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.     

Effect of ration size and feeding frequency on the growth and food conversion of juvenile Penaeus merguiensis de Man

When juvenile Penaeus merguiensis were fed four times daily they increased in weight more rapidly and utilized their food more efficiently than when fed once per day. The maximum ration for prawns given a commercial dry pellet was approximately 12.0% of the wet body weight per day and changed very little as the prawns grew from 0.5 to 1.3 g in indoor culture. Food conversion efficiency declined with increasing weight and ration size but the relative loss in efficiency was least when rations were maintained near to the maximum. Evidence is presented for the existence of a negative K-line relationship in P. merguiensis.     

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.     

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.     

Observations on the breeding and growth of the giant freshwater prawn Macrobrachium rosenbergii (de Man) in the laboratory

Three male and 20 female prawns, Macrobrachium rosenbergii (de Man), were observed for 390 days. They were maintained in brackish water (5%. salinity) at 28°C which was recycled continuously through a percolating biological filter. Illumination was artificial and did not exceed 10 lm/ft² (approx. 0.1 m²) at the water surface. Mating readily occurred in the experimental tanks (48 × 28 × 25 cm deep). Eggs were incubated for 20 days; the mean number of larvae per brood was 24 000 (range 50–98 100). Over 750 000 larvae were hatched during the experiment. Larger females had proportionately larger broods and larvae from seven broods were cultured to the post-larval stage at intervals throughout the experimental period, which demonstrated their viability.The increase in length of the adults at each moult was constant (arithmetic growth) and did not alter when ova were maturing in the ovary.Prawns achieved larger mean length increments after the environmental conditions were improved. The moulting frequency was very variable and, with one exception, did not change proportionately with length or age of the prawns.Females grew from 115 to 205 mm and males from 145 to 230 mm total length.Three females spawned more than four times in successive intermoult periods, and one produced viable larvae five times in succession.Two of the males sired viable larvae four and seven times respectively during one intermoult period.     

IHHN virus: Infectivity and pathogenicity studies in Penaeus stylirostris and Penaeus vannamei

Infectivity studies of infectious hypodermal and hematopoietic necrosis virus (IHHNV) were conducted on Penaeus stylirostris and P. vannamei (representing species highly susceptible and highly refractory to the disease) via intramuscular injections of the virus. Distinctive histological lesion patterns were observed between species. Six target organ systems were compared interspecifically. The gills and nerve cord/ganglia were shown to undergo significantly higher degrees of tissue damage in infected P. stylirostris compared with infected P. vannamei. Pathogenetic differences correlated well with observed differences in epizootiology between the two species.The infectivity study confirmed that IHHN disease is virus-caused. Cell-free extracts from IHHNV-infected shrimp, when injected into healthy, susceptible shrimp, produced mortalities and Cowdry type A intranuclear eosinophilic inclusion bodies presently considered pathognomonic for the disease.     

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。     

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.     

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.     

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.     

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.     

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.     

Ammonia production and oxidation during the culture of marine prawns and lobsters in laboratory recirculation systems

Data obtained during the culture of tropical prawns Penaeus sp. and European lobsters Homarus gammarus (L.) in 20 laboratory recirculation systems over a number of years were used to obtain gross estimates of (a) the rates and diurnal patterns of ammonia excretion, (b) food utilization and wastage, and (c) nitrification rates in biological filters. Ammonia excretion in Penaeus monodon decreased with increase in animal size from 0·93 to 0·30 mg N g^?1 day^?1 at 1·6 and 27 g live weight, respectively. Large lobsters (300 g) excreted 0·3 mg N g^?1 day^?1. Peak excretion times were approximately 3, 9 and 15 h after a single morning feed for prawns and after 6 and 12 h for lobsters. Uneaten food solids amounted to 11% (lobsters) and 32% (prawns) of the daily ration and, for 4 g animals, only 69% (lobsters) and 45% (prawns) of the food nitrogen in the daily ration was converted into crustacean flesh. Nitrification rates ranged from 0·03 to 0·43 g N oxidized per m² of filter media surface per day. Some evidence for periodicity in nitrifying activity was also found and is discussed in relation to the published literature.     

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.     

Serotonin stimulates ovarian maturation and spawning in the black tiger shrimp Penaeus monodon

Serotonin (5-hydroxytryptamine, 5HT) has been reported to induce ovarian maturation and spawning in the crayfish Procambarus clarkii and white Pacific shrimp Litopenaeus vannamei. The aim of this study was to explore the role of exogenous 5HT on the reproductive performance of the black tiger shrimp Penaeus monodon. 5HT solution was injected into domesticated P. monodon broodstock at 50 μg/g body weight and ovarian maturation and spawning were recorded. The presence of 5HT in the ovary and oviduct of P. monodon was also studied by immunohistochemistry and its levels in the ovary by enzyme link immunoabsorbance assay (ELISA). The 5HT-injected P. monodon developed ovarian maturation and spawning rate at the level comparable to that of unilateral eyestalk-ablated shrimp. Hatching rate and the amount of nauplii produced per spawner were also significantly higher in the 5HT-injected shrimp, compared to the eyestalk-ablated shrimp. 5HT-positive reactions were found in the follicular cells of pre-vitellogenic oocytes, in the cytoplasm of early vitellogenic oocytes and on the cell membrane and cytoplasm of late vitellogenic oocytes. 5HT in the ovary was present at 3.53 ± 0.26 ng/mg protein level in previtellogenic stage and increased to 17.03 ± 0.57 ng/mg protein level in the mature stage of the ovary. The results suggest a significant role of 5HT, possibly directly on the ovary and oviduct, on the reproductive function of female P. monodon.     

长毛对虾海水养殖环境以及虾肠道微生物群落结构研究

为了研究长毛对虾养殖环境以及对虾肠道微生物种群结构的特征,实验分别采集养殖区进水口水体、养殖池底泥、养殖池水体以及长毛对虾肠道样品,采用构建16S rRNA基因克隆文库的方法对不同样品间的微生物群落组成进行了研究。结果表明,4组样品中共获得621条序列,操作分类单元(OTU)总数达212个,表明养殖环境微生物群落结构具有高度的多样性。从遗传进化树分析发现,进水口水体中细菌优势种群为蓝细菌(53.97%)、α-变形杆菌(13.76%)和γ-变形杆菌(10.58%);养殖池水体细菌优势种群为蓝细菌(33.55%)、γ-变形杆菌(14.84%)、厚壁菌(14.19%)、拟杆菌(12.26%)和α-变形杆菌(9.68%);养殖池底泥细菌优势种群大部分属于厚壁细菌(79.12%);对虾肠道细菌优势种群为厚壁细菌(75.79%)、梭杆菌(13.68%)和γ-变形杆菌(10.53%)。在目分类水平上,养殖池底泥、养殖池水体和对虾肠道中芽孢杆菌占有较高的比例,分别占克隆数的69.78%、13.55%和72.63%;进水口水体和养殖池水体中红细菌的比例较高,分别占克隆数的10.05%和9.68%。本研究分析了养殖环境以及对虾肠道微生物的群落结构,揭示微生物从水源到对虾肠道内的演替规律。总体上,本养殖系统微生物群落结构良好,但在养殖池水体和对虾肠道中也检测到黄杆菌类群和少量的弧菌。本研究有助于了解养殖环境对于对虾肠道微生物组成的影响,并为长毛对虾病害的预防提供参考。     

The growth of turbot (Scophthalmus maximus (L.)) in recirculating systems

O-group wild turbot (Scophthalmus maximus (L.)) were used in a number of feeding experiments designed to assess the usefulness of readily available species of industrial fish as feed for the ongrowing stage of cultivation (10–500 g). Sprats (Sprattus sprattus (L.)) and sandeels (Ammodytes marinus Raitt) were the most successful in that feeding rates of 2% live weight per feed gave conversion efficiencies which were generally better than 3:1. A regular regime of two feeds a day should give growth rates approaching 2% per day resulting in an ongrowing period of about 200 days at 16°C. The turbot were maintained in closed recirculating systems using a simple design for the treatment units. These provided a stable environment in which to conduct the experiments the average water quality conditions being given. There were few health problems and the taste and texture of the fish produced appeared to be good.     

Toxic levels of mercury for sequential larval stages of Macrobrachium rosenbergii (de Man)

The toxicity of mercury for sequential stages of Macrobrachium rosenbergii (de Man) larvae was studied under static water conditions at a salinity of 12‰ and temperature of 25.5 – 27.0°C. The results revealed that stage 1 larvae had the lowest threshold lethal concentration (TLC) of mercury, 0.041 ppm Hg, while the post-larvae had a TLC of 0.325 ppm Hg. There was an abrupt increase in the TLC of mercury after the larvae had reached stage 5. The lower TLC prior to stage 5 is most probably due to the more frequent moulting and the relatively thinner cuticle of the 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.