مقایسه لقاح خشک و نیمه‌خشک تخم ماهی قزل‌آلای رنگین‌کمان (Oncorhynchus mykiss)با تأکید بر میزان ماندگاری لارو

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).