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The combined effects of temperature (23 and 27 °C), light intensity (1100 and 2 lux or ≈ 21.5 and 0.04 µEinst m[sup -2] s respectively) and photoperiod (10 h light/14h dark and 14 h light/10 h dark) on ovarian maturation and spawning performance of ablated pond-reared Penaeus merguiensis were investigated in a 51-day experiment. The results showed that temperature was the most influential factor, followed by light intensity, whereas the effect of photoperiod was minor. As the maturation process progressed, the effects of temperature and light intensity became stronger while that of photoperiod became less significant. Temperature significantly affected all the reproductive parameters assessed. Prawns in the 27°C treatments outperformed those in the 23 °C treatments (P< 0.05). The effect of light intensity was found to have a significant effect (P < 0.05) only on the proportion of spawners (prawns that spawned) and spawning rate. More prawns spawned at a higher rate under dim light (2 lux) than under strong light (1100 lux). Photoperiod affected only the proportion of prawns reaching stage III of ovarian development (P<0.05). There were interactions between temperature and light intensity affecting the proportion of prawns reaching stage III and, although not significantly, the proportion of spawners (P=0.177), fecundity (P=0.134) and survival (P=0.061). Overall, it is recommended that a combination of 27 °C, 2 lux and 10 h light/14 h dark is suitable for the maturation of pond-reared P. merguiensis. There were indications that temperature can be used to control the rate of ovarian maturation. Also, it is possible to increase light intensity up to 11001ux in P. merguiensis hatcheries if prawns are ablated. [ABSTRACT FROM AUTHOR]

This 12-month preliminary study investigated the development of sexual characters, primary sexual maturity, ovarian maturity and spawning performance of pond-reared Penaeus merguiensis in relation to culture conditions in south-east Queensland, Australia. Post-larvae of P. merguiensis were produced and cultured in two 60-m[sup 3] tanks during the first 14 weeks. Before winter, they were harvested and stocked in three different overwintering facilities: a 200-m[sup 2] covered pond, two 60-m[sup 3] outdoor tanks and a 15-m[sup 3] indoor, recirculated tank at a stocking density of 10 individuals m[sup -2]. The development of sexual characters was found to be similar to that reported previously in wild P. merguiensis. Males matured at younger ages and smaller sizes than females. Overall, the average size at primary sexual maturity of pond-reared P. merguiensis was 23.1 mm carapace length for males (possessed spermatophores) and 29.3 mm for females (being impregnated). Water temperature and the availability of natural food strongly influenced prawn growth, maturity rate and their subsequent spawning performance. Growth, maturity rate and spawning performance of prawns in the covered pond were significantly higher than in the other overwintering facilities. Prawns started mating at 6–7 months, reached full ovarian maturation and spawned as early as about 8 (peaked at 9–11) months from hatching, producing high fecundity and viable larvae. There was a strong relationship (P < 0.001) between prawn size and fecundity. The results of this study suggest a potential for using pond-reared broodstock P. merguiensis for hatchery production and for domestication or selective breeding programmes. [ABSTRACT FROM AUTHOR]

An experiment was conducted to investigate the effect of light intensity just prior to and during spawning of Penaeus (Fenneropenaeus) merguiensis de Man in the laboratory. Neither the presence of light nor light intensity (0, 10 and 1100 lux) had a significant effect on the spawning process or hatching rate in P. merguiensis. Difference in the percentage of spawners, percentage of incomplete spawning, fecundity and hatching rate were all insignificant (P > 0.05) among the three light treatments. However, spawning was delayed (up to 21 min on average) under 1100 lux with a high percentage of incomplete spawning, compared with the Control (0 lux). For the first time, spawning behaviour of P. merguiensis was observed and fully described. The spawning process can be divided into four phases: dormant, pre-spawning, spawning and post-spawning by distinct behaviour of prawn broodstock. The dormant phase was characterized by a quiescent and non-feeding period, whereas movement of prawn broodstock was active during the pre-spawning and post-spawning phases. Depending on the individual, spawning was completed within 3-5 min. Prawns often stayed still on the water surface during spawning with occasional manoeuvres to change the position. After a short rest at the termination of the spawning phase, prawn broodstock re-exhibited active movement as in the pre-spawning phase, but showing conspicuous care to the deposited eggs. The role of light in controlling ovarian development and spawning, and the behaviour of prawn broodstock in relation to maximizing fertilization rate are discussed. [ABSTRACT FROM AUTHOR]

Shrimp. Penaeus monodon (Fabricius) and Penaeus merguiensis (de Man), culture on East Java is described with special attention to the differences in production characteristics between areas and districts. Traditionally, tambak culture developed along the North coast of East Java where the majority of modern tambaks are still located. The practice never developed extensively on Madura's Island. With the exception of the latter, intensification, starting in 1984-1987. touched all areas. In 1991, the combined production of P. monodon and P. merguiensis reached 3 5 000 Mt. representing a value of US$ 220 x 106 The following year, a decline in total production was noted, mainly caused by a diminished production of intensive farms. Possible causes for this production drop are explored. [ABSTRACT FROM AUTHOR]

Abstract Critical thermal minima (CTMin) were determined for subadults of Penaeus merguiensis acclimated at 15, 18, 21 and 24 °C for 3 weeks. The effect of cooling rate on CTMin was also investigated. The CTMin of prawns from these respective acclimation groups were 5.3, 6.0, 7.4, 9.0 and 4.7, 5.4, 6.0, 7.3 °C at the cooling rate of 1 °C h-1 and 3 °C h-1 respectively. Both acclimation temperature and cooling rate had a significant effect (P < 0.01) on the CTMin. Observation during the acclimation period showed that the growth rate of prawns acclimated at 24 °C was much higher than those acclimated at 21, 18 and 15 °C. The results indicate that P. merguiensis can overwinter in aquaculture ponds in south-east Queensland, Australia, or other subtropical areas and attain good growth if simple overwintering facilities are available. [ABSTRACT FROM AUTHOR]