COMPARATIVE GROWTH-PERFORMANCE AND DIGESTIVE ENZYME-ACTIVITY OF JUVENILE SOUTH-AFRICAN ABALONE, HALIOTIS-MIDAE, FED ON DIATOMS AND A PRACTICAL DIET

The growth performance of juvenile South African abalone, Haliotis mid ae (3.22-11.29 mm shell length), fed diatoms and a pelleted, practical diet was evaluated. The growth of the juveniles did not differ signif icantly in terms of the increase in shell length (diatoms, 50 +/- 7 mu m day(-1); pellets, 59 +/- 9 mu m day(-1)) and weight (diatoms, 1.66 +/- 0.24% daily growth rate; pellets, 1.91 +/- 0.27% daily growth rate ), Abalone fed the pellets consumed 5.55 +/- 0.20% of their body weigh t per day, feed conversion ratio was 0.44 +/- 0.04, protein efficiency ratio 6.64 +/- 0.77, and percentage protein deposited 32.64 +/- 3.72% , Protease activity was significantly higher, and amylase activity sig nificantly lower, in juveniles fed pellets in comparison with diatoms. Similar, but very low, levels of lipase activity were observed in juv eniles fed both the practical diet and diatoms. The results show that the digestive physiology of juvenile H. midae can readily adapt to art ificial diets, and that these can successfully replace natural diets.