The effect of dietary ( n−3) polyunsaturated fatty acids on growth, survival and swim bladder development in Sparus aurata larvae

Abstract

The requirement for dietary ( n−3) PUFA for growth, survival and swim bladder development in gilthead seabream, Sparus aurata, larvae was tested using rotifers with various levels of ( n−3) PUFA. Four rotifer treatments differing in their ( n−3) PUFA content (0.8, 3.2, 5.1 and 8.4 mg/g dry body weight, DBW) were prepared by feeding them combinations of various oil emulsions and dried squid (rich in both EPA (20:5 n−3) and DHA (22:6 n−3)). A fifth treatment consisted of rotifers enriched on the algae Nannochloropsis sp. Regression analyses, from the emulsion treatments, were performed on various relationships between rotifer ( n−3) PUFA levels and larval phospholipid and growth. The equations describing these correlations were then used to examine whether the same parameters in larvae fed Nannochloropsis-enriched rotifers were a result of the dietary ( n−3) PUFA levels they consumed or some other nutritional factor. The results indicate that dietary ( n−3) PUFA significantly ( P<0.05) influence fish moisture and lipid levels and are necessary for good growth in larval gilthead seabream. Fish fed the highest levels of ( n−3) PUFA (8.4 mg/g DBW) showed a four-fold increase in growth (1263% vs. 312%) over larvae offered rotifers with the lowest levels of ( n−3) PUFA (0.8 mg/g DBW). In contrast, there was no compelling evidence that EPA and/or DHA significantly ( P<0.05) affected larval survival or swim bladder inflation and suggests that these dietary factors, at least in the development of the swim bladder, play a more subordinate role. Larval growth on the Nannochloropsis treatment was strongly associated with EPA and implies that, despite other sources of nutrition in the algal media, this fatty acid determines the dietary value of these rotifers for growth in Sparus aurata larvae.