Biswajit Kumar Biswas

Growth and Environmental Tolerances (Water Temperature and Low Salinity) of Hybrid Female Red Sea Bream Pagrus major × Male Black Sea Bream Acanthopagrus schregeli

The growth and tolerance for water temperature and salinity were compared among red sea bream Pagrus major (RSB) black sea bream Acanthopagrus schregeli (BSB) and their hybrid (), female RSB male BSB. The growth of the fish did not differ until 27 days after hatching (dAH), after which the most rapid growth was observed until approximately 300 dAH, followed by RSB and BSB. However, the RSB had out grown the fish by approximately 303 dAH. By 480 dAH, the RSB were largest, followed by the and BSB groups. The tolerances for high and low water temperature were significantly different for each species and growth stage. The largest tolerance spectrum was observed in the BSB group, and the tolerance spectrums gradually decreased with increasing final body weight. During the salinity tolerance trials, all of the species started to die following transfer into freshwater (0 psu). BSB showed the highest survival rate when kept in fresh water for an average of 29.9 hours, while the fish were more tolerant than the RSB fish. The fish were increasingly tolerant to fresh water and changes in water temperature as they grew, while the size of the temperature spectrum remained unchanged but shifted to a lower temperature range with growth. Our results demonstrate that performed well in terms of growth compared to parental fish, with higher temperature and salinity tolerances than RSB, and is thus suggested to be a suitable aquaculture species for Korea and northeast China.

Suitable Dietary Protein/Lipid Ratio for Hybrid, Female Red Sea Bream Pagrus major and Male Black Sea Bream Acanthopagrus schlegeli in the Juvenile Stage, Compared with Red Sea Bream

Abstract To determine a suitable dietary protein/lipid (CP/CL) ratio in the early juvenile stages of hybrid porgy (F 1 ), female red sea bream (RSB) × male black sea bream, five diets with various CP/CL ratios—60/7, 55/12, 51/17, 46/23, and 41/28—were prepared and provided to juveniles in triplicate. At the smaller juvenile stage, F 1 , weighing 0.32 g, a significantly higher specific growth rate (SGR) and feed efficiency (FE) were seen with 60/7 and 55/12 diets. However, in RSB weighing 0.26 g, SGR and FE were higher with the 60/7 diet than the other diets at 21°C. At the larger juvenile stage, F 1 , weighing 3.7 g, there was no significant difference in SGR or FE among the diets, but RSB weighing 4.0 g fed 60/7, 55/12, and 51/17 diets had higher SGR and FE than 46/23 and 41/28 diets at 24°C. Moreover, survival and apparent nutrient retention of F 1 at both stages were significantly higher than those in RSB. These results indicate that both F 1 and RSB weighing ca. 0.3 g require a higher dietary CP/CL than those weighing ca. 4 g. Additionally, F