Publication Date:
2021-05-19
Description:
This project was conducted in five independent experiments in appropriate tanks with suitable aeration and water fellow. Temperature: an experiment designed to evaluate the effect of temperature on growth and survival of tilapia fry by using four thermal regimes consist of 22, 25, 28 and 31 °c in three replicates. Fries with initial wight of .014 g were stocked in plastic container with 10 liter capacity at the rare of 5/liter. Fish were fed on rainbow trout commercial food at a rate of 30 % of biomass 5 times per day. The results showed that some growth indices such as final body weight, daily growth rate, specific growth rate and weight gain increased by increasing water temperature significantly. Although fry survival increased by increasing temperature but these differnces were not significant. the results suggest that in larviculture of Nile tilapia water temperatue should not be less than 28°c. Density: compressibility of Nile tilapia fry was studied by using plastic container with 13 liter capacity. Fry with initial weigh of .034 g were stocked in four treatments 10, 15, 20 and 30 fry/l with four replicates. They fed on rainbow trout food according to their biomass five times per day during the light period. The results showed that some growth indices such as average of final body weight, daily growth rate, specific growth rate and survival decreased by increasing stocking density significantly, while feed conversion rate increased by increasing stocking density. Considering the experiment, it could be suggested that lower stocking density (10/l) resulted the best growth efficiency and survival of Nile tilapia fry. On the other hand, compering the results of growth and survival rate(84%) in two stocking densites(15 and 20/l) showed that it is passible to culture Nile tilapia fry at the stocking density of 20fry/l in suitable condition. Salinity: A study conducted to evaluate the effect of salinity on growth and survival rate of Nile tilapia fry by using six salinity levels (0, 4, 8, 12, 16 and 20 ppt) with three replicates. Fry fed on rainbow trout food five times per day during the light period. Results showed that some growth indices such as average of final body weight, daily growth rate, specific growth rate and survival rate increased by increasing salinity levels up to 8 ppt significantly, and then decreased by increasing salinity levels up to 20 ppt. according to the experiment, it seems that larviculture of Nile tilapia in brackish water is available and the best results achives at 8 ppt. considering the results of growth and survival rate at 16 ppt showed that Salinity up to 16 ppt was tolerable, although reduced the growth and survival of Nile tilapia fry. Photoperiod: the objective of this study was to examine the effects of photoperiod on growth and survival rate of Nile tilapia fry by planning four treatments (6L:18D, 12L:12D, 18L:6D and 24L:0D) and four replicates. Light provided by tow fluorescent lamps those set at a distance of 60 cm above the tanks and worked by an automatic timer. Fry fed on rainbow trout food five times per day. Results showed that average of final body weight, daily growth rate and specific growth rate were loest in 6L:18D and these indices increased by increasing light duration. these differences were not significant among 6L:18D and 12L:12D. but the differences between 6L:18D with 18L:6D and 24L:0D were significant. Evaluation of survival rate showed that photoperiod did not significant effect on survival in all treatments. These finding suggests that a 12L:12D cycle be adequate in case of larval rearing. Cannibalism: An experiment designed to determine the occurrence of cannibalism among 5 different size groups of (5, 10, 20 and 30 g with fry 0.45 g) Nile tilapia population (fry / fingerling) under two stocking densities (1 / 2 and 1 / 4 fingerling / fry) with three replicates in the poly etilen tanks in brackish water condition. Fry were counted at 6, 24, 48, 72, 96, 120 and 144 hours after stocking in two methods (feeding and no feeding). In the feeding trial fingerling were fed on rainbow trout food two times per day. The results showed that cannibalism became more intense as the size difference increased. After passing time cannibalism rate increased. Also results showed increasing fry density causes increasing cannibalism in both treatments (feeding and without feeding). Feeding fingerlings (predator) was effective in reducing cannibalism.
Description:
Iranian Fisheries Science Research Institute
Description:
Published
Keywords:
Oreochromis niloticus
;
Fry
;
Temperature
;
Stocking density
;
Salinity
;
Photo period
;
Cannibalism
;
Brackish Water
;
Growth
;
Survival
;
Tilapia
;
Larvae
Repository Name:
AquaDocs
Type:
Report
,
Refereed
Format:
48pp.
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