Egg production of rainbow trout broodstocks stocked in marine cages and freswater ponds

SUMMARY Egg Production of Rainbow Trout (Oncorhynchus mykiss) Broodstocks Stocked in Marine Cages and Freshwater Ponds. In this study, spawning time, fecundity, egg size and survival rates of eggs of rainbow trout (O. mykiss) broodstocks stocked in the sea cages and in the freshwater tanks were investigated. The study was conducted between October 1995 and May 1996. Sea group were stocked in the cages, while freshwater group were stocked in the fiber tanks. Spawning in sea group took place on 11 January and in the freshwater group on 19 January and 8 February 1996. Broodstock weights were 2531.5±85.51 g (n=16) in the sea group, 1377±21.99 g (n=12) in the freshwater group. The mean total fecundity was determined as 6183±376 and, 312Ü276 egg/individual in the sea and in the freshwater group, respectively, while the relative fecundities were 2435±1 18 and 2570±247 egg/kg. Difference in broodstock weights between two group were important (PO.05), and a positive relationship was determined between broodstock weights and mean total fecundity in the each groups (r= 0.63). Mean egg diameters and weights were estimated as 5.25 1±0. 043 mm and 0.095±0.003 g in the sea group and 4.682±0.099 mm and 0.064±0.004 g in the freshwater group. The eggs of the sea group were eyed in the 28th day and hatched in the 36th day. Incubation in this group was 344 day-degree, in 9.6°C water temperature, while the first and the second party of freshwater eggs eyed in 30th and 32nd days and hatched in 367 and 415 day-degree, in 9.3 °C water temperature. Fertilization, eyeing and hatching rates of eggs respectively were determined as 98.5%, 86.7% and 70.4% in the sea group and 95.8%, 83.8% and 76.9% in the freshwater group. Larval survival rates until free swimming were 95. 1% in the sea group, 96.6% in the freshwater group. Key Words : Rainbow Trout, Oncorhynchus mykiss, Fecundity, Egg Quality, Sea water, Freshwater. VI