and Economic Growth”) was issued in 2020 with the intent to: …improve the competitiveness of American industry; ensure food security; provide environmentally safe and sustainable seafood; support American workers; ensure coordinated, predictable, and transparent Federal actions; and remove unnecessary regulatory burdens.”
Among the specific actions outlined in order to achieve these goals is the renewal of a: …focus on long-term strategic planning to facilitate aquaculture projects, we can protect our aquatic environments; revitalize our Nation’s seafood industry; get more Americans back to work; and put healthy, safe food on our families’ tables. Several legislative hurdles hindering the development of the U.S. marine aquaculture industry are addressed by the executive order, such as requiring environmental reviews of aquaculture projects to be completed within 2 years.
Establishing the StriperHub
The StriperHub is a Sea Grant-supported network that was formed to facilitate striped bass aquaculture. The hub aims to overcome barriers to industry development and expansion by demonstrating and promoting commercial-level culture, economics, and marketing of U.S. striped bass. North Carolina Sea Grant is leading the initiative and coordinating the StriperHub network, which is made up of several Sea Grant programs, USDA and other federal scientists, industry partners, and university researchers focused on consolidating and streamlining commercialization efforts in various culture environments.
“Detailed analyses of economics and marketing, baseline farm gate value and market depth, estimations of production economics, and demonstration of the potential for commercial culture scaling necessary for adoption and growth of the commercial striped bass aquaculture industry are some of the priorities of the StriperHub. The StriperHub has been active since 2020 in organizing project meetings, developing a web presence, creating recipes, and conducting research. Activities to date have resulted in successful commercial aquaculture production, and the first farmed domestic striped bass will be available in U.S. markets in 2021.”
In addition to being identified as a candidate aquaculture species by the NOAA, establishing a commercial striped bass aquaculture industry relies on the continued efforts of stakeholders, scientists, legislators, policymakers, and their institutions in conducting research, performing assessments, developing business models, and marketing strategies, and adopting clear permitting and licensing procedures for producers and vendors. These goals will be best realized if all of these stakeholder groups are able to synergize in a coordinated effort to serve as a nexus for information that can be disseminated to commercial producers and the public through the additional avenues of communication, outreach, education, and extension created through the StriperHub.
*This is a summarized version developed by the editorial staff of Aquaculture Magazine of the original article “The status of striped bass, Morone saxatilis, as a commercially ready species for U.S. marine aquaculture” written by: Linnea K. Andersen, Jason Abernathy, David L. Berlinsky, Greg Bolton, Matthew M. Booker, Russell J. Borski, Travis Brown, David Cerino, Michael Ciaramella, Robert W. Clark, Michael O. Frinsko, S. Adam Fuller, Steve Gabel, Bartholomew W. Green, Eric Herbst, Ronald G. Hodson, Michael Hopper, Linas W. Kenter, Frank Lopez, Andrew S. McGinty, Barry Nash, Matthew Parker, Stacey Pigg, Steve Rawles, Kenneth Riley, Marc J. Turano, Carl D. Webster, Charles R. Weirich, Eugene Won, L. Curry Woods III, Benjamin J. Reading, StriperHub that was originally published through Wiley’s Journal of the World Aquaculture Society on May 2021.
The full version of this review can be accessed online at: DOI: 10.1111/jwas.12812