Effects of temperature and salinity on oxygen consumption and ammonia excretion of juvenile miiuy croaker, <Emphasis Type="Italic">Miichthys miiuy</Emphasis> (Basilewsky)

The metabolic responses of the juvenile Miichthys miiuy in terms of oxygen consumption and ammonia excretion to changes in temperature (6–25°C) and salinity (16–31 ppt) were investigated. At a constant salinity of 26 ppt, the oxygen consumption rate (OCR) of the fish increased with an increase in temperature and ranged between 133.38 and 594.96 μg O₂ h⁻¹ g⁻¹ DW. The effect of temperature on OCR was significant (P < 0.01). Q₁₀ coefficients were 6.80, 1.41, 1.29 and 2.36 at temperatures of 6–10, 10–15, 15–20 and 20–25°C, respectively, suggesting that the juveniles of M. miiuy will be well adapted to the field temperature in the summer, but not in the winter. The ammonium excretion rates (AER) of the fish were also affected significantly by temperature (P < 0.01). The O:N ratio at temperatures of 6, 10, 15 and 20°C ranged from 13.12 to 20.91, which was indicative of a protein-dominated metabolism, whereas the O:N at a temperature of 25°C was 51.37, suggesting that protein-lipids were used as an energy substrate. At a constant temperature of 15°C, the OCRs of the fish ranged between 334.14 (at 31 ppt) and 409.68 (at 16 ppt) μg O₂ h⁻¹ g⁻¹ DW. No significant differences were observed in the OCR and AER of the juveniles between salinities of 26 and 31 ppt (P > 0.05). The OCR and AER at 16 ppt were, however, significantly higher than those at 26 and 31 ppt (P < 0.05), indicating salinity lower than 16 ppt is presumably stressful to M. miiuy juveniles.     

Rearing of the Pacific white shrimp,Litopenaeus vannamei in a biofloc system: The effects of different food sources and salinity levels

The present study assessed the effects of different types of feeds and salinity levels on water quality, growth performance, survival rate and body composition of the Pacific white shrimp, Litopenaeus vannamei, juveniles in a biofloc system. Shrimp juveniles (2.56 ± 0.33 g) were cultured for 35 days in 300 L fibreglass tanks (water volume of 180 L) with a density of 1 g/L in six treatments. Three sources of feed (100% formulated feed, mixture of 66.6% formulated diet and 33.3% wet biofloc, and 100% wet biofloc) and two levels of salinity (10 and 32 ppt) were considered in two control groups and four biofloc treatments. Water quality parameters in the biofloc treatments were significantly better than control groups (p < .05). The highest increase in growth performance and survival rate were obtained in salinity of 32 ppt and mixed feed sources. Analysing the proximate composition of body shrimp indicates an increase in lipid and ash levels in biofloc treatments, which was more evident in the salinity of 32 ppt. In addition, the proximate analysis of shrimp body showed significant differences between biofloc treatments and control groups (p < .05). The highest FCR was found in the treatment with salinity level of 10 ppt and fed only with floc. Overall, it was found that the artificial diet supplemented with biofloc at the salinity of 32 showed better performance in the juvenile stage of Pacific white shrimp.     

Impact of salinity changes on growth,oxygen consumption and expression pattern of selected candidate genes in the orange mud crab (Scylla olivacea)

Change in environmental salinity level is a major limiting factor for the aquaculture productivity because it imposes severe stress on organisms that in turn retards growth. The orange mud crab (Scylla olivacea) is an important coastal aquaculture species (farming is practised in 10‰–20‰ salinity levels) in Bangladesh. The present study was conducted to investigate the changes in growth, O₂ consumption and mRNA expression levels of five selected genes in the orange mud crab (S. olivacea) exposed to three different experimental salinity levels (0‰, 10‰ and 20‰) for three months. Crabs reared at 10‰ and 20‰, showed significantly higher (p < .05) growth performance and expression of growth regulatory genes (Actin and α‐amylase). The highest levels (p < .05) of O₂ consumption and expression of ion regulatory genes (Na⁺‐K⁺‐ATPase, V‐type H⁺‐ATPase and Diuretic Hormone) were obtained at 0‰. Moderate levels of growth and expression of selected candidate genes were observed at 10‰ treatment while the highest levels of growth and gene expression were obtained at 20‰ (control salinity). Strong interactions were observed between growth performance and expression of growth genes (R² = 0.81–0.91), and rate of O₂ consumption and expression of ion regulatory genes (R² = 0.83–0.93), implying that the selected genes are important candidates for growth and ionic balance in S. olivacea. Growth performance was found to be very low at 0‰ initially, after 30 days crabs showed better growth performance at this salinity level. It is thus inferred that orange mud crab individuals might require 3–5 days for acclimation to salinity stress but it can take at least 30 days for acclimation to regular growth. Results indicate that with proper acclimation, the orange mud crab (Scylla olivacea) can be farmed at low salinity conditions and possibly in freshwater condition.     

Acute Toxicity of Ammonia and Nitrite to Sea Bream,Sparus aurata (Linnaeus, 1758), in Relation to Salinity

Sea bream, Sparus aurata, is one of the most important fish species that is commonly cultured in the Mediterranean and the eastern coasts of the Atlantic Ocean. The life cycle of sea bream in its natural habitat passes through hyposaline and hypersaline lagoons. It is important to determine the tolerance of the fish to nitrogenous compounds for aquaculture at maximum stocking densities. In the present study, a series of acute experiments were performed to evaluate the effect of salinity on ammonia and nitrite toxicity to sea bream. The fish were exposed to different ammonia and nitrite concentrations according to the static renewal methodology at three different salinities (10, 20, and 30 ppt) and at a temperature of 20 C and a pH of 8.2. The toxic effect of total ammonia nitrogen (TAN) and nitrite nitrogen (NO₂‐N) decreased with increasing salinity levels (P < 0.001). Acute toxicity (96‐h lethal concentration 50 [LC₅₀]) values of TAN were determined to be 5.93, 11.72, and 19.38 mg/L at 10, 20, and 30 ppt salinity, respectively. The 96‐h LC₅₀ values of NO₂‐N were determined to be 370.80, 619.47, and 806.33 mg/L at 10, 20, and 30 ppt salinity, respectively. Results indicate that sea bream is less tolerant to ammonia but more tolerant to nitrite compared with some other fish species.     

Effect of salinity at constant 10 °C on grow-out of anadromous Arctic charr from Labrador

The goal is to determine the requirements allowing cultured Salvelinus alpinus to thrive in seawater, as they do in the wild. In late-June, eight families of individually identified 1+ year-old charr (mean wt: 427 g) of a domesticated strain derived from the Fraser River population were directly transferred from freshwater (9 °C) to salinities of either 0, 10, 20 and 30 ppt at 10 °C, then on-grown in tanks until December. Cumulative mortality was 16% in 30 ppt salinity, and < 4% in the lower salinities. Repeated measures analysis revealed somatic growth was inhibited by both elevated salinity and sexual maturation. Among immature fish, final mean weight and condition factor in 30 ppt salinity was 490 g and 1.2, compared to nearly 1 kg and > 1.7 in 0 and 10 ppt. In 20 ppt salinity, growth was initially similar to that in ≤ 10 ppt salinity but deteriorated from September onwards. Sexually maturing fish in ≤ 10 ppt salinity attained a final mean weight about 35% less than immatures. Plasma osmolality was only slightly elevated in the 30 ppt salinity, remaining < 340 mOsm kg^− 1. Food intake and conversion were affected by the interaction between salinity and time, being optimum in 0 and 10 ppt treatments. Family effects on final body size were large, but the effect of salinity on growth was independent of family. In conclusion, despite their large body size, direct transfer of this strain from freshwater to seawater does not appear viable for commercial aquaculture.     

Effects of Nitrite Exposure on Growth and Survival of Sea Bass,Lates calcarifer,Fingerlings in Various Salinities

Sea bass, Lates calcarifer, fingerlings were acclimated to 0. 15, and 32 ppt, and the toxic effects of nitrite exposure were assessed. The 96-hour median lethal concentrations (96-hour LC₅₀ for nitrite were estimated to be 14.5 mg/L at 0 ppt, 105 mg/L at 15 ppt and 93 mg/L at 32 ppt salinity. Chronic exposure to a nitrite concentration equivalent to 10% of the respective 96 hour LC₅₀ resulted in marked growth reduction: growth being reduced in the order of 0 ppt > 32 ppt > 15 ppt. In nitrite-free water, growth rate for fish raised at a salinity of 15 ppt was higher compared to fish raised at salinities of 0 ppt and 32 ppt, a phenomenon which probably reflected the advantage of a reduction in osmoregulatory work in an iso-osmotic environment.     

Biochemical impacts of salinity on the catfish,Heteropneustes fossilis (Bloch, 1794), and possibility of their farming at low saline water

Although a stenohaline freshwater fish, the stinging catfish Heteropneustes fossilis, is also available in the freshwater fringes of the coastal areas of Bangladesh, the tolerance of this species to variable environmental salinity has not been thoroughly investigated. Based on median lethal salinity (MLS‐50 96 h), three sublethal salinity levels (3 ppt, 6 ppt and 9 ppt) and a control (0 ppt), each with three replications were selected to observe the effects of mildly brackish conditions on the fish for a period of 90‐day exposure. Better growth and survival were found up to 6 ppt compared with control. Salinity more than 6 ppt appeared unsuitable for H. fossilis fingerling due to increased mortality and reduced growth. To determine biochemical alterations, a few important physiological parameters were observed after 90 days of exposure. Glycogen level of liver and muscle in the fish reared at 9 ppt salinity decreased significantly (P < 0.05) as compared to the control. Glucose level in blood and liver was also found to be increased in fish with increase in salinity. ALP and ATPase activities were reduced significantly in both muscle and liver tissues at higher salinity, indicating the stress mitigation effect. However, all the biochemical parameters were found in normal condition up to 6 ppt compared with control. This evidence suggests that H. fossilis can sustain and grow well below 6 ppt and can be a potential candidate for culture in coastal areas after heavy downpour when the salinities level falls to 6 ppt or lower.     

Relationship of RNA/DNA ratio to somatic growth of Nile tilapia juveniles (Oreochromis niloticus) under joint effects of temperature and salinity

Tilapia juveniles are a very important life stage, and reliably assessing their growth performance is of prime importance in aquaculture production. The suitability of the RNA/DNA as a bioindicator for growth evaluation in tilapia has not yet been reported. In this study, we examined suitability of RNA/DNA ratio for assessing growth of tilapia juveniles and variation in the ratio under the concurrent influences of temperature and salinity using the central composite design and response surface methodology. Results showed that under our experimental conditions, the synergistic effects of temperature and salinity on the RNA/DNA ratio were highly significant (P < 0.01), and the ratio varied with the two factors in a nonlinear fashion; the temperature × salinity interaction was detected at 1% significance level, and had a negative effect on the RNA/DNA ratio particularly at higher temperatures. Temperature was found to have a greater influence on RNA/DNA ratios than salinity. A model of the relation between RNA/DNA, temperature and salinity was developed, with an R² greater than 98%. The linear relationships of absolute growth, cumulative growth and specific growth of tilapia juveniles to RNA/DNA ratio all showed an R² of greater than 95%. Our results indicate that the RNA/DNA ratio was a responsive and accurate bioindicator for evaluating the growth performance of juvenile tilapia. These ratio‐based models are neither temperature‐ nor salinity‐dependent, and could be readily applicable to freshwater or brackish water aquaculture within temperature–salinity combinations ranging from 16 to 36°C and 0–16 ppt.     

Tetrodotoxin accumulation conflicts with low salinity tolerance in juvenile tiger puffer Takifugu rubripes

We evaluated whether bearing tetrodotoxin (TTX) affects salinity stress in the juvenile tiger puffer Takifugu rubripes. Juveniles of hatchery-reared non-toxic T. rubripes [body weight (BW): 1.7?±?0.2 g, n?=?120] were divided into six tanks and acclimatized to salinity (8.5 ppt) that is equivalent to blood osmolality. Fish in three tanks were fed non-toxic diet, and those in the other three tanks were fed a TTX-containing diet (356 ng/g diet) three times a day until satiation. In each diet treatment, salinity of one tank was kept at 8.5 ppt, and the other two tanks were adjusted to either 1.7 or 34.0 ppt, and fish were reared for another 33 days. Then, we compared survival, growth, TTX accumulation, plasma osmolality, plasma cortisol, and glucose levels among treatments. We detected TTX only in the fish in the TTX-diet groups. Survival was highest at 8.5 ppt (70%) and lowest at 1.7 ppt in the TTX-diet group (20%). The BW was greater at 8.5 ppt, and plasma osmolality was significantly higher at 34.0 ppt than at any other salinities. Plasma cortisol level was significantly higher but glucose level was lower at 1.7 ppt. Possessing TTX at a low salinity may be lethal to tiger puffer juveniles.

     

Physiological characteristics and stress resistance of great sturgeon (<Emphasis Type="Italic">Huso huso</Emphasis>) juveniles fed with vitamins C,E, and HUFA-enriched <Emphasis Type="Italic">Artemia urmiana</Emphasis> nauplii

This study was carried out to examine the effect of Artemia urmiana nauplii enriched with HUFA, and vitamins C and E on stress tolerance, hematocrit, and biochemical parameters of great sturgeon, Huso huso juveniles. Cod liver oil (EPA 18% and DHA 12%), ascorbyl-6-palmitate and α-tocopherol acetate were used as lipid, and vitamin C and E sources, respectively. Beluga juveniles at the stage of first feeding (69.7 ± 5.9 mg body weight) were randomly divided into five treatments and three tanks were assigned to each diet. All fish groups were fed non-enriched Artemia for the initial 5 days and then fed enriched Artemia for 7 days. Juveniles were fed with Artemia enriched with HUFA + 20% vitamin C (C group); HUFA + 20% vitamin E-enriched Artemia nauplii (E group); HUFA + 20% vitamin C + 20% vitamin E (C and E group); HUFA without vitamins (HUFA) and non-enriched Artemia (control). After the period of enrichment, Juveniles were fed with Daphnia sp. from the 13th to the 40th day. At day 40, the fish were transferred directly from fresh water (0.5 ppt) to brackish water (6 ppt for 4 days and 12 ppt for 2 days) and warm water (from 27 to 33°C) to evaluate juvenile resistance to salinity and thermal shocks. Moreover, all treatments were separately exposed to freshwater in tanks with the same capacity as used for osmotic and thermal tests (as fresh water control). The addition of vitamins C, E, and C + E to HUFA significantly increased fish resistance to 12 ppt salinity and temperature stress tests, whereas survival was not significantly different among challenges at 6 ppt. There was no significant difference in the hematocrit index under stress conditions. Enrichment had significant influence on plasma Na⁺ level in the C group on the 4th day at 6 ppt. Na⁺ and Ca²⁺ concentrations in C, E, and C and E groups on the 1st day at 12 ppt, and Ca²⁺ level in E group on the 2nd day at 12 ppt were lower than the other groups. The glucose level in the C and C and E groups was lower than the other treatments on the 1st day at 12 ppt and the 2nd day at 33°C. Regardless of Artemia enrichment, plasma ions (Na⁺, K⁺, Ca²⁺, and Mg²⁺) and glucose concentrations in fish exposed to salinity stress tests were higher than fish in fresh water. Glucose concentration in plasma also increased after 2 days at 33°C. Although most of our results were not significantly different, the use of vitamins C, E, and HUFA in Artemia enrichment can improve Juveniles tolerance under stress conditions, and regardless of enrichment, these data show that beluga juveniles are partly sensitive to high salinity and temperature.     

Combined effects of temperature and salinity on yolk utilization in Nile tilapia (Oreochromis niloticus)

The combined effects of temperature and salinity on the yolk utilization of sac fry in Nile tilapia (Oreochromis niloticus) were investigated using central composite experimental design and response surface approach. Based on the preliminary trials, temperature was determined to range from 22 to 34°C, and salinity ranging from 2 ppt to 10 ppt. The utilization was mensurated in terms of yolk sac volume. Results showed that the linear effects of temperature and salinity on the yolk utilization was significant (P < 0.01); the quadratic effects of and the interaction between the two factors were significant (P < 0.05); temperature was more important than salinity in influencing the yolk utilization. The model equation of yolk sac volume towards temperature and salinity was established. From those high R² values, the model had excellent goodness of fit to experimental data and could be applied for predictive purpose. What with the production cost, it is suggested that the temperature/salinity combination, i.e. 28–30°C/4–6 ppt, be employed during the period of sac fry rearing, in which the yolk utilization was on average 98.6%.     

Influence of water salinity on the survival of embryos and growth of the sichel larvae Pelecus cultratus (L.) under controlled conditions

The purpose of this study was to analyse the influence of water salinity on the incubation of eggs and growth of the larvae of sichel Pelecus cultratus (L.) under controlled conditions. The following water salinity was considered: 3, 6, 9, 12, 15 and 0 ppt for the control. The eggs incubation time depended on the water salinity, lasting from 56.3°D [9 ppt] to 107.7°D [0 ppt]. The higher water salinity, shorter the incubation time. The highest survivability of larvae was obtained in water of the salinity equal 3 ppt and in freshwater, where respectively 87% and 84% of the larvae survived. No hatched larvae were obtained in water of the salinity of 12 and 15 ppt, as all embryos died during the experiment. Larvae were reared up for 21 days. The final body weight, depending on the water salinity, reached from 43.5 mg [9 ppt] to 74.6 mg [3 ppt], at the respective body lengths of 19.3 mm and 23.2 mm. The highest body gains and lengths of larvae were observed in water of the salinity of 3 ppt. The lowest survivability of sichel larvae occurred in water of the salinity 9 ppt, where it was only 53.2%. The survivability of larvae in freshwater and water of the salinity of 3 ppt was quite similar: 96.2% and 95.6% respectively. Water salinity degree of 12 and 15 ppt appeared to be lethal for both embryos and larvae of the sichel.     

Effect of low salinity on the expression profile of Na+/K+‐ATPase and the growth of juvenile chub mackerel (Scomber japonicus Houttuyn)

Chub mackerel (Scomber japonicus Houttuyn) is one of the most commercially important scombroid fish used as a food resource. Recently, there has been a demand for efficient rearing methods of this fish for a full‐life cycle aquaculture. In the present study, we evaluated the physiological responses in the juvenile S. japonicus to different ambient salinities. A significantly higher gain of the body mass was observed in the juveniles reared in 24 g/L and 13 g/L seawater than in those reared in natural seawater (34 g/L) within 40 days of the experimental period without affecting mortality. A principal enzyme for osmoregulation, Na⁺/K⁺‐ATPase, was expressed in the ionocytes located in the gill filaments of the juveniles. The number and the cell size of ionocytes and the enzymatic activity of Na⁺/K⁺‐ATPase in the gills decreased within 10 days after the low‐salinity challenge, which implies the reduction of the energy‐consuming active ion secretion under the low‐salinity environment. The physiological capacity for adaptation to low‐salinity seawater in chub mackerel could be basic knowledge to carry out culturing of these fish in coastal sea pens where ambient salinity fluctuates. The improvement of the growth performance by rearing in low‐salinity seawater will contribute to the efficient production of the seed juveniles for aquaculture.     

Temperature and Salinity Tolerances of the Tropical Spiny Lobster,Panulirus ornatus

Interest in the development of aquaculture of the tropical spiny lobster, Panulirus ornatus, has increased markedly over the past 10 yr because of strong market demand and high prices. In Australia, economic conditions will necessitate that a semi‐intensive approach be taken, possibly involving managed environmental conditions. Identification of optimal temperature and salinity levels will be necessary, and therefore two experiments were performed to examine these two parameters. Juvenile lobsters were grown in tanks at five temperatures (19, 22, 25, 28 and 31 C). Growth was significantly affected by temperature (P < 0.01), and maximal growth occurred at 25–31 C. Examination of the temperature effect on molt increment and intermolt period indicated that 27 C was the optimal temperature, at which molt increment was greatest and intermolt period the least. Temperature also had a significant (P < 0.01) positive effect on apparent feed intake (AFI). Juvenile lobsters were also exposed to four different salinities (20, 25, 30 and 35 ppt) over a period of 91 d. Significant differences (P < 0.01) were apparent for both survival and growth. Lowest survival occurred at 35 ppt which may be attributable to higher cannibalism at that salinity. Growth was highest at 35 ppt and progressively less at lower salinities. Although full marine salinity (35 ppt) will generate best performance of P. ornatus, its capacity to tolerate reduced salinity will provide greater opportunity to develop commercial aquaculture.     

Effect of salinity and temperature on salinity tolerance of the sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis>

Sea cucumber Apostichopus japonicus juveniles acclimated to different environmental conditions (23, 25, and 27°C combined with 25, 30, and 35 psu) were assessed for tolerance to increasing and decreasing levels of salinity at a rate of 2 psu h⁻¹. They were also tested for the LS₅₀ (median lethal salinity) when transferred directly into a series of higher salinity (32–46 psu) and lower salinity (9–25 psu). The CSMax (critical salinity maximum), CSMin (critical salinity minimum), USTL (upper salinity tolerance limit), and LSTL (lower salinity tolerance limit) were positively correlated to the acclimated salinity level but negatively correlated to temperature. The CSMax of A. japonicus was 6.2–10.0 psu higher than the USTL, and the CSMin was 5.5–8.5 psu lower than the LSTL, indicating that gradual changes in salinity resulted in the wide range of salinity tolerance that was observed, but that abrupt changes in salinity resulted in the narrow range of tolerance. Two-way analysis of variance revealed that salinity and temperature had a significant effect on 50% CSMax, 50% CSMin, USTL, and LSTL (P < 0.001). The information obtained in this study will be valuable for the further development of the sea cucumber aquaculture industry in China.     

Effects of salinity acclimation on the growth performance,osmoregulation and energy metabolism of the oriental river prawn,Macrobrachium nipponense (De Haan)

In this study, we evaluated the growth, osmoregulation and energy metabolism of the oriental river prawn, Macrobrachium nipponense, reared during 6 weeks with different salinities (0, 8, 14 and 22 g/L). The results showed that the haemolymph osmolality of M. nipponense increased with an increase in ambient osmotic pressure; the isosmotic point was 490 mOs/kg H₂O. The prawns showed a higher survival rate, weight gain rate and hepatopancreas index in salinity 14 g/L. Digestive enzymes were all affected by salinity, and the highest activities were observed in the salinity 14 g/L. The mRNA expression of Na⁺‐K⁺‐ATPase in gills and p53 in hepatopancreas were the highest in salinity 22 g/L. The expressions of heat shock protein 90 and glutathione S‐transferase genes in hepatopancreas were significantly higher in the salinity 8 g/L. Lipid metabolism‐related genes in hepatopancreas were significantly expressed in the salinity 14 g/L. The glucose‐6‐phosphatase gene in hepatopancreas was highly expressed in the salinity 8 and 22 g/L, and the expression of the ecdysone receptor gene in hepatopancreas was significantly higher in the salinity 14 g/L. The results showed that salinity 14 g/L could promote the growth of M. nipponense. However, higher salinity conditions may cause physiological damage, which provides a theoretical basis for brackish water culture of M. nipponense.     

Effects of Salinity on Biogenic Amines,Hemolymph Osmotic Pressure,and Activity of Gill’s Na+/K+‐ATPase in Charybdis japonica (Crustacea,Decapoda)

The effects of salinity on hemolymph osmotic pressure, gill Na⁺/K⁺‐ATPase activity and dopamine (DA), norepinephrine (NE), serotonin (5‐HT) in the gills, and hemolymph of the adult Charybdis japonica were studied. DA levels increased significantly (P < 0.05), while the NE and 5‐HT revealed contrary change in hemolymph and gills. The iso‐osmotic point of C. japonica (911.4 mOsm/kg) was at salinity of 27.87 ppt. The Na⁺/K⁺‐ATPase activity of gill showed negative correlation with salinity in the hypotonic environment (<27.87 ppt). The results of this experiment indicated that C. japonica had great capability to acclimate to low salinity.     

Effects of different salinities on amino acid profile in Artemia franciscana

The effects of different salinity levels, including 10–15, 30–35, 70–75, 110–115 and 150–155 ppt, were evaluated on survival and the body amino acids (BAA) of Artemia franciscana. The results were expressed as total essential (TE), non‐essential (NE) and total amino acids (TAA); also, the ratio of the TE to NE (ENAA) on days 3 and 13 of the culture is reported. The study of changes in Artemia BAA showed that with the increase in the water salinity, the TE, NE and TAA increased significantly on days 3 and 13 of the culture. However, the highest ratio of ENAA was observed in the 110 gL^?1 salinity treatment on day 3 (1.067 ± 1.25). Regarding the effects of different salinity treatments on the survival rate of Artemia, it was observed that, generally, an increase in the water salinity would reduce the survival rate of this species. This reduction was observed on day 3 of culture in the salinity treatments above 120 (66.66 ± 1.68%) and below 30 gL^?1 (89.66 ± 0.34%) and on day 13 of culture in the salinity treatments below 30 (11.86 ± 0.13%) and above 70 gL^?1. Basically, it can be concluded that A. franciscana culture at a salinity of 110 gL^?1 can lead to the biological enrichment of Artemia in terms of amino acid profile.     

Efficacy of a pilot-scale wastewater treatment plant upon a commercial aquaculture effluent: I. Solids and carbonaceous compounds

A pilot-scale wastewater treatment station was built and operated at a commercial recirculating aquaculture facility in order to initiate, characterize and optimize the operation of a treatment strategy for effluent recovery and reuse. The treatment train consisted of sedimentation, denitrification, ozonation, trickling filter treatment, and chemical flocculation. The study consisted of four different sets of treatment conditions, differentiated by alternative use of 6 or 4 lpm flow and recycling rates, ozone doses between 36.6 and 82.5 mg O₃/l water, and 6- or 9-min ozonation time. The effects of treatment on solids and dissolved organic compounds are reported here. Over 70% of solids were removed by sedimentation under all experimental conditions. At the end of treatment, up to 99% of TSS was removed due to the combined action of ozonation and chemical flocculation. COD removal was not significantly different among experimental conditions by sedimentation (59.2–62.7%, p > 0.05), but was positively correlated with ozone dose (slope = 0.452, r² = 0.99), yielding total COD removal η(CODt) of 19.8–40.7%. Of these amounts, 60.4–66.5% of COD was removed with foam, while the balance was mineralized. The ozone reactivity was 83.7% at a dose of 82.5 mg O₃/l water. The ozone consumption coefficient Y(O₃/CODox) for COD oxidized was 1.92–2.23 g/g O₃ COD and 0.70–0.78 g O₃/g COD when total COD removed was considered. Overall, 87.9–92.4% of COD was removed by the treatment train, to an average of 44 mg/l at the highest ozone dose, a value 3.3–3.9 times less than in fish tanks. Under the same conditions, cBOD₅ was reduced by 88%, 3.8–4.1 times less than in fish tanks. The water’s biodegradability was increased by over 20%. DOC did not change significantly through the treatment train, and fluctuated through the system due to methanol addition to support denitrification. Work with the pilot station showed that the treatment strategy employed could support effective recovery and recycling of aquaculture effluent, although salts and refractory organics may accumulate in the system.     

Growth and potential purification ability of Nitzschia sp. benthic diatoms in sea cucumber aquaculture wastewater

The growth patterns and water treatment capacity of Nitzschia sp. benthic diatoms in different concentrations of sea cucumber aquaculture wastewater (0%, 10%, 30%, 50%, 80% and 100%) and f/2 medium were studied. Nitzschia sp. grew in different concentrations of aquaculture wastewater and showed remarkable differences in their rate of growth among the treatment groups. Nitzschia sp. grew most quickly (0.83 ind/day) and showed the greatest total chlorophyll‐a content in 30% wastewater. The total chlorophyll‐a content and growth rate of Nitzschia sp. were strongly correlated (R² > 0.98). The total lipid (TL), total protein, exopolysaccharide (EPS) and intracellular polysaccharide (IPS) contents of the diatoms were highest in 100% wastewater and showed significant differences among the experimental groups (p < 0.05). Total nitrogen (TN), ammonium‐nitrogen (NH₄‐N) (AN), nitrate nitrogen (NO₃‐N) (NN), nitrite nitrogen (NO₂‐N) (NIN) and total phosphate (TP) contents were significantly reduced after cultivation. TN uptake peaked at 54.58% in 30% wastewater. AN uptake exceeded 95% in 30% wastewater and 100% wastewater. NN uptake peaked at 56.42% in 80% wastewater, whereas TP uptake ranged from 16.80% to 27.69%. These results suggest that Nitzschia sp. biomass can be enhanced via cultivation in low‐concentration (30%) wastewater, after which their cultivation may be continued in high‐concentration (100%) wastewater, increasing their nutritional value and aiding in the removal of surplus nitrogen and phosphorus in sea cucumber aquaculture wastewater. Application of Nitzschia sp. using the recirculating wastewater‐treatment methods described has the potential to reduce environmental harm caused by sea cucumber cultivation and thus achieve sustainable aquaculture.