BIOCHEMICAL-COMPOSITION OF SOME PREY SPECIES OF PENAEUS-ESCULENTUS HASWELL (PENAEIDAE, DECAPODA)

A representative collection was made of the very small prey animals that comprise the diet of juvenile Penaeus esculentus in seagrass beds in Moreton Bay, Australia (three gastropod species; two bivalves; four crustaceans; one polychaete). Proximate analyses were made of each group, and whole animals were analysed for total amino acids, lipid classes and fatty acids. The mean protein content ranged from 67 to 83% of ash-free dry weight, the lipid from 10 to 21% and the carbohydrate from 6 to 22%. The amino acid composition was fairly uniform in all species and, except for isoleucine which was lower, similar to that of P. esculentus muscle. Sterols and sterol esters were mostly above 3% of ash-free dry weight; phospholipids ranged from 22 to 80% of total lipid, with phosphatidylcholine a major component in most cases. Saturated fatty acids were < 45% of total fatty acids, except in one bivalve; polyunsaturated fatty acids (PUFA) ranged from 23 to 56% of the total, but levels of C18 PUFA were mostly < 3% of the total; C20:4-omega-6 and higher PUFA were abundant. Overall, the natural diet of P. esculentus is high in protein, with relatively low mean carbohydrate (10.6%) and lipid (12.3%), and with a high proportion of PUFA in the lipid fraction. The relevance of this to empirically derived aquaculture diets is discussed.