REPLACEMENT OF SQUID AND KRILL MEAL BY SNAIL MEAL Buccinum striatissimum IN PRACTICAL DIETS FOR JUVENILE KURUMA SHRIMPS Marsupenaeus japonicus

Kuruma shrimps (Marsupenaeus japonicus) are considered quite valuable in Japan and they are some of the largest shrimp species in the penaiedae family with females reaching nearly 30 cm in body length. These carnivorous species require a higher amount of protein than other shrimp species at about 55%. This dietary requirement has made it difficult to create optimum diets for them. Fortunately, in Japan, squid and krill meals have been found to be most ideal protein sources for these shrimps. In an effort to promote the use of locally available ingredients to create potentially cheaper feeds, marine snails, Buccinum striatissimum, have been used in the present study to see their effectiveness in replacing squid and krill meal in the diets of kuruma shrimps.

A 60-day feeding trial was conducted in order to investigate the effects of substituting the marine snails for squid and krill meal into the diets of juvenile kuruma shrimps. Five experimental diets were formulated to contain varying levels of snail meal at 0%, 25%, 50%, 75%, and 100% (D1, D2, D3, D4 and D5, respectively) and fed to juvenile kuruma shrimp (initial mean body weight 0.27 ± 0.02g). A natural light and dark regime was observed throughout the experiment and temperature, pH and salinity were recorded with mean values of 23±0.7°C, 7.7±0.5 and 34± 0.06g/L, respectively.

The results showed that growth, total body length, apparent feed intake and specific growth ratio were significantly improved (P<0.05) with 75% and 100% substitution of snail meal. There was no significance (P>0.05) detected in survival rate among diet groups. Lipid content in shrimps fed D1 and D3 were significantly higher while cholesterol content in shrimps fed D4 and D5 were significantly lower and polyunsaturated fatty acid contents were significantly higher in those groups. During the low-salinity stress test, diet groups fed 50-100% snail meal showed a significantly higher resistance (P<0.05) to stress compared with the control group and shrimps fed 25% snail meal. These results suggest that supplementing snail meal for complete replacement of squid and krill meal at 100% can be done in order to improve juvenile kuruma shrimps' growth, stress resistance and to reduce their cholesterol levels.