Postprandial Ammonia Excretion and Oxygen Consumption Rates in Olive Flounder Paralichthys olivaceus Fed Two Different Feed Types According to Water Temperature Change

Abstract

Postprandial ammonia excretion and oxygen consumption in olive flounder Paralichthys olivaceus fed two different feed types, moist pellet (MP) and expanded pellet (EP) diets, to satiation were determined at <TEX>$12^{\circ}C$</TEX>, <TEX>$15^{\circ}C$</TEX>, <TEX>$20^{\circ}C$</TEX>, and <TEX>$25^{\circ}C$</TEX> for 48 h. The ammonia excretion and oxygen consumption rates increased with increasing water temperature. However, the postprandial times for the maximum rates of ammonia excretion and oxygen consumption were shortened from 12 h to 6 h after feeding with increasing water temperature. The ammonia excretion and oxygen consumption rates of the fish fed EP were significantly higher (P < 0.05) than those fed MP at 12 h post-feeding both for <TEX>$12^{\circ}C$</TEX> and <TEX>$15^{\circ}C$</TEX>. The highest (P < 0.05) weight-specific ammonia excretion rates at <TEX>$12^{\circ}C$</TEX> were observed in the fish fed EP and MP at <TEX>$12.1mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX> and <TEX>$8.7mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX>, respectively, for 12 h and 9 h after feeding. The highest (P < 0.05) weight-specific oxygen consumption rates at <TEX>$12^{\circ}C$</TEX> were observed in fish fed EP and MP at <TEX>$116.4mg\;kg^{-1}h^{-1}$</TEX> and <TEX>$101.0mg\;kg^{-1}h^{-1}$</TEX>, respectively, for 12 h after feeding. The highest ammonia excretion rates at <TEX>$25^{\circ}C$</TEX> in the fish fed EP and MP increased to <TEX>$16.9mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX> and <TEX>$18.3mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX>, respectively, for 6 h after feeding. The highest (P < 0.05) weight-specific oxygen consumption rates at <TEX>$25^{\circ}C$</TEX> were observed in fish fed EP and MP at <TEX>$184.3mg\;O_2kg^{-1}h^{-1}$</TEX> and <TEX>$197.3mg\;O_2kg^{-1}h^{-1}$</TEX>, respectively. These data are valuable for the design of biofilters and development of effluent treatment technologies for the land-based flounder farms.