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1.
Five isonitrogenous and isocaloric diets were fed to juvenile cobia, to assess the relative contribution of different proteins (fish meal, soybean meal, corn gluten and beer yeast) to the growth of cobia. The dietary effects on nitrogen and carbon turnover and on the isotopic diet‐consumer discrimination factors (Δ15N and Δ13C) were also assessed. Growth results showed that the final body weight, growth rate, feed conversion ratio and protein efficiency ratio of cobia fed diets with alternative protein were significantly lower (P < 0.05) than cobia fed diet formulated with 100% fish meal. The estimated half‐lives of nitrogen and carbon ranged between 9–11 days and 6–8 days, respectively, with significant differences among treatments (P < 0.05). Δ15N ranged between 0.0–1.2‰ and ?0.1–1.6‰ in whole fish and muscle and Δ13C ranged between 3.8–5.1‰ and 4.0–5.1‰ in whole fish and muscle respectively. Diets were formulated with low levels of dietary nitrogen (10%) supplied by alternative protein sources substituting fish meal. The relative contributions of the dietary nitrogen supplied from these sources to the growth of whole fish and muscle tissue ranged between 4.9–5.2% and 5.9–7.7% respectively. Results indicated that growth accounted for the majority of observed isotopic change in animals under all treatments. In whole animals and muscle tissue, isotopic change due to metabolism occurred faster for carbon stable isotopes than for nitrogen stable isotopes. Cobia fed diets formulated with alternative proteins showed reduced nitrogen turnover rate and increased Δ15N.  相似文献   

2.
Nile tilapia (1.20 g) were fed for 56 days in five treatments (FM100 containing only fish meal [FM] as a protein source; soybean meal (SBM) replace 25%, 50%, 75% and 100% of FM protein in the diets of FM75, FM50, FM25 and FM0, respectively) to assess the effects of dietary protein sources on growth, turnover half‐life of nitrogen and carbon stable isotopes (δ13C and δ15N) in muscle, isotope discrimination factors (Δ15N and Δ13C), and the relative contribution of protein sources to muscle growth. Results showed that the final body weight, weight gain and specific growth rate of fish fed diet FM25 were significantly higher than other treatments (p < .05). By day 35, fish under all treatments reached isotopic equilibrium, and the equilibrium values consistently increase as a function of stable isotope values in diets. Growth accounted for most isotopic changes in muscle and resulted in significantly shorter half‐lives of nitrogen and carbon in FM25 (p < .05). The Δ15N of FM25 and Δ13C of FM0 were significantly lower than other treatments (p < .05). The proportional contributions of SBM protein were significantly higher than their respective levels in FM75 and FM25 (p < .05), indicating a preferential incorporation of nitrogen from the SBM in muscle tissue.  相似文献   

3.
An experiment was conducted to determine the growth efficiency of lotus (Nelumbo nucifera Gaertn) on nutrient capture in farming systems of yellow catfish (Pelteobagrus fulvidraco Richardson). Three treatments, a control treatment of N. nucifera alone (T1), a treatment of N. nucifera‐P. fulvidraco co‐culture (T2) and a treatment of P. fulvidraco alone (T3), were conducted in triplicate. Except pH, conductivity and chemical oxygen demand (CODMn), most of the water quality parameters were significantly lowered by N. nucifera cultivation. Total nitrogen and phosphorus concentrations in the T2 system were 62.2% and 71.6% higher than those in the T1 system respectively; and 31.8% and 59.2% lower than those in the T3 system respectively. The nitrogen and phosphorus release rates were 41.2% and 36.8% in the T2 system, respectively, and 95.6% and 99.1% in the T3 system respectively. 7.31%–21.4% of nitrogen and 3.35%–15.9% of phosphorus were unaccounted. N. nucifera can effectively remove nutrients from water and sediments and may promote the outflow of nutrients. No significant difference in fish or N. nucifera growth performance was observed among the systems. This study indicates that the co‐culture of N. nucifera with P. fulvidraco is an optimal culture system that can increase food production and reduce waste discharge.  相似文献   

4.
This study was undertaken to evaluate the role of polychaete Nereis diversicolor in bioremediation of waste water and its growth performance and fatty acid composition in an integrated culture system with great sturgeon, Huso huso. Three treatments consisting of N. diversicolor fed with H. huso waste (FNW), N. diversicolor fed with fish feed waste (NW), and fish waste without the worm (FW) were considered at water temperature of 23°C for 8 weeks. The obtained results demonstrated that N. diversicolor in the flow‐through system could grow via feeding with the fish waste water. The pure production and survival rate of harvested Nereis in NW treatment were significantly higher than those of FNW treatment (p < .05). However, no significant difference was observed in specific growth rate and weight gain between these two treatments (p > .05). The highest removal efficiency of waste water including total nitrogen (56%), total phosphorus (53%), NO2‐N (91%), NH3‐N (35%), PO4‐P (47%), BOD5 (60%) were seen in FNW treatment. Also, the highest additional efficiency of NO3‐N occurred in FW (37%) treatment. Certain fatty acids specifically 20:5 ω3 (eicosapentaenoic acid [EPA]) and 22:6 ω6 (docosahexaenoic acid [DHA]) were also abundant in Nereis, and analysis revealed some differences due to the diet. These results demonstrated that the promotion of growth by cultured Nereis can enhance the decomposition rate of organic matter in enriched sediment and minimize negative effects in fish farms. These results also suggest that the use of N. diversicolor is an excellent potential candidate for an integrated aquaculture and nutrient recycling including the removal of organic wastes.  相似文献   

5.
A feeding trial was performed to determine the effect of a commercial source of Yucca schidigera and Quillaja saponaria extracts (Nutrafito Plus®), in practical diets, on striped catfish Pangasianodon hypophthalmus growth, feed utilization, body composition, total ammonia‐nitrogen (TAN) excretion and haematological parameters. Four experimental diets were supplemented with Nutrafito Plus® at 0%, 0.01%, 0.02% and 0.03% (diets: control, N01, N02 and N03 respectively). Three replicate groups of striped catfish, with initial mean weight of 1.78 ± 0.05 g, were fed one of the four diets for 12 weeks. The specific growth rate (SGR) and final weight of fish fed diet N03 was significantly higher (P < 0.05) than fish fed the other dietary treatments. The growth performance of fish fed diets N01 and N02 were not significantly different compared to fish fed the control diet. Striped catfish fed diet N03 had improved feed conversion ratio (FCR), net protein utilization (NPU) and protein efficiency ratio (PER) than the control (P < 0.05). The inclusion of the high dietary level of Yucca schidigera and Quillaja saponaria, diet N03, reduced TAN compared to all groups. Dietary inclusion of Yucca schidigera and Quillaja saponaria at all levels investigated did not affect the whole body proximate composition of the striped catfish (P > 0.05). The packed cell volume (PCV) and haemoglobin level in fish fed diet N03 was significantly higher than in the fish fed the control diet. The present study demonstrates that dietary inclusion of Yucca schidigera and Quillaja saponaria induced positive effects on growth performance and haematological parameters and decreased TAN excretion in striped catfish.  相似文献   

6.
Columnaris disease, caused by the bacterium Flavobacterium columnare, is currently the most frequently reported bacterial disease affecting farm‐raised channel catfish in the USA. Common treatments against the disease include the use of medicated feed that has led to emergent antibiotic resistant strains of F. columnare. Nigella sativa (Black cumin) is a medicinal herb commonly used by many cultures as a natural remedy for numerous disorders. Recently, we have discovered the antibacterial activity of N. sativa and its oil extract against F. columnare. In this study, we showed N. sativa oil (NSO) strongly inhibited the growth of all of the strains of F. columnare tested and yielded significantly larger zones of inhibition than those produced by oxytetracyclin. We tested the protective effect against columnaris disease in vivo by incorporating NSO (5%) or N. sativa seeds (NSS) (5%) into fish feeds. Fishes (Ictalurus punctatus and Danio rerio) fed amended diets displayed significantly lower mortality than those fed control diets. Per cent mortalities in control groups ranged from 77% to 44% and from 70% to 18% in zebrafish and channel catfish, respectively. A dose study using different NSS concentrations showed that 5% NSS offered the most protection against columnaris disease in channel catfish.  相似文献   

7.
This study investigated the effects of dietary mono‐ and multiprobiotic strains of Enterococcus faecalis, Lactobacillus fermentum and Leuconostoc mesenteroides on growth performance, intestinal bacteria and body composition of Javanese carp (Puntius gonionotus). Moreover, the effect of storage temperature on lactic acid bacteria (LAB) viability in the feed was studied. Compared to the control group, significant (P < 0.05) effect on weight gain, feed conversion ratio, specific growth rate and protein efficiency ratio of probiotic fed Javanese carp was observed. Inclusion of individual LAB strains in the diet resulted in significantly improved growth performances of Javanese carps compared to fish fed a diet supplemented LAB mixture. The inclusion level of E. faecalis at 107 colony‐forming unit (cfu) g−1 in the diet revealed higher growth performance compared to other treatments. The population levels of LAB in the fish intestine were significantly increased while the levels of Gram‐negative bacteria were significantly decreased compared to the control. No significant variations were observed in the chemical composition of the carcass by probiotics. The viability of LAB in feed was higher when stored at 4 °C compared to 25 °C. It is suggested that E. faecalis has a greater potential for use in improving Javanese carp culture outcomes.  相似文献   

8.
The application of probiotics in food is now widespread and is widely accepted by consumers. Lactic Acid Bacteria (LAB) were isolated from traditional salted fish and then characterized by its ability to inhibit Vibrio parahaemolyticus growth using minimal inhibitory concentration tests. Five out of these strains were identified as Lactobacillus delbrueckii, Lactobacillus casei and three Lactobacillus gasseri by PCR using 16S and 23S rRNA genes. Antibiofilm activity of Lactobacillus spp. extracts were also tested in 96 polystyrene plates. A potential antibiofilm effect was demonstrated as most LAB. Although most LAB extract were able to eradicate pre‐formed biofilm, results demonstrated that five Lactobacillus spp. exhibited a stronger inhibitory effect against V. parahaemolyticus in infected oysters. Vibrio parahaemolyticus viable cells number declined from 106 UFC to 104 UFC after 3 days of incubation with Lactobacillus spp. Probiotic applications, in biological control of seafood associated pathogens can be an alternative solution, providing consumer with a product of good quality owing to the use of non‐toxic compounds. Based on our results, LAB could be used as a bioprotective culture in oyster's depuration to prevent V. parahaemolyticus growth.  相似文献   

9.
Vibrionaceae infections are a major obstacle for marine larviculture; however, little is known about virulence differences of Vibrio strains. The virulence of Vibrio strains, mostly isolated from vibriosis outbreaks in farmed fish, was tested in larval challenge trials with cod (Gadus morhua), turbot (Scophthalmus maximus) and halibut (Hippoglossus hippoglossus) using a multiwell dish assays with single‐egg/larvae cultures. The strains differed significantly in virulence as some caused a high mortality of larva reaching 100% mortality after a few days, while others had no or only marginal effects on survival. Some Vibrio strains were pathogenic in all of the larva species, while some caused disease only in one of the species. Twenty‐nine of the Vibrio anguillarum strains increased the mortality of larvae from at least one fish species; however, pathogenicity of the strains differed markedly. Other Vibrio species had no or less pronounced effects on larval mortalities. Iron uptake has been related to V. anguillarum virulence; however, the presence or absence of the plasmid pJM1 encoding anguibactin did not correlate with virulence. The genomes of V. anguillarum were compared (D. Castillo, P.W. D'Alvise, M. Middelboe & L. Gram, unpublished data) and most of the high‐virulent strains had acquired virulence genes from other pathogenic Vibrio.  相似文献   

10.
A feeding trial was conducted to determine the dietary threonine requirement of juvenile large yellow croaker (Larmichthys crocea). Six diets were formulated containing 45% crude protein with six graded levels of threonine (0.71–2.46% in about 0.35% increment). Each diet was randomly assigned to triplicate groups of 60 juvenile fish (initial body weight 6.00 ± 0.10 g). Fish were fed twice daily (05:00 and 16:30) to apparent satiation for 8 weeks. The result indicated that significant difference was observed in the weight gain among all treatments. Specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER) and nitrogen retention (NR) increased with increasing levels of threonine up to 1.75% diet (P < 0.05), and thereafter, declined. No significant differences in body dry matter, crude protein, crude lipid or ash content were found among dietary treatments. Theronine contents of fish muscle were significantly affected by dietary threonine levels (P < 0.05). Fish fed the diet with 0.71% threonine showed the lowest threonine content (2.94%) in fish muscle, while fish fed the diet with 1.75% threonine had the highest value (3.16%). Other essential amino acid contents of muscle were not significantly different among the dietary treatments. On the basis of SGR, FE or NR, the optimum dietary threonine requirements of juvenile L. crocea were estimated to be 1.86% of diet (4.13% of dietary protein), 1.90% of diet (4.22% of dietary protein) and 2.06% of diet (4.58% of dietary protein), respectively, using second‐order polynomial regression analysis.  相似文献   

11.
The fermented fish silages produced with Streptococcus spp., Lactobacillus brevis, Lactobacillus plantarum, Pediococcus acidilactici and Enterococcus gallinarum, and formic acid silages were compared for production of two discard fish silages (Equulites klunzingeri and Carassius gibelio). The E/NE ratio of spray‐dried fish silages was determined in range of 0.80–1.10 for E. klunzingeri and 0.80–0.90 for C. gibelio silages. Pediococcus acidilactici and En. gallinarum groups had greater antioxidant activity than other silage groups. The DPPH radical scavenging ability was found as 6.14%–14.71% and 6.99%–13.36% for E. klunzingeri and C. gibelio silages, respectively. The OMD, ME and NEL values were determined in range of 69.74%–80.08%, 6.38–8.65 MJ/kg DM and 6.45–7.49 MJ/kg DM, respectively for spray‐dried E. klunzingeri silages and 81.18%–86.62%, 8.97–9.61 MJ/kg DM and 7.61–8.08 MJ/kg DM, respectively, for spray‐dried C. gibelio silages. According to the nutritional and chemical evaluation, spray‐dried fish silages have great potential as a feed components because of high rate of digestibility and nutritious components.  相似文献   

12.
This work compared the effects of different densities of Mugil curema integrated in the rearing of Litopenaeus vannamei in a biofloc system on the yield and ecological performance of the system. For that, an experiment lasting 55 days was conducted. Four groups were evaluated as follows: (a) T0: shrimp reared without mullet, (b) T10: shrimp reared with 22 fish per tank, (c) T20: shrimp reared with 43 fish per tank, and (d) T30: shrimp reared with 65 fish per tank, each treatment with four replicates. The sludge:biomass ratio was higher in the T0 treatment, while the T10–T20 treatments were more efficient, producing more biomass and less sludge. The use of water was 17% more efficient in all treatments with mullet. Mullet survival was higher in the T10 and T20 treatments (mean: 84 ± 8%) than in the T30 (61 ± 5%) treatment. The fish final biomass and yield limits of the system were 0.37 kg and 3.7 kg/m3 respectively. Finally, there was no increase in the total nitrogen output of the system up to the T10 density. In conclusion, it is possible to integrate mullet up to 3.7 kg/m3, increasing the yield in 20% and decreasing water use.  相似文献   

13.
We evaluated the influence of different proportions of 5′‐inosine monophosphate (IMP) and 5′‐guanosine monophosphate (GMP) on growth, feed digestibility and activity of digestive enzymes of turbot Scophthalmus maximus. Weight gain and daily feed intake were significantly higher in S. maximus fed with IMP or GMP, in comparison with fish fed with neither IMP nor GMP. The growth of 0.05% IMP + 0.05% GMP group was the best, and the intestinal digestive function was improved. The addition of IMP and GMP to fish diets significantly increased the apparent feed digestibility coefficient of dry matter and protein, as well as intestinal protease activity. The highest intestinal protease activity was observed in fish fed with 1 g/kg IMP. However, the lipase activity in hepatopancreas decreased significantly after addition of nucleic acid. According to our results, the optimal level of dietary IMP is 1 g/kg, which is in line with most of the growth performance and feed digestibility.  相似文献   

14.
The aim of this research is to evaluate the effects of biofloc system application at different fish density on the nursery production performance and the robustness of African catfish Clarias gariepinus (Burchell) against Aeromonas hydrophila and salinity stress. An economic analysis was also performed to determine the most optimum fish density in biofloc‐based African catfish nursery production. African catfish with an average body weight of 0.96 ± 0.04 g and average body length of 4.20 ± 0.46 cm, respectively, were distributed in 12 units of circular plastic‐lined tanks (1,020 L). The experiment consisted of four treatments in triplicates, that is, a control without carbon source addition at a density of 4 fish/L, and three biofloc treatments at different densities, that is, BFT4 (4 fish/L), BFT6 (6 fish/L) and BFT8 (8 fish/L). Tapioca flour was used as the organic carbon source in biofloc systems and was added at an estimated C/N ratio of 10. Housing the fish in biofloc systems resulted in higher fish growth, more efficient feed utilization, higher fish robustness against A. hydrophila infection and salinity stress, as well as higher profitability of nursery production. Increasing the fish density resulted in higher mortality. However, higher number of fish produced and lower feed conversion ratio were observed in the treatments with higher density (6 and 8 fish/L). In conclusion, the application of biofloc technology at a density of 8 fish/L could be recommended to increase the production and profitability of African catfish nursery culture.  相似文献   

15.
Comparative evaluation of mahua (Bassia latifolia) oil cake (MOC) and castor bean (Ricinus communis) seed (CBS) was tested as piscicides for tilapia (Oreochromis mossambicus) and panchax (Aplocheilus panchax), and residual toxicity test was done on Labeo bata. Delayed response of CBS compared with MOC was evident as first and total mortality of tilapia was encountered at 4th and 10th hour of application, against 26 hr and 42 hr in panchax respectively. Susceptibility of the test fish to the piscicides was highly variable as tilapia was more susceptible than panchax under both the piscicides tested especially in CBS. Residual toxicity decreased polynomialy over time (R2 ≥ 0.99) and reduced to below 10% on day 13–14 in both MOC and CBS treatments. Both MOC and CBS contributed positively to the nutrient pool of water in which CBS provided more nitrogen compared with MOC. N: P ratio of water in CBS treatment increased exponentially to more than 18 indicating phosphorus limitation.  相似文献   

16.
Freshwater bathing is one of the main treatment options available against amoebic gill disease (AGD) affecting multiple fish hosts in mariculture systems. Prevailing freshwater treatments are designed to be long enough to kill Neoparamoeba perurans, the ectoparasite causing AGD, which may select for freshwater tolerance. Here, we tested whether using shorter, sublethal freshwater treatment durations are a viable alternative to lethal ones for N. perurans (2–4 hr). Under in vitro conditions, gill‐isolated N. perurans attached to plastic substrate in sea water lifted off after ≥2 min in freshwater, but survival was not impacted until 60 min. In an in vivo experiment, AGD‐affected Atlantic salmon Salmo salar subjected daily to 30 min (sublethal to N. perurans) and 120 min (lethal to N. perurans) freshwater treatments for 6 days consistently reduced N. perurans cell numbers on gills (based on qPCR analysis) compared to daily 3 min freshwater or seawater treatments for 6 days. Our results suggest that targeting cell detachment rather than cell death with repeated freshwater treatments of shorter duration than typical baths could be used in AGD management. However, the consequences of modifying the intensity of freshwater treatment regimes on freshwater tolerance evolution in N. perurans populations require careful consideration.  相似文献   

17.
We evaluated the effect of different concentrations of 5′‐inosine monophosphate (IMP) and 5′‐guanosine monophosphate (GMP) on the growth, immunity and muscle composition of turbot Scophthalmus maximus. Eight diets (containing no IMP or GMP, or 0.5 g/kg IMP, 1.0 g/kg IMP, 2.0 g/kg IMP, 0.5 g/kg GMP, 1.0 g/kg GMP, 2.0 g/kg GMP, or 0.5 g/kg IMP plus 0.5 g/kg GMP) were prepared. A total of 360 fish (average body weight of 105 g) were randomly selected and placed in groups into 24 plastic aquaria (8 treatments × 3 replicates × 15 individuals per plastic aquaria). The tanks were maintained at the temperature of 15 ± 2°C. The experimental diets were fed for 60 days. The specific growth rate (SGR) was significantly higher in S. maximus fed with IMP or GMP compared with fish fed neither IMP nor GMP. The highest SGR was observed in fish fed with 1.0 g/kg IMP. Supplementation with these dietary nucleotides had a positive, but not significant effect on the activity of superoxide dismutase, alkaline phosphatase and acid phosphatase. There was a significant difference in the moisture and crude lipid content of muscle from S. maximus fed the different diets compared with control fish. The highest moisture content was 83.44 for a diet of 0.5 g/kg IMP plus 0.5 g/kg GMP, which was also significantly higher when compared to fish fed alternative diets. The crude lipid content of S. maximus fed diets containing either IMP or GMP was significantly higher than those fed diets without IMP or GMP. Thus, according to these results, the optimal level of dietary IMP is 1.0 g/kg, which correlates with the largest increase in growth performance of S. maximus.  相似文献   

18.
The effects and commercial implications of aquatic plant addition, and variable prawn stocking density and supply of commercial aquafeed on water quality, prawn production and economic benefit, are investigated in a prawn (Macrobrachium rosenbergii) + plant (Hydrilla verticillata) co‐culture system. Our experimental design includes a control (PM, prawn monoculture without H. verticillata, with 30 prawns/m2) and four treatments with 15% plant cover of total pond area in each replicate. Dissolved oxygen, pH, N, P, total ammoniacal nitrogen, nitrite and nitrate in this co‐culture system were significantly lower than those of PM. Prawn survival (96.2 ± 14.9%), average final weight (68.5 ± 4.9 g) and yield (879.1 ± 102.4 kg/ha) in treatment 20W80%A (20 prawns/m2, 80% of control aquafeed) were obviously greater than in PM and other treatments. Despite small males (SM) and immature females (IF) being predominant in prawn + plant cultures, more than 77.2% of prawns reached or exceeded 40 g on completion of trials, and by six months were of appropriate size for market. We report culture of M. rosenbergii with H. verticillata to be both feasible and profitable. The optimal treatment, a stocking density of 20 prawns/m2 with these plants, enabled reduction of commercial aquafeed to 20% conventional culture levels. For this optimal treatment, we estimate total gross revenue, profit and internal rate of return to be US$ 6,593.3 ± 103.3 ha?1, US$ 3,095.5 ± 42.6 ha?1 and 127.5 ± 20.7% for 20W80%A respectively; we estimate U.S. Dollar (US$) invested generates 3.87 times conventional culture revenue. Co‐culture of M. rosenbergii and plants renders prawn production ecologically and economically feasible on larger farms.  相似文献   

19.
To compare production and economic performance of polyculture systems with different species combinations, a 210‐day trial was carried out. In the first combination (T1), milkfish (Chanos chanos) and mudcrabs (Scylla serrata), and in the second (T2), mullets (Mugil cephalus, Liza tade and Liza parsia at 0.5:0.5:0.5 ratio) and mudcrabs were stocked keeping fish and mudcrabs at 15,000 numbers per ha, respectively, in both treatments. The finfish were fed floating pellet at 2%–3% and mudcrabs were fed fresh and farm made feed at 5%–8% body weight. Growth parameters of mudcrabs were similar in both T1 (407.64 ± 105.78 g) and T2 (418.89 ± 105.24 g), with no significant differences. Among finfish, M. cephalus attained highest final body weight, 241.55 ± 26.44 g followed by milkfish, 200.46 ± 11.82 g whereas lowest growth noticed in L. parsia (63.69 ± 6.62 g). Length–weight analysis of fish indicated negatively allometric growth (b < 3) for grey mullets, parsia and milkfish while L. tade recorded perfect cube low (b = 2.99). Male mudcrabs recorded positive allometric (b = 3.3) and female crab exhibited negative allometric growth (b = 2.68). The total productivity was 4,533 and 3,694 kg/ha with mudcrab contributes 53.69% and 60.56% to the total productivity in T1 and T2 respectively. The economic analysis indicated benefit–cost ratio (BCR) of 1.57 and 1.73 in T1 and T2 respectively with 10% and 35% insignificant increase (p > 0.05) in BCR and profit per kg, respectively, in T2 compared with T1. The study elucidates polyculture of mudcrabs with finfish can be a taken up as a profitable venture for sustainable diversification of brackishwater farming in Sundarbans.  相似文献   

20.
Nile tilapia (Oreochromis niloticus) is currently one of the most farmed freshwater fish and contributes significantly to total global aquaculture production. The genetically improved strain of O. niloticus (GIFT) was introduced to Papua New Guinea (PNG) in 1999 to improve food and income security. The high cost and low availability of commercial fish feed hinder the growth of GIFT farming in PNG. Stable carbon and nitrogen isotopes were used to determine the role of supplementary and natural food sources in the diet of GIFT in pond‐based aquaculture. Two treatments were used: treatment 1 was daily feeding, and treatment 2 was weekly feeding, each with three replicates. Isotopic analysis of muscle tissue and all potential food sources showed that pellet feed contributed 7% to the growth of GIFT in daily‐fed ponds and 33% in the weekly‐fed ponds. Highly enriched δ15N values for chicken manure, compared to depleted values for GIFT and other natural food sources in both treatments, clearly indicate insignificant contributions of this input to production. After 90 days of cultivation, the average final body weight of GIFT receiving daily feed inputs was 134 g (average 19 cm), while for weekly‐fed it was 92 g (17 cm). The feed conversion ratio (FCR) was poor (6.4:1) in the daily‐fed GIFT ponds compared to a better, and preferable, FCR (1:1) in the weekly‐fed ponds. The findings of this study show that pelleted feed was not the major contributor to the growth of GIFT. Genetically improved farmed tilapia aquaculture should focus on enhancing natural food availability for fish production.  相似文献   

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