Effects of stocking density and feeding levels on growth and feed efficiency of Nile tilapia (Oreochromis niloticus L.) fry

The effects of stocking density and feeding levels on larval survival, growth rates, feed utilization efficiency and body composition of Nile tilapia (Oreochromis niloticus L.) fry were investigated in two consecutive experiments. In experiment 1, swimup fry (0.016 g average body weight) were stocked in 20‐L fibreglass tanks, in a closed, recirculating indoor system, at five stocking densities (3, 5, 10, 15 and 20 fry L^?1) and fed a larval test diet (40% crude protein) to apparent satiation, three times a day, for 40 days. Fish survival, percentage weight gain and specific growth rate (% SGR) were negatively correlated with stocking density. The best performance was achieved at 3 fry L^?1. However, no significant differences in growth parameters were found between 3 and 5 fry L^?1. Body composition was not significantly affected by stocking density. In experiment 2, fry (0.016 g average body weight) were stocked at 5 fry L^?1, and fed a larval test diet (40% crude protein) at six feeding levels (10%, 20%, 25%, 30% and 35% BW day^?1) and to satiation, three times a day for 40 days. Fish growth rates and survival were extremely poor at 10% feeding level, and improved significantly with increasing feeding levels up to 30%, and levelled off with further increase in feeding levels. On the contrary, feed conversion ratio (FCR) and protein production value (PPV) were negatively correlated with feeding level. The lowest feeding level (10%) produced significantly lower body lipid and higher protein and ash than other feeding levels. The present results suggest that the optimum stocking density and feeding level of Nile tilapia fry are 5 fry L^?1 and 30% per day respectively.     

Effect of feeding frequency on growth, survival and feed utilization in fingerlings of Catla catla (Hamilton), Labeo rohita (Hamilton) and Cirrhinus mrigala (Hamilton) in outdoor rearing systems

Fingerling rearing of Indian major carps, Catla catla, Labeo rohita and Cirrhinus mrigala, were conducted in concrete tanks under a polyculture system at a density of 0.3 million fry ha^?1 to evaluate the effect of one, two or three feedings per day on growth, survival and feed utilization. Fry were fed with formulated supplementary diet at 10% of biomass per day during the first 15 days, followed by 8% in the next 15 days and 6% thereafter, for 60 days. Feeding of fish three times daily led to higher growth (103.9±8.5 mm/10.3±2.4 g) than those feeding twice (100.2±4.8 mm/9.9±1.5 g) or once (97.2±9.8 mm/9.4±2.1 g) daily, although the values were not significantly different (P>0.05). Survival rate ranging between 72.3% and 75.1% also did not vary significantly (P>0.05) among the treatments. However, higher feeding frequencies resulted in better feed utilization as evident from decreasing feed conversion ratio values. The present study suggested requirement of a higher feeding frequency for rohu compared with catla and mrigal.     

Effect of feeding frequency on growth and food conversion of Cyprinus carpio fry

Cyprinus carpio fry (173 ± 38 mg) were fed 6 times a day, 3 times a day, 2 times a day, once a day, once in 2 days, once in 3 days or given no food at all for a total period of 21 days. Food consumption by the group fed 3 times a day was maximum (45.6 gcal^*/meal) and the level of consumption per meal was very low in the remaining groups.

Feeding rate increased to a maximum (598.2 gcal g⁻¹ day⁻¹) in fry fed 3 times a day; a further increase in feeding frequency reduced the feeding rate. Feeding frequency influenced all bioenergetic parameters except absorption efficiency which remained constant at 97.7%. Although the growth efficiency did not change significantly in the groups fed very frequently (2 times a day or more), the growth rate was maximum in the group fed 3 times a day. With regard to both feeding and growth, a feeding schedule of 3 times a day seemed to be optimum and was suggested for practical nursery culture of Cyprinus carpio.     

Factors affecting androgen sex reversal of Tilapia aurea

Tilapia aurea were fed a single level of androgen-treated feed (ethynyltestosterone at 60 mg/kg of feed — ET-60) under a variety of conditions to determine the effect on sex reversal. Sex ratios were significantly altered in favor of males in 16- and 19-day treatments at 21 and 30° C; all-male populations were produced in 21- and 28-days at 21° C, but a few females persisted in the groups at 30° C. Feeding regimes of 12% body weight/day and satiation had variable impacts on growth but did not adversely affect success of sex reversal, except at higher temperatures. Because of higher metabolic rate at 30° C and the concomitant increase in appetite, a fixed level of feeding at 12% of body weight was considered to be limiting and was later increased to 15%. High stocking density (2600 fry/m² of surface) reduced growth rate but did not affect sex reversal. A 21-day treatment with ET-60 fed at 15% body weight/day at water temperatures between 21 and 30° C should consistently produce all-male populations of T. aurea at stocking densities up to 2600 fry/m².     

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.     

Controlled propagation of the African catfish,Clarias lazera (C. & V.): III. Feeding and growth of fry

The suitability of some common, natural and artificial feedstuffs for the rearing of fry of Clarias lazera (C. & V.) was investigated in 2 experiments.It was found that a dry trout starter, an experimental dry feed and dried inactive yeast were not suitable feeds for rearing C. lazera fry. Neither could ground Clarias fingerlings or frozen zooplankton be used. By contrast, frozen Artemia and especially live Artemia and live zooplankton gave good results. After 4 weeks the fish thus fed had attained an average weight of 0.3 to 1 g and survival ranged from 50 to 96%.Feeding in excess of satiation and feeding 24 h/day gave the fastest growth, although the differences in comparison with feeding Artemia or live zooplankton to satiation 4 times per day were not significant. The specific growth rate (% body weight) of these fish decreased from 68% at the start of the experiment to 9% after 28 days.     

Sex reversal and growth of Oreochromis spilurus (Günther) in brackish and sea water by feeding 17α-methyltestosterone

Abstract. An investigation was undertaken to study the effect of 17α-methyiteslosterone (17-MT) on the sex reversal and growth of tilapia, Oreochromis spilurus (Günther), in brackish water (3–5 ppt) and sea water (40 ppt). Seven experiments were performed; four in brackish water and three in sea water. Yolk-sac fry (1 or 3 day age) were immersed (7 or 24 h/day) in water containing hormone at a concentration of 0–10mg/l for 4–25 days. The swim-up fry were subsequently fed either normal or hormone-impregnated diets (30–70 mg/kg) for another 35 days starting from first feeding. The growth and SGR of fry were better in groups which received hormone both in water and food as compared with water or food alone. Immersion In 5–10 ppm (24 h/day) brackish water solution for 5 days did not bring any change in growth or sex ratio. However, immersion in sea water solution for 25 days (7 h/day) at a concentration of 1 ppm induced positive growth but no change in sex ratio. Higher doses either did not affect or reduced growth and SGR but induced higher percentages (77–83%) of males. Complete masculinization (100%) was observed only in brackish water when fish were immersed in 2·5 ppm solution for 4 days (24 h/day) and later fed 50 mg/kg in diets for 35 days. These results were further confirmed when the immersion schedule was modified to 10 days (7 h/day) and feeding 50–70 mg/kg hormone. It can be concluded from these studies that in brackish water complete masculinization of O. spilurus is possible through immersion in 5·0 ppm for a minimum of 75 h followed by feeding with 50 mg/kg food for a minimum of 40 days starting from first feeding.     

Evaluation of live duckweed,Wolffia globosa as an allochthonous feed for Labeo rohita fry during nursery rearing

A 40 days feeding trial with Labeo rohita (rohu) fry was conducted in six outdoor cemented tanks (5m × 4m × 1 m; 6–8 cm soil base) to establish the relative impact of on‐farm grown live Wolffia globosa (a duckweed with crude protein of 28.57%) and a formulated iso‐nitrogenous feed (crude protein 28.37%) on growth performance, survival, health and overall quality of fingerlings. The experimental tanks were dried, limed at 250 kg/ha, filled with ground water and subsequently applied with cow dung (soaked overnight) and mustard oil cake at 1,000 kg/ha and 50 kg/ha respectively. The fry were stocked at 0.3 millions/ha in six prepared tanks, and fed live Wolffia (T1) and formulated feed (T2). Results of the study indicate better performance (p < 0.05) of fry in terms of final mean weight (7.83 g), length (8.82 cm), daily growth index (6.51 g %/day) and survival (89.5%) than those fed on formulated feed. Furthermore, significantly improved (p < 0.05) feed utilization parameters viz. apparent feed conversion ratio (AFCR), apparent protein conversion efficiency (APCE), apparent protein efficiency ratio (APER); haematological parameters viz. total erythrocyte count (TEC), total leucocyte count (TLC), packed cell volume (PCV), plasma glucose and protein of fry were also observed in T1 (live Wolffia). Overall findings from this study hints towards the possible utilization of on‐farm grown live Wolffia as a suitable nutrient source for fry rearing of L. rohita.     

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.     

不同驯化方式对哲罗鱼仔、稚鱼生长和存活的影响

在水温8．9～14．2℃下,在平列糟（长3m,宽0．4m,高0．2m）中采用A、B和C组三种投喂方式驯养刚开口摄食、体质量0．129±0．07g的哲罗鱼（Huchotaimen）苗60d,以探讨驯化方式对哲罗鱼仔、稚鱼生长、存活和种群变异系数的影响：A组以浮游动物开口,投喂浮游动物3d,投喂水蚯蚓15d后,改投人工饲料;B组以水蚯蚓开121,投喂水蚯蚓15d后,改投人工饲料;C组直接以人工饲料开口。结果表明：C组体质量特定生长率（3．577±0．78％／d）,明显大于A组（3．132±0．87％／d）和B组（3．024±0．91）;A、B、C组的成活率分别为75．67％、74．87％和84．36％,C组明显大于A、B组;A、B和c组鱼体质量变异系数依次为21．47％、22．59％和11．32％,实验表明,直接以人工饲料开口是哲罗鱼规模化养殖中合理的驯化投喂模式。     

投喂频率对尼罗系吉富罗非鱼幼鱼胃排空、生长性能和体组成的影响

通过胃排空试验与养殖试验研究了不同投喂频率对尼罗系吉富罗非鱼幼鱼的胃排空、生长性能以及体组成的影响.在试验开始时,观测尼罗系吉富罗非鱼幼鱼的胃内饲料排空情况,胃排空试验结果表明,胃排空率的最佳描述为平方根函数,胃内饲料在饱食投喂后15 h左右完全排空,达到投喂前水平,80％胃排空为9h,也就是投喂后大约9h恢复食欲.360尾试验鱼(初始体质量3.72 g)以不同的投喂频率(1d4次、1d3次、1d2次、2d4次、2d3次、2d2次)分组,每组设立3个平行组,随机养殖于18个网箱中,每箱养殖20尾鱼,按饱食量投饲膨化饲料.养殖期为6周.尼罗系吉富罗非鱼幼鱼在投喂频率为1d4次、1d3次和1d2次时特定生长率和饲料效率显著高于投喂频率为2d4次、2d3次和2d2次时(P＜0.05)；投喂频率为1d2次、2d4次、2d3次和2d2次时其摄食量显著低于1d4次和1d3次时(P＜0.05).随着投喂频率降低,鱼体水分含量逐步上升,脂肪和蛋白质含量逐步下降,其中1d4次、1d3次组鱼与2d2次组鱼有显著性差异(P＜0.05).各投喂频率组间的肝体指数无显著性差异(P＞0.05).3.7～48.0 g尼罗系吉富罗非鱼幼鱼的适宜投喂频率为1d2次,较2d2次、2d3次和2d4次时明显提高了生长速度和饲料效率,较1d3次、1d4次摄食量显著降低.2种试验结果较为一致.     

Growth and fry production of Nile tilapia, Oreochromis niloticus (L.), on different feeding schedules

The effect of scheduled use of high‐protein and low‐protein diets on body weight and fry production of Nile tilapia, Oreochromis niloticus (L.), was determined. A preliminary feeding trial was first conducted on fingerlings. These were fed a high‐protein diet (H, 25% protein) or a low‐protein diet (L, 18% protein) daily, or diet H for 1–3 days followed by diet L for 1–4 days. Final body weight was significantly higher (P < 0.05) in fish fed diet H daily and in fish fed diet H for 2–3 days followed by diet L for 1 day (2H?1L and 3H?1L). Fingerlings on 1H?1L and 3H?2L had slightly lower growth. Based on the response of the fingerlings, five feeding schedules were tested with the broodstock. A high‐protein diet (HP, 40%) and a low‐protein diet (LP, 25%; same as H for fingerlings) were used. Feeding schedules significantly influenced body weight of female but not the male fish. Fry production was not significantly affected by the feeding schedule for broodstock. When growth, fry production and saving in feed cost were all considered, the broodstock on 1HP?1LP and 3HP?2LP feeding schedules both gave the highest overall performance. These findings give fish farmers an option in the management of feeding of tilapia broodstock.     

Feed intake,growth, feed utilization,body composition and waste output of juvenile hybrid bream at different feeding frequencies

An eight‐week feeding trial was conducted to evaluate the feed intake, growth, feed utilization, body composition and waste output of juvenile hybrid bream at different feeding frequencies (0.5, 1, 2, 3 or 4 meals/day). Fish (initial body weight of 10.6 ± 0.8 g) were fed to satiation at each feeding. The test diet contained 336 g/kg crude protein and 79 g/kg crude lipid. The weight gain significantly increased with increase in feeding frequency from 0.5 to 3 meals/day (p < 0.05) and afterwards did not change with feeding frequency from 3 to 4 meals/day (p > 0.05). The feed intake increased with increase in feeding frequency (p < 0.05). Fish fed at 3 meals/day exhibited the lowest feed conversion ratio and waste output of nitrogen and phosphorus, however, the highest nitrogen retention efficiency (p < 0.05). No significant differences were found in the phosphorus retention efficiency, the body composition of crude protein, ash and phosphorus among all the feeding frequencies (p > 0.05). The body lipid content increased, whereas the content of moisture decreased, with the increase in feeding frequency (p < 0.05). The present study reveals that the optimum feeding frequency is 3 meals/day for hybrid bream.     

Effects of different feeding regimes on juvenile black rockfish (Sebastes schlegilii) survival,growth, digestive enzyme activity,body composition and feeding costs

The objective of this study was to establish a proper feeding regime for juvenile black rockfish (Sebastes schlegilii) intended for stock enhancement. We used a combined experimental design to assess the effects of different feeding rates (1%, 3% and 5% body weight per day (BW/day)) and feeding frequencies (apparent satiety or restricted feeding 1 to 3 times daily) on survival, growth, digestive enzyme activity, body composition and feeding costs over 50 days, from newly weaned (initial average weight 1.5 ± 0.2 g) to release size. The results showed that feeding rate significantly affected fish growth, feed utilization and body composition. The highest feed conversion ratio was at 3% BW/day. Increased feeding rates resulted in enhanced growth and higher body lipid content, but this was also accompanied by decreased contents of moisture, protein and ash. With feeding to apparent satiety, increased feeding frequency resulted in higher growth performance and enhanced intestinal lipase activity but decreased gastric protease activity. There were no growth improvements or effects on digestive enzyme activity and body composition with increasing feeding frequency (from one to three times daily) under a fixed‐quantify feeding (3% BW/day). Feed costs increased with increasing feeding rates or apparent satiety feeding frequencies and were associated with shorter growth times to reach a suitable size for release. Our study suggests that a feeding rate of 3% BW/day is the best feeding regime for proper growth and reduced feed costs in juvenile black rockfish before releasing for stock enhancement.     

Effect of feeding frequency on growth,feed utilization,body composition and waste output of juvenile golden pompano (Trachinotus ovatus) reared in net pens

A 6‐week feeding trial was conducted to examine the effect of feeding frequency on growth, feed utilization efficiency, body composition and waste output of juvenile golden pompano Trachinotus ovatus reared in net pens. Fish (10.3 ± 0.5 g) were either fed a formulated diet containing 48.4% crude protein and 5.7% crude lipid at 0.5, 1, 2, 3 or 4 meals per day or fed a raw fish feed at two meals per day as a control. The weight gain (WG) increased with increasing feeding frequency from 0.5 to 3 meals per day (P < 0.05), but did not significantly change with the further increase in feeding frequency from 3 to 4 meals per day (P > 0.05). The feed intake (FI) was lower in fish fed at 0.5 or 1 meal per day than in fish fed at 2, 3 or 4 meals per day (P < 0.05). No significant differences were found in the feed conversion ratio (FCR), nitrogen retention efficiency (NRE), condition factor (CF), nitrogen waste output (NWO) and phosphorus waste output (PWO) between fish fed at 1, 2, 3 or 4 meals per day (P > 0.05), whereas no significant difference was found in the phosphorus retention efficiency (PRE) among the feeding treatments (P > 0.05). The body lipid content increased, whereas the contents of moisture and ash decreased, with the increase in feeding frequency (P < 0.05). At the same feeding frequency, fish fed the formulated diet exhibited lower FI, FCR, HSI, body moisture content, NWO and PWO, but higher NRE, PRE, body lipid content and body phosphorus content than those of fish fed the raw fish feed (P < 0.05). These results suggest that the formulated diet can satisfy nutrient requirements of juvenile golden pompano reared in net pens, and the suitable feeding frequency is 3 meals per day.     

Effects of feeding frequency and dietary energy level on growth and body composition of juvenile flounder, Paralichthys olivaceus (Temminck & Schlegel)

A two (dietary energy levels; low energy, LE and high energy, HE) × 4 (feeding frequency; one feeding in 2 days, one feeding daily, two times daily and three times daily) factorial experiment was performed to determine the effects of dietary energy level and/or feeding frequency on the growth and body composition of juvenile flounder Paralichthys olivaceus. The survival rate was not significantly different among treatments. Weight gain of fish fed the LE and HE diets significantly increased as feeding frequency increased. The weight gain of fish fed the LE diet was higher at each level of increasing feeding frequency. The weight gain of fish fed the HE diet was higher than that of fish fed the LE diet once in 2 days and once daily, but weight gain of fish fed the HE diet was lower than the LE diet three times daily. Daily feed intake was significantly influenced by feeding frequency, but not by dietary energy level. Feed efficiency of fish fed the HE diet once daily was significantly higher than that of fish fed the LE diet once in 2 days, but no significant difference in feed efficiency was observed among other groups of fish. The protein efficiency ratio of fish fed the LE diet once in 2 days was the lowest. Feeding frequency and dietary energy level had a significant effect on the body lipid content. A feeding frequency of two times or three times daily would be effective, depending on dietary energy level for maximum growth of juvenile flounder grown from 3.5 to 15 g.     

First feeding of common wolffish on formulated dry feed diets in a low water-level raceway system

Wolffish (Anarhichos lupus) larvae were first fed in a low water-level raceway system, with two new types of formulated dry feed diets. Water level in the rearing tank was 1.5 cm. The fish showed a high preference for feeding from the surface. During the first week the fish experienced a drop in dry weights. The highest SGR of 5.8% was obtained between day 35–60. The best feeding regime gave a survival rate of 82 (2.5)%. Results indicate failure to initiate feeding as a main cause of mortality in the fed groups. Death by starvation occurred after 30–40 days. It is speculated whether the large difference in growth rates between the two feeding regimens is due to differences in carbohydrate levels between the two feed types. The rearing tank technology proved, with minor adjustments, to be self-cleaning and well suited for first feeding of wolffish.     

The effect of feeding rate on the growth performance of green sturgeon (Acipenser medirostris) fry

Four one‐week growth trials were conducted on green sturgeon fry to determine the effect of feeding rate on their growth performance at 18 °C when they were fed a salmonid soft moist feeds containing 445–457 g kg^?1 of crude protein and 201–207 g kg^?1 of lipid. The fry used in Trials I‐IV were 5–8 weeks after their initiation of exogenous feeding. Their average initial body weights were 1.63 ± 0.01, 2.63 ± 0.03, 5.08 ± 0.08 and 7.49 ± 0.05 g, respectively. Six feeding rates used were as follows: 2.5–15.0% body weight per day (% BW day^?1) with a 2.5% increment in Trial I; 1.25–7.50% BW day^?1 with a 1.25% increment in Trial II; and 2.0–7.0% BW day^?1 with a 1.0% increment in Trials III and IV. Four replicates with 50 fry per tank in Trials I‐III and 30 fry per tank in Trial IV were assigned randomly to each feeding rates. The final body weight, specific growth rate, feed efficiency, protein retention, and whole‐body moisture, lipid, and energy contents were significantly (P < 0.05) affected by the feeding rates. The optimum feeding rates determined by the broken‐line model were 7.1, 5.7 and 5.3% BW day^?1 for Trials I, II and IV, when the fry were 5, 6 and 8 weeks after their initiation of exogenous feeding, respectively.     

Determination of the optimum transfer time of kutum (<Emphasis Type="Italic">Rutilus frisii kutum</Emphasis>) larvae from live food to artificial dry feed

Kutum Rutilus frisii kutum is known as a valuable commercial species in the southern part of Caspian Sea. Artificial rearing of fry has been introduced as an alternative to supply kutum fry in order to restock the kutum population in the Caspian Sea. The aim of this study was to find the suitable time to transfer kutum larvae from live food to artificial feed. The experiment began on day 3 post- hatching and lasted for 21 days. Mean initial weight of larvae was 4.5 mg. Five experimental groups including Group A (zooplankton alone for 21 days), Group B (12 days zooplankton + 9 days artificial feed), Group C (8 days zooplankton + 13 days artificial feed), Group D (4 days zooplankton + 17 days artificial feed) and Group E (artificial feed alone for 21 days) were considered for this experiment. According to the obtained results, the specific growth rate of kutum larvae varied from 8.01 to 13.58% day⁻¹, and the highest and lowest specific growth rate were found in A and E treatments, respectively. The lowest mean body weight (24.6 mg) was found in larvae fed on artificial feed for 21 days. However, survival rates of kutum larvae fed mixed zooplankton for 8 and 12 days (85.83 and 89.33%, respectively) were comparable with those of larvae fed live food during the entire experiment (91.6%). The lowest survival rate (69.16%) was found in larvae fed artificial feed during the entire experiment.     

Draining system and feeding rate during the initial development of Lophiosilurus alexandri (Steindachner, 1877), a carnivorous freshwater fish

This study evaluated the efficiency of the drainage system during the larviculture of Lophiosilurus alexandri. Moreover, we assessed the best feeding rate after feed training for juvenile production. The study was performed in three phases over 87 days. In phase 1 (40 days), larvae were fed live food and posteriorly submitted to feed training in two drainage systems: water drained on the surface (DS), and water drained into a tank column (DI). In the second phase (30 days), using only the DS system juveniles were fed a formulated diet at feeding rates, 2, 4, 6 and 8% of body wet weight. In the third phase (17 days), the fish from the second phase were fed until apparent satiation. At the first phase, the animals in the DS system exhibited greater survival rates and growth. The best feeding rate for daily weight gain, specific growth rate (SGR) and mean body weights were similar: 5.57, 5.13 and 5.68% respectively. In the third phase, an increased SGR was observed in the treatment groups that received lower feeding rates in the second phase (2 and 4%), which could indicate a possible compensatory growth rate.