Sunshine Bass Research Articles

Initial investigations into the production of triploid sunshine bass using temperature shock

AbstractObjectiveThe sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) is an important food fish raised in U.S. aquaculture. Spawning is performed by manually stripping and fertilizing White Bass eggs with Striped Bass sperm. Embryos hatch in approximately 48 h. Mature sunshine bass females can become fertile and produce viable eggs, which is problematic in commercial food‐fish production; therefore, triploid fish are desired.MethodsThe present nonreplicated study incorporated three warm and three cold temperature shocks, along with three postfertilization initiation times and three exposure times for each temperature, during initial stages of incubation to induce triploidy. After exposure to temperature shocks, fertilized eggs were incubated in experimental hatching systems. The best performing cold and warm temperatures and times (and an ambient diploid control) were then used to incubate fertilized eggs in a commercial‐scale trial using standard industry practices with a single batch of eggs. Larvae were stocked at about 185,000 larvae/ha (75,000 larvae/acre) in newly filled and fertilized ponds. Fry were sampled weekly and harvested at 30 days.ResultThere were 15 survivors from the pond containing fish derived from cold‐shocked fertilized eggs; these individuals were tested via Coulter Counter, and no triploids were detected. Testing of 50 survivors from the pond containing fish derived from warm‐shocked fertilized eggs indicated that 14% were triploid.ConclusionTherefore, initial trials indicate that warm temperature shock is preferable to cold shock for inducing a greater percentage of triploid sunshine bass.

The impact of cottonseed meal condition on water quality, zooplankton densities, and sunshine bass production when used as an organic fertilizer in ponds

AbstractObjectiveCottonseed meal is applied to sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) fry rearing ponds as an organic fertilizer to stimulate plankton development. The efficacy of cottonseed meal as a fertilizer following long‐term storage and degradation is unknown. The use of degraded and undegraded cottonseed meal were compared during the production of sunshine bass fingerlings in lined 0.4‐ha ponds.MethodsFilling ponds were fertilized repeatedly between 13 days before and 6 days after fry stocking, and water quality, zooplankton, and 41–48‐day fingerling production were monitored. Adequate phytoplankton and zooplankton densities were maintained using cottonseed meal of both conditions.ResultCottonseed meal condition had no significant impact on any fish production metric. The degraded cottonseed meal appeared to release nitrogen more readily as indicated by higher prestocking NH3‐N concentrations. Higher nutrient availability likely stimulated primary productivity at a faster rate, leading to higher dissolved oxygen, pH, and zooplankton densities during the first half of the pond cycle. The ponds fertilized with degraded cottonseed meal required more intensive water quality management to maintain adequate dissolved oxygen and pH for sunshine bass fry. However, poststocking water quality parameters were within species tolerance ranges.ConclusionThe study confirmed that degraded cottonseed meal can be used as an organic fertilizer in sunshine bass fry rearing ponds without compromising fingerling production, provided ponds are managed appropriately.

Evaluation of Settling Chamber Hydraulic Retention Time in a Sunshine Bass Biofloc Production System

AbstractHigh total suspended solids (TSS) concentrations that result from the high feeding rates used in biofloc technology production systems can negatively impact fish performance. Excess TSS are removed from biofloc production tanks by side‐stream settling chambers. The effects on solids removal, water quality dynamics, and performance of sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) from three settling chamber hydraulic retention times (HRTs; 18, 43, and 87 min; designated HRT18, HRT43, and HRT87, respectively) were evaluated in this 126‐d study in biofloc tanks. Corresponding settling chamber flow rates were 7.2, 3.0, and 1.5 L/min, respectively, and corresponding tank turnover times were 8.3, 20.0, and 40.0 h. Upon activation of settling chambers, the TSS concentration decreased faster in the HRT87 treatment than in the other two treatments. The dry matter mass of solids discharged each time the settling chambers were drained and the total dry matter mass of solids discharged both increased linearly with HRT. Compared to the HRT43 and HRT87 treatments, nitrate‐nitrogen in the HRT18 treatment accumulated about 17% more slowly and 25% less sodium bicarbonate was needed, which suggests that nitrification was impacted negatively by the elevated settling chamber flow rate. Denitrification was not detected in settling chambers given the absence of significant differences between influent and effluent dissolved inorganic nitrogen concentrations in all treatments. Sunshine bass performed well in all treatments, with overall production averaging 4.4 kg/m3 at 81.9% survival. Although sunshine bass were grown successfully to market size in biofloc culture, future research should address higher stocking rates and settling chamber operational parameters to maintain higher TSS concentrations and promote denitrification. Thus, the results of this study suggest that a minimum settling chamber HRT of 43 min is appropriate for biofloc culture of hybrid striped bass.

Larval development staging table for hatchery-reared sunshine bass (Morone chrysops♀ x Morone saxatilis♂)

Aquaculture of hybrid Morone species is preferred over that of purebred strains due to their higher growth rates and resilience to a wide range of rearing conditions. One of the most popular hybrids is the sunshine bass, which is a cross between white bass (M. chrysops) females and striped bass (M. saxatilis) males. Yet, despite their growing economic importance, a detailed description of sunshine bass larval development under captive conditions is missing. Here, we provide a detailed staging system of hatchery-reared sunshine bass larvae. Based on externally visible features, we define 15 distinct stages from hatching to juvenile stage (2–43 days post-fertilization). We identified a biphasic pattern of larval growth, with a 2-fold increase in growth rates (from 0.2 to 0.4 mm/day) around the onset of metamorphosis and larger variations in length and weight after the completion of metamorphosis. Both age (R2 = 0.93) and standard length (R2 = 0.89) were good predictors of larval stage. Overall, this work provides a reference for studies of factors that affect sunshine bass larval development and, thus, is an important step towards resolving bottlenecks in larval rearing operations in this species.

Nutritional Utilization of Modified Carinata Brassica carinata Meals in Sunshine Bass Diets

AbstractLow amounts (approximately ≤ 10%) of raw carinata Brassica carinata meals are used in animal diets due to the negative effects of antinutrients, mainly glucosinolates. We processed carinata meal by aerobic conversion followed with a single wash (ACCM). Another portion of carinata meal was double‐washed without aerobic conversion (WCM). The objective of this study was to determine if sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) fed diets containing low (20%) animal meals could tolerate up to 30% of ACCM or 30% of WCM. Twenty randomly selected sunshine bass (19.2 ± 0.08 g) were stocked in each tank (106 L) of a 32‐tank recirculating aquaculture system, with temperature maintained at 25.6 ± 0.7°C using an inline heater. Seven and six replicates were used for the reference and test diets (10% or 30% ACCM or 30% WCM), respectively, and the fish were cultured for 106 d. Growth improved with increasing levels of processed carinata meals in diets. Survival (>99%) was similar among dietary treatments. Consumption of 30% ACCM and 30% WCM diets was higher than for the reference diet. Feed conversion ratio improved in the WCM dietary treatment and was associated with a better protein efficiency ratio and apparent net protein utilization. Protein deposition was highest in sunshine bass fed 30% of processed carinata meals. Whole‐body protein also increased with increasing processed carinata meals in diets. Sunshine bass fed 30% WCM had lower liver weights and were in better condition than sunshine bass fed other diets. Hematocrit was high in sunshine bass fed ACCM diets. Although carinata meal is high in iron, the single wash in ACCM processing likely removed less iron than the two washes in WCM processing. Hemoglobin contents of sunshine bass were also increased by ACCM but not by WCM. Our results demonstrate that high levels of even moderately processed carinata meal (WCM) can be tolerated in fish diets without affecting fish performance.

Listeria monocytogenes is inhibited on fillets of cold‐smoked sunshine bass, Morone chrysops × Morone saxatilis, with an edible corn zein‐based coating incorporated with lemongrass essential oil or nisin

Ready‐to‐eat (RTE) foods have been identified as a high‐risk food group because of the number of outbreaks caused by food‐borne pathogens isolated from these products. As these items receive no further processing or heat treatment prior to consumption, bacterial pathogens such as Salmonella, Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes present a serious threat to consumer safety. Of particular concern, L. monocytogenes is resistant to various food storage techniques, including reduced or modified atmosphere packaging, refrigerated storage, and increased salt concentration. Cold‐smoked fishery products have been implicated in a number of listeriosis cases, where it is estimated that between 6 and 36% of cold‐smoked fish is contaminated with L. monocytogenes. Edible coatings incorporated with natural antimicrobials have been suggested to control pathogenic and spoilage bacteria on a variety of meat products. In this study, edible zein‐based coatings incorporated with nisin and lemongrass essential oil (LG) (8%) were evaluated for antibacterial action against L. monocytogenes and spoilage organisms on cold‐smoked, cultured hybrid striped bass, Morone saxatilis × Morone chrysops, under polyvinyl chlorine (PVC) and vacuum packaging for 14 days (PVC) and 42 days (vacuum packaging), respectively, at 4°C. In this study, corn zein‐based edible coatings were found to be an effective carrier for nisin and LG. Nisin‐treated samples were most effective against L. monocytogenes in both PVC and vacuum‐packaged fillets, with a total reduction of 3.5 log and 3.7 log, respectively over the length of the storage time. LG‐treated samples reduced L. monocytogenes cell counts by 2.5 log in PVC and 1.7 log in vacuum‐packaged samples. Only LG‐treated samples packaged in PVC were found to inhibit the growth of spoilage organisms. Because nisin‐ and LG‐treated fillets reduced L. monocytogenes, they may be useful methods to improve food safety in smoked seafood.

Toxicity of Peracetic Acid to Fish: Variation among Species and Impact of Water Chemistry

AbstractThere has been strong interest in the use of peracetic acid (PAA) in aquaculture as it can be used to disinfect water and hard surfaces and thereby eliminate or lower the burden of fish pathogens. Unfortunately, there has been little research on the toxicity of PAA to fish. Twelve species of fingerling fish that are important to aquaculture were exposed to PAA for 24 h in static toxicity bioassays in well water. These fish were: fathead minnow, Pimephales promelas; black‐nose crappie, Pomoxis nigromaculatus; bluegill, Lepomis macrochirus; blue tilapia, Oreochromis aureus; channel catfish, Ictalurus punctatus; golden shiner, Notemigonus crysoleucas; goldfish, Carassius auratus; grass carp, Ctenopharyngodon idella; largemouth bass, Micropterus salmoides; rainbow trout, Oncorhynchus mykiss; sunshine bass, Morone chrysops × M. saxatilis; and walleye, Sander vitreus. Median lethal concentration (LC50) values were estimated with the trimmed Spearman–Karber method using nominal PAA concentrations. The mean 24‐h LC50 values ranged from 2.8 to 9.3 mg/L PAA. Fathead minnow were very sensitive and blue tilapia were very tolerant to PAA exposure; LC50 values of other species tested were within the range of 4.1–6.2 mg/L PAA. More importantly, the 24‐h no‐observed‐effect concentration (NOEC) ranged from 1.9 to 5.8 mg/L PAA; the NOEC would be considered as the safe range for culturists to investigate the use of PAA. Decreased alkalinity/hardness increased the toxicity of PAA, while a small increase of dissolved organic content had no effect on PAA toxicity. Results of the present study are important information on the safe application of PAA for the aquaculture industry.

Salinity Has Limited Influence on Sedation of Sunshine Bass with AQUI-S 20E (10% Eugenol)

AbstractWe evaluated sedation and recovery of juvenile sunshine bass (male Striped Bass Morone saxatilis × female White Bass M. chrysops) exposed to AQUI-S 20E (10% eugenol; 60 mg/L) in freshwater or increasingly brackish salinities (nominal salinities of 0, 5, 10, 15, 20, and 25 g/L). Induction and recovery times were significantly affected by salinity, but the magnitude of the effects was relatively small. Induction was fastest (0.90 min) among fish tested at 25 g/L salinity and slowest (1.07 min) among those tested at 0 g/L salinity, but this was the only significant difference observed in induction times between treatments. Recovery was also faster among fish that were tested at higher salinities and slower among fish that were tested at lower salinities (range = 2.63–3.91 min), but significant differences were not noted for each pairwise comparison. Most fish (65%) exhibited slight agitation and gasping or piping at the surface during sedation, but these behaviors were less common among fish held at ...

Sea Clam‐Derived Feeding Stimulants Enhance Acceptability and Intake of Reduced Fish Meal, Soy‐Based Sunshine Bass Feeds

AbstractFish meal sparing or replacement is limited by reduced diet acceptability and feed intake, particularly among carnivorous finfish. Two 8‐week feeding trials were conducted to assess whether the inclusion of sea clam (ocean quahog Arctica islandica) processing by‐products could improve the intake of reduced fish meal feeds in sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis). In trial 1, juvenile fish (31.9 ± 0.2 g, average initial weight) were cultured at 18.5 ± 2.4°C and fed diets containing 30% fish meal (hereafter, “FISH”), 6.7% fish meal (remainder of dietary protein primarily provided by soybean meal; hereafter, “SOY”), or the reduced fish meal formulation amended with 1% dried clam juice (hereafter, “SOY + clam juice”), dried clam fines (hereafter, “SOY + clam fines”), or betaine as feeding stimulants. In trial 2, fish were slightly smaller at the outset (18.4 ± 0.3 g) and cultured at 27.3 ± 0.2°C. Growth performance was generally superior among fish reared in trial 2, but both trials yielded similar results in terms of dietary treatments. Feed intake and growth were reduced among fish fed the SOY feed compared with those fed the FISH feed. The addition of betaine to the reduced fish meal formulation did not improve diet acceptance or intake. However, the inclusion of clam by‐products improved feed intake and growth, with both the SOY + clam juice and SOY + clam fines feeds yielding growth equivalent to the FISH feed. Semiquantitative evaluations of feeding behavior suggest that dietary treatment effects were rooted in differences in feed acceptability and that the inclusion of clam by‐products had a corrective effect on the comparatively indifferent feeding observed among fish fed the SOY diet. The inclusion of sea clam by‐products, particularly dried clam fines, improved the intake of the reduced fish meal formulation, and these by‐products appear to be effective feeding stimulants in soy‐based feeds for juvenile sunshine bass grown in tanks.

Use of Copper Sulfate to Control Egg Saprolegniasis at a Commercial Sunshine Bass Hatchery

AbstractAn obstacle to the larval production of sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) is fungal growth on the eggs caused by the water mold, Saprolegnia spp. Copper sulfate (CuSO4) is commonly used for fungus control in troughs at catfish hatcheries, but the effectiveness in other fish‐egg hatching systems is unknown. Because sunshine bass eggs begin hatching after 48 h, CuSO4 treatments (0, 10, 20, and 40 mg/L) began the afternoon of spawning with a 10‐min, aerated, static bath and were repeated the morning and afternoon of day 2; eggs were not treated after hatching began. An in vitro assay was developed for this treatment regimen that indicated maximum fungal inhibition was achieved with 20 mg/L CuSO4. In the effectiveness experiment in McDonald hatching jars (n = 3), fungus was severe in the untreated controls (27.7% survival), but very little fungus was present in treatments receiving 10 mg/L CuSO4 (31.4% survival) or higher. The control was not significantly different from the 10‐mg/L treatment. The highest survival was at 40 mg/L CuSO4 (50.5% survival); however, the survival from the 20‐mg/L CuSO4 treatment (45.8%) was not significantly different from that in the 40‐mg/L treatment and thus allows for a greater margin of safety. Fungus samples were identified as Saprolegnia ferax through genetic sequencing. Toxicity experiments on sunshine bass larvae indicated the 24‐ and 48‐h LC50 values were 5.4 and 3.9 mg/L CuSO4, respectively; the no observed effect concentrations were 0.5 and 0.25 mg/L CuSO4, respectively. This study confirms that CuSO4 can be an economical and valuable resource in hatchery management for the control of saprolegniasis on sunshine bass eggs in McDonald jars.

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

AbstractPalmetto 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.

Variability in Size Traits of Sunshine Bass Larvae from Different Male Striped Bass

AbstractWe examined the amount of variability in size at hatch and size at yolk absorption among sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) due to sire effects. Eggs from a female White Bass were separated into four aliquots. Each aliquot was fertilized by sperm from a different male Striped Bass. Single fertilized eggs were place in 6‐mL vials and incubated at 18°C. Eggs were examined every 6 h until the first eggs hatched and every 3 h thereafter. Approximately 50–100 yolk sac larvae were removed from the vials at hatching, photographed, and returned live to the vials when possible. At 5 d posthatch (dph), the remaining larvae were photographed and enumerated. Standard lengths of larvae at hatch and at 5 dph were estimated from photographs. Growth (i.e., increase in length) during the endogenous larval stage was calculated for a subset of individuals photographed at both times. This process was repeated in two subsequent trials. There were significant sire effects for size at hatch (P = 0.003), size at 5 dph (P < 0.001), and growth (P < 0.001). The sire effect explained 3.0–39.0% of the variability in these size traits. Genetic selection for favorable size traits at early life stages among both parent species could lead to larger sunshine bass larvae at yolk absorption and eliminate the need for rotifers at first feeding. Rapid growth at early life stages may be an indicator of rapid growth at later life stages. Efforts to select for rapid growth at several life stages could enhance multiple aspects of the hybrid Striped Bass industry.

Evaluation of Hydrogenated Soybean Oil in Feeds for Hybrid Striped Bass Fed in Conjunction with Finishing Periods of Different Durations

AbstractWe evaluated the production performance and tissue composition of hybrid striped bass, i.e., sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis (initial weight = 110.6 g) raised to a marketable size (final weight = 575 g) on grow‐out feeds containing graded levels of fish oil and hydrogenated soybean oil (100% fish oil, 50% fish oil and 50% soybean oil, 25% fish oil and 75% soybean oil, or 100% soybean oil) in conjunction with finishing periods of different durations (4, 8, or 12 weeks of feeding the 100% fish oil feed prior to harvest). Production performance varied significantly among the feeding regimens, but none of the experimental groups were significantly different from the 100% fish oil control group. However, performance tended to follow fish oil consumption, with regimens providing more fish oil during grow‐out yielding marginally superior growth and growth efficiency. Fillet fatty acid profiles varied considerably among the regimens prior to finishing. Fillets of fish fed diets containing increasing amounts of hydrogenated soybean oil contained more monounsaturated fatty acids (18:1[n‐9]) and (n‐6) and fatty acids (18:2[n‐6]) and less long‐chain polyunsaturated fatty acids and (n‐3) fatty acids (20:5[n‐3] and 22:6[n‐3]). Despite major differences in dietary levels of saturated fatty acids (SFAs), fillet levels of SFAs did not vary appreciably. Profile differences arising during grow out were reversed by finishing, to a greater or lesser extent, depending on the magnitude of prefinishing profile distortion and the duration of the finishing period. Utilization of hydrogenated soybean oil merits further consideration and research, but our results suggest that this feedstuff has value as a supplemental lipid source, if not a complete fish oil substitute, in feeds for hybrid striped bass.

Refining Ammonia Treatments for Control of Prymnesium parvum in Striped Bass Fingerling Production Ponds

AbstractTexas state fish hatcheries use un‐ionized ammonia nitrogen (NH3‐N) treatments of 0.14–0.25 mg/L to control Prymnesium parvum in production ponds for phase‐1 Striped Bass Morone saxatilis based on a published ammonia tolerance for 4‐ to 6‐d‐old Sunshine Bass (female White Bass M. chrysops × male Striped Bass M. saxatilis). Because fingerling production has been inconsistent and the treatments require frequent reapplications to maintain control of P. parvum, we conducted this study to answer two questions: (1) are the treatments developed for Sunshine Bass appropriate for Striped Bass culture, and (2) can the maximum treatments be increased as the fish grow. Striped Bass (4, 10, 20, and 28 d old) were exposed to NH3‐N concentrations up to 1.2 mg/L for 96 h. Ammonia concentrations and fish mortalities were monitored at 24‐h intervals, their relationship modeled using logistic regression, and ammonia concentrations that 90% of the fish survived during the various exposure periods (maximum treatments) were estimated. The 4‐ to 6‐d‐old Striped Bass survived ammonia concentrations similar to those of Sunshine Bass of the same age‐group. The 20‐d‐old fish were the least tolerant of NH3‐N, followed by 4‐d‐old fish and then 10‐d‐old fish. The 28‐d‐old fish was the most tolerant of ammonia toxicity. The maximum treatment varied with fish age. Thus, the current practice of treating for concentrations between 0.14 and 0.25 mg NH3‐N/L throughout production of phase‐1 fish is inappropriate. Treating with 0.14‐ to 0.25‐mg NH3‐N/L can be suitable for culture of Striped Bass fry and fingerlings, except for fish in the 22–24‐d age range. The upper limit of concentration may be increased up to 0.37 and 0.40 mg NH3‐N/L for 10‐ to 12‐d‐old and 28‐ to 30‐d‐old Striped Bass, respectively. However, the concentration must be lowered to 0.1 mg NH3‐N/L for 22‐ to 24‐d‐old Striped Bass.

Utilization of Soluble Canola Protein Concentrate as an Attractant Enhances Production Performance of Sunshine Bass Fed Reduced Fish Meal, Plant‐Based Diets

AbstractSoluble canola protein concentrate (SCPC) is rich in glutamic acid and may act as a feed attractant to improve feed acceptance and production performance of fish fed plant‐based diets. In the first experiment, attractant properties of SCPC were evaluated by comparing production performance of sunshine bass, Morone chrysops × Morone saxatilis, fed reduced fish meal (FM) diets supplemented with 1% SCPC or a betaine‐based feed attractant. In the second experiment, production performance of fish was compared after feeding reduced FM diets with or without SCPC. Following the first experiment, production performance was similar among fish fed attractants, but at 0% FM weight gain and survival were significantly lower compared to the 30% FM control treatment regardless of attractant inclusion. According to broken‐line analysis of data from the second experiment, the critical breakpoints in dietary FM inclusion rates needed to achieve maximal weight gain were similar regardless of SCPC. However, weight gain observed among fish fed SCPC was significantly greater than fish not fed SCPC. Including FM in plant‐based sunshine bass diets at rates >10–13% dry matter did not improve weight gain, and weight gain is optimized when a feed attractant/palatant such as SCPC is included in these plant‐based diets.

Assessment of Aquaflor®, copper sulphate and potassium permanganate for control of Aeromonas hydrophila and Flavobacterium columnare infection in sunshine bass, Morone chrysops female × Morone saxatilis male

Two experiments were conducted to test the effectiveness of different therapeutants against a mixed infection of Aeromonas hydrophila and Flavobacterium columnare in sunshine bass. Experiment 1 evaluated copper sulphate, florfenicol-medicated feed and potassium permanganate (KMnO(4) ) against a natural mixed infection. Experiment 2 further evaluated copper sulphate as a treatment to control an experimental mixed infection. In experiment 1, naturally infected untreated fish had the lowest final survival per cent, at 71%, while florfenicol-medicated feed at 15mgkg(-1) body weight for 10days or copper sulphate at 2.1mgL(-1) (1% of the total alkalinity) for 24h produced the highest final survivals, at 90% and 88%, respectively. The final survival of the naturally infected fish administered florfenicol-medicated feed was significantly different (P<0.1) from the untreated fish. The survival curves for the florfenicol and the copper sulphate at 2.1mgL(-1) were significantly improved from the untreated fish. In experiment 2, fish were challenged by waterborne exposure to A. hydrophila and F. columnare and either not treated or treated with copper sulphate at 2.1mgL(-1) . At the end of experiment 2, the per cent survival of the challenged fish treated with copper sulphate (99%) was significantly higher (P<0.05) than the non-treated (61%). The results illustrate clear benefit of florfenicol and copper sulphate against a mixed infection of A. hydrophila and F. columnare.

Response of sunshine bass (Morone chrysops x M. saxatilis) to digestible protein/ dietary lipid density and ration size at summer culture temperatures in the Southern United States

Temperature and ammonia levels often increase dramatically in ponds during summer production of sunshine bass and summer temperatures are projected to increase in the Southern US. Extended periods of high ammonia result in fish stress, disease, mortality and significant loss of feeding days as producers attempt to reduce ammonia to manageable levels through reduced feeding or lower protein diets. A factorial feeding trial was conducted in temperature controlled tanks to investigate main and interactive effects of three digestible protein (DP) levels (33, 40, 47%), two lipid levels (10, 18%) and two ration levels (full fed: satiation, restricted: 80% of satiation) on growth, body composition, nutrient and amino acid retention, and ammonia and phosphorus excretion in sunshine bass (mean weight:75g) reared at elevated temperature (30.5±0.5°C) . Diets were balanced on an available amino acid basis to the profile of hybrid striped bass muscle and supplemented with lysine and methionine at the equivalent of 330, 400, or 470g/ kg of muscle protein. Each DP x lipid x ration treatment was fed to triplicate tanks of fish for 116days. All measured responses were significantly altered by main and interactive effects, but the patterns of interaction were similar among responses. Restricted feeding resulted in much lower final weights and weight gains but much higher ammonia excretion as a function of feed or N fed and body weight (BW), regardless of DP level. Lower dietary fat (10%) resulted in lower weight gains and poorer feed conversions as well as higher ammonia excretion (per gN fed/kg BW) regardless of DP or ration level. Weight gain (475%) and final fish weight (434g) were highest at 47% DP/18% dietary lipid, but feed conversion, protein, energy and amino acid retention efficiencies were markedly poorer in the 47% DP diets regardless of lipid level due to hyperphagia in fish fed this diet. The 40/18 diet consistently outperformed the 33/18 diet in better growth and lower ammonia excretion as a function of N fed/ BW, and nearly equaled the growth attained by fish fed 47/18 diet. Increasing ration to satiation at elevated temperature resulted in much greater improvements in weight gain, final weight and ammonia excretion of fish fed the 40/18 diet, as opposed to those fed the 33/18 diet. Amino acid retentions were nearly equal between the 33/18 and 40/18 diets and restricting feed to 80% of satiation slightly improved feed conversions and protein and amino acid retentions. Consistent lipid x DP interactions generally indicated that the differences among responses to DP level seen at 18% dietary lipid significantly decreased or disappeared at 10% dietary lipid. Phosphorus excretion was low and not significantly altered by main effects. Results suggest that a producer desiring to reduce pond ammonia with the least compromise to production efficiency would be better served by feeding a 40% DP/ 18% lipid diet at a reduced level instead of switching to a lower protein diet.

Safety of Aquaflor‐Medicated Feed to Sunshine Bass

AbstractAquaflor (florfenicol, 50% type A medicated article) is a relatively new antibiotic used in U.S. aquaculture and has been widely accepted as a safe and effective therapeutant. Some peer‐reviewed studies have suggested that 15 mg florfenicol (FFC)·kg−1 body weight (BW)·d−1 for 10 d controls mortality to a greater extent than 10 mg FFC·kg−1 BW·d−1 for 10 d. This study evaluated the safety of Aquaflor to sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis) when administered in feed at 15 (1× the maximum proposed therapeutic dose), 45 (3×), and 75 (5×) mg FFC·kg−1 BW·d−1 for 20 d (2× the currently approved 10‐d treatment duration). The medicated feed was top‐coated with Aquaflor and fed at 2% BW·d−1 divided equally between the morning and afternoon feedings. Juvenile sunshine bass (13.6 ± 1.6 g [mean ± SD]) were stocked into 100‐L flow‐through tanks at 20 fish per tank. Diets were randomly assigned to three replicate tanks per treatment; fish in three additional nonstudy tanks were fed control diets and weighed weekly to calculate proper feeding quantities. Throughout the trial, water quality was maintained within ranges suitable for sunshine bass culture, fish behavior appeared normal, and all feed was readily and rapidly consumed. There were no mortalities and fish health evaluations revealed no chronic toxicity patterns. None of the histopathologies distinctive to the use of Aquaflor were observed. In conclusion, there is an adequate margin of safety associated with administering Aquaflor‐medicated feed to fingerling sunshine bass at the proposed therapeutic treatment regimen of 15 mg FFC·kg−1 BW·d−1 for 10 d.

In vitrocomparisons of the inhibitory activity of florfenicol, copper sulphate and potassium permanganate towardsAeromonas hydrophilaandFlavobacterium columnare

Aeromonas hydrophila and Flavobacterium columnare, the aetiological agents of motile aeromonas septicaemia (MAS) and columnaris disease respectively, have been recently causing crippling mortalities to the sunshine bass, Morone chrysops female ×Morone saxatilis male (Percichthyidae), industry in the United States. Isolates of A. hydrophila and F. columnare obtained from fish that died during farm outbreaks were subjected to in vitro evaluation of florfenicol (FFC), copper sulphate (CuSO4) and potassium permanganate (KMnO4). Florfenicol inhibited the growth of A. hydrophila and F. columnare more than CuSO4 and KMnO4. The minimum inhibition concentration (MIC) of FFC was 0.04 ± 0 and 0.2 ± 0.1 mg L−1 for A. hydrophila and F. columnare respectively, while the 50% inhibition concentration (IC50) for A. hydrophila and F. columnare was 0.23 ± 0.01 and 0.4 ± 0.2 mg L−1 respectively. Copper sulphate was more effective against A. hydrophila than KMnO4; CuSO4 had a MIC of 83.2 ± 0 mg L−1 compared to 158.0 ± 0 mg L−1 for KMnO4. Copper sulphate was also more effective against F. columnare than KMnO4. The IC50 values of CuSO4 and KMnO4 towards F. columnare were 4.8 ± 0.3 and 8.7 ± 1.6 mg L−1 respectively, and the minimum bactericidal concentration values of CuSO4 and KMnO4 towards F. columnare were 25.0 ± 0 and > 158.0 mg L−1 respectively. In addition, F. columnare was more sensitive to CuSO4 and KMnO4 than A. hydrophila.

Replacement of Marine Feedstuffs with Stabilized Poultry Protein Meal and Fat in Practical Diets for Sunshine Bass, Morone chrysops × M. saxatilis

We evaluated production performance and fillet composition of sunshine bass fed increasing levels of stabilized poultry protein meal (PM) and poultry fat (PO) to replace menhaden fish meal (FM) and/or oil (FO) in diets. The control diet included 200 g/kg (dry matter basis) FM and 98 g/kg FO. In eight treatment diets, 50% or 100% of the FM and/or FO were replaced with PM and PO. Each diet was fed to four replicate tanks of juvenile sunshine bass for 10 wks. Survival, food conversion ratio, and liposomatic index were unaffected by dietary treatment, although consumption, growth, and HSI were reduced with complete FM replacement. Fillet lipid content and athero- and thrombogenicity indices differed with lipid source; substitution of FO with PO resulted in marked increases in dietary and fillet monoenes and n-6 fatty acids. Consistent with this, dietary and fillet n-3 and highly unsaturated fatty acids were reduced in fish fed more PO. FM replacement similarly affected fillet fatty acid profile, though to a lesser degree. Our data suggests little to no interaction between FM, FO, and their alternatives in diets for sunshine bass, except with respect to the effect of FO and residual lipids in FM on tissue fatty acid composition.