Survival Of Fingerlings Research Articles

Effect of azolla-incorporated diets on the growth and survival of Labeo fimbriatus during fry-to-fingerling rearing

AbstractAn experiment of 75 days duration was conducted in fertilized outdoor circular cement tanks (1,000 L) with soil base for evaluating the growth and survival of Labeo fimbriatus fry fed with pelleted feed containing varied levels of dried azolla (Azolla pinnata). The Control feed contained 45% groundnut oilcake plus 45% rice bran and 10% finger millet flour added as binder for pelleting. Dried azolla powder was incorporated into the feed at 10, 20, 30 and 40% levels, replacing the groundnut cake and rice bran proportionately. L. fimbriatus (mean length 2.42 cm) fry were stocked in all the tanks at 30 m−3. The fish were fed 10% of body weight during the first month, followed by 7% during the second month and 5% during the last 15 days. Incorporation of azolla did not affect (p > 0.05) the water quality, growth and survival of fingerlings at harvest. Incorporation of azolla in the diet reduced the cost of feed (Rs. per 100 g biomass; Rs: Indian rupee, INR; 1 INR ≈ 0.015 EUR) from 3.35 to 2.53, with a ...

Comparative Study of Mustard Oil Cake and Soybean Meal Based Artificial Diet for Rohu, Labeo rohita (Ham.) Fingerlings

An experiment was conducted to evaluate the nutritive potential of soybean meal and mustard oil cake based diets for rearing of Labeo rohita fingerlings under pond condition at the Bangladesh Agricultural University, Mymonsingh during 2008. Three diets designated as treatments were formulated and fed to the stocked fingerlings. Studies have revealed an increase in final weight, average live weight gain, specific growth rate (SGR), lower food conversion ratio (FCR), protein efficacy ratio (PER) and apparent net protein utilization (ANPU%) and survival of fingerlings fed on diet D3, a soybean meal based diet. Carcass composition also revealed high protein and lipid in fish fed on the diet D3. DOI: http://dx.doi.org/10.3329/agric.v11i1.15244 The Agriculturists 2013; 11(1) 61-66

Growth and Survival of Fingerlings of a Threatened Snakehead, Channa striatus (Bloch) in Earthen Nursery Ponds

Nursery rearing of a high-valued threatened snakehead fish, Channa striatus was studied in relation to varying stocking densities in earthen ponds. The experiment was conducted for eight weeks in nine earthen nursery ponds having an area of 0.012 ha with an average depth of 0.8 m. Fry produced from natural propagation was first reared in indoor cemented cisterns with hatched Artemia cyst as live food for 10 days and then stocked at 150,000, 200,000 and 250,000 ha-1 in treatment-1 (T1), treatment-2 (T2) and treatment-3 (T3), respectively. At stocking, mean length and weight of fry was 1.17±0.18 cm and 0.15±0.03 g, respectively. Fry in all the experimental ponds were fed with a supplementary feed comprising of fish meal (50%) and mustard oil cake (50%) at the rate of 5-8% of the estimated body weight. In addition, chopped trash fishes were supplied at the rate of 5% of the estimated biomass daily, till harvest. The physicochemical parameters of water and plankton were monitored simultaneously and were within the acceptable range for fish culture. Growth parameters (final weight, final length, weight gain, length gain and specific growth rate) and survival of fingerlings were significantly higher in T1 than those in T2 and T3, respectively. Feed Conversion Ratio (FCR) was significantly lower in T1 followed by T2 and T3 in that order. Significantly higher survival of fingerlings was obtained in T1 than those in T2 and T3. Overall, highest growth and survival were obtained from T1 where stocking density of fry was 150,000 ha-1. Hence, of the treatments evaluated, stocking density of 150,000 fry ha-1 appears to be the most efficient stocking density for rearing of C. striatus fingerlings in earthen nursery ponds. This study represents the first successful attempt to produce fingerlings of the threatened C. striatus in nursery ponds, the findings of which might immensely be helpful towards the protection of snakehead from extinction as well as for its conservation, stock enhancement and rehabilitation.

Partial Replacement of Dietary Animal Protein with Vegetable Protein Blend with Different Proportions of Glucosamine on Growth, Feed Efficiency, Body Composition and Survival of Fingerlings of Asian Catfish (Clarias batrachus)

A 12-week feeding trials was conducted to evaluate the use of animal and plant protein, in combination with glucosamine source for Asian catfish, Clarias batrachus (average weight 2.1–2.6 g). This study was performed to evaluate the effect on fish growth performance by replacing animal protein with a blend of vegetable protein sources. In experiment, six (40.45–43.51 % crude protein, 16.45–16.76 kJ/g energy, and crude lipid 5.01–6.69 %) practical diets were formulated. The animal and plant protein component of the diets was progressively added with glucosamine 0.0 %, 0.5 %, 5.0 % and 10.0 % with fish meal, silkworm pupae, soybean meal (SBM) and casein (F1, PAG 0:100:0.5; F2, PAG 0:100:5.0; F3, PAG 0:100:10.0; F4, PAG 25:75:0.5; F5, PAG 25:75:5.0; F6, PAG 25:75:10.0). The experimental diets were fed to triplicate groups of fingerlings ad libitum and results were compared with control feed (natural feed). Growth performance and feed utilization efficiency of catfish, fed diets with animal protein are better than those of plant protein supplemented feeds. After 12-week study the final weight gain recorded as 18.6, 19.7, 19.9, 16.3, 15.2, 15.6 and 13.1 g in control fed fishes. The best growth among the animal protein group (F1–F3) were recorded as 745.5 %, 838.1 % and 765.2 % respectively. The growth percentage in 25 % replaced feeds (F4, PAG 25:75:0.5; F5, PAG 25:75:5.0; F6, PAG 25:75:10.0), recorded as 579.2 %, 484.6 % and 609.1 % respectively whereas in control it was 469.6 %. The results suggests that the growth is better in total animal protein feeds and the best growth (p < 0.05) recorded in the feed incorporated with 10 % glucosamine. The data on growth and feed conversion ratio (FCR) were considered animal protein content of the diet along with glucosamine has better growth performances. The survival was recorded in F1–F6 as 88 %, 83 %, 76 %, 78 %, 80 % and 75 % respectively and in control it is recorded as 68 %. The hepatosomatic and viscerosomatic indices ranged between 0.78–1.51 and 1.9–3.03 respectively in F1 to F6. The feed efficiency in terms of FCR recorded as 2.34–2.95 among all the feeding trials. Results indicate that animal protein rich diets with glucosamine were much acceptable than natural diets for Asian catfish, C. batrachus and the potential for replacing animal protein with SBM in the diets of fish need more evaluation along with synergistic approach of incorporating glucosamine. Inclusion of plant protein blend affected growth performance and reduced digestibility, but was not compensated by increased feed intake.

Stocking density effects on growth and production of the threatened silurid catfish,Mystus cavasius(Hamilton) fingerlings in nursery ponds

The fingerling-rearing experiment of the threatened catfish, Mystus cavasius was carried out at different stocking densities in earthen nursery ponds. Twelve-day-old fry were stocked at 200 000 ha−1 in treatment-1 (T1), 250 000 ha−1 in treatment-2 (T2) and 300 000 ha−1 in treatment-3 (T3) respectively. The mean length and weight of fry at stocking was 1.24 ± 0.25 cm and 0.11 ± 0.04 g respectively. Fry in all the experimental ponds were supplemented with SABINCO nursery feed for the first 14 days and starter-I feed for days 15–56. The physico-chemical parameters and plankton population of pond water were within the suitable level for fish culture. Growth in terms of final weight, final length, weight gain, length gain and specific growth rate and survival of fingerlings were significantly higher in T1 than those in T2 and T3. Feed conversion rate was significantly lower in T1 followed by T2 and T3 in that order. Significantly higher number of fingerlings was produced in T3 than that in T2 and T1. Even then, consistently higher net benefits were obtained from T1 than those from T3 and T2. Among the treatments evaluated, 200 000 fry ha−1 was the best stocking density considering the highest growth, production and net benefits of fingerlings of M. cavasius in nursery ponds.

Comparative Cost Analysis of Hybrid Striped Bass Fingerling Production in Ponds and Tanks

AbstractYear‐round production of hybrid striped bass (female white bass Morone chrysops × male striped bass M. saxatilis) fingerlings would allow food fish growers to sell their product throughout the year, which would improve the consistency of market supply and cash flow for the farm. However, pond production of fingerlings is seasonal and precludes year‐round supply. Tank culture methods have been developed to produce hybrid striped bass fingerlings indoors throughout the year, but the associated costs have not been estimated or compared with pond production costs. Economic engineering techniques were used to estimate production costs for phase I hybrid striped bass fingerlings in ponds (0.4, 1.2, or 2.4 ha) and tanks (945, 2,457, or 5,670 L) for production scales of 50,000, 100,000, 250,000, 500,000, 1,000,000, or 2,000,000 fingerlings per year. The results demonstrated that there are economies of scale in terms of the volume of production and the size of the production unit. Overall, pond production per 1,000 fingerlings was substantially less expensive than tank production, even accounting for the increased number of annual production cycles in tanks. Production costs were sensitive to survival rates and can be reduced by 7–14% and 5–11% for each 5% improvement in survival in ponds and tanks, respectively. Substituting microcyst brine shrimp for rotifers Artemia spp. in the diet may have the potential to reduce the tank costs of producing hybrid striped bass depending on fingerling survival beyond 14 d posthatch. Additional research is needed to improve overall fingerling survival both during the early fry rearing stage and after training to dry feed.

Efeito do extrato de Melia azedarach sobre a predação de alevinos de carpa comum (Cyprinus carpio) por larvas de Neuraeschna (Odonata: Aeshnidae)

The presence of larvae of predator insects in fish farming ponds is one of the factors that contribute to the reduction of the survival of fingerlings and consequently to the decrease of production profits. Dragonflies, which belong to the order Odonata and lay their eggs directly in the water, are among the insects that have a harmful effect on fish farming. The larvae are starving carnivore: they predate post-larvae fish and fingerlings and thus become economically relevant plagues. The objective of this work is to study the occurrence of odonata larvae in fish ponds and evaluate the effect of vegetal extracts adsorved in silica to control odonata larvae predation on common carp. A total of 126 larvae (INSECTA: ODONATA) of the suborder Anisoptera were registered in the monitored ponds. Of those, 80 belonged to the family Aeshnidae and 46 to the Libellulidae. The genera Neuraeschna was dominant in the three sampled ponds and was used in the biological tests. During the tests of predation of fingerlings of common carps (Cyprinus carpio) by the Neuraeschna larva, the daily consumption was of 5,2 and 7,2 fingerlings in the treatments with and without EEC, respectively.). The adoption of Good Practises in Aquaculture and the sustainability of fish farming request the adoption of natural products.

Precision of Striped Bass Fry Density Estimates

AbstractMany fisheries for striped bass Morone saxatilis in the United States are supported by stocking hatchery‐reared fish. Fingerlings are usually obtained by spawning adults in captivity, collecting fry in large (25–100‐L) collection containers (vats), moving them to rearing facilities (e.g., earthen ponds and raceways), and subsequently harvesting the fish that remain after some predetermined period. The number of fry stocked is estimated, and the accuracy and precision are seldom known or reported. The effect of treating fry stocking estimates as “error free, complete counts” on survival and production estimates is, therefore, also unknown. The objective of this study was to document and determine the statistical precision of the procedures used at Texas Parks and Wildlife Department's Dundee Fish Hatchery through the 1990s (standard procedures still in use at many hatcheries) for estimating fry densities in vats. The precision of fry density estimates was directly correlated with the mean density and sample volume. Such estimates could be improved by reducing the water volume (especially when densities are low) in vats and using a standard sample volume (at least 15 mL) instead of adjusting the sample volume based on visual inspection of fry in vats. The number of samples could be reduced from 10 to 8 without substantially affecting precision. Further, the practice of removing the highest and lowest sample values should be discontinued. The resulting precision of subsequent fingerling survival and production statistics could benefit from these changes without a substantial increase in data analysis.Received August 5, 2010; accepted October 4, 2010

Growth and production performance of threatened snakehead fish, Channa striatus (Bloch), at different stocking densities in earthen ponds

Production trials of threatened snakehead fish (Channa striatus) were carried out under different stocking densities in earthen ponds of Bangladesh. The average weight and length of the fingerlings during stocking was 17.63 ± 1.23 g and 13.21 ± 0.52 cm. Fingerlings were stocked at 5000 ha−1 in treatment-1 (T1), 6250 ha−1 in treatment-2 (T2) and 7500 ha−1 in treatment-3 (T3) respectively. Fish in all the experimental ponds were fed with supplementary feed comprising of fish meal (30%) and mustard oilcake (70%) at the rate of 3–6% of estimated body weight two times per day. In addition, trash fish were supplied at the rate of 2–3% of the estimated biomass on each alternate day. In situ water quality parameters of the pond were within the suitable range for fish culture. The growth and survival of fingerlings were significantly higher in T1 than in T2 and T3. The food conversion ratio was significantly lower (P<0.05) in T1 than in T2 and T3. The estimated gross and net production of fish was higher in T1, followed by T2 and T3. Overall, the highest growth, survival and production were obtained from T1. Therefore, it could be concluded that of 5000 fingerlings ha−1 is the most suitable stocking density for culturing C. striatus under a monoculture system in the earthen ponds for better production.

Effects of dietary lipid levels on growth performance, feed utilization and fatty acid composition of juvenile Japanese seabass (Lateolabrax japonicus) reared in seawater

Triplicate groups of 40 Japanese seabass Lateolabrax japonicus (initial weight, 11.3 ± 0.4 g) reared in seawater (salinity, 30.0–33.0 g L−1) were fed with five isonitrogenous (41.3 ± 0.2% crude protein) and isoenergetic (18.5 ± 0.3 MJ kg−1) experimental diets formulated with increasing lipid levels (4.3, 8.4, 12.2, 15.8 and 20.1% lipid) for 10 weeks. Survival throughout the feeding experiment ranged from 87.5 to 100%, but the survival of fingerlings fed with the 4.3% lipid diet was significantly lower than the rest of the diets. At the end of the feeding experiment, fish fed with 12.2% lipid diet showed optimal growth performance (P < 0.05). Lipid contents of whole body, liver and muscle increased in parallel with the increase in dietary lipid levels. Viscerosomatic index (VSI), hepatosomatic index (HSI) and muscle lipid content were higher in 20.1% lipid group than those in the rest of the lipid level groups indicating that viscera and muscle tissues played important contributions to body lipid deposition. High proportions of 18:1n-9, eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA), and low concentrations of n-6 polyunsaturated fatty acids (PUFAs) occurring in liver and muscle, to some extent, reflected fatty acid (FAs) composition in the experimental diets.

Genetic architecture of rainbow trout survival from egg to adult

Survival from birth to a reproductive adult is a challenge that only robust individuals resistant to a variety of mortality factors will overcome. To assess whether survival traits share genetic architecture throughout the life cycle, we estimated genetic correlations for survival within fingerling stage, and across egg, fingerling and grow-out stages in farmed rainbow trout. Genetic parameters of survival at three life cycle stages were estimated for 249 166 individuals originating from ten year classes of a pedigreed population. Despite being an important fitness component, survival traits harboured significant but modest amount of genetic variation (h2=0.07-0.27). Weak associations between survival during egg-fry and fingerling periods, between early and late fingerling periods (rG=0.30) and generally low genetic correlations between fingerling and grow-out survival (mean rG=0.06) suggested that life-stage specific survival traits are best regarded as separate traits. However, in the sub-set of data with detailed time of death records, positive genetic correlations between early and late fingerling survival (rG=0.89) showed that during certain years the best genotypes in the early period were also among the best in the late period. That survival across fingerling period can be genetically the same, trait was indicated also by only slightly higher heritability (h2=0.15) estimated with the survival analysis of time to death during fingerling period compared to the analysis treating fingerling survival as a binary character (h2=0.11). The results imply that (1) inherited resistance against unknown mortality factors exists, but (2) ranking of genotypes changes across life stages.

The Effect of the Dye Aquashade® on Water Quality, Phytoplankton, Zooplankton, and Sunshine Bass, Morone chrysops×M. saxatilis, Fingerling Production in Fertilized Culture Ponds

Rooted macrophytes make harvesting fingerling fish difficult because they can smother fish or tangle in the seines during harvest. Aquashade®, a dye, is used to reduce macrophyte growth. Fingerling culturists are reluctant to use it because it may reduce phytoplankton concentrations and zooplankton food supplies of larval fish. Aquashade was applied at 4 mg/L (twice the recommended rate) to three ponds when filled and to three ponds when fry were started on prepared feed. Three ponds served as a control. All ponds were stocked with sunshine bass larvae at 15,000/0.04 ha. Water quality and plankton were monitored daily until harvest. Few differences were found among treatment ponds for water quality, chlorophyll a, primary productivity, phytoplankton and zooplankton concentrations, or weight of rooted macrophytes. Unionized ammonia and pH increased to potentially harmful levels in ponds that did not receive the dye. No differences were found in the number, total weight or percent survival of fingerlings harvested. No differences in average individual total length, total weight, or coefficient of condition were found either. At the concentration of dye used, the dye was not effective for rooted macrophyte control but may offer fish some protection from high pH or unionized ammonia concentrations.

Cloreto de sódio, benzocaína e óleo de cravo-da-índia na água de transporte de tilápia-do-nilo

Testou-se a ação de diferentes concentrações de cloreto de sódio, benzocaína e óleo de cravo-da-índia na sobrevivência de alevinos e juvenis de tilápia (Oreochromis niloticus), linhagem chitralada, por 5 horas visando ao transporte. Utilizaram-se 1.350 alevinos (9,74 ± 0,04 g e 6,79 ± 0,01 cm) e 270 juvenis (29,6 ± 0,06 g e 11,52 ± 0,01). Os peixes foram mantidos em jejum por 24 horas em quatro caixas de amianto (500 L) com aeração constante. Em seguida, os peixes foram distribuídos em 54 sacos plásticos, capacidade para 5 L e mantidos em soluções de: cloreto de sódio nas concentrações de (0; 4; ou 8 g/L), benzocaína (0; 20; ou 40 mg/L) e óleo de cravo (0; 2; ou 5 mg/L). O delineamento foi em blocos casualizados, com três repetições, em arranjo multifatorial, com três fatores: substâncias, peixes e concentrações de cada substância em estudo. Mensuraram-se, no início, os parâmetros oxigênio dissolvido, temperatura, pH, salinidade e amônia e, ao final do experimento, a glicose dos peixes. Maiores níveis de glicose foram registrados nos juvenis mantidos na água com óleo de cravo e cloreto de sódio. Não foi observada diferença significativa na sobrevivência entre os tipos de peixes e as substâncias. Entretanto, as dosagens de cloreto de sódio e benzocaína ocasionaram diferenças significativas na taxa de sobrevivência. A sobrevivência foi baixa nos alevinos com 0 g/L de cloreto de sódio e diferiu das dosagens 4 e 8 g/L. O óleo de cravo promoveu resultados similares, em todas as dosagens e substâncias, de taxas de glicose. Ao final do experimento, a sobrevivência foi satisfatória, com média geral de 97,26%, comprovando que as três substâncias podem ser usadas no transporte de alevinos e juvenis durante 5 horas. Sugere-se o cloreto de sódio por seu melhor custo-benefício.

Effects of Water Replacement Frequency on the Growth and Survival of Heterobranchus Longifilis Valenciennnes, (1980) Fingerlings Reared

The effect of water replacement frequency on growth and survival of fingerlings (4.21±0.39 mean weight) of African catfish Heterobranchus longifilis was investigated in concrete tanks of dimension 2m x 2m x1m (4m²)over a period of sixty days. There were five treatments namely: Treatment A = daily water replacement; Treatment B = replacement every two day; Treatment C = replacement every three days; Treatment D = replacement every six day; Treatment E = no water replacement (control). The fish were fed with well balanced artificial diet at 3% body weight daily at 0800hrs and 1700hrs. The results show that fingerlings in treatment D had the best specific growth percentage of 5.32% and feed conversion ratio of 1:3.35 while treatment E was poorest with specific growth percentage of 1.33% and feed conversion ratio of 1: 9.20.Treatment A had 100% survival while treatment E had the least survival rate of 30%. Generally it was observed that the lesser the frequency of water replacement the better the growth performance while the reverse was the case with survival rate of the fish fingerlings. It is recommended that an every six day and upward of water replacement frequency be adopted to avoid the problem associated with stress. Journal of Agriculture and Food Sciences Vol. 4 (2) 2006: pp. 109-114

Evaluation of Growth, Survival, and Production of an Endangered Fish, Labeo gonius (Hamilton) Fingerlings in Earthen Nursery Ponds

ABSTRACT Nursery rearing of an endangered fish, Labeo gonius (Ham.) was studied in relation to varying stocking densities in earthen ponds. The experiment was conducted for 8 weeks in nine nursery ponds having an area of 0.012 ha with an average depth of 1 m. Four-day-old hatchling stocked at 0.6 million/ha was designated as treatment-1 (T1), 0.8 million/ha as treatment-2 (T2) and 1.0 million/ha as treatment-3 (T3), respectively. At stocking, all hatchlings were of same age group with a mean length and weight of 0.66 ± 0.08 cm and 0.001 ± 0.0001 g, respectively. Hatchlings in all the experimental ponds were given wheat flour for the first 7 days, finely ground mustard oilcake for the next 7 days and a mixture of rice bran, and mustard oilcake (1:1) for days 15 to 56. The rate of feeding was 20 kg/million hatchling/day for the first two weeks, 25 kg for the second two weeks, 30 kg for the third two weeks and 35 kg for the fourth two weeks. The physicochemical parameters of water and plankton were monitored simultaneously and were within the acceptable range for fish culture. Growth parameters (final weight, final length, weight gain, length gain and specific growth rate) and survival of fingerlings were significantly higher in T1 (0.6 million hatchling/ha) than those in T2 (0.8 million/ha) and T3 (1.0 million/ha), respectively. Feed conversion ratio (FCR) was significantly lower in T1 followed by T2 and T3 in that order. The estimated gross and net productions of fingerlings were significantly higher in T1 than in T2 and T3, respectively. Significantly higher number of fingerlings was produced in T3 than those in T2 and T1. Despite this, consistently higher net benefits were obtained from T1 than from T3 and T2. Overall, highest growth, survival, production and benefits were obtained from T1 where stocking density of hatchlings was 0.6 million/ha. Hence, of the treatments evaluated, stocking density of 0.6 million hatchling/ha appears to be the most efficient stocking density for rearing of L. gonius fingerlings in earthen nursery ponds.

Growth and survival of hybrid catfish fingerlings under three dietary treatments in concrete tanks

Fingerlings of African catfish (Clarias gariepinus x Heterobranchus longfilis) were reared in concrete tanks under three dietary treatments for 60 days. Tadpole meal produced the highest fingerling survival rate (90%), with a mean weight value of 2.68g at harvest. The best growth results were obtained among the fish that were fed on fresh tilapia meal, but this treatment also had the lowest fish survival rate (52%). An equal mixture of tadpole and tilapia meal gave fish mean weight value of 2.65g and a survival rate of 80%. Keywords: Hybrid, Catfish, Tadpole, Tilapia AJAZEB Vol. 6 2004: pp. 76-80

Effect of stocking density on survival and growth of endangered bata, Labeo bata (Hamilton–Buchanan) in nursery ponds

Effect of stocking densities on the growth, survival and production of bata, Labeo bata fry and fingerlings were tested in a single-stage nursery rearing system. The experiment was conducted over a 7 weeks period in nine 0.028 ha earthen nursery ponds. Four-day-old hatchlings stocked at 0.60 million ha − 1 was designated as treatment T 1, 0.80 million ha − 1 as treatment T 2 and 1.0 million ha − 1 as treatment T 3. At stocking, all hatchlings were of same age with a mean length and weight of 1.01 ± 0.04 cm and 0.011 ± 0.002 g, respectively. Hatchlings in all the treatments were fed with a mixture of mustard oil cake, rice bran, wheat bran, and fish meal in 40:25:25:10 proportions (32.80% crude protein) from days 1 to 49 days. The water transparency, pH, dissolve oxygen and total alkalinity were found to be in the range of 24.33–47.48 cm, 7.3–8.8, 3.10–5.62 mg L − 1 and 104.13–140.58 mg L − 1 , respectively. The plankton level in all treatments was found to be at optimum level. Highest weight gain (6.76 ± 0.69 g) was observed in treatment T 1 and lowest (3.13 ± 0.34 g) in treatment T 3. Final length, final weight and survival of fingerlings also followed the same trends as weight gain. Fingerlings in treatment T 1 produced significantly higher specific growth rate (3.53 ± 0.23) than treatment T 2 and T 3. Feed conversion ratio was significantly lower in T 1 (0.32 ± 0.01) than T 2 and T 3. Significantly higher number of fingerlings was produced in treatment T 3 than in treatment T 2 and T 1, respectively. Despite of this, consistently higher net benefits were found from treatment T 1 than from treatment T 2 and T 3. Overall, highest growth (6.77 ± 0.66 g), survival (80.15 ± 0.85%) and net benefits of fingerlings were obtained at a density of 0.60 million hatchlings ha − 1 . Therefore, of the three stocking densities, 0.60 million hatchlings ha − 1 appear to be most suitable stocking density for nursing and rearing of bata fry and fingerlings in single-stage nursery system.

Effects of dietary vitamin C on immunity, growth and survival of Indian major carp Labeo rohita, fingerlings

An 8-week feeding trial was conducted to evaluate the efficacy of dietary L-ascorbic acid (AA) dosages on immunity, growth and survival of the fingerlings of Labeo rohita. AA was supplemented at 0, 100, 200 and 500 mg kg )1 basal diets. Each diet was fed for 8 weeks to duplicate groups of fingerlings of rohu with initial body weight of 35 ± 5 g. Selected biochemical and haematological analyses were evaluated every second week. At the end of the feeding trial of 56 days, fish were divided into two subgroups under each major treatment group for challenge with two pathogens, Aeromonas hydrophila and Edwardsiella tarda. The mortality (%) and agglutinating antibody titre were recorded on 28th day postchallenge. Non-specific immune parameters like superoxide anion production, lysozyme activity and complement activity increased independently of the levels of AA in the diet. Whereas phagocytic ratio, phagocytic indices, lymphokine production indices and serum bactericidal activity were better in the group of fish fed with 200 mg AA kg )1 feed for 42 days. However, growth parameters such as specific growth rate, feed conversion ratio and survival were better in the group of fish fed with the highest level of AA through feed for 56 days. These data indicated that elevated levels of dietary AA could be recommended for optimum immunity, growth and survival of fingerlings of L. rohita.

Effect of Multiple‐batch Channel Catfish, Ictalurus punctatus, Stocking Density and Feeding Rate on Water Quality, Production Characteristics, and Costs

Abstract To quantitatively define relationships among stocking densities, feeding rates, water quality, and production costs for channel catfish, Ictalurus punctatus, grown in multiple‐batch systems, twelve 0.1‐ha earthen ponds were stocked at 8,600, 17,300, 26,000, or 34,600 fingerlings/ha along with 2,268 kg/ha of carryover fish. Fish in all ponds were fed daily to apparent satiation using 32% protein floating feed. Temperature and dissolved oxygen in each pond were monitored twice daily; pH weekly; nitrite‐N, total ammonia nitrogen, and Secchi disk visibility every 2 wk; nitrate‐N, chlorophyll a, total nitrogen, total phosphorus, and chemical oxygen demand monthly; and chloride every other month. The costs of producing channel catfish at different stocking densities were estimated. There were no significant differences (P &gt; 0.05) as a result of stocking density among treatment means of (1) gross or net yields, (2) mean weights at harvest, and (3) growth or survival of fingerlings (24–36%) and carryover fish (77–94%). Mean and maximum daily feeding rates ranged from 40 to 53 kg/ha/d and 123 to 188 kg/ha/d, respectively, and feed conversion ratios averaged 1.75. There were no differences in any feed‐related parameter as a result of density. Water quality variables showed few differences among densities at samplings and no differences when averaged across the production season. Yield of fingerlings increased as stocking density increased with significant differences between the two highest and the two lowest stocking densities. Breakeven prices were lower at the higher stocking densities as a result of the higher yield of understocked fish and similar mean individual fish weights produced at these higher stocking densities. Overall, varying stocking densities of fingerlings in multiple‐batch systems had little effect on production efficiency and water quality. Additional research on managing the population structure of carryover fish in commercial catfish ponds may be warranted.

Effect of stocking density on survival and growth of critically endangered mahseer, Tor putitora (Hamilton), in nursery ponds

Effects of stocking densities on the growth, survival and production of mahseer ( Tor putitora) fingerlings were examined in a single-stage nursery-rearing system. The experiment was conducted for 8 weeks in six earthen nursery ponds having an area of 0.012 h each. Four-day-old hatchlings stocked at 0.6 million/ha was designated as treatment-1 (T 1), 0.8 million/ha as treatment-2 (T 2) and 1.0 million/ha as treatment-3 (T 3). At stocking, all hatchlings were of same age group with a mean length and weight of 1.18 ± 0.04 cm and 0.012 ± 0.003 g, respectively. Hatchlings in all the treatments were fed with Saudi Bangla (SABINCO) commercial fish feed viz., nursery (32.06% crude protein) for the first 14 days and starter-I (31.53% crude protein) from days 15 to 56. Physico-chemical parameters (temperature, secchi disc transparency, dissolved oxygen, pH and total alkalinity) and plankton populations (phyto- and zooplankton) were at the optimum level for fish culture. Highest weight gain was observed in T 1 and lowest in T 3. Final length, final weight and survival of fingerlings also followed the same trends as weight gain. Fingerlings in T 1 produced significantly higher specific growth rate than T 3, but not than T 2. Feed conversion ratio was significantly higher in T 1 followed by T 2 and T 3 in that order. Significantly higher number of fingerlings was produced in T 3 than in T 2 and T 1, respectively. Despite this, consistently higher net benefits were obtained from T 1 than from T 3 and T 2. Overall, highest growth, survival and benefits of fingerlings were obtained at a density of 0.6 million hatchling/ha. Hence, of the three stocking densities, 0.6 million hatchling/ha appears to be the most suitable stocking density for rearing of mahseer fingerlings in single-stage nursery system.