One 6-week feeding trial was conducted to determine the dietary protein requirement of juvenile giant croaker, Nibea japonica. Semipuri®ed diets were formulated with white ®sh meal to contain graded levels of protein ranging from 30% to 55% of dry diet. Each diet was fed to triplicate groups of juvenile giant croaker initially weighing 1.86 T 0.07 g ®sh ±1 (mean T SD) in a¯ow-through seawater system. Giant croaker were raised in aquaria with a water temperature of 16.4±20.0°C for 6 weeks. Weight gain and feed ef®ciency were best in ®sh fed diets containing 45% protein or more in the experiment. The protein ef®ciency ratio value was maximized in ®sh fed diets containing 45% crude protein, and declined in ®sh fed diets containing 50% crude protein and higher. Survival was independent of all diets excluding 30% crude protein. At elevated dietary protein level, wholebody moisture decreased and lipid increased (P < 0.05); however, all diets containing different protein levels produced similar condition factors, intraperitoneal fat, whole-body protein and ash. Hepatosomatic index and intestinosomatic index were maximized in ®sh fed diets containing 50% and 40% crude protein, respectively. Diets containing higher protein levels (45%±55%) produced signi®cantly higher muscle ratio values compared with the diets containing lower protein levels (30%± 40%), whereas ®sh fed all diets containing different protein levels had similar muscle ash, lipid, moisture and protein values. The optimal dietary protein requirement for juvenile giant croaker was deter-mined to be 45% of dry diet in natural seawater based on high weight gain, feed ef®ciency, protein ef®ciency ratio values and muscle ratio.

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Genetic parameters for growth-related traits were estimated in 9-month old of two Korean abalone subspecies, Haliotis discus hannai and H. discus discus, using multiple traits of animal model. The data were collected from the records of 3,504 individuals produced from 16 sires and 17 dams in H. discus hannai and 821 individuals produced from 3 sires and 4 dams in H. discus discus, which was evaluated at the Bukjeju branch, NFRDI, from May 20, 2004 to February 14, 2005. The heritability estimates obtained from restricted maximum likelihood (REML) method range from 0.29 to 0.31 for three growth traits (shell length, shell width and body weight) in H. discus hannai and from 0.22 to 0.28 in H. discus discus, respectively. The heritabilities for shell shape and condition factor were lower than others of growth traits such as ranging from 0.03 to 0.24 in H. discus hannai and from 0.06 to 0.11 in H. discus discus, respectively. Genetic and phenotypic correlations were >0.91 between shell parameters and weight in two abalone subspecies, respectively, indicating that breeding for weight gains could be successfully achieved by selecting for shell length.

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