PARTIAL REPLACEMENT OF FISH MEAL BY A COMBINATION OF VARIOUS PROTEIN SOURCES IN PRACTICAL EXTRUDED PELLETS FOR STARRY FLOUNDER Platichthys stellatus  

Dietary fish meal is recognized to be the best ingredient with the high protein and good balanced amino acid profile for fish. Because the supply of fish meal is however static or even decreasing, a number of studies have been conducted to reduce its dietary incorporation level for farmed fish. Even though many ingredients have been tested as fish meal replacer for various species of fish, the research to find out the total substitute seems to be still on a long way to go. Differently from the other flatfish, starry flounder Platichthys stellatus grows well on diet composed of plant protein sources with low fish meal. Fish meal-based diet is, however, being commercially produced for the fish in Korea. Therefore, an attempt to investigate growth, hematological parameters and muscle fatty acid composition of the fish fed diets with different levels of fish meal was made under the field condition. A blend composed of lysine cell mass, corn protein concentrate and poultry by-product meal was employed to replace fish meal.

Dietary incorporation level of the alternative increased from 10 to 20, 30, 40 and 50%, while that of fish meal decreased correspondingly from 52 to 42, 32, 22 and 12%. The experimental diets were formulated to contain 52% protein and 10% lipid. A commercial diet containing the same levels of protein and lipid was used performed as positive control. The 5 experimental diets were extruded using a conventional twin extruder at the size of 3.5 mm.

Juvenile starry flounder with around 80~120 g of average body weight were randomly distributed in each (600~620 kg/tank) of 6 concrete tanks (8x8x0.5 m each) under a flow-through culture system. Water exchange rate was kept at 25 times a day and water temperature at 11.2 to 13.8℃ during 6 week feeding trial. Fish were fed by hand twice a day. Weight gain (WG), feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR) and survival rate (SR) of fish fed the experimental diets were investigated. Hematological parameters and muscle fatty acid composition will be discussed.

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