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Showing 4 results for Survival
Effects of Spawning Frequency and Density of Incubating Eggs on Egg and Larvae Survival Rates in Rainbow Trout
N. Mahboobi Soofiani, O. Farhadian,
Volume 6, Issue 4 (1-2003)
Abstract
To determine the effects of spawning frequency and density of incubating eggs on the survival rates of eggs and larvae in rainbow trout, five different groups of broodstocks with varying spawning frequencies were stripped. After fertilization, the percentage of survival at different stages of development, from eying, hatching to free swimming fry stages and also growth rates of larvae were determined. Moreover, the effects of incubating egg density (4000, 7000, 10000 per tray) on the different developmental stages of egg through free swimming larvae for each group of broodstock was studied. The study was carried out in a completely randomized design as a 5*5*3 factorial arrangement with three replicates. The results indicated that survival and growth rates are significantly correlated with spawning frequency (P<0.05) so that, survival and growth rates from fertilization to free swimming fry in broodstocks at their third and fourth spawning period were significantly different from the results obtained for broods in the first, second and fifth or higher spawning periods (P<0.05). Although the holding densities had no significant effects on the growth rate of larvae from different broodstocks, the survival rates from fertilization to free swimming stage was affected by incubating density so that the significantly lower value was recorded for density of 4000 per tray (P<0.05). In general, the results indicate that eggs obtained from broodstocks at their third and fourth spawning years have a better performance than those obtained from younger and older spawners. Also, the low holding density of eggs could decrease the performance of the fertilized eggs during incubating period.
Comparison of Dry and Semi-dry Fertilization in Rainbow Trout (Oncorhynchus mykiss) with Emphasis on Larval Survival Rate
O. Farhadian, M. R. Ahmadi,
Volume 7, Issue 3 (10-2003)
Abstract
Oval fertilization and survival rates at incubation stage form the most important issues of concern in rainbow trout hatcheries in Iran. Hatchery managers tend to use the best method in fertilizing the ova in order to obtain the highest survival rates. A survey of common fertilization methods may help to determine the best one. In this study, the ova from two groups of 3-5 year-old and younger than 3 years broodstocks were fertilized employing dry and semi-dry methods in normal water and dry and semi-dry methods in fertilization solution. The experiment was carried out in a completely randomized design as a 422 factorial arrangement and with two replicates. The analysis of final results indicates that the highest survival rates of eggs and larvae were obtained in semi-dry fertilization. These rates significantly increased when fertilization solution was used (P<0.05). Moreover, the survival rates of eggs and larvae of 3-5 year-old broodstocks were higher than those of younger than 3 years. On the other hand, type and methods of fertilization showed no significant differences with degree-day (sum of heat) at developmental stage but the age of broodstocks made significant differences with degree-day from fertilization to the first hatching stage (P<0.05).
Evaluation of Different Irrigation Methods of Hedysarum criniferum Boiss. under Field Conditions
O. Asadi Asadabad, S. H. Matinkhah, Z. Jafari, H. Karim Mojeni,
Volume 25, Issue 1 (5-2021)
Abstract
In order to investigate the effect of the type drip of irrigation methods, subsurface irrigation and furrow irrigation on the domestication of Hedysarum criniferum Boiss., an experiment with a  randomized complete block design with three replications was implemented  at Isfahan University of Technology for two years (2016 to 2018) . For this purpose, clay pipes were made and the plant was cultivated on the sides of clay pipes and types. Also, furrow irrigation treatment was applied as the control. During the experiment, all treatments received the same water and finally, some growth parameters were measured. The results of the study showed improvement in height (0.43 and 0.34), canopy cover (0.66 and 0.52), stem number (0.44 and 0.85), chlorophyll index (0.45 and 0.45), seed emergence (0.75 and 0.30), plant survival (0.78 and 0.55), yield (0.23 and 0.35), and water use efficiency (0.25 and 0.25) under type drip irrigation treatment, as compared to subsurface and furrow irrigation, respectively (P<0.05). In general, the type drip treatment is recommended in the early years of planting; however, since the maximum production potential of this plant is in the third year onwards, it is necessary to examine the results in the following years to recommend the proper irrigation method, especially the use of subsurface irrigation. 

Investigation of Potential and Performance of Five Chemical and Mineral Mulch in Stabilizing Sand Dunes
S.m. Abtahi, M. Khosroshahi,
Volume 28, Issue 4 (2-2025)
Abstract
Today, wind erosion and dust are an environmental crisis, not just in desert areas but also in the entire country, and putting many costs. The combat against wind erosion in many desert areas by using oil mulches and the cultivation of compatible plants started in the 40s. However, the use of petroleum in addition to mulching the environmental problems, due to the high costs of purchase, displacement, and dispersion, is not economical. Therefore, the performance of non-oil and chemical mulch on dunes was investigated in Kashan. The research on fertilizer application of mulch under a completely randomized design includes: control (no mulch), a polymer mulch, potas, Fars, Paya, and Akrilik at 3 reps (3 sand hills) and the amount of erosion (with the help of the embedded indices in the hills), the survival of plants cultivated in the form of cuttings and seedlings, the percentage of humidity and temperature of each iteration were measured and variance analyses were performed. Field surveys and the results of the statistical analysis showed that the strength resistance of Fars, Paya, and Akrilik is almost the same. Observation of wood indices showed that Fars, Paya, and Akrilik mulches have almost the same strength in terms of wind resistance (almost no wind resistance). Fars mulch after 8 months of spraying showed small fractures due to the loss of flexibility. The study of soil temperature statistics showed that the treatments under mulch had no significant temperature difference compared to the control treatment. A comparison of soil moisture data indicated a high moisture percentage in the potash mulch treatment. The survival rate of cultivated plants was higher in Paya and Akrilik treatments. According to the results, Akrilik, Paya, and Fars mulch are recommended for sand fixation. One of the limitations of research in desert areas is the uncontrollability of environmental and human conditions. So, it is recommended to close the entire mulching area and use a mobile wind tunnel device at the project site to determine the wind slavery at different speeds.

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