Nutritive value of 'Tahiti Isochrysis' Isochrysis sp. for larval greasy back shrimp, Metapenaeus ensis
1997
Okauchi, M. (National Research Inst. of Aquaculture, Tamaki, Mie (Japan)) | Kawamura, K. | Mizukami, Y.
The diatom, Chaetoceros gracilis, is extensively used as a nutritive food organism in the rearing of shrimp larvae in Japan. the large-scale outdoor culture of this species is, however, difficult during the summer season. To access the suitability of "Tahiti Isochrysis" Isochrysis sp. (T-Iso) as a substitute for C. gracilis, we investigated the comparative nutritive value of these algae for larvae of greasy back shrimp, Metapenaeus ensis, by feeding experiments and fatty acids analyses. Further, T-Iso was cultured in large-scale outdoor tanks to determine its suitability for culture during the spawning season of M. ensis in summer. Larvae fed on T-Iso only were considerably delayed in development as compared to those fed on C. gracilis. On the eicosapentaenoic acid, which is known as an essential fatty acid of Kuruma prawn Penaeus japonicus larvae, the content of T-Iso was less than that of C. gracilis. Thus, the nutritive value of T-Iso seemed to be lower than that of C. gracilis. However, the survival rate and the development of larvae fed on T-Iso and C. gracilis mixture were better than those of larvae fed on C. gracilis or T-Iso in single use. Further, T-Iso showed a steady and constant increase in density in both 100-l and 500-l outdoor tanks under high temperature conditions like Tetraselmis tetrathele and Nannochloropsis oculata. Therefore, T-Iso is useful as a supplemental food alga to C. gracilis, particularly during summer periods of high temperature and achieve a high survival rate and good growth of the shrimp larvae
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