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1.
Water exchange is routinely used in shrimp culture. However, there are few, if any, systematic investigations upon which to base exchange rates. Furthermore, environmental impacts of pond effluent threaten to hinder further development of shrimp farming in the U.S. The present study was designed to determine effects of normal (25.0%/d), reduced (2.5%/d) and no (0%/d) water exchange on water quality and production in intensive shrimp ponds stocked with Penaeus setiferus at 44 postlarvae/m2. Additional no-exchange ponds were stocked with 22 and 66 postlarvae/m2 to explore density effects. Water exchange rates and stocking density influenced most water quality parameters measured, including dissolved oxygen, pH, ammonia, nitrite, nitrate, Kjeldahl nitrogen, soluble orthophosphate, biochemical oxygen demand, phytoplankton and salinity. Reduced-exchange and no-exchange treatments resulted in reduced potential for environmental impact. Mass balance of nitrogen for the system indicates that 13–46% of nitrogen input via feed is lost through nitrification and atmospheric diffusion. Growth and survival were excellent in ponds with normal exchange, reduced exchange, and a combination of low density with no water exchange. A combination of higher stocking density and no water exchange resulted in mass mortalities. Mortalities could not be attributed to a toxic effect of any one water quality parameter. Production was 6,400 kg/ha/crop with moderate stocking density (44/m2) and reduced (2.5%/d) water exchange and 3,200 kg/ha/crop with lower stocking density (22/m2) and no water exchange. Results indicate that typical water exchange rates used in intensive shrimp farms may be drastically reduced resulting in a cost savings to farms and reduced potential for environmental impact from effluent.  相似文献   

2.
Intensive Culture Potential of Penaeus vannamei   总被引:3,自引:0,他引:3  
Tank and pond rearing studies were conducted to assess the potential for intensive culture of Penaeus vannamei in South Carolina. Postlarvae were stocked in intensive nursery tanks at 500/ m2. Growth and survival were compared for shrimp reared in control fiberglass tanks and in tanks with artificial substrates (fiberglass screen). Addition of substrate improved survival (82% versus 58%), but not growth. Juvenile shrimp (mean weight, 1.3 g) from the nursery trial were stocked into 6 m diameter tanks at densities of 10, 20 and 40/m2. Growth rate was inversely related to stocking density, with mean sizes of 33.9, 32.5, and 26.7 g attained at the low, medium, and high densities respectively after 168 days. At harvest, standing crop biomass averaged 225.6, 442.0, and 685.4 g/m2 for the three densities. To further test the intensive culture potential, two 0.1 ha ponds were stocked with hatchery-reared postlarvae at densities of approximately 40 and 45/m2. The ponds were managed intensively using paddlewheel aerators and water exchange averaging 16–17%/day. The ponds were harvested after 138 and 169 days and yielded 6,010 kg/ha of 16.7 g (mean weight) shrimp and 7,503 kg/ha of 17.9 g shrimp, respectively. Average production was 6,757 kg/ha with a food conversion of 2.51. These data suggest good potential for intensive pond culture of P. vannamei in South Carolina and other areas of the continental United States.  相似文献   

3.
Nursery production may be enhanced by the addition of artificial substrate to increase the surface area upon which shrimp graze and to serve as refuge. The objective of this study was to assess the effects of the artificial substrate, AquaMatsTM, on the performance of postlarval Pacific white shrimp Litopenaeus vannamei stocked at three densities. Eighteen 230-L tanks were stocked with 10-d postlarvae (mean weight < 0.01 g). Six treatments were evaluated and consisted of shrimp stocked at three densities (778 shrimp/m2, 1,167 shrimp/ m2, and 1,556 shrimp/m2) with and without access to artificial substrate. Shrimp in all treatments received a commercial diet ad libitum . After 6 wk, shrimp were harvested from each nursery tank, counted, and batch weighed. Mean final weight, survival, production, feed conversion ratio, and water quality parameters were analyzed by 2-way ANOVA. There were highly significant ( P < 0.001) density and substrate effects on final weight, but there was no significant interaction effect. Final weight was 26.0, 17.4, and 34.5% greater in treatments with substrate than without substrate when stocked at 778, 1,167, and 1,556 shrimp/m2, respectively. There was no significant density, substrate, or interaction effect on survival or water quality. Mean survival was ± 89.1% for all treatments. Increased shrimp growth in the presence of added substrate was likely due to the availability of attached particulate organic matter on the AquaMatsTM that served as an additional food source. Results from this study indicate that artificial substrate can be used to mitigate the potential negative effects of high stocking density on growth of L. vannamei in nursery systems.  相似文献   

4.
Abstract. A preliminary study was conducted to assess the performance of the tilapia, Oreochromis spilurus (Günther), cultured in seawater cages at different stocking densities during the nursing and rearing phases. The stocking densities tested were 200, 400 and 600 fish/m3 during the nursing phase and 100, 200, and 300 fish/m3 during the rearing phase.
In both growth phases, no significant differences (P>0.05) were observed among the different stocking densities on the mean individual final weight, daily growth rate, feed conversion ratio and survival rate. Yields in cages stocked with 400 and 600 fish/m3 during the nursing phase, however, were significantly (P<0.05) higher compared with cages stocked with 200 fish/m3. No significant differences (P>0.05) were observed between 400 and 600 fish/m3. A density of 600/m3 is therefore considered to be optimum for the nursing phase.
Yields of cages during the rearing phase increased significantly (P<0.01) with the increase in stocking density. After grading the fish, however, no significant differences (P>0.05) were observed when only fish bigger than 150g were considered. The occurrence of exophthalmia (cataract) was observed in two of the four replicates at the highest stocking density (300 fish/m3) during the rearing stage. Therefore, a stocking density of 200 fish/m3 is considered optimum for the rearing phase.  相似文献   

5.
Abstract. Six groups of tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)(mean weight. 20·45 ± l·5g), were reared in 0·34m3 fibreglass tanks at different stocking densities (105, 195, 285, 375, 465 and 555 specimens/m3 water) for 84 days. The objective of the study was to determine the effect of various stocking densities on the growth, nutrition, biochemical composition and survival of M. nemurus. The lowest growth rate appeared in fish at the highest density and the highest was observed in fish stocked in moderate density of 285 and 375 fish/m3 water. Fish production was also lower at relatively low stocking densities of 105 and 195 fish/m3. Food conversion ratio (FCR), protein efficiency ratio (PER) and biochemical composition of M. nemurus indicate that there exists an optimum stocking density which lies between 285 and 375 fish/m3.  相似文献   

6.
Abstract The geographic distribution of the Atlantic white shrimp Penaeus setiferus is in coastal waters from New York to Florida and around the Gulf of Mexico. Beside its value to commercial fisheries, this shrimp is sold as bait for recreational fishing. Previous data suggest that demand for live bait shrimp cannot be satisfied by commercial fleets. A 120-d trial was designed to study production of bait size P. setiferus at high densities in eight small outdoor ponds in south Texas. A 24–1 fractional factorial design was applied to study the effects of postlarval (PL) density (350 and 700 shrimp/m2), feed type (A and B), and water circulation methods (with and without airlift pumps or center pond dividers) on shrimp growth, survival and yield. No significant differences in survivals or yields were found between treatments (P = 0.2). Feed type ( P = 0.011), airlift pumps ( P = 0.021), and center dividers ( P = 0.026), had significant impacts on shrimp growth rates. Density effect on growth was not statistically significant ( P = 0.055). This study demonstrated that 6-d-old postlarvae can be stocked at 700 per square meter and reached a bait size (6.2 g) in 94 d with a 73.6% survival and a yield equivalent to 31,300 kg/ha when offered a commercial shrimp feed. A preliminary economic analysis based on this data suggests that operating a bait shrimp farm in Texas with two crops/yr will show profitability within 7 to 12 yr with an internal rate of return of 6.5 and 17.6%, respectively.  相似文献   

7.
A 34-day study was conducted to estimate the effect of stocking density on growth, biomass, and yield of harvestable animals in red swamp crawfish, Procambarus clarkii (Girard). Juvenile crawfish were stocked at l, 2, 4, 8, and 16 crawfish per m2 into plastic-lined metal pools planted with rice ( Oryza sativa ) with three replicate pools at each density. Crawfish averaged 35 ± 1.5 mm (SE) total length at the time of stocking.
Growth in total length and weight was significantly affected by density ( P < 0.01), ranging from 91.5 mm and 20.7 g for crawfish stocked at 1 per m2 to 62.5 mm and 6.3 g for crawfish stocked at 16 per m2. The total crawfish biomass ranged from 20.7 g per m2 for crawfish stocked at 1 per m2 to 88.7 g per m2 at 16 per m2. The portion of that biomass made up of harvestable sized animals (>75 mm total length) ranged from 100% at 1 per m2 to 0.7% at 16 per m2. Gross revenues per ha were projected for crawfish yields at each stocking density with and without a graded product.  相似文献   

8.
Abstract. The aim of this research was lo evaluate the effect of density and feeding level (initially 8 or 16kg/m3 and 1·3% or 2% of present biomass respectively) on productive traits, meat composition and water quality output in farmed rainbow trout, Oncorhynchus mykiss (Walbaum). Individual fish growth shows significant differences in relation to density and feeding level; feed conversion rate is positively Influenced by the lower feeding level and low rearing density. At low density, specific growth rate, protein efficiency ratio and coefficient of variation of individual final weights are more favourable than at high density. Dry matter and lipid composition of meat are positively affected by feeding level; whereas no differences are recorded on the amino acid and fatty acid profiles. Water quality shows differences due to density (NO3 and NH4+) and feeding level (NO2, NH4+ and P).  相似文献   

9.
Shrimp were grown under ideal management conditions during two distinct seasons of the year at stocking densities used most often in Honduras with the objective of evaluating the usefulness of high protein diets. A randomized design in 2 × 2 factorial arrangement was used to test a diet composed of either 20 or 40% crude protein in earthen ponds that were stocked with juvenile Penaeus vannamei at 5 to 11/m2. The study was repeated during wet and dry seasons. Dietary protein level had no significant effect ( P > O .05) on survival, yield, or average weight of shrimp at either density during either season. Higher stocking rates yielded significantly greater shrimp production during both seasons. Mean shrimp weight in high density ponds was significantly lower than mean shrimp weight in low density ponds during the wet season, but there was no significant weight difference because of stocking density during the dry season. Mean survival was significantly lower at the higher stocking rate during the dry season. Net income was negative during the dry season, particularly at the high stocking density. Mean production was 240% greater in the wet season than in the dry season. Diets offered P. vannamei stocked at 5 to 11/m2 should contain no more than 20% protein, regardless of season. Higher dietary protein levels increase costs and waste nitrogen without resulting in greater shrimp yields. The high stocking density might increase profitability in the wet season, but long term sustainable production may be more feasible at lower stocking rates because of reduced nutrient wastes.  相似文献   

10.
The effects of four levels of diffused aeration (0, 6, 12, and 24 hours/day) and two stocking densities (400 and 600 fish/m3) on the culture performance of caged Florida red tilapia were evaluated in 1 m3 cages in a 2 ha watershed pond on St. Croix, U.S. Virgin Islands. Fish obtained a nutritionally-complete (36% protein), floating feed from demand feeders for 143 to 146 days. Diffused aeration had no significant ( P > 0.05) effect on fish growth, survival, feed conversion, and production in cages. Combined across all levels of diffused aeration, fish stocked at 400/cage had a greater growth rate (2.21 vs. 1.97 g/day), larger final body weight (370 vs. 335 g), and a lower feed conversion ratio (1.69 vs. 1.80) than fish stocked at 600/cage ( P < 0.05). The final biomass of fish stocked at the higher density (181 kg/m3) was greater than at the lower density (140 kg/m3). The enhancement of water exchange rates by diffused aeration did not increase tilapia growth rate or production in cages.  相似文献   

11.
Abstract.— The effect of stocking prawns Macrobrachium rosenbergii at increasing densities in ponds with Nile tilapia Oreochromis niloticus reared at low density was evaluated. Twelve 0.01-ha earthen ponds were stocked with 1 tilapia/m2 and 0, 2, 4, or 6 postlarvae prawn/m2. Three replicates were randomly assigned to each prawn density. Postlarval prawns were stocked a week prior to tilapia juveniles and both were harvested 175 d after the beginning of the experiment. Tilapia final average weight, survival, production, and food conversion rates did not differ significantly among treatments ( P > 0.05); the averages were 531 g, 67%. 3,673 kg/ha, and 1.91, respectively. Prawn survival rates did not differ for the three stocking densities (mean 90%). However, final weight and production were significantly different ( P < 0.05) as follows: 34.0, 23.0, and 14.7 g and 639, 909, and 818 kg/ha, respectively for 2. 4, and 6 prawns/m2 densities. Stocking densities up to 6 prawn/m2 did not affect tilapia production and required neither additional feeding nor significant changes in management. The polyculture system allowed an increase in total production with the same amount of supplied feed, thus improving the system sustainability.  相似文献   

12.
Abstract. During the period June 1982-84 hatchery-reared brown trout, Salmo trutta L., fry were Stocked into stretches of the Owendoher. a trout nursery stream on the east coast of Ireland. These experiments were designed to examine the survival of stocked fry and to estimate the carrying capacity of the system. During the first year fry were stocked into sectors already supptorting wild fish at densities normal for the system. In the following year fry numbers were artificially reduced prior to stocking with the hatchery-reared fish. Mortality of the stocked fry was high after release with less than 33% of the fish surviving beyond the first 3 weeks. No stocked fish survived after October 1982. In the second year, however, 2-9% of the fish survived. The best survival rates were achieved where wild fry numbers were lowest. Regardless of the initial stocking density the various experiments yielded autumn fry densities (0.07-0.7 fish/m2) similar to those at unstocked sites (0.1-0.62 fish/m2).
Stocking did not increase recruitment to the 1+ group and again 1+ densities (0.15-0.35 fish/m2) similar to unstocked sites (0.07-0.39 fish/m2) were obtained at the end of each year. These results suggest that spawning and recruitment in the Owendoher yield population densities approaching the maximum carrying capacity of the stream. The system appears to support a maximum summer fry density in the region of 1 fish/m2 and a maximum autumn density of 0.7 fish/m2.  相似文献   

13.
Abstract.
The study was conducted to develop guidelines for high-density overwintering of tilapia in tanks using warm underground sea water. Seawater-acclimated fish of 20 g were stocked in 36 tanks at 250, 500 and 750/m3. Water flow was regulated at 0.1 and 0.2 l/kg fish/min. Fish were fed at the rates of 0.75% and 1.0% of biomass per day.
After 135 culture days, the mean individual weight gain and specific growth rate decreased, whereas feed conversion increased significantly ( P <0.0001) with the increase in stocking density. The condition factor at 500 and 750 fish/m3 was significantly lower ( P <0.0005) than at 250 fish/m3. However, stocking density had no significant effect on the survival rate. Significantly better specific growth rate, condition factor and feed conversion were observed at a water flow rate of 0.2 l/kg fish/min than at 01 l/kg fish/min. Significantly higher mean individual weight gain, specific growth rate, and survival rate were observed at 1.0%/day than at the 0.75%/day feeding rate. The findings indicate that the optimum stocking density for overwintering tilapia in tanks using warm underground sea water is 750 fish/m3 with a water flow rate of 0.1 l/kg fish/min and a feeding rate of 0.75%/day.  相似文献   

14.
Recirculating raceway systems were examined for their potential as a method for the intensive culture of the marine shrimp Penaeus vannamei Boone. The systems consisted of fiberglass raceways 38 m3 (13.7 m ± 2.4 m ± 1.16 m) and 28 m3 (13.7 m ± 2.4 m ± 0.85 m) each equipped with a vertical screen biofilter, foam fractionators and an ultraviolet ozone generator. All of the systems were enclosed in a commercial greenhouse. Four preliminary growout experiments and two growout experiments with stocking densities of 970 shrimp/m3 and 2,132 shrimp/m3 were completed.
Temperature, pH and salinity remained constant throughout the experiments. Unionized ammonia levels remained below 0.2 mg/L. Nitrite levels ranged from 0.1 to 1.0 mg/L. The 2,132/m2 stocking density resulted in 48% survival, food conversion ratio (FCR) of 1.8 and an average size of 10.8 g. The 970/m3 stocking density resulted in 82% survival, FCR of 2, and an average size of 14 g. Production was 11.4 kg/m3 (114 tons/ha) and 11.0 kg/m3 (110 tons/ha) for the high and low stocking densities, respectively.  相似文献   

15.
Abstract.— Two growth trials utilizing Penaeus vannamei and Penaeus setiferus were conducted at densities of 28.4, 56.8, 85.2, 113.6, 170.4, 227.3 and 284.1/ m2 in an indoor recirculating system. There was an inverse linear relationship between stocking density and growth among both species. The relationship between final weight and stocking density is described by the following linear equation: P. setiferus , Y =−0.00619X ± 4.46, adj. r2= 0.8572;. P. vannamei, Y =−0.00717X ± 7.39, adj. r2= 0.6230. Although the responses in terms of growth depressions were similar, P. setiferus growth was lower than that of P. vannamei . There was an inverse relationship between stocking density and survival for P. setiferus . Survival of P. vannamei was highly variable but was negatively correlated with density. Based on the results of the present study, P. setiferus has a similar tolerance of high density as that of P. vannamei and hence may be suitable for intensive culture systems. However, depressed growth rates of P. setiferus , which do not appear to be due to effects of water quality or density, must be solved if growth rates similar to P. vannamei are to be realized.  相似文献   

16.
Abstract. Effects of stocking density on water quality and on the growth, survival and food conversion of Oreochromis niloticus (Linnaeus) were evaluated. Fingerlings of tilapia (average weight 40.25 ± 94 g) were stocked in six 3.75-m3 concrete tanks at 16, 32 and 42.6/m3 and reared for 164 days. A water flow rate of 1 l/min/kg fish biomass was maintained in all the tanks. The growth rate was inversely related to stocking density with mean weights of 337.25g, 327.0g and 323.5g at the low, medium and high densities respectively. At harvest, standing crop biomass averaged 5.36 kg, 10.44kg and 13.24kg for the three densities. The respective food conversion ratios (FCR) were 1.85, 1.88 and 1.95, while the survival rates were 99.2, 99.6 and 95.9%. However, the survival rate, growth rate and food conversion efficiencies were not significantly different at the three stocking densities. Water quality did not deteriorate in different tanks as the oxygen was continuously replenished and metabolites and waste products removed by the water flowing through the tanks. These data suggest that culture of tilapia at a density of 42.6/m3 and production of 13.24 kg/m3 in 164 days with a production of 18–20 kg/m3 in a growing season (April-October) of 210 days is possible using the drainage water in flow-through water systems.  相似文献   

17.
A specially designed recirculating system was used to maintain P. vannamei broodstock for maturation, mating and spawning in the same tank. Two groups of different size shrimp were stocked in this system in Phase I (8 May to 5 September 1989) and Phase II (5 September to 5 December 1989). Results showed that this recirculating system was able to maintain good water quality keeping broodstock maturing, mating and spawning with high stocking density (10 shrimp/m2) and low mortality (6%). Seventy-eight percent of spawned eggs were collected by a submerged egg collector. Mating success was very poor (3.4%) in Phase I even though there was normal spawning frequency. Mating success and nauplii production were much improved in Phase II. During Phase II 104 male and female broodstock housed in a 6 m3 tank produced 1.6 ± 106 nauplii (with 70% mating success) in three months. This study illustrated that broodstock size was a critical factor of successful mating and fertilization for P. vunnamei , and also, reduction of handling stress and lowered disturbance of the shrimp greatly enhanced the mating success.  相似文献   

18.
Abstract This study was conducted to evaluate the effects of stocking density and monosex culture on growth, survival, yield and feed conversion ratio of freshwater prawn Macrobrachium rosenbergii in concrete tanks. Juvenile prawns with an average weight of 1.8 g were stocked into triplicate tanks at densities of 5, 10, 15 and 20 prawns/m2, grown for 168 d and fed a 34% tilapia diet. Stocking density had significant effect on prawns. Final mean body weight decreased with the increasing density, being highest at 5 prawns/m2 (29.6 9). and lowest at 20 prawns/m2 (17.4 g). Total yield increased from 135 g/m2 (1,350 kg/ha) at a density of 5 prawns/m2 to 261 g/m2 (2,610 kg/ha) at density 15/mz to 245 g/m2 (2,450 kg/ha) at 20/mz. Feed conversion ratios were high and ranged from 3.7 (5 prawns/m2) to 5.6 (20 prawns/m2).
In monosex culture of freshwater prawns stocked in triplicate tanks at a density of 5 prawns/m2 for 112 d, the all-male population had the best growth performance and feed conversion ratio, followed by the mixed-sex and all-female populations. The all-male population had 99% marketable prawns (>20 g) with an average yield of 159 g/m2 (1,590 kg/ha); the mixed-sex population had 90% marketable prawns and the yield was 135 g/mz (1,350 kg/ha); and the all-female population had 75% marketable prawns with an average yield of 108 g/m2 (1,080 kgha).  相似文献   

19.
Super Intensive Culture of Red-Tailed Shrimp Penaeus penicillatus   总被引:1,自引:0,他引:1  
Two continuous grow-out experiments of red-tailed shrimp Penueus penicillatus were conducted for one year in a super intensive system with a stocking density of 171 and 286 postlarvae/m2, respectively. The postlarval shrimp (Ph8–12) were cultured in three 0.14 ha earthen ponds with concrete dikes. The shrimp were fed with a commercially prepared feed four times a day. Water quality parameters from the second trial varied as follows: water temperature from 23.0 to 30.4 C, salinity from 15.33 to 21.00 ppt, dissolved oxygen (DO) from 3.47 to 7.34 mg/L, NH3-N from 0.002 to 0.869 mg/L, nitrite-N from 0.013 to 0.844 mg/L, and nitrate-N from 0.021 to 1.795 mg/L. Ammonia-N increased from 0.022 to 46.110 mg/L, while the pH declined from 8.12 to 7.32. Yield was 4,650 kg/0.42 ha from the first crop in 131 days and 5,160 kg/0.42 ha from the second crop in 141 days. The productivity of this system producing P. penicillatus was 11–12 tons/ha/crop.  相似文献   

20.
A generalized nitrogen budget was constructed to evaluate the potential role of mangrove sediments as a sink for dissolved inorganic nitrogen (DIN) in shrimp pond effluents. DIN concentrations were measured in pond effluents from three semi-intensive shrimp ponds along the Caribbean coast of Colombia between 1994–1995. Mean NH4+ concentrations in the discharge water for all farms were significantly higher (67 × 12 μg/L) than in the adjacent estuaries (33 × 8 μg/L). Average NH4+ concentrations in the pond discharge over all growout cycles were similar, representing an approximate doubling in relation to estuarine water concentrations. In contrast, NO2-+ NO3- concentrations were similar in both pond effluent and estuarine waters. Dissolved inorganic nitrogen loading of the ponds was similar. The estimated reduction of DIN in pond effluents by preliminary diversion of outflow to mangrove wetlands rather than directly to estuarine waters would be × 190 mg N/m2 per d. Based on this nitrogen loss and depending upon the enrichment rate, between 0.04 to 0.12 ha of mangrove forest is required to completely remove the DIN load from effluents produced by a 1-ha pond.  相似文献   

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