Oxygen consumption and ingestion rate of Penaeus setiferus larvae fed Chaetoceros ceratosporum, Tetraselmis chuii and Artemia nauplii

The effects of the density and type of food on oxygen consumption and ingestion rate of larvae of the white shrimp Penaeus setiferus fed diatoms Chaetoceros ceratosporum, flagellates Tetraselmis chuii and Artemia franciscana nauplii were analysed. Diatoms, flagellates and Artemia nauplii were fed at five densities from 10 to 5 × 10³ cells mL^?1, 0 to 4 × 10³ cells mL^?1, and 0.1, 0.5, 1.0, 1.5 and 2 nauplii mL^?1, respectively. In three experiments, two of three types of food were maintained constant at concentrations of 30-40 × 10³ cells mL^?1 (diatoms), 2 × 10³ cells mL^?1 (flagellates) and 1 Artemia nauplii mL^?1. The oxygen consumption in three experiments increased with larval stage, reaching maximum values in Mill except at lower feed concentrations. A maximum ingestion peak in MI was recorded in larvae fed diatoms, whereas that peak was observed in Mil in larvae fed flagellates. The maximum ingestion rate of Artemia nauplii was observed in Mill. Feed concentrations that produced an optimum metabolic rate as a consequence of equilibrium between ingested food and larval stages were obtained with 20 and 30 × 10³ cells mL^?1 of C. ceratosporum, 2 and 3 × 10³ cells mL^?1 of T. chuii, and 1.0 Artemia nauplii mL^?1. These concentrations would be the most suitable for producing P. setiferus postlarvae.     

Inhibitory effects of Bacillus licheniformis (DAB1) and Pseudomonas aeruginosa (DAP1) against Vibrio parahaemolyticus isolated from Fenneropenaeus indicus

In aquaculture industries, there is an urgent need to develop microbial control strategies, to control disease outbreaks. In recent years, probiotics are considered as a valid alternative for the use of antibiotics in aquaculture to prevent high mortality and promote growth. In the present study, seven strains of bacteria such as Bacillus licheniformis (DAB1), Bacillus pumilus (DAB2), Bacillus sp. (DAB3), Pseudomonas aeruginosa (DAP1), Pseudomonas sp. (DAP2), Pseudomonas aeruginosa (DAP3), Pseudomonas aeruginosa (DAP4), and three pathogenic Vibrio parahaemolyticus (DAV1, DAV2, DAV3) were isolated from healthy and diseased Fenneropenaeus indicus collected from the east coast of Tamilnadu, India. The strains were identified by biochemical analysis and 16S rRNA sequence methods. Among the seven probiotic strains tested, the cell-free extract from DAB1 and DAP1 exhibited higher inhibitory activity of V. parahaemolyticus than other isolates under in vitro conditions. The LC₅₀ of DAV1, DAV2, and DAV3 was found to be ～10³ CFU mL^?1. Pathogenicity of three V. parahaemolyticus DAV1, DAV2, and DAV3 showed significant mortalities (40 %) in Artemia nauplii at inoculation densities of 10³ CFU mL^?1 when compared to the controls (unchallenged nauplii). A significant reduction in mortality (P < 0.001) was found by addition of 10⁶ CFU mL^?1 of DAB1 and DAP1 strains in nauplii against the pathogens. In conclusion, the present study result reveals that DAB1 and DAP1 have potential applications for controlling pathogenic V. parahaemolyticus in Artemia culture systems and aquaculture practices.     

Effects of dietary administration of two Patagonian probiotics on the zoeae I from the swimming crab Ovalipes trimaculatus

In this study, we analyzed the effects of supplying two alternative Patagonian-autochthonous probiotic strains of Bacillus sp. and Lactococcus sp. or no probiotic at all (control treatment) on the survival, stage duration, molting success to the next larval instar, and speed of vertical displacement of the zoeae I of the southern surf crab Ovalipes trimaculatus, also considering two alternative methods for their administration: (i) direct inoculation into the rearing seawater or (ii) bio-encapsulation in Artemia persimilis nauplii. Both probiotic strains were effectively bio-encapsulated by the nauplii at high CFU x naupli^?1. Probiotic inoculation in the rearing seawater improved the performance of the zoeae over the control treatment and also outperformed bio-encapsulation. Bio-encapsulation in Artemia nauplii resulted in lower survival and molting success to zoeae II compared to the control treatment. No significant differences were observed between the mean effects of either one of the two probiotics. Overall, our results show that the direct inoculation of any of both probiotics into rearing seawater improves the larval culture of the portunid crab.

     

Effect of feeding Lactobacillus-based probiotics on the gut microflora, growth and survival of postlarvae of Macrobrachium rosenbergii (de Man)

The present study was conducted to study probiotics treatment in the post‐larval diet of Macrobrachium rosenbergii. Three hundred postlarvae (average weight, 114–118 mg±0.11) were divided in five experimental groups each with four replicates. The experiment was conducted for 60 days. Experimental diets were identical in all the aspects except for variation in the probiotics strain. T1 and T2 groups were fed Lactobacillus acidophilus (140×10¹¹ CFU 100 g^?1) and L. sporogenes (24×10⁷ CFU 100 g^?1) respectively. The T3 group was fed L. sporogenes bioencapsulated in Artemia nauplii. T4 was the control group (without probiotic) whereas T5 was fed Artemia along with control diet. The bacteriological study indicated that the gut microflora of postlarvae are devoid of lactic acid bacteria. The probiotic strains were found to have inhibitory effects against the gram‐negative bacterial flora present in the gut. Growth of the probiotic fed groups was significantly higher (P<0.05) than the control group. Significantly higher growth (P<0.05), per cent weight gain (132.5%), specific growth rate (1.41%), feed efficiency ratio (FER) (0.45), protein efficiency ratio (1.29) and protein gain (161.6%) were recorded in T3 group fed Artemia bioencapsulated L. sporogenes over the control group (P<0.05). Although insignificant (P>0.05), growth‐promoting effects of L. sporogenes were found to be higher than L. acidophillus. Survival of the postlarvae was not affected by probiotics in the diet.     

Effect of Customized Probiotics on the Physiological and Immunological Responses of Juvenile Western King Prawns (Penaeus latisulcatus Kishinouye, 1896) Challenged with Vibrio harveyi

Juvenile western king prawn P. latisulcatus were fed 10⁵ colony-forming units (CFU)/mL of two probiotics Pseudomonas synxantha and P. aeruginosa for 28 days. P. latisulcatus were then challenged with V. harveyi at 0 (control), 10³, 10⁵, and 10⁷ CFU/mL. During the seven days of challenge, disease resistance of the probiotic-fed prawns was compared with that of prawns not fed probiotics. The immunological responses of the prawns did not improve during the challenge period in terms of total haemocyte count, hyalinocyte, semi-ganulocyte, granulocyte, clotting time, bacteraemia, and intestinal bacterial load. Overall, when prawns were challenged with V. harveyi, the LT₅₀ values got shorter as V. harveyi concentration increased. LT₅₀ values of prawns fed probiotics were significantly longer (P < 0.05) than those not fed probiotics. At a V. harveyi concentration of 10³ CFU/mL, the 100% survival of the prawns fed probiotics was three times more likely than those of the prawns not fed probiotics.     

Replacement of live food with a microbound diet in feeding Litopenaeus setiferus (Burkenroad) larvae

Microbound feeds have been well accepted by shrimps and farmers in many penaeid shrimp hatcheries. The present study focused on an adequate level of replacement of Artemia nauplii and microalgae by a microbound diet for rearing Litopenaeus setiferus (Burkenroad) larvae. A microbound diet (MBD) consisting of fishmeal, squid meal, shrimp meal, yeast meal and soybean meal was used. The first experiment was designed to obtain the optimum level of MBD to complete the live feeding schedule, from Protozoea (PZ_III) to Mysis (M_III). The experimental levels of the microbound diet tested were 2, 4, 6 and 8 mg MBD L^?1 day^?1. The next step was to determine the Artemia nauplii replacement level from PZ_I to M_III by MBD. These experiments were carried out either in the presence (Experiment 2) or in the absence of algae (Experiment 3). Four replacement levels were tested: 0% (4 mg MBD L^?1 day^?1: 1 Artemia nauplii mL^?1), 40% (5.5 mg MBD L^?1 day^?1: 0.6 Artemia nauplii), 60% (6.5 mg MBD L^?1 day^?1: 0.4 Artemia nauplii) and 100% (8 mg MBD L^?1 day^?1: 0 Artemia nauplii). In all experiments growth, survival, development, quality index (QI) and performance index (PI), were used to determine the optimum concentration of microbound diet. Results showed that 6 mg MBD L^?1 day^?1 can be recommended as a complement to live food for L. setiferus larvae from PZ_III to M_III. In the presence of algae, maximum growth and survival may be obtained in 40–60% (5.5–6.5 mg MBD L^?1 day^?1) of Artemia nauplii replacement levels. In the absence of algae, the Artemia nauplii replacement resulted in slower development, less salinity resistance, lower growth and lower survival than was obtained in larvae fed with algae.     

The larval rearing of the marine ornamental crab, Mithraculus forceps (A. Milne Edwards, 1875) (Decapoda: Brachyura: Majidae)

The goal of this study is to develop a larviculture protocol for Mithraculus forceps, a popular marine aquarium species. Different temperatures (25±0.5°C and 28±0.5°C), stocking densities (10, 20, 40 and 80 larvae L^?1), prey densities (newly hatched Artemia of 1, 4, 7 and 12 nauplii mL^?1) and metamorphosis to crab conditions (Systems A and B) were tested. The best survivorship and faster development were obtained when the larvae were reared at a density of 40 larvae L^?1 for 7 days post hatching (DPH) in System A, at 28°C and fed with 7 mL^?1 of newly hatched Artemia nauplii. After 7 DPH all the megalopa were moved to System B and the same temperature and prey density were maintained. At the end of the experiment, 12 DPH, survivorship of 74.1±4.8% was obtained.     

Use of the microalga Nannochloropsis occulata in the rearing of newborn longsnout seahorse Hippocampus reidi (Syngnathidae) juveniles

The aim of this study was to evaluate the effect of microalgae on the rearing of newborn juveniles of the longsnout seahorse, Hippocampus reidi. Two treatments in three replicates were tested over a 15‐day period: with and without the addition of the microalgae Nannochloropsis oculata at a concentration of 2.02 ± 0.44 × 10⁶ cells mL^?1. At each replicate, beginning on the second day of life, 120 H. reidi juveniles (stocking density of 3 ind L^?1) were fed the offspring of the benthic copepod Tisbe biminiensis (100 copepod cm^?2) together with newly hatched Artemia nauplii (3.8 mL^?1). From the sixth day of life, enriched Artemia metanauplii replaced newly hatched Artemia nauplii. After 15 days, the H. reidi individuals were counted, measured and weighed. Mean survival was significantly greater in the microalgae treatment (76.42 ± 5.07%) than in the treatment with no microalgae (25.44 ± 6.91%). Moreover, total length, height and dry weight were significantly larger in the microalgae treatment. Thus, the addition of microalgae increases the growth and survival of H. reidi juveniles fed T. biminiensis and Artemia. The higher growth and survival of H. reidi juveniles was not related to the larger ingestion rates but probably to the nutritional improvement of the live feeds or to the probiotic effect. The protocol developed for rearing H. reidi juveniles resulted in a high survival, and represents an advance in the farming of this species.     

Food consumption and selectivity by larval yellowtail kingfish Seriola lalandi cultured at different live feed densities

Live food supply is a key factor contributing to the success of larval fish rearing. However, live food densities vary greatly between fish species and management protocols across fish hatcheries. The growth, survival, food selection and consumption of yellowtail kingfish larvae were examined at different regimes of live food supply in an attempt to identify a suitable live food feeding protocol for larval rearing in marine fish. This study was divided into two feeding phases: rotifer phase from 3 to 14 DPH (phase I) and Artemia nauplii phase from 15 to 22 DPH (phase II). In phase I, four rotifer densities (1, 10, 20 and 40 mL⁻¹) were used. In phase II, Artemia started at 0.8 nauplii mL⁻¹ on 15 DPH, and then the density of Artemia was daily incremented by 50%, 70%, 90% and 110%, respectively, in four treatments from 15 to 22 DPH. In phase I, rotifer density significantly affected larval growth, but not survival. By 7 DPH, the number of rotifers consumed by fish larvae reached 170–260 individuals, but did not significantly differ between rotifer densities. During cofeeding, fish larvae selected against Artemia nauplii by 10 DPH, but by 14 DPH Artemia nauplii became the preferred prey item by fish larvae exposed to the 10, 20 and 40 rotifers mL⁻¹. In phase II, both fish growth and survival were affected by Artemia densities. Fish daily consumption on Artemia by 20 DPH reached 500–600 individuals but did not significantly differ between prey densities. The result suggests that rotifer densities be offered at 20–40 mL⁻¹ before 6 DPH and 10–20 mL⁻¹ afterwards to support larval fish growth and survival. Likewise, Artemia is recommended at a daily increment of 90–110% of 0.8 mL⁻¹ from 15 to 22 DPH. This study proposes a management protocol to use appropriate type and quantity of live food to feed yellowtail kingfish larvae, which could be applicable to larval culture of other similar marine fish species.     

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.     

Daily food intakes and optimal food concentrations for red king crab (Paralithodes camtschaticus) larvae fed Artemia nauplii under laboratory conditions

Daily food intakes, optimal feeding regimes and food concentrations for laboratory reared Paralithodes camtschaticus (Tilesius, 1815) larvae were investigated. Artemia nauplii hatched at standard conditions were used as food. Daily food intakes of zoeae I–IV at 7–8 °C comprised 11.3, 22.4, 33.2, and 41.8 nauplii individuals (ind)^?1 day^?1, respectively, taking into account that wet weight of Artemia nauplii used for the experiments constituted 0.026 mg, dry weight 0.0042 mg. Optimal initial Artemia nauplii concentrations for feeding zoeae I–IV was determined as 400–600, 600–800, 800–1000 and 1000–1200 nauplii L^?1 respectively. Recommendations on using Artemia nauplii as food for red king crab larvae were outlined on the basis of experimental results. Growth, development and survival rates of zoeae I–IV reared in recycling water system at 7–8 °C and fed Artemia nauplii according to these recommendations were described.     

Effect of Sargassum wightii fucoidan on growth and disease resistance to Vibrio parahaemolyticus in Penaeus monodon post‐larvae

The polysaccharide – fucoidan was extracted from brown seaweed Sargassum wightii and its antibacterial activity was screened by agar well diffusion method. The maximum zone of inhibition observed was 15.66 mm in 20 mg mL^?1 concentration against Vibrio parahaemolyticus. The Minimum Inhibitory Concentration (MIC) of the fucoidan was 12 mg mL^?1 against V. parahaemolyticus. The fucoidan was then enriched with Artemia nauplii at four different concentrations such as 100, 200, 300 and 400 mg L^?1 for 12 h. The enriched Artemia nauplii were fed to Penaeus monodon post‐larvae for 20 days and the growth performance was assessed. The weight gain and SGR of the control group were 0.2432 g and 15.78%, respectively. But, in experimental groups fed with fucoidan enriched Artemia nauplii, the weight gain and SGR were increased and were respectively ranged from 0.2602 to 0.3161 g and from 16.11 to 17.05%. The P. monodon post‐larvae were challenged with V. parahaemolyticus for a period of 30 days showed a reduction in mortality percentage of experimental groups over the control group and it was ranged between 36.97 and 89.86%. During the challenge test, the V. parahaemolyticus load was also enumerated from the infected shrimp at every 10 day intervals. In the control group, the Vibrio load showed a linear increase in hepatopancreas and muscle tissues from 10th to 30th days of challenge test, whereas in the experimental groups, the Vibrio load established a declining trend with the advancement of challenged test.     

Complete and partial replacement of Artemia nauplii by Moina micrura during early postlarval culture of white shrimp (Litopenaeus schmitti)

Growth rate, soluble protein content, osmotic stress and digestive enzyme activity were studied in early Litopenaeus schmitti postlarvae under different feeding regimens, by partially or completely replacing Artemia nauplii with Moina micrura. Growth was significantly higher in the postlarvae fed with a mixture of M. micrura, Artemia nauplii and algae (0.030 mg dry weight (dw) larva^?1 day^?1, 17.4 ± 2.1% day^?1), together with the postlarvae fed on Artemia nauplii and algae (0.027 mg dw larva^?1 day^?1, 18.3 ± 1.9% day^?1). Complete replacement of Artemia nauplii by M. micrura produced the lowest growth rate (0.018 mg dw larva^?1 day^?1, 14.3 ± 1.6% day^?1) and induced the highest protease and α‐amylase activities and lower soluble protein contents. No significant difference among the treatments could be detected in postlarval resistance to osmotic stress. Based on the growth results, soluble protein content, enzymatic activity and osmotic stress resistance, we determined that the partial replacement of Artemia nauplii by M. micrura did not affect the growth, the soluble protein content and the nutritional state in the postlarvae of L. schmitti. To our knowledge, this is the first reported use of M.micrura as feed for early postlarvae of L. schmitti.     

Effect of feeding scheme and prey density on survival and development of Chinese mitten crab Eriocheir sinensis zoea larvae

The effect of feeding scheme and prey density on survival and development of Eriocheir sinensis zoea larvae was studied in three experiments. Different combinations and densities of rotifers (Brachionus rotundiformis) and newly hatched Artemia nauplii were fed to zoea larvae. Average survival at each stage, larval development (larval stage index, LSI), duration of zoeal stage and individual megalopa dry weight were compared among treatments. This study revealed that, under the experimental conditions, rotifers should be replaced with Artemia between the zoea 3 (Z3) and the zoea 4 (Z4) stage. The optimal rotifer feeding densities for zoea 1 (Z1) and zoea 2 (Z2) were 15 and 20 mL^?1 respectively, while the optimal Artemia feeding density for Z3, Z4 and zoea 5 (Z5) was 3, 5 and 8 mL^?1 respectively. Further trials in production scale are recommended.     

Hormone-induced ovulation, natural spawning and larviculture of Brazilian flounder Paralichthys orbignyanus (Valenciennes, 1839)

Mature Brazilian flounders Paralichthys orbignyanus were captured in coastal southern Brazil and their reproduction in captivity was studied. Brazilian flounder will spawn naturally in captivity when the water temperature is around 23 °C and 14 h of light is provided daily. Females were induced for ovulation and hand stripping using human chorionic gonadotropin, luteinizing hormone‐releasing hormone analogue or carp pituitary extract. There was no need to inject males, as running milt was observed during the spawning season. Fertilization and hatching rates were above 80% independent of the hormone used. Notochord length at hatching was 2.18±0.07 mm for larvae hatching from naturally spawned eggs. Larvae were reared in salt water (30–35 g L^?1) at 24 °C and under continuous illumination. Larviculture was with green water (Tetraselmis tetrathele 50 × 10⁴ cells mL^?1). Rotifers (10–20 ind mL^?1) were offered as first food 3 days after hatching and gradually replaced by Artemia nauplii (0.5–10 ind mL^?1). Larvae settled to the bottom 20 days after hatching and completed metamorphosis within a week after that. The total length for newly metamorphosed juveniles was 12.9±2.2 mm and the mean survival was 44.8%. The results demonstrate the feasibility of producing Brazilian flounder fingerlings for stock enhancement or grow‐out purposes.     

Effect of Rearing Density and Feeding Regimes on Growth and Survival of African Catfish,Heterobranchus longifilis (Valenceinnes, 1840) Larvae in a Closed Recirculating Aquaculture System

Heterobranchus longifilis larvae were reared over a 35 d period to evaluate the effects of stocking densities and feeding regimes on growth and survival. In experiment 1, larvae (12.3?±?2.1 mg) were stocked into glass aquaria at densities of 1, 2, 5, 10, 15, 20, and 25 larvae L^?1. Larvae were fed on Artemia nauplii ad libitum. Significant variations in terms of growth performance and feed utilization occurred at all levels of density treatments. Specific growth rate (SGR), body weight gain (BWG), and feed efficiency (FE) of the larvae decreased significantly as density increased. However, survival rate increased with the increase of stocking density. In experiment 2, larvae (13.4?±?1.1 mg) stocked at a density of 15 larvae L^?1, in the same conditions as experiment 1, were fed on three different regimes: Artemia nauplii; 35%?protein beef brain; and 35%?protein commercial catfish feed (CN⁺). SGR, BWG, and coefficient of variation (CV) of larvae fed on Artemia nauplii were significantly higher than those fed on beef brain and CN⁺. The survival rate of larvae fed on beef brain was significantly higher (88.40?±?9.75%) than those of Artemia (69.21?±?6.69%) and CN⁺ (40.40?±?6.22%). The results of this study suggest that the optimum stocking density is 15 larvae L^?1 and the beef brain can be used as alternative feed to Artemia in rearing H. longifilis larvae.     

Weaning requirements of larval mulloway,Argyrosomus japonicus

Mulloway (Argyrosomus japonicus) is an emerging aquaculture species in Australia, but there is a need to improve the production technology and lower costs, including those associated with larval rearing and live feeds. Three experiments were conducted to determine appropriate weaning strategies from live feeds, rotifers (Brachionus plicatilis) and Artemia, to cheaper formulated pellet diets. Experiment 1 examined the effects of feeding Artemia at different levels [0%, 50% or 100% ration of Artemia fed from 18 days after hatching (dah); based on current hatchery protocols] and a pellet diet from two larval ages (14 or 23 dah). In addition, rotifers were supplied to larvae in all treatments for the duration of the experiment (14–29 dah), at which time all larvae were successfully weaned onto the pellet diet. No significant (P>0.05) differences existed between the growth of fish fed a 50% and 100% ration of Artemia; however, fish fed a 0% ration of Artemia had significantly (P<0.05) reduced growth. The time of pellet introduction had no significant (P>0.05) effects on the growth of larvae. Experiments 2 and 3 were designed to determine the size [total length (TL), mm] at which mulloway larvae selected Artemia equally or in preference to rotifers, and pellet (400 μm) equally or in preference to Artemia respectively. Each day, larvae were transferred from a holding tank to experimental vessels and provided with rotifers (2 mL^?1), Artemia (2 mL^?1) or a combination of rotifers (1 mL^?1) and Artemia (1 mL^?1) (Experiment 2), and Artemia (2 mL^?1), a pellet diet or a combination of Artemia (1 mL^?1) and a pellet diet that was broadcast every 15 min (Experiment 3). After 1 h, a sub‐sample of larvae was randomly selected from each replicate vessel (n=5) and the gut contents were examined under a light microscope. Mulloway larvae began selecting Artemia equally to rotifers at 5.2 ± 0.5 mm TL and selected pellets equally to Artemia at 10.6 ± 1.8 mm TL. Our results have led to the establishment of weaning protocols for larval mulloway, which optimize larval growth while reducing feed cost by minimizing the amount of Artemia used during production.     

Uptake and metabolism of a particulate form of ascorbic acid by Artemia nauplii and juveniles

A study was conducted to establish whether a particulate form of ascorbic acid (AA), ascorbyl‐2‐phosphate (A2P), could be used to enrich Artemia. In the first experiment, we examined the efficiency of A2P conversion to and maintenance of AA by juvenile Artemia (1.5 mm, 5‐day‐old) held at 9000 L^?1 and 28 °C for 24 h. Maximal uptake and assimilation was >10 000 μg AA g^?1 dry weight (dw) (representing >1%Artemia dw) at enrichment rates of ≥1.2 g A2P L^?1. In the second experiment, a similar biomass of instar II/III nauplii (1 mm, 2‐day‐old) and juvenile (2.5 mm, 8‐day‐old) Artemia were enriched for 6 or 24 h at 28 °C before starvation for 6 or 24 h at 18 or 28 °C. At 0 h and after 6 and 24 h enrichment, AA levels were 485, 3468 and 11 080 μg g^?1 dw in nauplii and 122, 4286 and 12 470 μg g^?1 dw in juveniles. When Artemia nauplii or juveniles were enriched for 6 h and starved for 6 h at 18 or 28 °C, there was no significant reduction in AA. Continuation of starvation to 24 h at 18 and 28 °C reduced the level of AA to 3367 and 2482 μg g^?1 dw in nauplii and 3068 and 2286 μg g^?1 dw in juveniles. After 24 h enrichment, 6 h of starvation at 18 and 28 °C reduced AA to 8847 and 7899 μg g^?1 dw in nauplii and to 9053 and 8199 μg g^?1 dw in juveniles. Continuation of starvation to 24 h at 18 and 28 °C further reduced AA levels in nauplii to 6977 and 4078 μg g^?1 dw and to 7583 and 5114 μg g^?1 dw in juveniles. This study demonstrated that A2P could be assimilated as AA in the body tissue of different‐sized Artemia in a dose‐dependant manner and AA was depleted during starvation depending on time and temperature.     

Effects of dietary Lactobicillus plantarum on the growth,carcass quality,and immune response of African catfish (Clarias gariepinus) challenged with Salmonella typhi

An experiment was conducted to investigate the effects of Lactobacillus plantarum on the production of African catfish (Clarias gariepinus). Five experimental diets containing 0, 10³, 10⁵, 10⁷, and 10⁹ CFU of Lactobacillus plantarum g^?1 diet (T₁–T₅ treatments respectively) were fed to African catfish (Clarias gariepinus) (9.20 ± 0.1 g initial body mass), for 70 days. Results indicated significantly lower growth performance in the fish fed diet without probiotics and in those fed diet with the least probiotic level. Treatments with probiotics significantly improved the blood profile and carcass protein but significantly reduced the carcass fat (P < 0.05); these treatments also marginally improved the carcass minerals in comparison with the treatment without probiotic (P < 0.05). Challenging the fish fed the experimental diets with Salmonella typhi showed higher immunity of fish fed the probiotic diets than those fed the nonprobiotic diet. Duncan’s multiple range test showed that the best fish performance was observed with 10³ CFU g^?1 L. plantarum for very parameter measured. However, regression analyses showed the optimum level of the bacteria to be 10^4.13–10⁵ CFU g^?1     

Improved techniques for rearing mud crab Scylla paramamosain (Estampador 1949) larvae

A series of rearing trials in small 1 L cones and large tanks of 30–100 L were carried out to develop optimal rearing techniques for mud crab (Scylla paramamosain) larvae. Using water exchange (discontinuous partial water renewal or continuous treatment through biofiltration) and micro‐algae (Chlorella or Chaetoceros) supplementation (daily supplementation at 0.1–0.2 million cells mL⁻¹ or maintenance at 1–2 millions cells mL⁻¹), six different types of rearing systems were tried. The combination of a green‐water batch system for early stages and a recirculating system with micro‐algae supplementation for later stages resulted in the best overall performance of the crab larvae. No clear effects of crab stocking density (50–200 larvae L⁻¹) and rotifer (30–60 rotifers mL⁻¹) and Artemia density (10–20 L⁻¹) were observed. A stocking density of 100–150 zoea 1 (Z1) L⁻¹, combined with rotifer of 30–45 mL⁻¹ for early stages and Artemia feeding at 10–15 nauplii mL⁻¹ for Z3–Z5 seemed to produce the best performance of S. paramamosain larvae. Optimal rations for crab larvae should, however, be adjusted depending on the species, larval stage, larval status, prey size, rearing system and techniques. A practical feeding schedule could be to increase live food density from 30 to 45 rotifers mL⁻¹ from Z1 to Z2 and increase the number of Artemia nauplii mL⁻¹ from 10 to 15 from Z3 to Z5. Bacterial disease remains one of the key factors underlying the high mortality in the zoea stages. Further research to develop safe prophylactic treatments is therefore warranted. Combined with proper live food enrichment techniques, application of these findings has sustained a survival rate from Z1 to crab 1–2 stages in large rearing tanks of 10–15% (maximum 30%).