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Modification of freshwater flow regimes can impact estuarine ecosystems at the receiving end of these flows. This is particularly true in tropical areas, such as the wet-dry tropics, where major freshwater flows in the wet season may result in prolonged and large-scale flooding, followed by periods of little or no flow during an extended dry season. Estuarine species, such as the commercially important prawn Penaeus merguiensis, have lifecycles adapted to seasonal flows. The potential effects of flow regulation on estimated catches of P. merguiensis were explored using a Bayesian belief network (BBN) model. Probability statements were generated about the ecological implications of different magnitudes of natural flow, as well as three water-extraction scenarios: 1) reduced flow in the wet season; 2) the introduction of flow in the dry season; and 3) the combination of scenario one and two. Thresholds of freshwater flow that affect the likelihood of high prawn catches in the fishery were identified, and the cumulative effects explored. This is the first time that these thresholds have been identified and the model suggests there is little capacity to regulate or modify the freshwater flow without reducing the probability of high prawn catches. [ABSTRACT FROM AUTHOR]

Decapod Hepandensovirus 1 (HDV), formerly known as hepatopancreatic parvovirus, has been associated with stunting, lowered production and outright mortalities in prawns in aquaculture. Despite the fact that broodstock are sourced and aquaculture farms are planned in the regions of northern and Western Australia, data on these parvoviruses from this region are limited. The prevalence of HDV in Penaeus esculentus and Penaeus merguiensis is moderate (34–51%) in southern Western Australia, Exmouth Gulf and the Gulf of Carpentaria but statistically higher (P < 0.05) in Shark Bay (82%). We speculate this is due to the topography of Shark Bay combined with the currents of the Indian Ocean gyre (IOG). Despite an on average 8–12% genomic heterogeneity, the nucleotide sequences of HDV in WA most closely align with HDV in regions associated with the IOG; Thailand, India, Tanzania, Madagascar; eastern Asia, Korea and less commonly, with sequences from the eastern coast of Australia. This potentially changes the paradigm of a single strain of HDV being ubiquitous in Australia and there was little risk in moving broodstock from WA to the eastern states, so there was no testing of broodstock for HDV. There is no strong evidence to clarify whether the strain of HDV in WA P. esculentus came from either its' nearest genetic relatives, P. monodon or P. semisulcatus or from P. merguiensis from the Solanderian province of Australia. P. esculentus HDV appears to be most related to strains within the IOG. The HDV nucleotide heterogeneity of wild prawns contrasts strongly to studies undertaken with prawns from aquaculture where genetic selection may have occurred. [ABSTRACT FROM AUTHOR]

The ability of three proteases producing bacteria such as Pseudomonas aeruginosa , Serratia marcescens , and Bacillus pumilus on the demineralization and deproteinzation efficiency of shrimp waste, for chitin extraction, was investigated. Statistical analysis of data was showed a significant difference between the percentage of demineralization and deproteinization in different bacteria species ( p < 0.05). The highest deproteinization (74.76%) and demineralization rate (78.46%) was obtained with P. aeruginosa and the lowest was observed in the treatment of S. marcescens . Then, chitin was converted to chitosan by deacetylation in the presence of NaOH 50%. The antioxidant activity of chitosan solution was determined using different tests. The highest activity (DO 700 nm = 0.74, DO 695 nm = 0.31) was observed for chitosan sample at concentration of 1000 μg/ml. The antioxidant potential of the hydrolysates was also evaluated. The highest reducing power in a volume of 400 μl hydrolysate of S. marcescens and the highest total antioxidant capacity in a volume 100 μl hydrolysate of B. pumilus were observed. These results indicated that the P. aeruginosa bacterium in comparison with other bacterial strains, higher ability to remove proteins and mineral from shrimp waste. Therefore, the use of this bacterium is recommended for protein and mineral removal from marine crustaceans. [ABSTRACT FROM AUTHOR]

Penaeus merguiensis hepandensovirus (PmeDV) is a strain of the hepatopancreatic parvoviruses that causes overt mortalities and stunting in survivors in many penaeids around the tropical and temperate world. This study was to investigate if RNA interference (RNAi) could be used to ameliorate pre-existing PmeDV infection in a therapeutic manner rather than in a simultaneous exposure when delivered via live bacteria in pelleted food. One hundred and fifty Australian Penaeus merguiensis testing positive for PmeDV by PCR were divided into 5 treatment groups which were bled weekly for viral copies measured by real time PCR and treated for 5 weeks with the appropriate RNAi. The treatments were no treatment control, carrier fish oil, plasmid delivered nonspecific RNAi, plasmid delivered specific RNAi and plasmid delivered specific RNAi in live Escherichia coli . Statistically, the specific RNAi microencapsulated in live E. coli was the best overall treatment against pre-existing PmeDV when delivered in the food. Specific RNAi in bacterial cells had the lowest mortality (P < 0.0001), the highest relative percentage survival (68%), most prawns with no detectable viral copies (53%) and it was equal to the nonspecific RNAi with the lowest viral copies when virus was detected (P < 0.0001). The naked plasmid, specific RNAi and the nonspecific RNAi as plasmids were very similar being the next most protective across all measures. The week of the trial was not significant (P > 0.05), but the week by treatment interaction was (P < 0.05) with the number of RNAi-control prawns significantly increasing viral copies at week 2 whilst copies in other treatments fell. Also, fish oil lost its protective effects by 5 weeks as evidenced by statistically increased number of viral copies. Overall, this study showed that RNAi microencapsulated in live E. coli and fed via pelleted feed could increase survival of P. merguiensis and lower viral copies in pre-existing infections of PmeDV. This methodology herein should be the simplest for farmers to apply and when utilized, these results should allow farmers to increase yields, profitability and therefore, sustainability. [ABSTRACT FROM AUTHOR]

Abstract: The ribosomal DNA internal transcribed spacer 1 (ITS1) was investigated in the search for additional genetic marker that is suitable for population studies of the penaeid shrimps. The sequence variations of the ITS1 were determined and found to be informative in estimating phylogenies in that they differentiate four species of penaeid shrimps, namely Penaeus merguiensis, Penaeus silasi, Penaeus monodon and Penaeus semisalcatus and the populations of P. merguiensis collected in the Gulf of Thailand and the Andaman Sea. The length of the ITS1 ranged from 499 to 772 bp, with a GC content of 63.30–67.37%. Four microsatellite loci are found in the ITS1 at 5′ end and the middle of region and seem to be associated with sequence divergence and size variation in Penaeus species. Some microsatellites were found in only one specie, (GCGA)4 in P. semisalcatus and (CGGA)4–9 in P. monodon. These microsatellite regions are considerably long enough and the level of intragenomic variation in P. merguiensis is less than that between different species, hence, provide a great potential use in the population studies. [Copyright &y& Elsevier]

Abstract: Apoptosis is a fundamental cellular process that plays a critical role in normal development and tissue homeostasis, eliminating from an organism unwanted cells, including damaged and virus-infected cells. In order to investigate the significance of apoptosis in response to viral infections in crustacean, we have cloned a caspase gene (cap-3) from the white shrimp, Penaeus merguiensis infected with white spot syndrome virus (WSSV). The deduced amino acid sequence of the protein named CAP-3 was 320 amino acids in length and contained the highly conserved pentapeptide QACRG recognized as the active site of caspase. CAP-3 showed similarities to the insect caspase, Spodoptera frugiperda Sf caspase-1 and the caspases of Spodoptera littoralis, Bombyx mori, Drosophila melanogaster and Anopheles gambiae, which in turn belong to the group of human caspase-3, caspase-7 and CED-3. The recombinant CAP-3 protein prepared from Escherichia coli had enzymatic activity when assayed using a luminescent substrate specific for the cleavage target site for human caspase-3, implying that CAP-3 functioned as caspase-3. There was a high level of expression of this gene product in moribund shrimp infected with WSSV. [Copyright &y& Elsevier]

Abstract: The effects of fish predators, light phase, habitat structure and prawn size on the habitat preferences of juvenile Penaeus (Fenneropenaeus) merguiensis de Man were examined with laboratory experiments. The behaviour of juvenile P. merguiensis within habitats of different structural complexity was also examined. Experiments were carried out in a tank (1.8 m diameter) divided into four habitats representing: bare substratum, leaf litter (little vertical structure), mangrove pneumatophores (regular vertical structure) and mangrove woody debris (heterogeneous vertical structure). The location of 10 prawns was monitored over 270 min (135 min light and 135 min dark), with different prawns five times for each combination of prawn size class, and predator (no predator; Arius graeffei Kner and Steindachner and Lates calcarifer Bloch). In the absence of predators and during the light phase, when observations on prawn behaviour were made, swimming was the most common behaviour (of seven mutually exclusive behavioural categories) with few differences in behaviour between sizes. All size classes of juvenile P. merguiensis selected vertical structure (mangrove debris and pneumatophores) over low vertical structure (leaf litter and bare substratum), in both light and dark conditions and in the presence or absence of predators. When L. calcarifer was present, the selection by prawns of the mangrove-debris habitat increased significantly. This was attributed to an increase in predation risk in the other habitats. L. calcarifer rarely pursued prey amongst the mangrove-debris structure, compared to habitats with less heterogeneous vertical structure (pneumatophores, leaf litter and bare substratum). [Copyright &y& Elsevier]

Abstract: This study investigates the distribution of three trace elements (Cd, Cu and Zn) in tissues (exoskeleton, abdominal muscle and hepatopancreas) of two shrimp species (Penaeus merguiensis and Penaeus semisulcatus). Special emphasis in this study was placed on evaluating the effects of storage conditions on redistribution of the elements and moreover the potential roles of metallothionein in tissue redistribution. The specimens were collected from the northern part of Persian Gulf during September 2001 and January 2002. The concentrations of metals in the tissues were measured using an Inductively Coupled Plasma-Atomic Emission Spectrophotometer (ICP-AES) and an ICP-Mass Spectrometer (ICP-MS). Metallothionein levels were determined using Differential pulse polarography. Results show a similar hierarchy for Cd and Cu concentrations among different tissues as follows: hepatopancreas>exoskeleton>muscle; and for Zn, the hepatopancreas again contained the highest levels, though there were not any significant differences in Zn concentrations between muscle and exoskeleton. Significant differences were found between the species in the case of Cd and Zn concentrations. Cd and Zn levels in P. semisulcatus were markedly higher than in P. merguiensis. In general, there were highly significant differences among the storage conditions from accumulation the selected trace elements and metallothionein in both species point of view, but in most cases, no significant differences could be observed among the fresh, refrigerated and frozen specimens of P. semisulcatus. In regards to Zn and Cu accumulation in edible (muscle) tissues of P. merguiensis, optimum conditions for frozen storage is −30 °C as ice-frozen, and in terms of short-term storage, 1-day refrigeration is recommended. The redistribution of Zn and Cu during the storage period can be attributed to the role of metallothionein in their transport from organ(s) to muscle during storage. The variations in pH values measured in the muscle of P. merguiensis in different storage conditions showed a similar trend with metallothionein, Zn and Cu. In contrast, it appears that cadmium is transported from muscle to the other tissues. Exoskeleton is probably one of the recipient tissues of cadmium. The inter-elemental relationships were assessed for each species, separately. A significant positive relationship was observed between the concentrations of Zn and metallothionein in P. semisulcatus, whereas in P. merguiensis, Cd concentrations decreased significantly with increasing metallothionein. Highly significant differences between the sexes in Cu and Zn contents could be detected. The differences between the sexes in the levels of Zn and Cu were significantly greater in P. semisulcatus. Highly significant size-related differences were found in the levels of Cd, Cu and metallothionein in the selected tissues of the shrimp species. Comparison between the mean concentrations of the elements in muscle tissue and existing guidelines indicate that in nearly all cases, the concentrations were well below permissible levels for human consumption. The only exception was observed regarding mean values of Cd, which was somewhat greater than some of the recommended levels. [Copyright &y& Elsevier]

Polymorphisms of nuclear DNA markers were used to study the genetic variation and differentiation among populations of Penaeus merguiensis in Thailand. The data consisted of three nuclear loci analysed for 163 individuals from five populations collected from the Gulf of Thailand (Trad, Surat Thani and Songkhla) and the Andaman Sea (Satun and Trang). The multilocus FST estimated at three nuclear loci revealed great and highly significant differentiation between the Gulf of Thailand and Andaman Sea (FST=0.203, P<0.001), mostly due to the polymorphism of locus PvAmy. In addition, significant population differentiation was also found within the Gulf of Thailand. These results were compared to that of a previous mitochondrial DNA survey spanning the same geographical range where two divergent mitochondrial clades were reported. The present study brings support to the fact that the existence of these two clades is not due to a mixture of cryptic species but reflects their phylogeographic origin. The strong genetic structure of P. merguiensis on each side of the Thailand peninsula for both mitochondrial and nuclear genes could thus be linked to the phylogeographic divide between Indian Ocean and Pacific forms on the west and east sides respectively. [Copyright &y& Elsevier]

During October to December 1997, we trawled estuarine habitats in the Joseph Bonaparte Gulf (JBG) to determine the distribution of juvenile red-legged banana prawns, Penaeus indicus (H. Milne Edwards, 1837) and white banana prawns, Penaeus merguiensis (de Man, 1888). We made 229 beam-trawls at 185 sites, mostly over a 100-m path (3-min duration). A Global Positioning System (GPS) receiver was used to verify our location. During October to December 1998, we intensively resampled three of the rivers that were sampled in 1997 to confirm the gulf-wide distribution of P. indicus and P. merguiensis and to investigate the microhabitat use of P. indicus. We chose previously sampled and new sites in Forsyth Creek (eastern JBG), the Lyne River (Cambridge Gulf), and the Berkeley River (western JBG). We made 249 trawls at 21 sites, mostly over 100 m.Juvenile banana prawns were abundant in eastern JBG, Cambridge Gulf and western JBG. They were not abundant in southern JBG, although fewer trawls were made there, due to its inaccessibility. In eastern JBG and Cambridge Gulf, over 96% and 73% (respectively) of juvenile banana prawns were P. indicus and they were more abundant there than in the western JBG. Conversely, in the western JBG over 93% of the juvenile banana prawns were P. merguiensis and they were more abundant than in the eastern JBG and Cambridge Gulf. The Lyne River in the northwestern Cambridge Gulf seems to be the transition zone; both P. indicus and P. merguiensis are equally abundant.P. indicus are most abundant on the mangrove-lined muddy banks of waterways within mangrove forests, similar habitats to P. merguiensis. Within these habitats, they were most abundant in gutters and small creeks, rather than rivers and large creeks. Few P. indicus or P. merguiensis were caught in 100 m2 trawls undertaken midriver (on the channel bottom and on emergent banks), although these habitats may be only 100 m from the mangrove-lined habitats. In all creek and river habitats, both species are most catchable at low tide (irrespective of daylight or darkness) when they move out of the mangrove forests and accumulate in the remnant water bodies.The offshore fishery for P. indicus is in northwestern JBG in waters 50–80 m deep, about 300 and 200 km, respectively, from where juveniles are abundant in their extensive inshore habitats in east JBG and in Cambridge Gulf, demonstrating a geographical separation of the juvenile and adult phases. Postlarval P. indicus, spawned offshore, must use tides and currents to travel south and east to reach nursery habitats. Emigrant subadults must migrate north and west, across relatively shallow inshore sand substrates (30–40 m deep) to reach their offshore habitats. [Copyright &y& Elsevier]

The combined effects of temperature and salinity on the hatching success, survival and development of the larval stages of Penaeus merguiensis were investigated in a 4×2 factorial designed experiment employing two temperatures (29±1 and 33±0.5 °C) and four salinities (25, 30, 35 and 40 ppt). Best percentage of hatch was obtained at 33 °C and 35 ppt (87%) followed by 29 °C and 35 ppt (82%). Similarly during naupliar stages, high survival rate was obtained at 33 °C and 35 ppt (89%). Metamorphosis cycle during the protozoeal stages (protozoea 1 to postlarva 1) was extended and survival rate decreased at 25 ppt. Development to PL1 was faster at 33 °C (7–8 days) as compared to 29 °C (8–10 days) regardless of the salinity levels. Maximum survival during the protozoeal stages was at 35 ppt followed by 48% at 33 °C and 45% at 29 °C. Results showed that salinity exerted a greater influence than temperature on the survival and development of larvae. Based on the results, the best temperature–salinity combination for larval survival and metamorphosis of P. merguiensis is 33 °C and 35 ppt. A salinity range of 30–35 ppt is ideal for larval development. [Copyright &y& Elsevier]

Closely related species, Penaeus merguiensis and Penaeus silasi from Thai waters, were genetically examined using variation observed in 558 base pairs (bp) of sequence from cytochrome oxidase subunit I (COI) gene of mtDNA. The sequence divergences of COI between P. merguiensis and other Penaeus species were 5.76–6.15% (P. silasi), 13.17–13.97% (Penaeus indicus), 16.43% (Penaeus vannamei), 16.63% (Penaeus monodon), and 18.37% (Penaeus japonicus). From the alignment reported that there were four clades on phylogenetic tree, the distinction of the two monophyletic clades was referred as P. merguiensis, one monophyletic clade within P. silasi and P. indicus. These results point toward the possibility of P. merguiensis being a complex of two cryptic species or a single species with strong phylogeographic subdivision. [Copyright &y& Elsevier]

Two environmental manipulation protocols were tested against a current maturation technique (CONTROL) in an 81-day experiment. PROTOCOL 1 mimicked changes in the natural environment from winter to spring when ovarian maturation and spawning in Penaeus merguiensis starts. PROTOCOL 2 evaluated whether a clear improvement of temperature from a fluctuation period to a stable one could help trigger ovarian maturation. In phase A (first 30 days) of the experiment, temperature and day length were gradually increased from 22 to 27 °C and from 10 to 14 h, respectively, while light intensity was stepwise reduced from 360 to 240, 120 and 5 lx for PROTOCOL 1. For PROTOCOL 2, light intensity and day length were manipulated as for PROTOCOL 1, but temperature was cycled from 22 to 27 °C every 3 days. In phase B (the following 30 days) temperature, light intensity and day length were stably maintained at optimal levels (27 °C, 5 lx and 14 h light, respectively). During phase B, the proportion of female prawns reaching stages III and IV was significantly (P<0.05) highest in PROTOCOL 1 and lowest in the CONTROL. Of the total spawns by unablated females recorded in this phase, 55.6% was in PROTOCOL 1, 33.3% in PROTOCOL 2 and only 11.1% in the CONTROL. Mass spawning was induced by unilateral eyestalk ablation on day 60. Spawning performance of prawns were monitored for a further 21-day period (phase C). Overall, PROTOCOL 1, PROTOCOL 2 and the CONTROL produced 2.36, 1.96 and 1.53 million eggs, respectively. The latency period of spawners was shortest (P<0.05), whereas the proportion of spawners, fecundity, spawning rate and egg production/female were all improved in PROTOCOL 1. An improvement of prawn growth was observed in PROTOCOL 2. This study suggested that environmental manipulation could improve ovarian maturation and spawning rate of pond-reared P. merguiensis. [Copyright &y& Elsevier]

The effects of light intensity (I, 750 and 75 lx) and photoperiod (P, 12L/12D and 7L/5D) on moulting and growth of Penaeus merguiensis were investigated over 12 weeks under laboratory conditions. Both light intensity and photoperiod significantly (P<0.05) influenced the percentage weight gain (PWG), but did not influence moult frequency or moult interval. Mean PWG of prawns cultured at 750 lx was 198.4%, significantly (P<0.01) higher than those cultured at 75 lx (168.1%). Imposing two light/dark cycles (7L/5D) in 24 h resulted in a significantly higher growth of prawns (P<0.05) than the normal photoperiod (12L/12D). Prawns cultured at 750 lx had a lower food conversion ratio (FCR, 1.485) than those cultured at 75 lx (1.590, P<0.05). The effect of light intensity on prawn growth was found to be stronger and more immediate than that of photoperiod. There was no interaction between light intensity and photoperiod. Although not significantly different (P>0.05), prawns cultured at 750 lx tended to moult more frequently. Sexual dimorphism was not observed within the range of tested prawns. [Copyright &y& Elsevier]

The maturation rate and spawning performance of ablated Penaeus merguiensis were significantly (P<0.05) higher at 27°C than at 23°C. Increasing the temperature from 23°C to 27°C further improved spawning performance (P<0.05), whereas reducing the temperature from 27°C to 23°C impaired spawning. The effect of temperature during the inducing period was more critical than during the holding period. Prawn growth (% of weight gain), however, was not different between 23°C and 27°C over the 60-day experimental period (P>0.05). [Copyright &y& Elsevier]

The effects of prawn age, size, and light intensity on spawning performance of pond-reared Penaeus merguiensis were studied by inducing spawning of prawn broodstock by eyestalk ablation under two different light intensities (bright, 1100 lx and dim, 2 lx) at three different known ages (7, 10, and 13 months old). For each age group (except the 13-month-old group), two distinguished size classes (large and small) were established to reveal the effect of prawn size. Results showed that light intensity did not affect spawning performance of prawns of different ages and sizes (P>0.05). In contrast, age had a significant effect on spawning performance of prawns (P<0.01). The overall spawning performance of the prawns increased from 7 to 10 months old and started to decline at 13 months old. Within the 7- and 10-month-old groups, larger prawns produced a superior overall spawning performance compared with smaller ones (P<0.01). Comparison across the size range of the experimental prawns showed that spawning performance improved with the increase of body size. However, the 13-month-old prawns, although having a similar size as large 10-month-old prawns, had an inferior spawning performance (P<0.01). Survival and growth of ablated prawns significantly decreased with the increase of prawn size and age (P<0.01). It is suggested that spawning performance of pond-reared P. merguiensis peaked between 10 and 12 months old, and broodstock should be bred during this period for hatchery production. [Copyright &y& Elsevier]

The effect of three levels of light intensity (BRIGHT: 1100 lux; DIM: 2 lux; and DARK: 0 lux) on ovarian maturation and spawning of Penaeus merguiensis was investigated. The proportion of spawners, latency period, spawning rate, fecundity, spawning interval and number of days spent at stage IV per spawn were not significantly different (P>0.05) among the three light intensity treatments. Compared to dim light, bright light did not adversely affect the maturation and reproductive performance of ablated prawns. However, the percentage of spawning at stage III (31.6%) and mortality (26.7%) were significantly higher in the DARK treatment (P<0.05). A trend of increasing fecundity with an increase in light intensity was observed. Also, the hypothesis of whether the prawn eye is the only light receptor involved in ovarian maturation and spawning was tested by covering the remaining eye of ablated prawns with prepared caps made from black heat-shrinkable tubing (polyolefin). These prawns were held under 1100 lux (BRI-COV treatment) and 2 lux (DIM-COV) with the DARK treatment as the control group. The proportion of spawners was lowest in the BRI-COV treatment and highest in the DARK treatment (P<0.05), whereas there was no significant difference between these two treatments and the DIM-COV treatment. The DARK treatment, however, had a significantly higher spawning rate (P<0.05). The significantly higher percentage of spawning at stage III and less time spent at stage IV per spawn of prawns in the DARK treatment (P<0.05) compared with the DIM-COV and BRI-COV treatments suggest that the prawn eye may not be the only light receptor involving in ovarian maturation and spawning in P. merguiensis. [Copyright &y& Elsevier]

The effect of light intensity on ovarian maturation and spawning of unablated female Penaeus merguiensis was investigated in a 4 week experiment. The experiment had two different light intensity treatments: BRIGHT (1100 lx) and DIM (2 lx). At starting time, there were four groups of broodstock with four different ovarian maturation stages (II, III, IV and V) in each treatment. Results showed that light intensity plays an important role in controlling ovarian maturation of prawns, especially at the later stages (stages III and IV). Bright light showed an inhibitory effect, whereas dim light favoured ovarian maturation and spawning. Ovarian regression occurred in most stage III and stage IV prawns kept under bright light, while prawns at the same stages developed their ovaries further and spawned under dim light. Proportion of spawners (12.5%), mean number of spawns per prawn (0.12) and mean fecundity (87,300) of prawns were significantly lower (P<0.05) in the BRIGHT treatment, compared to the DIM treatment. Under light intensity of 2 lx, 41.7% of prawns spawned, producing 0.5 spawn per prawn on average with a mean fecundity of 117,300. The results also suggest that the sensitivity of broodstock to light increased from stages II to IV of ovarian maturation, while there were some evidence of light adaptation in stage V broodstock. This study confirmed multiple spawning of unablated P. merguiensis for the first time. Rematuration period was short (6–7 days). [Copyright &y& Elsevier]

This study investigated short-term effects of high temperature on survival and feed consumption of the tropical banana shrimp Penaeus merguiensis. Three 7-day experiments were conducted with three age group of P. merguiensis : PL 25 (postlarvae 25 days old), PL 50 and PL 100. In these experiments water temperature was maintained at 27 °C in the control, but increased to 32, 35, 38 and 41 °C at a constant rate of 1 °C every 8 h. Once reached, the desired level of water temperature was kept stable until the end of the experiment. Results showed that water temperature above 35 °C significantly reduced survival of the experimental shrimp (P < 0.01). Shrimp survival was only 24% and 0% in the 38 °C and 41 °C treatments, respectively while ranging between 91 and 96% in the other treatments. Feed consumption was significantly affected by both ambient water temperature and shrimp size (P < 0.01). It was highest in the 41 °C treatment (1.7%/shrimp×day), followed by the 38 °C treatment (1.3%/shrimp×day) (P < 0.01). Feed consumption in the PL 50 and PL 100 age groups was 3.5 to 4.0 fold higher than that in the smallest age group PL 25 (P < 0.01). This study suggests that P. merguiensis in tropical areas may survive water temperature up to 35 °C in commercial shrimp ponds. • This study is reports short-term tolerance of Penaeus merguiensis to high water temperatures. • Shrimp survival were not different from 27 to 35oC, but significantly reduced at 38oC and 41oC (P < 0.01) • Feed consumption was not different from 27 to 35oC, but significantly increased at 38oC and 41oC (P < 0.01) • P. merguiensis could be farmed during the hot season when water temperature may reach 35oC. [ABSTRACT FROM AUTHOR]