Muhammad Zairin

Water quality fluctuations under floating net cages for fish culture in Lake Cirata and its impact on fish survival

Vertical profiles of water quality were surveyed before and after mass mortality of fish cultured in cages in Lake Cirata, a man made lake in Indonesia. The first survey was performed 4 months before the mass mortality and the second survey was carried out 4 days after the mass mortality. In the first survey, the conditions below 8 m depth were reductive and anoxic, although at 8 and 10 m depth, the water became oxidative in spite of low oxygen concentration in the second survey. These changes were probably caused by strong mixing of surface water with deeper water. Eight months after the mass mortality, when the redox potential at 8m became reductive again, exposure tests of fish were performed in different layers in the water column around the cage. During the exposure tests the redox potential of the water was less than −100 mV and 93% of carp died within 6 h of exposure at 8 m depth. These results indicated that the mass mortality was caused by the strong mixing of surface water with reductive water in deeper layers.

PENGARUH PEMBERIAN HORMON ITe METILTESTOSTERON SECARA ORAL PADA INDI.,K IKAN GAPI (Poecilia retidlau Pcters) STRAIN TUXEDO TERHADAP JENIS KELAMIN KETURUNANNYA

Percobaan dilakukan untuk mengetahui pengaruh pemberian hormon lzo-metiltestosteron secara oral pada induk ikan gapi (Poecilia reticulau Peters) strain tuxedo terhadap ienis kelamin keturunannya.

A rapid chromosome preparation technique without metaphase arrest for ploidy determination in Nile tilapia, Oreochromis niloticus

Abstract Most chromosome preparation techniques use colchicine or colcemid in order to arrest cell division during metaphase, which usually involves the use of high cost materials. This research was aimed to simplify fish chromosome preparation technique without using colchicine or colcemid. Ten fish of different ages, namely one-, two- and three-month-old Nile tilapias, were used in this research. Tissues were collected on the caudal fin of the fish. Chromosome spreads was easily observed, using Giemsa or silver staining, five hours after the whole preparation process. The results showed that the one- and two-month-old fish had better mitotic index (0.008 and 0.01, respectively) compared to those of the three-month-old fish (0.005). This method is rapid, cost-efficient and applicable for ploidy level determination, and also keeps fish alive for subsequent evaluations.