Effects of Methyltestosterone on Largemouth Bass,Micropterus salmoides

The effectiveness of 30 or 50 mg of 17 ∝-methyltestosterone/kg diet for periods of 4, 6, or 10 weeks starting when the fish were 25 mm TL for sex-reversal of juvenile largemouth bass, Micropterus salmoides, was evaluated. Fish were subsequently dissected to determine gonadal morphology and histology. Five of the six trials produced significantly (P < 0.05) altered sex ratios based on gonadal differentiation. Data with two-year-old largemouth bass indicated a low number of spermiating individuals among methyltestosterone- treated fish.     

Feasibility of Pond Production of Largemouth Bass,Micropterus salmoides,for a Filet Market

The effects of stocking density on food‐size largemouth bass (LMB), Micropterus salmoides, production (>0.5 kg) were evaluated in a 2‐yr study by stocking LMB fingerlings (mean weight = 57 g/fish) in 0.1‐ha earthen ponds at rates of 6175, 12,350, or 18,525 fish/ha. Gross yields increased from 3989 to 9096 kg/ha as stocking density increased. No significant differences were observed in survival rates (range of 65–74%) due to density. Maximum feed consumption occurred at water temperatures of 27–30 C. Feed conversion ratio (FCR) and mean harvest weight were significantly different (P < 0.05) among densities, with the lowest FCR and the lowest mean weight found at the highest density (18,525 fish/ha). At harvest, LMB were considered to be in good condition with relative weight (W_r) values of 123–124. Dressout yield percentages were 61–62% for whole‐dressed LMB and 34–35% for shank filets. LMB grew well and reached a size adequate for targeted shank filet sizes. However, the production costs of $7.26–$9.34/kg mean that LMB production for a filet market is unlikely to be feasible. Research to lower LMB fingerling and feed costs and improved FCR would contribute to improved economic feasibility.     

Triploidy Induction in Largemouth Bass,Micropterus salmoides

Triploid largemouth bass, Micropterus salmoides, were produced by using hydrostatic pressure treatments five minutes after fertilization. Treatments ranged from 4,000 p.s.i. for 3 minutes to 8,000 p.s.i. for 1 minute was best, yielding 100% triploids and a relatively low mortality.     

周期性“饥饿-再投喂”对大口黑鲈幼鱼补偿生长的影响

在水温(26.5±1.2)℃下,将体质量(45.70±0.56)g的大口黑鲈Micropterus salmoides幼鱼分为4组,饲养在采光大棚内的30m2水泥池中,每池40尾,D0组每天饱食投喂2次,D1、D2、D3组分别投喂6d、5d、4d,饥饿1d、2d、3d,持续8周,每组3个重复池塘,研究周期性“饥饿-再投喂”对大口黑鲈幼鱼补偿生长的影响。结果发现,随着每周饥饿天数的增加,大口黑鲈的末体质量和增重率均不同程度下降,但D1组与D0组无显著差异(P>0.05)。大口黑鲈的日摄食量随饥饿时间的增加而显著提高(P<0.05),但各组间无显著差异(P>0.05)。D1组的饲料利用效率和蛋白质效率与D0组无显著差异(P<0.05);而D2和D3组显著低于D0组(P<0.05)。试验结束时,鱼体粗蛋白和粗脂肪含量随饥饿时间增加而下降。D3组鱼的胃和肠道蛋白酶活性显著低于D0组(P<0.05);D1组的胃和肠道脂肪酶活性较高;D1和D2组胃淀粉酶活性较高,肠道淀粉酶活性则随着饥饿时间增加显著上升(P<0.05)。饥饿使大口黑鲈血清甘油三酯和总胆固醇含量降低,血清谷草转氨酶和谷丙转氨酶活性增加。血清生长激素水平随着饥饿时间增加而上升,类胰岛素生长因子-Ⅰ水平则下降(P<0.05)。结果表明:每周投喂6d饥饿1d的大口黑鲈饲料转化效率较高,实现了完全补偿生长,可供集约化养殖的科学投喂参考。     

Effects of Graded Levels of Carbohydrate on Growth and Survival of Largemouth Bass, Micropterus salmoides

Excessive carbohydrates (CHO) in diets for largemouth bass (LMB), Micropterus salmoides, are suspected of accumulating glycogen in hepatocytes, which may result in liver dysfunction. This study evaluated the effect of graded levels of dietary CHO on growth, survival, and liver histology of LMB. One hundred feed‐trained advanced fingerling LMB (128.5 ± 21.5 g) were stocked into each of nine 3400 ‐ L polyethylene tanks. Tanks were randomly assigned one of three experimental diets containing different CHO levels (13, 19, or 25% of diet). The extruded diets were approximately isonitrogenous (42% crude protein) and isocaloric (3 kcal/g energy). There were three replicate tanks per dietary treatment. Bass were fed to apparent satiation twice daily for 148 d. Survival was significantly higher (P ≤ 0.05) for fish fed the 13 and 19% CHO diets (89 and 90%, respectively) compared to those fed the 25% CHO diets (82%). Average harvest weight of fish fed the 13% CHO diet (380 g) was significantly greater (P ≤ 0.05) than for fish fed other diets. Average harvest weight of fish fed the 19% CHO diet (347 g) was significantly greater (P ≤ 0.05) than for fish fed the 25% CHO diet (310 g). Specific growth rates (%/d) were significantly higher (P ≤ 0.05) in fish fed the 13 and 19% CHO diets than in fish fed 25% CHO diet. Feed conversion ratios for fish fed the 13 and 19% CHO diets (2.3 and 2.4, respectively) were both significantly lower (P ≤ 0.05) than in fish fed the 25% CHO diet (3.6). There were no significant differences (P > 0.05) in condition factor, protein efficiency ratio, hepatosomatic index, or liver glycogen concentration among fish fed the different experimental diets. Overall, mean blood glucose levels in fish fed the 13 and 19% CHO diets (61.0 and 71.2 mg/dL, respectively) were significantly lower (P ≤ 0.05) than in fish fed the 25% CHO diet (87 mg/dL). Histopathological examination of livers from fish fed the three diets was used to score the degree of vacuolization of hepatic tissues (0 = normal, 1 = slight, 2 = mild, 3 = moderate, and 4 = severe). Regression of vacuolization scores on dietary CHO levels was statistically significant (P ≤ 0.05) and indicated a direct positive relationship between liver vacuolization and dietary CHO level (R² = 0.57). These data indicate that LMB grow faster and use feeds more efficiently when CHO are maintained at <20% of diet. CHO levels >20% negatively impacted liver histology, but a liver tissue analyses did not document glycogen accumulation.     

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.     

加州鲈池塘立体混养技术试验

以加州鲈为主养品种,适当混养河蟹、黄颡鱼、青虾,并栽种水草、投放螺蛳等,进行池塘立体混养试验,与单养加州鲈作对比.试验结果表明,混养塘的饵料资源得到多层次利用,与对照塘相比饵料系数下降12.8%,为3.4;平均成本下降6.6%,为7 204.6元/667m2;平均利润提高109.6%,为3 868.2元/667m2.对立体混养技术中的放养准备、水草栽培、水质管理、投饵管理、病害防治等内容作了重点介绍.     

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。     

Effect of Water Temperature on Growth, Survival, and Biochemical Composition of Largemouth Bass Micropterus salmoides

The effects of water temperature on growth rate, survival, and biochemical composition of juvenile largemouth bass Micropterus salmoides were evaluated under controlled conditions in tanks for 12 wk. Feed-trained juvenile largemouth (9.1 ± 1.9 g) were stocked into nine 3,610-L polyethylene tanks inside a greenhouse structure at 140 fish/m³ (500 fish/tank). Three treatment temperatures were evaluated (20, 26, and 32 C) with three replicates per treatment. Bass were fed to apparent satiation twice daily using a commercially available floating salmonid diet (45% crude protein and 16% lipid). After 97 d bass grown at 26 and 32 C had significantly higher ( P < 0.05) average weights, SGR, condition factor (K), and production rates (kg/m³) than those in the 20 C treatment. Bass in the 26 C treatment had significantly lower ( P 0.05) FCR and higher percent protein deposit (PPD) than bass raised at 20 and 32 C, which were not significantly different ( P >0.05). There were no significant differences ( P >0.05) in survival among treatments which averaged 97%, overall. Bass raised at 32 C had higher ( P 0.05) lipid levels in the liver than other treatments. Whole body amino acid concentrations were not significantly impacted ( P >0.05) by culture temperature. Largemouth bass raised at 26 C had significantly lower ( P 0.05) levels of stearic acid (18:0) and significantly higher ( P 0.05) levels of arachidonic acid (20:4 n-6) than bass raised at 20 or 32 C. Bass raised at 32 C had significantly higher ( P 0.05) levels of Linoleic acid (18:2 n-6), total saturates, and dienes than bass raised at 26 or 20 C. These data indicate that growth and feed conversion efficiency are reduced at 20 C. Growth is similar at 26 and 32 C, but feed and dietary protein are more efficiently utilized at 26 C.     

Development of First-Feeding Protocols for Indoor Larviculture of Largemouth Bass (Micropterus salmoides)

Largemouth bass (LMB) Micropterus salmoides fry do not accept prepared diets at first feeding. Fry are initially reared in fertilized ponds on natural live foods until large enough to be feed trained. Unpredictable weather patterns and depletion of natural forages can affect nursery pond survival. A series of experiments was conducted to investigate the use of Artemia nauplii prepared diets and optimal feeding schedules to raise LMB fry from first feeding through habituation to a commercial dry diet. In Studies 1, 2, and 3, swim-up fry were transferred to a recirculating system and stocked into either 3-L (Studies 1 and 2) or 10-L (Study 3) acrylic aquaria. Study 1 screened candidate diets to evaluate whether LMB fry could be transitioned directly to prepared diets or if they required live foods. In Study 2 the optimum duration for feeding live Artemia (1, 2, or 3 weeks) and the appropriate size of commercial diets (<200 or 200–360 μm) were evaluated. Study 3 was designed to identify the best transitional feed. Results from Study 1 indicate that fry fed Otohime-A (<200 μm) and decapsulated Artemia cysts performed better than those fed other diets tested. However, survivals were low (6%–8%) indicating a need for live feed initially. In Trial 2, fry fed live Artemia nauplii for two weeks and then transitioned to a 200–360 μm diet (Otohime-B) performed better than other diet combinations tested. In Study 3, survival was significantly higher in treatments using decapsulated Artemia cysts or Otohime-B as transitional diets between initial live Artemia feeding and trout starter. These data indicate that LMB fry can be successfully raised from first feeding to fully habituated to a commercial trout starter by feeding live Artemia nauplii for two weeks, followed by a gradual transition to either decapsulated Artemia cysts or Otohime-B for one week, then gradually transitioning to trout starter. Surviving fish were easily transitioned to commercial floating feed (Study 4). This protocol yielded survival rates of approximately 70% and may improve the reliability of LMB fingerling production by eliminating the outdoor nursery pond phase.     

大口黑鲈选育效果的初步分析

通过选择培育获得大口黑鲈群体选育子三代,对其选育效果进行初步评价。实验数据分析表明,经过三代的选育,大口黑鲈2个选育组在体长、体高和体重上均大于对照组,且差异极显著（P〈0.01）,选育组1和2的日增重率分别比对照组提高了25.32%和23.42%,平均每代的选育效应分别为8.44%和7.81%,而体重变异系数分别是26.8%和20.2%,相比对照组分别降低了9.8%和21.1%。试验结果表明,大口黑鲈的选育效果明显,F3代的生长性能有了显著性的提高,个体之间的生长速度更加趋于一致,同时,F3代仍具有较大的选育潜力,可继续对其进行选育。该研究为进一步通过选择育种培育大口黑鲈优良品种（系）奠定了基础。     

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.     

Effect of Stocking Density on Growth and Water Quality for Largemouth Bass Micropterus salmoides Growout in Ponds

Juvenile largemouth bass Micropterus salmoides , trained to accept artificial diets, were stocked into six 0.04-ha ponds at stocking densities of either 6,175 or 12,350 fish/ha. Fish were fed a floating custom-formulated diet, containing 44% protein, once daily to satiation for 12 mo (May 1994–May 1995). At final harvest, the total yield of fish was significantly greater (P < 0.05) and feed conversion ratio (FCR) was significantly lower, for bass stocked at the higher density (4,598 kg/ha and 2.3, respectively) than when stocked at the lower density (2,354 kg/ha and 3.3, respectively). There was no significant difference (P > 0.05) in average weight, length, or survival of bass stocked at the two densities. Averaged over the study period, there were no significant differences (P > 0.05) in total ammonia-nitrogen (TAN), nitrite-nitrogen, or un-ionized ammonia concentrations in ponds in which bass were stocked at the two densities. These data indicate that largemouth bass of the size used in this study are amenable to pond culture at densities of at least 12,350 fish/ha and that higher stocking densities may be possible.     

Response of Largemouth Bass Micropterus salmoides to Dietary Supplementation of Lysine, Methionine, and Highly Unsaturated Fatty Acids

Abstract.— A 12-wk feeding trial was conducted in aquaria with juvenile (36.0 ± 1.2 g) largemouth bass Microptents salmoides to examine the effects of dietary supplementation of methionine, lysine, and long-chain polyunsaturated fatty acids (PUFA) on growth, feed conversion and body composition. Diets were formulated to increase dietary concentrations of methionine. lysine, and PUFAs to match levels found in whole body samples of largemouth bass. The control diet was formulated similar to diets previously tested for largemouth bass. Diets 2 and 3 were similar to the control diet hut were supplemented with 2% lysine and 1% methionine, respectively. Diet 4 was formulated to increase PUFAs, especially docosahexaenoic acid (DHA) (22:6n-3), by replacing menhaden fish oil with squid oil. Fish were fed all they would consume in 10 min, twice daily. At harvest, there were no statistically significant differences ( P > 0.05) in average individual weight or specific growth rate (SGR) among fish fed the four diets. The feed conversion ratio (FCR) of largemouth bass fed the diet supplemented with methionine (1.7) was significantly lower ( P ≤ 0.05) than fish fed the control diet (2.5). Fish fed the diet high in PUFA had significantly lower ( P ≤ 0.05) whole body lipid levels and significantly higher ( P ≤ 0.05) protein levels than fish fed the other three diets. These data indicate that the control diet in this study likely contained sufficient lysine, methionine and PUFA to meet the requirements of largemouth bass; however, additional methionine may improve feed conversion efficiency, and increased levels of PUFAs or other factors in squid oil may have a significant impact on body composition.     

Effects of Different Feed Habituation Methods on Survival and Feed Habituation Success of Largemouth Bass,Micropterus salmoides,in a Recirculating Aquaculture System

Demand for food size and trophy largemouth bass, Micropterus salmoides, is steadily increasing. However, largemouth bass, a carnivorous species, are more difficult to feed habituate than other commercially produced fish. Improving current feed habituation techniques to increase the percentage of fingerlings successfully feed habituated would increase profits, productivity and efficiency, and available product in the largemouth bass industry. The focus of this research was to evaluate different combinations of automatic feeders and supplemental hand feeding to determine the feed habituation success under commercial largemouth bass production conditions. Hand feeding, using only automatic feeders, or combinations of both, did not result in significant differences with regard to survival or feed habituation success. Initial fingerling size (total length, TL) was found to be the most important factor affecting survival and feed habituation success. Fish ranging from 40 to 50 mm (TL) survived and feed habituated at significantly higher rates than 30–40 and 50–60 mm (TL) fingerlings. Medium‐sized fish provide the best results in terms of feed habituation success and survival. The results suggest any combination of hand feeding and automatic feeders may be used to achieve feed habituating success in largemouth bass.     

Artificial Propagation and Induction of Triploidy in Largemouth Bass Micropterus salmoides and Ploidy Discrimination using Erythrocyte Length

We describe an artificial propagation procedure and simple ploidy discrimination techniques using erythrocyte major axis length for largemouth bass Micropterus salmoides. Hormonal treatments of 5 mg/kg of carp pituitary and 50 μg/kg of leutinizing hormone-releasing hormone (LHRH) produced viable gametes in 21-24 h, and triploidy was induced using a pressure treatment of 563 kg/cm² on embryos for a 1-min duration exactly 5 min following fertilization. We produced about 500 fingerling triploids and about 500 diploid controls, and verified genetic status of a subset of each group using flow cytometry. Erythrocyte length was measured for 10 known diploid and 10 known triploid individuals. Remaining fish were internally microtagged with group-specific tags and mixed to test the model. We developed ploidy discrimination intervals based on the 99% confidence limits of mean erythrocyte length (MEL, N = 25 erythrocytes) for individual fish, which were 14.43-16.66 μ.m for triploids, and 10.23-13.62 μm for diploids. Logistic regression provided the discrimination model: Ploidy status (±) = -196.16 + 13.97 x MEL, with positive (+) outcomes considered triploid. Both discrimination techniques were 100% effective at differentiating ploidy of the 22 microtagged largemouth bass recollected from the mixed population. We did not observe a significant change in erythrocyte length as fish size increased, indicating that erythrocyte length is an accurate predictor of ploidy for all sizes of largemouth bass.     

Effect of Dietary Lipid Level and Protein Energy Ratio on Growth and Body Composition of Largemouth Bass Micropterus salmoides

A feeding trial was conducted in aquaria with juvenile largemouth bass Micropterus salmoides to examine the effects of increasing dietary lipid levels on growth and body composition. Feed‐trained largemouth bass fingerlings were graded to a similar size (16.3 ± 2.4 g) and randomly stocked into 15 113.6‐L glass aquaria at 25 fish/aquarium. Fingerlings were fed twice daily to apparent satiation with one of five isonitrogenous extruded experimental diets based on practical ingredients. Diets contained approximately 40% crude protein and either 0, 5, 10, 15, or 20% added lipid. Due to background lipids in the ingredients, this equated to total lipid levels of 7, 10, 16, 20, and 23%, respectively. These diets had protein to energy ratios of 137, 120, 106, 95, and 86 mg/kcal, respectively. There were three replicate aquaria per dietary treatment. After 12 wk, there were no statistically significant differences (P > 0.05) in average weight (g), specific growth rate (% body weight/d), survival (%), or protein efficiency ratio (PER, %) among fish fed the five diets, which averaged 79.3 ± 5.6, 1.9 ± 0.1, 99.5 ± 1.5, and 2.11 ± 0.19, respectively. Juvenile largemouth bass fed diets containing 15 and 20% added lipid had significantly lower (P± 0.05) feed conversion ratios (FCR) (1.1 ± 0.0 and 1.1 ± 0. 1, respectively) than fish fed diets containing 0, 5, and 10% added lipid (1.4 ± 0.1, 1.3 ± 0. 1, and 1.3 ± 0.2, respectively). Proximate analysis of whole body samples indicated a significantly higher (P ± 0.05) lipid content in fish fed 15 and 20% added lipid compared to fish fed lower lipid levels. While FCR was lowest in fish fed the 15 and 20% added lipid diets, increased whole body lipid deposition may indicate that these levels are above optimal levels for juvenile largemouth bass. It appears that 7–16% total dietary lipid (P/E:137–106 mg/kcal) is sufficient to support efficient growth without impacting body composition in juvenile largemouth bass when fed a diet containing 40% crude protein.     

Replacement of Fishmeal with a Blend of Poultry Byproduct Meal and Soybean Meal in Diets for Largemouth Bass,Micropterus salmoides

A feeding trial was conducted to evaluate the potential of replacing fishmeal with poultry byproduct meal (PBM) and soybean meal in diets for largemouth bass, Micropterus salmoides. A reference diet (C) contained 400 g/kg fishmeal, and 40 or 60% of the fishmeal was replaced with a blend of pet‐food‐grade PBM and soybean meal (diets PP1 and PP2) or a blend of feed‐grade PBM and soybean meal (diets PF1 and PF2). No significant differences were found in weight gain, nitrogen retention efficiency (NRE), condition factor, and body composition among fish fed diets PP1, PP2, PF1, and PF2. Feed intake and feed conversion ratio (FCR) were higher in fish fed diet PF1 than in fish fed diet PP1. No significant differences were found in weight gain, NRE, condition factor, and body composition between fish fed diet C and diets PP1, PP2, PF1, and PF2. The feed intake and FCR were lower in fish fed diet C than in fish fed diets PP2, PF1, and PF2. This study reveals that dietary fishmeal level for largemouth bass could be reduced to 160 g/kg by inclusion of PBM and soybean meal in combination.     

The Effects of Biomass Density on Size Variability and Growth Performance of Juvenile Largemouth Bass,Micropterus salmoides,in a Semi‐closed Recirculating System

This study evaluated the effects of biomass density on size variability and growth performance of feed‐trained largemouth bass, Micropterus salmoides, fingerlings in a semi‐closed recirculating system for 60 d. Average individual body weight and length of fingerlings were 9.04 g and 9.07 cm, respectively. Experimental biomass densities were set at 15, 20, 25, 30, 35, and 40 kg/m³. Water temperature was adjusted to approximately 25 C and dissolved oxygen concentration was maintained above saturation. Fish were fed a formulated diet (42% protein) distributed by automatic feeders for 12 h daily. During the experiment, fingerlings actively fed and presented high survival rates (96.8–95.0%) at all densities. Growth performance of fingerlings was not affected by the biomass densities tested in this study (P < 0.05). The ranges of size distributions were similar among treatments, but more fingerlings were near the average size at lower biomass densities. Based on the results of this study, largemouth bass fingerlings were tolerant of high biomass density and a gross yield of 100–125 kg/m³ may be viable for largemouth bass reared in a semi‐closed recirculating system up to 30 g in weight.