Salinity Stress Test Research Articles

Enhancement of Penaeus monodon shrimp postlarvae growth and survival without water exchange using marine Bacillus pumilus 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.

Viability of culturing pink shrimp Farfantepenaeus duorarum in low-salinity groundwater from the Yucatán Peninsula (SE, México)

In the Gulf of Mexico constraints linked to the supply of post-larvae (PL) and legal pressures associated with the introduction of a non-native species have been the motives behind research on the aquaculture of the native shrimp. In the present study, the growth and survival of 25-day-post-larvae (PL-25) of the pink shrimp Farfantepenaeus duorarum in saline groundwaters were evaluated. During the experiment the shrimps were acclimated from 36 psu to 5 psu utilizing various acclimation times ( T1 = 38 h, T2 = 42 h, and T3 = 45 h) with a variable rate of salinity reduction ( T1 = 9.9% h − 1 , T2 = 11.8% h − 1 , and T3 = 11.4% h − 1 ). After a 1-day acclimation period there were no differences ( P > 0.05) in survival between treatments (80.7 ± 3.5%). The salinity reduction rate of T1 (low acclimation time) was selected to acclimatize the PL for the nursery experiment due to the high survival rate recorded after the salinity stress test. During the nursery experiment, shrimp at a density of 80 PL m − 2 had the highest growth rate (20 mg week − 1 ) ( F (2,9) = 10.73; P < 0.05) and survival rate (79%) ( F (2,9) = 4.93; P < 0.05) in comparison to other densities (150 PL m − 2 ; 250 PL m − 2 ). The PL growth was adjusted to a non-linear regression function (0.030 * e (0.035 * d)). Shrimp at 80 PL m − 2 ( t = 0.87) and 150 PL m − 2 ( t = 1.54) showed isometric growth (Ho = b = 3). Temperature was the only environmental variable that explained the most consecutive additional variance (80.1%) in the PL weight. The temperature–growth response curve was fitted to a generalized additive model (GAM). Results from this research demonstrate that F. duorarum (PL-25) can be successfully acclimated to low-salinity (5 psu) conditions with a high percentage of survival and an acceptable growth rate in the nursery phase (45 days). In the future efforts should be made to improve survival at higher densities in order to make production profitable.

EFFECTS OF N3-HUFA ENRICHED DAPHNIA MAGNA ON GROWTH, SURVIVAL, STRESS RESISTANCE, AND FATTY ACID COMPOSITION OF LARVAE OF PERSIAN STURGEON (ACIPENSER PERSICUS)

Effects of Daphnia magna enriched with cod liver oil (CLO) as a source of highly unsaturated fatty acid (HUFA) on growth, survival, stress resistance, and fatty acid composition of the Persian sturgeon larvae were evaluated. Daphnia enriched for three different time periods (3, 6, and 9 hours) and non-enriched Daphnia were fed to the Persian sturgeon larvae (average weight 61.6±0.4mg) during 14 days. The highest n3-HUFA content was found in Daphnia enriched for 9 hours (0.69mg g-1 DW) and the highest n3-HUFA content of the larvae was also found in those larvae fed with Daphnia enriched for 9 hours (2.39mg/g-1DW). A significant growth difference between larvae fed with enriched and non-enriched Daphnia was observed (p 0.05). Furthermore, the highest pH stress resistance was found in those larvae fed with Daphnia enriched for 9 and 6 hours (p<0.05). A salinity stress test did not show significant differences among the treatments.

Use of periphytic cyanobacterium and mixed diatoms coated substrate for improving water quality, survival and growth of Penaeus monodon Fabricius postlarvae

An eco-friendly method was established by using periphyton coated substrate (a cyanobacterium or mixed diatoms) to improve water quality, survival and growth of Penaeus monodon postlarvae (PL) in a shrimp hatchery system without changing water. Polyvinyl chloride (PVC) pipes (2 cm × 2 cm) were used as the substrate to grow pure cultures of cyanobacterium and diatoms. P. monodon (PL1) were cultured in 40 L glass tanks containing 30 L filtered-seawater and stocked at a density of 50 PLs L − 1 . Two treatments using i) cyanobacterium coated substrate ( Oscillatoria), ii) mixed diatoms coated substrate ( Amphora, Navicula and Cymbella), and a control (without substrate) were employed in this experiment. The experiment was run in triplicate for a period of 16 days (PL16) whereafter the PLs are normally stocked in growout ponds. Tanks with Oscillatoria coated substrate had the lowest ( P < 0.05) concentrations of total ammonia nitrogen (TAN, 0.03 ± 0.0 mg L − 1 ); nitrite–nitrogen (NO 2–N, 0.01 ± 0.0 mg L − 1 ) and soluble reactive phosphorus (SRP, 0.05 ±0.0 mg L − 1 ) in comparison to mixed diatoms (0.82 ± 0.02; 0.52 ± 0.05; 0.35 ± 0.01 mg L − 1 for TAN, NO 2–N and SRP, respectively) and control tanks (1.14 ± 0.01; 0.80 ± 0.02; 0.53 ± 0.04 mg L − 1 for TAN, NO 2–N and SRP, respectively). In addition, nutrients in diatoms treated tanks were significantly lower ( P < 0.05) than the control. Oscillatoria was more effective in reducing TAN (1.40 g m − 2 day − 1 ), NO 2–N (0.07 g m − 2 day − 1 ) and SRP (0.06 g m − 2 day − 1 ) than the mixed diatoms. Furthermore, shrimp cultured in tanks containing periphyton coated substrate showed significantly higher survival (51.3 ± 0.6%–60.0 ± 1.1%) than those reared in the periphyton free control tanks (36.8 ± 0.3%). The specific growth rates (dry weight) of the PLs was the highest in the diatoms tanks (28.02 ± 0.01%) followed by the Oscillatoria (22.83 ± 0.03%) and the control tanks (19.83 ± 0.05%) ( P < 0.05). The PLs produced in both substrate based systems exhibited higher resistance to reverse salinity stress test than those reared in the control tanks (36.7 ± 4.1 to 43.3 ± 8.2% survival compared to 26.7 ± 8.2%) ( P < 0.05). The protein, lipid and carbohydrate levels in PLs reared in tanks with mixed diatoms coated substrate were higher than for PLs grown in control tanks. This study illustrated the beneficial effects of periphyton coated substrate in improving water quality, growth and survival of shrimp larvae grown in shrimp hatchery system without water exchange.

Salinity stress test and its relation to future performance and different physiological responses in shrimp postlarvae

This review evaluates the use of the salinity stress test (SST) as an index of postlarvae (PL) quality, either at the end of experimental treatments or to predict performance during stocking and growout. The SST is easy to apply and does not require specialized equipment, hence its popularity. However, predictive value of the test seems to be limited to short-term performance during future culture. To determine to what extent SST depends on osmoregulation, the mechanisms in crustaceans are briefly reviewed, with particular emphasis on studies related to SST in PL penaeid shrimp. Two main physiological features of osmoregulation, active ion transport through the Na +/K +-ATPase pump and fatty acid composition of membranes affecting permeability to water and ions, cannot fully explain differential survival to an SST. This observation is derived from different experimental models, which include nutritional conditions or normal (genetic) variation. Other traits of the overall physiological condition appear to be involved and are not related to physiological regulation but rather are a result of a possible increased tolerance capacity.

Necrotizing hepatopancreatitis (NHP) infected Penaeus vannamei female broodstock: Effect on reproductive parameters, nauplii and larvae quality

Necrotizing hepatopancreatitis (NHP) is a disease of cultured Penaeus vannamei caused by a gram-negative intracellular bacterium rickettsia-like organism. NHP was first reported in Texas in 1985, as being responsible for mortalities in shrimp ponds in Central and South America. The growth and proliferation of NHP within the hepatopancreatic epithelial cells is associated with anorexia, lethargy, abdominal muscle atrophy, softened exoskeleton, growth retardation and mortalities ranging from 20% to 95%. Although NHP can cause high mortalities in commercial ponds, it has been considered a problem only in broodstock ponds and maturation laboratories due to an increase in broodstock mortalities in Colombia. In order to evaluate additional negative effects at this level, we investigated the effect of NHP infection upon the reproductive behavior of females and the effect of maternal infection on nauplii and larval quality. Broodstock from NHP affected ponds were transferred to a maturation laboratory. After copula, females were transferred to individual spawning tanks. After spawning, females were sacrificed for histopathology and PCR analysis, while the eggs were placed in individual tanks for hatching. Females were classified into three groups according to their histopathological findings: NHP negative ( n = 23) had no NHP lesions, positive for NHP with lesions grade 1 ( n = 20) and NHP positive females with lesions grade 2 ( n = 12). For each group, we analyzed the number of eggs, hatching percentage and number of nauplii per female. Our results show that females with NHP lesions grade 2 presented a significant reduction in the number of eggs and nauplii ( P < 0.05) as compared with NHP negative females and females grade 1 NHP disease. No significant differences were found in hatching percentage among the three groups. Triglyceride levels in nauplii II were significantly higher in NHP negative females than in females with grade 2 NHP ( P < 0.05), whereas there was no difference between NHP negative and grade 1 females. No significant differences were found for glucose and cholesterol levels in nauplii among the three groups. No differences were found in survival at zoea I, mysis I, PL-1 and PL-10 for the three groups. However, after a salinity stress test, the PL-10 survival decreased significantly in larvae from NHP positive females. Also a significant decrease in PL-10 length was also observed in the progeny of these females (grades 1 and 2). This study demonstrated that NHP disease in female shrimp spawners affects both maturation and larviculture causing a decrease in the number of eggs and nauplii per female, a reduction in the levels of triglyceride in nauplii II and decreasing larvae growth and resistance to osmotic stress test at PL-10 stage.

Salinity stress test as a predictor of survival during growout in pacific white shrimp ( Litopenaeus vannamei)

A high survival rate to a salinity stress test applied to 15-day-old shrimp postlarva (P15) is supposed to be associated with improved performance during growout, or at least during pond stocking. However, there is no direct evidence (e.g. correlation) for this association. The present study analyzed survival to a salinity stress for correlation to subsequent performance in 40 larval batches (individual spawns) that were cultured simultaneously under the same conditions, as a predictive criterion of survival during stocking and growout to juvenile stages. We also determined some osmoregulatory capacities (gill area, Na +/K +-ATPase) associated with survival to the salinity stress test. The activity of Na +/K +-ATPase was higher in P15 subjected to lower salinities, but it did not reach significance in batches with higher survival to the salinity stress test. Survival to a stress test was positively correlated to P15 length ( r=0.62; P<0.001). The batches that had higher survival to the stress test also had higher survival during stocking, and a positive correlation was found between survival during stocking and survival to the stress test ( r=0.34; P<0.05). Thus, the salinity stress test applied to P15 was useful for predicting survival during stocking. However, it was not correlated to survival during growout ( r=0.04; P>0.05), or to size of juveniles during growout ( r=0.12; P>0.05), and thus it was not reliable as predictive indicator of performance (survival and growth) during growout under our experimental conditions. To our knowledge, these are the first published results of a relationship between survival to a salinity stress test applied to P15, and subsequent survival during stocking and growout assessed in controlled experiments.

Survival, Na+/K+-ATPase and lipid responses to salinity challenge in fed and starved white pacific shrimp (Litopenaeus vannamei) postlarvae

Fed (3-h starved) and 24-h starved 20-day-old postlarvae (P20) were compared to establish the effect of energy reserves on survival rate at 0 ppt and osmoregulatory mechanisms at 10 ppt. The activity of Na+/K+-ATPase was fivefold higher in posterior gills than anterior gills. The activity of Na+/K+-ATPase increased by 63% in both anterior and posterior gills in shrimp subjected to a salinity challenge. No significant increase in carbonic anhydrase activity was observed in P20 exposed to dilute medium. Starvation did not affect these osmoregulatory responses, although starved P20 had a significantly lower survival rate when exposed to dilute medium of 0 ppt. These results indicate that the lower survival rate from a salinity stress test on starved P20 cannot be fully explained by impairment of the osmoregulatory mechanisms. Total lipids (TL) in the hepatopancreas were significantly lower in starved P20, and triacylglycerides (TG) were slightly but not significantly lower in P20 exposed to 10 ppt. In gills, triacylglycerides were significantly higher in P20 exposed to 10 ppt. These results suggest a mobilization of lipids to satisfy the energy demands of the osmoregulatory response or an increase in metabolism as part of a general stress response.

Criteria for assessing larval and postlarval quality of Pacific white shrimp ( Litopenaeus vannamei, Boone, 1931)

Optimum shrimp larval quality is of primary importance to obtain maximum yields during larval and postlarval culture, as well as during stocking in ponds for further growout. The present study analyzed putative predictive criteria of larval quality at different stages for correlation to subsequent performance. Association of salinity stress test (SST) survival with larval morphological and biochemical characteristics was also analyzed. For these purposes, 36 larval batches (individual spawns) that were cultured simultaneously under the same conditions were evaluated for biochemical and morphological characteristics, and survival from stress tests. The experimental design consisted of two approaches: (1) dividing these batches in low versus high survival during culture or to salinity stress test and comparing variables between both groups and (2) correlation analysis between different variables. Significant correlations were obtained between survival to an ammonia stress test of zoea or “metamorphosis” to zoea and survival from nauplii to 1-day-old postlarvae ( r=0.59 or r=0.73, P<0.01, respectively). In addition, survival from 1- to 15-day-old postlarvae (PL1 to PL15) was correlated to the salinity stress test applied at PL1 ( r=0.42, P<0.05). Thus these criteria were useful for predicting larval and postlarval survival to further stages. However, other possible criteria, such as nauplii and PL1 biochemical and morphometric variables, were not reliable as predictive indicators under our experimental conditions. In addition, several characteristics of PL1, such as gill area, postlarva size, and acylglycerides and their associated fatty acid content were significantly higher ( P<0.05) in batches of PL1 with high survival after a salinity stress test.

Influence of highly unsaturated fatty acids on the responses of white shrimp ( Litopenaeus vannamei) postlarvae to low salinity

Salinity stress tests are commonly applied in shrimp hatcheries to estimate the quality of postlarvae (PL) to be used during growout. Higher larval survival during culture and to a salinity stress test in both fish and crustaceans have been reported when specimens were offered a diet containing high levels of highly unsaturated fatty acids (HUFA). However, it is not clear if increased survival is a result of better overall physiological condition resulting from the diet or a specific effect of HUFA on osmoregulatory mechanisms. This study analyzed if HUFA-rich diets could modify the fatty acid composition of membranes in gills, and if this change in composition could affect the activity of the Na +/K + ATPase pump and carbonic anhydrase in relation to changes in salinity. One-day-old postlarvae (PL1) pooled from different spawns were fed for 20 days with Artemia sp. nauplii enriched with three levels of HUFA: low, medium and high. At PL20, survivals during culture and to salinity stress test (tap water for 30 min) were evaluated. Also at this stage, Na +/K +-ATPase and carbonic anhydrase activity, morphometric variables, and fatty acid composition in the hepatopancreas and gills were measured after they were submitted to a salinity challenge in dilute seawater (10 ppt) for 3 h. No significant differences were observed in survival rates during culture, but survival to a salinity stress test was higher and gill area was larger in PL20 fed the Artemia sp. nauplii enriched with medium HUFA levels, probably as a result of an increased 22:6n-3 content and higher 22:6n-3/20:5n-3 ratio in this diet and in the tissues of the organisms fed this diet. Na +/K +-ATPase specific activity was significantly higher in posterior gills, while the specific activity of the carbonic anhydrase was higher in anterior gills. Enzymatic activities increased significantly in PL20 submitted to a salinity challenge, and HUFA levels in the diet affected both. The proportion of fatty acids in hepatopancreas and gills were significantly affected not only by diet, but also by exposure to dilute media. This effect is discussed in relation to an increase in gill surface and changes in fatty acid composition in the phospholipids present in gill membranes, which can modify the permeability and the activity of the Na +/K +-ATPase pump. The beneficial effect of HUFA supplementation in the diet on survival to salinity stress test is partially related to modification of fatty acid composition of gills and to a larger gill area, which in turn enhances osmoregulatory mechanisms, namely Na +/K +-ATPase and carbonic anhydrase activities.

Egg and larval quality criteria as predictive measures for juvenile production in turbot ( Scophthalmus maximus L.)

Although much effort has been made to evaluate criteria for marine egg and larval quality, the significance of poor egg quality for the results in the final juvenile production has not been clarified. The aim of our experiments with turbot ( Scophthalmus maximus) was to determine whether the initially observed egg quality affected offspring viability and normal development up to the juvenile stage. Eggs from each of six individual females were divided into three replicate groups, and the eggs in each replicate was quality evaluated according to fertilization rates and the ratio of normal cell cleavages (blastomere morphology) at the 8–32 cell stage. The condition of yolk-sac larvae was tested by an acute high salinity stress test, and the larvae were fed according to our standard feeding regime with microalgae, enriched rotifers and Artemia nauplii. Significant positive correlations were found between observed egg quality characteristics and hatching rates, larval tolerance to acute stress, and to survival, metamorphosis and juvenile pigmentation. Larvae hatching from poor quality egg groups thus had a lower viability and were less able to develop normally to the juvenile stage than larvae from good quality egg groups. Our conclusion is that egg quality observed as fertilization rate and rates of normal blastomeres at early egg stages may be a useful predictive tool for evaluation of the potential juvenile production in turbot.

Recent developments and improvements in ornamental fish packaging systems for air transport

Current ornamental ¢sh packaging systems are characterized by very high ¢sh loading densities and high metabolic wastes in the transport water after shipment. They focus mainly on management of the quality of transport water. Recent studies using the guppy as a model ¢sh showed that post-shipment mortality could be reduced through enhancement of the stress resistance of the ¢sh, and hence emphases should also be placed on the preparation of the ¢sh for transport and recovery of the ¢sh after shipment. Farmers can contribute signi¢cantly by applying nutritional prophylaxis before harvesting. Exporters may use the salinity stress test to identify ¢sh lots of good quality for transport, apply health prophylaxis to eradicate parasites and optimize other techniques such as starvation of the ¢sh or addition of salt to the transport water to enhance the stress resistance of the ¢sh. Importers may adopt proper acclimation procedure and allow ¢sh to recover in low salinity water to reduce post-shipment mortality. As the main bulk of post-shipment mortality is stressmediated and occurs during the 1-week recovery period, the industry should consider revising the basis of the current warranty system for their customers, from death on arrival to cumulative mortality at 7 days post shipment (or death after 7 days, DA7), in order to cut down ¢sh losses after shipment.

Optimal dietary levels of lecithin and cholesterol for black tiger prawn Penaeus monodon larvae and postlarvae

The effect of lecithin and cholesterol on growth and survival of larval and postlarval Penaeus monodon was evaluated using semi-purified diets containing four levels of lecithin (0.0, 0.5, 1.0 and 1.5%) and three levels of cholesterol (0.0, 0.5 and 1.0%). Three early stages (zoeal, mysid and postlarval) of P. monodon were fed the experimental diets. Growth and survival of shrimp fed diets containing 1.0 and 1.5% lecithin were not significantly different ( P>0.05) but these groups had significantly greater growth and survival than those fed 0.0 and 0.5% lecithin diets. Shrimp fed diets containing 1.0% cholesterol had significantly greater ( P<0.05) growth and survival than that of shrimp fed diets containing 0.0 and 0.5% cholesterol. There was no interaction between lecithin and cholesterol on growth and survival of P. monodon. During a low salinity stress test, PL-15 shrimp fed diets containing 1.0% cholesterol had significantly greater ( P<0.05) tolerance to low salinity exposure.

Dietary ascorbic acid requirements during the hatchery production of turbot larvae

The effect of high ascorbic acid (AA) levels transferred through enriched live food was evaluated for turbot Scophthalmus maximus larvae in two consecutive feeding experiments. The same feeding strategy was applied to all treatments, except for the AA content of the live food which was manipulated through bioencapsulation with ascorbyl palmitate. This resulted finally in a low, medium and high‐AA treatment. The AA incorporation levels in the turbot larvae (up to 1400 μg AA g DW−1) were correlated with the AA content of the live food administered. However, feeding the high AA concentration resulted in the same values as for the medium treatment, indicating a saturation of the body AA reserves. Under standard culture conditions, no differences in growth nor overall survival could be detected among the different groups, illustrating that the dietary AA requirements of larval turbot are met by non‐enriched live food containing already 500 μg AA g DW−1. The larvae of the high‐AA treatment, however, showed a better pigmentation rate (47 and 32% for experiments 1 and 2, respectively) compared to the other groups (35 and 25%, respectively). Evaluation of the physiological condition applying a salinity stress test revealed an improvement by feeding extra AA, significantly in the medium‐AA treatment. Though not significantly different, cumulative mortalities after challenge with Vibrio anguillarum amounted to 50% for the control v. 40% for the fish fed medium and high‐AA diets, respectively. Moreover, the onset of mortalities in this study was slower (not significantly) for the fish fed the extra AA.

Dietary ascorbic acid requirements during the hatchery production of turbot larvae

The effect of high ascorbic acid (AA) levels transferred through enriched live food was evaluated for turbot Scophthalmus maximus larvae in two consecutive feeding experiments. The same feeding strategy was applied to all treatments, except for the AA content of the live food which was manipulated through bioencapsulation with ascorbyl palmitate. This resulted finally in a low, medium and high-AA treatment. The AA incorporation levels in the turbot larvae (up to 1400 μg AA g DW−1) were correlated with the AA content of the live food administered. However, feeding the high AA concentration resulted in the same values as for the medium treatment, indicating a saturation of the body AA reserves. Under standard culture conditions, no differences in growth nor overall survival could be detected among the different groups, illustrating that the dietary AA requirements of larval turbot are met by non-enriched live food containing already 500 μg AA g DW−1. The larvae of the high-AA treatment, however, showed a better pigmentation rate (47 and 32% for experiments 1 and 2, respectively) compared to the other groups (35 and 25%, respectively). Evaluation of the physiological condition applying a salinity stress test revealed an improvement by feeding extra AA, significantly in the medium-AA treatment. Though not significantly different, cumulative mortalities after challenge with Vibrio anguillarum amounted to 50% for the control v. 40% for the fish fed medium and high-AA diets, respectively. Moreover, the onset of mortalities in this study was slower (not significantly) for the fish fed the extra AA.

Evaluation of vitamin C-enriched Artemia nauplii for larvae of the giant freshwater prawn

The effect of high levels of ascorbic acid (AA) delivered through enriched live food has been verified through the successful culture of larval giant freshwater prawn, Macrobrachium rosenbergii. Two successive feeding trials were set up using a control (550 Μg AA g−1 DW) and two different AA-enrichment levels in Artemia (1300 and 2750 Μg AA g−1 DW). Under standard culture conditions, no differences in growth nor survival could be observed demonstrating that the nutritional requirements are below 550 Μg AA g−1 DW, which is the normal level occurring in freshly-hatched Artemia. However, a significantly positive effect could be demonstrated on the physiological condition of the postlarvae, measured by means of a salinity stress test, when vitamin C-boosted live food was administered. Since the AA levels in the predator larvae are linked with the enrichment levels in the live prey, it may be assumed that a positive influence on stress resistance was caused by feeding vitamin C-enriched Artemia. It is expected that under suboptimal conditions, supplementation of high vitamin C levels might also enhance production characteristics.

Effects of Dietary Fatty Acid Enrichment on Survival, Growth, and Salinity-Stress-Test Performance of Inland Silversides

Abstract Larvae of inland silversides (Menidia beryllina) reared on three dietary levels of highly unsaturated fatty acids (HUFA) (low HUFA, medium HUFA, and high HUFA) showed no differences in survival or growth during a 3-week feeding trial and no differences in survival during a salinity stress test at 75‰. Inland silversides therefore appear to have dietary needs for (n-3) HUFA that are more like those of freshwater fish than marine fish, even though they are found in marine environments.

State of the Art of Asian Seabass Lates calcarifer Larviculture

AbstractInnovative techniques opened new perspectives in the larviculture of the Asian seabass in the 1980s. Induced spawning maximized egg production while sperm preservation reduced the problem of male brood‐stock supply. Studies of biometric characteristics of the fish larvae resulted in improved feeding strategies with live food. This in turn permitted a more rational use of expensive Artemia nauplii. Nutritional enhancement of the highly unsaturated fatty acid (HUFA) composition of the live food resulted in significant improvement of survival and physiological condition of the larvae at metamorphosis. A salinity stress test enabled the evaluation of the larvae's physiological status and estimation of their HUFA‐requirements during the hatchery and pre‐nursery phase.

Does participation on concurrent clinical trials compromise the quality of the data or its timely submission

A 13-day nursery trial was conducted to evaluate the performance of young Litopenaeus vannamei post-larvae (from PL6 to PL18) reared in both biofloc and microalgae-based systems at a stocking density of 67 PLs L−1. The effects of different concentrations of total suspended solids (TSS) on PL performance were also evaluated. One experimental group was reared in a conventional microalgae-based system with daily water exchange and daily addition of microalgae (herein called microalgae treatment). The other two experimental groups were reared using biofloc technology (BFT) with daily dextrose addition and no water exchange, but in the “Biofloc-500” treatment, TSS were maintained at around 500 mg L−1, while in the “Biofloc-700” treatment, TSS were maintained at around 700 mg L−1. Water quality variables remained within the appropriate range for larval culture. In microalgae treatment, ammonia control was likely associated with its assimilation into microalgae biomass and daily water exchange. In biofloc tanks, however, the addition of dextrose stimulated the production of bacterial biomass from ammonia. This system required only 12.9% of the water used by the microalgae treatment since water was not exchanged during the culture. The nursery of young PLs resulted in similar (P > 0.05) performance in all treatments: survival >94%, PL length ∼ 11.5 mm, and PL dry weight ∼ 1.2 mg. In addition, the salinity stress test (>90.0%) was not significantly different among treatments. Our results indicate that BFT can be as effective as the microalgae-based system for the nursery of young L. vannamei post-larvae. We also found that post-larvae performance was similar (P > 0.05) between biofloc treatments, indicating that organisms can tolerate environments with large quantities of solids.