THE NUTRITIONAL-VALUE OF 4 AUSTRALIAN MICROALGAL STRAINS FED TO PACIFIC OYSTER CRASSOSTREA-GIGAS SPAT

Four Australian microalgal isolates (Pavlova pinguis, Rhodomonas salin a, Tetraselmis sp. CS-362 and Nannochloropsis-like sp. CS-246) were co mpared to an overseas isolate (Isochrysis sp, (T.ISO)) to assess their potential as food for bivalve aquaculture, When fed to Pacific oyster spat, the best growth was observed with a mixed diet comprising the f our Australian species plus Isochrysis sp. (T.ISO)(161% increase in or ganic weight over 21 days). The best growth using the monospecific die ts was produced by P. pinguis (111% increase), followed by Isochrysis sp, (T.ISO) and R. salina (85% and 82%); then Tetraselmis sp, CS-362 ( 51%), and Nannochloropsis-like sp. CS-246 (35%). The growth rates (bas ed on an increase in organic weight) of oysters fed the monospecific d iets were correlated to the amounts of protein and carbohydrate they i ngested. The gross biochemical composition of the microalgae grown in semicontinuous culture differed significantly. Protein ranged from 48% of the dry weight (R. salina) to 17% (Nannochloropsis-like sp. CS-246 ); carbohydrate ranged from 41% (P. pinguis) to 22% (R, salina); and l ipid from 16% (Tetraselmis sp. CS-362) to 26% (Nannochloropsis-like sp . CS-246), The instantaneous growth rate (mu) of Isochrysis sp, (T.ISO ) (mu = 0.48 day(-1)) was greater than the Australian strains, the bes t of which was R. salina (mu = 0.37). (C) 1998 Elsevier Science B.V. A ll rights reserved.