A diet of fructose‐enriched Artemia improves the response of juvenile Litopenaeus vannamei shrimp to acute low‐salinity challenge

The Pacific white shrimp (Litopenaeus vannamei), as an economically important species, has been reared in low‐salinity water during the last decade. To investigate how juvenile L. vannamei shrimp fed with fructose‐enriched Artemia respond to acute low‐salinity stress, the shrimp were randomly divided into four treatment groups, three groups were fed with Artemia enriched with either 100, 200 and 300 mg L^?1 of fructose and a control group fed with Artemia with no enrichment for 10 days. The results showed that the 300 mg L^?1 fructose group demonstrated the maximum survival rate and glycogen content. Additionally, the 300 mg L^?1 fructose group showed significantly higher Na⁺/K⁺‐ATPase activity, total antioxidant capacity, and expression levels of Na⁺/K⁺‐ATPase α‐subunit, V‐H ATPase α‐subunit, hexokinase, phosphofructokinase, antioxidants (SOD, CAT, GPX) and Hsp70 mRNA when compared with the control group. Furthermore, after exposure to low salinity, the mRNA levels of phosphofructokinase, V‐H ATPase α‐subunit, GPX, p38, JNK and Rac1 stayed constant in shrimp fed with fructose‐enriched Artemia but changed significantly in the control group. Thus, a diet of fructose‐enriched Artemia can improve the osmoregulation and survival of juvenile L. vannamei shrimp exposed to low salinities.     

Effects of formalin on total haemocytes count and histopathological changes in the shrimp Litopenaeus schmitti (Pérez‐Farfante & Kensley 1997)

Formalin is used in shrimp industry to eliminate ectoparasites and as a disinfectant. However, the effect of formalin on shrimp's defense mechanism is unknown. Several biomarkers were used to assess the immune response of juveniles of the shrimp Litopenaeus schmitti exposed to different concentrations of formalin (10, 25 and 50 mg L^?1) during 24 and 48 h. Formalin concentrations of 25 and 50 mg L^?1 produced a significant reduction in the total haemocyte count at both 24 and 48 h. Peroxidase and phenoloxidase activity did not show variations. The total protein concentration in haemolymph of shrimps was not significantly different between experimental groups. Histological analysis showed hyperplasia in the gills of animals exposed at 10 mg L^?1 for 24 h; however, the exposure at 25 and 50 mg L^?1 caused necrosis in gills, hepathopancreas and the antennal gland.     

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 chlorine to different sizes of black tiger shrimp (Penaeus monodon) in low-salinity shrimp pond water

An experiment was conducted, in a dark room with controlled temperature (27.3–28.4 °C), to determine the acute toxicity of chlorine concentration to black tiger shrimp (Penaeus monodon fabicus) of sizes 0.02 g, 2.75 g, 8.47 g and 23.65 g. Toxicity tests on each of these shrimp sizes were run in triplicate in glass jars under static conditions without media renewal. The concentration of active chlorine that killed 50% of the shrimp of each size after 24‐h exposure (LC₅₀‐24 h) was used as an indicator of acute toxicity. Chlorine concentrations applied in the shrimp toxicity test ranged from 2.0 to 14.5 mg L^?1 in shrimp pond water. As the test water contained total suspended solids of 22.0–85.0 mg L^?1 and total ammonia nitrogen of 0.18–0.40 mg L^?1, the resultant concentrations of combined residual chlorine ranged from 0.6 to 3.5 mg L^?1, which were the effective doses causing shrimp mortality. The test results showed that 24‐h LC₅₀ for average shrimp size at 0.02, 2.75, 8.47 and 23.65 g occurred in water containing combined residual chlorine at a concentration of 0.91, 1.39, 1.74 and 1.98 mg L^?1, for which the original application doses were 6.96, 2.05 11.50 and 13.34 mg L^?1 respectively.     

Effect of hot water extracts of brown seaweeds Sargassum spp. on growth and resistance to white spot syndrome virus in shrimp Penaeus monodon postlarvae

An experiment was conducted to evaluate the effect of a hot water extract of brown seaweeds Sargassum duplicatum and Sargassum wightii on the growth and white spot syndrome virus (WSSV) resistance in shrimp Penaeus monodon postlarvae (PL). Artemia nauplii (instar II) were enriched with both seaweed extracts at various concentrations (250, 500 and 750 mg L^?1) and fed to the respective P. monodon (PL15–35) group for 20 days. A control group was also maintained without seaweed extract supplementation. The weight gain of the experimental groups was significantly higher (0.274–0.323 g) than the control group (0.261 g). Similarly, the specific growth rate was also significantly higher (16.27–17.06%) in the experimental groups than in the control group (16.03%). After 20 days of the feeding experiment, the shrimp PL were challenged with WSSV for 21 days. During the challenge test, the control shrimp displayed 100% mortality within 8 days. In contrast, the mortality percentage of the highest concentration (750 mg L^?1) of seaweed extract enriched Artemia nauplii fed shrimp was 54–79%. Comparatively, low mortality was observed in S. wightii extract‐enriched Artemia nauplii fed shrimp. The polymerase chain reaction analysis indicated the concentration‐dependent infection of WSSV in P. monodon PL.     

Effects of total ammonia,temperature and salinity on the mortality and viral replication of WSSV‐infected Chinese shrimp (Fenneropenaeus chinensis)

In this study, we evaluated the effects of three factors, total ammonia, temperature and salinity, on the mortality of and viral proliferation in white spot syndrome virus (WSSV)‐infected Chinese shrimp. Shrimp maintained in 30‰ seawater at 25°C with 0.34 mg L^?1 total ammonia (control group) were injected with approximately 20 WSSV particles per shrimp and subsequently subjected to the following conditions: 30‰ seawater at 25°C, with 6 mg L^?1 (N1 group) or 14 mg L^?1 (N2 group) total ammonia; 30‰ seawater at 18°C (T1 group) or 30°C (T2 group), with 0.34 mg L^?1 total ammonia and 20‰ (S1 group) or 40‰ (S2 group) seawater at 25°C, with 0.34 mg L^?1 total ammonia. An anova analysis revealed that the cumulative mortality of WSSV‐infected Chinese shrimp was significantly lower when reared in the T1 group compared to that of the T2 and control group. Similarly, the mortality of the shrimp in the S1 group was also significantly lower than that of the S2 and control group. No significant differences were detected among the N1, N2 and control groups. Accordingly, the WSSV level in the T1 and S1 groups was significantly lower than those in the control, T2 or S2 groups respectively. No significant differences in viral loads were detected among the control, N1 and N2 groups. The transfer of Chinese shrimp to lower temperature and lower salinity enhanced their resistance to WSSV infection, whereas a change in the concentration of total ammonia had no significant effect on the mortalities and viral loads of WSSV‐infected shrimp.     

Impacts of chloramine‐T treatment on antioxidant enzyme activities and genotoxicity in rainbow trout,Oncorhynchus mykiss (Walbaum)

Juvenile rainbow trout Oncorhynchus mykiss (Walbaum) were exposed to therapeutic, and higher concentrations of chloramine‐T (Cl‐T) to assess the effects of this chemical on the antioxidant enzyme system and genetic structure. Red blood cells acetylcholinesterase, ?‐aminolevulinic acid dehydratase, paraoxonase and liver glutathione S‐transferase activity were increased at 10 and 20 mg L^?1 Cl‐T‐exposed fish, while they were decreased at 30 mg L^?1 Cl‐T‐exposed fish. On the other hand, liver catalase activity and liver protein levels increased at 10 mg L^?1 and decreased at 20 and 30 mg L^?1 concentrations of Cl‐T. Liver super‐oxide dismutase activity decreased at 10 mg L^?1 and 20 mg L^?1 Cl‐T and increased at 30 mg L^?1 of Cl‐T. Compared to control, comet assay indicated that Cl‐T did not cause significant DNA damage to red blood cells of the fish. Results indicate that 10 or 20 mg L^?1 Cl‐T can be safely used to prevent or treat external parasitic and bacterial infection of rainbow trout.     

Promotion of callus propagation by 5‐aminolevulinic acid in a Laminaria japonica sporophyte

The effects of 5‐aminolevulinic acid (ALA) on the induction and growth of callus‐like cells in Laminaria japonica were investigated in explants obtained from basal, middle and apical portions along the sporophyte. 5‐Aminolevulinic acid treatment promoted the induction of callus‐like cells in explants obtained from all portions, and the induction rate was higher when a concentration of 50–500 mg L^?1 of ALA was used. The promotion was especially remarkable in apical explants, and the induction was 10–14 times higher in the 100–500 mg L^?1 range than that in the 0 mg L^?1. The cell division rate of callus‐like cells showed the highest value in the explants cultured with 500 mg L^?1 of ALA for 14 days. The promotion of the cell division rate by culturing with 500 mg L^?1 ALA was also observed under white, blue and red lights. The callus‐like cells, which were cultured in 500 mg L^?1 of ALA for 2 months, had many clear chloroplasts. After 3 months, young thalli occurred. These results suggest that the ALA treatment is effective for stable propagation of callus‐like cells in L. japonica.     

Effect of promoted natural feed on the production,nutritional, and immunological parameters of Litopenaeus vannamei (Boone, 1931) semi‐intensively farmed

The effect of promoted biota on the production parameters, water quality, nutritional and immunological condition of Litopenaeus vannamei was assessed in semi‐intensive ponds. Earthen ponds were used as experimental units: three with formulated + natural promoted feed + shrimp (T1), three with formulated feed + shrimp (T2), and three with promoted natural feed without shrimp (Control). The dissolved oxygen (DO) levels were optimal for all treatments (≥6 mg L^?1) as well as the pH (8.4–8.6). Total ammonia nitrogen was greater in T2 (0.10 mg L^?1) than T1 (0.07 mg L^?1) and the Control (0.06 mg L^?1). Phytoplankton, zooplankton and benthos were more abundant in T1 and the Control. The promotion of natural feed had a positive effect on all the production parameters of shrimp with an increase of 19.0%, 3.5% and 23.9% in weight gain, survival, and final biomass, respectively; also it was observed a decrease of 13.9% in feed conversion ratio. No differences in haemolymph parameters were observed for nutritional indicators (glucose, cholesterol, proteins, and triglycerides) nor for immunological response (phenoloxidase and prophenoloxidase). The results indicate that the promotion of biotic communities enhances the production parameters of farmed shrimp, without affecting the nutritional and immunological status. Also the water quality was improved by the presence of biota.     

Production of Tiger Shrimp (Penaeus monodon) in Potassium Supplemented Inland Saline Sub-Surface Water

Abstract

Potassium deficient inland saline (10 g L^?1 salinity) well water was supplemented with muriate of potash to achieve 50% (57 mg L^?1) and 100% (114 mg L^?1) of seawater potassium concentration and used for the production of tiger shrimp (Penaeus monodon). Total mortality was observed in non-supplemented water within 6 days compared to 88.0% survival in K⁺100% and 85.3% survival in K⁺50% up to 60 days. P. monodon were subsequently cultured for 110 days in two identical 0.25-ha ponds supplied with water of 10 g L^?1 and supplemented with the potassium equivalent of 35% of seawater. Survival and production were 55.8% to 64.25% and 157.70 kg (630.8 kg ha^?1) to 172.75 kg (691 kg ha^?1), respectively.     

A study on the influence of selected Indian herbal active principles on enhancing the immune system in Fenneropenaeus indicus against Vibrio harveyi infection

Five herbs such as Acalypha indica, Hygrophila spinosa, Picrorhiza kurooa, Tinospora cordifolia and Zingiber officinale were selected to screen for the in vitro immunostimulant activity against the shrimp pathogen Vibrio harveyi using different organic polar and non-polar solvents. After initial screening, the best extract of the five herbs was mixed thoroughly in equal proportion and made it an artificial immunostimulant diets (ISD) such as ISD-1(500), ISD-2 (1,000), ISD-3 (1,500) and ISD-4 (2,000) mg?kg^?1. The control diet was prepared without adding immunostimulant herbal extracts. The Indian white shrimp, Fenneropenaeus indicus having the weight of 8.0?±?1.0?g, were fed with the above diets for 60?days. After the completion of feeding trail, they were challenged with V. harveyi at the rate of 10⁷CFU/ml and found out the cumulative mortality, growth parameters, haematological and immunological parameters. The weight gain and specific growth rate were significantly (P?<?0.05) increased from the control group to experimental group. The immunostimulant active principles helped to decrease the coagulation time and improved the total haemocyte count (THC), phagocytosis, phenol oxidase (PO) activity, haemagglutinin activity and bacterial clearance.     

The effect of vitamin C on stress withstanding capability in the juvenile soft-shelled turtle (Pelodiscus sinensis)

The study was conducted to determine the effect of dietary supplementation of vitamin C on anti‐acid stress ability in juvenile soft‐shelled turtle. The soft‐shelled turtles were fed vitamin C supplemented diets at levels of 0, 250, 500, 2500, 5000 and 10 000 mg kg^?1 for 4 weeks. The results showed that the phagocytic rate of blood cell in the group fed vitamin C deficient diets, the serum bacteriolytic activity in the two groups fed vitamin C supplemented diet at 0 and 250 mg kg^?1 and the serum bactericidal activity in all groups after acid stress significantly decreased compared with those of before stress (P < 0.1). The phagocytic rate of blood cells in the two groups fed vitamin C supplemented diet at 2500 and 5000 mg kg^?1 were significantly higher than those of the four groups fed at 0, 250, 500 and 10 000 mg kg^?1 (P < 0.01). The serum bacteriolytic activity in the groups fed vitamin C supplemented diet at 500, 2500, 5000 and 10 000 mg kg^?1 were significantly higher than that of the group fed vitamin C deficient diets (P < 0.05), and the two groups fed vitamin C at 2500 and 5000 mg kg^?1 were significantly higher than those of the groups fed at 250 and 10 000 mg kg^?1 (P < 0.05). The serum bactericidal activities in the four groups fed vitamin C supplemented diet at 500, 2500, 5000 and 10 000 mg kg^?1 were significantly higher than those of the two groups fed at 0 and 250 mg kg^?1 diet (P < 0.01), and the two groups fed vitamin C at 2500 and 5000 mg kg^?1 were significantly higher than those of the two groups fed at 500 and 10 000 mg kg^?1 (P < 0.1). These results suggest that supplementation of vitamin C higher than 250 mg kg^?1 is necessary to reduce the adverse effects of acid stress.     

Stocking strategies for production of Litopenaeus vannamei (Boone) in amended freshwater in inland ponds

The performance of the Pacific white shrimp Litopenaeus vannamei (Boone) under various stocking strategies was evaluated in earthen ponds filled with freshwater amended with major ions. Six 0.1‐ha earthen ponds located in Pine Bluff, AR, USA, were filled with freshwater in 2003 and 2004, and potassium magnesium sulphate added to provide 50 mg K⁺ L^?1 and stock salt added to provide 0.5 g L^?1 salinity. In 2003, three ponds either were stocked with PL₁₅ shrimp (39 PL m^?2) for 125 days of grow out or with PL₂₅ shrimp for 55 days (23 PL m^?2) followed by a 65‐day (28 PL m^?2) grow‐out period. In 2004, ponds were stocked with 7, 13 or 30 PL₁₅ m^?2 for 134 days of grow out. Salinity averaged 0.7 g L^?1 during both years, and concentration of SO₄^?2, K⁺, Ca²⁺ and Mg²⁺ was higher, and Na⁺ and Cl^? was lower in amended pond water than in seawater at 0.7 g L^?1 salinity. Potassium concentration in amended water was 52–61% of the target concentration. Shrimp yields ranged from 3449 kg ha^?1 in 2003 to 4966 kg ha^?1 in 2004 in ponds stocked with 30–39 PL₁₅ m^?2 for a 125–134‐day culture period. At harvest, mean individual weight ranged from 17.1 to 19.3 g shrimp^?1. In ponds stocked with PL₂₅ shrimp, yields averaged 988 and 2462 kg ha^?1 for the 1st and 2nd grow‐out periods respectively. Gross shrimp yield in 2004 increased linearly from 1379–4966 kg ha^?1 with increased stocking rate. These experiments demonstrated that L. vannamei can be grown successfully in freshwater supplemented with major ions to a final salinity of 0.7 g L^?1.     

Antibacterial activity of immobilized silver nanoparticles on TEPA‐Den‐SiO2 against shrimp pathogen,Vibrio sp. Persian1

In this study, we prepared silver nanoparticles immobilized onto silica sand beads as an antibacterial material against pathogenic luminous Vibrio sp. Persian1. Silica beads were modified with 3‐aminopropyltriethoxysilane (APTES), cyanuric chlorid and tetraethylene pentamine, and silver nanoparticles were generated in various concentrations (0.5, 1, and 2 mM g^?1 of silica beads) of AgNO₃ on the surface using chemical reduction. Ag/TEPA‐Den‐SiO₂ samples were characterized by TEM, FE‐SEM/EDS, FT‐IR and ICP OES and their antibacterial activity assayed by zone of inhibition and test tube tests against pathogenic Vibrio sp. The results of the zone inhibitory test revealed that all the Ag/TEPA‐Den‐SiO₂ samples had an antibacterial effect against luminous Vibrio sp. Persian1. In addition, the tube test results showed 100% killing of bacteria in 2 h contact period. Ag/TEPA‐Den‐SiO₂ samples maintained their antibacterial activity after 14‐day immersion in seawater by slow release of silver ions. These results suggest that Ag/TEPA‐Den‐SiO₂ substrates could be effective antibacterial materials for disinfection of seawater used to culture Penaeid shrimp larvae.     

Effects of acute change in salinity and moulting on the infection of white leg shrimp (Penaeus vannamei) with white spot syndrome virus upon immersion challenge

In the field, moulting and salinity drop in the water due to excessive rainfall have been mentioned to be risk factors for WSSV outbreaks. Therefore, in this study, the effect of an acute change in environmental salinity and shedding of the old cuticle shell on the susceptibility of Penaeus vannamei to WSSV was evaluated by immersion challenge. For testing the effect of abrupt salinity stress, early premoult shrimp that were acclimated to 35 g L^?1 were subjected to salinities of 50 g L^?1, 35 g L^?1, 20 g L^?1, 10 g L^?1 and 7 g L^?1 or 5 g L^?1 and simultaneously exposed to 10^5.5 SID₅₀ mL^?1 of WSSV for 5 h, after which the salinity was brought back to 35 g L^?1. Shrimp that were transferred from 35 g L^?1 to 50 g L^?1, 35 g L^?1 and 20 g L^?1 did not become infected with WSSV. Shrimp became infected with WSSV after an acute salinity drop from 35 g L^?1 to 10 g L^?1 and lower. The mortality in shrimp, subjected to a salinity change to 10 g L^?1, 7 g L^?1 and 5 g L^?1, was 6.7%, 46.7% and 53.3%, respectively (P < 0.05)_. For testing the effect of moulting, shrimp in early premoult, moulting and post‐moult were immersed in sea water containing 10^5.5 SID₅₀ mL^?1 of WSSV. The resulting mortality due to WSSV infection in shrimp inoculated during early premoult (0%), ecdysis (53.3%) and post‐moult (26.72%) demonstrated that a significant difference exists in susceptibility of shrimp during the short moulting process (P < 0.05). The findings of this study indicate that during a drop in environmental salinity lower than 10 g L^?1 and ecdysis, shrimp are at risk for a WSSV infection. These findings have important implications for WSSV control measures.     

A novel micro‐organism for removing excess ammonia‐N in seawater ponds and the effect of Cobetia amphilecti on the growth and immune parameters of Litopenaeus vannamei

To investigate the feasibility of using micro‐organisms for ammonia‐N removal, six strains were isolated from Chinese white shrimp, Fenneropenaeus chinensis, seawater culture ponds in Dongying (Shandong, China). Of these, strain DY‐01, which exhibited the highest capacity to degrade ammonia‐N, removed 61.7% of the total ammonia‐N (50 mg/L) in 8 hr. An investigation of the factors affecting the removal efficiency indicated the optimum conditions to be 30°C, pH 8.0, and a salinity level of 30 g/L; 16S rDNA gene sequencing and biochemical analysis identified strain DY‐01 as Cobetia amphilecti, which has not previously been reported to degrade ammonia‐N. This strain also boosted the growth of Pacific white shrimp, Litopenaeus vannamei (p < .05), at a concentration of 10⁷ CFU/mL, with no harmful effects on the shrimp's immune system. This study has thus identified a novel aerobic nitrifying bacterium that is potentially an excellent candidate for improving the water quality in mariculture ponds.     

Survival and behavioural responses of cool and warm water fish sedated with AQUI‐S®20E (10% eugenol) at high loading densities

This study evaluated the effects of AQUI‐S^®20E (10% eugenol) sedation on the survival and behaviour of yellow perch Perca flavescens (Mitchill) and Nile tilapia Oreochromis niloticus L. held in high loading densities. Fish were held in 0–300 mg L^?1 AQUI‐S^®20E (0–30 mg L^?1 eugenol) for up to 10 h in static tanks. At 17°C, yellow perch held in 200 and 300 mg L^?1 AQUI‐S^®20E were lightly sedated for up to 7 h. Yellow perch at 200 and 300 mg L^?1 AQUI‐S^®20E also had >95% mean survival 7‐days post exposure using loading densities up to 360 g L^?1. Nile tilapia were only sedated for ≤3 h in concentrations up to 300 mg L^?1 at 22°C and had >90% mean survival at loading densities ≤480 g L^?1. Ammonia in tanks increased significantly as loading density increased, but treatment with AQUI–S^®20E did not reduce ammonia accumulation. Results suggest that AQUI–S^®20E was effective to sedate yellow perch and Nile tilapia at high loading densities, but sedation varied with loading density and species.     

Effect of hypo- and hyper-saline conditions on osmolarity and fatty acid composition of juvenile shrimp Litopenaeus vannamei (Boone, 1931) fed low- and high-HUFA diets

Litopenaeus vannamei (Boone) grown in ponds are exposed to salinities of less than 5 g L^?1 during inland shrimp culture or to more than 40 g L^?1 from evaporation and reduced water exchange in dry, hot climates. However, dietary requirements for shrimp grown in low or high salinities are not well defined, particularly for fatty acids. Feeding shrimp postlarvae with highly unsaturated fatty acids (HUFA) enhances tolerance to acute exposure to low salinity, as a result of better nutritional status, or/and specific effects of HUFA on membrane function and osmoregulation mechanisms. This study analysed the effect of HUFA supplementation (3% vs. 34%) on L. vannamei juveniles reared for 21 days at low (5 g L^?1), medium (30 g L^?1) and high salinities (50 g L^?1). Juveniles grown at 5 g L^?1 had lower survival compared with controls (30 g L^?1) or shrimp grown at 50 g L^?1, but no significant effect on survival was observed as a result of HUFA enrichment. In contrast, growth was significantly lower for shrimp grown at 50 g L^?1, but this effect was compensated by the HUFA‐enriched diet. Osmotic pressure in haemolymph was affected by salinity, but not by HUFA enrichment. Shrimp fed HUFA‐enriched diets had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in hepatopancreas and gills. These results demonstrate that growth at high salinities is enhanced with diets containing high HUFA levels, but that HUFA‐enriched diets have no effect on shrimp reared at low salinities.     

Immune responses of Litopenaeus vannamei to non‐ionic ammonia stress: a comparative study on shrimps in freshwater and seawater conditions

To investigate the effect of non‐ionic ammonia (NH₃‐N) stress (0.1 and 0.5 mg L^?1) on the immunity of Litopenaeus vannamei cultured in long‐term freshwater, the total haemocyte count (THC), the activity of phenoloxidase (PO), nitric oxide synthase (NOS), superoxidase dismutase (SOD) and the content of malondialdehyde (MDA) were determined and further compared with those of seawater shrimps. The results showed that NH₃‐N stress significantly reduced THC and the activity of PO and SOD (P < 0.05). Under 0.1 mg L^?1 NH₃‐N stress, NOS activity increased first and then decreased significantly, while it dropped dramatically under 0.5 mg L^?1 NH₃‐N stress (P < 0.05). During NH₃‐N stress, MDA content increased continuously, and the MDA content in hepatopancreas of freshwater shrimps was higher than that of seawater shrimps. It was concluded that NH₃‐N stress significantly influenced the non‐specific immunity and could also upset the balance of antioxidant system of L. vannamei in both freshwater and seawater shrimps. Compared with in seawater, the shrimps in freshwater were more vulnerable to NH₃‐N stress because of higher lipid peroxidation and lower immunity.     

Effects of stocking density and water conditioners on yolk‐sac larvae of two marine finfish during simulated air transport

As marine finfish aquaculture expands, there is an increasing interest in the ability to ship early life stages from breeding centres to hatcheries so that each hatchery does not have to maintain its own broodstock. Here, we conducted 24 h air‐shipping simulations with yolk‐sac larvae of California yellowtail (CYT; Seriola lalandi) and white seabass (WSB; Atractoscion nobilis) to help fill in the informational gaps for shipping marine fish larvae. We examined the effects of a pH buffer on water quality, post‐shipping larval survival and subsequent survival to first feeding at larval densities of 1000, 3000, 6000 and 9000 larvae L^?1. The pH buffer, 8.3 Trizma^®, was tested at varying concentrations of zero (NT = 0.00 g L^?1), low (LT = 0.75 g L^?1), medium (MT = 1.5 g L^?1) and high (HT = 3.0 g L^?1). Trials were conducted using replicate 2 L aquarium bags filled with 500 mL of seawater and held in a water bath at 19–20°C. Results showed an interspecific difference in survival at the highest shipping densities under these experimental conditions. Shipping densities up to 6750 CYT larvae L^?1 or 3000 WSB larvae L^?1 consistently yielded >90% survival immediately after simulated shipment and >85% survival 48 h after the simulations. Furthermore, at these densities, pH was maintained at ~8.0 when buffered at 1.5 g L^?1. The highest tested densities of 9580 CYT larvae L^?1 and 9940 WSB larvae L^?1, yielded lower survival 69–79% and 0.0–1.3% respectively after 24 h. Final pH in the high density CYT trials were unsatisfactory (below 7.0), regardless of the buffer concentration; however pH in the WSB high density trials improved with increasing buffer concentration. On the basis of the results from these air‐shipping simulations, we recommend CYT and WSB larvae be shipped in seawater with 1.5 g L^?1 Trizma^® at densities not greater than 6750 larvae L^?1 for CYT and 3000 larvae L^?1 for WSB. We believe this represents an important step in improving long distance transport protocols for these species and provides useful guidance in air transport of other economically and ecologically important marine species. Additional research is warranted to compare these simulation results with those from actual air shipments, as we did not account for factors that may vary in flight like temperature and pressure variations, and physical agitation.