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1.
Salt (NaCl) and gypsum (CaSO4) are used as water additives to mitigate fish stress and improve specimen survival. High stocking densities and the transportation of fish can increase aqueous ammonia, which can, in turn, alter fish cortisol secretion. The objectives of this study were to assess the effects of salt, gypsum, and aqueous ammonia on some stress‐induced physiological responses of jundiá, Rhamdia quelen, juveniles induced by captivity and handling, and to determine the lethal ammonia concentration for this species. Jundiá juveniles were subjected to the following five treatments: water only, water + ammonia (0.4 mg/L), water + NH3 + NaCl (6 g/L), water + NH3 + gypsum (150 mg/L), and water + NH3 + NaCl + gypsum. Blood samples were taken after intervals of 1, 5, 24, and 96 h, and the concentrations of cortisol, glucose, chloride, ammonia, and hematocrit were determined. The NH3 LC50 value after 96 h of exposure (LC50?96h) was measured to be 1.9 mg/L NH3. Either salt or gypsum reduced both cortisol and glucose levels during most of the experimental period, but the combination of both reduced these levels even further. The combined use of NaCl and CaSO4 demonstrates a synergic effect on mitigating stress responses induced by handling and aqueous ammonia in jundiá juveniles.  相似文献   

2.

Though Biofloc Technology is a new concept in Bangladesh, it provides advantages for improving aquaculture production in many countries, leading to achieve sustainable development goals. The objectives of this study were to determine the effects of stocking densities on the growth performance of stinging catfish (Heteropneustes fossilis) under Biofloc Technology and assess the economic prospects and business feasibilities. Fingerlings were stocked in unique 5000-L tanks with three stocking densities, i.e., 3500 fish/tank (Treatment-I), 4000 fish/tank (Treatment-II), 4500 fish/tank (Treatment-III). The treatments showed significant differences (P?<?0.05) considering the species-specific growth rate, feed conversion ratio, and protein efficiency ratio. Treatment-I had significantly ((P?<?0.05) higher final biomass (29.51 ± 0.04 kg/m3) than the other treatments. The present findings revealed that using a lower stocking density, the Biofloc Technology reduced ammonia (NH3), nitrite (NO2), nitrate (NO3), TDS, and floc volume but significantly increased the dissolved oxygen. As a result, Treatment-I had generated significantly higher net income (BANGLADESHI TAKA—BDT 86,278.90) over the other treatments. Moreover, the NPV, net BCR, and RoR with 4% and 9% opportunity cost were also significantly higher in Treatment-I than other treatments. The internal rate of return (IRR) and SWOT analysis index indicates that investing in Biofloc Technology is far superior, and a stocking density of 3500 fish/tank (Treatment-I) resulted in a faster investment return.

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3.
The initial stages of rearing marine shrimp using biofloc technology (BFT) involve the biofloc formation process. At the same time, there is an increase in the levels of total suspended solids and a decrease in alkalinity and pH. This reduction of alkalinity and pH occurs due to the consumption of inorganic carbon by the autotrophic bacteria present in the bioflocs and biofilms. The aim of this study was to evaluate the effects of different alkalinities on water quality and the zootechnical performance of the marine shrimp Litopenaeus vannamei in a BFT system. The experiment consisted of four treatments, with three replicates each: 75, 150, 225 and 300 mg CaCO3/L. To maintain the alkalinity at the established level, sodium bicarbonate was applied. For the experiments, twelve experimental units (area = 0.20 m2) with an effective volume of 50 L were stocked with 30 juvenile L. vannamei (0.20 ± 0.07 g), to achieve a stocking density of 150 shrimps/m2 and were maintained for an experimental period of 49 days. The 75 treatment presented the highest levels of ammonia and nitrite throughout the study, compared to the 150 and 300 treatments. The results showed that higher alkalinity favors biofloc formation and the establishment of nitrifying bacteria.  相似文献   

4.
A study to determine the effects of four stocking densities on growth and feed utilization of wild‐caught black sea bass Centropristis striata was conducted in a pilot‐scale recirculating tank system. The outdoor system consisted of 12 insulated fiberglass tanks (dia. = 1.85 m; vol. = 2.17 m3) supported by biological filters, UV sterilizers, and heat pumps. Subadults (N= 525; ×± SD = 249 ± 16.8 g) were stocked at densities of 4.6 fish/m3 (1.18 kg/m3), 16 fish/ m3 (3.91 kg/m3), 25.3 fish/m3 (6.83 kg/m3), and 36 fish/m3 (7.95 kg1m3), with three replicate tanks per treatment. Fish were grown under 35 ppt salinity, 21‐25 C, and under ambient photoperiod conditions. A commercial flounder diet containing 50% protein and 12% lipid was hand‐fed twice daily to satiation for 201 d. Mean (range) total ammonia‐nitrogen, 0.61 (0‐2.1) mg/L, nitrite‐nitrogen, 0.77 (0.04‐3.6) mg/L, and nitrate‐nitrogen 40.1 (0‐306) mg/L were significantly higher (P < 0.0001) in the 25.3 and 36 fish/m3 treatments than in the 4.6 and 16 fish/m3 treatments [0.19 (0.05‐0.5), 0.1 (0.24‐0.63), and 11.9 (1.3‐82.2) mg/L, respectively]. However, there were no significant differences (P > 0.05) in growth (RGR = 196.8‐243.1%; DWG = 2.55‐2.83 g/d; and SGR = 0.55‐0.61%/d), coefficient of variation of body weight (CwtV., = 0.24‐0.25), condition factor (K = 2.2‐2.4), feed consumption (FC = 1.45‐1.65%/d), and feed conversion ratio (FCR = 1.45‐1.52) among stocking densities. Final biomass densities on day 201 reached 3.48, 12.0, 21.1, and 27.2 kg/m3 at stocking densities of 4.6, 16, 25.3, and 36 fish/m3, respectively. Survival (83.8‐99.1%) did not differ among treatments. Apparent net protein retention (ANPR) was significantly higher (P < 0.005) for fish stocked at the lower densities of 4.6 and 16 fish/m3 (22.5‐23.7%) than for those stocked at 25.3 and 36 fish/m3 (21‐20.1%). There were no significant differences (P > 0.05) in apparent net energy retention (ANER = 55.9‐59.1 %) among stocking densities. Final whole body protein (15.3‐16.3%) and lipid (23.1‐26.4%) levels did not differ significantly (P > 0.05) among treatments. The results demonstrated that growth, survival, and feed utilization were not impaired under stocking densities ranging from 4.6‐36 fish/m3 (3.48‐27.2 kg/m3), despite a slight reduction in water quality at the higher densities. In addition, growth variation and final whole body protein and lipid levels were not influenced by these densities. The results suggest that black sea bass are tolerant of crowding and moderate variations in water quality during intensive culture in recirculating tank systems and that higher stocking densities are possible.  相似文献   

5.
A mathematical model is framed for a goldfish recirculating aquaculture system based on unsteady-state mass balance for prediction of the concentration of total ammonia nitrogen (TAN), nitrite-nitrogen (NO2-N), nitrate-nitrogen (NO3-N), dissolved oxygen (DO) and total suspended solids (TSS). The goldfish were stocked at 100 numbers per m3 of rearing water volume of 5 m3 tank capacity in the years 2009 and 2010 and the model was calibrated and validated. The recirculation flow rate was fixed at 29,000 L/day. The model parameters were estimated as kTAN (mg of TAN generated per kg of feed): 20,000, M (mortality rate): 0.002 day−1, α (percentage of feed conversion to suspended solids): 23.8, koxy (mg of oxygen required for fish respiration per kg of feed applied in unit time): 300,000, kb (partial nitrification in the culture tank): 0.86 and the reaction rate constants, k1 and k2: 84.65 day−1 and 42.03 day−1 respectively and temperature growth coefficient (TGC): 5.00 × 10-5. The model efficacy was adjudged by estimation of the coefficient of determination (R2), root mean square error (RMSE), Nash-Sutcliffe modelling efficiency (ENS) and graphical plots between predicted and observed values.  相似文献   

6.
草鱼养殖水体中参与氮转化途径的异养菌分析   总被引：1，自引：0，他引：1  
为分析草鱼池塘中参与氮代谢的异养细菌比例及其代谢途径,从杭州郊区取得4个草鱼池塘的水样,每个水样通过涂布随即挑选100株菌株进行定性显色试验,并据此选取11株异养菌进行16S rRNA序列分析。结果表明,4个草鱼养殖池塘中NH4+-N和NO2--N的平均水平分别为5.597 mg/L和0.135 mg/L。池塘中可培养的异养菌平均为3.26×105cfu/mL,其中的89.75%参与了氮的不同代谢途径,其中31.25%的氨化菌和33.50%NO3--N(NO2--N)还原菌参与了NH4+-N的生成,32.45%的氨氧化菌参与了NH4+-N的降低;NO2--N生成途径主要包括蛋白质直接转化(11.26%)、氨氧化(4.25%)和硝酸盐氮还原(10.75%),而NO2--N降低主要通过15.50%的亚硝酸氧化菌、8.75%的NO2--N还原菌和10.75%的反硝化菌实现。结果提示,草鱼养殖水体中存在大量的异养硝化菌参与不同的氮代谢途径,且产生氨氮的异养菌比例远高于去除氨氮的菌,这是草鱼养殖水体中氨氮含量易偏高的原因。同时,11株不同功能的异养菌16SrRNA鉴定结果为寡养食单胞菌(Stenotrophomonas)6株、假单胞菌(Pseudomonas)3株、克雷伯氏菌(Klebsiella)和肠杆菌(Enterobacter)各1株,而且细菌对氮源的利用具有菌株特异性。  相似文献   

7.
This study evaluated the zootechnical performance and enzymatic activity of Litopenaeus vannamei reared at different feeding frequencies during the nursery phase in biofloc system. The experiment consisted of four treatments, corresponding to the feeding frequencies of one, two, three and four times a day. Twelve‐day postlarvae (PL12) were stocked in 12 circular tanks at a density of 3,000/m2 for 35 days. These tanks were connected to a recirculation system supplied by a matrix tank where biofloc management was carried out. Water quality remained within acceptable limits for the species over the experiment. Food frequencies had no influence on survival (88.5–92.7%) and feed conversion ratio (1.5–1.7), but the final mean weight (0.43–0.56 g) was significantly higher in shrimp fed three times a day. This fact is probably associated with amylase (14.58 U/mg) and trypsin (23.84 U/mg) activities, as well as the significant increase of chymotrypsin (11.74 U/mg) and lipase (1.27 U/mg) in shrimp of this treatment at the end of culture period. Feeding three times a day provided the highest enzymatic activity and the best zootechnical performance of L. vannamei during the nursery phase in biofloc system.  相似文献   

8.
Results are presented of a zero‐discharge marine recirculating system used for the culture of gilthead seabream Sparus aurata. Operation of the system without any discharge of water and sludge was enabled by recirculation of effluent water through two separate treatment loops, an aerobic trickling filter and a predominantly anoxic sedimentation basin, followed by a fluidized bed reactor. The fish basin was stocked for the first 6 mo with red tilapia Oreochromis niloticus × O. aureus at an initial density of 16 kg/m3. During this period salinity was raised from 0 to 20 parts per thousand. Then, gilthead seabream, stocked at an initial density of 21 kg/m3, replaced tilapia at day 167 and were cultured for an additional 225 d. Non steady‐state inorganic nitrogen transformations occurred as a result of these salinity changes. After day 210, the system operated at all times with those water quality parameters considered critical for successful operation of mariculture systems, within acceptable limits. Thus ammonia, nitrite, and nitrate concentrations did not exceed 1.0‐mg total ammonia‐N/ L, 0.5‐mg NO2:‐N/L and 50‐mg NO3‐N/L, respectively. Sulfide levels in the fish basin were below detection limits and oxygen > 6 mg/L after the oxygen generator was added at day 315. Ammonia, produced in the fish basin and to a lesser extent in the sedimentation basin, was converted to nitrate in the aerobic trickling filter. Nitrate removal took place in the sedimentation basin and to a lesser extent in the fluidized bed reactor. Sludge, remaining in the sedimentation basin at the end of the experimental period, accounted for 9.2% of the total feed dry matter addition to the system. The system was disease‐free for the entire year and fish at harvest were of good quality. Water consumption for production of 1 kg of tilapia was 93 L and 214 L for production of 1 kg of gilthead seabream. Additional growth performance data of gilthead seabream cultured in a similar but larger system are presented. During 164 d of operation of the latter system, maximum stocking densities reached 50 kgl M3 and fish biomass production was 27.7 kg/m3. Relatively poor fish survival and growth resulted from occasional technical failures of this pilot system.  相似文献   

9.
《Aquacultural Engineering》2008,38(3):234-251
Convenient, economical, and reduced labor fish harvest and transfer systems are required to realize operating cost savings that can be achieved with the use of much larger and deeper circular culture tanks. To achieve these goals, we developed a new technology for transferring fish based on their avoidance behavior to elevated concentrations of dissolved carbon dioxide (CO2). We observed this behavioral response during controlled, replicated experiments that showed dissolved CO2 concentrations of 60–120 mg/L induced rainbow trout (Oncorhynchus mykiss) to swim out of their 11 m3 “growout” tank, through a transfer pipe carrying a flow with ≤23 mg/L dissolved CO2, into a second 11 m3 “harvest” tank. The research was conducted using separate groups of rainbow trout held at commercially relevant densities (40–60 kg/m3). The average weight of fish ranged from 0.15 to 1.3 kg during the various trials. In all trials that used a constant flow of low CO2 water (≤23 mg/L) entering the growout tank from the harvest tank, approximately 80–90% of the fish swam from the growout tank, through the transfer pipe, and into the harvest tank after the CO2 concentration in the growout tank had exceeded 60 mg/L. The fish that remained in the growout tank stayed within the area of relatively low CO2 water at the entrance of the transfer pipe. However, the rate of fish transfer from the growout tank to the harvest tank was more than doubled when the diameter of the transfer pipe was increased from 203 to 406 mm. To consistently achieve fish transfer efficiencies of 99%, water flow rate through the fish transfer pipe had to be reduced to 10–20% of the original flow just before the conclusion of each trial. Reducing the flow of relatively low CO2 water near the end of each fish transfer event, restricted the zone of relatively low CO2 water about the entrance of the fish transfer pipe, and provided the stimulus for all but a few remaining fish to swim out of the growout tank. Results indicate that the CO2 avoidance technique can provide a convenient, efficient, more economical, and reduced labor approach for fish transfer, especially in applications using large and well mixed circular culture tanks.  相似文献   

10.
False clownfish, Amphiprion ocellaris, is one of the most commercialized fish species in the world, highly produced to supply the aquarium market. The high stocking densities used to maximize fish production can increase ammonia and nitrite to toxic levels. In this study, A. ocellaris juveniles (1.20 ± 0.34 g) were exposed to six concentrations of ammonia ranged from 0.23 to 1.63 mg/L NH3-N and eight concentrations of nitrite (26.3–202.2 mg/L NO2 ?-N). The LC50- 24, LC50-48, LC50-72 and LC50-96 h were estimated to be 1.06, 0.83, 0.75 and 0.75 mg/L for NH3-N and 188.3, 151.01, 124.1 and 108.8 mg/L for NO2 ?-N. Analysis of gill lesions caused by sublethal concentrations of these nitrogenous compounds showed that both nitrogenous compounds induced tissue lesions such as hyperplasia of epithelium cells, hypertrophy of chloride cells and lamellar lifting to all concentrations tested. However, histopathological alterations were more conspicuous accordingly the increase of ammonia or nitrite in fish exposed to 0.57 mg/L NH3-N or 100 mg/L NO2 ?-N. Based on our results, we recommend to avoid concentrations higher than 0.57 mg/L of NH3-N and 25 mg/L of NO2-N in water.  相似文献   

11.
An optimal flow domain in culture tanks is vital for fish growth and welfare. This paper presents empirical data on rotational velocity and water quality in circular and octagonal tanks at two large commercial smolt production sites, with an approximate production rate of 1000 and 1300 ton smolt/yr, respectively. When fish were present, fish density in the two circular tanks under study at Site 1 were 35 and 48 kg/m3, and that in four octagonal tanks at Site 2 were 54, 74, 58 and 64 kg/m3, respectively. The objective of the study was twofold. First, the effect of biomass on the velocity distribution was examined, which was accomplished by repeating the measurements in empty tanks under same flow conditions. Second, the effect of operating conditions on the water quality was studied by collecting and analysing the water samples at the tank’s inlet and outlet. All tanks exhibited a relatively uniform water velocity field in the vertical water column at each radial location sampled. When fish were present, maximum (40 cm/s) and minimum (25–26 cm/s) water rotational velocities were quite similar in all tanks sampled, and close to optimum swimming speeds, recommended for Atlantic salmon-smolt, i.e., 1–1.5 body lengths per second. The fish were found to decrease water velocity by 25% compared to the tank operated without fish. Flow pattern was largely affected by the presence of fish, compared to the empty tanks. Inference reveals that the fish swimming in the tanks is a major source of turbulence, and nonlinearity. Facility operators and culture tank designers were able to optimize flow inlet conditions to achieve appropriate tank rotational velocities despite a wide range of culture tank sizes, HRT’s, and outlet structure locations. In addition, the dissolved oxygen profile was also collected along the diametrical plane through the octagonal tank’s centre, which exhibits a close correlation between the velocity and oxygen measurements. All tanks were operated under rather intensive conditions with an oxygen demand across the tank (inlet minus outlet) of 7.4–10.4 mg/L. Estimates of the oxygen respiration rate in the tank appears to double as the TSS concentration measured in the tank increases from 3.0 mg/L (0.3 kg O2/kg feed) up to 10–12 mg/L (0.7 kg O2/kg feed). Improving suspended solids control in such systems may thus dramatically reduce the oxygen consumption and CO2 production.  相似文献   

12.
Tropical and subtropical climatic conditions in India present an ideal and unique opportunity for being the leader in tropical marine finfish aquaculture. However, the problem persist due to non-availability of marine finfish seed for the culture. In response to this problem, broodstock development of different tropical marine finfishes for seed production was started. The present study was undertaken to design a recirculating aquaculture system (RAS) and studying their performance in managing the various water quality required for the marine finfish broodstock development and breeding. The design of RAS, developed in the present study, included a broodstock tank, egg collection chamber, electrical pump, rapid sand filter, venturi type protein skimmer and biological filter. Two RAS were designed, one was stocked with a demersal fish species, orange spotted grouper (Epinephelus coioides) and the other was stocked with a pelagic fish species, Indian pompano (Trachinotus mookalee) at the rate 1 and 0.5 kg/m3 with a sex ratio of 1:1 and 1:2 (female: male) respectively. Various physio-chemical parameters, viz, total ammonia nitrogen (TAN), nitrite, nitrate, pH, alkalinity, temperature, free carbon dioxide (CO2) and dissolved oxygen (DO) of both tank water were analyzed to assess the performance of recirculating aquaculture system in maintaining the water quality. Gonadal development of the fishes was assessed and the spawning performance was recorded and finally, economic performance of the system was also evaluated. During the entire experimental period, mean monthly total ammonia nitrogen was less than 0.07 and 0.06 mg L−1 and mean monthly nitrite was less than 0.02 and 0.01 mg L−1 in orange spotted grouper and Indian pompano RAS tanks respectively. The pH (7.8–8.2), DO (>4 mg/L) and alkalinity (100–120 mg/L) were found to be in optimum range in both recirculating aquaculture systems. Carbon dioxide was found to be nil during the entire experimental period in both the systems. In fact these levels were comparable or less than that is reported as the permissible limits for broodstock development. Indian pompano and Orange spotted grouper matured and spawning was obtained with production of fertilized eggs round the year. Economic evaluation showed the price of 10,000 fertilized eggs of orange spotted grouper to be US $ 1.33. The design of RAS devised in the present study is efficient in controlling and maintaining optimum water quality for broodstock development of both demersal and pelagic finfishes. The fishes stocked in RAS attained final maturation and round the year spawning was obtained.  相似文献   

13.
This experiment was conducted to study the effects of carbohydrates with different molecular sizes on growth performance, feed utilization and composition, activity of digestive enzymes, plasma and hepatic metabolites of jundiá (Rhamdia quelen). Triplicate groups of jundiá (4.08 ± 0.005 g) were stocked in 12 tanks with stocking density of 25 individuals per tank and fed for 40 days with four isonitrogenous diets (37%) and isocaloric diets (3,200 kcal/kg) containing fructose (FRU), sucrose (SUC), maltodextrin (MALDEX) or corn starch (CS). The results showed no significant differences for growth variables and digestive enzymes. Fish whose diet received maltodextrin showed higher levels of deposited body fat and hepatosomatic index. Moreover, the above‐mentioned treatment resulted in lower concentrations of glucose and cholesterol in the plasma of jundiá, higher levels of triglycerides, and lower reserves of glucose and liver glycogen. However, fish fed the starch‐based diet presented higher moisture content, crude protein deposition, and body protein retention coefficient. In that same treatment, the jundiá presented higher levels of plasma glucose and liver protein. In conclusion, the efficiency of using digestible carbohydrates in iso‐nutritional diets for jundiá depends on the size of their molecular structure. The corn starch was the best dietary carbohydrate source for jundiá, based on feed utilization and composition and greater synchronicity between energy utilization and protein synthesis.  相似文献   

14.
This study was conducted to determine the biological filtration capabilities of some culinary herbs co‐cultured with lemon fin barb hybrid in a nutrient film technique (NFT) recirculating aquaponic system. Lemon fin barb hybrid (Hypsibarbus wetmorei ♂ × Barbonymus gonionotus ♀) fingerlings were stocked in twelve 2‐tonne fibreglass tanks at 25 fish per tank and co‐cultured with Chinese celery (Apium graveolens var. secalinum Alef.), coriander (Coriandrum sativum) and peppermint (Mentha × piperita) for seven weeks. The impacts of the waste generated by the fish on the water quality, the filtration capability of the herbs and the ability of fish and herbs to retain nutrients (NPK) were also estimated. All the herbs showed water purifying potentials to varying degrees as significantly lower levels of nitrogenous compounds (NH3‐N, NO3‐N, NO2‐N) were observed after the herbal filtration. The plant growth seemed to be affected by their ability to absorb nutrients and consequently purify the culture medium. Interestingly, the lemon fin barb hybrid also showed significant differences in terms of weight gain, but the nutrient retention among fish treatments was not statistically different. The plants absorbed less phosphorus and potassium than the fish. After computing for the total system percentage of NPK recovered, nitrogen was the most retained nutrient. The peppermint showed superiority in terms of gross biomass and water purifying potential compared to the Chinese celery and coriander.  相似文献   

15.
One pilot-scale portable Nutrient Film Technique (NFT) aquaponic system has been designed, developed, and tested at ICAR-CIFA, Bhubaneswar for a period of 90 days (October to December 2018) to study the efficiency of the new design. The experimental setup has three separate units, each consisting of four major components, such as Fibreglass Reinforced Plastic (FRP) round fish culture tank (ø2.15 × 0.9 m) with operational capacity 2800 L, biofilter unit made up of Polypropylene (PP) of 100 L capacity, FRP rectangular hydroponics tank (4 × 0.9 × 0.35 m) having 2.64 m2 plantation area and High-density Polyethylene (HDPE) sump (ø0.6 × 0.7 m) of 200 L capacity. Implementation of custom designed and calibrated automatic water recirculation system gives an average flow rate of 94.7 L/h for continuous flow of nutrients from fish culture tank to hydroponics tank. The designed system harnesses gravity flow in 75 % of the cycle. For performance assessment, the system was initially stocked with 54 numbers of fish fry/m3 (153.7 g/m3) of pangas (Pangasius hypophthalmus) in culture tank and 27 marigold (Tagetes erecta) plants/m2 in hydroponics tank. Length and weight gain of fish were by 77.04 % and 397.2 % from initial, respectively, and marigold plant harvested 107 number of flowers/m2. The Total Ammoniacal Nitrogen (TAN) reduction in biofilter was found to be 61.97 %.  相似文献   

16.
This study investigated the secondary stress responses of Paralichthys orbignyanus exposed to ammonia and nitrite and after recovery. Fish were exposed to 0.12, 0.28, and 0.57 mg NH3‐N/L, or 5.72, 10.43, and 15.27 mg NO2‐N/L for 10 d followed by the same time length for recovery. Ammonia‐ and nitrite‐free water was used as a control treatment. Blood samples were collected after 1, 5, and 10 d of exposure and after recovery. Fish exposed to ammonia presented lower and higher glucose levels after 10 d of exposure and recovery, respectively. Ammonia induced initial and transient ionic disturbances and metabolic alkalosis. Nitrite exposure caused hyperglycemia, increased plasma K+ levels, and respiratory alkalosis, whereas metabolic acidosis was observed after recovery. Increased proportion of monocytes and/or granulocytes and reduced number of lymphocytes were demonstrated in fish exposed to 0.28 mg NH3‐N/L (Day 1) and 10.43 mg NO2‐N/L (Day 5) and after recovery in the 0.28 and 0.57 mg NH3‐N/L treatments. Exposure to ammonia decreased the proportion of granulocytes on Day 5. In conclusion, exposure to concentrations at 0.12 mg NH3‐N/L and 5.72 mg NO2‐N/L provoked physiological disorders in Brazilian flounder. Nonetheless, fish exposed to 5.72 mg NO2‐N/L following a 10‐d recovery period showed complete resumption of homeostasis.  相似文献   

17.
The effects of total ammonia (TAN; NH4++ NH3) on the reproductive performance, survival, growth and moulting of wild Penaeus paulensis (Pérez-Farfante) broodstock were studied to determine optimal rearing conditions. Based on previously established ‘safe levels’ for P. paulensis adults (3.4 and 4.2 mg L?1 TAN), two 46-day trials were performed. In the first trial, six females and four males were stocked in 700-L tanks under three treatments (0.37, 2.53 and 6.86 mg L?1 TAN) with at least two replicates per treatment. In trial 2, ammonia levels of 0.68, 1.55 and 2.62 mg L?1 TAN were assigned to three 6000-L tanks, each stocked with 36 females and 24 males. Ammonia only influenced the survival of females and the growth of males exposed to 6.86 mg L?1 TAN (0.21 mg L?1 NH3). No further effects of ammonia on moulting and reproductive performance were detected. The present results demonstrate that up to 2.62 mg L?1 TAN, coupled with 0.07 mg L?1 NH3 and 1.50 mg L?1 NO2, will not impair reproductive performance of P. paulensis. It is suggested that water quality for the maturation of P. paulensis may be maintained through lower daily water exchange rates instead of the usual high levels (150-300%) employed on penaeid shrimp maturation systems.  相似文献   

18.
A 10‐week feeding trial was conducted to determine the optimal requirement of cobia (Rachycentron canadum Linneaus) for dietary ascorbic acid (AA). Graded levels of L‐ascorbyl‐2‐polyphosphate (LAPP) were supplemented in basal diet to formulate six semi‐purified diets containing 2.70 (the control diet), 8.47, 28.3, 80.6, 241 and 733 mg AA equivalent kg?1 diet, respectively. Each diet was randomly fed to triplicate groups of fish in flow‐through plastic tanks (300 L), and each tank was stocked with 25 fish with average initial weight of 4.59 ± 0.36 g. Observed deficiency signs included poor growth, higher mortality and lower feeding rate (FR) in the fish of the control group. Fish fed the control diet had significantly lower weight gain (WG), lower feed efficiency ratio (FER) and lower tissue AA concentrations in fish liver and muscle. With the increase of dietary AA, the survival, WG, FER, hepatic and muscular AA concentrations of cobia significantly increased and then levelled off. The dietary AA requirement of cobia was estimated to be 44.7 mg kg?1 based on WG, 53.9 mg kg?1 or 104 mg kg?1 based on either hepatic or muscular AA concentration, respectively.  相似文献   

19.
A data set from commercial Atlantic salmon (Salmo salar L.) producers on production intensity and production strategies in smolt tanks (N = 63–94) was obtained during 1999–2006. The effects of production intensity on subsequent fish mortality and growth during the early sea phase (90 days) were examined by principal component analysis and subsequent generalized linear model analysis. Levels of accumulated metabolites (CO2, total ammonia nitrogen and NH3), and information provided by producers (production density (kg fish m3−1), specific water use (l kg fish−1 min−1) and oxygen drop (mg l−1) from tank inlet to tank outlet), were used as predictor variables. In addition, several other welfare relevant variables such as disease history, temperature during freshwater and sea stage; season (S1) or off-season (S0) smolt production; and the use of seawater addition during the freshwater stage were analyzed. No strong intensity effects on mortality or growth were found. CO2 levels alone (P < 0.001, R 2 = 0.16), and in combination with specific water use (R 2 = 0.20), had the strongest effect on mortality. In both cases, mortality decreased with increasing density. For growth, the intensity model with the most support (R 2 = 0.17) was O2 drop, density and their interaction effects, resulting in the best growth at low and high intensity, and poorer growth at intermediate levels. Documented viral disease outbreaks (infectious pancreatic necrosis and two cases of pancreas disease) in the sea phase resulted in significantly higher mortalities at 90 days compared with undiagnosed smolt groups, although mortalities were highly variable in both categories. The temperature difference between the freshwater stage and seawater had a small, but significant, effect on growth with the best growth in groups stocked to warmer seawater (P = 0.04, R 2 = 0.06). S0 and S1 smolt groups did not differ significantly in growth, but the mortality was significantly (P = 0.02) higher in S1 groups. Seawater addition as a categorical variable had no significant effects, but when analyzed within the seawater addition group, intermediate salinities (15–25 ppt) gave the best results on growth (p = 0.04, R 2 = 0.15). Production intensity had small explanatory power on subsequent seawater performance in the analyzed smolt groups. If anything, the analysis shows a beneficial effect of intensive production strategies on subsequent performance. Analysis of the various production strategies indicates better survival of S0 compared with S1 smolt groups, improved growth when stocked in seawater warmer than freshwater, and a negative effect of viral disease outbreaks on survival. The results clearly demonstrate the difficulty of extrapolating results from experimental work on fish welfare and production intensity variables to commercial production. On the other hand, the presented results may simply demonstrate that the traditional fish welfare criteria growth and mortality may not suffice to evaluate welfare consequences of suboptimal water quality or production strategies in the aquaculture industry.  相似文献   

20.
于 2005年 3月 5日 ~5月 3日连续监测了海水观赏鱼居室养殖循环系统的水质，研究该系统中三态氮的变化规律以及添加硝化细菌后对水质的影响。结果表明：1)试验初期氨氮的质量分数迅速上升， 在 1周内达到高峰(峰值2．56mg/L)，并在1．50mg/L的范围内维持 1周左右，此后迅速下降至0．01mg/L 左右，并一直维持在该水平直至试验结束。亚硝态氮的质量分数在氨氮的质量分数迅速回落时(约试验开始后 2周)呈现出直线上升的趋势，并在 3~3．5mg/L左右的水平上维持 2~3周时间(峰值为3．65 mg/L)，此后迅速下降至0．01mg/L以下，并一直维持在低水平直至试验结束。而硝酸盐的质量分数在整个试验期间基本保持稳定上升的趋势，至本试验末期，NO3 - -N的质量分数达到 15mg/L左右。2)系统的生物滤器需要 4~5周左右时间才能基本成熟，即氨氮和亚硝酸氮均降至 ＜0．01mg/L，到达安全的质量分数，适合海水观赏鱼健康生长。3)添加硝化细菌的试验组，氨氮和 NO3 - -N的质量分数变化与对照组基本相似，而 NO2 - -N的质量分数变化与对照组明显不同。试验组从高质量分数水平迅速下降的时间比对照组提前了约 1周。  相似文献   

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