Dietary Protein and Lipid Requirements for Juvenile Largemouth Bass,Micropterus salmoides

A feeding trial was conducted to evaluate dietary protein and lipid requirements for juvenile largemouth bass, Micropterus salmoides. A 4 × 2‐factorial layout included four protein (420, 450, 480, and 510 g/kg) and two lipid (80 and 120 g/kg) levels. Fish (initial weight 8.7 g) were fed the test diets for 8 wk. Weight gain, feed intake, feed conversion ratio, hepatosomatic index, and body composition were dependent on dietary protein level. Nitrogen retention efficiency was independent of dietary protein level, lipid level, and their interaction. Weight gain was higher in fish fed the diet containing 480–510 g/kg crude protein than in fish fed the diet containing 420–450 g/kg crude protein at two dietary lipid levels. The feed intake and weight gain were higher in fish fed the diet containing 484 g/kg crude protein and 115 g/kg crude lipid than in fish fed the diet containing 478 g/kg crude protein and 77 g/kg crude lipid. This study indicated that the suitable dietary protein and lipid levels for largemouth bass are 480–510 g/kg and 120 g/kg, respectively.     

患白云病加洲鲈的同工酶分析

采用垂直平板聚丙烯酰胺凝胶电泳技术,对感染致病菌后的加洲鲈5种组织中5种同工酶系统的酶谱表型及活性进行分析。证实在5种酶的4种组织中出现明显的紊乱现象,表明病鱼的病理机制与代谢异常有关,其特异性变化可以作为疾病早期诊断及病理分析的生化辅助指标。     

Practical Comparison of Commercial Starter Diets for Feed Training Largemouth Bass Fingerlings

We compared performance (growth, survival, and condition) of northern largemouth bass Micropterus salmoides salmoides fingerlings fed one of three commercial starter feeds: Otohime Marine Weaning (OMW; Marubeni Nisshin Feed), Bio-Oregon BiVita Fry (BVF; Bio-Oregon), and Purina Aquamax Starter (PAS; PMI Nutrition International LLC). Nine 833-L circular tanks, connected in parallel to a recirculation system, were stocked with 465 fish (1.4 kg), each to provide a rearing density of 1.1 fish/L. Water temperature was maintained at 27°C, and photoperiod was 15:9 h light:dark. Feed sizes (1.5–1.6 mm) were comparable and had similar protein composition (48%–50%). Feed was dispensed by vibratory feeders at a rate of 5% BWPD from 0730 h to 2130 h every 0.5 h for a total of 29 feedings per day (trial duration = 22 days). Overall performance was best for fish fed OMW, followed by BVF, then PAS. The PAS feed resulted in significantly lower growth, survival, and condition factor (P ≤ 0.05). Though not statistically significant, the BVF feed resulted in lower growth, condition factor, and survival than OMW (P > 0.05). Performance measures were positively correlated with crude fat and negatively correlated with protein to energy ratio of feeds. The OMW or BVF diets may be more appropriate for intensive culture when the artificial feed is the sole food supply, while the PAS diet may be more suitable for extensive culture as a supplemental food source.     

Evaluation of Four Commercial Grower Diets for Production of Largemouth Bass

We compared performance (growth, survival, condition, and health indices) of largemouth bass, Micropterus salmoides, fingerlings (10.3 g [SE ± 0.5 g] and 92 mm [SE ± 1 mm] total length) fed one of four commercial grower feeds: Purina Aquamax Grower 400 (PAG; PMI Nutrition International LLC), Bio-Oregon BioDiet Grower (BDG; Bio-Oregon), Silver Cup Steelhead (SCS; Silver Cup), and Richloam Bass Fry Diet 12 (RBF; Silver Cup). Sixteen 833-L circular tanks, connected in parallel to a recirculation system, were initially stocked with 2.25 kg of fish (219 fish each, 0.32 fish/L) with four replicates per feed treatment. Water temperature was 25°C, and photoperiod was 15 h light:9 h dark. Feed sizes (2.4–3.0 mm) were comparable, and protein compositions ranged from 49% to 61%. Fish were fed to satiation multiple times per day (trial duration = 100 days). Overall, performance was best for fish fed RBF, followed by PAG and BDG, and then SCS. The SCS feed resulted in significantly lower growth and survival (P ≤ 0.05). The PAG and BDG feeds resulted in significantly lower growth than the RBF feed (P ≤ 0.05); however, survival did not differ (P > 0.05). Performance measures were positively correlated with protein, and protein to energy ratio and negatively correlated with fat and carbohydrate compositions. The four commercial grower feeds resulted in highly varied growth, survival, and health indices, and this research should facilitate feed choice for various largemouth bass production strategies as well as increase contribution of stocked fish.     

Evaluation of Plant and Animal Source Proteins for Replacement of Fish Meal in Practical Diets for the Largemouth Bass Micropterus salmoides

Two feeding trials were conducted with juvenile largemouth bass Micropterus salmoides to evaluate alternative plant and animal source proteins for their ability to replace fish meal in practical diets. The first trial was designed to identify the most promising candidates. The second trial was conducted to evaluate how much of the fish meal could be replaced by those candidates. In Study 1, feed‐trained largemouth bass (3.1 ± 0.7 g) were randomly stocked into 18114‐L glass aquaria at 25 fish per aquarium. Fish were fed one of six experimental diets, each containing approximately 38% crude protein and 10% crude lipid, to apparent satiation twice daily. The control diet (CTL) contained 30% fish meal and 34.5% soybean meal. Diets 2–6 each contained 15% fish meal and at least 34.5% soybean meal with the remainder of the protein made up of either meat and bone meal (MBM), soybean meal (SBM), poultry by‐product meal (PBM), a 50150 mixture of blood meal and corn gluten meal (BM/CG), or 50150 mixture of hydrolyzed feather meal and soybean meal (FMISBM). There were three replicate aquaria per dietary treatment. After 12 wk, there was no significant difference (P > 0.05) among treatments in survival which averaged 92% overall. Only fish fed the PBM or BM/CG diets had average individual weights and feed conversion efficiencies that were not significantly different (P > 0.05) from the control diet (CTL). In Study 2, the formulation of the control diet (CTL) remained the same. Based on their performance in the first trial, PBM and BM/CG were chosen to now replace 75 or 100% of the fish meal. Fish were stocked at an average weight of 6.9 ± 1.7 g. After 11 wk, fish fed diets containing the BM/CG mixture at both levels were significantly smaller (P 5 0.05) than fish fed other diets and at 100% replacement survival was reduced. Fish fed diets containing poultry meal as the primary protein source performed as well as those fed the control diet (CTL). It appears that PBM can completely replace fish meal in diets for juvenile largemouth bass without adverse effects on growth, feed efficiency, or body composition.     

Evaluation of Reduced Fish Meal Diets for Second Year Growout of the Largemouth Bass,Micropterus salmoides

Development of efficient cost‐effective diets is a critical component in the refinement of production technologies for the largemouth bass, Micropterus salmoides (LMB). One of the first steps in reducing feed costs can be to decrease the amount of fish meal in the diet. The objective of this study was to evaluate reduced levels of fish meal, and a least‐cost formulation diet, for second year growout of LMB under practical pond conditions. Twelve 0.04‐ha ponds were stocked with juvenile LMB (210.1 ± 3.3 g) at a stocking density of 8650 fish/ha (350 fish/pond). Each pond was randomly assigned one of the four dietary treatments with three replicate ponds per treatment. The three experimental diets contained varying levels of fish meal. Diets FM‐45, FM‐24, and FM‐8 contained 45, 23.5, and 8% fish meal, respectively. In diets FM‐24 and FM‐8, fish meal was replaced by varying levels of poultry by‐product meal, soybean meal, and blood meal. The fourth diet was a commercial salmonid diet widely used as a LMB growout feed (Nelson and Sons, Inc., Silvercup ^TM , Steelhead, Murray, UT, USA). This diet served as a commercial control (CC) and contained 46% crude protein. The experimental diets were formulated to be isonitrogenous and isocaloric with the CC diet and were fed once daily to apparent satiation for 180 d. At harvest, there were no significant differences between treatments ( P > 0.05 ) in terms of survival, which averaged 95% overall. Mean weights of fish fed the three experimental diets FM‐45, FM‐24 and FM‐8 were not significantly different ( P > 0.05 ) and averaged 518, 546, and 529 g, respectively, but were all significantly greater ( P≤ 0.05 ) than those fed the CC (488 g). Feed conversion ratio (FCR) of fish fed the FM‐45 and FM‐8 diets (1.43 and 1.46, respectively) was significantly greater ( P≤ 0.05 ) than those fed the FM‐24 diet (1.34). The FCR of fish fed the CC diet (1.39) was not significantly different ( P > 0.05 ) from fish fed other diets. Feed cost per unit of weight gain ($US/kg) was significantly lower ( P≤ 0.05 ) in fish fed the FM‐24 and FM‐8 diets ($0.73 and $0.72/kg, respectively) than in fish fed other diets. Feed cost per unit gain of fish fed the FM‐45 diet ($0.83/kg) was significantly lower ( P≤ 0.05 ) than those fed the CC diet ($1.04/kg). There were no significant differences ( P > 0.05 ) in dress‐out percentages or proximate composition among fish fed the four diets. This study indicates that fish meal levels in feeds used for the second year growout of LMB can be reduced to ≥ 8% of the formulation without reducing survival or growth and without negatively impacting body composition.     

Dietary synbiotics improved the growth,feed utilization and intestinal structure of largemouth bass (Micropterus salmoides) juvenile

This study investigated the effect of dietary synbiotics on the growth, feed utilization and intestinal histology of largemouth bass (Micropterus salmoides). A commercial synbiotic product containing dried powder of yeast, Bacillus subtilis and mannan oligosaccharides was supplemented in basal diet with 0 g/kg (control), 1.0, 2.0, 4.0 and 6.0 g/kg, respectively, and then, the five diets were fed to largemouth bass with body weight of 4.5 ± 0.1 g for 8 weeks. The results showed that the supplementation of 2.0, 4.0 and 6.0 g/kg synbiotics increased weight gain by 20.6%, 17.7% and 11.8% (p < .05) and decreased feed conversion ratio by 0.20, 0.18 and 0.12 (p < .05), respectively, when compared to the control. The protein retention, lipid retention, apparent digestibility coefficient of dry matter and crude protein, and the intestinal villus height and width of 2.0 and 4.0 g/kg synbiotic groups were significantly higher than those of the control (p < .05). The intestinal protease activity and serum lysozyme activity were increased by the addition of 2.0 and 4.0 g/kg synbiotics (p < .05). In conclusion, dietary synbiotics improved the growth, feed utilization and intestinal structure of juvenile largemouth bass, and the recommended inclusion level was 2.0–4.0 g/kg.     

An evaluation of replacing fish meal with fermented soybean meal in the diets of largemouth bass (Micropterus salmoides): Growth,nutrition utilization and intestinal histology

A 56‐day feeding trial was conducted to investigate the effects of replacing fish meal (FM) with soybean meal (SBM) and fermented soybean meal (FSBM) on growth performance, nutrition utilization and intestinal histology of largemouth bass. The basal diet contained 350 g/kg FM (control), and then, FM was replaced with SBM or FSBM of 15%, 30%, 45% and 60% respectively. The results showed that the specific growth rate of fish fed FSBM‐60, SBM‐45 and SBM‐60 diets significantly decreased, and the feed conversion ratio of SBM‐30, SBM‐45, SBM‐60, FSBM‐45 and FSBM‐60 groups increased when compared to the control group (p < .05). The apparent digestibility coefficients of dry matter and crude protein of SBM‐45, SBM‐60 and FSBM‐60 groups were significantly lower than those of the control group (p < .05), and the substitution of FM with SBM and FSBM (45% and 60%) significantly reduced the protein retention (p < .05). Serum total protein contents of SBM‐60 and FSBM‐60 groups and serum cholesterol contents of SBM‐45, SBM‐60 and FSBM‐60 groups were significantly lower than those of the control group (p < .05). The SBM‐30 and SBM‐60 groups showed significantly higher alanine aminotransferase activity than the control group (p < .05). The intestinal histology analysis resulted that the villus length of the SBM‐60 group and the villus width of the SBM‐45, SBM‐60 and FSBM‐60 groups decreased when compared to the control (p < .05). In conclusion, FSBM could replace 30% FM in diet of largemouth bass containing 350 g/kg FM, while the substitution level of FM with SBM was only 15%.     

Effects of season, maturity, and sex on lipid class dynamics in largemouth bass (Micropterus salmoides Lacepede)

Abstract Factors that can influence changes in lipid class concentrations in specific tissues have not been reported for largemouth bass Micropterus salmoides. We investigated patterns of lipid composition by measuring seasonal levels of total lipid and major lipid classes in the muscle and liver tissues of juvenile and adult largemouth bass and gonad tissue of adults. Fish were collected in December, February, April and July to correspond with key stages of the sexual cycle. Total lipid concentrations were substantially greater in hepatic (32.8 [female] to 56.6 [male] mg. g^?1) and gonadal tissues (34.4 [F] to 204.0 [M] mg. g^?1) than in muscle (7. 5 [F] to 11.4 [M] mg. g^?1). Muscle lipid concentrations in juveniles were significantly higher (10.9 [F] and 11.4 [M] mg. g^?1) in summer than in winter in adult muscle tissue (8.6 [F] and 9.4 [MI mg. g^?1). A 44% increase in ovary lipid was observed from preparatory to prespawn stages, followed by a 78% decline after the spawn. Additionally, seasonal hepatic lipid concentrations were substantially higher in juveniles. Concentrations of lipid classes (free cholesterol [C], triacylglycerol [TAG], free-fatty acids [FFA], esterified cholesterol [CE] and phospholipid [PL]) of all tissue types varied significantly among season, sex, and maturity categories. Changes with all lipid classes in the ovary coincided with those occurring in total ovarian lipid. Mobilization and transport of TAG and PL from the liver to the ovary appeared to occur during gametogenesis. All class concentrations in juveniles were invariably higher in liver than in muscle, but seasonally variable among hepatic and gonad tissues of adults. Juvenile males showed slightly greater hepatic C concentrations than other groups. Muscle and hepatic C were generally higher in juveniles.     

Persistence of Florida largemouth bass alleles in a northern Arkansas population of largemouth bass, Micropterus salmoides Lacèpéde

Abstract– Lake Ashbaugh, located in northeast Arkansas, was constructed in 1981, and initially stocked with Florida largemouth bass followed by supplemental stockings of northern largemouth bass. Allele frequencies of three discriminant allozyme loci (sAAT-B, sIDH-B, sMDH-B) between Florida and northern largemouth bass were determined for 414 largemouth bass collected between 1994 and 1996. F_x bass dominated our sample, with 62.3% possessing Florida largemouth bass alleles. A high incidence of Hardy-Weinberg disequilibrium was observed, indicative of genetic change within the population. No significant differences were identified for frequency of age classes, relative weight, and length at age between the northern, F₁ and F_x phenotypes. Despite being located north of what is generally considered suitable for stocking Florida largemouth bass, it was demonstrated that temperature is not selective at present against bass possessing Florida largemouth bass alleles. However, caution should prevail when introducing non-native stock into native gene complexes, as introduced genes persist through many generations.     

Replacement of Fishmeal by a Mixture of Soybean Meal and Chlorella Meal in Practical Diets for Juvenile Crucian Carp,Carassius auratus

A growth trial was conducted to evaluate the effect of a mixture of soybean meal and Chlorella meal (SCM) as a dietary fishmeal (FM) substitute on growth performance, apparent digestibility coefficients (ADCs), digestive enzymatic activities, and histology of juvenile crucian carp, Carassius auratus. Five isonitrogenous and isoenergetic diets were formulated to replace 0 (SCM0), 25 (SCM25), 50 (SCM50), 75 (SCM75), and 100% (SCM100) of protein from FM with SCM, respectively. The diets were fed to triplicate groups of juvenile crucian carp for 6 wk. Weight gain, specific growth rate, feed intake, protein efficiency ratio, and intestinal digestive enzymatic activities (amylase, trypsin, and lipase) tended to decline with increasing FM replacement levels (P > 0.05). Dietary SCM substitution significantly influenced dry matter content in muscle, and crude protein and lipid contents in liver (P < 0.05). ADCs for dry matter, protein, lipid, energy, and most amino acids showed no significant differences between the control and SCM25 group, but tended to decline with replacement levels over 25%. Higher SCM substitution (50–100%) caused karyopyknosis and necrosis in liver, but intestinal histology did not show noticeable pathological changes. The present study indicated that FM could be replaced by 25% of SCM, without significant adverse growth performance, feed utilization, and histology of crucian carp.     

Arginine requirement and effect of arginine intake on immunity in largemouth bass,Micropterus salmoides

An 8‐week feeding test was conducted to quantify the dietary arginine requirement of juvenile largemouth bass (LMB) (25 ± 0.4 g). Six isonitrogenous and isolipidic (459 g crude protein and 122 g crude lipid kg^?1 dry diet) diets were formulated to contain graded levels of arginine (17.0–30.1 g kg^?1 dry diet). Zein‐coated crystalline amino acid mixtures were supplemented to simulate, except for arginine, the amino acid profile of the muscle protein of LMB. Each diet was randomly assigned to quadruplicate tanks of 35 fish reared in a flow‐through system. Fish were fed to apparent satiation twice daily. Weight gain (WG) was significantly affected by dietary arginine level. Nitrogen retention was significantly lower in fish fed D17.0. Arginine retention significantly decreased with dietary arginine increased. Threonine, leucine and lysine concentrations in whole body were significantly affected by dietary arginine level. Serum lysozyme activity, serum protein and respiratory burst of head kidney leucocytes were significantly affected, while complement activity (CH₅₀) showed no difference among treatments. Based on broken‐line analysis for WG against dietary digestible arginine level, the arginine requirement of LMB was 19.1 g kg^?1 of dry diet (41.6 g kg^?1 of crude protein).     

Physical activity and behavior of a centrarchid fish, Micropterus salmoides (Lacépède), during spawning

Abstract – The spawning behavior of male and female largemouth bass Micropterus salmoides (Lacépède) was studied in central Illinois during the spring of 1998 to examine patterns of muscular activity associated with different spawning related behaviors and to evaluate whether electromyogram (EMG i ) telemetry could be used to detect spawning activity. Fish were implanted with EMG i transmitters (8 females, 16 males) on April 7, prior to the initiation of spawning, and were released in four 0.10-ha earthen research ponds. Continuous EMG i records, underwater videography and additional visual observations for one pair of EMG i tagged fish were collected throughout the entire spawning event, allowing us to quantify behavioral correlates of physical activity. Male EMG i activity patterns were only correlated with female patterns during courting and periods of male aggression toward the female. Overall, EMG i activity was highest for the female during shuddering (gamete deposition), whereas male EMG i activity was similarly high during periods of nest excavation, shuddering and post-spawn parental care activities. During spawning, female EMG i activity was positively correlated to shuddering. Average daily EMG i activities for females peaked on the day of spawning. As a result of their engagement in parental care activities, male activity continued to rise even after spawning was completed. EMG i telemetry appears to be a useful technique for monitoring the reproductive activity of largemouth bass, especially in areas of high cover or turbid water or during low light conditions. This technology permitted us to quantify and contrast the activity patterns associated with different spawning related activities, information that will be required to construct accurate, gender-specific bioenergetics models for this species.     

Replacing fish meal with a blend of poultry by‐product meal and feather meal in diets for giant croaker (Nibea japonica)

An 8‐week feeding trial was conducted to evaluate the potential of replacing fish meal with poultry by‐product meal (PBM) and feather meal (FEM) in giant croaker (Nibea japonica) diet. The control diet (C) contained 400 g/kg fish meal, and 20%, 40%, 60% and 80% of the fish meal in diet C was replaced by a blend of PBM and FEM (PBM: FEM = 7:3) in diets B20, B40, B60 and B80, respectively. The weight gain and feed intake of fish fed diet C did not differ from those of fish fed diets B20 and B40 (p > .05), but were higher than those of fish fed diets B60 and B80 (p < .05). Phosphorus retention efficiency was lower in fish fed diets C, B20 and B40 than in fish fed diets R60 and R80 (p < .05). No significant differences were found in feed conversion ratio, nitrogen retention efficiency, condition factor, hepatosomatic index, body composition and nitrogen waste among the treatments (p > .05). Ratio of fish meal consumption to fish production linearly declined with the decrease in dietary fish meal level. This study indicates that dietary fish meal for giant croaker could be reduced to 240 g/kg by inclusion of the blend of PBM and FEM.     

Effects of fish meal replaced by fermented soybean meal on growth performance,intestinal histology and microbiota of largemouth bass (Micropterus salmoides)

This study was conducted to investigate the effects of replacing fish meal (FM) with fermented soybean meal (FSM) and soybean meal (SM) on growth performance, intestinal histology and microbiota of largemouth bass (Micropterus salmoides). The basal diet contained 350 g/kg FM (CON), and then, FM was replaced with SM and FSM at the ratios of 30% and 60% (SM‐30, SM‐60, FSM‐30 and FSM‐60), respectively. The largemouth bass (4.43 ± 0.13 g) were fed for 8 weeks. The results showed that weight gain of fish fed with FSM‐60 and SM‐60 diets was significantly lower, and feed conversion ratio of SM‐30, SM‐60 and FSM‐60 groups was significantly higher than the CON group (p < .05). The intestinal villus height of SM‐60 group and the villus width of SM‐60 and FSM‐60 group were significantly lower than the CON group (p < .05). The 30% FM replacement by SM and FSM significantly increased the abundance of Cetobacterium and Mycoplasma, respectively (p < .05). In conclusion, FSM could replace 30% FM in diet without negative impacts on the growth performance of largemouth bass, while the SM should be controlled below 30%.     

Production performance of largemouth bass Micropterus salmoides and water quality variation in monoculture,polyculture and integrated culture

A 74‐day experiment was conducted to evaluate the production performance and water quality variation in three types of farming system for largemouth bass Micropterus salmoides. The tested aquaculture models included monoculture of largemouth bass (MC), polyculture of largemouth bass, gibel carp Carassius auratus gibelio and silver carp Hypophthalmichthys molitrix (PC), and integrated culture of largemouth bass, gibel carp, silver carp and freshwater pearl mussel Hyriopsis cumingii (IC). The ratio of largemouth bass, gibel carp and silver carp was 30:2:1 in the PC model, and the ratio of largemouth bass, gibel carp, silver carp and mussel was 30:2:1:5 in the IC model. The largemouth bass were fed with formulated feed twice daily. No significant differences were found in weight gain and yield of largemouth bass, total fish yield, nitrogen (N) and phosphorus (P) utilization efficiencies, N and P wastes, pH, nitrite, nitrate, reactive phosphate, total nitrogen, total phosphorus, total organic carbon, chemical oxygen demand, 5‐day biochemical oxygen demand, chlorophyll a, primary productivity among the MC, PC and IC models. The ammonia was lower, while the dissolved oxygen was higher in the PC tanks than in the MC tanks. These results suggest that the environment situation was better in the PC tanks relative to that in the MC tanks. The present study reveals that the PC model should be a way to optimize the aquaculture model for commercial largemouth bass farming.     

Replacement of fishmeal by chicken plasma powder in diets for largemouth bass (Micropterus salmoides): Effects on growth performance,feed utilization and health status

The present study was conducted to explore the effects of graded replacing fishmeal (0, 50, 100 and 150 g/kg) with chicken plasma powder in diets for largemouth bass, and each diet was fed to triplicate groups of fish (initial weight: 49.50 ± 0.07 g) twice daily. Results showed that specific growth rate was not remarkably reduced until 150 g/kg fishmeal being replaced. Meanwhile, the inclusion of chicken plasma powder led to a significant decrease in feed intake, and the replacement of 150 g/kg fishmeal significantly decreased the apparent digestibility coefficient of protein and essential amino acids, which may account for the lowered protein retention rate and decreased crude protein content of liver and whole body composition. Moreover, the replacement of 150 g/kg fishmeal resulted in a significantly reduced activity of lysozyme, classical complement pathway and respiratory burst, and meanwhile, the red blood cell count and haemoglobin content were also significantly reduced, indicating the impaired health status of fish with high inclusion of chicken plasma powder. In above, approximately 50–100 g/kg fishmeal could be replaced by chicken plasma powder in the diets for largemouth bass.     

国产鱼粉替代进口鱼粉饲养牙鲆试验报告

以国产鱼粉和进口鱼粉 ,分别设计成两种等蛋白、等能量的干粉料 ,与小杂鱼按一定的比例混合制成软颗粒饲料 ,投喂南方池养牙鲆进行饲养对比试验 ,经过 2 0 4天的饲养 ,投喂A料、B料的尾相对增重率分别为 2 4 0 1 %、 2 4 83% ,尾平均日增重分别为 2 .1 8g、1 .4 6 g ;饲料系数分别为 2 .0 5、 2 .6 0 ,牙鲆增重 1kg所需饲料成本分别为 9.6 6 元和 1 3.6 5 元。牙鲆鱼肌肉粗蛋白、粗脂肪含量差异不显著 (P >0 .0 5 ) ,5种鲜味氨基酸的含量很接近     

Maximum yield approximation and size distribution patterns of stocker size largemouth bass,Micropterus salmoides reared in a semi‐closed indoor system

The main objectives of this study were to approximate the maximum yield and evaluate size dispersion of stocker size largemouth bass, Micropterus salmoides reared in a semi‐closed recirculating system for 60 days. Fingerlings with an average body weight of 36.7 g were utilized for the study. An experimental system consisting of 18 square plastic tanks (165 L) equipped with a radial flow settler, a sump, a moving bed filter, a centrifugal pump, a rapid sand filter, a down‐flow oxygen saturator and a UV sterilizer was utilized for the trial. The system was operated semi‐closed, accounting for a daily exchange rate of 30–50% of total system water volume. Experimental stocking densities were 4.5, 9.1, 18.8, 36.5, 54.6 and 73 kg m^?3 with three replicates per treatment. At the end of the experimental trial, largemouth bass showed acceptable feed conversion (1.00–1.48), specific growth rate (1.16–1.45% day^?1) and survival rate (81.8–96.6%) in all treatments, displaying the highest performance at an initial stocking density range of 18–36 kg m^?3. Based on a piecewise regression model with breakpoint analysis, maximum yield of largemouth bass fingerlings should not exceed 70 kg m^?3. As stocking density increased, relatively more underweight fingerlings were produced with a higher uniformity of fatness.