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Growth indices (WG and SGR), food (FCR) and protein efficiency (PER and PCE) of fingerling Nile tilapia, Oreochromis niloticus,were evaluated in 3 synchronous examinations with 12 treatments in triplicates. Groups of control, canola meal (at rates of 25, 50, 75 and 100%), cottonseed meal (at rates of 15, 25, 35 and 45%), as the replacements of expensive protein sources (fish meal and soybean meal), and azolla (at rates of 13, 21 and 29% of diet) were studied. Growth indices, total food intake and protein intake of the control were the highest of all. They decreased with increase in plant protein in every group (p<0.05). FCR and protein efficiency indices didn’t show significant differences (p>0.05) between control and canola meal (at rates of 25 and 50%), cottonseed meal (at rates of 15, 25 and 35%) and azolla (at rates of 13 and 21%). Total food intake, protein consumption and growth indices decreased, because all plant protein ingredients were unpalatable. If the problem of palatability is solved, it seems that the expensive protein sources replace with canola meal and cottonseed meal at the rates of 50 and 35% respectively, and azolla can be used at the rate of 21% in diets. 

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Abstract:

An experiment was conducted to evaluate the effects of stocking density on growth and survival of Nile tilapia (Oreochromisniloticus) in brackish water earthen pond. Fish with initial weight of 13 g kept in three stocking density 3, 6 and 9 fish/m₂ in duplicates and were fed on rainbow trout feed for 105 days during the light period. The results showed significant reduction in final weight, weight gain, daily growth rate, specific growth rate and survival by increasing stocking density, while feed conversion ratio enhanced in higher stocking densities (p< 0.05). Among the treatments evaluated, 3 fish/m² showed the best growth rate and survival, and the lowest feed conversion ratio. So, it seems that to achieve the highest profit, the stocking density of 3 fish/m² is suitable for culturing of tilapia in earthen pond. 

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Aims: Malathion is one of the agricultural organophosphate pesticides used in agriculture that may be found in aquaculture centers. The aim of this study was to investigate the effects of different levels of dietary vitamin C on improving the situation of growth, digestive enzymes activity and blood stress factors of Nile Tilapia (Oreochromis Niloticus) under sub-lethal toxicity of malathion.

Materials & Methods: In this experimental study, 180 Nile tilapia with weight average of 12.5±5g were subjected to 25% concentrations of Lc50 96h of malathion for 28 days and during this period, the fishes were fed with different levels of vitamin C (0, 300, 600, and 900mg/kg of feed). Data were analyzed by Duncan's new multiple range test and one-way analysis of variance through SPSS 24 software.

Findings: The weight gain and specific growth rate of fish fed by the highest vitamin level (900mg/kg of feed) were significantly higher than other groups (p<0.05), while the feed conversion ratio in the fish under mentioned treatment significantly decreased compared to other treatments. Trypsin and chymotrypsin digestive enzyme activities were significantly increased in treatments of 600 and 900mg/kg vitamin C in diet, respectively. The activity of other enzymes at different concentrations of vitamin C in the diet did not show a significant difference (p>0.05). Blood glucose level was significantly higher in control treatment in comparison to the other treatments.

Conclusion: Vitamin C as an anti-stress agent reduces the stress in Nile tilapia subjected by Malathion pesticides and improve the metabolic status and growth performance of Nile tilapia.

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The effects of natural zeolite as a bed medium in increasing lettuce and red tilapia growth as well as improvement of water quality parameters in an aquaponic system were investigated. An experiment with a completely randomized design was run with two treatments in triplicates, 1) an aquaponic system without use of zeolite as a control group and 2) use of a small cotton bag, containing 10 g zeolite as a bed medium for planting a lettuce seedling. In each experimental unit, 42 seedlings of lettuce were introduced. The individual weight of fish and lettuce yield in treatment 2 was significantly higher (P< 0.05) than treatment 1 at the end of experiment. The initial mean individual weight of red tila-pia juveniles was 6.23 ± 0.06 g and increased to 32.50 ± 2.00 and 37.50 ± 2.20 in treat-ments 1 and 2, respectively by the end of experiment. The yield of lettuce was higher in treatment 2 (1507 ± 445.00 g/unit) compared to the control (275 ± 83 g/unit). The concen-tration of total ammonia-N in the water was significantly lower (P< 0.05) in treatment 2 compared to treatment 1 at the end of experiment. The concentration of phosphorous and potassium in the fish rearing tanks was significantly lower (P< 0.05) in treatment 2. These results indicated that the use of zeolite, as a bed medium to plant lettuce seedlings in a re-circulating aquaponic system could increase the growth of lettuce seedlings as well as im-proving water quality parameters.

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The purpose of this study was to measure sensory, chemical, microbial, freshness and shelf life of packaged Tilapia fillets by vacuum and modified atmosphere methods compared to fillets packaged by aerobic method at refrigeration. Methods: Treatments consisted of Tilapia fillets packaged by vacuum and modified atmosphere methods. The fillets packaged by aerobic method were as control samples. Findings: TVB-N, PV, TBARS, total bacterial count, Staphylococcus and Pseudomonas bacteria, sensory parameters and freshness showed significant differences in experimental and control treatments (P<0.05). The studied factors did not show significant difference in modified atmosphere treatments compared to vacuum treatments (p> 0.05). Coliform, Escherichia coli and anaerobic bacteria were not observed in experimental and control treatments. Sensory evaluation and frshness were better in modified atmosphere treatment compared to vacuum treatment (p> 0.05). Chemical, microbial, sensory factors and freshness had significantly different in the experimental treatments compared to the control sample (p<0.05). The experimental and control treatments had good quality during 14 and 6 days at refrigeration. Conclusion: Considering the absence of significant differences in microbial and chemical quality of experimental treatments and higher sensory evaluation and freshness of modified atmosphere treatment compared to other treatments, modified atmosphere packaging method is recommended for packing Tilapia fish fillet at refrigerator temperature.

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Aims: The aim of the present study is to evaluate the amount of tilapia fish consumption and the relationship between its consumption amount and some demographic characteristics Such as gender, age, occupation, education, marital status, occupation, number of household members and income.
Methods: The statistical population of this research is the whole country. A questionnaire was designed and sent to people electronically through virtual space. Correlation tests were used to evaluate the number of fish purchases per year as well as the amount of each purchase from the output of SPSS software and to investigate the existence of a significant relationship between consumption and demographic characteristics.
Findings: The results showed that Most of the female respondents are married, aged 20 to 35, employed and have bachelor's and master's degrees. Most of them are employees and earn between 3 and 6 million tomans. It was also found that most households (54%) buy fish up to 20 times a year. The average number of times of buying fish per year by the households of the consumption community was 45 times. Most households in the consumer society buy 2 kg of fish each time they buy. The number of households that consume more than 10 kg of fish per purchase was 3.3%. According to the obtained information, the average amount of fish per purchase was calculated to be 8 kg. The per capita consumption of tilapia in households consuming this fish was 4.2 kg.

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This study was undertaken to evaluate the effect of hydrolysable tannin (HT) and condensed tannin (CT) on growth performance and body composition of Nile tilapia. Hydrolysable tannin and CT were included into diets at four levels (0, 5, 15, and 25 g kg-1 diet). The diet with zero tannin level acted as control and the response of fish fed diets containing tannin was compared to that of the control diet. All the diets were iso-nitrogenous and iso-energetic. Hydrolysable and condensed tannin had a significant (P<0.05) effect on body weight gain (WG), feed intake (FI), feed conversion ratio (FCR), specific growth rate (SGR) and protein efficiency ratio (PER). Weight gain, SGR and PER of fish fed on the diets containing 15 and 25 g HT/ kg diet were significantly (P< 0.05) lower than those fed on the other diets. Feed conversion ratio of fish fed diets containing 15 and 25 g kg-1 HT were significantly (P<0.05) higher than those fed on the other diets. Feed intake of fish fed diets containing 15 and 25 g HT/kg diet were significantly (P< 0.05) lower than those fed on the other diets, except for diet containing 15 g kg-1condensed tannin (CT2). It is concluded that adverse effect of HT is higher on tilapia compared to that of CT and that protein sources of plant origin containing high amounts of tannins, in particular HT, should be used with caution as fish meal substitutes in tilapia diets.