- The effects of temperature and ration on growth, food consumption, and food conversion efficiency of chum salmon, Oncorhynchus keta, in sea water were studied in two experiments conducted during the spring, summer, and fall, 1973, at the Oregon State University Marine Science Center, Newport, Oregon. The test temperatures
employed in the study were nominally 11.0, 13.5, 16.5, and 20.0 C. The fish were fed the Oregon Moist pellet. Rations fed during the first experiment (May 29-July 7) were 3, 6, 9, and 15 percent of the dry body weight of the fish per day. Rations fed during the second experiment (Sept. 28-Nov. 7) were 3, 8, 13, and 18%/day. The growth rates of the fish increased with an increase in ration level at all test temperatures. Growth during the first experiment was markedly lower than during the second experiment at each ration level.
Growth rates during both experiments were generally higher at 13.5 C than at lower or higher temperatures. During the first experiment, growth rates at the highest test temperatures (16.5 and 20.0 C) were positive only at the highest ration level (15%/day). Values of growth rate during the second experiment were positive at all but the lowest level (3%/day) at all test temperatures. Food conversion efficiency was found to be directly related to ration level and inversely related to temperature. At low consumption rates, increases in temperature markedly reduced efficiency. As ration levels increased, the effects of temperature were ameliorated. The highest conversion efficiencies at the lowest temperatures reflect the decrease in maintenance rations with a decrease in temperature. As with growth, the highest conversion efficiencies were
generally found at 13.5 C. Maximum food consumption rates and maintenance rations were generally lower in experiment U than in experiment I. These differences in consumption and maintenance may be attributable to the larger sizes of fish used in the second experiment than in the first experiment. The number of deaths resulting from Vibrio disease during experiment I was found to be directly related to temperature and
inversely related to ration level. Mortality resulting from Vibrio disease during experiment II was generally highest at the highest temperatures. Unlike experiment I, there was no clear relationship between mortality and ration level during the second experiment. The results of the study suggest that elevation of sea water temperatures beyond approximately 13.5 C does not benefit the growth of chum salmon, but the extent to which disease may have influenced the growth and food relationships of the fish at elevated temperatures could not be adequately evaluated. Further studies to determine the temperatures most favorable for the culture of chum salmon should be undertaken upon development of methods for the control of Vibrio