Effect of stocking density on survival and growth performance of pikeperch, <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.), larvae under controlled conditions

The effect of stocking density on the survival and growth of pikeperch, Sander lucioperca (L.), larvae was examined in two consecutive experiments. In experiment I, 4-day-old larvae [body wet weight (BW): 0.5 mg; total body length (TL): 5.6 mm] were reared in 200-l cylindro-conical tanks in a closed, recirculating system (20 ± 0.5°C) at three stocking densities (25, 50 and 100 larvae l⁻¹) and fed a mixed feed (Artemia nauplii and Lansy A2 artificial feed) for 14 consecutive days. At densities of 25 and 100 larvae l⁻¹, growth rate and survival ranged from 2.7 to 1.9 mg day⁻¹ and from 79.2 to 72.3%, and fish biomass gain ranged from 0.6 to 2.0 g l⁻¹, respectively. There were two periods of increased larval mortality: the first was at beginning of exogenous feeding and the second during swim bladder inflation. In experiment II, 18-day-old larvae (BW: 35 mg; TL: 15.6 mm) obtained from experiment I were reared under culture conditions similar to those of experiment I, but at lower stocking densities (6, 10 and 15 larvae l⁻¹). The fish were fed exclusively with artificial feed (trout starter) for 21 consecutive days. At densities of 6 and 15 larvae l⁻¹, the growth rate and fish biomass gain ranged from 28.8 to 23.1 mg day⁻¹ and from 2.0 to 3.3 g l⁻¹, respectively. The highest survival (56.5%) was achieved at a density of 6 larvae l⁻¹. Mortality at all densities was mainly caused by cannibalism II type behaviour (27–35% of total). In both experiments, growth and survival were negatively correlated and fish biomass gain positively correlated with stocking densities. The present study suggests that the initial stocking density of pikeperch larvae reared in a recirculating system can be 100 individuals l⁻¹ for the 4- to 18-day period post-hatch and 15 individuals l⁻¹ for the post-19-day period.     

Acute toxicity of nitrite on tilapia (Oreochromis niloticus) at different external chloride concentrations

Tilapias (Oreochromis niloticus) juveniles (total length 4.9 ± 0.2 cm and weight 1.8 ± 0.2 g) were exposed to several nitrite concentrations (0, 10, 18, 32, 56 and 100 mg l⁻¹) for 96 h, using a semi-static renewal method at chloride levels of 35.0 and 70.0 mg l⁻¹. At the end of the 96-h period, the median lethal concentration (LC₅₀) of nitrite was 28.18 mg l⁻¹ in water with low chloride content (35.0 mg l⁻¹) and 44.67 mg l⁻¹ with high chloride content (70.0 mg l⁻¹, respectively). It indicated that high concentrations of chloride ions could reduce the toxicity of nitrite. During the toxicity experiments, the behaviour and clinical signs of tilapias were also observed. Furthermore, the test of toxic mechanism was designed taking five test concentrations, viz., 5, 10, 15 and 20 mg l⁻¹ and a nitrite-free control. Nitrite exposure produced high levels of methaemoglobin (MHb) but did not seem to cause mortality, as surviving tilapias showed high levels (85.37 ± 2.23 and 53.82 ± 3.44 at 35.0 and 70.0 mg l⁻¹ chloride, respectively). The percentage of MHb exposed to nitrite was significantly higher (P<0.05) than the control (0 mg l⁻¹ nitrite) and increased with the increasing nitrite concentration. However, the percentage of MHb decreased with the increasing chloride concentration.     

Delivery of HUFA, probionts and biomedicine through bioencapsulated Artemia as a means to enhance the growth and survival and reduce the pathogenesity in shrimp Penaeus monodon postlarvae

One of the major problems in the shrimp culture industry is the difficulty in producing high-quality shrimp larvae. In larviculture, quality feeds containing a high content of highly unsaturated fatty acids (HUFA) and ingredients that stimulate stress and disease resistance are essential to produce healthy shrimp larvae. In the present study, Penaeus monodon postlarvae (PL15) were fed for 25 days on an unenriched Artemia diet (control; A) or on a diet of Artemia enriched with either HUFA-rich liver oil of the trash fish Odonus niger (B), probionts [Lactobacillus acidophilus (C1) or yeast-Saccharomyces cerevisiae (C2)] or biomedicinal herbal products (D) that have anti-stress, growth-promoting and anti-microbial characteristics. P. monodon postlarvae fed unenriched Artemia exhibited the lowest weight gain (227.9 ± 8.30 mg) and specific growth rate (9.95 ± 0.05%), while those fed the HUFA-enriched Artemia (B) exhibited the highest weight gain and specific growth rate (362.34 ± 12.56 mg and 11.77 ± 0.08%, respectively). At the end of the 25-day rearing experiment, the shrimp postlarvae (PL40) were subjected to a salinity stress study. At both low and high (0 and 50‰) salinities, the group fed the control diet (A) experienced the highest cumulative mortality indices (CMI) 935.7 ± 2.1 and 1270.7 ± 3.1, respectively. Those fed diet D showed the lowest stress-induced mortality, and CMI were reduced by 31.1 and 32.3% under conditions of low and high salinity stress, respectively. A 10-day disease challenge test was conducted with the P. monodon postlarvae (PL40–PL50) by inoculating the shrimp with the pathogen Vibrio harveyi at the rate of 10⁵–10⁷ CFU/ml in all rearing tanks. P. monodon postlarvae fed probiont-encapsulated Artemia diets (C1 and C2) exhibited the highest survival (94.3 and 82.3%, respectively) and lowest pathogen load (V. harveyi) in hepatopancreas (5.2 × 10² ± 9.0 × 10 and 4.6 × 10² ± 9.0 × 10 CFU g⁻¹, respectively) and muscle (2.0 × 10² ± 6 × 10 and 1.7 × 10² ± 8.6 × 10 CFU g⁻¹, respectively) tissues. The shrimp that were fed the unenriched Artemia (Control; A) showed the lowest survival (26.33%) and highest bacterial load in the hepatopancreas (1.0 × 10⁵ ± 5 × 10³ CFU g⁻¹) and muscle (3.6 × 10⁴ ± 6 × 10² CFU g⁻¹). The shrimp fed the herbal product (D)-enriched Artemia also exhibited enhanced survival and reduced V. harveyi load in the tissues tested compared to the control diet (A) group. The results are discussed in terms of developing a quality larval feed to produce healthy shrimp larvae.     

Tolerance of striped trumpeter Latris lineata embryos to ozonated seawater

The tolerance of striped trumpeter, Latris lineata (Bloch and Schneider 1801) embryos to ozonated seawater was examined as a possible means of disinfection. The effect of a range of ozone doses and exposures (CT = concentration × exposure time) was tested at different stages of embryonic development. Three-day-old embryos two-thirds developed around the yolk were exposed for 0.5, 1 or 5 min to ozone concentrations of 0.5, 1, 2 and 5 mg O₃ l⁻¹ in a fully orthogonal factorial design. For each treatment there were four replicate 250 ml containers that each received 100 ± 15 embryos. There was no significant difference in hatching success between control-treated embryos or embryos ozonated at 0.5 or 1 mg O₃ l⁻¹ for 0.5, 1 or 5 min (P < 0.05). However, hatching success was significantly reduced when embryos were treated with 2 or 5 mg O₃ l⁻¹ for 5 min or 5 mg l⁻¹ O₃ for 1 min (P < 0.05). The tolerance of embryos to 0, 0.5 or 2 mg O₃ l⁻¹ for 1 min at different stages of development (Day 0, 1, 2, 3 or 4), was then examined. An ozone concentration of 0.5 mg l⁻¹ had no effect on hatching success at any stage of development, but a concentration of 2 mg l⁻¹ significantly reduced hatching success on all days except Day 3. A safe and tested hatchery practise is to disinfect striped trumpeter embryos with 1 mg O₃ l⁻¹ for 1 min on Day 3 post-fertilisation when the embryo is two-thirds developed around the yolk.     

The impact of net-isolated polyculture of tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) on plankton community in saline–alkaline pond of shrimp (<Emphasis Type="Italic">Penaeus vannamei</Emphasis>)

We used 12 land-based experimental enclosures (6 m × 5 m) in a saline–alkaline pond of shrimp (Penaeus vannamei) to determine the impact of net-isolated polyculture of tilapia (Oreochromis niloticus) on plankton communities for 40 days. Tilapias were stocked in net cages suspended in enclosures, in polyculture ponds including tilapia and shrimp. Four tilapia biomass were tested: 0, 39, 115 and 227 g m⁻². Shrimp stocking biomass were 0.7 g m⁻² in all treatments. There were three replicates in each treatment. Our results showed that the presence of tilapia significantly reduced phytoplankton biomass directly through predation and indirectly through top-down effect. The stocking of tilapia reduced zooplankton biomass, particularly rotifer biomass. However, copepod biomass was not been significantly affected. So, net-isolated polyculture of tilapia can thus have a strong impact on phytoplankton allowing the co-existence of large numbers of copepods with planktivorous fish and improving the water quality of shrimp ponds.     

Effects of dimethoate and beta-naphthoflavone on selected biomarkers of Poecilia reticulata

The main objective of the present study was to investigate if a battery of enzymatic biomarkers was suitable for use as effect criteria in acute toxicity tests with Poecilia reticulata. To attain this objective, the in vivo effects of dimethoate and beta-naphthoflavone on acetylcholinesterase (AChE), cytochrome P4501A-dependent monooxygenase activity of 7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferases (GST), lactate dehydrogenase (LDH) and Na⁺-K⁺-ATPase activities of P. reticulata were studied. After 96 h of exposure to sublethal concentrations (0.063 mg l⁻¹ to 1 mg l⁻¹) of the pesticide, an inhibition of the enzymes AChE and GST, as well as an induction of LDH was observed. The compound beta-naphthoflavone significantly induced both EROD and GST. The remaining enzymes analysed were not significantly altered by the exposure to beta-naphthoflavone (0.82 mg l⁻¹ to 1.7 mg l⁻¹). These results suggest that in vivo toxicity tests based on the biomarkers used in this study are sensitive and present advantages to conventional acute tests based on mortality, since they were able to detect sublethal effects in a short-period of time (96 h) indicating target and/or detoxification mechanisms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Shrimp shell as a potential sorbent for removal of arsenic from aqueous solution

This study examined the ability of shrimp shell to remove arsenic (As) from aqueous solutions. The shells of two species of shrimp, black tiger shrimp Penaeus monodon and white shrimp Litopenaeus vannamei, were chosen to be the sorbents. Laboratory exposure experiments estimated uptake and depuration rate constants (i.e., k ₁ and k ₂) as well as the bioconcentration factors (BCF) of the shells of the two shrimps. A first-order one-compartment model was presented to describe the uptake kinetics of As in shrimp shell. The resulting k ₁, k ₂, and BCF values of black tiger shrimp were 0.034–1.722 ml/g/day, 0.007–0.345 g/g/day, and 5.08 ± 1.56 ml/g, while those for white shrimp were 0.053–0.523 ml/g/day, 0.011–0.237 g/g/day, and 3.95 ± 1.88 ml/g, respectively. The sorption capacities of black tiger shrimp shell and white shrimp shell were 1.08 × 10⁻⁴–6.66 × 10⁻³ and 1.04 × 10⁻⁴–3.26 × 10⁻³ mmol/g, respectively. The sorption capacity of shrimp shell increased with the initial As concentration in water. Shrimp shell, as a waste material, could be potentially used for the removal of As from an aqueous medium. Although the As-removal capacity of shrimp shell was lower than those of natural and chemical sorbents, using shrimp shells as sorbents is less expensive and could increase the additional value of shrimp products.     

The effect of feeding on oxygen consumption and ammonia excretion of juvenile tench Tinca tinca (L.) reared in a water recirculating system

The effect of feeding frequency (one, three, and continuous feeding), feed ration (0.2, 0.5, 0.8% of total fish biomass), and feeding per se on the oxygen consumption (OC, mg O₂ kg⁻¹ h⁻¹) and ammonia excretion (AE, mg TAN kg⁻¹ h⁻¹) of juvenile tench (body weight 15–19 g) and variations in these parameters in daily cycles were examined. Fish metabolism was studied in a recirculating system (rearing tanks of 0.2 m³, water temperature 23 °C). It was found that oxygen consumption and ammonia excretion depended significantly on feed ration. An increase of feed ration from 0.2 to 0.8% of fish biomass caused an increase of OC and AE from 126.80 mg O₂ kg⁻¹ h⁻¹ and 1.95 mg TAN kg⁻¹ h⁻¹ to 187.35 mg O₂ kg⁻¹ h⁻¹ and 8.80 mg TAN kg⁻¹ h⁻¹ (p<0.05). There was no dependence between feeding frequency and the mean rate of oxygen consumption. However, the relationship between feeding frequency and ammonia excretion by juvenile tench was statistically significant (p<0.05). Feeding frequency significantly affected daily fluctuations of AE and OC. It was found that diurnal variations in metabolic rates were strictly related to tench feeding, and the daily variations of AE were significantly higher than OC.     

Bioaugmentation in the growth and water quality of livebearing ornamental fishes

Bacillus subtilis isolated from the intestine of Cirrhinus mrigala (Hamilton) was incorporated into the rearing water of Poecilia reticulata (Peters), Poecilia sphenops (Valenciennes), Xiphophorus helleri (Heckel) and Xiphophorus maculatus (Gunther) at four different concentrations (5 × 10⁸ cells ml⁻¹, 5 × 10⁷ cells ml⁻¹, 5 × 10⁶ cells ml⁻¹ and 5 × 10⁵ cells ml⁻¹) and its effect on fish growth performance and survival, water quality parameters and bacterial population of water were assessed. The results showed that the addition of bacterial cells in the rearing water resulted in greater survival and a faster growth rate and, hence, greater length and weight increments of the livebearers. The use of a bioaugmentor in the rearing water of the livebearing fishes resulted in significantly lower (P < 0.05) concentrations of dissolved organic matter and total ammonium nitrogen. The counts of motile aeromonads and total coliforms recorded in the water of bioaugmented tanks were also lower than that in the control tank. Bioaugmentation between 10⁶ and 10⁸ cells ml⁻¹ in the rearing water is sufficient in establishing a bioaugmentor and the use of a higher concentration of bacterial cells did not always lead to significantly better results.     

Enhancement of <Emphasis Type="Italic">Penaeus monodon</Emphasis> shrimp postlarvae growth and survival without water exchange using marine <Emphasis Type="Italic">Bacillus pumilus</Emphasis> and periphytic microalgae

We have investigated the possibility of using a consortium of marine bacterium and periphytic microalgae to improve the water quality and increase the growth and survival of the shrimp Penaeus monodon in a hatchery system. Three treatments were evaluated for their effect on P. monodon postlarvae (PL) when the culture water was not changed: Bacillus pumilus alone (B); periphytic microalgae alone (M); B. pumilus + periphytic microalgae (BM). P. monodon PL raised in a tank of unchanged water without bacterium and periphytic microalgae served as the control. The water in tanks of the M and BM treatments had significantly low levels of total ammonia-nitrogen (TAN) (0.03 and 0.01 mg l⁻¹, respectively) and nitrite-nitrogen (NO₂-N) (0.03, 0.01 mg l⁻¹, respectively) than that in the B (TAN 0.80, NO₂-N 0.68 mg l⁻¹) and control (TAN 1.11, NO₂-N 1.12 mg l⁻¹) tanks. Moreover, PL cultured in tanks M and BM had significantly higher survival and specific growth rates and a significantly higher resistance to the reverse salinity stress test than those in the B and control tanks. Compared to the control PL, the PL cultured in the BM tanks had significantly higher levels of protein, lipid, polyunsaturated fatty acids, ecosapentaenoic acid, and docosahexaenoic acid. The culture water in tanks BM also contained significantly less Vibrio than the control water. Our results illustrate the beneficial effects of a B. pumilus and periphytic microalgae consortium on improving the water quality and the growth and survival of shrimp PL grown in a hatchery system.     

Effects of conventional versus organic production systems on amino acid profiles and heavy metal concentrations in the Chinese shrimp <Emphasis Type="Italic">Penaeus chinensis</Emphasis>

Amino acid composition and heavy metal concentration were examined in organic and conventional Chinese shrimp Penaeus chinensis production systems during the production cycle. The crude protein and total amino acid contents for organic shrimp samples were 0.932 and 0.945 mg/g d.w., while they were 0.849 and 0.826 mg/g d.w., respectively, for conventionally produced samples. The ratios of essential amino acids to nonessential amino acids in organic and conventional cultured shrimp were 0.58 and 0.63, respectively. Shrimp samples from the conventional system were significantly richer in Cu (2.28 vs. 1.53 mg kg⁻¹), Pb (0.13 vs. 0.08 mg kg⁻¹), Cd (0.09 vs. 0.04 mg kg⁻¹), and Zn (9.94 vs. 8.42 mg kg⁻¹) when compared with those obtained from the organic system. It is concluded that organic shrimp production systems can produce comparable growth and nutritional quality benefits.     

Tench (<Emphasis Type="Italic">Tinca tinca</Emphasis> L.) larvae rearing under controlled conditions: density and basic supply of <Emphasis Type="Italic">Artemia</Emphasis> nauplii as the sole food

After artificial reproduction of tench, larvae must be maintained indoors, and studies on rearing conditions are needed, focussing on the reduction of labour and costs. Three experiments on larvae (5th day post-hatch) were conducted for 25 days using Artemia nauplii as the sole food in order to determine basic feeding and density conditions during the first rearing period. Tench were maintained in 25 l fibreglass tanks, supplied with an artesian water flow throughout of 0.2 l min⁻¹. Water temperature was 22.5 ± 1°C, and the photoperiod was natural. Larvae fed on a restricted amount of nauplii reached high survival rates, even with the minimum of 50 nauplii larva⁻¹ day⁻¹. This amount of food may be sufficient at least for the first 25 days of exogenous feeding if fast growth is not the priority, and high densities can be maintained with good survival rates (over 90% up to 160 larvae l⁻¹ and 77% with 320 larvae l⁻¹). When food was supplied in excess once a day, high survival rates were achieved (91–97%), without differences among the densities tested. Animals at a density of 100 l⁻¹ reached the highest length (15.57 mm) and individual weight (46.8 mg). This growth is greater than those reported in studies feeding several times a day. It could be deduced that, while live food remains available for tench, it is not necessary to feed so frequently. Considering the relationship among the initial number of animals, final survival and growth and ration supplied, the new data reported here are useful to establish suitable stocking densities under both culture and experimental conditions.     

Evaluation of a 40 day Assay for Testing Endocrine Disrupters: Effects of an Anti-Estrogen and an Aromatase Inhibitor on Sex Ratio and Vitellogenin Concentrations in Juvenile Zebrafish (Danio rerio)

In the present study, the effects of the anti-estrogen ZM 189,156 and the aromatase inhibitor fadrozole were evaluated in a 40-day juvenile assay developed for screening of endocrine disrupting chemicals. Juvenile zebrafish were exposed from 20 to 60 days post hatch (dph) to ZM 189, 154 (100 μg l⁻¹ and 200 μg l⁻¹) and fadrozole (10, 32, and 100 μg l⁻¹). VTG concentrations were measured at 38 dph by the use of a direct non-competitive sandwich ELISA and sex ratios were determined at 60 dph by histological examination of the gonads. A small but significant increase in VTG concentrations was observed in fish exposed to ZM 189, 156 (100 and 200 μg l⁻¹) and fadrozole (10 and 100 μg l⁻¹) compared to control groups. In fish exposed to ZM 189, 156 and fadrozole, the percentage of females declined and the number of undifferentiated fish increased. These findings show that exposure of juvenile zebrafish to an aromatase inhibitor or an anti-estrogen during early development inhibits differentiation and development of female gonads. The data presented, furthermore, show that the 40-day juvenile assay may be suitable for screening endocrine disrupting chemicals acting as anti-estrogens and aromatase inhibitors.     

Enrichment of Artemia nauplii with the probiotic yeast Saccharomyces boulardii and its resistance against a pathogenic Vibrio

Enrichment of Artemia nauplii with a known probiotic yeast Saccharomyces boulardii (SB) and its role in enhancing resistance against the pathogen Vibrio harveyi was investigated. SB was cultured, then fed to instar II Artemia nauplii in three different treatments; 10² (T1), 10³ (T2) and 10⁴ (T3) colony forming units (CFU) per ml in triplicate. The algae Nanochloropsis sp. was used as control diet. Survival and total count of CFU nauplii⁻¹ was observed on different media (Sabouraud, for enumerating yeasts, thiosulphate citrate bile salts sucrose, for enumerating Vibrio and seawater agar, for enumerating total aerobic flora) for each replication. Enhanced survival of nauplii was observed in treatments as compared to control. Results indicated that enrichment of SB in Artemia nauplii proceeded in a linear fashion, and up to 3500 CFU of SB could be detected in one nauplii at 10⁴ CFU ml⁻¹ treatment. No conclusive trend could be observed in the count of Vibrio and total aerobic flora due to treatment. Enriched nauplii were then challenged with the pathogen V. harveyi for 24 and 48 h at a concentration of 6.1 × 10⁶ CFU ml⁻¹. The survival counts at 48 h showed that the resistance of the nauplii was significantly (P < 0.01) improved in those fed with 10⁴ CFU  ml⁻¹ SB (90% survival rate after 48 h of challenge versus less than 40% for the infected control group without SB and treatments T1 and T2). This study shows that SB, which has been used for the first time in an aquatic live feed organism, has a profound beneficial effect on the nauplii by increasing its resistance to a pathogenic Vibrio infection. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relationship between concentrations of odorous compounds and biomass of phytoplankton and actinomycetes in freshwater ponds of Beijing,China

The odorous compounds including geosmin and 2-methylisoborneol (MIB) were detected in intensively cultivated freshwater ponds in Beijing, China, by coupling head space solid-phase microextraction with gas chromatography mass spectrometry (GC-MS). Moreover, the biomass of phytoplankton and actinomycetes in the fishponds were determined simultaneously, and the relationship between the concentrations of these odorous compounds and the biomass of phytoplankton and actinomycetes was assessed. The results showed that among the odorous compounds detected, geosmin was the main one, and concentrations of 1.22–35.58 ng l⁻¹ were found in all fishponds. Besides, MIB with 1.39–6.00 ng l⁻¹ was found in parts of fishponds. Six phyla and 22 genera of algae were observed in the fishponds with a biomass of 17.33–178.34 mg l⁻¹, among which dominant phyla were Bacillariophyta and Euglenophyta. Four genera of actinomycetes with a gross biomass of 0–76 × 10⁴ ind l⁻¹ were found in the fishponds, of which Streptomyces spp. was the dominant genera. This indicated that geosmin concentration in fishponds was related with the total biomass of the dominant algae. The results showed that Melosira spp. and Cyclotella spp. were the main microalgae to cause off-flavor in Beijing’s intensively cultivated freshwater ponds in summer and autumn, while Euglenophyta and other algaes played a small role in causing off-flavor.     

Growth and performance of the whiteleg shrimp Penaeus vannamei (Boone) cultured in low‐salinity water with different stocking densities and acclimation times

We evaluated the performance of whiteleg shrimp Penaeus vannamei (Boone, 1931) in response to different stocking densities and acclimation periods. Shrimp postlarvae were acclimated from seawater (30 g L^?1) to low‐salinity well water (<1.0 g L^?1) at a constant hourly reduction rate of 40, 60, 80 and 100 h. After acclimation to low‐salinity well water, postlarvae from each acclimation time treatment were stocked in three replicate tanks at densities of 50, 100, 150 or 200 shrimps m^?2 for 12 weeks of growth. Salinity averaged <1.0 g L^?1 for each growth study. The different treatments resulted in significant differences in both the final body weight and the survival rate (SR). Shrimp acclimated for 100 h showed substantially improved survival (83%) relative to shrimp acclimated for shorter periods. Shrimp yields for all cultured periods ranged from 0.32 kg m^?2 in tanks stocked at 50 m^?2 to 1.14 kg m^?2 in tanks stocked at 200 m^?2. We conclude that whiteleg shrimp can be successfully grown in low‐salinity well water, and that the growth, production output and SRs are significantly higher when shrimp are acclimated for longer periods.     

Toxicity of Diazinon 60 EC for Cyprinus carpio and Poecilia reticulata

Diazinon 60 EC (chemical insecticide, organophosphate, active substance diazinon at a concentration of 600 g l⁻¹) is used in fish-farming in well-founded cases as a biocide to suppress excessive propagation of coarse Daphnia zooplankton. At the concentration of 10 μg l⁻¹ (i.e., 100 g per 1 ha at a mean depth of the pond of 1 m), Diazinon 60 EC can highly selectively eliminate Daphnia zooplankton, causes no harm to fish, and relatively quickly decomposes in the aquatic environment. This has been corroborated by results of acute toxicity tests in fish: the 96 h LC50 is 3 mg l⁻¹ for the guppy (Poecilia reticulata) and 10–25 mg l⁻¹ for the common carp (Cyprinus carpio). As demonstrated by embryonic and larval tests of toxicity for the common carp (C. carpio), Diazinon 60 EC at the concentration of 10 μg l⁻¹ causes no harm to the tested, individuals even in these sensitive (critical) stages of ontogeny.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

Use of soy protein concentrate in practical diets for Pacific white shrimp (Litopenaeus vannamei) reared under field conditions

The objective of this study was to evaluate the production response of Litopenaeus vannamei fed with production diets containing increasing percentages (0, 4, 8, and 12%) of soy protein concentrate (SPC). The diets were commercially produced and evaluated in outdoor tanks and 0.1-ha production ponds. In the outdoor green water tank system, the four test diets and a commercial reference diets were offered to juvenile shrimp (1.0 g initial weight) reared over a 10-week period at a stocking density of 30 shrimp per tank. At the conclusion of the tank trial, there were differences in final weight (13.5–15.0) biomass (399 g–432 g), and FCR (1.17–1.28) with the reference diet generally producing significantly better results than the test diets albeit there were no significant differences among the SPC test diets. In addition, the test diets were evaluated in 0.1-ha ponds using four replicates per diet. Nursed juvenile shrimps (0.013 g initial weight) were stocked at 35 shrimp m⁻² and were cultured under standardized pond production conditions for 18 weeks. At the conclusions, net yield (4,190–5,051 kg/ha), final mean weight (13.5–15.7 g), survival (86.7–93.3%), and FCR (1.3–1.59) were evaluated with no significant differences between dietary treatments. The results from this study demonstrated that SPC inclusion up to 12% SPC in soybean-based diet can be used in commercial feed formulations for L. vannamei without causing negative effect on growth, feed conversion, survival and net yield.