Document Type : Research Paper
Authors
1
M.Sc. Student, Department of Fisheries Sciences, Natural Resources Faculty, University of Tehran, Karaj, Iran
2
Associate Professor, Department of Fisheries Sciences, Natural Resources Faculty, University of Tehran, Karaj, Iran
3
Professor, Department of Fisheries Sciences, Natural Resources Faculty, University of Tehran, Karaj, Iran
4
Kermanshah Agriculture Organization Aquaculture Researcher, University of Applied Science and Technology, Sarpolzahab, Iran
5
Assistant Professor, Department of Fisheries, Faculty of Marine Sciences, Chabahar Maritime University, Chabahar Iran
Abstract
Water’s oxidation-reduction potential (ORP) is one the of water’s physicochemical indexe that is affected by the combination of oxidizing and reducing agents. In addition to affecting many water quality parameters, this index alone reflects the general water quality conditions. The aim of this study was to investigate the effect of different levels of water oxidation-reduction potential (ORP) on some reproductive indices of the giant freshwater prawn female brood-stock. For this research, 4 treatments in triplicates with levels of 200-150 (control treatment), 250-200 (2nd treatment), 300-250 (3th treatment), 350-300 (4th treatment) mv were provided and checked and regulated by digital ORP meter daily. Reproductive indices including egg dry weight, fertilized egg percentage, egg hatching percentage, fertilizing rate, egg clutch somatic index (ESI), larval dry weight, larval stage index (LSI), and larval condition index (LCI) were evaluated. In each experimental unit with a volume of 80 liters, three female brood-stocks and one male were stocked for 8 weeks. Based on the results, the percentage of fertilization in the second treatment showed a significant increase (P <0.05) while the third and fourth treatments recorded a significant decrease (P <0.05). The LSI index of the second treatment significantly increased (P <0.05) with the first treatment (control), but the third treatment was not significantly different and the fourth treatment had a significant decrease (P <0.05). ESI, LCI and egg dry weight indices in the second treatment (200-250 mV) were not significantly different (P <0.05) but in the third and fourth treatments were significantly reduced (P <0.05). Egg dry weight in the third and fourth treatments had a significant decrease compared to the control treatment, but the second treatment did not record a significant difference. In general, according to the results of this study, keeping the levels of water,s ORP between 200-250 mv in the freshwater giant prawn -brood-stock tank provides the best reproductive performance.
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