No abstract

No abstract

No abstract

A series of experiments were conducted with black tiger shrimp (Penaeus monodon) juveniles to firstly determine the effects of reducing fishmeal inclusion in a diet and then to evaluate the potential for a microbial bioactive to support complete replacement of both fishmeal and fish oil in feeds when fed under clear-water and green-water conditions. The isoproteic and isoenergetic replacement of fishmeal resulted in a consistent decline in growth performance indicating that at every decrease in fishmeal below an inclusion level of 45% there was a decline in performance. In a subsequent trial undertaken in a clear-water tank system diets devoid of both fishmeal and fish oil fed to shrimp were demonstrated to produce poorer performance than a fishmeal and fish oil reference diet. However the addition of a microbial bioactive to the diet resulted in not only a compensation for the replacement of these ingredients but additional growth. Replication of the clear-water trial in a green-water tank system produced similar results, but also showed that the green-water system largely compensated for the performance lost through replacement of fishmeal and fish oil. However it was also shown that the use of the microbial bioactive in the diets still resulted in improved growth performance of shrimp. This study has effectively demonstrated a viable strategy for not only a complete replacement of all fishery products in shrimp diets, but an improved performance strategy.

The contribution of epiphytes associated with physical substrates to the nutritional requirements of postlarval shrimp, Penaeus esculentus Haswell was determined in highdensity rearing systems (3000, 6000 and 11,000 m -3 ). Stable isotope signatures of epiphytes on polyethylene mesh substrate, AquaMats TM and tank walls were compared with shrimp signatures. Two methods were used: the determination of carbon and nitrogen natural abundance ratios; and 15 N-nitrogen enrichment ratios after the addition of 15 N-ammonium to tanks. Using the natural abundance technique and a simple mixing model, epiphytes were found to contribute substantially to the carbon requirements of postlarval shrimp (39 to 53%). This was despite the addition of formulated feed at satiation levels. There was no indication of a reduced contribution of carbon from epiphytes to shrimp nutrition at higher shrimp densities. The lack of a difference in the 15 N/ 14 N ratios of the two food sources meant that mixing models could not be used to calculate the contribution of nitrogen from epiphytes vs. artificial feed to shrimp nutrition. Using the 15 N-nitrogen enrichment method, the amount of nitrogen contributed by epiphytes to shrimp nutrition over 24 h could be determined. This method showed that nitrogen from epiphytes was assimilated by shrimp. 15 N-enrichment methods provided a more accurate alternative to natural abundance techniques particularly when the stable isotope signals of the food sources are similar. This experiment has shown the benefits in providing substrates for P. esculentus in high density rearing systems to provide an additional food source for shrimp. shrimp ponds. Aquaculture Research, in press.

No abstract

The reproductive performance of domesticated Penaeus monodon was assessed when fed on two experimental semi‐moist maturation diets varying in their arachidonic acid content for 21 days before ablation and throughout a 17‐day reproductive assessment. The biochemical composition of the two semi‐moist two diets was similar with the exception of arachidonic acid (ARA) content; the basal diet (BAS) consisting of 0.9 g kg−1 DM ARA (1.1% of total fatty acids) and the supplemented diet (ARA‐SUP) consisting of 5.0 g kg−1 DM ARA (5.8% of total fatty acids). ARA/EPA and ARA/DPA ratios were 0.1 in the BAS diet and 0.5 in the ARA‐SUP diet. Fatty acid composition of the spawned eggs was comparable between diets with the exception of ARA concentration, which was higher in the ARA‐SUP (8.95 ± 0.44 g kg−1 DM) than the BAS (3.23 ± 0.17 g kg−1 DM) (P < 0.0001). The cumulative percentage of females spawning (mean ± SE after 17 days) (31.9 ± 7.0%; 24.1 ± 1.3%), number of spawnings per female (0.48 ± 0.1; 0.29 ± 0.02), and eggs per female (62 520 ± 16 935; 44 521 ± 9914) was significantly (P < 0.0001) higher for the ARA‐SUP than the BAS. Results of this study suggest that arachidonic acid plays a key role in promoting egg development and spawning in P. monodon.

No abstract