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The fate of 15N-nitrogen-enriched formulated feed fed to shrimp was traced through the food web in shallow, outdoor tank systems (1000 l) stocked with shrimp. Triplicate tanks containing shrimp water with and without sediment were used to identify the role of the natural biota in the water column and sediment in processing dietary nitrogen (N). A preliminary experiment demonstrated that 15N-nitrogen-enriched feed products could be detected in the food web. Based on this, a 15-day experiment was conducted. The ammonium (NH4+) pool in the water column became rapidly enriched (within one day) with 15N-nitrogen after shrimp were fed 15N-enriched feed. By day 15, 6% of the added 15N-nitrogen was in this fraction in the ‘sediment’ tanks compared with 0.4% in the ‘no sediment’ tanks. The particulate fraction in the water column, principally autotrophic nanoflagellates, accounted for 4–5% of the 15N-nitrogen fed to shrimp after one day. This increased to 16% in the ‘no sediment’ treatment, and decreased to 2% in the ‘sediment’ treatment by day 15. It appears that dietary N was more accessible to the phytoplankton community in the absence of sediment. The difference is possibly because a proportion of the dietary N was buried in the sediment in the ‘sediment’ treatment, making it unavailable to the phytoplankton. Alternatively, the dietary N was retained in the NH4+ pool in the water column since phytoplankton growth, and hence, N utilization was lower in the ‘sediment’ treatment. The lower growth of phytoplankton in the ‘sediment’ treatment appeared to be related to higher turbidity, and hence, lower light availability for growth. The percentage 15N-nitrogen detected in the sediment was only 6% despite the high capacity for sedimentation of the large biomass of plankton detritus and shrimp waste. This suggests rapid remineralization of organic waste by the microbial community in the sediment resulting in diffusion of inorganic N sources into the water column. It is likely that most of the dietary N will ultimately be removed from the tank system by water discharges. Our study showed that 15N-nitrogen derived from aquaculture feed can be processed by the microbial community in outdoor aquaculture systems and provides a method for determining the effect of dietary N on ecosystems. However, a significant amount of the dietary N was not retained by the natural biota and is likely to be present in the soluble organic fraction. [Copyright &y& Elsevier]

Abstract The present study compares the relative costs of stocking ponds with postlarvae from wild or domesticated Kuruma shrimp, Penaeus japonicus (Bate), broodstock. Wild broodstock were obtained from a commercial trawler. Domesticated broodstock were reared to harvest size (wet weight = 25 g) on a commercial farm and then transferred to controlled environment tanks where they were grown to a final wet weight of 50 g. The costs of stocking ponds with postlarvae were calculated from the observed reproductive output, the costs of purchasing wild broodstock and the costs of domesticated broodstock production in the controlled environment facility. Domesticated P. japonicus spawned comparable numbers of eggs to wild broodstock of similar size, but hatching success was significantly lower. A total of 12 domesticated P. japonicus broodstock would be needed to produce the postlarvae to stock a 1-ha pond, compared to only six wild broodstock. However, the much higher relative costs of wild broodstock means that the cost of using their postlarvae would be Aus$851 per pond compared to Aus$390 for domesticated broodstock. The present authors conclude that the use of domesticated P. japonicus broodstock could be a cost-effective alternative to wild broodstock in Australia and in other countries where P. japonicus is farmed. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined the impact of the cyanobacterium Trichodesmium spp. blooms on the penaeid prawn larvae. Development of the larvae of the prawn Penaeus merguiensis; Details on the usage of electron microscopy; Methodology used to conduct the study; Results of the study.

Abstract: In those shrimp species comprehensively studied, polyploidy is currently the only known technique that can achieve the dual outcomes of reproductive sterility for genetic protection and skewing sex ratios towards a high proportion of females, which are larger than males in all of the penaeid shrimp. This review article aims to collate the scientific knowledge and global shrimp industries experience, thoughts, perceptions and publications from numerous formats and languages on shrimp polyploidy to provide an overview of its global status and future direction. At present there is a significant amount of literature on polyploidy in penaeid shrimp; however, some is difficult to access and several observations by Dr. Xiang''s research group at the Institute of Oceanology, China, and Dr. Preston''s CSIRO Food Futures Flagship research group at CSIRO Marine and Atmospheric Research, Australia have not yet been published. For any researcher or shrimp industry member who has attempted to, or whom would like to thoroughly search the literature to gain a complete understanding of the current state of shrimp polyploidy, this publication will be an invaluable source of reference material, some of which is published here for the first time. [Copyright &y& Elsevier]

Abstract: In this study we induced triploids in a single family of Black Tiger shrimp (Penaeus monodon) using chemical shock induction to stop the second meiotic division. The family was reared from egg to harvest age (post-larval stage 184) in a combination of commercial hatchery and experimental controlled environment tank rearing systems. During the rearing phase ploidy, survival, weight, sex ratio and gonad morphology of sibling diploids and induced triploids were periodically assessed. This is the first published report of the culture performance of triploid P. monodon. The induction rate of triploids at the nauplii stage was 83.4±0.04% but this proportion had dropped to 62.45% by the time shrimp metamorphosed to the protozeal stage. Proportions of triploids remained fairly constant throughout the remaining larval and early post-larval stages (ranging from 60.47% to 72.38%), but dropped again to 56.32% by the time shrimp reached harvest age. The reduction in triploid rate from egg to harvest age is thought to be due to a combination of factors including heightened sensitivity of triploids to continual handling and general lower survival of triploids compared to diploids. Once shrimp reached harvest age diploid females were significantly heavier (42.95±2.43g, P <0.05) than all other categories of shrimp. There was no significant difference in weight (P >0.05) between triploid females, diploid males and triploid males (35.14±2.26g, 34.02±0.89g and 31.79±1.56g respectively). The final sex ratio of harvest age triploid P. monodon was 1 female:1.625 males. Histological examination of harvest age female and male gonads revealed a drastic reduction in the development of both ova and sperm in triploid shrimp compared to diploids. The limited numbers of oocytes and sperm produced in triploids failed to fully mature by harvest age. No sperm were observed within spermatophores of triploids at harvest age when a gross morphological examination was performed and no sperm bundles were seen in the vas deferens. Using the same examination technique, diploid harvest age males had sperm within the spermatophores and vas deferens, and sperm bundles. Results indicate that reproductive sterility is likely for both female and male triploid P. monodon. [Copyright &y& Elsevier]

Abstract: The growth, survival and reproductive performance of tank-reared, 2nd generation domesticated Penaeus monodon, originating from founder stocks collected from a population off the coast of Weipa (12°48′, 141°32′), Gulf of Carpentaria, Queensland, Australia, were compared when reared at a standard density for maturation (SD) (approx. 3 individuals m−2) and a low density for maturation (LD) (approx. 1 individual m−2). Growth and survival of the shrimp reared at the two densities in 10·000 L tanks (3.6 m dia.; 10 m2 tank-bottom area) were assessed from 5.5 months of age through to 10.5 months of age. Reproductive performance of shrimp in the two density treatments was assessed from 10.5 months of age for two moult period''s post-ablation under standardized conditions. The weight of the female shrimp at 10.5 months of age (mean±S.E.) was significantly greater at LD (131.2±4.9 g) than at SD (120.3±2.5 g). No difference in 10.5 month weight was found between males at LD (90.9±2.2 g) and SD (87.4±1.5 g). Significantly more spawnings were produced at LD (2.2±0.2 ablated female−1; 3.4±0.6 spawning female−1) than at SD (1.3±0.2 ablated female−1; 2.4±0.6 spawning female−1). The percentage of spawnings that hatched (LD 87.2±5.1%; SD 61.8±6.6%), eggs per spawning (×103) (LD 231±21; SD 148±16) and nauplii per spawning (×103) (LD 39±8; SD 16±3) were also significantly higher at LD. Hatch rates per spawning were low and did not differ between LD (19.0 ±2.7%) and SD (16.8±2.4%). No significant differences in spermatophore weight (LD 0.19±0.02 g; SD 0.20±0.01 g) or sperm count (×106) (LD 6.25±0.77; SD 8.44±1.15) were found between males at the two densities. While egg and nauplii production (×103) were significantly higher at LD than SD when expressed per female (LD 434±115 eggs, 73±26 nauplii; SD: 160±44 eggs, 17±7 nauplii), no significant difference was found when expressed per m2 tank-bottom area of the maturation tanks (LD 272±67 eggs, 46±21 nauplii; SD 271±109 eggs, 29±15 nauplii). Our results found that lowering the maturation density of tank reared P. monodon stocks from approx. 3 individuals m−2 to 1 individual m− 2, over a 5 months maturation period, improved growth of females and reproductive performance when expressed per spawning or per female. However, no significant increases in egg and nauplii production were obtained by reducing the maturation density when expressed per tank-bottom area. [Copyright &y& Elsevier]

Abstract: The reproductive performance of tank-reared, 2nd generation domesticated Penaeus monodon was compared when fed on two experimental maturation diet combinations; a control diet (CD) containing a treatment portion of 32.5% squid (Photololigo sp.) and 32.5% bivalves (Plebidonax sp.); and a shrimp-supplemented diet (SSD) containing a treatment portion of 21.6% squid (Photololigo sp.), 21.6% bivalves (Plebidonax sp.) and 21.6% shrimp (sexually mature Penaeus sp. and Metapenaeus sp.). The remaining portion of both diets consisted of 5% polychaetes and 30% commercial shrimp pellets. Broodstock were fed on the diets from approximately 10 months of age until commencement of reproductive assessment at 11 months, and until completion of the assessment when females had completed two moult periods post-ablation. No significant difference in growth, survival, ovarian maturation, spawning and egg production was found between diet treatments (P >0.05). However, the percentage of spawnings that hatched (mean±standard error) (CD 77.5±6.7%; SSD 41.2±8.6%) (P <0.01), egg fertility rates per spawning (CD 60.2±6.1%; SSD 34.4±8.4%) (P <0.05), hatch rates per spawning (including both unhatched and hatched spawnings) (CD 23.3±4.2%; SSD 5.2±1.7%) (P <0.01) and nauplii per spawning (×103) (CD 41±9; SSD 6±2) (P <0.01) were significantly lower for broodstock fed the SSD than the CD. No difference in spermatophore weight or sperm quantity was found between diet treatments (P >0.05). These results indicated that partial replacement of squid and bivalves with sexually mature shrimp in the maturation diet of tank-domesticated P. monodon had a negative effect on egg fertility and hatching. Furthermore, these results highlight the large effect that the final maturation diet can have on reproductive output of domesticated P. monodon broodstock. [Copyright &y& Elsevier]

Abstract: The reproductive performance of reciprocally crossed wild-caught (W) and domesticated lines (L1 and L2) of Penaeus monodon broodstock was assessed over two moult periods under standardised conditions. Significant variations in the reproductive performance of the broodstock from the three sources (W, L1 and L2) were found. Reproductive performance was more dependent on the source of the female broodstock than the male broodstock. W females matured and spawned more rapidly after ablation and more often than L1 and L2 females. The percentage of W females spawning (86.8%) was significantly greater than that for both L1 (38.9%) and L2 females (23.7%). W females had significantly more spawnings (1.99 spawnings female− 1) than the L1 (0. 62 spawnings female− 1) and L2 females (0.37 spawnings female− 1), and spawned within a shorter period after ablation (9.2 days compared with 15.3 days for the L1 and 18.7 days for the L2 females). There was no difference in the numbers of eggs per spawning, percentage of spawnings that hatched, hatch rates and protozoeal metamorphosis rates produced from the W and the L1 tank-reared females. However, the L2 females had significantly lower numbers of eggs per spawning, percentage of spawnings that hatched and protozoeal metamorphosis rates per spawning than the W and L1 females. The lower performance of the L2 stocks, compared with the L1 stocks, demonstrates the variability in reproductive performance that can exist between different domesticated stocks. Our results suggest that the largest improvements in the reproductive output of these tank-reared P. monodon stocks will likely be found through improvements in the quality of the female broodstock. [Copyright &y& Elsevier]

Develops strategies for sampling sediment bacteria in intensive shrimp ponds in Australia. Comparison between the bacterial counts of the pond center and the pond periphery; Correlation between the bacterial numbers in the sediment and the sediment grain size; Role of bacteria in nutrient cycling; Association between nitrogen concentration and bacterial numbers in pond sediments.

Describes an automated spawning detection and alarm system that permits timely collection and manipulation of penaeid shrimp embryos. Components of the alarm system; Applications for multiple spawnings; Effectiveness of the system in detecting spawnings of penaeids and a range of aquatic species that release eggs or embryos directly into the water.