Early growth and survival of striped bass, Morone saxatilis (Walbaum), and its phenotypically similar hybrid (M. saxatilis × M. chrysops) using an otolith marking method

An experiment using differently marked larval striped bass, Morone saxatilis (Walbaum). and its hybrid (M. saxatilis x M. chrysops (Rafinesque)) was performed in two grow-out ponds. Larval striped bass were immersed in oxytetracycline solution to mark their otoliths; hybrids received no treatment. Larvae from both groups were mixed and stocked at 8 days post hatch into the ponds. Striped bass and hybrid larvae grew to a significantly larger size at 35 days in one pond. In both ponds, hybrid lengths at 35 days after hatch were significantly greater than striped bass lengths. However, the magnitude of the size difference between hybrids and striped bass was twofold greater (10%) in one pond than in the other (5%). The proportion of striped bass juveniles at 35 days differed from the initial stocking proportion (0.53) only in one pond, where hybrids showed 12% greater survival than striped bass. Results suggested that the relative survival of hybrids was influenced by growth conditions in the ponds. Based on the ease of protocol and analysis of the marking experiment, we recommend its use to (1) investigate relative performance between genetic groups of young fish in common environments; and (2) predict the effects of introductions of genetically altered fishes.     

A MATHEMATICAL PROGRAMMING MODEL OF YEAR-ROUND HYBRID STRIPED BASS (♀MORONE CHRYSOPS x ♂MORONE SAXATILIS) FINGERLING PRODUCTION

Year-round production of hybrid striped bass fingerlings has been limited by low survival in ponds during late summer. A whole-farm model was developed to assess economic effects of incorporating indoor tank production and mobile nursery systems to extend the fingerling production season. Mixed-integer linear programming models were constructed for six production scales with three sizes of ponds and indoor tanks and with a mobile fish nursery system. Optimal allocation of production activities was sensitive to varying survival rates of fingerlings and monthly sales patterns. Breakeven prices in winter production of hybrid striped bass fingerlings in indoor tanks were 3–4 times higher than in other months, implying that year-round production would require hybrid striped bass fingerling growers to receive higher prices to cover costs of production in winter months.     

杂交条纹鲈苗种培育技术试验

根据对引进的美国杂交条纹鲈的生长发育需求及生理生态要求和食性，应用我国池塘精养技术，肥水培育苗种，进行调控水质，培养天然饵料，精心投喂，科学管理，经1年饲养管理，共出塘鱼种26000余尾，平均全长达14．0cm，平均尾重31．9g，成活率达22．7％。得出初步的苗种培育技术。     

Production Characteristics of Striped Bass × White Bass and Striped Bass × Yellow Bass Hybrids

The potential for commercial culture of hybrid striped bass is promising in many areas of the United States. While several different striped bass hybrids are candidates for culture, differential performance has not been thoroughly evaluated. Comparative performance of two striped bass hybrids was evaluated in six, 757–1, fiberglass tanks receiving a continuous flow of ambient pond water for 397 d. Three replicate tanks were stocked with 50 fingerlings (66 fish/m³) of either striped bass female × white bass male (mean weight 23 g) or striped bass female × yellow bass male hybrids. Fish were fed a 35% protein ration throughout the study, and weight was recorded for all fish at stocking and at 21-d intervals. White bass hybrids grew significantly faster (0.94 g/d) than yellow bass hybrids (0.59 g/d). Survival to harvest averaged 65% and 44% for yellow bass and white bass hybrids, respectively. A significant difference from the expected 1:1 sex ratio occurred for yellow bass hybrids (100% female), but not for white bass hybrids (56% female). Mean condition factor, 1.63 and 1.39, and fillet percentage, 30.7% and 28.4%, was significantly higher for white bass hybrids compared to yellow bass hybrids.     

Production Costs of Juvenile Penaeid Shrimp in an Intensive Greenhouse Raceway Nursery System

This analysis compared the use of an intensive nursery raceway system with direct stocking of post-larval shrimp into growout ponds. The intensive raceway system allows two crops to be produced in Texas where only one crop is feasible with direct stocking. Both investment and operational costs are analyzed for three types of greenhouses and three types of raceways where the types vary in cost and lengths of life. Three growout pond stocking densities and two farm sizes were evaluated for each combination of greenhouse and raceway type. Investment costs ranged from $142,000 for the small farm using the least expensive greenhouse and raceway and utilizing the lowest stocking density, to about $2.3 million for the large farm using the most expensive greenhouse and raceway and the highest stocking density in the growout ponds. The operational cost was $7.60 and $9.71 respectively per 1,000 one gram juveniles produced. Under technology available at the time of this analysis, direct stocking growout ponds with PIS and producing one crop per year is more profitable than stocking one gram juveniles and producing two crops per year on the Texas coast.     

Trophic dynamics of a reservoir fishery following an introduction of a top predator: Insights from stable carbon and nitrogen isotopes

Trophic dynamics and conceptual niche spaces of top piscivores were assessed using stable isotope analysis following the introduction of hybrid striped bass Morone saxatilis (Walbaum) × Morone chrysops (Rafinesque) into an established reservoir fishery devoid of gizzard shad, Dorosoma cepedianum (Lasueur). Hybrid striped bass were initially stocked into Three Mile Lake, Iowa as an attempt to biologically control pervasive yellow bass, Morone mississippiensis Jordan & Eigenmann, populations. From the analyses, it concluded that hybrid striped bass predominately targeted prey fish located in the littoral habitats of the reservoir and did not selectively consume yellow bass as intended. Bayesian isotope mixing models described the diets of hybrid striped bass to include a variety of prey fish, predominantly consisting of young bluegill Lepomis macrochirus and yellow bass. Food resource overlap among hybrid striped bass, largemouth bass, Micropterus salmoides Lacépède, and walleye, Sander vitreus (Mitchill), appeared substantial based on the isotopic niche overlap model. Results from this case study, in conjunction with the hindsight that yellow bass populations became prolific even with stockings of hybrid striped bass, suggest that their use to control yellow bass populations may not be a viable management strategy in southern Iowa.     

Comparative Oxygen Consumption and Metabolism of Striped Bass Morone saxatilis and its Hybrid M. chrysops♀ xM. saxatilis♂

It has been reported that metabolic rates of striped bass Morone saxatilis and hybrid striped bass M. chrysops♀ x M. saxatilis♂ are different. A series of experiments were conducted to further characterize oxygen consumption and metabolism of striped bass and its hybrid, the sunshine bass. Oxygen consumption was measured to determine standard and routine metabolic rates of striped bass and hybrid striped bass in a freshwater, flow‐through tank system. Additionally, blood chemistry stress indicators of the two bass groups were compared in both fresh and brackish water. Hematocrit (% PCV) and hemoglobin were measured in order to compare oxidative efficiencies of the bass. Plasma glucose, chlorides, and cortisol levels were measured to compare the relative stress status of the two bass types reared under experimental conditions. No significant differences were found in average daily oxygen consumption between striped bass and sunshine bass for either standard metabolism (P= 0.92), or routine metabolism (P = 0.86). Standard metabolic rates of oxygen consumption were 69 ± 4.1 and 68 ± 3.5 mg 0₂/kg³/⁴ bw/h for sunshine bass and striped bass respectively. Routine metabolic rates were 132 ± 30 and 125 ± 30 mg O₂/kg^3/4 bw/h for sunshine bass and striped bass respectively. While there were no significant differences in oxygen consumption between species, normal feeding activity generally resulted in increased oxygen consumption by the fish. Striped bass had significantly lower hematocrit values (P= 0.0001), but significantly higher hemoglobin concentrations than sunshine bass maintained in freshwater (P= 0.0001). Striped bass had significantly higher (P= 0.0001) levels of plasma glucose compared to sunshine bass (176 ± 8.6 vs. 103 ± 5.6 mg/dL respectively). Plasma chloride levels for striped bass (123 ± 1.9 mEq/L) were significantly higher (P= 0.041) than plasma chloride levels of sunshine bass (117 ± 1.7 mEq/L). Plasma cortisol levels were significantly higher (P= 0.0081) for striped bass (147 ± 8.4 ng/mL) compared to sunshine bass (119 ± 5.6 ng/ mL) when reared in freshwater. When maintained in brackish water, sunshine bass had significantly higher hematocrit values (P= 0.0001), and hemoglobin concentrations (P= 0.0012) when compared to striped bass. However, sunshine bass had significantly higher hemoglobin concentrations (P= 0.0012) when compared to striped bass. In addition, plasma glucose levels were significantly lower (P = 0.0079) for sunshine bass (79 ± 4.1 g/dL) when compared to striped bass (115 ± 11 g/dL). There were no significant differences between the bass in levels of chlorides or cortisol. No differences were detected in oxygen consumption. However, hybrid striped bass may have more efficient oxidative metabolism due to elevated hemoglobin concentrations. While striped bass hemoglobin values tended to be higher in brackish water than in freshwater, sunshine bass hematocrit or hemoglobin values generally were significantly higher than striped bass in both fresh and brackish water. Based on these results, hybrid striped bass may be capable of directing more energy towards growth than striped bass due to more efficient oxidative metabolism and lower losses of energy related to increased stress.     

ECONOMIC ANALYSIS OF ALTERNATIVE EFFLUENT TREATMENT OPTIONS FOR POND PRODUCTION OF HYBRID STRIPED BASS IN AURORA,NORTH CAROLINA

The focus of this article is the post-harvest treatment of effluent from hybrid striped bass (HSB) pond aquaculture to meet effluent discharge standards for Biochemical Oxygen Demand (BOD; 5 mg/L) and chlorophyll-α (40 μg/L) established by the North Carolina Division of Water Quality (DWQ). The specific application is to HSB pond aquaculture in Aurora, North Carolina. A variety of effluent treatment options were proposed and evaluated based on their efficacy in reaching the new standards on a 28.8-ha (72-acre) HSB farm. The economic feasibility of the proposed options ranged from positive $499 to negative $121,691 using the partial budget methodology. Our results indicate that retaining water on-farm for subsequent production cycles instead of discharging had the highest positive impact ($499) on annual farm budgets and may reduce production costs without compromising fish yields. Application of effluents onto existing or newly planted trees was also an attractive alternative because of the possible generation of additional income and the conversion of a point source discharge into a non-point discharge. By conversion of a point source into a non-point source the pond effluents would also benefit from the additional biological treatment and filtration of the effluents by the trees and the associated soil organisms.     

Acute and Sublethal Effects of Ammonia on Striped Bass and Hybrid Striped Bass

Bioassays in static water (mean ± SD; temperature, 20–22 C; pH, 8.2–8.4; alkalinity, 205 ± 10 mg/L CaCO₃; total hardness, 220 ± 10 mg/L CaCO₃) were used to determine median lethal concentrations (LC₅₀) of un-ionized ammonia (NH₃-N) for striped bass Moronc saxatilis and hybrid striped bass M. saxatilis × M. chrysops. The 96 h LC₅₀ for striped bass was 1.01 ± 0.24 mg/L NH₃-N₃ and was significantly higher than the LC₅₀ for hybrid striped bass (0.64 ± 0.05 mg/L NH₃-N). The effects of sublethal ammonia were evaluated after fish were exposed for 96 h to 0.0, 0.25, or 0.5 mg/L NH₃-N or to additional exposure to oxygen depleted water (about 2.0 mg O₂/L). Plasma ammonia of striped hass did not change as sublethal ammonia increased, but exposure to oxygen depletion caused a decrease in plasma ammonia. In contrast, plasma ammonia of hybrid striped bass increased as environmental ammonia increased, and increased further after exposure to oxygen depletion. Plasma cortisol levels of striped bass were significantly higher and more variable than cortisol levels of hybrid striped bass; additional exposure to oxygen depletion increased this variability, but these responses may be due to the stress of handling and confinement. Mean differences also existed between species for hemoglobin and hematocrit, while differences in variability occurred for osmolality and oxygen depletion rates. Striped bass tolerated ammonia better than hybrid striped bass but were more susceptible than hybrid striped bass to the additional stress of oxygen depletion. Most changes in physiological characteristics were relatively independent of environmental ammonia, but they were affected by oxygen depletion challenge.     

Evaluation of Meat and Bone Meal in Practical Diets Fed to Juvenile Hybrid Striped Bass Morone chrysops×M. saxatilis

Juvenile hybrid striped bass ( Morone chrysops × M. saxatilis ) were fed one of eight diets to evaluate meat and bone meal as a source of crude protein and essential amino acids. Diets contained either 0, 15, 20, 25, 30, 35, 40 or 45% meat and bone meal substituted for an isonitrogenous amount of soybean meal and fish meal. All diets were fed for 7 wk, followed by a 2-wk digestibility trial. Mean consumption, weight gain, and feed conversion ratio were not significantly affected by addition of meat and bone meal into diets. Intraperitoneal and liver lipid concentrations were not significantly affected by meat and bone meal. Fillet proximate composition was not significantly different among treatments. Apparent crude protein, phosphorus, and amino acid availabilities were significantly lower in fish fed 45% meat and bone meal compared to fish fed 30% and lower concentrations and generally lower in fish fed greater than 30% meat and bone meal. Based on these data, it appears meat and bone meal can be used as the primary source of crude protein and essential amino acids in practical growout diets for hybrid striped bass, comprising as much as 45% of the diet. Nutrient availability values were lower in fish fed greater than 30% meat and bone meal and may restrict usage in some applications.     

Tilapia wild spawning control through predator fishes: Israelitrial with red-drum and hybrid bass

Tilapia wild spawning is a nuisance in warm freshwater aquaculture growout ponds. To cope with this problem two experiments were carried out with predatory fish that do not reproduce in fresh water. One experiment tested the capacity of hybrid bass (Morone saxatilis × M. chrysops) and red-drum (Sciaenops ocellatus) as predators of wild spawning of hybrid tilapia (Oreochromis niloticus × O.aureus), and the other compared predation effectiveness of red-drum of different sizes and stocking densities.Both hybrid bass and red-drum effectively reduced tilapia wild spawning and improved by 15–20% tilapia performance and food conversion ratio. These effects were obtained stocking small red-drum (20 g) or large red-drum (60–80 g) or bass (135 g) at stocking densities of 500–1000 predators/ha, together with 15000 tilapia/ha of 65–75 g. Hybrid bass stocked at 750/ha and large red-drum stocked at 500/ha presented over 90% survival. Red-drum at higher stocking density and/or lower stocking weight presented reduced survival (40–60%). Red-drum of all examined stocking weights presented better growth rates when stocked at 500/ha than at higher densities.     

Comparison of Growth Between Morone Hybrids (Palmetto and Sunshine) in Earthen Ponds

Palmetto bass are produced by crossing the female striped bass, Morone saxatilis, with the male white bass, Morone chrysops; whereas, the sunshine bass is the reciprocal cross. The hybrid striped bass industry typically rears sunshine bass in earthen ponds, because of the ease of handling, availability, and early maturation of the white bass female broodstock. Growth performance has been assumed similar between the crosses. Under commercial pond conditions, sunshine bass (19.8 ± 0.4 g (mean ± SEM)) and palmetto bass (23.2 ± 0.3 g) were grown to market size (617.0 ± 17.2 g sunshine and 620 ± 3.6 g palmetto) within 15 mo, yielding 4532.6 kg/ha. The net production between the crosses was not significantly different and averaged 4373.4 kg/ha. Feed conversion ratio (FCR) of sunshine bass (FCR 1.70) was better (P = 0.0158) than palmetto bass (FCR 1.76). Commercial processing metrics of each cross demonstrated significant differences, with sunshine bass exhibiting lower frame waste (P = 0.0457) than palmetto bass, probably due to fish body shape or conformational differences at this size. Without growth performance differences between the hybrids, there might be an advantage to rearing sunshine bass due to the slightly better FCR and increased skinless boneless fillet yield.     

Evaluation of Growth Performance and Whole-body Composition of Juvenile Hybrid Striped Bass Morone chrysops × Morone saxatilis and Red Drum Sciaenops ocellatus Fed High-protein and High-lipid Diets

To investigate potential use of increasing nutritional density of diets for rapid growth of warm‐water fishes, a feeding trial was conducted in which growth performance, body indexes, and whole‐body composition of juvenile hybrid striped bass fed diets comprising protein (49, 54, and 59%), lipid (16, 20, 23, and 28%), and energy (22.0–25.1 kJ/g) concentrations beyond established minimum levels were compared to those of fish fed a more typical commercial reference diet (37.5% crude protein, 10.5% crude lipid, and 19.6 kJ/g energy on a dry matter basis). A subset of the experimental diets and the commercial reference diet also were fed to juvenile red drum. After 6 wk of feeding, hybrid striped bass fed the high‐protein and high‐lipid diets showed much greater growth performance compared to fish fed the commercial diet. Increasing dietary protein level, but not lipid level, tended (P ≤ 0.1) to enhance weight gain and feed efficiency of hybrid striped bass. Hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and whole‐body protein were significantly (P < 0.01) influenced by dietary protein level. The dietary lipid and associated energy level had significant negative linear effects on daily feed intake. Linear regression analysis showed that dietary energy : protein ratio, largely influenced by dietary protein level, moderately but significantly influenced weight gain, HSI, IPF ratio, and whole‐body protein of hybrid striped bass and red drum. Red drum grew very similar to hybrid striped bass in response to the experimental diets. However, significant differences in HSI, IPF ratio, whole‐body protein, lipid, moisture, and ash between hybrid striped bass and red drum were observed, indicating species differences in protein and energy partitioning. In particular, the excessive lipid in the diet increased HSI and whole‐body lipid of red drum but not of hybrid striped bass.     

Acceptance and Consumption of Food by Striped Bass and Hybrid Larvae

Food acceptance, consumption and weaning times were investigated for striped bass ( Morone saxatilis ) and hybrid striped bass ( M. saxatilis × M. chrysops ) larvae. Experimental treatments consisted of: control groups of striped bass (SC) and hybrids (HC) fed Artemia nauplii; hybrids fed formula food (HF); and hybrids weaned from Artemia nauplii to formula food at 11–15 days (HF₁), and 18–22 days (HF₂) posthatch. The formula diet did not support growth and resulted in total mortality of the HF hybrids by the third week posthatch. HF₁ fish had significantly slower growth and lower survival than HF₂ of HC. The HF₂, HC and SC groups had similar growth and survival, which indicated no heterosis in hybrids. There were no differences in Artemia nauplii consumption by the SC and HC groups. Daily consumption increased exponentially for both groups (0.8 to 50–60 cal/day/larva between 7 and 30 days posthatch). Weight specific consumption (WSC) decreased initially and then increased for both groups. A mean WSC of 58% (range of 24–83%) was found for the combined SC and HC groups. Food conversion ratio, growth efficiency, caloric efficiency, and productive protein values were similar for striped bass and hybrid larvae.     

Increased Growth and Production of Striped Bass × White Bass Hybrids in Earthen Ponds

Four 0.1 hectare earthen ponds were stocked with 16,500 hybrid striped bass (female Morone saxatilis × male M. chrysops ) per hectare on 22 June 1982. Mean weight at stocking was 5.2 g ± 0.10 SE. Fish were fed to satiation two or three times daily with a dry commercial salmonid diet, and the ponds were aerated mechanically during periods of low dissolved oxygen during warm weather. Survival at harvest on 6 March 1983 averaged 84.7%, and mean weight of the fish was 170.2 g ± 2.66 SE. Average weights of fish from individual ponds ranged from 149.0 to 189.7 g. The ponds were restocked on 1 April 1983 with 10,000 fish per hectare averaging 193.6 g. Ten months later, average survival in 3 ponds was 83.9% (range, 81.3–87.0%) and mean weight was 656.3 g ± 5.51 SE. Average weights of fish from individual ponds ranged from 632.5 to 690.7 g. All fish in one pond died in June as a result of an aerator failure. Standing crop at harvest in the three remaining ponds averaged 5, 504 kg/ha (range, 5,247–5,765 kg/ha). Improvements in culture techniques resulted in approximately a 138% increase in production per hectare over that reported in a prior study. Results demonstrated that hybrid striped bass offer considerable potential for commercial aquaculture in warm temperate latitudes of the United States.     

The Effect of On-Farm Production of Various Sizes of Stocker Caffish Ictalurus punctatus on Farm Profitability.

Abstract— The effect of on‐farm production of various sizes of stocker catfish Ictalurus punctatus on farm profitability was compared to profitability of understocking fingerlings directly into multiple‐batch growout production. Vat‐graded catfish averaging 9 × 2 g (10 cm total length) and 27× 8 g (15 cm total length) were stocked into eight 0.1‐ha ponds at 100,000 fingerlingdha. Fish were fed once daily to apparent satiation and harvested 210 d after stocking. There were no significant differences (P < 0.10) in yield, feed conversion ratio (FCR), and survival across treatments. Mean gross yield (× SD) was 9,469 × 852 kg/ha and 8,846 × 2,099 kg/ha; net yield averaged 8,531× 885 and 6,374 × 2,189 kg/ha; FCR averaged 1.8 × 0.1 and 2.4 × 0.7, and survival averaged 38 × 7% and 26 ×11% for the 10‐cm and 15‐m fingerling stocking treatments, respectively. While experimental survival was low, varying survival rates of stockers in the economic analysis did not affect selection of the most profitable stocking strategies. The 15‐cm hgerlings reached a size significantly larger (361× 81 g or 32.8 × 2.2 cm) than the 10‐cm fingerlings (255 × 28 g or 29.6 × 1.4 cm) (P < 0.07). Whole‐farm budgets were developed based on three sizes of farm (65, 130, and 260 ha) and eight production strategies involving the purchase of different sizes of fingerlings for either understocking growout ponds (6,12, or 37‐g fingerlings) or to grow into stockers (114,135, 176, 255, or 361 9). Purchasing 37‐g advanced fingerlings for multiple‐batch production was the most profitable strategy for the three sizes of farm. The second most important profit‐maximizing strategy for larger farm sizes was single‐batch production with 255‐g stockers produced on‐farm, but purchasing 12‐g fingerlings to stock into multiple‐batch production was the second most profitable strategy for the smallest farm. Sensitivity analysis indicated that the results were robust to variation in survival, prices, and other production characteristics. Risk analysis indicated that purchasing 37‐g advanced fingerlings for multiple‐batch production was associated with the lowest levels of economic risk for growout production.     

Gynogen Production in Hybrid Striped Bass

Abstract.— Meiotic gynogens were produced using hybrid striped bass (♀ white bass, Morone chrysops , ×♂ striped bass, M. saxatilis ) eggs and white perch M. americana UV-irradiated sperm. Diploidy of the fertilized eggs was restored by application of hydrostatic pressure, which induced retention of the second polar body. Use of white perch sperm provided an unmistakable marker for detection of a paternal genetic contribution. Two assays were developed using the polymerase chain reaction (PCR) to amplify specific regions of the Morone genome . Primers for gene amplification were developed based on the DNA sequence of the striped bass growth hormone gene (SB-GH) or an anonymous striped bass locus (SBI-10). Control experiments using DNA from the three Morone species demonstrated that gene amplification yielded species-specific patterns of DNA fragments for both of these loci. Therefore, any progeny with a paternal contribution of a set of white perch chromosomes could be identified. Using these assays, we demonstrated that greater than 75% of the progeny obtained from successful experiments were true gynogens. These striped bass hybrid gynogens will provide the basis for future efforts to calculate gene-centromere distances and to identify markers linked to specific traits of interest to aquaculture.     

Comparison of Purified and Practical Diets Supplemented with or without β-Glucan and Selenium on Resistance of Hybrid Striped Bass Morone chrysops ♀× M. saxatilis ♂ to Streptococcus iniae Infection

This study was conducted to evaluate the efficacy of β-glucan and selenium supplements to the diet on increasing survival of hybrid striped bass Morone chrysops X M. saxatilis exposed to Streptococcus iniae. A 2 × 2 × 2 factorial design was employed by including purified casein/gelatin-based diets and practical menhaden fish meal-based diets with supplement! of either β-glucan from barley at 0 and 0.1 % of diet or sodium selenite at 0 or 0.2 mg/kg diet or a combination of these supplements. All diets were formulated to meet the nutritional needs of hybrid striped bass with the exception of selenium. The purified and practical basal diets contained 0.03 and 1.03 mg Se/kg, respectively, and the diets supplemented with sodium selenite had an additional 0.07 mg Se/kg on average. Juvenile hybrid striped bass initially averaging 2.44 ± 0.17 g/fish were fed the eight experimental diets in triplicate 110-L recirculating aquaria for 6 wk, after which they were immersed in a bath of S. iniae at 6.2 × 10⁶ CFU/mL for 2 h and monitored for 21 d. Weighi gain and feed efficiency were significantly (P < 0.05) affected by diet type and selenium supplementation, with fish fed practical diets and those supplemented with selenium having the greatest values. Supplementation of β-glucan to the purified or practical type diets did not significantly affect survival of fish after experimental infection. The most notable difference (P < 0.0001) was in the comparison of diet type; the survival rate of fish fed the practical diets was 75% compared to 35% for those fed the purified diets. Dietary supplementation of β-glucan did not enhance disease resistance in the present study. Fish fed menhaden fish meal-based diets were significantly more resistant to 5. iniae in comparison to the those fed the purified diets. Thus, nutritional influences on disease resistance of hybrid striped bass were evident in this study and warrant further investigation.     

Cage Culture of Hybrid Striped Bass in Indiana and Evaluation of Diets Containing Three Levels of Dietary Protein1

Culture of hybrid striped bass Morone saxatilis × M. chrysops has been increasing in selected regions of the United States. Because of their thermal tolerance, hybrids may have potential as a new commercial aquaculture species in the Midwest. In these studies, hybrid striped bass were reared in cages located in southern, central and northern Indiana and offered one of three practical diets. Diets contained either 32, 36 or 40% crude protein. Additionally, a preliminary 8 wk laboratory experiment was conducted in which fish were offered the same diets. All diets were formulated to meet the established dietary lysine requirement; optimal levels of other essential amino acids in the diet were predicted by the whole-body essential amino acid profile of hybrid striped bass. In the laboratory experiment, weight gain of fish fed 36% crude protein was significantly higher than those fed either other level of dietary protein. After 205 days, final average weight gains of fish in the field experiment were not significantly different and ranged from 233 to 426 g with an overall average daily gain of 1.6 g/fish/d. Overall survival was 89.1%. Dress-out percentages were 81.2, 69.8, and 34.9% for eviscerated, eviscerated and headed, and fillets, respectively. Those values were not significantly different among dietary treatments or sites. Lipid content of fillets from fish fed 32% dietary crude protein was significantly higher than in fish fed 36 or 40% crude protein.     

Growth performance of hybrid striped bass (Morone chrysops × M. saxatilis) fed with commercial pike perch and trout diets

Two commercial trout diets (Oncorhynchus mykiss) and one commercial pike perch diet (Sander lucioperca) were fed to hybrid striped bass (Morone chrysops × M. saxatilis) (mean initial weight ± SD of 60.7 g ± 12.1; mean initial length SD of 17.2 cm ± 1.1) for 69 days at rations of approximately 1% average body weight. While final body weight (FBW), final length (FBL) and condition factor (Cf) were not significantly influenced by diets, specific growth rate (SGR) in hybrid striped bass fed with the pike perch diet (1.15) was significantly higher than those fed with either of the two trout diets (1.04 and 1.07). The feed conversion ratio (FCR) in hybrid striped bass fed with the pike perch diet (1.0) was significantly lower than the FCR in hybrid striped bass fed with either of the two trout diets (1.1 and 1.2). When hybrid striped bass (mean initial body weight: 65.7 ± 4.5 and 127.7 ± 2.9 g) were fed with the pike perch diet twice per day until satiation for 52 days, the SGR was 1.7 and 1.15% d^?1 in fishes with an average body weight of 116 and 183 g, respectively. Present results demonstrate that growth performance in hybrid striped bass can be improved when fishes are fed with commercial pike perch diets rather than using commercial trout diets as is the current practice.