Location: Harry K. Dupree Stuttgart National Aquaculture Research Cntr
2020 Annual Report
Objectives
Objective 1: Develop novel ingredients and formulate diets for warmwater finfish. Novel ingredients and new formulations will target reduced reliance on fishmeal in the diets, enhanced nutrient delivery (e.g., better amino acid availability), and reduced anti-nutritional factors.
Sub-objective 1A: Develop and validate practical all-plant protein diets for hybrid striped bass (HSB) and white bass (WB).
Sub-objective 1B: Determine optimal inclusion level of distiller’s dried grains with solubles and high-protein distillers dried grains with solubles in diets for Nile tilapia.
Sub-objective 1C: Determine optimal inclusion level of cottonseed meal and poultry by-product meal in diets for largemouth bass.
Objective 2: Obtain and test white bass broodfish from multiple populations for improved production of hybrid striped bass. Key phenotypic traits will be defined and a white bass broodstock will be established.
Sub-objective 2A: Obtain and produce white bass from multiple geographically distinct populations.
Sub-objective 2B: Conduct white bass strain performance evaluation and selection.
Sub-objective 2C: Hybrid striped bass performance evaluation.
Objective 3: Compare and optimize production of hybrid striped bass in biofloc technology and pond production systems.
Sub-objective 3A: Define stocking rate/initial biomass – yield relationship for HSB in a biofloc technology system.
Sub-objective 3B: Compare production of HSB in biofloc technology and pond production systems.
Approach
Identify promising feed palatants that enhance all plant protein (APP) diet feed intake; identify plant proteins for use in APP test diets; formulate a series of marine fish meal (FM) replacement diets using ideal protein theory, plant protein blends, and feed additives designed to ameliorate ingredient deficiencies; characterize growth performance, nutrient retention, gut microflora, and metabolic gene expression in response to FM replacement diet; and validate promising APP diets in a pond production trial. Feeding studies will evaluate the effect of partial or total replacement of FM by either Distiller’s dried grains with solubles or high protein Distiller’s dried grains with solubles in the diet of Nile tilapia on feed intake, growth, feed conversion, and histology of the intestine. A feeding study will evaluate the effect of substitution of FM by various ratios of poultry by-product meal and cottonseed meal in practical diets for juvenile largemouth bass on growth performance, health status, and body composition. Adult white bass (WB) will be acquired from three distinct regions of the species’ native range (Arkansas River, AR, Central and South TX, and Upper Tennessee River, TN), spawned and the genetic diversity and production performance of multiple strains and families will be compared in tanks and ponds to our domesticated WB broodfish population in order to select superior performing families to use in developing improved synthetic lines. Evaluate production performance of families of hybrid striped bass (HSB) made from the WB improved synthetic lines. Quantify the relationship between the HSB stocking rate/initial biomass – yield relationship to produce advanced fingerlings in the biofloc technology production system and compare to traditional pond production method.
Progress Report
This project was replaced by new project #6028-31640-009-00D, "Enhancing the Production of Hybrid Striped Bass Through Improved Genetics, Nutrition, Production Management, and Fish Health."
Tremendous progress was achieved for all project objectives during this five-year period. Fishmeal is the primary source of dietary protein in commercial diets formulated for carnivorous fish like hybrid striped bass and white bass and a secondary source of dietary protein for other warmwater fish like tilapia and bluegill, but because fishmeal is a finite global resource its use in fish production diets is not sustainable. Soybean meal is a common plant protein used in formulating animal, including warmwater fish, diets but how much can be included in the diet may be limited by how well the fish tolerates the anti-nutritional factors found in soybean meal. Anti-nutritional factors are compounds found in many plant ingredients that can cause intestinal health issues and reduce digestion and absorption of nutrients from feed. Soy-naïve hybrid striped bass were fed test diets in which fish meal was replaced by six different soy products, including three non-genetically modified soybean meals that were bred for high protein content and potentially lower anti-nutritional factors. Results of feeding trials indicate that fishmeal can be replaced totally by a variety of soy derived products when formulated on an available amino acid basis and supplemented with limiting amino acids, with no apparent adverse effects on fish production, and suggest that hybrid striped bass are not as sensitive as some fish to soy-derived antigens found in traditional soy varieties.
As the plant-based content of fish diets increases hybrid striped bass find the feed increasingly unpalatable and grow less because feed consumption drops. Consumption of an all-plant protein diets supplemented with one or more flavor attractants, also called palatants, was compared to an all-plant protein diet without attractants and a commercial, fishmeal-based diet consumed readily by hybrid striped bass. Several palatants caused juvenile hybrid striped bass to consume as much feed as fish fed the commercially formulated diet.
When animal protein, which is typically high in the amino acid taurine, is removed completely from fish diets, growth performance of some fish species suffers, likely because of a deficiency in this conditionally essential amino acid. Although ARS researchers found no evidence that hybrid striped bass require taurine when fed all-plant protein diets, muscle saturation and liver data suggest that body stores are maximized when taurine is included at 1% of the diet.
Fish feed typically is supplemented with inorganic phosphorus to ensure adequate dietary phosphorus availability, especially in diets that contain high percentages of plant feedstuffs where phosphorus is present as phytate and is not bio-available to fish because their digestive system lacks enough phytase enzyme. Consequently, unmetabolized phytate is excreted and contribute to eutrophication of the culture environment. ARS researchers conducted studies in earthen ponds, cages in earthen ponds, and biofloc production system tanks to evaluate whether treating formulated diets for hybrid striped bass or tilapia with phytase would eliminate the need to supplement diets with inorganic phosphorus and whether phytase-treated diets impact negatively channel catfish performance and physiology. Data analyses are ongoing.
As the culmination of our research to optimize fish meal replacement in formulated diets for hybrid striped bass. ARS researchers conducted an pond trial using a typical industry pond management protocol validated diets that gave promising results in tank trials. Production of market-sized hybrid striped bass was evaluated for fish fed an all-plant protein diet, fish meal-free diet, a fish meal control diet, or a commercial feed. Sample and data analyses are ongoing.
Genetic markers that were developed through genotype-by-sequencing allowed differentiation of wild stocks collected from waterways in Alabama, Arkansas, North Carolina, and Texas from the only existing domestic stock and demonstrated enough genetic diversity to create a new white bass line. Even and odd year-class base populations were established by crossing males and females from each population with males and females from all other populations.
White bass naturally reproduce in the springtime, with the help of natural cues including daylight and temperature. ARS researchers developed and implemented a protocol to spawn white bass in the fall (off season) that will allow us to evaluate additional performance traits such as disease resistance and tolerance to fish meal-free diets.
In an on-going common-garden trial, a subset of juveniles from 15 families from the odd (2019) year-class of white bass families are being fed a fish meal control or an all-plant protein diet. The families used represent a portion of the crosses derived from each of the wild and domestic strains of white bass currently being used to develop a new line of white bass by single-pair mating of wild caught and domestic fish. Results of this study will determine whether white bass can be selected for better performance traits on an all-plant protein diet.
ARS researchers continue to progress toward a better understanding of the currently uncharacterized moronid sex-determination system and are developing sex markers because most producers are interested in female-heavy breeding stocks. As the sex determining system in seabass in polygenic, we continue to examine whether thermal protocols can influence sex ratios in moronids. A total of 150 male and 150 female white bass genomes were re-sequenced and genetic mapping between the populations is underway. Long-read sequencing for haplotype mapping and testing of discriminant markers is an ongoing effort.
A backcross HSB line was created by breeding hybrid striped bass males with white bass females. Because parental white bass and striped bass species display extremes in important production traits, these backcross families are being utilized in genome-wide association studies.
ARS researchers are investigating the use of hybrid striped bass in expression quantitative trait loci (eQTL) studies. F1 hybrid striped bass from reciprocal matings of wild and domestic white bass and striped bass were created. A total of 36 fish (original and reciprocal matings) transcriptomes were sequenced and signatures of domestication are currently being analyzed to distinguish parent-of-origin bias from lineage-of-origin (potential eQTLs for domestication) bias.
ARS researchers continued collaboration with North Carolina State University, Raleigh, North Carolina, researchers to assemble and improve the white bass and striped bass genome sequences using a combination of short-read and long-read sequencing technologies.
The biofloc technology production system is an innovative, non-traditional production system that extends the gains achieved in static-water pond yields by adoption of increased aeration capacity and use of split-ponds and was the focus of Objective 3, Compare and optimize production of hybrid striped bass in biofloc technology and pond production systems. Farmers in the U.S. have adopted the direct-stock production method for hybrid striped bass that relies on stocking a 0.5-1.5-ounce advanced fingerling for which production practices have not been optimized. ARS researchers were the first to demonstrate that hybrid striped bass can be grown successfully in the biofloc production system. In producing advanced fingerlings, a certain percentage of the hybrid striped bass fingerling population gains an early growth advantage and becomes cannibalistic towards conspecifics. ARS researchers in Stuttgart, Arkansas, found that cannibalistic fish decreased linearly from 33% to 6% of the population as stocking rate increased. Further refinements to optimize stocking rate are ongoing.
Food-size tilapia have been grown successfully in biofloc production systems that were stocked with advanced (2.5-7.0 ounce) fingerlings but using this system had not been used to produce these advanced fingerlings. Hatchery-reared tilapia weigh about 0.2 ounces when purchased by U.S. farmers, who must rear them efficiently to food fish size. Stocking these small fingerlings into food fish production units is practiced by many farmers but is inefficient. The stocking rate – advanced fingerling production function quantified by ARS researchers, allows producers to customize management protocols to produce efficiently advanced fingerlings to meet production goals.
Tilapia grown in the biofloc production system can derive some nutrition by consuming the biofloc, which led some to advocate reducing formulated ration dietary protein content. ARS researchers used ideal protein theory to formulate diets supplemented with the first four limiting amino acids and found that apparent grazing of biofloc by tilapia appeared to allow diet digestible protein to be reduced to 27.7% from 32.3% with no adverse effects on fish production. However, grazing the biofloc did not compensate for further reducing diet DP to 22.5%, which decreased tilapia production significantly and shifted fish to smaller size classes.
Accomplishments
1. Diet development for emerging food fish species. Bluegill, and their hybrids, used to only be grown to supply the sportfish industry. Today, however, they are emerging as a popular food fish in the southern U.S., as well as globally. But lack of economical, nutritious diet formulations and winter mortality are widely recognized as major factors that decrease profitability for producers. A uniform strategy for minimizing winter weight loss, reducing winter mortality, and optimizing intensive production-oriented diets that contain sustainable alternative protein ingredients to marine fish meal are high priorities for this industry. Diet composition, as well as feeding strategy, can affect the nutrition and disease resistance of fish. Deficiency of essential fatty acids (EFAs), for example, can result in growth reduction, abnormal physiological stress during cold temperatures, and suppressed immune function. However, the effects of dietary EFAs, protein sources, and feeding strategy on growth performance and winter survivability is unknown. A series of cooperative studies between ARS researchers in Stuttgart, Arkansas, and the University of Arkansas at Pine Bluff Agricultural Extension Service determined that: 1) feeding frequency impacted final fish weight at the end of simulated winter culture periods for some centrarchid species, but not all; 2) bluegill and hybrid bluegill exhibited preferential sequestering of long chain polyunsaturated fatty acids (the "n-3 heart healthy fatty acids") and utilization of monounsaturated fatty acids for energy during winter water temperatures, regardless of feeding frequency; and 3) centrarchids were able to effectively utilize a variety of alternative protein ingredients in place of marine fish meal; however, more work is needed to develop effective all-plant protein diets. These findings were rapidly adopted in the industry and have changed both the feeding practices and philosophy of diet formulation for both centrarchid sportfish and food-fish producers.
2. Population genetics analyses of domestic and wild white bass (Morone chrysops) and the creation of a new line for selective breeding. White bass is one of the parental species of hybrid striped bass, a major U.S. aquaculture species. Numerous state, federal, and private hatcheries rear these species for stocking as well as food fish. Genetic markers are critical for evaluating population diversity, detecting inbreeding, differentiating unknown individuals by population origin, and, ultimately, selecting for performance traits. ARS researchers in Stuttgart, Arkansas, captured wild white bass along waterways in the states of Arkansas, Alabama and Texas and collected a domesticated strain from North Carolina State University. In collaboration with scientists from Auburn University, genetic markers that could differentiate wild stocks from the only existing domestic stock of white bass were developed. ARS researchers then utilized this information to determine enough genetic diversity was present to create a new line of white bass by single-pair mating wild caught and domestic fish. As white bass reach sexual maturity in approximately 1.5 years, both an even and odd year class of white bass were created. A total of 98 full-sib families were spawned both years for broodstock development and selective breeding.
3. Off-season spawning of white bass (Morone chrysops). White bass naturally reproduce in the springtime, with the help of natural cues including daylight and temperature. ARS researchers in Stuttgart, Arkansas, have developed and implemented a method to further spawn white bass in the offseason (fall) in an effort to evaluate additional performance traits, including disease-resistance and tolerance to diet reformulations, and to provide for a year-round supply of fingerlings to industry. Both even and odd year-class have been successfully spawned utilizing protocols developed by ARS researchers. Methods are being implemented and amended to continue to improve reproductive success for subsequence generations. This increase in supply of white bass stocks are alleviating the need for wild caught fish in hybrid striped bass hatchery operations.
Review Publications
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.
Ramena, Y., Rawles, S.D., Lochmann, R., Gaylord, T.G., Mcentire, M.E., Farmer, B.D., Baumgartner, W., Webster, C.D., Beck, B.H., Green, B.W., Barnett, L.M. 2020. Growth, nutrient retention, innate immune response, and intestinal morphology of juvenile, soy-naïve hybrid striped bass, Morone saxatilis x M. chrysops, fed commercial-type, soy-based, fish meal replacement diets. Aquaculture. https://doi.org/10.1016/j.aquaculture.2020.735150.
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.
