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1.
Genetic effects on cold‐stress tolerance were assessed for red drum (Sciaenops ocellatus), an economically important sciaenid fish in the southern USA. Thirty‐five families were generated via ‘natural’ spawning of multiple sets of five breeders (three dams × two sires) in individual brood tanks. Offspring from the 35 families were transferred abruptly from an acclimation temperature of ～24 °C to 5.7 °C and maintained subsequently at an average temperature of 6.5 °C. Offspring were assigned a posteriori to individual broodfish (dam and sire) based on genotypes at nuclear‐encoded microsatellites. Heritability of the survival–time probability function was estimated using a proportional hazard approach and an animal‐additive model. The estimated heritability was 0.20 (95% CI: 0.07–0.40), indicating a significant genetic component to acute cold‐stress tolerance in red drum.  相似文献   

2.
ABSTRACT

Eighteen to 29 families of red drum were generated via spontaneous spawning of multiple sets of three dams?×?two sires. In 2002, offspring from spawning events were grown in separate larval ponds to a mean TL of 30.4 mm. In 2003, offspring from spawning events were individually passive integrated transponder (PIT)-tagged and grown in “common-garden” tanks from 121.9 to 166.6 mm. Offspring in both experiments were assigned to parents based on genotypes at four microsatellite loci. Heritability estimates were 0.24?±?0.06 (larval TL) and 0.48?±?0.16 (juvenile-specific growth rate in length) and indicate a significant genetic component for both traits.  相似文献   

3.
In this study, heritability was estimated for growth‐related traits of giant freshwater prawn (Macrobrachium rosenbergii) before and after morphological sexual differentiation. Estimation was made on data from 16 full‐sib and eight half‐sib families. The variance estimation was performed using a univariate mixed linear animal model and variance components were analysed following an animal model using restricted maximum likelihood procedure using average information algorithm. Heritability estimates (h2) varied considerably with ages. At 2 months old, h2for carapace length (CL; 0.35±0.15) and body weight (BW; 0.26±0.13) were higher than those estimated at 5 months old, based on mixed sex data. However, when data were sorted by sex, h2 calculated from data of females were higher than those of males for CL (0.26±0.16 vs. 0.10±0.06), BW (0.28±0.17 vs. 0.12±0.08), body length (0.40±0.17 vs. 0.11±0.07), total length (0.47±0.18 vs. 0.11±0.07) and claw length (0.29±0.16 vs. 0.03±0.04). The same trend was observed for traits at 6 months old in both bulk and individual rearing.  相似文献   

4.
An experiment was carried out to determine the effects of dietary fish oil replacement at an optimal level on the growth and carcass proximate composition of juvenile barramundi or sea bass (Lates calcarifer). Ten fish feeds were formulated to contain iso‐ingredients with theoretically identical dietary lipid levels but with different sources of lipids (fish oil, soybean oil, canola oil and linseed oil) replacing dietary fish oil. Three hundred fish were equally divided into 30 70‐L plastic tanks (three replicate tanks for each treatment). Fish were fed with experimental diets for 40 days within closed recirculating freshwater systems (70 L h?1, 28°C and 12L:12D). Growth, specific growth rate, food conversion ratio (FCR) and carcass proximate composition were determined. Dietary lipids significantly affected (P<0.05) the growth of the fish. Good growth and low FCR were observed in all treatments. Therefore, fish oils can be partially replaced by vegetable oils to reduce the feed cost. There were no significant differences (P>0.05) in lipid, moisture and protein content in fish carcasses among the group. However, juvenile barramundi showed increasing lipid and moisture content in muscle, whereas decreasing protein content when compared to the initial fish.  相似文献   

5.
This preliminary study assessed genotype × diet interaction in late growth of European sea bass (Dicentrarchus labrax) fed with either a fish meal (FM)‐ or a fish oil (FO)‐based diet (M) or an all‐plant‐based (PB) diet. A total of 550 fish from 224 families were reared together and tagged. DNA was sampled and microsatellites were used to assign parentage. When fish weight was 192 ± 54 g, two tanks were fed with M (FM: 100%; FO: 100%) and two others with PB (FM: 0% and FO: 0%). Body weight (BW), fork length (FL) and fillet lipid content (CorrFat) were analysed with a linear model and with REML methodology. We observed no significant differences between groups, but a slightly lower (P=0.03) daily growth coefficient in sea bass fed PB than in those fed M. Heritability estimates of BW differed significantly from zero (PB: 0.37 ± 0.18; M: 0.47 ± 0.24). Sire × diet interactions were significant and genetic correlations ranged between 0.51 and 0.87, showing genotype × diet interaction for BW and CorrFat. For the first time, genetic parameters in the context of total replacement of marine fishery by‐products were estimated in European sea bass, showing re‐ranking of family performances with extremely contrasted diets.  相似文献   

6.
This study was designed to evaluate the effects of dietary supplementation with brewers yeast (Brewtech®) and nucleotides (Optimûn), either singularly or in combination, on red drum growth, body composition, stress responses and possible resistance to Amyloodinium ocellatum infection. Juvenile red drum (～1 g initially) fed practical fish‐meal‐based diets for 6 weeks had similar weight gain regardless of whether the diet was unsupplemented (basal) or supplemented with brewers yeast (2% of diet), nucleotides (Optimûn at 0.2% of diet) or both brewers yeast (2% of diet) and nucleotides (Optimûn at 0.2% of diet). Dietary effects on hepatosomatic index, intraperitoneal fat ratio or whole‐body composition were not significant, except that fish fed the singular nucleotide supplement had a significantly higher whole‐body lipid content compared with fish fed the basal diet. No significant dietary effects on cortisol response were observed after a 15 min confinement stress test perhaps because of the extreme variation among individual fish. Subsequently, in situ challenge by co‐habitation with A. ocellatum caused 100% mortality regardless of dietary treatment within a 48 h period. It is concluded that dietary supplementation of brewers yeast and nucleotides did not promote enhanced growth or improved cortisol response and resistance to uncontrolled amyloodiniosis in juvenile red drum, at least at the tested dosages.  相似文献   

7.
Two separate feeding trials examined the effects of dietary supplementation of the prebiotics GroBiotic®‐A and inulin on growth performance and gastrointestinal tract microbiota of the red drum, Sciaenops ocellatus. In the first feeding trial, fish meal‐based diets without prebiotics or supplemented with either GroBiotic®‐A or inulin at 1% of dry weight were fed to triplicate groups of juvenile red drum (initial weight of 2.6 g) in 110‐L aquaria operated as a brackish water (7 ppt) recirculating system for 8 wk. In the second feeding trial, soybean meal/fish meal‐based diets supplemented with either GroBiotic®‐A or inulin at 1% of dry weight were fed to triplicate groups of red drum (initial weight of 15.8 g) in 110‐L aquaria operated as either a common recirculating water system or closed system with individual biofilters (independent aquaria) for 6 wk. Supplementation of the prebiotics in either feeding trial did not alter weight gain, feed efficiency ratio, or protein efficiency ratio of red drum fed the various diets. In the second feeding trial, the culture system significantly affected weight gain, feed efficiency ratio, and protein efficiency ratio although there were no effects of dietary treatments on fish performance or whole‐body protein, lipid, moisture, or ash. Denaturing gradient gel electrophoresis (DGGE) analysis of the gastrointestinal tract microbial community showed no effect of the dietary prebiotics as the microbial community appeared to be dominated by a single organism with very low diversity when compared with other livestock and fish species. DGGE of the microbial community in the biofilters of the independent aquariums showed a diverse microbial community that was not affected by the dietary prebiotics.  相似文献   

8.
An 11‐week growth trial was conducted to determine dietary myo‐inositol (MI) requirement for juvenile gibel carp (Carassius auratus gibelio). Myo‐inositol was supplemented to the basal diet to formulate six purified diets containing 1, 56, 107, 146, 194 and 247 mg MI kg?1 diet, respectively. Each diet was fed to triplicate groups of juvenile gibel carp (initial body weight 3.38 ± 0.27 g, mean ± SD) in a flow‐through system. The diets were randomly assigned to different fish tanks. Fish fed ≥ 107 mg MI kg?1 diet had significantly higher weight gain (WG), feed efficiency (FE) and protein efficiency ratio than those fed 1 mg MI kg?1 diet. Fish fed ≥ 56 mg MI kg?1 diet had higher feeding rate and survival compared with fish fed 1 mg MI kg?1 diet. Dietary supplemental inositol did not affect fish liver inositol concentration. Fish fed ≥ 56 mg MI kg?1 diet had higher body dry matter, crude protein and gross energy and lower hepatosomatic index than fish fed 1 mg MI kg?1 diet. Dietary inositol supplementation decreased fish body ash. Quadratic regression of weight gain indicated that the myo‐inositol requirement to maximum growth for juvenile gibel carp was 165.3 mg MI kg?1 diet.  相似文献   

9.
This study investigates the effect of the feed supply rate within a meal on growth of juvenile perch (Perca fluviatilis). Groups of PIT-tagged, feed-trained juvenile perch (12 g) were held in 100-L tanks at 18 °C, under a 24L:0D photoperiod and fed five meals per day in excess. Feed was applied at rates of 1.2 (Low), 4.2 (Medium) and 14.3 (High) pellets fish−1 min−1 during two periods, each of 50 days. Cumulative meal-time per day ranged from 10 to 225 min. Specific growth rates (SGR) in the two periods were positively correlated, indicating a consistent individual growth performance. There was growth dimorphism between the sexes. Females grew about 20% faster than males, resulting in final mean weights of ≈ 87 and 58 g respectively. Autopsy revealed differences in sex ratios between treatments and the effect of feeding rate was analysed according to sex. There was a tendency for fish fed at the lowest rate to have a higher SGR than fish in other treatments, both for females (L = 1.98 ± 0.0, M = 1.84 ± 0.08, H = 1.88 ± 0.19% bw day−1) and males (L = 1.68 ± 0.01, M = 1.55 ± 0.16, H = 1.57 ± 0.02% bw day−1). Fish fed at the lowest rate also tended to have the lowest feed conversion ratio (L = 0.88 ± 0.05, M = 1.02 ± 0.11, H = 1.04 ± 0.10) but the effects were not significant. These results suggest that juvenile perch can feed efficiently under a range of conditions.  相似文献   

10.
A low‐head recirculating aquaculture system (RAS) for the production of Florida pompano, Trachinotus carolinus, from juvenile to market size was evaluated. The 32.4‐m3 RAS consisted of three dual‐drain, 3‐m diameter culture tanks of 7.8‐m3 volume each, two 0.71‐m3 moving bed bioreactors filled with media (67% fill with K1 Kaldness media) for biofiltration, two degassing towers for CO2 removal and aeration, a drum filter with a 40‐µm screen for solids removal, and a 1‐hp low‐head propeller pump for water circulation. Supplemental oxygenation was provided in each tank by ultrafine ceramic diffusers and system salinity was maintained at 7.0 g/L. Juvenile pompano (0.043 kg mean weight) were stocked into each of the three tanks at an initial density of 1.7 kg/m3 (300 fish/tank). After 306 d of culture, the mean weight of the fish harvested from each tank ranged from 0.589 to 0.655 kg with survival ranging from 57.7 to 81.7%. During the culture period, the average water use per kilogram of fish was 3.26 or 1.82 m3 per fish harvested. Energy consumption per kilogram of fish was 47.2 or 22.4 kwh per fish harvested. The mean volumetric total ammonia nitrogen (TAN) removal rate of the bioreactors was 127.6 ± 58.3 g TAN removed/m3 media‐d with an average of 33.0% removal per pass. Results of this evaluation suggest that system modifications are warranted to enhance production to commercial levels (>60 kg/m3).  相似文献   

11.
Two experiments were conducted to examine the effect of commercially available beta‐glucan (Macrogard) and nucleotide (Aquagen) on the resistance to Streptococcus iniae infections in vaccinated or nonvaccinated juvenile red‐tail black sharks (Epalzeorhynchos bicolor, RTB) (1.4 ± 0.4 g weight total (WT), 5.6 ± 0.5 cm total length (TL)). The immunostimulants were added to a control diet formulated without any yeast source following the recommended doses of 1 g/kg feed for the beta‐glucan and 2 g/kg feed for the nucleotide. Beginning 4 d after introduction into tanks, fish were fed the experimental diets for 24 d, at 3% body weight per day, divided into two feedings. At the end of this period, fish were challenged by an intracoelomic injection of S. iniae. In the first experiment, both vaccinated and nonvaccinated fish were fed one of the two immunostimulants. In the second experiment, only vaccinated fish were fed the immunostimulants. Fish were vaccinated a week after being introduced into the system and challenged by intracoelomic injection with 1.5 × 105 S. iniae colony‐forming units /fish after three additional weeks; mortality was recorded for 2 wk after the bacterial challenge. In the first experiment, the mortality of both vaccinated and nonvaccinated fish fed beta‐glucan (23 ± 7% and 82 ± 1%, respectively) or nucleotide (28 ± 6% and 86 ± 5%, respectively) was significantly lower than the mortality of the control groups (35 ± 4% and 93 ± 5%, respectively), but there was no significant difference in mortality between fish fed beta‐glucan or nucleotide. In the second experiment, the mortality of vaccinated fish fed beta‐glucan (25 ± 7%) or nucleotide (43 ± 9%) was significantly lower than that of vaccinated fish fed the control diet (69 ± 7%). In both experiments, there was no significant difference in growth rate among fish fed immunostimulants or the control diet. The results of this investigation demonstrated the efficacy of beta‐glucans and nucleotides in increasing resistance to S. iniae in RTB sharks.  相似文献   

12.
An 8‐week comparative slaughter experiment was carried out to determine the effect of dietary protein and lipid on growth, apparent digestibility (AD) and nutrient retention of polka dot grouper Cromileptes altivelis. Fingerlings were fed diets that varied in crude protein (CP) at 55 g kg?1 increments between 410 and 630 g kg?1 dry matter (DM) and at either a moderate (150 g kg?1 DM) or high (240 g kg?1DM) lipid concentration. Each diet was fed to satiety twice daily to four replicate tanks (110 L) of fish. One replicate block of tanks comprised 150 fish of mean (±SD) initial weight of 9.6 ± 0.29 g, which were distributed equally to 10 tanks. The other three replicate blocks of tanks comprised 300 fish of 12.6 ± 0.45 g, which were distributed equally to 30 tanks. Tanks were provided with filtered and heated (29 ± 0.5 °C) seawater in a flow‐through system within a laboratory where photoperiod was maintained at 12 : 12 h light–dark cycle. Voluntary food intake was not significantly affected by either the CP or lipid concentration of the diet (mean ± SD of 1.93 ± 0.146 g week?1) but there was a trend for intake to be higher on the moderate compared with the high lipid diets (mean ± SEM of 1.97 versus 1.89 ± 0.033 gweek?1, respectively). Daily growth coefficient (DGC) and food conversion ratio (FCR) improved linearly (P < 0.01) with increasing dietary CP (from 0.94 to 1.35% day?1 for DGC and 1.58 to 1.00 g DM g?1 wet gain for FCR) and these responses were almost coincident for each of the lipid series. The AD of CP increased linearly with increasing dietary CP (from 46.8 to 74.1%) and was independent of dietary lipid. Apparent digestibility of energy increased curvilinearly with increasing dietary CP, with the quadratic component being more prominent for the high‐lipid series. Increasing the amount of lipid in the diet markedly increased the lipid content of the fish from an initial composition (mean ± SD) of 173 ± 7.3 g kg?1 to a final composition (mean ± SEM) of either 217 or 250 ± 5.9 g kg?1 for moderate and high‐lipid series, respectively. Total body lipid content tended to increase linearly with increasing dietary CP for the high‐lipid series but with an opposite effect for the moderate‐lipid series. The retention of digestible nitrogen decreased linearly with increasing dietary CP but at a steeper rate for the moderate, compared with the high, lipid series (from 62.7 to 35.7%, slope ?0.115 for moderate‐lipid and 54.6 to 41.9%, slope ?0.050 for high‐lipid). A quadratic function of dietary CP concentration best explained the retention of digestible energy with the curvilinearity being more marked for the high, compared with the moderate, lipid diet series. While there was some indication that ingested lipid spared dietary protein, the results showed a far greater propensity of polka dot grouper fingerlings to use protein as the prime dietary energy source. Diets for juvenile polka dot grouper should contain not less than 440 g digestible protein kg?1 DM and at least 150 g lipid kg?1 DM.  相似文献   

13.
Silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), is an endemic species from Latin America that is raised in cultivation ponds, and consequently may be exposed to low oxygen levels. Therefore, the objective of this study was to verify the lethal concentration (CL50?96 h) of dissolved oxygen levels for silver catfish juveniles. In addition, the effects of different dissolved oxygen levels (1.96±0.08, 3.10±0.10, 4.14±0.09, 5.20±0.07 and 6.16±0.03 mg L?1) on growth and metabolic parameters (glycogen, glucose, protein, lactate levels and catalase activity) were also investigated. CL50?96 h was 0.52 mg L?1 (CI 0.42–0.61 mg L?1) or 6.7% oxygen saturation. After exposure of silver catfish to hypoxia for 30 days, there were no changes in biochemical parameters indicating the use of an anaerobic pathway by the fish. However, the dissolved oxygen levels influenced silver catfish juvenile behaviour, survival and growth, and under the experimental conditions 5.2 mg L?1 (or 65.6% oxygen saturation) is the minimum oxygen level recommended for the growth of this species.  相似文献   

14.
A 56‐day experiment was conducted to investigate the effect of no carbohydrate addition applied to control water quality in water‐reusing biofloc systems for tilapia (GIFT Oreochromis niloticus) cultivation. Reusing water‐contained flocs was initially inoculated into six 300 L indoor tanks. Thirty fish (average individual weight 99.62 ± 7.34 g) were stocked in each tank. Glucose was extra added into three tanks (GLU‐tanks) according to biofloc technology, while other tanks were no carbohydrate added (NCA‐tanks). Concentrations of total ammonia nitrogen in GLU‐tanks and NCA‐tanks were fairly consistent and below 4.74 ± 0.35 mg/L. Nitrite concentrations in NCA‐tanks were significantly lower than GLU‐tanks, which were below 0.59 ± 0.10 mg/L during the later culture period. NCA‐tanks achieved a low relative abundance of denitrifiers and high concentrations of nitrate. Soluble reactive phosphorous in NCA‐tanks was consistently increased, which was decreased to a low level in GLU‐tanks. However, growth parameters in NCA‐tanks were similar to GLU‐tanks (p > .05) and reach a high finial density of 24.32 ± 1.04 kg/m3. Cetobacterium sp. was the first‐dominant bacterial genus in all tanks, which was a commonly indigenous bacterium in the intestinal tract of freshwater fish. The results demonstrate the feasibility of no carbohydrate addition in water‐reusing biofloc systems for tilapia.  相似文献   

15.
Protein requirement of silver barb, Puntius gonionotus fingerlings   总被引：2，自引：0，他引：2  
Five iso‐energetic (15.05 MJ kg?1) semi‐purified diets with graded levels of crude protein, i.e. 200 (D‐1), 250 (D‐2), 300 (D‐3), 350 (D‐4) and 400 (D‐5) g kg?1 diet were fed to Puntius gonionotus fingerlings (average weight 0.88 ± 0.03 g) in triplicate groups (15 healthy fish per replicate) for a period of 90 days to determine the optimum protein requirement of the fish. Fifteen flow‐through cement tanks of 100‐L capacity with a flow rate of 0.5 L min?1 were used for rearing the fish. Specific growth rate (SGR), food conversion (food gain) ratio (FCR), nutrient digestibility and retention, digestive enzyme activity, RNA : DNA ratio and tissue composition were used as response parameters with respect to dietary protein levels and feed intake. The mean weight gains of fish after 90 days were 10.84 ± 0.27, 11.07 ± 0.12, 14.09 ± 0.20, 11.27 ± 0.12 and 10.91 ± 0.25 g for D‐1, D‐2, D‐3, D‐4 and D‐5, respectively. Maximum SGR (3.13 ± 0.02% per day), RNA : DNA ratio (10.09 ± 0.09), tissue protein content (160 ± 0.1 g kg?1 wet weight), protease activity (25.27 ± 0.47 μg of leucine liberated mg tissue per protein h?1 at 37 °C) and minimum FCR (1.60 ± 0.02) was found in D‐3 group fed with 300 g kg?1 protein level. All these parameters were negatively affected with the further increase in protein level in the diet. Digestibility of protein, lipid and energy was not affected because of variation in dietary protein levels and nitrogen intake of fish. Maximum energy retention (27.68 ± 0.12%) was recorded at 300 g kg?1 dietary crude protein fed group. However, using broken line regression analysis, the maximum growth was found to be at 317.7 g kg?1 dietary protein. Hence, it may be concluded that the protein requirement of P. gonionotus fingerling is 317.7 g kg?1 diet with a resultant P/E ratio of 21.1 g protein MJ?1.  相似文献   

16.
A feeding trial was conducted to evaluate the dietary copper requirement of red drum (Sciaenops ocellatus) and compare the bioavailability of copper sulphate (CuSO4) and copper‐ethanolamine. A basal diet was formulated using semi‐purified ingredients and analysed to contain 3 mg Cu/kg. Both copper sources were supplemented to the basal diet at either 5, 10 or 20 mg Cu/kg of dry diet. No significant differences were observed in growth performance of fish fed the various diets. However, red drum fed all copper‐supplemented diets retained more copper in liver and whole‐body tissues compared to fish fed the basal diet. Within both inorganic and organic copper treatments, the highest tissue copper concentrations were observed in fish fed diets supplemented with 10 mg Cu/kg. No significant differences were detected in net copper retention regardless of the nature of the copper source; hence, the bioavailability of copper sulphate and copper‐ethanolamine complex was not different in the diets for juvenile red drum. Furthermore, the minimum copper requirement for growth performance of juvenile red drum appeared to be satisfied when fish were fed the basal diet containing 3 mg Cu/kg diet, and no detrimental effects were observed in red drum fed diets supplemented with 20 mg Cu/kg.  相似文献   

17.
This study evaluated various by‐catch and by‐product meals of marine origin with red drum (Sciaenops ocellatus L.). Four different kinds of by‐catch or by‐product meals [shrimp by‐catch meal from shrimp trawling, Pacific white shrimp (Litopenaeus vannamei (Boone)) processing waste meal, red salmon (Oncorhynchus nerka (Walbaum)) head meal, and Pacific whiting (Merluccius productus (Ayres)) meal] were substituted for Special Select? menhaden fish meal at 33% or 67% of crude protein in diets formulated to contain 40% crude protein, 12% lipid, and 14.6 kJ digestible energy g?1. Each of these diets and three additional diets consisting of shrimp processing waste meal formulated on a digestible‐protein basis and two Pacific whiting diets containing reduced levels of ash were also evaluated in two 6‐week feeding trials with juvenile red drum (initial weight of 4–5 and 1–2 g fish?1 in trials 1 and 2). Red drum fed by‐catch meal at either level of substitution performed as well as fish fed the control diet; whereas, fish fed shrimp processing waste meal diets had significantly (P≤0.05) reduced weight gain and feed efficiency ratio values compared with the controls, even when fed on a digestible‐protein basis. The diets containing Pacific whiting at either levels of substitution and regardless of ash level supported similar performance of red drum as those fed the control diet. Fish fed the red salmon head meal diet fared poorly, probably owing to an excessive amount of lipid in the diet that became rancid. Overall, by‐catch meal associated with shrimp trawling and Pacific whiting appear to be suitable protein feedstuffs for red drum.  相似文献   

18.
Preliminary technical baseline information for the inland culture of juvenile red drum, Sciaenops ocellatus, in a freshwater fish hatchery is presented. Three initial stocking densities (d1 = 83, d2 = 167, and d3 = 250 fish/m3) were tested in a semirecirculation system for 575 days using a commercially available feed (48.1% protein, 25% lipids, and 0.13% fiber). Initial and final mean fish weight were 7.11 ± 0.02 g and 287.6 ± 27 g. As carrying capacity appeared to have been reached, only data from Days 1–333 were analyzed. One‐way ANOVA analyses indicated that the survival rate of the smaller density (d1 =40 ± 3.7%) was significantly different from the other two densities (d3 = 21 ± 1.1% and d2 = 23 ± 1.0%), which did not differ between them. Absolute growth rate (0.87 ± 0.02 g/day) was not significantly different between densities (F = 0.23. p = .801). Neither was weight significantly different between treatments. There were significant differences in the feed conversion rate (FCR) between densities (F = 8.54; p = .02). FCR for d1 was significantly lower than for the two other densities, which did not differ from each other. A von Bertalanffy growth model was adjusted (R2 = 0.95), and weight–length relationship presented negative allometric values (b = 2.85, R2 = 0.98).  相似文献   

19.
Litopenaeus vannamei were stocked in 25 clear‐water 500‐L tanks at 100 shrimp m?2 and in 25 green‐water 1000‐L tanks at 60 animals m?2. Four diets were formulated to include krill meal at 10, 50 or 110 g kg?1; or krill oil at 25 g kg?1 by replacing fish meal, fish oil, soybean lecithin and cholesterol. Diets had similar levels of crude protein, total energy and essential amino acids. After 72 days, shrimp reared in clear and green water showed no differences in performance among diets. In clear water, shrimp attained 13.1 ± 0.59 g body weight, 1.00 ± 0.06 g week?1 growth, 81.4 ± 7.3% survival, 780 ± 118 g m?2 yield, 16.9 ± 1.8 g shrimp?1 apparent feed intake (AFI), and 2.18 ± 0.29 food conversion ratio (FCR). In green water, shrimp attained 14.3 ± 0.81 g body weight, 1.04 ± 0.09 g week?1 growth, 91.4 ± 5.4% survival, 569 ± 69 g m?2 yield, 20.9 ± 3.2 g shrimp?1 AFI, and 2.22 ± 0.34 FCR. Diets containing krill meal or krill oil were able to fully replace the protein and lipid value of fish meal, fish oil, soybean lecithin and cholesterol at no cost to performance.  相似文献   

20.
A rapid sand filter (RSF, 12 m3 m−2 h−1) and a rapid sand filter followed by slow sand filter (RSF-SSF, 0.1 m3 m−2 h−1) were compared to investigate whether the biological activity in the RSF-SSF would improve turbidity reduction and control of biofilm growth in seawater aquaculture of juvenile dusky grouper over a 31 days test period. The RSF-SSF combination produced water with lower turbidity than RSF, turbidity breakthroughs in RSF were effectively abated by SSF. Microbial growth potential (MGP) measured by a growth assay with Pseudoalteromonas spongiae in samples filtered through 0,2μm membranes was significantly smaller in SSF filtrate (MGP, 3.2 ± 0,1 logCFU) than in RSF filtrate (3.9 ± 0,6 logCFU). Turbidity in fish tanks fed with RSF-SSF and RSF effluent remained below 1 NTU and 6 NTU, respectively, inspite of the large amount of food not consumed by the fish and of the tanks remaining open to the atmosphere. Surface biofouling on PVC samples was assessed by protein and carbohydrate analysis. It was less pronounced on bottoms of tanks operated with RSF-SSF treated water but similar on tank walls for both types of water. Carbohydrates were present in much larger quantities than proteins in bottom biofilms, but the opposite occurred in wall biofilms. Diatoms were dominant in RSF but not in RSF-SSF tank biofilms. Dusky grouper survival and growth was similar for the two types of water. The benefit of reduction of microbial growth potential achieved in SSF pretreatment was successfully captured in lesser tank surfaces biofilm colonization and by lower water turbidity in the tanks.  相似文献   

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