不同投饲率对锦鲤幼鱼生长及鱼体生化成分的影响

采用同一种饲料,选取同批次的锦鲤幼鱼(17.50±1.04)g,研究投饲率对锦鲤幼鱼生长及鱼体生化成分的影响,分别设置5个投喂水平(鱼体质量1.0%、2.0%、3.0%、4.0%、5.0%),在水温为(27.0±1.0)℃的条件下40 d的养殖试验结果表明:随着投饲率的增加,特定生长率和相对增重率呈先上升后平稳的趋势,饲料利用率呈先下降后平稳再下降趋势;随着投饲率的增加,鱼体的粗蛋白、粗脂肪和灰分含量逐渐上升,而水分含量逐渐降低。根据相对增重率和饲料利用率综合分析,确定锦鲤幼鱼适宜投饲率在水温(27.0±1.0)℃时为4.0%。     

不同投饵率对施氏鲟幼鱼生长及体成分的影响

采用同一种饵料 5个投喂率水平 (1.5 %、2 .0 %、2 .5 %、3.0 %、3.5 % ) ,室外流水养殖系统 ,在水温 (16 .5± 1.8)℃的条件下对施氏鲟 (Acipenserschrenckii)幼鱼 (4 2 .6± 9.2 )g进行 4 2d生长实验。结果表明 ,相对增重率、饵料利用率、鱼体蛋白质及水分含量受投饵率影响显著 (P <0 .0 5 )。随着投饵率的增加 ,相对增重率呈先升高、后降低的趋势 ,饵料利用率随着投饵率的升高而下降。根据最大相对增重率和最大饵料利用率 ,确定施氏鲟幼鱼适宜投喂率在水温 15～ 18℃时为体重的 2 .0 %。     

人工养殖条件下不同投饵率对达氏鳇幼鱼生长影响的初步

为了确定达氏鳇幼鱼适宜的投饵率，选取同一种饲料设置的5个投饵率水平（分别为体重的0.5%、1.0%、1.5%、2.0%、2.5%），在水温17℃~20℃，溶氧量在6.2mg/l以上的环境下对达氏鳇幼鱼体重的生长进行为期30天的试验。应用软件SPSS对各实验组相应的数据进行分析，结果表明（1）达氏鳇幼鱼相对增重率和特定生长率都随投饵率的增加，先升高后下降；而饲料转化率则逐渐下降。（2）达氏鳇幼鱼在该条件下的最适投饵率为1.0%。     

不同投饵率对达氏鳇幼鱼生长影响的初步研究

为了确定达氏鳇(Huso dauricus)幼鱼适宜的投饵率,选取同一种饲料,设置的5个投饵率水平(分别为体重的0.5%、1.0%、1.5%、2.0%、2.5%),在水温17～20℃、溶氧6.2 mg/L以上的环境下,对达氏鳇幼鱼生长进行为期30 d的试验.应用SPSS软件对各实验组相应的数据进行分析.结果表明,5个投饵率水平的达氏鳇幼鱼相对增重率和特定生长率先升高、后下降、再升高、再下降,而饲料转化率则逐渐下降;达氏鳇幼鱼在该条件下的适宜投饵率为1.0%.     

不同投饵率对达氏鳇幼鱼生长影响的初步研究

为了确定达氏鳇(Huso dauricus)幼鱼适宜的投饵率,选取同一种饲料,设置的5个投饵率水平(分别为体重的0.5%、1.0%、1.5%、2.0%、2.5%),在水温17～20℃、溶氧6.2mg/L以上的环境下,对达氏鳇幼鱼生长进行为期30d的试验。应用SPSS软件对各实验组相应的数据进行分析。结果表明,5个投饵率水平的达氏鳇幼鱼相对增重率和特定生长率先升高、后下降、再升高、再下降,而饲料转化率则逐渐下降;达氏鳇幼鱼在该条件下的适宜投饵率为1.0%。     

投饲频率对俄罗斯鲟幼鱼生长、消化酶活力和氨氮排泄的影响

在室内水族箱条件下,以俄罗斯鲟(Acipenser gueldenstaedtii)幼鱼(4.42±0.06 g)为对象,探讨了投饲频率对幼鱼生长、消化酶活力和氨氮排泄的影响。实验采用等量投饲法,共设置4个投饲频率(2次·d-1、3次·d-1、4次·d-1和6次·d-1,分别记为F2、F3、F4和F6组),投饲实验为期42 d。结果表明,随着投饲频率增加,实验鱼的增重率升高,饵料系数下降。其中,F6组增重率最高,为461.33%,但与F3组(409.67%)和F4组(443.33%)之间的差异不显著;相应地,F3、F4与F6组实验鱼的饵料系数显著低于F2组(P0.05),而F3、F4与F6组之间的饵料系数无显著性差异。F2组和F6组肥满度较低,且显著低于F3组和F4组(P0.05);此外,实验鱼脏体比和肝体比随着投饲频率的增加而略有下降,但各组之间的差异均不显著(P0.05);肝脏淀粉酶活性和脂肪酶活性随投饲频率的增加而升高,胰蛋白酶活性的差异则不显著;提高投饲频率还可降低鱼的氨氮排泄率,其中F6组的耗氧率也显著低于其它组。结果显示,适当增加投饲频率可提高俄罗斯鲟的消化酶活力,降低蛋白被用于能量代谢的比例,从而提高了幼鱼的生长速度和饲料利用率。结合本实验的结果和生产实际情况,建议人工养殖鲟鱼幼鱼的投饲频率大于等于4次·d-1为宜。     

温度、体重和昼夜节律对大菱鲆幼鱼代谢的影响

在鱼体重相对恒定时,用流水法测定了温度、昼夜节律对大菱鲆幼鱼耗氧率、氨氮排泄率的影响;在温度相对恒定时,用静水法测定了体重对大菱鲆幼鱼耗氧率、氨氮排泄率,窒息点的影响。结果表明:在实验温度范围内,体重2.0 g的幼鱼,耗氧率随水温升高而上升;10℃时,耗氧率最低,在26℃达到最高;在18℃以上,温度再升高,大菱鲆幼鱼将分配更多的能量用于呼吸代谢。体重2.0 g的大菱鲆幼鱼氨氮排泄率随水温的升高而上升;在10℃时氨氮排泄率最低,26℃达到最高;大菱鲆幼鱼的氨氮排泄比较稳定,但在较高温度水平时大菱鲆幼鱼蛋白质代谢的强度增加。     

尼罗罗非鱼在淡水和海水中的生长及对蛋白质需求的比较

以酪蛋白为蛋白源,配制蛋白质含量为19 80%～40 50%的6种精饲料,采用室内循环水养殖系统,在饱食投喂和(27±1)℃水温条件下对吉富品系尼罗罗非鱼幼鱼进行8周的饲养实验,比较其在淡水和海水中的生长及蛋白质需求。结果显示:尼罗罗非鱼在淡水和海水中生长良好,存活率分别为100%和87%～100%;随着饲料蛋白质含量增加,实验鱼的平均终重、增重率和日增重率呈线性增加,饲料系数呈线性下降,蛋白质效率也呈下降趋势。在相同的饲料蛋白水平下,上述指标在淡水鱼和海水鱼之间均无显著差异蛋白质适宜需要量为28%～32%。     

投喂频率对绿鳍马面鲀幼鱼生长、生理指标及肝脏hsp70基因表达丰度的影响

为探究投喂频率对绿鳍马面鲀(Tharnnaconus septentrionalis)幼鱼生长、生理指标及肝脏hsp70基因表达的影响,本研究设5个投喂频率,分别为1、2、3、4和5次/d (分别简称为F1、F2、F3、F4和F5),每个处理组设3个平行,每缸养殖30尾鱼[(6.47±0.56)g]。实验期间,水温为17℃~26℃,盐度为30~31,pH为6.8~7.6,溶解氧≥5 mg/L,养殖周期为30 d。结果表明,不同投喂频率对绿鳍马面鲀幼鱼的生长、体成分、消化酶和抗氧化酶活性均有影响。随着投喂频率的增加,绿鳍马面鲀幼鱼的摄食和生长均呈上升趋势,F5组数值最大,摄食率为3.95%,增重率为347.19%,特定生长率为5.07%/d,增重率为F1组的2倍多。F1组的肥满度为1.79,显著低于其他4组(P<0.05);肝体比逐渐升高,F4和F5组的肝体比显著高于其他3组(P<0.05)。增加投喂频率,鱼体的粗蛋白含量呈先升高后降低的趋势,F2组最高,为59.82%;粗脂肪含量呈逐渐升高的趋势,F5组最高,为31.23%。胰蛋白酶活性随投喂频率增加呈先降低后增加的趋势,F3组活性最低,为37.48 U/μg prot;脂肪酶活性逐渐升高,F5组最高,为2.67 U/g prot;淀粉酶活性不受投喂频率的影响(P>0.05)。过氧化氢酶、超氧化物歧化酶活性和丙二醛含量最高均在F5组,分别为14.71 U/mg prot、250.32 U/mg prot和2.73 nmol/mg。肝脏中hsp70基因的相对表达量不受投喂频率的影响(P>0.05)。基于绿鳍马面鲀幼鱼的生长性能和生理效应的综合考虑,其最适投喂频率为3次/d。     

不同水温对个体养殖系统中华绒螯蟹幼蟹蜕壳生长和摄食率的影响

为探讨不同水温对中华绒螯蟹(Eriocheir sinensis)幼蟹蜕壳、生长和摄食率的影响,本研究应用恒温的河蟹个体养殖系统,分析不同水温(10、15、20、25、30℃)对中华绒螯蟹幼蟹的成活率、蜕壳次数、蜕壳间隔、蜕壳增重率、肥满度和摄食率的影响。结果显示:在133 d的试验中,各饲养水温的中华绒螯蟹成活率均在89%以上;10℃和15℃水温的实验蟹只蜕壳1次,20℃和25℃水温组的实验蟹蜕壳2次,30℃水温组的实验蟹蜕壳3次;五个水温组的平均蜕壳间隔分别为109.39、67.92、46.63、43.69、38.01 d;蜕壳增重率随水温升高呈总体增加的趋势,30℃水温组的蜕壳增重率显著高于其他水温组;平均绝对生长率和相对生长率均随着水温的升高而逐步增大,且各水温组间差异显著;肥满度随水温的升高而逐渐下降;五个水温组的平均日摄食率分别为1.58%、1.97%、3.54%、4.79%和5.25%。腿部肌肉切片观察发现,低水温组(10、15、20℃)的肌纤维直径显著大于高水温组(25、30℃)。结果表明:随着饲养水温的增加,河蟹的蜕壳速度加快,增重率增加,肥满度下降,摄食率增加,以30℃水温时的河蟹生长最佳。     

Effect of Dietary Protein Concentration and Feeding Rate on Weight Gain,Feed Efficiency,and Body Composition of Pond-Raised Channel Catfish Ictalurus punctatus1

Two experiments were conducted in earthen ponds to evaluate the effect of dietary protein concentration and feeding rate on weight gain, feed efficiency, and body composition of channel catfish. In Experiment 1, two dietary protein concentrations (28% or 32%) and four feeding rates (≤ 90. ≤ 112, ≤ 135 kg/ha per d, or satiation) were used in a factorial arrangement. Channel catfish Ictalurus punctatus fingerlings (average size: 27 g/fish) were stocked into 0.04-ha ponds at a rate of 24,700 fish/ha. Fish were fed once daily at the predetermined maximum feeding rates for 282 d (two growing seasons). In Experiment 2, three dietary protein concentrations (24, 28, or 32%) and two feeding rates (≤ 135 kg/ha per d or satiation) were used. Channel catfish (average size: 373 g/fish) were stocked into 0.04-ha ponds at a rate of 17,300 fish/ha. Fish were fed once daily for 155 d. In both experiments, five ponds were used for each dietary treatment. Results from Experiment 1 showed no differences in total feed fed, feed consumption per fish, weight gain, feed conversion ratio (FCR), or survival between fish fed diets containing 28% and 32% protein diets. As maximum feeding rate increased, total feed fed, feed consumption per fish, and weight gain increased. There were no differences in total feed fed, feed consumption per fish, or weight gain between fish fed at ≤ 135 kg/ha per d and those fed to satiation. Fish fed the 28% protein diet had a lower percentage carcass dressout and higher percentage visceral fat than fish fed the 32% protein diet. Dietary protein concentrations of 28% or 32% had no effect on fillet protein, fat, moisture, and ash. Feeding rate did not affect FCR, survival, percentage carcass dressout, or fillet composition, except fillet fat. As feeding rate increased, percentage visceral fat increased. Fish fed at ≤ 90 kg/ha per d had a lower percentage fillet fat than fish fed at higher feeding rates. In Experiment 2, dietary protein concentration or maximum feeding rate did not affect total feed fed, feed consumption per fish, weight gain, FCR, or survival of channel catfish. Feeding rate had no effect on percentage carcass dressout and visceral fat, or fillet composition. This was due to the similar feed consumption by the fish fed at the two feeding rates. Fish fed the 24% protein diet had lower carcass dressout, higher visceral fat and fillet fat than those fed the 28% or 32% protein diet. Results from the present study indicate that both 28% and 32% protein diets provide satisfactory fish production, dressed yield, and body composition characteristics for pond-raised channel catfish fed a maximum rate of 90 kg/ha per d or ahove.     

Optimization of Feeding Rate for Hatchery-Produced Juvenile Gilthead Sea Bream Sparus aurata

Abstract.— A 61-d growth trial (five 11-d feeding periods) was conducted to determine the effects of feeding rate on growth, feed utilization, morphology, and body composition of the gilthead sea bream Sparus aurata . Gilthead sea bream juveniles with an average initial body weight of 3 g were fed a commercial diet (51% crude protein, 11% crude fat) at rates of 0.5, 1.0, 1.5, 2.0, 2.5, or 3.0% of their body weight (BW) per day in two equal meals. Water temperature was approximately 21.4 C throughout the experiment. Each ration was administered to triplicate groups of 60 fish, with ration readjusted every 11 d. Growth rate was measured as specific growth rate (SGR). Survival rate and coefficient of variation did not differ significantly among the groups fed different rates. Body weight, condition factor, and hepatosomatic and viscerosomat-ic indices displayed significant increases with increasing feeding rate from 0.5 to 3.0% BW/d. Fish fed 0.5% BW/d had significantly higher moisture and ash and lower protein contents than those fed at higher rates. Moisture and protein contents were not significantly different for fish fed at the highest feeding rates (2.0, 2.5, and 3.0% BW/d). Lipid contents increased significantly with increasing feeding rate from 0.5 to 3.0% BW/d. The SGR showed a curvilinear significant increase when the feeding rate was increased from 0.5 to 3.0% BW/d. Feed efficiency (FE) increased significantly to a maximum value with increasing feeding rate from 0.5 to 2.0% BW/d and decreased significantly with increasing feeding rate from 2.5 to 3.0% BW/d. Based on the data obtained, feeding rates of 2.3% and 0.6% BW/d are recommended as optimum and maintenance rations, respectively.     

Growth and Feed Conversion of Sub-Yearling Atlantic Sturgeon,Acipenser oxyrinchus,at Three Feeding Rates

Abstract

Growth and survival of fingerling Atlantic sturgeon, Aci-penser oxyrinchus, were examined at three different feed rates. Sturgeon (mean initial weight±SD of 28±12 g) were offered a closed-formula, commercially-available sturgeon diet (48.5% protein, 16.2% fat, 9.9% moisture, 7.6% ash, 0.5% fiber and 17.4% nitrogen free extract) via 24-hour, time-controlled feeders at rates of 1.5, 3.0, and 4.5% body weight per day (BW/day). Mean water temperature was 16.8°C. After 49 days of feeding, final length, final weight and feed conversion were all significantly affected by feeding rate (P ≤ 0.05). Peak feed conversion occurred at a ration of 1.5%, while maximum increase of both length and weight occurred at approximately 3.0%. No mortality occurred during the seven-week trial. The choice of feeding rates will ultimately depend upon production requirements and the culturist. Offering diet at a rate of 3.0% BW/day will result in significantly greater growth accompanied by high survival. Delivering diet at a rate of 1.5% BW/day will result in equally high survival and require approximately 50% less diet. It will, however, yield lower growth rates.     

Effect of feed restriction on the growth performance of turbot (Scophthalmus maximus L.) juveniles under commercial rearing conditions

Two trials were performed to study the effect of periodic feed deprivation (trial 1) or feed restriction, followed by satiation feeding (trial 2) on the growth performance of turbot juveniles under commercial rearing conditions. In trial 1, duplicate groups of 350 fish with an initial weight of 62 g were fed a commercial diet to apparent visual satiation for 7, 6, 5 or 4 days a week for 83 days. At the end of the trial, fish weight was directly related to the number of feeding days but feed efficiency and protein efficiency ratio were not affected by treatments. At the end of the trial, there were no differences in whole‐body composition among groups. In trial 2, duplicate groups of 500 fish with an initial weight of 33 g were fed a commercial diet to satiation (100%) or feed restricted to 90%, 80% and 70% of satiation for 90 days. Thereafter, all groups were fed to satiation for 34 days. During the feed restriction period, growth was directly related to feed intake, while during the satiation feeding period, it was inversely related to the previous feeding level. At the end of the trial, the final weight was not different among groups. At the end of the feed restriction period, whole‐body lipid content showed a trend to decrease with an increase in the feed restriction level. The results of this study indicate that under practical conditions, turbot juveniles should be fed daily as even cycles of short periods of feed deprivation negatively affect growth, while not improving feed efficiency. On the contrary, even after a relatively long feed restriction period, fish shows compensatory growth, and this may be used as a feed management strategy for controlling fish production in commercial farms.     

不同投饵率对暗纹东方鲀幼鱼生长的影响

比较投饵率水平分别为3%、4%、5%、6%时,对暗纹东方鲀幼鱼生长、饲料效率的影响,以确定暗纹东方鲀幼鱼阶段的适宜投饵率。在23℃下,对规格为3.45～3.56g的暗纹东方鲀幼鱼进行30d的生长实验,结果表明:不同投饵率对暗纹东方鲀幼鱼的特定生长率、质量相对增加率、饲料效率、存活率均有显著影响(p<0.05);暗纹东方鲀幼鱼的适宜投饵率为4%,在投饵率为4℅时,质量相对增加率为116.04±0.04%,饲料效率达83.70±0.02%,特定生长率为111.49±0.03%/d,存活率为84.44±0.02%。     

Effects of feeding rate on growth, feed utilizationand body composition of a tropical bagrid catfish

A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P > 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P > 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.     

Dietary Protein Level and Feeding Rate for Hybrid Clariid Catfish,Clarias gariepinus X Heterobranchus bidorsalis,in Homestead Tanks

Abstract

A 3 × 3 factorial experiment was designed to determine the effects of protein levels and feeding rate on growth and body composition of hybrid clariid catfish, Clarias gariepinusX Heterobranchus bidorsalis, over 12 weeks experimental period. Hybrid catfish (initial mean weight 12.53±0.35 g) were stocked in three feeding rates (3%, 5%, or 7% body weight/day (bw/day) and three crude protein levels (30%, 35%, or 40%). Each treatment was assigned randomly to three tanks. Final weight was higher for fish fed at 40% than those fed at 30% and 35% CP. There was no significant difference (P >0.05) in fish fed at 3%, 5%, and 7% bw/day. Also, there was no significant interaction between feeding rate and dietary protein level for weight gain, specific growth rate or feed conversion ratio. Weight gain and feed efficiency under feeding rates increased linearly as protein level increased. Dietary protein levels and feeding rate had significant effect on fish survival. Protein levels had a positive linear effect on fish body protein in all the feeding rates. Based on the above results, 40% CP level and 5% bw/day feeding rate are suggested to be optimal for achieving optimum growth rate and body composition.     

饲料蛋白质水平对马苏大麻哈鱼幼鱼生长指标和饲料系数的影响

为了解在水温7.4~11.3℃的流水池养殖条件下马苏大麻哈鱼(Oncorhynchus masou masou)幼鱼饲料中不同蛋白质水平对其生长指标和饲料利用效率的影响,设计了5组蛋白质水平为40.40%、44.84%、50.16%、54.82%和59.03%的养殖试验,养殖期为150d。试验过程中进行了水质化学指标的监测,结果表明随着饲料蛋白质水平增高,总氮、氨氮、亚硝酸盐氮有升高的趋势,40.40%组与44.84%、50.16%、54.82%及59.03%组总氮具统计学意义差异;59.03%组与其余4组氨氮、亚硝酸盐氮具统计学意义差异;40.40%、44.84%、50.16%、54.82%4组间总磷、硫化物和COD无统计学意义差异,59.03%组与上述4组间总磷、硫化物和COD均具统计学意义差异。生长试验结果表明:随蛋白质水平升高,40.40%、44.84%、50.16%组间终末体质量、增重率有显著升高的趋势(P<0.05),54.82%、59.03%组间终末体质量显著降低;50.16%试验组与其余4组特定生长率具统计学意义差异。各试验组随蛋白质水平升高,饲料系数有下降的趋势,40.40%、44.84%组的饲料系数是2.02、1.98,显著高于50.16%、54.82%、59.03%试验组,饲料蛋白质含量从40.40%增加到59.03%,饲料系数有逐渐降低趋势。通过生长指标和折线模型计算马苏大麻哈鱼幼鱼饲料适宜蛋白质含量为50.78%。     

不同投饵率对花鳗鲡黑仔苗生长的影响

实验设置1.0%,1.5%,2.0%,2.5%,3.0%五个不同投饵率水平,在水温30℃的条件下,选取同一种饲料,对规格为3.67±0.30g的花鳗鲡黑仔苗进行40d的生长实验。结果表明,投饵率对花鳗鲡黑仔苗的相对增重率、特定生长率、饲料转化率均有显著性影响（p〈0.05）,花鳗鲡黑仔苗生长的适宜投饵率是2.0%;在此投饵率下,花鳗鲡黑仔苗的饲料转化率为（47.39±1.17）%,特定生长速率为（1.08±0.03）%/d,相对增重率为（52.49±1.04）%,存活率为100%。     

Effects of feeding rates on growth and production of Nile tilapia, common carp and silver carp polycultured in fertilized ponds

Abstract In an attempt to identify appropriate feeding rates for multispecies of fish raised in fertilized earthen ponds, the present work was conducted over a 19‐week experimental period to establish the growth performance, production and body composition of Nile tilapia, common carp and silver carp fed 0.0%, 0.5%, 1.0%, 3.0%, 5.0% biomass and to apparent satiation (treatments). Twelve ponds were stocked with a similar number and weight of each fish species. Two ponds were assigned to each of the treatments, and a 25% protein pelleted fish feed was used to feed fish at the specified rate of feeding. At the end of the experiment, growth, weight gain, survival, yield and body composition of fish groups were affected by the treatments. The economic effectiveness also varied among treatments. The most conspicuous attribute of the feeding rates was its lack of influence on growth (g day^?1), weight gain (g per fish), yield (kg ha^?1) or body composition of silver carp. The results of whole‐body proximate analysis indicated that various feeding rates had either an irregular pattern or no effects on the protein and ash gain per 100 g of fish body weight (bw) gain. The most notable exceptions were significant (P < 0.05) increases in body fat and gross energy gains in Nile tilapia, common carp and silver carp accompanied by decreases in percentages of moisture (but not in silver carp) as feeding rate increased. Among the six different feeding levels, feeding to apparent satiation (feed amount was equivalent to 2.67% of fish bw day^?1) appeared to be optimal, as it significantly (P < 0.05) supported the highest fish production, income and net profit compared with all other treatments except for the 3% feeding level, for which the differences in those measurements were comparable.