GROWTH, METABOLISM AND GROWTH EFFICIENCY OF A EUPHAUSIID CRUSTACEAN EUPHAUSIA-PACIFICA IN THE SOUTHERN JAPAN SEA, AS INFLUENCED BY TEMPERATURE

Growth (assessed from intermolt period and molt increment) and metabolism (oxygen consumption) of the post-larva of Euphausia pacifica from the southern Japan Sea were determined at seven graded temperatures ranging from 1 to 25 degrees C. The intermolt period shortened progressively as temperature increased from 1 to 20 degrees C, but an effect of temperature on molt-to-molt growth increment was not seen. Oxygen consumption rates were accelerated by the increase in temperature up to 20 degrees C. Beyond 20 degrees C, E.pacifica exhibited reduced oxygen consumption and died within 1 day without molting. After removing the effect of body size, the relationships between growth rate and temperature, and between oxygen consumption rate and temperature, were established. The carbon budget was calculated as a function of temperature. Because of differential effects of temperature on growth and metabolism, the net growth efficiency [K-2: growth x 100/(growth + metabolism)] changed with temperature. The optimum temperature at which Epacifica attained the maximum K-2 was 11.4 degrees C, which was derived from calculation of cumulative carbon invested in growth and metabolism in this animal. Tn an alternative method, the optimum temperature was obtained mathematically by solving a set of differential equations. The biological and ecological significance of the optimum temperature which leads to the maximum K-2 is discussed.