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Research Project: Enhancing the Production of Hybrid Striped Bass Through Improved Genetics, Nutrition, Production Management, and Fish Health

Location: Harry K. Dupree Stuttgart National Aquaculture Research Cntr

2021 Annual Report


Objectives
1. Improve the performance of hybrid striped bass (HSB) fingerlings in intensive production systems. 1.A. Develop fish stocking and dissolved oxygen and dissolved inorganic nitrogen management strategies for intensive production of HSB. 1.B. Optimize production of advanced HSB fingerlings in the biofloc technology production system. 1.C. Determine the nutritional value of alternative ingredients and supplemental exogenous enzymes for HSB. 1.D. Evaluate practical fishmeal-free (FMF) and plant-based diets for HSB performance and nutrient (N & P) retention in intensive production systems. 1.E. Determine optimum feeding regime, live feed enrichment, and feasibility of microparticulate diets to increase growth, survival, condition, and fatty acid composition in moronid larvae. 2. Reduce on-farm mortalities to pathogens in HSB aquaculture. 2A-D. Perform controlled challenges with white bass (WB), striped bass, palmetto and sunshine HSB to establish their susceptibility to emerging pathogens. Detect genetic variation for resistance to disease in host, and identify genes and pathways critical for pathogenesis in microbe; Evaluate the innate and adaptive immune response and determine the efficacy of vaccines to emerging pathogens. 2.E. Develop methods for harmful algal bloom control. 3. Develop and implement technologies that enhance genetic improvement of HSB. 3.A. Create and release a first-generation white bass genome and transcriptome assembly. 3.B. Optimize a photo thermal manipulation protocol for offseason (fall) spawning of WB and create even/odd year class base populations for selective improvement of important production traits. 3C. Identify phenotypic differences in WB for growth and utilization of plant protein- and plant oil-based diets and determine the genetic variation in protein, lipid and carbohydrate utilization for the identified traits. 3.D. Develop methods for the production of triploid HSB.


Approach
Develop fish stocking and dissolved oxygen and dissolved inorganic nitrogen management strategies for intensive production of hybrid striped bass utilizing both traditional and split-pond production systems; Optimize production of advanced hybrid striped bass fingerlings in biofloc technology production system; Determine the nutritional value of alternative ingredient mixes and supplemental exogenous enzymes for hybrid striped bass. Evaluate practical fishmeal-free and plant-based diets for hybrid striped bass performance and nutrient (Nitrogen and Phosphorus) retention in intensive production systems; Determine optimum feeding regime, live feed enrichment, and feasibility of microparticulate diets to increase growth, survival, condition, and fatty acid composition in moronid larvae; Determine optimum larval feeding regime for larval Morone using live feeds to increase growth, survival, and larval quality through metamorphosis; Determine the influence of live feed enrichment on growth, survival, condition, and fatty acid composition of Morone larvae; Determine the feasibility of replacing live feeds with formulated microparticulate diets from first feeding in moronid larvae; Perform controlled challenges with white bass, striped bass, palmetto and sunshine hybrid striped bass to establish their susceptibility to emerging pathogens; Detect genetic variation for resistance to disease in moronids. Identify microbial genes and pathways critical for pathogenesis in moronids; Evaluate the innate and adaptive immune response in moronids and determine the efficacy of vaccines to emerging pathogens; Develop methods for harmful algal bloom control; Create and release a first-generation white bass genome and transcriptome assembly; Optimize a photo thermal manipulation protocol for offseason (fall) spawning of white bass and create even/odd year class base populations for selective improvement of important production traits; Identify phenotypic differences in white bass for growth and utilization of plant protein- and plant oil-based diets and determine the genetic variation in protein, lipid and carbohydrate utilization for the identified traits; Develop methods for the production of triploid hybrid striped bass.


Progress Report
Research is ongoing to determine the feasibility of early weaning of hybrid striped bass (HSB) larvae onto manufactured microdiets (MDs). ARS researchers in Stuttgart, Arkansas, have been seeking to determine the earliest time that HSB larvae can be converted to a manufactured MD. Additional studies were completed this year comparing the growth and survival of white bass and hybrid striped bass larvae fed one of six MDs or a traditional live feed for either 19 or 36 days. These studies have also been a combination of traditional weaning as well as MD/live feed cofeeding studies to determine if there is a growth and/or survival benefit to this strategy with any of these unique formulations. Data analysis is ongoing to determine the MD that best maximizes larval growth and survival as compared to a typical live feed regimen. Research ongoing to determine feasibility of using food-grade clam juice as a larval MD feed palatant. ARS researcher at SNARC have been seeking to determine the feasibility of converting HSB larvae to a manufactured MD. The goal of this study was to determine if the addition of a feed palatant would increase the intake and therefore improve growth and/or survival of HSB larvae. Working with a food manufacturer, the palatant chosen was a novel mixture of diluted clam juice added to a Otohime commercial MD, one of the main MDs currently fed to multiple commercial larval species around the globe. Data analysis is ongoing to determine the impact of the addition of the novel palatant had on growth and survival. An intensive study was initiated to compare production for the first time of market-size hybrid striped bass in conventional earthen ponds to that in earthen ponds modified to the split-pond configuration. In the split-pond production system, a traditional earthen pond is divided (split) into a fish basin (15-20% of pond area) and a waste treatment lagoon (80-85% of pond area). Improved management of dissolved oxygen concentration in the fish basin and ammonia detoxification in the waste treatment lagoon produces catfish yields two to four times above that from traditional earthen ponds. Similar results are expected when hybrid striped bass are grown in the split-pond production system. Because of the delays in marketing and potential new market opportunities for fish larger than 1.5 lb, farmers now are concerned that as fish exceed this size their fat content will become excessive and possibly cause consumer dissatisfaction. Continued lean growth of larger fish should be possible by using a finishing diet that contains less protein and fat than the high protein-high fat grow-out diets. Besides evaluating intensified production systems, an additional treatment was included to evaluate a nutritionally complete finishing diet for HSB grow-out in traditional earthen ponds. Our collaboration with researchers from the University of Arkansas at Pine Bluff (UAPB), Pine Bluff, Arkansas and Keo Fish Farm, Keo, Arkansas, to produce sterile or triploid (3n) sunshine hybrid striped bass has continued. When producing triploid fish, the first obstacle was that the use of tannic acid by the industry (first 4 minutes of incubation) also coincided with the time the literature states that hydrostatic pressure needs to be applied (also 4 minutes) to prevent the second polar body release from the fertilized egg; preventing this release is essential to create triploid fish. The use of evaporated or whole milk has removed this obstacle and allowed us to proceed with the next phase of our research which is using pressure to make triploid fish. Attempts to create both triploid hybrid striped bass and tetraploid parental species are ongoing. Our collaboration with researchers at the Freshwater Institute (Shepherdstown, West Virginia) and Hood College (Frederick, Maryland) on the toxicity of peracetic acid to early life stages of Atlantic salmon has continued. This research is also investigating the use of peracetic acid in recirculating aquaculture systems to treat these systems to eliminate pathogens. Our collaboration with researchers in Denmark, Germany, Norway and the United States to establish the importance of peracetic acid as a disinfectant to the global aquaculture industry has continued. In the U.S., our research has the attention of the major manufacturer of peracetic acid (PeroxyChem) and another company that retails fishery products (AquaTactics); these companies have obtained U.S. Environmental Protection Agency (EPA) Registrations for use of their products in the aquaculture industry as a disinfectant and are considering other implications of its use. Collaborated by email and video conferences with a group of research scientists on the Aquatic Pathogen chapter for the joint USDA ARS-APHIS (Animal and Plant Health Inspection Service) Agriculture Biocontainment Compendium. Subsets of the white bass (WB) families created in crosses produced in Subobjective 3.A were raised in a common garden approach and fed a fish meal control or all-plant protein diet to examine Genotype x Environment effects. The two diets consisted of a control diet formulated to resemble an HSB commercial diet containing a mix of animal and plant protein sources, with 20-25% fish meal, and an all-plant protein diet formulated to replace animal protein in the control diet with plant proteins on an ideal protein basis. Diets were fed for 20 weeks to apparent satiation at least once daily, 6 days/week. At the end of the feeding trial, a subset of fish per cross per diet of the top and bottom performing crosses were arbitrarily selected for whole body composition and blood collection for gene expression analysis (RNA sequencing) based on the high-quality WB genome and transcriptome generated in Subobjective 3.A. Lab analyses are pending removal of ARS Pandemic occupancy restrictions and increased personnel availability. In efforts to minimize antibiotic use, alternatives to antibiotics (ATA) have been examined across animal agriculture, including aquaculture. Two promising feed additive classes are organic acids (e.g., sodium butyrate, sodium diformate) and phytogenic compounds from herbs and spices known as essential oils ( e.g., carvacol, thymol, alicin, cinnamaldehyde). The mode of action of these differing additives are not fully described but have shown varied success as antimicrobial agents based on bacterial type. ARS researchers at SNARC, Stuttgart, Arkansas and Small Grains and Potato Germplasm Research Center, Hageman, Idaho along with collaborators at the Bozeman Fish Technology Center, Bozeman, Montana performed feeding trials with hybrid striped bass and rainbow trout to test the efficacy of these feed additives separately and in combination on fish performance and health. The additives were tested to combat Streptococcus infection in hybrid striped bass and cold-water disease in rainbow trout. Preliminary results indicate both organic acids and essential oils improve growth rates and feed efficiency in rainbow trout and hybrid striped bass compared to fish consuming the control diet. The disease challenge, gene regulation, and hybrid striped bass taste panel portions of the trials are still pending. ARS researchers have determined that WB and striped bass (SB), the parental species to HSB, display large differences in susceptibility to the bacterium Flavobacterium columnare. We created F2 backcross hybrid striped bass by mating F1 hybrid striped bass with parental white bass to be used as a mapping population for disease resistance Quantitative Trait Loci (QTL) studies. Disease challenges on segregating families and sampling has been performed and building of a high-density Moronid single nucleotide polymorphism (SNP) array is underway. This research will aid in the development of disease-resistance genetic markers. ARS researchers continue to breed WB (Morone chrysops) families to provide stocks to stakeholders through Cooperative Agreements as well as to selectively improve growth traits when fed a plant-based diet. WB (M. chrysops) is a parental species of HSB (M. chrysops x M. saxatilis). A chief constraint to the expansion of HSB production arises from the use of wild-catch parents in breeding programs. This is costly, unsustainable and leads to uncontrolled variation in the offspring. A goal of our broodstock development program is to advance progress in the genetic improvement of hybrids by building white bass resources to facilitate selective breeding for agriculturally important traits and ultimately provide germplasm to stakeholders. ARS researchers continue to examine the differential susceptibilities of among WB, SB, and HSB to emerging pathogens. Gene expression differences in mucosal tissues among WB, SB, and their hybrids are currently being examined by RNA sequencing of gill, skin, and intestines after bacterial challenge at various times post infection.


Accomplishments
1. High-quality genome sequence of white bass. ARS researchers in Stuttgart, Arkansas, in collaboration with scientists at North Carolina State University mapped and annotated a high-quality genome sequence of the white bass (Morone chrysops) for release to the public through the National Center for Biotechnology information (NCBI). The white bass is a parental species of hybrid striped bass, a fish of increasing commercial importance throughout the U.S. Our goal was to advance progress in the genetic improvement of hybrids by building white bass resources to facilitate selective breeding for agriculturally important traits. Toward this goal, we created a white bass genome assembly, which was accomplished using high-throughput Illumina DNA sequencing combined with Chicago® and Dovetail™ Hi-C + HiRise™ scaffolding. First, available white bass short-read DNA sequences generated from a single female individual on an Illumina GAIIx platform were assembled into 57,533 contigs to build a preliminary genome sequence. Next, DNA from the same female individual was re-sequenced and scaffolded from the initial genome assembly via the Chicago and Dovetail Hi-C + HiRise scaffolding pipeline. This approach produced a 645.14 Mb genome assembly. The largest 24 scaffolds, indicative of the haploid number of chromosomes (n=24) for white bass, ranged in size from 15.4 Mb to 32.2 Mb. The final scaffold N50 was improved from 161 kb to 28.018 Mb and the final scaffold N90 was improved from 24 kb to 21.862 Mb over our initial assembly. Data is available at the NCBI under the accession number JAGRRF00000000.

2. Determined disease resistance of white bass, striped bass, and hybrid striped bass to Flavobacterium columnare and the role of moronid mucus on bacterial biofilm formation. ARS researchers in Stuttgart, Arkansas, in collaboration with ARS researchers at the Aquatic Animal Health Research Unit in Auburn, Alabama, determined the survival rate of white bass, striped bass, and hybrid striped bass to Flavobacterium columnare and the role of moronid mucus on bacterial biofilm formation. Columnaris disease generates substantial losses of many freshwater fish species, including hybrid striped bass. ARS researchers sought to determine the susceptibility of white bass, striped bass, and hybrid striped bass to infection by F. columnare and investigate the effects of moronid mucus on total bacterial growth and biofilm formation. We found that white bass are more resistant to F. columnare than hybrid striped bass and that striped bass were the most susceptible of the three. Species and concentration-dependent differences were detected in the total growth of the bacteria to host mucus. Moronid mucus can significantly affect biofilm formation when exposed to F. columnare, and that there is a correlation between the bacteria's response of growth and biofilm formation with bass species’ susceptibility. Results also suggest a component of this disease resistance is contained in the fish mucus and that recovery and survival after F. columnare infection may be associated with the presence of mucosal antimicrobial effectors.

3. Report on the status of striped bass as a commercially ready species for U.S. marine aquaculture. ARS researchers in Stuttgart, Arkansas, in collaboration with the StriperHUB consortium, combined research efforts and expertise to publish a consensus report on the current status of striped bass (Morone saxatilis) as an aquaculture species for U.S. farmers. Striped bass have long been regarded as one of the most important recreational fisheries in the United States. Decades of research have been conducted on striped bass and its hybrid (striped bass x white bass M. chrysops). Culture methods have been established, in particular for the hybrid striped bass, which is the fourth largest finfish aquaculture industry in the nation ($50 million USD). Additionally, domestic striped bass have been bred since the 1990’s and are available for commercial fry production. In this report, we detail the current status of striped bass aquaculture in the United States, including genetic, nutrition, and production parameters, along with economic opportunities for breeders and producers.

4. Sticky fish eggs thwarted by common baking ingredient. Hybrid striped bass larvae are produced by strip-spawning, and fertilized eggs become extremely sticky and clump together which limits the amount of oxygen that can reach them and can cause fungal problems. Both issues can destroy an entire batch of eggs. The hybrid striped bass industry typically uses tannic acid treatments to prevent adhesion of eggs, but it is costly and, if left too long, will form a hard layer on the surface of the fertilized eggs which can prevent embryos from hatching. ARS researchers in Stuttgart, Arkansas, investigated 12 candidate compounds to prevent stickiness and found that 10% whole milk treatment performed best. To further this research, evaporated milk was explored as an egg de-adhesive as an easier option for remote hatcheries because of the much longer shelf-life as opposed to fresh whole milk. After seeing the success of these experiments and ease of using evaporated and whole milk, the largest commercial hybrid striped bass hatchery decided to start using them immediately for the remainder of their 2020 hybrid striped bass production; in 2021, the hatchery exclusively used the milks to prevent clumping and successfully produced 80.9 million larvae using these methods.

5. Iron acquisition systems in virulent Aeromonas hydrophila identified as potential target for new therapeutants. ARS researchers in Stuttgart, Arkansas, in collaboration with ARS researchers in Auburn, Alabama, and researchers at Auburn University, characterized additional virulence pathways of the fish pathogen Aeromonas hydrophila. This Gram-negative bacterium has been responsible for extensive losses in the aquaculture industry, including catfish, for over a decade. Due to its significance and impact on the aquaculture industry continuing efforts to better understand the basic mechanisms that contribute to virulent A. hydrophila (vAh) outbreaks are urgently needed. Recent challenge models demonstrated that vAh cultured in the presence of the iron chelating agent deferoxamine mesylate (DFO), were more virulent to channel catfish (Ictalurus punctatus). Using a global proteome analyses combined with a custom computational pipeline, researchers identified upregulated proteins among the DFO treatment that were enriched for gene ontology groups including iron ion transport, siderophore transport and siderophore uptake transport - all iron acquisition pathways. Protein-protein interactions were also evaluated among the differentially expressed proteins and predicted that many of the upregulated iron acquisition proteins likely form functional physiological networks. Our findings revealed additional virulence factors which can be explored as potential targets for new therapeutants including vaccines.

6. Use of an immersion adjuvant with a recombinant protein vaccine in channel catfish enhances protection against Flavobacterium Columnare. The Gram-negative bacterium Flavobacterium columnare, the causative agent of columnaris disease, generates substantial mortality during the production of freshwater fish species, including catfish. Vaccination remains a practical alternative that has proven to be effective in the control of different pathogens in the catfish industry. ARS researchers in Stuttgart, Arkansas, in collaboration with ARS researchers in Auburn, Alabama, evaluated the efficacy of a recombinant F. columnare DnaK vaccine using different immersion adjuvant strategies. Our studies found that timing of vaccine with adjuvant treatment by bath immersion significantly impacts survival rate after exposure to F. columnare. Eight weeks post vaccination, catfish challenged with F. columnare had a significantly higher survival rate (P <0.05) among the 5- and 30-min bath immersion rDnaK + adjuvant vaccine groups when compared to the non-vaccinated and adjuvant only control groups. There was also a significant difference in survival between the rDnaK + adjuvant groups (P <0.05). The overall survival rates of the vaccine groups were 37% (5 min) and 17% (30 min) after 5 days of observation, while non-vaccinated and adjuvant only controls had 0% survival after 2.5 days. These results will assist in improving the production and protocols of usage for vaccinations against columnaris disease.

7. Determined optimum hybrid striped bass larval feeding regimes using live feeds at two rearing temperatures. ARS researchers in Stuttgart, Arkansas, have been seeking to determine the earliest time that Morone larvae can be converted to a prepared diet by minimizing the time spent on live food items while maximizing larval growth and survival by rearing larvae in recirculating aquaculture systems at two temperatures (18 deg C and 26 deg C). Importantly, less infrastructure and expertise is needed to grow and feed Artemia as compared to rotifers and Artemia are less prone to catastrophic losses due to environmental conditions. Therefore, the goals of this study were to determine the earliest time HSB larvae could be weaned off of rotifers and onto Artemia nauplii at an optimum (26 deg C) and suboptimum (18 deg C) culture temperature and compare total length and survival of the resulting larvae (2 - 8 days in two day intervals). There was no difference in survival in HSB larvae based on how many days they were fed rotifers at either 18 deg C or 26 deg C. However, there was a difference in larval survival between the two rearing temperatures. At the end of the study, larvae from the 18 deg C system were 17% shorter (8.00 mm) than those reared in the 26 deg C system (9.59 mm), and total length and body depth of larvae varied significantly (P<0.0001) among treatments by temperature and the number of days they were fed rotifers. These results demonstrate that minimizing time larvae were fed rotifers maximized growth. This study also showed that Artemia is a suitable diet for six-day-old larval HSB and that these larvae can easily be weaned from rotifers at both optimum (26 deg C) and sub-optimum culture temperature (18 deg C) while maintaining suitable growth and with no significant drop in survival. This will allow tank producers of hybrid striped bass to alter rearing practices to incorporate fewer days of required rotifers which will reduce costs associated with tank production of Moronid larvae.

8. Determined the optimum larval feeding regime to maximize white bass larval growth. ARS researchers in Stuttgart, Arkansas, have been seeking to determine the earliest time that several species of Morone larvae can be converted to a prepared diet by minimizing the time spent on live food items while maximizing larval growth and survival by rearing larvae in recirculating aquaculture systems. White bass (WB) Morone chrysops is one of the parental species of the hybrid striped bass (HSB) which represents a valuable sector of the U.S. aquaculture industry. One factor limiting the growth of the HSB industry is the lack of methods to rear larvae in tanks with minimal time spent on live feeds, maximizing growth and survival, including methods targeting the parental species. The goal of this study was to determine the minimum amount of time WB larvae could be fed live feeds (Artemia) and weaned onto a commercial diet that will maximize growth (eight to 28-days in 4-day increments). At the end of the study, mean length of larvae ranged from 10.91 - 19.12 mm and averaged 14.49 +/- 3.46 mm across all treatments; mean body depth of larvae ranged from 1.86 - 3.40 mm and averaged 2.42 +/- 0.69 mm. Total length and body depth of larvae varied significantly based on the number of days fed Artemia (P<0.0001), with both traits significantly increasing with the number of days fed Artemia. The present study demonstrates that maximizing the time WB larvae are fed Artemia before the addition of dry commercial diet results in significantly larger larvae at the conclusion of the larval feeding period. Further refinements of microdiets and feeding strategies with WB larvae could help shorten this requirement. This research is currently ongoing.


Review Publications
Farmer, B.D., Fuller, S.A., Beck, B.H., Abernathy, J.W., Lange, M.D., Webster, C.D. 2020. Differential susceptibility of white bass (Morone chrysops), striped bass (Morone saxatilis) and hybrid striped bass (M. chrysops x M. saxatilis) to Flavobacterium columnare and effects of mucus on bacterial growth and bio. Journal of Fish Diseases. 44(2):161-169. https://doi.org/10.1111/jfd.13272.
Green, B.W., Schrader, K.K., Rawles, S.D., Webster, C.D., McEntire, M.E. 2019. Comparison of unused water and year-old used water for production of channel catfish in the biofloc technology system. Aquaculture. https://doi.org/10.1016/j.aquaculture.2019.734739.
Webster, C.D., Rawles, S.D., Kelly, A.M., Roy, L.A., Rosentrater, K. 2021. Juvenile bluegill (Lepomis macrochirus) can be fed diets without marine fish meal without adverse effects on growth, survival, diet utilization, and body composition. Aquaculture Nutrition. 27(4):1144-1159. https://doi.org/10.1111/anu.13255.
Roy, L., Rawles, S.D., Kelly, A., Stone, N., Park, J., Webster, C.D. 2019. The effects of different winter feeding regimens on growth, survival, and fatty acid composition of fathead minnow and golden shiners. North American Journal of Aquaculture. 81:189-200. https://doi.org/10.1002/naaq.10086.
Green, B.W., Rawles, S.D., Schrader, K., Mcentire, M.E., Abernathy, J.W., Ray, C.L., Gaylord, T.G., Lange, M.D., Webster, C.D. 2021. Impact of dietary phytase on tilapia performance and biofloc water quality. Aquaculture. 541:1-11. https://doi.org/10.1016/j.aquaculture.2021.736845.
Andersen, L., Abernathy, J.W., Berlinsky, D., Bolton, G., Booker, M., Borski, R., Brown, T., Cerino, D., Ciaramella, M., Clark, R., Frinsko, M.O., Fuller, S.A., Gabel, S., Green, B.W., Herbst, E., Hodson, R.G., Hopper, M., Kenter, L.W., Lopez, F., Mcginty, A.S., Nash, B., Parker, M., Pigg, S., Rawles, S.D., Riley, K., Turano, M.J., Webster, C.D., Weirich, C., Won, E., Woods, L., Reading, B.J. 2021. The status of striped bass Morone saxatilis as a commercially ready species for U.S. marine aquaculture. Journal of the World Aquaculture Society. 52(3):1-21. https://doi.org/10.1111/jwas.12812.
Bockus, A.B., Rawles, S.D., Sealey, W.M., Conley, Z.B., Gaylord, T. 2021. Effect of dietary additives Thermal Care™, Bio-Mos®, and GroBiotic® A on rainbow trout (Oncorhynchus mykiss) performance at elevated temperature. Aquaculture. 544. https://doi.org/10.1016/j.aquaculture.2021.737084.
Good, C., Davidson, J., Straus, D.L., Harper, S.B., Marancik, D., Welch, T.J., Peterson, B.C., Pedersen, L., Lepine, C., Redman, N., Meinelt, T., Liu, D., Summerfelt, S. 2020. Assessing peracetic acid for controlling post-vaccination Saprolegnia spp.-associated mortality in juvenile Atlantic salmon Salmo salar in freshwater recirculation aquaculture systems. Aquaculture Research. 00:1-4. https://doi.org/10.1111/are.14567.
Lange, M.D., Abernathy, J.W., Shoemaker, C.A., Zhang, D., Kirby, A., Peatman, E., Beck, B.H. 2020. Proteome analysis of virulent Aeromonas hydrophila reveals the upregulation of iron acquisition systems in the presence of a xenosiderophore. FEMS Microbiology Letters. 367(20):1-8. https://doi.org/10.1093/femsle/fnaa169.
Fuller, S.A. 2020. Minimizing time fed rotifers maximizes hybrid striped bass larval growth in recirculating aquaculture systems. North American Journal of Aquaculture. 80:208-214. https://doi.org/10.1002/naaq.10146.
Zhao, H., Beck, B.H., Fuller, S.A., Peatman, E. 2020. EasyParallel: a GUI platform for parallelization of STRUCTURE and NEWHYBRIDS analyses. PLoS One. 15(4):e0232110. https://doi.org/10.1371/journal.pone.0232110.