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1.
This research reveals the applied engineering basis for determining the particle size and settling velocity distributions of solids generated while rearing wild-caught premature punctuated snake-eels (Ophichthus remiger) in a prototype recirculating aquacultural system. Settled solids were sampled from the bottom of the rearing tanks, and suspended solids were sampled before filtration within the drum filter and analyzed to characterize their settling velocity and particle size properties. These particle properties are considered bioengineering parameters since they will provide biological information to improve engineering solutions for RAS solids removal processes. The average settling velocity for the settleable solids in the rearing tanks was 2.89 ± 0.02 cm s−1, and the average particle size ranged between 7.32 ± 3.41 and 19.44 ± 8.58 mm. Suspended solids within the drum filters before filtration had an average settling velocity of 0.35 ± 0.11 cm s−1 and it was found that 69.93 % of the particles size was greater than 200 μm, 15.40 % were within the range of 120 μm and 90 μm sizes, and 6.53 % were between 70 μm and 40 μm sizes. The particle physical properties, settling curves, and particle sizes curves obtained from this experience represent valuable information to be used to improve engineering design of solids handling mechanisms, especially in marine land-based systems, and in this case, applied for rearing wild-caught punctuated snake-eels. The present investigation constitutes an advance in the knowledge of applied engineering to the design of a marine aquaculture fattening operation targeted to feed up wild-caught premature punctuated snake-eels to the point of sale or trade.  相似文献   

2.
The culture of the mulloway (Argyrosomus japonicus), like many other Sciaenidae fishes, is rapidly growing. However there is no information on their metabolic physiology. In this study, the effects of various hypoxia levels on the swimming performance and metabolic scope of juvenile mulloway (0.34 ± 0.01 kg, mean ± SE, n = 30) was investigated (water temperature = 22 °C). In normoxic conditions (dissolved oxygen = 6.85 mg l− 1), mulloway oxygen consumption rate (M·o2) increased exponentially with swimming speed to a maximum velocity (Ucrit) of 1.7 ± < 0.1 body lengths s− 1 (BL s− 1) (n = 6). Mulloway standard metabolic rate (SMR) was typical for non-tuna fishes (73 ± 8 mg kg− 1 h− 1) and they had a moderate scope for aerobic metabolism (5 times the SMR). Mulloway minimum gross cost of transport (GCOTmin, 0.14 ± 0.01 mg kg− 1 m− 1) and optimum swimming velocity (Uopt, 1.3 ± 0.2 BL s− 1) were comparable to many other body and caudal fin swimming fish species. Energy expenditure was minimum when swimming between 0.3 and 0.5 BL s− 1. The critical dissolved oxygen level was 1.80 mg l− 1 for mulloway swimming at 0.9 BL s− 1. This reveals that mulloway are well adapted to hypoxia, which is probably adaptive from their natural early life history within estuaries. In all levels of hypoxia (75% saturation = 5.23, 50% = 3.64, and 25% = 1 .86 mg l− 1), M·o2 increased linearly with swimming speed and active metabolic rate (AMR) was reduced (218 ± 17, 202 ± 14 and 175 ± 10 mg kg− 1 h− 1 for 75%, 50% and 25% saturation respectively). However, Ucrit was only reduced at 50% and 25% saturation (1.4 ± < 0.1 and 1.4 ± < 0.1 BL s− 1 respectively). This demonstrates that although the metabolic capacity of mulloway is reduced in mild hypoxia (75% saturation) they are able to compensate to maintain swimming performance. GCOTmin (0.09 ± 0.01 mg kg− 1 m− 1) and Uopt (0.8 ± 0.1 BL s− 1) were significantly reduced at 25% dissolved oxygen saturation. As mulloway metabolic scope was significantly reduced at all hypoxia levels, it suggests that even mild hypoxia may reduce growth productivity.  相似文献   

3.
This paper provides a detailed observation of pond hydrodynamics. Bathymetry and aerator deployment largely control the hydrodynamic regime. Aerators drive pond circulation, which is resisted by bottom and bank friction. Hydrodynamic friction is characterized by sediment grain size. One particular pond is offered as a proxy representative of Australian mariculture ponds in general: Pond X. The pond had been stocked with P. monodon at densities in the range 25–35 m−2 about ten times during the period from 1989 to 1995. Observations were made in the year 1996. The site was on the east coast of Australia at 18° south latitude. The location was sheltered by a mountainous offshore island, such that winds effecting the pond averaged 2.3 m s−1. Water exchange occurred at a rate of about 8.3% of pond capacity per day. Pond X was found to be rectangular, 120 m long and 87 m wide. The banks were found to slope between 1:1.5 and 1:7.6, with an average slope near 1:3. The pond was shallowest in one corner, where depth was 834 mm, and drained diagonally with 1872-mm maximum water depth. Aeration was provided by a total of six 1.5-kW machines, comprised of two of the paddlewheel type and four of the propeller-aspirator type. Each machine was found to deliver 200 N of horizontal thrust into the pond water column. The combined effect of the aerators created a circulation current averaging about 11 cm s−1 around the pond periphery. The central region of the pond was found to have a fluctuating velocity of less than 1 cm s−1. The mass-average size of pond soil and sediment was found to vary from 25 μm in the central region to 250 μm at the banks and where the bottom was swept by paddlewheels.  相似文献   

4.
The most common type of rearing unit for rainbow trout produced in the US is the flow-through raceway. A water treatment structure, which can be readily retrofitted into existing raceways, was designed to create rotational currents to aid in the concentration and collection of particulate waste material in situ. The designed structure, referred to as the Appurtenance for Settleable Solids In-raceway SeparaTion (ASSIST), incorporated a drain line which diverts a small fraction of the raceway flow to continuously remove the uneaten feed and fecal material from the collection area located at the effluent end of the raceway. Continuous removal of the collected particulates minimizes the leaching of soluble material from the solids into the water column. Based on scale model tests using analogous waste material, the ASSIST is expected to remove 40–50% of the settleable solids generated in commercial rainbow trout aquaculture while diverting 5–10% of the raceway flow.  相似文献   

5.
Purified microcystin-LR (MC-LR) was administered via the dorsal aorta to brown trout, Salmo trutta L., or rainbow trout, Oncorhynchus mykiss (Walbaum), and, within 24 h, a dose of 300 μ g MC-LR kg–1 caused increased activities in the blood by enzymes originating mainly from the liver, i.e. lactate dehydrogenase (LDH) and alanine transaminase (ALT). A dose of 75 μ g MC-LR kg–1 significantly increased liver enzyme activities in the blood of brown trout at 24 h, but was without effect on rainbow trout, whereas 25 μ g MC-LR kg–1 had no effect on blood LDH or ALT activities in either species. However, histopathological analysis of liver from both species following administration of the lowest toxin dose showed hepatocyte swelling and necrosis. Liver damage was more severe in brown trout compared to rainbow trout following administration of 300 μ g MC-LR kg–1, showing disruption of the parenchymal architecture. After 48 h, there was a dose-dependent increase in the hepatosomatic index in both species. It is concluded that brown trout are less tolerant to MC-LR than rainbow trout.  相似文献   

6.
A commercially available heterogeneous, solid-phase tube enzyme-linked immunoassay (ELISA) was modified and validated for the measurement of serum cortisol in rainbow trout Oncorhynchus mykiss . The assay is accurate and precise. Resting and stress-elevated serum cortisol concentrations were measured in rainbow trout with a sensitivity of 1.5 ng/ml. Fish held in net-pens at a density of 0.4 kg/m3/cm had a resting cortisol level of 16.5 ± 3.8 ng/ml (mean ± SE). At 3 h postdisturbance, serum cortisol levels were not affected by the removal of fish from adjacent net-pens with dip nets or by the use of 200 mg/L tricaine methanesulfonate (MS-222) as an anesthetic for obtaining samples. However, an acute stress (60 s removal from water) elevated serum cortisol levels to 73.7 ± 9.4 ng/ml.  相似文献   

7.
Fish sperm collected by stripping males is frequently contaminated by urine. In this study, carp milt mixed with urine (0.5–7.5% of volume) was studied in order to evaluate the changes of some motility parameters (percentage of motile spermatozoa, velocity and beat frequency) and the ATP content of spermatozoa. In the absence of urine contamination, spermatozoa had an ATP content in the range of 8–9 nmol/108 spermatozoa, an initial velocity of 100–160 μm s−1 and a flagellar beat frequency around 30–50 Hz, 10 s after a 1/2000 dilution in an activating medium (45 mM NaCl, 5 mM KCl, 30 mM Tris–HCl, pH 8.0, osmolality <160 mosM kg−1). In contrast, when milt was contaminated with 7.5% of urine for 1 h, the ATP content was 4–5 nmol/108 spermatozoa and most spermatozoa had low initial velocity (30–100 μm s−1) and flagellar beat frequency (10–30 Hz). It appears that the low osmolality of urine was responsible for the degradation in the quality of carp spermatozoa by an early activation in the collecting tube which induced an early reduction of the intracellular ATP store. From a practical point of view, milt contamination by urine during stripping can be avoided by first pressing the abdomen before sampling and then collecting the remaining urine by means of a catheter introduced into the urinary bladder.  相似文献   

8.
Abstract. The pathogenicity of Renibacterium salmoninarum to carp, Cyprinus carpio L., and rainbow trout, Salmo gairdneri Richardson, was investigated. All carp injected with 4·8 × 108 cells/fish, or 4·8 × 107 cells/fish survived for 38 days. R. salmoninarum was isolated from all moribund fish, but not from the kidney of surviving fish, although R. salmoninarum antigen was detected in several of these fish by the dot blot assay. On the other hand, mortality in rainbow trout was 95% in the fish injected with 4·8 × 108 cells/fish, and 15% in those which received 4·8 × 107 cells/fish. R. salmoninarum antigen was detected by the dot blot assay in all surviving rainbow trout. The number of R. salmoninarum cells was immediately decreased by carp or rainbow trout serum, and the serum bactericidal activity of carp was higher than that of rainbow trout. Carp blood leucocytes had higher phagocytic activity than those of rainbow trout.  相似文献   

9.
Controlling the concentration of bioflocs is one of the main concerns in aquaculture systems with Biofloc Technology (BFT). Biofloc accumulation deteriorates the water quality and can negatively affect the production rates of the farmed river shrimp. This study describes and characterizes the settling velocity distribution of bioflocs generated with the addition of two carbon sources (molasses and chancaca) when applying the BFT for the rearing of the river shrimp Cryphiops caementarius. This study revealed that bioflocs generated with different carbon sources have different settling velocity curves. Regarding the mass fraction settling velocities, there were significant differences (P < 0.05) for mean solids fraction at similar withdrawn times between molasses and chancaca. The average settling velocities for bioflocs were 0.1044 ± 0.1224 cm s−1 for molasses and 0.1131 ± 0.1225 cm s−1 for chancaca. Therefore, a settling device operating with a given overflow rate will more efficiently remove bioflocs generated with chancaca than with molasses. The settling velocity curves obtained in this research contain valuable information to select appropriate devices for bioflocs and suspended solids removal in aquaculture systems with BFT.  相似文献   

10.
Antifungal agents are essential for the maintenance of healthy stocks of fish and their eggs in intensive aquaculture operations. In the USA, formalin is the only fungicide approved for use in fish culture. However, hydrogen peroxide and sodium chloride have been granted low regulatory priority drug status by the United States Food and Drug Administration (FDA) and their use is allowed. We evaluated the efficacy of these fungicides for controlling fungal infections on rainbow trout eggs. A pilot study was conducted to determine the minimum water flow rate required to administer test chemicals accurately in Heath incubators. A minimum water flow rate of 7.6 1 min−1 was necessary to maintain treatment concentrations during flow-through chemical exposures. The antifungal activity of formalin, hydrogen peroxide, and sodium chloride was evaluated by treating uninfected and 10% fungal-infected (Saprolegnia parasitica) rainbow trout eggs (Oncorhynchus mykiss) for 15 min every other day until hatch. There were no significant differences among treatments in percent hatch or final infection for uninfected eggs receiving prophylactic chemical treatments. Eggs of the negative control group (uninfected and untreated) had a mean hatch exceeding 86%. All chemical treatments conducted on the infected egg groups controlled the spread of fungus and improved hatching success compared with the positive control groups (infected and untreated). Formalin treatments of 1000 and 1500 μl l−1 and hydrogen peroxide treatments of 500 and 1000 μl l−1 were the most effective. Sodium chloride treatments of 30 000 mg l−1 improved fry hatch, but the compound was less effective at inhibiting fungal growths compared with hydrogen peroxide and formalin treatments.  相似文献   

11.
The present study evaluates if abdominal dis-tension caused by a water-filled stomach in seawater farmed rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., could be provoked experimentally by live chilling in sea water (0.5 °C). Fifty rainbow trout and 50 salmon were visually classified, either as normal or suffering from the condition. Prior to chilling, no rainbow trout or salmon suffered from a water-filled stomach. During chilling, 25% of the rainbow trout and 2.5% of the salmon developed water-filled stomach. Affected rainbow trout had significantly higher blood plasma osmolality and significantly lower body weight than normal trout. The frequency of trout with a water-filled stomach increased significantly with increasing chilling time and increasing plasma osmolality. The regression coefficients revealed that the proportion of affected rainbow trout in-creased by 0.82% h−1 of chilling and by 0.46% per unit increase in mosmol L−1. The present study revealed that abdominal distension in seawater farmed rainbow trout was far more severe than in Atlantic salmon and could be provoked experimentally by osmoregulatory stress. This is consistent with the observation that water-filled stomach appear only occasionally in seawater farmed Atlantic salmon.  相似文献   

12.
Video cameras are employed on net pen fish farms for monitoring food pellet levels near the cage bottom. Herein, the accuracy of a new machine-vision system for the identification of a feed-wastage event and its response time are reported. Research involved novel tests and definitions, video footage recorded under different stocking and environmental conditions, and numerical filters to reduce the effects of misclassifications and patchiness of the pellet wastage record on overall system accuracy. Single-frame food pellet detection accuracy was based on the difference between computer-generated and actual frame counts of pellets greater than 30 pixels in size. A pellet wastage event was defined as a median of three or more visible pellets per frame. During tests on still video frames from different feeding events, the system missed 0.1±0.1 to 1.3±0.4 pellets frame−1, and miss-classified as pellets 0±0.1 to 2.3±0.5 objects frame−1 (n=264). Most missed pellet images were on top of fish images. Waste matter accounted for 65% of the misclassifications, while particles associated with poor camera maintenance accounted for approximately 24%. The average response time to a pellet wastage event was 5.1 and 11.4 s for sampling rates of 2 frames s−1 and 0.5 frames s−1, respectively (n=20 different pellet wastage events). The longest response time (26 s) occurred when fish were amassed against the camera and/or covering pellets. Using appropriate camera lens, camera positioning and/or ‘warning’ software can address fish-interference problems.  相似文献   

13.
A simulation model to analyze the water flow and sediment transport in aquaculture raceways was developed using a computational fluid dynamics (CFD) software package. The simulation was used to evaluate the efficiency of solids settling in the quiescent zone of existing trout raceways. This efficiency was based on the percentage of solids removed, which corresponds to the percentage of solids introduced into the raceway that settle in it, with settling taking place primarily in the quiescent zone.

The raceway selected for model validation was a rectangular concrete raceway 30.0 m long, 3.0 m wide, 0.9 m deep, with a slope of 0.01. The raceway included a quiescent zone of approximately 5.3 m in length, which was separated from the rearing area by a screen. The water flow rate through the raceway was approximately 0.058 m3/s. Velocity measurements were recorded at 230 stations along the raceway using an acoustic Doppler velocimeter, for comparison with the results obtained from the simulations.

For the purpose of simulating sediment transport, six groups of particles were used to account for the total suspended solids. The sizes of the particles selected were based on an experimentally determined distribution for solids from a similar raceway, and were 692, 532, 350, 204, 61, and 35 μm for Groups 1–6, respectively. The particle density for each size was assumed to be 1150 kg/m3. Values of the percentage of solids removed for the different particle sizes were 100.0% for the largest particles, and 54.7, 0.9, and 0.1% for the three smallest particles, respectively. This methodology of analyzing the raceway sediment transport in terms of its percentage of solids removed based on CFD simulations can also be used to examine raceway design alternatives for improving the particle removal efficiency.  相似文献   


14.
Abstract. Viral haemorrhagic septicaemia (VHS) is reported for the first time in sea-water cultured rainbow trout. Heavy mortalities with typical signs and lesions A VHS virus (serotype 1) was isolated from the diseased fish. The mortalities were caused only by the VHS virus and 80 days post transfer of trout to sea-water the mortalities reached 85%, of the initial population.
The disease was experimentally transmitted to rainbow trout, both in sea-water 3·104 pfu/ml of virus or by intramuscular injection of various doses of VHS1 (7·101 7·104 or 7·104 pfu per fish). Death occurred in all infected groups and started earlier in sea-water. Typical signs of VHS were observed in moribund fish. Viral multiplication was demonstrated to have occurred in fish organs.  相似文献   

15.
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.  相似文献   

16.
The aim of the presented investigation was to test the sensibility of macroalgal aquaculture in offshore wind farms in the North Sea and to find arguments for the choice of appropriate sites among the planned wind farms. Based on experience with an offshore aquaculture farm of Laminaria saccharina conducted in 2002, we assessed the maximum hydrodynamic forces affecting farmed algae by applying the model software “WaveLoad”. Drag measured in a towing tank was considerably higher on algae with a more ruffled margin and wider blade collected from sheltered environments than on flat and narrow farmed Laminaria despite comparable blade areas. Drag varied according to frond size, current velocity and acceleration reaction. Dislodgement of laminarian holdfasts and the forces necessary to break the stipe depended on blade length and surface area. Neither did our measured nor our calculated values of drag exceed those forces, provided the algae had been grown in a current > 1 m s− 1. Even in storm conditions with maximum current velocities of 1.52 m s− 1 and wave heights of up to 6.4 m can cultivated L. saccharina withstand the high energy environment.  相似文献   

17.
Nutritional strategies to reduce both phosphorus (P) and nitrogen (N) excretion relative to growth of rainbow trout were tested in a 2 × 3 factorial experiment. The two factors were `dietary P level' and `dietary lipid level.' Reduction in dietary P from 14 to 8 g kg–1 dry diet was achieved by partial substitution of dietary fish meal with a combination of full-fat soyabean meal, corn gluten and spray-dried blood meal. Triplicate tanks of 35 rainbow trout per tank were fed experimental diets for 16 weeks and grew from approximately 40 to 250 g, in 15 °C spring water. All tanks were fed the same percent biomass per day. Diets were isonitrogenous, and dietary energy varied with dietary lipid. Diet digestibility data and results of the experiment were used to construct N and P budgets for the fish fed the various diets. A reduction in dietary fish meal from 500 to 200 g kg–1 dry diet, corresponding to a reduction in dietary P from 14 to 8 g kg–1 dry diet, resulted in >50% reductions in both solid and dissolved P waste, but did not affect growth, feed efficiency ratio (FER) or sensory characteristics of rainbow trout. Increasing dietary lipid from 170 to 310 g kg–1 dry diet led to higher growth rate and FER, and lower total N waste relative to weight gain, but did not change protein retention. Increasing dietary lipid level increased deposition of lipid in whole bodies of rainbow trout, and resulted in discernible differences in sensory characteristics of trout fillets.  相似文献   

18.
A hydraulically integrated serial turbidostat algal reactor (HISTAR) for the mass production of microalgae was designed, constructed and preliminarily evaluated. The 9266-l experimental system consists of two enclosed turbidostats hydraulically linked to a series of six open continuous-flow, stirred-tank reactors (CFSTRs). The system was monitored and controlled using GENESIS process control software. A production study was preformed using Isochrysis sp. (C-iso) to assess system stability and production potential under commercial-like conditions. The study was performed at the following target system parameters: system dilution rate of 0.49 per day, pH 7.6, NITROGEN=10 mg l−1, PHOSPHORUS=2 mg l−1, and artificial illumination (photosynthetic photon flux density) from 1000 W metal halide LAMPS=800 μmol s−1 m−2. At steady state conditions, daily harvested algal paste was 1454 g (wet), mean areal system PRODUCTIVITY=47.8±3.04 g m−2 per day (17.1±1.09 g C m−2 per day) and mean CFSTR6 DENSITY=105.5±6.71 mg l−1.  相似文献   

19.
An in vitro method was developed to assess the digestibility of phosphorus in 12 plant and animal feed ingredients for rainbow trout Oncorhynchus mykiss (Walbaum). The method simulates the gastrointestinal tract of the rainbow trout with regard to pH and gastrointestinal enzymes. Phosphorus solubility was measured after acid digestion (pH 3) with and without gastric enzymes, after alkaline digestion (pH 9) with and without intestinal enzymes, and after a two-step process involving acid and alkaline digestion. Commercially available digestive enzymes from mammals were compared with digestive enzymes from rainbow trout. Correlating in vitro digestibility with in vivo digestibility showed that acid digestion with both commercial enzymes ( r 2=0.98, P  < 0.05) and trout enzymes ( r 2=0.94, P  < 0.05) predicted the in vivo digestibility of animal feed ingredients. Alkaline digestion with both enzyme systems (commercial r 2=0.79; trout r 2=0.74, P  < 0.05) or without ( r 2=0.82, P  < 0.05) enzymes predicted the in vivo digestibility of ingredients from animal byproducts but not those from plant products. The in vitro digestibility with two enzyme steps (acid and alkaline) predicted in vivo digestibility of plant and animal ingredients ( r 2=0.79 for commercial enzymes and r 2=0.74 for trout enzymes) better than did one-step acid or alkaline digestion.  相似文献   

20.
The power law in particle size analysis for aquacultural facilities   总被引：1，自引：0，他引：1  
Fine particles tend to accumulate in recirculating aquacultural facilities, which can lead to serious fish health problems. The literature indicated that in many particle systems, the particle size distribution may be accurately represented by a two-parameter, hyperbolic power-law function, dN/dl=Al−β.

The purpose of this paper is to investigate whether this observation holds for aquacultural facilities. Particle size distribution data from four research establishments were examined, using 14 data sets, comprising 11 aquacultural systems, and covering three species of salmonids and one of striped bass. In the data examined, the exponent, β, varied from 2.9 to 4.6, with one sample reaching as high as 6.3. Correlation coefficients varied from 0.998 to 0.975. Larger exponents, indicating a greater number of fine particles, appear to dominate recirculating aquaculture systems.

The results strongly suggest that a hyperbolic distribution is valid for aquaculture systems. The usefulness in this technique is that once a worker has established the exponent from the distribution of particle sizes at any given point in his facility, an estimate of particulate contributions by size to the total particle number, surface area and volume/mass concentration can be obtained.  相似文献   


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