نوع مقاله : مقاله پژوهشی
نویسندگان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
A research experiment was conducted to provide a protocol for seminatural propagation and rearing of Roach up to release size. The attempt was made to combat the declining trend in the population size and catch of the fish in the Caspian Sea. The optimum temperature for spawning brood-stocks lasts from middle March to late April when the ambient temperature range is 12-17°C. During the four months research period, brood stocks were caught in the estuary of the Gorganrood in Golestan Province, north east Iran. The stocks were released into 2 hectare earthen ponds enriched with manure and fertilizers. Artificial spawning grounds made of pine branches were placed in the ponds. Ponds were stocked with 700 female breeders with an average weight of 150 grams and around 350 male breeders weighing 100 grams on average. Spawning and fertilization of eggs occurred in the ponds of which an estimated 80-90% eyed that were observed from the fifth day onwards. The starting of hatching was observed in the 6th day and yolk sac absorption was observed in day 4 to 6. The larvae were fed on natural zooplankton and artificial food. Assessment of 146 fries for ingested food indicated that the fries fed on Rotifer (Rotatoria sp. and Daphnia sp.) in the ponds. The length-weight relationship was not significantly different among the ponds and also specific growth rates (SGR) did not show any difference in the fries. The relative gut length in the fries were smaller than 1 (RLG<I) and fries with an average weight of 0.5 to 1 gram were released into their natural habitat.
کلیدواژهها [English]
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