Tissue distribution and depletion of sarafloxacin hydrochloride after in feed administration in gilthead seabream (Sparus aurata L.)

Tissue distribution and depletion of sarafloxacin was studied in gilthead seabream, under experimental field conditions at 25 and 18 °C, after in-feed administration of sarafloxacin hydrochloride for 5 days (10 mg/kg body weight/day). Ten fish per sampling point were examined during and after treatment. Muscle plus skin (n=10), liver, kidney and vertebra (pooled) were collected and analyzed by HPLC. Sarafloxacin concentrations in these tissues increased during the medication period, and then decreased rapidly. The highest sarafloxacin concentrations were recorded in liver (335.2 and 49.8 μg/g at 25 and 18 °C, respectively). In muscle plus skin, sarafloxacin concentrations were 193.0 and 42.0 μg/kg at 25 and 18 °C, respectively. Sarafloxacin residues were eliminated rapidly; at 36 h post treatment, the levels in muscle plus skin were 10.2 and 8.5 μg/kg at 25 and 18 °C, respectively. Elimination half-lives (t_1/2) were 17.8 and 32.5 h at 25 and 18 °C, respectively. Withdrawal period for the Maximum Residue Limit (MRL) of 30 μg/kg sarafloxacin in muscle plus skin (95% tolerance limit) at 25 °C was 42.2 h. The slow elimination from vertebra, relative to other tissues, suggests that vertebra behaves as a reservoir in gilthead seabream.     

Determining the optimum doses of Kurasan (ethoxiquinolin) and butylhydroxytoluol (BHT) in dry pellets: effect of both anti-oxidants on some haematological and condition parameters of rainbow trout, Salmo gairdneri Richardson

Abstract. Kurasan and BHT were tested at doses of 100, 200 and 400mg kg^-1 incorporated in dry pellets. The administration of these antioxidants did not influence the red blood count of rainbow trout, Salmo gairdneri Richardson, at body weights of 100 to 400g, reared in flow-through tanks at water temperatures of 7 to 13°C and in cage culture at water temperatures of 15 to 2O°C. In laboratory experiments at a water temperature of 14°C, the highest Kurasan dose increased the red blood cell (RBC) count insignificantly by 14% (1.06 vs 0.93 10¹²1^-1) after 80 days, haematocrit (PCV) was increased by 27% (0.410 vs 0.32511^-1), and haemoglobin (Hb) by 16% (72 vs 62gl^-1), This was seen in the cage culture experiment, but not in the experiments in the flow-through tanks. A trend of diminishing haematological parameters of the red blood count and total blood serum protein (TP) of the fish fed with BHT-stabilized diet was recorded only under laboratory conditions at the water temperature 9°C, The decline of RBC count in the experimental group with 0.04% BHT represented 14% (0.90 vs 1.05 10¹²1^-1), the decline in PCV amounted to 18% (0.328 vs 0.39811^-1), Hb to 17% (57 vs 69g 1^-1), and TP to 11% (39 vs 44g 1^-1).     

Biochemical parameters of blood plasma and content of microcystins in tissues of common carp (Cyprinus carpio L.) from a hypertrophic pond with cyanobacterial water bloom

The aim of this study was to evaluate the dynamics of the blood plasma parameters and the content of microcystins in the tissues of common carp ( Cyprinus carpio L.) in relation to the toxic cyanobacterial water bloom. Fish (average body mass 2176±697 g) in the hypertrophic pond were exposed to natural water bloom (dominated by Planktothrix agardhii, Pseudanabaena limnetica and Limnothrix redekei ), which contained microcystins (concentration in biomass 20–181 μg g⁻¹ dry wt, concentration in water 0.3–9.5 μg L⁻¹). Biochemical parameters in fish blood plasma were analysed in 89 fish at 14-day intervals during the whole season (nine sampling periods). Our results demonstrated high variability and fluctuations in the investigated parameters. The content of microcystins and density of cyanobacterial cells correlated with some haematological indices as lipase, alanine–aminotransferase, albumin, magnesium and chlorides. The concentrations of microcystins in the muscle and liver of the fish (determined by high-performance liquid chromatography with mass spectrometer) were below the limit of detection during the monitored period [0.31 ng g⁻¹ fresh weight (f.w.) for the liver and 0.13 ng g⁻¹ f.w. for muscle]. Our study demonstrates that although known cyanobacterial toxin microcystins were not detected in the fish tissues, several biochemical parameters important for the fish physiology were modulated by natural cyanobacterial bloom.     

The susceptibility of salmonid fish to an atypical strain of Aeromonas salmonicida that infects goldfish, Carassius auratus (L.), in Australia

Abstract. An enzootic, Australian, atypical strain of Aeromonas salmonicida isolated from diseased goldfish, Carassius auratus (L.), was inoculated into Atlantic salmon, Salmo salar L., brown trout, S. trutta L., rainbow trout, S. gairdneri Richardson, and brook trout, Salvelinus fontinalis (Mitchill), fingerlings by intraperitoneal injection (i.p.) and by bath challenge, the latter with and without prior abrasion of skin. The 10-day LD₅₀ (i.p.) was estimated to be 7·4 × 10^-3 colony forming units (cfu) for Atlantic salmon, 3·0 × 10^-2 cfu for brown trout, 3·7 × 10² cfu for brook trout and 6·4 × 10³ cfu for rainbow trout. Brown, rainbow and brook trout succumbed to bath challenges with between 10⁵–10⁶ cfu/ml, developing ulcers of the skin and septicaemia. The organism was trasmitted from inoculated fish to five of 195 within-tank control fish via water and established a carrier state in one of 14 Atlantic salmon. It was concluded that the organism poses a significant threat to the salmonid farming industry and wild salmonid fisheries in Australia.     

Effect of dietary lipid level on muscle composition in Atlantic salmon Salmo salar

This study was conducted to determine the effects of feeding increasing lipid concentrations (310, 380 and 470 g kg^–1 lipid on dry weight) in diets based mainly on herring byproducts to Atlantic salmon Salmo salar . The diets were isonitrogenous, varying in dietary lipid content at the expense dietary starch. Average fish weight increased from 1.2 kg in April to 2.2–2.7 kg at the end of the feeding trial in September. Significantly greater growth was found in fish fed either the 380 g kg⁻¹ or the 470 g kg⁻¹ lipid diets compared with the 310 g kg⁻¹ lipid diet. Muscle lipid content increased in all dietary groups on a wet weight basis from 7.7 ± 1.4% to 12 ± 3% in salmon fed the 310 g kg⁻¹ lipid diet, and to 16 ± 2% in salmon fed the 380 g kg⁻¹ and 470 g kg⁻¹ lipid diets. In fish of similar weight there was a positive correlation between dietary lipid and muscle lipid concentrations. Low concentrations of muscle glycogen were detected in fish fed each of the diets, while muscle vitamin E concentrations slowly decreased as muscle lipid increased. Muscle fatty acid composition reflected dietary fatty acid profiles, containing similar percentages of total saturated, monoenic and n-3 fatty acids (20:5n-3 and 22:6n-3) in fish from all dietary treatment groups. However, a higher ratio of n-3/n-6 was found in muscle from fish fed the 470 g kg⁻¹ lipid diet compared with the other two groups. Blood chemistry values varied somewhat, but all values were within normal ranges for Atlantic salmon of these sizes.     

Pharmacokinetics of oxolinic acid in gilthead sea bream, Sparus aurata L.

This is the first study on the pharmacokinetic parameters of oxolinic acid (OA) in gilthead sea bream, Sparus aurata L. The kinetic profile of OA was studied after a single intravascular injection (20 mg kg⁻¹) in 100 g fish at 20 °C. The distribution half-life ( t _1/2α) and the elimination half-life ( t _1/2β) of the drug were found to be short (0.51 and 12.60 h, respectively). The drug penetration from the plasma to the tissues was adequate as the apparent volume of distribution of the drug at steady-state ( V _d(ss)) was found to be 2.11 L kg⁻¹. The mean residence time ( MRT ) of OA was short (14.25 h) and the total clearance rate ( Cl _T) of the drug was low (0.15 L kg⁻¹ h⁻¹). The bioavailability ( F %) of OA following oral administration (30 mg kg⁻¹) was also low (14%). Maximum values were observed for muscle at 0.5 h after injection, with levels declining as with subsequent sampling. At the first two time points (0.5 and 1 h) plasma levels of OA were higher than muscle, however, the reverse was evident for subsequent samples. Following oral administration, highest muscle levels were found at 16 h and, with the exception of the 24-h sampling, muscle OA concentrations were higher than plasma at all time points. The fast elimination of OA suggests short withdrawal times with reference to human consumption of treated fish.     

Evaluation of indigenous marine periphytic Amphora, Navicula and Cymbella grown on substrate as feed supplement in Penaeus monodon postlarval hatchery system

Three isolated marine diatoms ( Amphora , Navicula and Cymbella ) grown on substrate were evaluated as feed supplement for Penaeus monodon postlarvae (PL) in hatchery system for a period of 19 days without changing water. Specific growth rate (day⁻¹) (0.27 ± 0.0) and survival (%) (56.3 ± 1.8) of PLs were significantly higher ( P  < 0.05) in treatment tanks when compared with the control (0.20 ± 0.0; 36.0 ± 1.5, respectively). Shrimp PLs reared in substrate-based tanks had significantly higher ( P  < 0.05) levels of protein, lipid (521.0 ± 7.0; 304.0 ± 2 g kg⁻¹ dry weight, respectively), ecosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (189.0 ± 2.0; 176.0 ± 2 g kg⁻¹ of total fatty acid, respectively) than the control (435.0 ± 22.0; 258.0 ± 22 g kg⁻¹ dry weight; 172.0 ± 5.0; 152 ± 2 g kg⁻¹ total fatty acid, respectively). The periphytic diatoms contained protein and lipid (430–490; 230–260 g kg⁻¹ dry weight, respectively), EPA (30–150 g kg⁻¹ of total fatty acids), DHA (20–30 g kg⁻¹ of total fatty acids) and nine essential amino acids. The results showed that isolated marine periphytic diatoms grown on substrate could be used as feed supplement in enhancing the growth and survival of P. monodon postlarvae.     

Dietary vitamin E requirement of hybrid striped bass (Morone chrysops female × M. saxatilis male)

This study was conducted to determine the dietary vitamin E requirement of juvenile hybrid striped bass ( Morone chrysops female ×  Morone saxatilis male). Semi-purified diets supplemented with 0.2 mg Se kg⁻¹ from Na₂SeO₃ and either 0 (basal), 10, 20, 40, 60, or 80 mg vitamin E kg⁻¹ as  DL -α-tocopheryl acetate were fed to hybrid striped bass initially averaging 1.8 ± 0.1 g (mean ± SD) for 12 weeks. Fish fed the basal diet, which contained 5.8 mg α-tocopherol kg⁻¹ dry weight, were darker in colour and had reduced weight gain, as well as generally reduced haematocrit values compared with fish fed diets supplemented with vitamin E. In addition, fish fed diets containing less than 20 mg supplemental vitamin E kg⁻¹ had significantly ( P  < 0.05) reduced weight gain and feed efficiency compared with those fed diets supplemented with vitamin E at 20–80 mg kg⁻¹. Dietary supplementation of vitamin E caused incremental increases in the concentration of α-tocopherol in both plasma and liver tissues. However, hybrid striped bass fed graded levels of vitamin E did not exhibit a dose response in terms of ascorbic acid-stimulated lipid peroxidation of hepatic microsomes. Regression analysis of weight gain data using the broken-line model indicated a minimum vitamin E requirement ( ±  SE) of 28 ( ±  3) mg kg⁻¹ dry diet. Based on these data, the dietary vitamin E requirement of hybrid striped bass appears to be similar to that determined for other fish species.     

Dietary threonine requirement of juvenile hybrid striped bass (Morone chrysops♀×M. saxatilis♂)

Two growth studies were conducted to determine the dietary threonine requirement of reciprocal cross hybrid striped (sunshine) bass. Semipurified diets were prepared with crystalline amino acids and lyophilized fish muscle to supply 350 g crude protein kg⁻¹ diet. The basal diet contained 4.9 g threonine kg⁻¹ from fish muscle, and test diets were supplemented with graded levels of L-threonine. In the first experiment, fish initially averaging ≊ 9.8 g each were fed diets containing threonine levels of 4.9, 7.5, 10.0, 12.5, 15.0 and 17.5 g kg⁻¹ dry diet for 7 weeks. Weight gain, feed efficiency and protein efficiency ratio (PER) were significantly ( P < 0.01) influenced by dietary threonine level. Based on weight-gain responses, a threonine requirement (± SE) of 8.4 (± 0.8) g kg⁻¹ dry diet was determined, and dietary threonine levels of 10.0 g kg⁻¹ diet or greater resulted in the highest levels of free threonine in plasma.
Based on the results of the first experiment, a second feeding trial was conducted with diets containing threonine levels of 4.9, 6.5, 8.0, 9.5, 11.0 and 12.5 g kg⁻¹ dry diet. Fish initially averaging ≊ 3.0 g each were fed each diet for 8 weeks. Weight gain, feed efficiency and PER values of fish were markedly improved, with increases in dietary threonine up to 8.0 g kg⁻¹ dry diet. Regression analysis of weight gain, feed efficiency and PER data using the broken-line model resulted in threonine requirement estimates of 9.7, 8.5 and 8.6 g kg⁻¹ dry diet, respectively. Based on these data, the threonine requirement of juvenile sunshine bass was determined to be ≊ 9.0 g kg⁻¹ dry diet or 26 g kg⁻¹ of dietary protein.     

Changes in skin colour and cortisol response of Australian snapper Pagrus auratus (Bloch & Schneider, 1801) to different background colours

A two-factor experiment was carried out to investigate the change in skin colour and plasma cortisol response of cultured Australian snapper Pagrus auratus to a change in background colour. Snapper (mean weight=437 g) were held in black or white tanks and fed diets containing 39 mg unesterified astaxanthin kg⁻¹ for 49 days before being transferred from white tanks to black cages (WB) or black tanks to white cages (BW). Skin colour values [ L ^* (lightness), a ^* (redness) and b ^* (yellowness)] of all snapper were measured at stocking ( t =0 days) and from cages of fish randomly assigned to each sampling time at 0.25, 0.5, 1, 2, 3, 5 and 7 days. Plasma cortisol was measured in anaesthetized snapper following colour measurements at 0, 1 and 7 days. Fish from additional black-to-black (BB) and white-to-white (WW) control treatments were also sampled for colour and cortisol at those times. Rapid changes occurred in skin lightness ( L ^* values) after altering background colour with maximum change in L ^* values for BW and WB treatments occurring within 1 day. Skin redness ( a ^*) of BW snapper continued to steadily decrease over the 7 days ( a ^*=7.93 × e^{−0.051 × time}). Plasma cortisol concentrations were highest at stocking when fish were held at greater densities and were not affected by cage colour. The results of this study suggest that transferring dark coloured snapper to white cages for 1 day is sufficient to affect the greatest benefit in terms of producing light coloured fish while minimizing the reduction in favourable red skin colouration.     

Feasibility of cultivation of Kappaphycus alvarezii (Doty) Doty at different localities on the Northwest coast of India

Kappaphycus alvarezii was cultivated at three places, viz. Mithapur, Okha and Beyt Dwarka on the Northwest coast of India. The biomass and growth rates were measured at 15-day intervals up to 45 days and varied differently for different growth periods at these places. Thus, at 15, 30 and 45 days, the biomass (fresh wt) varied from 182.0±19.96 to 435.0±23.66 g, from 366.0±118.09 to 1096.0±61.43 g and from 530.5±50.95 to 1537.0±43.54 g, respectively, with respective daily growth rates (%) from 3.95±0.78 to 9.80±0.63, from 3.64±0.01 to 13.98±3.07 and from 3.69±0.23 to 6.07±0.06. The seawater temperature, salinity, nitrate and phosphate ranged from 19.3 to 26.9 °C, from 30.81 to 36.83‰, from 11.60 to 19.75 μmol L⁻¹ and from 2.37 to 5.0 μmol L⁻¹ respectively. The growth rate between the culture months was significantly different at Okha at P <0.01. Further, it was significantly correlated to salinity at Mithapur while at Okha and Beyt Dwarka, the same was significantly correlated to nitrate and seawater temperature. Based on this study, commercial cultivation at these localities is quite feasible.     

Urea in feeds for sea water farmed Atlantic salmon: effect on growth, carcass quality and outbreaks of winter ulcer

The main objective of the present study was to evaluate whether dietary supplementation of urea might reduce the incidence of winter ulcer in sea water-farmed Atlantic salmon. Salmon destined to be S0 smolt were fed with a urea-supplemented diet (0 or 20 g kg⁻¹ urea) over an 8-week period prior to sea water transfer and were then fed supplemented diet (0, 5, 10 or 20 g kg⁻¹ urea) during the first and second winters in the sea. During the first winter positive relationships between dietary urea and plasma urea and between plasma urea and plasma osmolality were observed. Further, plasma osmolality displayed a negative relationship to mortality. Of the salmon that died during the first winter in the sea 90% had one or more skin ulcers. Both during the first and second winter there were fewer salmon with ulcer among fish fed with the diets supplemented with urea. Salmon fed with 20 g kg⁻¹ urea tended to have higher percentage water in the muscle. Mortality and incidence of salmon with ulcer seemed to relate to plasma osmolality amongst fish fed on diets that differed in levels of urea supplementation, suggesting that an osmotic imbalance may contribute to the development of winter ulcer in farmed salmon. Salmon fed with 20 g kg⁻¹ urea showed significantly greater body weight during the second winter in sea. Fish killed without prior starvation had significantly higher level of muscle urea in the 20 g kg⁻¹ urea group compared with fish fed with the unsupplemented diet. However, a 13-day starvation period reduced urea content in the muscle to the level of the control. No effects of dietary urea supplementation on the sensory quality of market size Atlantic salmon were observed.     

Physiological responses of juvenile wedge sole Dicologoglossa cuneata (Moreau) to high stocking density

Physiological responses to a high stocking density were tested in juvenile wedge sole Dicologoglossa cuneata (Moreau). Fish were kept at low (1 kg m⁻²), medium (3 kg m⁻²) and high (9 kg m⁻²) stocking densities for 22 days. No differences in the weight, length, survival and hepatosomatic index were observed among treatments. Basal plasma cortisol and osmolality were found to be directly and positively related to stocking density. A mild increase in plasma glucose was seen at medium density, and plasma protein was elevated at medium and high densities. The liver glucose and glycogen content was inversely related to stocking density. The liver triglyceride level was significantly elevated at the highest density, and the α-amino acid content decreased at the highest density. In muscle, glucose levels were significantly higher in fish kept at the lowest density; the α-amino acid content was elevated in fish kept at high density. In conclusion, plasma cortisol levels indicated an increasing stress level depending on the culture density, but significant changes in energy reserves did not occur in tissue (mainly liver and muscle glycogen and glucose reserves were significantly affected).     

Effects of prey nutritional quality on the growth and survival of juvenile cuttlefish, Sepia officinalis (Linnaeus, 1758)

This investigation examined the effect of prey condition on the growth and survival of juvenile cuttlefish ( Sepia officinalis ). In the first group, cuttlefish were fed with daily captured live Palaeomonetes varians from the wild [daily prey (DP)], the second group was fed 5 days stocked and starved P. varians [starved prey (SP)], while in the third group, cuttlefish were fed 8 days stocked P. varians fed with an artificial diet [fed prey (FP)]. Mean instantaneous growth rate (IGR) was 2.8±1% body weight day⁻¹ (bw day⁻¹), 3.3±1.1% bw day⁻¹ and 4.9±0.5% bw day⁻¹ for SP, DP and FP respectively. At the end of the experiment, final weight gain ( W _g) was 121±21.6%, 153.8±17.3% and 295±29.8% for SP, DP and FP respectively. No significant differences were found ( P >0.05) between growth curves for every group tested, or for the food conversions between those same groups ( P >0.05), but statistical differences ( P <0.05) were found in IGR between DP vs. FP and SP vs. FP. Mortality was 2 and 1 for SP and DP respectively. Results indicate that prey starvation should not be considered when feeding juvenile cuttlefish, as prey can only be stocked if proper artificial diets are provided, to obtain optimal growth.     

Recovery of Serratia marcescens in Hemolymph of Macrobrachium rosenbergii from Experimentally Seeded Water

Seratia marcescens was used as an indicator to determine if different concentrations of bacteria in water relate to concentrations in the hemolymph of Macrobrachium rosenbergii . Prawns were exposed to high (10⁵ to 10⁶ cells/ml), low (10³ to 10⁴ cells/ml) and control (no S. marcescens ) treatments with S. marcescens inoculated in aquaria water. S. marcescens ranged from 10 to 9.9 ± 10³ cells/ml from the high concentration group; a single isolate and zero S. marcescens were recovered from the low and control groups, respectively.     

Effects of dietary supplementation of alga Haematococcus pluvialis (Flotow), synthetic astaxanthin and β-carotene on survival, growth, and pigment distribution of red devil, Cichlasoma citrinellum (Günther)

Dietary carotenoids of various types and concentration can affect the pigmentation efficiency in an ornamental fish red devil, Cichlasoma citrinellum . Astaxanthin (AX) containing alga Haematococcus pluvialis , a synthetic AX, and a synthetic β-carotene (BC) were supplemented in formulated diets at two concentrations, 80 and 160 mg kg⁻¹, resulting in six pigmented diets. Formulated diet without carotenoids supplementation served as a control. These diets were fed to the fish, for 8 weeks. Astaxanthin dominated in body carotenoids deposition. Dietary BC hardly had contribution to body AX. Control fish had much lower AX content in skin, fin and muscle than fish fed pigmented diets, but had equal AX content in liver, intestine and gonad as those fish. Dietary synthetic AX had equal efficiency in depositing AX in skin and fin as natural AX but higher efficiency in gonad than natural AX. Fish fed AX supplemented at 160 mg kg⁻¹, either natural or synthetic AX, had higher AX content in skin than fish at 80 mg kg⁻¹ but had equal AX content in fin as fish at 80 mg kg⁻¹. Disregarding the treatment effects, the overall average AX content in tissue in descending order was gonad>fin≧(intestine=skin)>liver>muscle.     

Anaesthetic efficacy and physiological responses to clove oil-anaesthetized kelp grouper Epinephelus bruneus

The efficacy of clove oil as an anaesthetic and at producing a physiological response (plasma cortisol and glucose) was evaluated in the kelp grouper, Epinephelus bruneus . To acquire complete anaesthesia in less than 3 min and recovery in <10 min, three doses of clove oil were tested at 18, 22 and 26 °C. Although higher anaesthetic doses resulted in shorter induction times and longer recovery times, and a lower temperature resulted in longer anaesthesia induction and slower recovery, we found the optimal dose and administering temperature of clove oil to be 250–300 mg L⁻¹ at water temperature of 18 °C, 150–200 mg L⁻¹ at water temperature of 22 °C and 50–100 mg L⁻¹ at water temperature of 26 °C respectively. Following the administration of 150 mg L⁻¹ of clove oil at 22 °C, the plasma cortisol level was highest (4.24 ± 1.571 μg dL⁻¹) after 12 h and the plasma glucose was highest (92.7 ± 9.61 mg dL⁻¹) after 2 h. These results should be useful to the aquaculture industry, where anaesthesia is necessary for a range of activities.     

Dietary vitamin C requirement of red drum Sciaenops ocellatus

A feeding trial was conducted to determine the minimum dietary vitamin C requirement of juvenile red drum and characterize signs of vitamin C deficiency. Semipurified diets containing 400 g crude protein kg^–1 from lyophilized red drum muscle and crystalline amino acids were used in the feeding trial. The basal diet without supplemental vitamin C contained ≈ 6 mg vitamin C kg^–1 and was fed for a 1-week conditioning period. Red drum, initially averaging ≈ 3.6 g each, were fed diets supplemented with 0, 10, 20, 30, 45, 60, 75, or 150 mg vitamin C kg^–1 as ascorbate polyphosphate for a period of 10 weeks. Fish fed the basal diet began to exhibit overt signs of vitamin C deficiency, including reduced weight gain, lordosis, scoliosis and loss of equilibrium after 8 weeks. Total ascorbate was undetectable in liver of fish fed the basal diet while liver ascorbate levels in fish fed the other diets generally reflected dietary supplementation. Regression analysis of weight gain data using the broken-line model resulted in a minimum vitamin C requirement ( ± SE) of 15 ± 3 mg kg^–1 diet.     

Creation of artificial upwelling areas for brown trout, Salmo trutta, spawning in still water bodies

Abstract  Brown trout, Salmo trutta L., spawning sites were constructed by creating areas of artificial upwelling water, 252 ± 37 mL m⁻² min⁻¹ (95% CL), through appropriately sized spawning gravel substrate in 3 m² vessels buried in the bottom of a 150-m² pond. Natural spawning occurred in the vessels during autumn 2001–2004, with hatching and alevin swim up the following spring. In areas of upwelling, egg survival was 85–95%, while no live eggs were observed in areas without upwelling. In areas with upwelling, the maximum density of live eggs at the eyed stage was 570–1510 eggs m⁻². In spring 2004 and 2005, the density of alevins was estimated at 322 (±187) m⁻² and 567 (±217) m⁻², respectively, in areas with upwelling water, compared with 35.2 ± 25.4 m⁻² in areas without upwelling water in 2004.     

Efficacy of silicone-coated ascorbic acid and ascorbyl-2-polyphosphate to fast-growing tiger shrimp (Penaeus monodon)

Growth, survival, tissue ascorbate concentration and collagen content were studied in fast-growing Penaeus monodon fed two ascorbic acid (AA) derivatives. Prior to the experimental trial, shrimp (initial body weight: 0.9 ± 0.4 g) were fed on a diet lacking vitamin C for 5 weeks. During the following 13-week experiment, the shrimp (initial body weight: 8.2 ± 0.7 g) were given one of five squid-meal-based diets. The dietary treatments consisted of a diet lacking vitamin C, two diets supplemented with either 500 or 1000 mg AA kg⁻¹ in the form of silicone-coated AA, and two diets supplemented with either 500 or 1000 mg AA kg⁻¹ in the form of ascorbyl-2-polyphosphate. Shrimp gained 18.3 g in 13 weeks. The AA-free diet group exhibited the lowest growth rate, feed intake and survival (26.8%) after 4 weeks. Hepatopancreatic ascorbate and muscle collagen content were significantly ( P < 0.05) lower in AA-deprived shrimp. At the end of the feeding trial, growth rate and survival were not significantly ( P > 0.05) different among groups fed AA-supplemented diets. Hepatopancreatic and haemolymphatic ascorbate concentrations were significantly ( P < 0.05) higher in groups given ascorbyl-2-polyphosphate than in groups given silicone-coated AA. A supplement of 500 mg AA kg⁻¹ diet in the form of either silicone-coated AA or ascorbyl-2-polyphosphate was adequate for optimal growth. But ascorbate concentrations in tissues remained much below saturation levels with a supplement of 1000 mg AA kg⁻¹ diet. It is questionable whether the established vitamin C requirements for P. monodon are adequate to maintain tissue ascorbate in fast-growing juveniles.