Quantitative requirement of Penaeus kerathurus for a natural unprocessed diet

Juvenile Penaeus kerathurus (average weight = 0.64 g) were fed three different daily amounts (40%, 60% and 100% of biomass) of an unprocessed and unsupplemented diet composed of 43% anchovy, 33% shrimp head and 24% squid, whose suitability for P. kerathurus had been previously assessed. The experiment was performed with an animal density of 30/m² at 23° C for a period of 180 days. From the results obtained, it is concluded that, of the three feeding rates employed, 100% of biomass was suitable for animals weighing 0.64–1.8 g. For animals 1.8–4.3 g a feeding rate of 60% was appropriate, while a reduction to 40% seemed satisfactory for animals over 4.3 g in this experiment.     

副溶血弧菌对斑节对虾非特异性免疫酶活性的影响

为了研究副溶血弧菌对斑节对虾非特异性免疫酶活性的影响,分别对斑节对虾注射生理盐水和副溶血弧菌,于不同时间点测定肝胰腺和鳃中的总抗氧化能力(T-AOC)、酸性磷酸酶(ACP)、碱性磷酸酶(ALP)和溶菌酶(LSZ)的活性变化。结果显示,与对照组相比,感染副溶血弧菌后,肝胰腺和鳃中T-AOC活性分别于12和6 h达到最大值(P0.05),随后逐渐降低;肝胰腺中ACP活性于3 h显著升高,随后逐渐降低,并于24 h达到最小值(P0.05),而鳃中ACP活性于12 h达到最大值,随后逐渐降低,并于48 h显著低于对照组(P0.05);肝胰腺和鳃中ALP活性整体均呈现出先升高后下降的趋势,但未出现显著低于对照组的现象;肝胰腺和鳃中LSZ活性均于3 h显著升高至最大值(P0.05),随后逐渐恢复至初始水平。研究表明,副溶血弧菌感染对斑节对虾非特异性免疫酶活有显著影响,对其机体免疫防御系统有明显的破坏作用。     

Bacterial flora in the digestive tract of prawns, Penaeus japonicus Bate

Bacterial flora in the gut of wild cultured prawns, Penaeus japonicus Bate, were investigated and the isolated strains were classified to genera. The flora in the water and mud environment which the prawn inhabits were also investigated. In the water of the prawn culture tank, the highest bacterial number was counted in the zoea stages (1.8 × 10⁵ /ml) and the numbers decreased from the end of the mysis stage to the postlarval stage.Few differences in composition were observed between the two populations. In the digestive tract of the zoea, Vibrio spp. were the dominant genera. In the adult stage, Pseudomonas spp. were the most abundant in the flora of the digestive tract of prawns cultured for 126 days. One prawn that grew poorly had large numbers of the Aeromonas and Vibrio groups in the digestive tract. In the digestive tract of wild prawns, the Pseudomonas group was the dominant bacterial population.     

Breeding of Penaeus monodon Fabricius in laboratory recirculation systems

From March to May 1978 over 2 million nauplii were hatched from 34 batches of eggs obtained from five Penaeus monodon females. Females of 50–63 mm carapace length, with one eyestalk removed, spawned viable eggs repeatedly within intermoult periods of 20–30 days indicating that one impregnation was sufficient to fertilize several batches of eggs spawned within one intermoult period. A fresh impregnation was necessary after each moult. The number of eggs per batch varied from 19 000 to 460 000 (mean 217 635) and did not decrease with successive batches. The mean hatch-rate was 30.5% and the mean number of nauplii per brood was 66 000. There was a tendency to a lower hatchrate for batches of eggs produced towards the end of an intermoult period. Samples of larvae from 15 broods were cultured to the post-larval stage at densities of 40–250 larvae/l. Mean survival in 3-1 cultures was 79% but was <13% in larger-scale trials.     

Successful spawning of cultured Penaeus monodon Fabricius after eyestalk ablation

Preliminary experiments resulted in successful spawning of captive stock of the prawn Penaeus monodon, or “sugpo”, to complete the life cycle and produce a viable F₁ generation of larvae. Gonadal development was induced using eyestalk ablation techniques on sexually mature females. Removal of one eyestalk was found to be sufficient to induce gonadal development, whereas bilateral ablation indirectly resulted in high mortality of the treated females. By comparison, successful spawning had not occurred in unablated animals after 9 months.Fry hatched from wild adult stock and reared to 25-day postlarvae were further impounded in brackishwater experimental ponds and reared for 4 months. A transfer of 1 500 animals were then made to marine pens. After a further 10 months, 600 animals were selected for the experiment; healthy females were ablated unilaterally and placed with 100 males for a further 9 months. Of the remaining 400 specimens, 200 were used as controls and the remainder ablated bilaterally, Seven of the 23-month old females with one eyestalk removed had spawned successfully by January 27, 1976.Egg numbers, hatching rate and larval survival compared favorably with data obtained from females of oceanic origin. It is not known if the success of the experiment was entirely due to the effect of ablation or to the choice of a suitable environment. Work is continuing to induce gonadal development under more closely controlled conditions to overcome the inadequate and unreliable supply of spawners.     

Bionomics of Penaeus kerathurus transplanted into Lake Quarun (Egypt)

The total catch of prawns from the Egyptian Mediterranean waters decreased substantially from 7.23 thousand t in 1962 to 1.06 thousand t in 1976. To compensate for this loss, Lake Quarun, an inland closed saline basin in Middle Egypt, was selected for seeding and culture of prawn fry.The bionomics of Penaeus kerathurus, such as composition and distribution of the catch, growth, length-weight relationship, maturity stages of the females, and food, were investigated to confirm the suitability of Lake Quarun for marine prawns. The study showed that P. kerathurus have an approximate monthly growth rate of 10.0 mm for females and 5.0 mm for males (condition factor 0.62 and 0.58, respectively). The growth rates and condition factors in Lake Quarun did not vary much from those observed for stocks in the Mediterranean Sea. P. kerathurus became abundant in the southwest section of Lake Quarun. Futther studies are recommended to increase prawn propagation in the lake, but the preliminary results indicate that an inland lake fishery for marine prawns can be established.     

Predation and energetics of Penaeus indicus (Decapoda: Penaeidae) larvae feeding on Brachionus plicatilis and Artemia nauplii

Brachionus plicatilis and Artemia nauplii were fed to a number of larval stages of the penaeid prawn Penaeus indicus to determine ingestion rates, larval energy requirements and to establish at which stage larval predation commenced. The raptorial feeding rates were then contrasted on an energy basis with filter feeding rates for P. indicus larvae to compare the relative efficiency of these two feeding mechanisms. Brachionus was first eaten as early as protozoea 1 to protozoea 2, while the maximum ingestion rate of 300 rotifers larva^?1 d^?1 (1.06 J larva^?1 d^?1) was obtained during protozoea 3 to mysis 1. Artemia were effectively ingested by P. indicus protozoea 3 (4.1 J larva^?1 d^?1) to post-larva (8.2 J larva^?1 d^?1). Daily energy intake rate from filter feeding increased from 1.1 J larva^?1 d^?1 during protozoea 1 to reach a peak of 5.32 J larva^?1 d^?1 during mysis 3 after which it declined to 2.66 J larva^?1 d^?1 during the post-larval stage. This decline in energy intake from filter feeding with a concomitant increase in energy intake from Artemia predation demonstrates a predominant feeding mode changeover point during mysis 3. Energy intake was consistently low with Brachionus, indicating that it may be unnecessary for commercial culture purposes.     

Lipid content and composition of cultured Penaeus merguiensis fed with animal food

The lipid content and composition of cultured Penaeus merguiensis were examined by lipid extraction, thin-layer chromatography and capillary gas chromatography. The lipid content, 1.99% fresh weight, was higher than in other penaeids, but not especially so. The major lipid classes were phospholipid (47% total lipid), free sterol (27%) and triacylglycerol (17%), with smaller amounts of alkyldiacylglycerol, partial glycerides and free fatty acid. The fatty acid composition was moderately unsaturated and there were no signs of the accumulation of plant fatty acids typical of prawns fed diets supplemented with seed soils. In the light of these results, and of previous feeding studies on penaeids, it is concluded that animal lipid is probably an essential component in the diet of P. merguiensis, enabling it to maintain a normal lipid class and fatty acid composition.     

Some effects of oral doses of oxytetracycline on growth,survival and disease in Penaeus aztecus

Two size groups of brown shrimp (Penaeus aztecus) were fed a formulated feed containing 0, 100, 1 000 or 5 000 mg of oxytetracycline/kg of feed. Growth and survival were measured after a 3-week drug consumption period. The shrimp were then inoculated with Vibrio alginolyticus, and survival was monitored during the following 24 h.At all three concentrations of oxytetracycline, small shrimp (mean initial wet weight 143.4 mg) consumed approximately one-third the amount of feed consumed by those fed the control diet with no oxytetracycline, yet growth was more rapid with diets containing 100 and 1 000 mg of oxytetracycline/kg of food than with the control diet. Larger shrimp (mean initial wet weight 458.1 mg) receiving oxytetracycline consumed about one-fourth the feed consumed by those on the oxytetracycline-free diet. Some growth inhibition was apparent in these shrimp at all oxytetracycline concentrations. Maximum drug consumption rate, based on actual feed intake, was approximately 1 300 mg oxytetracycline per kg body weight per day for small shrimp, but only 370 mg per kg body weight per day for larger shrimp.All shrimp fed 0, 100 or 1 000 mg of oxytetracycline/kg of feed died within 24 h following inoculation with a standard dose (70% light transmission at 520–540 nm) of Vibrio alginolyticus. All the small shrimp and 70% of the large shrimp fed at the 5 000-mg drug level died, but death generally took place later in the 24-h period than with those fed at the lower drug concentrations. All shrimp fed 5 000 mg oxytetracycline/kg of feed and inoculated with a 1 : 100 dilution of the standard dose of Vibrio alginolyticus survived. All small shrimp and 90% of the large shrimp survived injection of sterile saline.     

Seasonal and nutritional effects on the fatty acids of three species of shrimp, Penaeus setiferus,P. aztecus and P. duorarum

The fatty acids of three species of shrimp from the Gulf of Mexico, white (Penaeus setiferus), brown (P. aztecus), and pink (P. duorarum), were analyzed periodically for 1 year. The fatty acid patterns of varied species of shrimp collected at the same time of the year differed very little from each other. On the other hand, a slight but distinctive seasonal variation of the fatty acid composition, irrespective of Penaeus species, was observed. Saturated fatty acids increased during the warm seasons and decreased during the cold months, while the opposite behavior was exhibited by monoenoic and polyenoic fatty acids. When the variations in fatty acid levels were compared to the temperature of the water, there was a 2-month lag period between a change in water temperature and the corresponding variation in fatty acid composition. This slow alteration of the shrimp fatty acids suggests that the changes are effected through the food chain rather than by endogenous adjustment to an alteration in water temperature.Further studies were performed in which the fatty acid patterns of pond- and laboratory-reared shrimp were compared with those of their food. Evidence was obtained confirming the significant effect of diet on the fatty acids of shrimp lipids. Shrimp incorporated certain dietary fatty acids readily but showed little ability for the conversion of C₁₈ polyunsaturated fatty acids into C₂₀ and C₂₂ fatty acids of higher unsaturation. Thus, the C₂₀ and C₂₂ fatty acids which are essential for shrimp growth cannot be substituted in the diet by C₁₈ precursors.Considered in toto, these experiments suggest that diet exerts a strong influence on the composition of shrimp body lipids and that, contrarily, endogenous synthesis or modification occurs to a low degree.     

An hypothesis on the light requirements for spawning penaeid shrimp,with emphasis on Penaeus setiferus

Using standard equations, we have concluded that the light intensities which have been used by investigators attempting to induce maturation and spawning are up to 4000 times higher than would occur over the spawning grounds of Penaeus setiferus, a species for which successful controlled spawning has yet to be achieved. We recommend that future attempts at captive maturation and spawning with that species be conducted at light levels of no more than 12 μW cm^?2 and that the intensity at which other species of shrimp are matured and spawned be examined relative to natural light levels on their spawning grounds. It is further recommended that the need for light of blue or green color be evaluated for its role as a promotor of maturation and spawning. The intent of these modifications in current spawning procedures is to eliminate the need for eyestalk ablation in captively spawned penaeid shrimp.     

The breeding and growth of Penaeus merguiensis de Man in laboratory recirculation systems

Penaeus merguiensis was cultured through three generations in laboratory recirculation systems. Populations of 24–76 prawns produced, on average, 2–15 batches of 44 000 eggs per month throughout a 16-month period. Survival to metamorphosis was over 50% and post-larvae reached a size (0.15 g live weight) suitable for stocking in “grow-out” tanks 50–60 days after being spawned. In the subsequent 16 weeks prawns reached 5–7 g live weight with 24–58% survival.     

Studies on the presentation of artificial diets for rearing the larvae of Penaeus japonicus Bate

The preparation of microencapsulated diets for rearing the larvae of Penaeus japonicus is described. Once the correct microcapsule size and feeding concentration had been determined, experiments showed that survival rates of 50% to post-larva were possible. Comparative experiments using artificial diets in the form of free particulates indicate that survival rates may be even higher (66–68%) on these diets providing precautions are taken to avoid bacterial blooms. Further investigations revealed that microencapsulated semi-defined diets may be used to determine the nutritional requirements of Penaeus larvae.     

Effects of salinity and photoperiod on the burying behavior of brown shrimp Penaeus aztecus Ives

The burying behavior of Penaeus aztecus was investigated with respect to both short-term and long-term exposures to combinations of four salinities (8.5, 17.0 and 25.5 and 34.0 ‰) and three photoperiods (total darkness, total light or partial light). Exposure either to total dark or total light regimes disturbed the diurnal rhythm and altered the normal body color of the shrimp. However, long-term exposures did not change the salinity-related burying responses. In response to light stimulii, greater numbers of shrimp always buried in lower (8.5 and 17.0‰) than in higher salinities, particularly 34.0‰. On the basis of the parallel relationship between burying responses and growth rates, burying behavior was interpreted as a means of conserving energy, which in turn may promote greater growth in brown shrimp.     

Epizootics of Streptococcus agalactiae infection in captive rays from Queensland,Australia

The aim of this study was to describe two epizootics of high mortalities from infection with Streptococcus agalactiae, occurring in captive rays held in a marine display aquarium in south‐east Queensland, Australia, in 2009 and 2010. Five different species of rays were affected, including mangrove whiprays (Himantura granulata), estuary rays (Dasyatis fluviorum), eastern shovelnose rays (Aptychotrema rostrata), white‐spotted eagle rays (Aetobatus narinari) and blue‐spotted mask rays (Neotrygon kuhlii). This report describes the history of both epizootics including collection, quarantine and husbandry of rays, the disease epizootics, clinico‐pathological features of the disease, antimicrobial therapy, autogenous vaccine production, and laboratory studies including clinical and histopathology, bacteriology, PCR, molecular serotyping and sequencing of the bacterium S. agalactiae.     

Influence of dietary protein and energy on growth,food consumption and food conversion efficiency in Penaeus merguiensis de Man

The requirement of juvenile Penaeus merguiensis for dietary protein and energy was assessed in growth trials performed in indoor recirculation systems using rations based on freeze-dried Mytilus edulis meal. From the results of these experiments evidence was obtained to indicate that the rate of food consumption in this prawn is related to the energy content of the diet. The implications of this are that the protein level required to support maximum growth and optimum protein conversion efficiency are also energy dependent. Optimum protein levels were estimated in the range 34.0–42.0% for diets of energy content 2.9–4.4 kcal/g. A possible scheme relating food consumption, energy production and growth in P. merguiensis is presented.     

Intensive production of juvenile tiger shrimp Penaeus monodon: An evaluation of stocking density and artificial substrates

Tiger shrimp Penaeus monodon were intensively grown from PL₁₅ for 56 d in tank systems at stocking densities of 1000 and 2000 shrimp m^− 3, with and without the addition of artificial substrates (AquaMat® (buoyant and non-buoyant) and polyethylene mesh) at each density. Shrimp growth was significantly greater at the lower density and when substrates were added. Mean shrimp weight at harvest ranged from 0.64 ± 0.06 g (2000 shrimp m^− 3, no added substrate) to 1.17 ± 0.01 g (1000 shrimp m^− 3, added substrate). Survival was high and averaged 79.5 ± 2.7% across all treatments. The addition of substrates significantly increased survival at both stocking densities; however, survival was not significantly affected by stocking density. A maximum harvest density of 1645 shrimp m^− 3 and biomass of 1.27 kg m^− 3 were produced at a stocking density of 2000 m^− 3 with added substrates. Both harvest density and biomass significantly increased with stocking density and addition of substrates. The feed conversion ratio (FCR) of formulated feed was significantly lower when substrates were added. The results show that growth of P. monodon juveniles was inversely related to stocking density during intensive production. However, production output was significantly increased by addition of artificial substrates, which enhanced both growth and survival.     

The effect of Penaeus merguiensis densovirus on Penaeus merguiensis production in Queensland, Australia

Penaeus merguiensis densovirus (PmergDNV) is currently present on several Queensland prawn farms culturing Penaeus merguiensis. Densoviruses have been linked to mortality and stunting that has caused significant financial loss to prawn farms in Asia. A histopathological study for PmergDNV was initially undertaken to compare broodstock to grow out factors from 60 broodstock animals from each of 22 ponds. There was a significant negative correlation (r = -0.61) between the number of animals with PmergDNV lesions and healthy animals. Furthermore, a higher number of septic hepatopancreatic tubules was correlated (r = 0.48) to high PmergDNV loads. Hence, a polymerase chain reaction analysis of 10-day-old post-larvae (PL) was conducted to determine whether PmergDNV infection was resulting in production losses. An attributable risk analysis of PL from 190 ponds over a 2-year period revealed that 28-29% of ponds with below average survival will have at least average survival following the removal of or decreased levels of PmergDNV. P. merguiensis culture facilities in Queensland should have at least a 14.5% increase in production, equating to an increase of $2.25 million within the first year alone, following the removal or reduction of PmergDNV in their ponds. Hence, focussing efforts on prevention, better management practices and maintaining healthy stock should be of top priority.     

The effect of reduced pH on carapace calcium,strontium and magnesium levels in rapidly growing prawns (Penaeus monodon fabricius)

Juvenile prawns (Penaeus monodon) were cultured for 6 weeks at pH 7.9, 7.4 and 6.7. Growth and survival throughout the trial were good, indicating a considerable degree of adaptability. The effects of exposure to low pH included carapace weight loss, increased magnesium content with constant calcium content and slightly decreasing strontium content. The withdrawal of more calcium salts in preference to magnesium (and perhaps organic materials) from the old carapace occurred prior to ecdysis under low pH conditions compared to more normal conditions.