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1.
An economic analysis was performed of a proposed commercial-scale 20-ha saltwater pond culture operation for Florida red tilapia in Dorado, northern Puerto Rico. The analysis was based on actual cost and production data from a commercial-scale hatchery, pilot-scale grow-out trials conducted in six 0.2-ha saltwater (avg. = 22.7 ppt) ponds at the Dorado facility and on wholesale market prices ($4.96–5.18/kg) fetched by dressed-out (gilled, gutted and scaled) product. The proposed 20-ha growout facility is comprised of 25 0.8-ha earthen ponds, each supplied with sea water, brackish well water, drainage and aeration, which account for 60.8% of the capital costs. Ponds are stocked with fingerlings (0.85 g avg. wt.) at a density of 3.0 fish/m2 (30,000/ha), and are harvested at 160 and 220 d, at an average weight of 545 g for a total yield of 11,445 kg/ha per crop. Imported feed ($0.55/kg), processing and distribution ($0.50/kg) and sex-reversed fry ($0.11/fry) are the highest variable costs, accounting for 30.7%, 15.4% and 13.9%, respectively, of the total annual costs. Salaries and benefits, and depreciation represent the highest fixed costs, accounting for 8.4% and 5.5%, respectively, of the total annual costs. Under these conditions, a wholesale price of $4.55/kg results in a positive cash flow by year eight, and a breakeven price, internal rate of return (IRR), net present value (NPV) and discounted payback period (DPP) of $4.08/kg, 7.6%, ($235,717) and >10 yr, respectively, suggesting that the proposed 20-ha operation is not economically feasible under these conditions. The proposed enterprise is marginally feasible if stocking density is increased to 3.5 fish/m2 while at 4.0 fish/m2 economic outlook is favorable. Costs can be lowered considerably by targeting production and market variables most sensitive to profitability indices, using locally-prepared feeds, and vertically integrating hatchery and growout operations.  相似文献   

2.
To calculate the potential for cage aquaculture to create economic opportunities for small-scale investors on the Volta Lake, Ghana, a local NGO with technical support from the Government of Ghana ran two trials (one of four and one of six units) of small-scale cage aquaculture in the town of Dzemeni. Cages were built locally from available materials at a cost of approximately US$1000 per 48 m3 cage. An indigenous line of Nile tilapia, Oreochromis niloticus, was stocked either as mixed sex (first trial) or all-males (second trial) at an average rate of 103 fish/m3 and grown on locally available pelleted feeds for approximately six months. Total costs averaged US$2038 per six-month production cycle. Gross yield ranged from 232 to 1176 kg/cage, averaging 460 kg/cage (9.6 kg/m3). Final average weight of mixed sex populations (253.05 ± 47.43g) was significantly less than of all-males (376.7 ± 72.30g). Likewise, percentage of fish over 300 g at harvest was significantly lower in mixed-sex (38.3%) compared to all-male (75.7%) populations. Mortality resulting primarily from poor handling during transport and stocking averaged 70% and was a major determinate of production and profitability. To break even, harvested biomass of fish needed to exceed 15 kg/m3. At 25 kg/m3, small-scale cage aquaculture generated a net income of US$717 per cage per six months (ROI = 30.2%) on revenues of US$3,500. Water quality in the area surrounding the cages was not negatively affected by aquaculture at the scale tested (5 tons of feed per six months).  相似文献   

3.
This study evaluated the effect of the density at harvest on the performance and profitability of hatchery‐reared spotted rose snapper cultured in cages. The fish were stocked at harvest densities of 15, 20, and 22 kg/m3 in cages of 222 and 286 m3. More than 39,000 snapper fingerlings with an initial weight of 14 g were stocked. The fish were fed an extruded diet and cultured over a 360 d period. The thermal growth coefficient ranged from 0.04 to 0.05 and survival was 95% for all treatments, with the highest final weight (436.8 g) observed for fish reared at a density of 20 kg/m3. The allometric value b indicated that hatchery‐raised, cage‐cultured snapper were heavier than their wild counterparts. The major costs were feed (ranging from 44.7–45.9%), labor (22.4–32.6%), and seed costs (20.2–26.1%). The total production cost ranged from US$ 6.5 to US$ 7.5/kg. The baseline scenario was not economically feasible. However, a 10% increase in the sales price resulted in increases in the internal rate of return (183%) and net present value (US$ 97,628.9). These results suggest that L. guttatus has the potential for commercial production in cages.  相似文献   

4.
We evaluated the effect of varying cage stocking density (60, 90 and 120 fish m?3) and feeding duration (10, 30 and 60 min) in a cage‐cum‐pond‐integrated system on growth performance, water quality and economic benefits in Labeo victorianus culture. Interactions between stocking density and feeding duration significantly (P < 0.05) affected the fish growth performance and yields in the cages‐cum‐pond system. Stocking density of 60 fish m?3 resulted in the highest growth in cages and in ponds regardless of the feeding duration, but produced lower yields than at stocking density 90 fish m?3. The lowest Apparent Food Conversion Ratio (AFCR) in cages occurred at stocking density of 60 fish m?3 and feeding duration of 30 min. Growth performance in the open ponds declined with increased feeding duration of the caged fish. Survival in cages and in the open ponds decreased with increased cage density, but was not affected by feeding duration. Low dissolved oxygen were recorded, at stocking density of 120 fish m?3, the lowest DO occurred when feeding of caged fish lasted 60 min. Growth performance, water quality and economic benefits in Labeo victorianus culture positively respond to interaction between stocking density and feeding durations.  相似文献   

5.
The paper compares two prawn (Penaeus monodon) brood stock systems—land-based tanks and marine offshore pens. Construction costs and annual maintenance and operating costs total US$1,430 and $2,550 for the tank and $1,500 and $3,680, respectively, for the pen. The 12 m3 ferrocement tank requires power for a 24-hour seawater flowthrough and can stock 50 animals/run for a projected yearly production of 8×106 nauplii for 1.2 × 106 juveniles (0.1 to 0.5 g body weight). The 16×16×4 m pen made of bamboo and nylon net materials can accommodate 300 brood stock/run with a projected annual production of 30 × 106 nauplii or 4.5 × 106 juveniles. Discussion includes general requirements, mortality and maturation rates, and criteria for choosing a brood stock system.  相似文献   

6.
The factors affecting production of estuary grouper, Epinephelus salmoides, in floating net cages are discussed. The concept of economic production in cage culture is outlined. Economic production of estuary grouper could be achieved by providing a suitable culture site with good water quality; ensuring proper farm management and regular maintenance of cages; preventing disease and ensuring efficient treatment; providing optimum stocking density, a balanced diet, optimal feeding frequency; manipulating fish behaviour by providing artificial hides; and manipulating physiological characteristics, e.g. by the use of growth promoters.The paper futher describes environmental parameters, such as dissolved oxygen content, water temperature, salinity, water current, bacteria count, pH, and bottom sediments, as important factors in site selection. Their effects on the growth and production of fish are discussed and their optimal levels determined. The problems involving management and maintenance of the farm are also outlined. The main problem in cage culture is fouling which demands considerable labour and money for cage maintenance. Other problems such as predators, poaching, and cannibalism are discussed at length. It is suggested that by manipulation of stocking density, production could be increased. The optimal stocking rate was found to be 60 fish/m3 which gives a high yield of marketable fish. Stocking could be further intensified by providing artificial hides using used car tyres. The net production could be increased by 230% if hiding space of 251 cm3 per fish was provided and the stocking density increased to 156 fish/m3. Although formulated feeds enhanced growth by 27.1% over that of groupers fed on trash fish, the production cost was much higher, rendering the use of formulated feeds alone uneconomical for commercial fish culture. Growth promoters such as 17α-methyltestosterone and nitrovin have been found to promote growth of young estuary grouper by 43.4 and 62.8%, respectively.Using various combinations of culture techniques, it was shown that net production could be increased from 23.76 kg/m3 using conventional culture methods to 136.75 kg/m3 with a combination of hiding space, heavy stocking, appropriate feeding frequency and formulated feeds incorporating growth promoters. The production time was also shortened considerably from 6 months to 2.7 months.Cost-benefit analysis of the eight culture techniques tested indicated that the production cost could be reduced from US$2.00/kg with conventional methods to as low as US$1.28/kg using a sophisticated method. However, based on current market proces, the conventional culture technique was still economically feasible, as the net income over total capital costs was 33.3%. Improvements of the conventional culture technique will increase the ratio of net income over total capital costs by 1–3 times.  相似文献   

7.
Abstract.— The aquaculture performance of mutton snapper Lutjanus analis raised in floating net cages was assessed by measuring their growth, survival, and feed conversion rates during a growout trial conducted in a 3.2‐ha saltwater lake in the Florida Keys, Florida, USA. Approximately 10,500 hatchery‐reared finger‐lings were stocked in two circular, high‐density polyethylene (HDPE) net cages of 7‐m diameter × 7‐m deep (300 m2) and 10‐m diameter × 7‐m deep (600 m3) dimensions. Cages were stocked at 25 fish/m3 (3.2 kg/m3) and 5 fish/m3 (0.72 kg/m3), respectively. Fish grew from a mean of 16.5 g to 302.8 g (25.6 cm TL) in 246 days in the former cage and from a mean of 42.3 g to 245.6 g (23.8 cm TL) in 178 d in the latter cage. Growth rates in weight were best expressed by the following exponential equations: cage 1 (high stocking density): W = 20.716 e0.0112x (r2= 0.83); cage 2 (low stocking density): W = 38.848 e0.0118x (r2= 0.81). Length‐weight data indicate that hatcheryraised, cage‐cultured mutton snapper are heavier per unit length than their wild counterparts. There was no significant difference (P < 0.05) between the slopes of the two lines, indicating that fish in the two cages grew at the same rate. The length‐weight relationships for mutton snapper stocked in cages 1 and 2 are expressed, respectively, by the equations W = 0.000009 L 3.11 (r2= 0.99) and W = 0.000005 L 3.22 (r2= 0.97). Overall feed conversion rate for both cages combined was 1.4. Approximately 10% of the fish sampled exhibited some degree of deformity, particularly scoliosis. Overall survival rate was 70%. Results suggest that L. analis has potential for aquaculture development in net cage systems.  相似文献   

8.
An economic analysis of a hypothetical small‐scale marine recirculating aquaculture system (RAS) is conducted for ongrowing small, wild black sea bass Centropristis striata at the University of North Carolina Wilmington, Center for Marine Science (UNCW‐CMS) aquaculture facility in Wrightsville Beach, North Carolina (NC). The analysis is based on production data from field trials and marketing data from the sale of tank‐grown product. The growout facility consists of four 16.7‐m3 (dia. x ht. = 5.58 × 1 m) fiberglass tanks supported by state‐of‐the‐art RAS components, including particle traps and swirl separators, drum screen filter, trickling biological filter, UV sterilizer, heat pump, protein skimmer, and oxygen cone. Wild‐caught, above minimum legal size black sea bass (24.2 cm TL, 350 g, 0.77 lb) were purchased from a commercial fisherman for $3.14/ kg ($1.4011b), stocked at a density of 21.1 kg/m3, and grown to a final weight of 1 kg (2.24 lb) in 200 d at 23 C resulting in 1.8 production cycles per year. Fish were fed a commercial pelleted diet ($0.94/kg; $0.42/Ib) with a feed conversion ratio of 1.5. Final harvest density was 60 kg/m3 (0.50 lb/gal), and total harvestable weight was 3,982 kg (8,919 Ibs) of fish per cycle, or 6,760 kg (15,022 lb) per year. The economic analysis assumes that the facility owner manages and operates the system on coastal property zoned commercial/industrial, where full strength seawater is available on demand from natural sources. Under the base case scenario, initial investment in construction and equipment is $84,506 (10‐yr life), fish are grown to a harvestable weight of lkg/fish (2.24 lb/fish), product price (farm gate basis) is $10.10/kg ($4.50/lb), and breakeven price is $7.02/kg ($3.13/lb). Depreciation, fingerlings, interest paid, electricity, and feed, account for 19.6%,17.4%, 16.9%, 16.6%, and 12.3%, respectively, of total annual costs. Measures of financial performance for the base case, 10‐yr scenario are: annual return to management, $18,819; net present value (5% discount rate), $145,313; internal rate of return on initial investment, 37%; and discounted payback period on initial investment, 3.2 yr. Sensitivity analysis showed that product price changes have the largest impact on annual returns, while changes in daily growth rate, initial weight, and survival have a strong impact on financial performance. Moderate effects are seen with changes in fingerling costs, feed costs, feed conversion ratio (FCR), final weight, and interest rates.  相似文献   

9.
ABSTRACT

Fish cage culture is an intensive, continuous-flow fish farming system, allowing intensive exploitation of water bodies with relatively low capital investment. This study aimed to determine the production function of Nile tilapia, Oreochromis niloticus, in cages; the profit-maximizing biomass at 300–400 and 500–600 fish per m3 for cages of different volumes; and the influence of water body conditions in fish performance. Feed intake, survival rate, and water temperature were monitored daily; dissolved oxygen, pH, and transparency of water were monitored each 15 days. Caged tilapia were fed daily on commercial, floating pellets (32% crude protein) at 0900, 1300, and 1700, and feeding rate was adjusted based on weight gain and survival rate. Data were analyzed statistically by ANOVA (P = 0.05) and regression analysis; the Mitscherlich function was chosen to represent the production function. Carrying capacity of both stocking densities reached 200 kg/m3 and no differences were found (P > 0.05) regarding accumulated biomass and individual average weight over time. The larger stocking density yielded larger accumulated biomass and had better feeding efficiency and no differences between individual average weights of fish at both densities were observed (P > 0.05). Profit-maximizing biomass at 500–600 fish/m3 was 145 kg/m3 and at 300–400 fish/m3 was 121 kg/m3. Cage farming of Nile tilapia at 500–600 fish/m3, individual average weight 283 g, presented many advantages: optimization of space and production time, better feed efficiency, higher fish production per unit volume of cages, and increased profitability.  相似文献   

10.
Split-pond aquaculture systems are being implemented by United States (US) catfish farmers as a way to improve production performance. The split-pond consists of a fish-culture basin that is connected to a waste-treatment lagoon by two water conveyance structures. Water is circulated between the two basins with high-volume pumps (water circulators) and many different units are being used on commercial farms. In this study circulator performance was evaluated with four different circulating systems. Rotational speeds ranged from 0.5 to 3.5 rpm for a twin, slow rotating paddlewheel; 12.5 to 56.5 rpm for a paddlewheel aerator; 60 to 240 rpm for a high-speed screw pump; and 150 to 600 rpm for an axial-flow pump. Water flow rates ranged from 8.6 to 77.6 m3/min and increased with increasing rotational speed. Power input varied directly with flow rate and ranged from 0.24 to 13.43 kW for all four circulators. Water discharge per unit power input (i.e., efficiency) ranged from 3.5 to 70.9 m3 min−1 kW−1 for the circulators tested. In general, efficiency decreased as water flow rate increased. Initial investment cost for each circulator and complete circulating system ranged from US $5850 to $22,900, and $15,335 to $78,660, respectively. The least expensive circulator to operate was the twin, slow-rotating paddlewheel, followed by the paddlewheel aerator, high-speed screw pump, and axial-flow pump. Our results show that four different circulating systems can be effectively installed and used to circulate water in split-ponds. However, water flow rate, rotational speed, required power input, efficiency, initial investment cost, and operational expense varied greatly among the systems tested. Long term studies are underway to better define the relationship between water flow rate and fish production in split-ponds. That information will help identify the water circulating system most appropriate for split-pond aquaculture.  相似文献   

11.
Abstract

Rainbow trout, Oncorhynchus mykiss, were raised in culture cages (1 m3) to determine the effect of stocking density on growth, survival, and percentage of market-size fish. Large fingerling rainbow trout (20-25 cm, 232 g average weight) were stocked into six cages located in a 0.4-ha pond. Two stocking densities (100 or 200 fish/cage) were used, and fish were grown for 140 days (2000-April 2001). Average total harvest weight (35.0 kg) in the low-density cages was approximately one-half the average total harvest weight (61.2 kg) in the high-density cages. Average weight gain (11.7 kg to 15.1 kg) and feed conversion (1.2 to 1.5) were also smaller for the low-density cages. Average survival was 96.7% for the low-density cages and 94.2% for the high-density cages, with the percentage of market-size fish (< 29 cm) averaging 50.3% and 52.0%, respectively. Production costs for the actual experiment and the revenues from fish sold at the end of the study were collected. An enterprise budget based on the experimental results for the two densities was developed to determine if a culture operation of this size would produce a net return. Production costs and revenues from the experiment resulted in a large negative return (-$3,124) and high breakeven price ($13.53/kg).  相似文献   

12.
The experimental rearing of T. nilotica in 1-m3 cages floating in Lake Kossou, Ivory Coast, was performed between March 1974 and April 1975. The fish were fed water-stable pellets (24.7% protein), the daily ration generally varying between 6 and 3.4% of the ichthyomass present. Fingerlings (9–55 g each) were stocked at densities of 200–400 fish/m3. They reached commercial size (more than 200 g) within 4–6 months, depending on the biomass present in the cage (stocking density and average individual weight of fish), as well as on limological conditions. The average annual mortality was 5.9%. Annual production varied from 36 to 64 kg/m3. The feed conversion rate averaged 2.8. A reduction of the daily ration for fish larger than 40 g reduced this value.Fingerlings should average at least 20–30 g in weight at initial stocking of the cage. Two crops a year can then be easily realized. If only male fish are reared, three harvests per year appear to be possible, increasing the annual cage production of fish close to 200 kg/m3 with proper management.The possible development of T. nilotica cage culture is actually hampered due to the lack of adequate fish feed available commercially, and to the lack of sufficient quantities of calibrated fingerlings throughout the year.  相似文献   

13.
Experimental culture of the native Amazonian fish tambaqui, Colossoma macropomum, in fixed cages was carried out over a period of 8 months, in Lake Urubu (Rio Grande do Norte, Brazil), to assess the viability of fixed cage culture of tambaqui and to test the influence of diet on growth rates. Nine synthetic net cages (1 m3) were each stocked with 45-day-old fish (mean weight 3 g; mean total body length 51 mm) at a density of 34 fry m–3. During the first 2 months of culture, fish were fed a balanced formulated feed on an as-fed basis at the rate of 5% body weight day–1. During months 3–8 this continued for fish in treatment 1 while those in treatment 2 were fed tropical regional fruits, on a wet weight basis at the rate of 5% body wt day–1. Fish in treatment 3 were given no supplementary feed. Monthly biometric measurements were made on all fish. Fixed cage fish culture was shown to be a viable and simple technique. Survival in all treatments was 100%. With balanced supplementary feed, production was 14.4 kg m–3, compared with 4.9 kg m–3 and 2.1 kg m–3, respectively, in the treatments where fish were fed with fruits and were not given any supplementary feed.  相似文献   

14.
The main aim of the study was to decide the effect of specific water consumption (L/kg/min) and feed load per water flow (g/m3) on the water quality parameters pH, CO2, total ammonia nitrogen (TAN) and suspended solids (SS) in two large semi-closed containment systems (S-CCS). The reported production parameters (range) in the two S-CCS were specific water consumption (q): 0.04–0.47 L/kg/min and feed load per water flow: 9.0–64 g/m3. The study period was split in two sub-periods; January–May (4.4–7.5 °C), and June–September (7.5–13.2 °C) before a regression model was used to determine the relationship between production intensity (q, feed load) and water quality (pH, CO2). With the acceptable level of CO2 defined as ≤10 mg/L, the model predicted a minimum specific water consumption (L/kg/min) between 0.07 (winter) and 0.2 (summer). The predicted maximum feed load per water flow (g/m3) was between 35 (summer) and 45 g/m3 (winter). These calculated limits for production intensity were close to the values earlier reported for smolt or post-smolt production in large, onshore tanks.  相似文献   

15.
We used a 50‐year (1961–2010) daily record of precipitation and evaporation in a hydrological model to simulate ground water withdrawal for the foodfish grow‐out phase of ictalurid catfish culture in northwest Mississippi, USA. The model quantified the effects of seepage, reusing water for multiple years, and managing water levels to capture rainfall (drop‐fill water management). Selecting sites with relatively impervious soils and reusing water for multiple years had large impacts on annual water use, and combining those practices with drop‐fill water management reduced simulated groundwater withdrawal to less than 60 cm year?1 compared with more than 450 cm year?1 for the least conservative scenario. Water conservation measures reduced estimated costs of pumping ground water from ~$1150 ha?1 year?1 for the least conservative set of water‐use variables to less than $110 ha?1 year?1 for the best set of water conservation practices. Efficiency of pumped water use was dramatically improved by intensifying production in the foodfish grow‐out phase. Combining water‐conservation practices with production intensification improved the water use index from 9.18 m3 kg?1 for foodfish grow‐out ponds with the least conservative set of practices to 0.28 m3 kg?1 for ponds built on soils with negligible seepage, managed with a 22.9‐cm drop/7.6‐cm fill, drained every 10 years, and producing 15 000 kg of catfish ha?1 year?1. When simulated ground water use for the best set of water conservation practices in foodfish grow‐out ponds was combined with estimates of ground water used for fingerling production and water used in producing grain‐based feedstuffs, total consumptive water use index for catfish culture was estimated at ~2.7 m3 kg?1. This index is competitive with most other types of animal agriculture. Efficient water use in catfish farming is easily achieved under commercial conditions using existing simple technologies.  相似文献   

16.
The main objectives of this study were to approximate the maximum yield and evaluate size dispersion of stocker size largemouth bass, Micropterus salmoides reared in a semi‐closed recirculating system for 60 days. Fingerlings with an average body weight of 36.7 g were utilized for the study. An experimental system consisting of 18 square plastic tanks (165 L) equipped with a radial flow settler, a sump, a moving bed filter, a centrifugal pump, a rapid sand filter, a down‐flow oxygen saturator and a UV sterilizer was utilized for the trial. The system was operated semi‐closed, accounting for a daily exchange rate of 30–50% of total system water volume. Experimental stocking densities were 4.5, 9.1, 18.8, 36.5, 54.6 and 73 kg m?3 with three replicates per treatment. At the end of the experimental trial, largemouth bass showed acceptable feed conversion (1.00–1.48), specific growth rate (1.16–1.45% day?1) and survival rate (81.8–96.6%) in all treatments, displaying the highest performance at an initial stocking density range of 18–36 kg m?3. Based on a piecewise regression model with breakpoint analysis, maximum yield of largemouth bass fingerlings should not exceed 70 kg m?3. As stocking density increased, relatively more underweight fingerlings were produced with a higher uniformity of fatness.  相似文献   

17.
A simple floating hatchery system with partially submerged tanks (bags made of flexible, plastic-coated fabric) was used to rear the larvae of Penaeus indicus. A total of 1.96 million active nauplii were reared in 6000-l tanks at average densities of 67 nauplii and 42 nauplii/l of tank capacity. Development time from spawning to metamorphosis was 9 days and the average survival rate of nauplii to age PL6 was 49%. From age PL6, post-larvae were reared in nursery net cages (6 × 3 × 0.6 m) in the sea. At densities of 50 000–60 000 post-larvae/cage, the average survival rate from age PL6 to age PL20–22 was 78%; from age PL20–22 to age PL37–44 at densities of 25 000/cage it was 83%.One batch of juveniles was stocked in a prawn pond at age PL27 and another was stocked at high densities in two sizes of net cages at age PL37–50. The prawns grown in the pond reached a mean size of 9 g after 76 days (at age PL103). In large net cages (5 × 5 × 2.5 m) stocked at a density of 80/m2, prawns reached a marketable size of 9.8 g after 113 days (at age PL157) with an average survival rate of 32%.Based on these results, the costs of producing post-larvae and juveniles using the floating hatchery and nursery net cage system and of producing live prawns of marketable size by net cage culture were calculated. Modifications in the net cage culture techniques employed are recommended to improve growth and survival rates and reduce production costs.  相似文献   

18.
Growth, net production, and survival rates of milkfish cultured with Gracilariopsis bailinae at two stocking density combinations (T1– 30 fingerlings 100‐m?2 pond+1‐kg G. bailinae 4‐m?2 net cage, T2– 30 fingerlings 100‐m?2 pond+2‐kg G. bailinae 4‐m?2 net cage) in brackish water earthen ponds over four culture periods were determined. The control (T3) was stocked at 30 fingerlings 100‐m?2 pond. Specific growth and production rates of G. bailinae were also calculated. There were no significant differences in mean growth, survival, and net production rates of milkfish between the three treatments. Irrespective of stocking singly or in combination with G. bailinae, significantly higher mean growth and mean production rates for milkfish were obtained during the third culture period of year 1 than those obtained from the other culture periods. Survival rates were not significantly different among the four culture periods. There were no significant differences in mean specific growth and mean net production rates between the two stocking densities of G. bailinae. Significantly higher mean specific growth and mean net production rates of red seaweed were also obtained during the third culture period of year 1 than those obtained from other culture periods. The production of milkfish and red seaweed was higher during the dry season. Growth rates of milkfish was positively correlated with temperature and salinity, while net production rates were positively correlated with temperature and total rainfall, but was inversely correlated with dissolved oxygen. G. bailinae growth and net production rates were positively correlated with water temperature and salinity. Results show that milkfish can be polycultured with G. bailinae grown in net cages in brackish water ponds at stocking density combination of 30 fingerlings 100‐m?2 pond+1‐kg G. bailinae 4‐m?2 net cage.  相似文献   

19.
Cage‐pond integration system is a new model for enhancing productivity of pond aquaculture system. A field trial was conducted using African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) in cages and carps in earthen ponds. There were four treatments replicated five times: (1) carps in ponds without cage, (2) tilapia at 30 fish m?3 in cage and carps in open pond, (3) catfish at 100 fish m?3 in cage and carps in open pond, (4) tilapia and catfish at 30 and 100 fish m?3, respectively, in separate cages and carps in open pond. The carps were stocked at 1 fish m?2. The cage occupied about 3% of the pond area. The caged tilapia and catfish were fed and the control ponds were fertilized. Results showed that the combined extrapolated net yield was significantly higher (P < 0.05) in the catfish, tilapia and carps integration system (9.4 ± 1.6 t ha?1 year?1) than in the carp polyculture (3.3 ± 0.7 t ha?1 year?1). The net return from the tilapia and carps (6860 US$ ha?1 year?1) and catfish, tilapia and carps integration systems (6668 US$ ha?1 year?1) was significantly higher than in the carp polyculture (1709 US$ ha?1 year?1) (P < 0.05). This experiment demonstrated that the cage‐pond integration of African catfish and Nile tilapia with carps is the best technology to increase production; whereas integration of tilapia and carp for profitability.  相似文献   

20.
Abstract

This study tested the Kuwaiti new indoor tilapia hatchery using the recirculating system, and compared its production costs with those in the flow‐through system. Breeders were stocked at 4 fish/m2 at 1: 3 male: female sex ratio. Seeds were harvested every two weeks for a period of 1.5 years. Seed production ranged from 45–52 seed/m2/d and 105–130 seed/kg female/d. Water quality parameters in the different components stayed below lethal concentration.

Analysis of the capital and operating expenses revealed that the new recirculating system cost 9.4 cents per fry compared with 11.0 cents in the flow‐through system. Operating expenses accounted for 67.14% of the total annual costs. Salary and wages were the major cost item (74.87%) of the operating expenses.

The cost of producing 0.5‐g fry was 6.2 cents per fry. With the use of more spawning and fry rearing tanks, production can be increased from 630,000 to 735,000 1.0‐g fry or 950,000 0.5‐g with a corresponding decrease in the costs per fry to 7.3 cents and 5.7 cents, respectively.  相似文献   

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