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1.
Penaeid shrimp reared in eutrophic pond water grow significantly faster than shrimp in clear well water, and this growth enhancement is especially pronounced in postlarval shrimp. The objective of this study was to determine if the nutritional benefits of pond water could supplement a lower protein feed for postlarval Pacific white shrimp Litopenaeus vannamei . Sixteen 230-L tanks were stocked with 10-d postlarvae at a density of 350 shrimp/tank. Four treatments (four replicates/treatment) were tested for 6 wk and consisted of: 1) shrimp grown in well water and fed a commercially available 45%-protein feed (W/45); 2) shrimp grown in pond water and fed the same 45%-protein feed (P/45); 3) shrimp grown in well water and fed a commercially available 52%-protein feed (W/ 52); and 4) shrimp grown in pond water and fed the same 52%-protein feed (P/52). At the end of the experiment. mean weight gain (± SE) for shrimp in pond water (1.85 ± 0.03 g) was significantly greater ( P > 0.0001) than shrimp in well water (0.98 ± 0.10 g). Mean weight gain for shrimp fed the 52%-protein feed (1.56 ± 0.13 g) was significantly greater ( P > 0.0001) than shrimp fed the 45%-protein feed (1.26 ± 0.20 g). In addition, there was a significant interaction effect between water source and feed ( P > 0.0001). Mean weight gain for shrimp in the W/52 treatment (1.23 ± 0.04 g) was 68% greater than shrimp in the W/45 treatment (0.73 ± 0.03 g). However, mean weight gain for shrimp in the P/52 treatment (1.90 ± 0.03 g) was only 5% greater than shrimp in the P/45 treatment (1.80 ± 0.04 g). These results suggest that organically rich pond water provides postlarval shrimp with sufficient nutrients to compensate for nutritional deficiencies associated with a lower protein feed.  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.
Rapid in vitro methods for measuring digestibility may be useful in analysing aqua feeds if the extent and limits of their application are clearly defined. The pH‐stat protein digestibility routine with shrimp hepatopancreas enzymes was previously related to apparent protein digestibility with juvenile Litopenaeus vannamei fed diets containing different protein ingredients. The potential of the method to predict culture performance of shrimp fed six commercial feeds (T3, T4, T5, T6, T7 and T8) with 350 g kg?1 declared crude‐protein content was assessed. The consistency of results obtained using hepatopancreas enzyme extracts from either pond or clear water‐raised shrimp was further verified in terms of reproducibility and possible diet history effects upon in vitro outputs. Shrimps were previously acclimated and then maintained over 56 days (initial mean weight 3.28 g) on each diet in 500‐L tanks at 114 ind m?2, clear water closed system with continuous renewal and mechanical filtering (50 μm), with four replicates per treatment. Feeds were offered four times daily (six days a week) delivered in trays at feeding rates ranging from 4.0% to 7.0% of stocked shrimp biomass. Feed was accessible to shrimp 4 h daily for 1‐h feeding period after which uneaten feed was recovered. Growth and survival were determined every 14 days from a sample of 16 individuals per tank. Water quality was monitored daily (pH, temperature and salinity) and managed by water back flushing filter cleaning every 7–10 days. Feeds were analysed for crude protein, gross energy, amino acids and pepsin digestibility. In vitro pH‐stat degree of protein hydrolysis (DH%) was determined for each feed using hepatopancreas enzyme extracts from experimental (clear water) or pond‐raised shrimp. Feeds resulted in significant differences in shrimp performance (P < 0.05) as seen by the differences in growth rates (0.56–0.98 g week?1), final weight and feed conversion ratio (FCR). Shrimp performance and in vitro DH% with pond‐raised shrimp enzymes showed significant correlation (P < 0.05) for yield (R2 = 0.72), growth rates (R2 = 0.72–0.80) and FCR (R2 = ?0.67). Other feed attributes (protein : energy ratio, amino acids, true protein, non‐protein nitrogen contents and in vitro pepsin digestibility) showed none or limited correlation with shrimp culture performance. Additional correlations were found between growth rates and methionine (R2 = 0.73), FCR and histidine (R2 = ?0.60), and DH% and methionine or methionine+cystine feed contents (R2 = 0.67–0.92). pH‐stat assays with shrimp enzymes generated reproducible DH% results with either pond (CV ≤ 6.5%) or clear water (CV ≤ 8.5%) hepatopancreas enzyme sources. Moreover, correlations between shrimp growth rates and feed DH% were significant regardless of the enzyme origin (pond or clear water‐raised shrimp) and showed consistent R2 values. Results suggest the feasibility of using standardized hepatopancreas enzyme extracts for in vitro protein digestibility.  相似文献   

4.
Outdoor microcosm tanks were used to grow the penaeid blue shrimp, Litopenaeus stylirostris, in Brunei Darussalam. The tanks were cylindrical, free standing fiber glass tanks of 1827 L water holding capacity and had a self-cleaning mechanism. In three eight-week feeding trials, juvenile shrimp of 0.9–4.3 g were stocked at a density of 28 shrimp/m2. At the end of each trial, survival rates exceeded 80%. Growth rates ranged from 1.19 to 2.46 g/week. Water quality remained stable and within suitable ranges for L. stylirostris growth in all trials. The tanks had algae and bacterial floc developing within a few days of starting the trials. Fourteen commercial shrimp feeds, each containing more than 40% crude protein, were tested in the trials. In spite of the presence of natural food organisms, significant feed-related differences among treatments were found in each trial. In conclusion, microcosm tanks support excellent growth and survival of L. stylirostris and are appropriate for conducting trials to evaluate feeds for pond growout.  相似文献   

5.
Abstract— The production of Litopenaeus vannamei in inland low‐salinity well water is a growing industry in several regions of the world. The state of Alabama in the southeastern USA is one such region with a large saline aquifer that could be utilized for shrimp culture. However, some farmers are experiencing problems rearing marine shrimp while others are having considerable success. Previous work has correlated low levels of potassium andor magnesium to poor shrimp survival. The problem is further complicated by the fact that the age at acclimation may also influence survival. In our present study, we evaluated the effects of potassium, magnesium, and the age of acclimation on growth and survival of PL at two farms. The first experiment was run in a static system utilizing four replicate tanks per treatment. Fifty PL17 (0.0066 g) that had been acclimated to 4 ppt seawater were stocked into each tank and the following treatments evaluated: low salinity well water (LSWW) without mineral supplements, LSWW with KCl, LSWW with MgCl2, and LSWW with KCl and MgCl, added to the water. Shrimp were harvested, counted and weighed after 4 wk. Survival was significantly higher in treatments receiving mineral supplements whereas biomass was only higher in the two treatments with potassium supplements. The second experiment was set up initially as a static system filled with 8.5‐ppt reconstituted sea water that was then converted to a flow‐through system using LSWW. This experiment evaluated the effect of PL age at acclimation on survival and growth at four different ages (PL15, PL19, PL23, and PL27). All tanks were stocked with 50 PL13L. vannarnei. Two days after stocking, and then at 4‐d intervals, a series of four tanks were converted to flow through (rate of 40 Lhr) using LSWW. After acclimation, water flow was maintained in all tanks until 28 d after stocking when tanks were harvested and surviving shrimp were counted and weighed. Survival and growth increased with PL age when shrimp were acclimated to inland low salinity well water.  相似文献   

6.
Development of an intensive culture system is presently being conducted in Kuwait as a means of farming penaeid shrimp in arid lands. Efficiency of commercial-scale hatchery production of Penaeus semisulcatus and P. japonicus showed significant improvement in 1981 over previous years. Three one-month hatchery rearing cycles in three 15 m3 concrete tanks yielded a total of 9.1 million post-larval shrimp with an average density of 160 PL/liter being obtained for one of these trials. Four other trials were discontinued due to low spawning rates and disease. Installation of a heat exchange system made it possible to begin larviculture in February, two months earlier than in previous years. Research in nursery and grow-out phases of intensive shrimp culture is being directed towards raceways, although Shigueno culture systems are also being investigated. Experimental work with six 18 m × 1.5 m raceways demonstrated that low water exchange rates (1 tank volume/day), combined with high aeration (9.5 liter/min) yielded the highest shrimp biomass. Unheated greenhouse structures constructed over the raceways showed that a single layer of 0.25 mm clear plastic sheeting could maintain water temperatures up to 2.7°C above those in unenclosed tanks. Rearing trials in two Shigueno tank systems demonstrated the importance of high water flow rates (3 tank volumes/day minimum) and adequate aeration. Due to sub-optimal conditions, survival was reduced to 7.5%, however, growth rates up to 6 g/month were obtained for P. semisulcatus.  相似文献   

7.
研究了由表面流与水平潜流组成的复合人工湿地联合使用塘内曝气增氧机与人工净化网调控生产性淡水对虾养殖塘水环境的效果与技术。养殖中后期(约60 d后), 湿地以1.65 m/d水力负荷, 3次循环处理虾塘废水, 有效调控虾塘水质, 确保养殖成功。结果表明湿地对废水中有害物质均可程度不等地去除, 蓝绿藻得以控制, 出口水 -N与BOD5分别为极显著(P<0.01)与显著(P<0.05)去除, 去除率与去除速率分别为72.6%, 0.467 g/(m2·d)与29.7%, 2.651 g/(m2·d), -P为41.7%, 0.022 g/(m2·d), TN为26.1%, 2.619 g / (m2?d), CODMn为15.9%, 3.738 g/(m2·d), -N去除率仅3.6%, 但去除速率较高[0.462 g/(m2·d)]。湿地静止4 d期间, 废水中 -N与 -N去除率达96.8%与93.3%, 均极显著去除(P<0.01)。养殖周期试验塘水化学指标均维持在虾安全生长范围内, 收获虾8.81 g, 9.36 cm; 对照塘因爆发蓝绿藻仅养殖60 d, 收获虾3.06 g, 6.54 cm。试验表明, 在不用药、不换水条件下, 联合塘内设施, 人工湿地以较高水力负荷与低频率运转可有效调控虾塘水质, 确保养殖成功。  相似文献   

8.
Pontoons made from plastic pipe were tested as an alternative to racks for deepwater culture of the Sydney rock oyster. The growth and mortality of oysters permanently suspended in water on trays beneath floating pontoons were compared with oysters on trays in an intertidal zone. For both culled spat (30–31 g whole oyster weight) and seconds oysters (37–39 g) beneath pontoons the growth rate, measured by weight increases, was three times that of oysters on intertidal racks over a 5-month period. Mortality (from unknown causes) was higher beneath the pontoons. The mean mortality of spat oysters was 40% compared with 24% on the intertidal trays, and for seconds oysters was 51% compared with 34%.  相似文献   

9.
After preliminary six week experiments showed that shrimp pond effluent from an intensive culture growout pond had the capacity to nearly double shrimp growth in laboratory tanks, an 18 day experiment was designed to determine if similar results occurred in the presence of high quality feeds. The results presented here corroborate the hypothesis that autochthonous factors in shrimp pond water stimulate shrimp growth. These results revealed that performance of currently available shrimp feeds is greatly improved in the presence of pond effluent, regardless of feed quality. Increased feed performance did not appear to be an artifact of supplemental feed availability in pond effluent. The implications from these experiments are that, even in intensive culture systems (above 40 shrimp per m2), in-situ sources of nutrition play an important role in shrimp growth.  相似文献   

10.
Redox potential represents the intensity of anaerobic condition in the pond sediment, which may affect the dominant microbial transformations of substances, the toxins production, mineral solubility, as well as the water quality in the sediment–water interface inhabited by the shrimp. This study evaluates the effect of sediment redox potential in conjunction with stocking density on shrimp production performance, immune response and resistance against white spot syndrome virus (WSSV) infection. A completely randomized two factors experimental design was applied with three different sediment redox potential, i.e. ?65, ?108 and ?06 mV, and two shrimp densities, i.e. low (60 shrimp m?2) and high (120 shrimp m?2). Shrimp juveniles with an initial mean body weight of 5.32 ± 0.22 g were maintained in semi‐outdoor fibre tanks (270 L in capacity) for 35 days of experimental periods. At the bottom of each tank, 5‐cm deep soil substrate with different redox potential was added according to the treatments. The survival and biomass production were significantly reduced at ?206 mV sediment redox potential, regardless of stocking density. Highly negative sediment redox potential (?206 mV) and higher stocking density significantly reduced total haemocyte counts and phenoloxydase activity, and shrimp resistance to WSSV infection. We recommend to maintain the redox potential of pond sediment at a level of more than ?206 mV.  相似文献   

11.
Current shrimp pond management practices generally result in elevated concentrations of nutrients, suspended solids, bacteria and phytoplankton compared with the influent water. Concerns about adverse environmental impacts caused by discharging pond effluent directly into adjacent waterways have prompted the search for cost‐effective methods of effluent treatment. One potential method of effluent treatment is the use of ponds or raceways stocked with plants or animals that act as natural biofilters by removing waste nutrients. In addition to improving effluent water quality prior to discharge, the use of natural biofilters provides a method for capturing otherwise wasted nutrients. This study examined the potential of the native oyster, Saccostrea commercialis (Iredale and Roughley) and macroalgae, Gracilaria edulis (Gmelin) Silva to improve effluent water quality from a commercial Penaeus japonicus (Bate) shrimp farm. A system of raceways was constructed to permit recirculation of the effluent through the oysters to maximize the filtration of bacteria, phytoplankton and total suspended solids. A series of experiments was conducted to test the ability of oysters and macroalgae to improve effluent water quality in a flow‐through system compared with a recirculating system. In the flow‐through system, oysters reduced the concentration of bacteria to 35% of the initial concentration, chlorophyll a to 39%, total particulates (2.28–35.2 µm) to 29%, total nitrogen to 66% and total phosphorus to 56%. Under the recirculating flow regime, the ability of the oysters to improve water quality was significantly enhanced. After four circuits, total bacterial numbers were reduced to 12%, chlorophyll a to 4%, and total suspended solids to 16%. Efforts to increase biofiltration by adding additional layers of oyster trays and macroalgae‐filled mesh bags resulted in fouling of the lower layers causing the death of oysters and senescence of macroalgae. Supplementary laboratory experiments were designed to examine the effects of high effluent concentrations of suspended particulates on the growth and condition of oysters and macroalgae. The results demonstrated that high concentrations of particulates inhibited growth and reduced the condition of oysters and macroalgae. Allowing the effluent to settle before biofiltration improved growth and reduced signs of stress in the oysters and macroalgae. A settling time of 6 h reduced particulates to a level that prevented fouling of the oysters and macroalgae.  相似文献   

12.
The influence of tank wall color and up‐welling water flow on growth and survival of Eurasian perch larvae (Perca fluviatilis) was tested in an intensive culture system. Newly hatched larvae were fed Artemia nauplii, later combined with dry feed, and reared for 5 wk in either black tanks with up‐welling water flow or in gray tanks with or without up‐welling water flow. The perch larvae grew significantly faster in black tanks than in gray tanks regardless of water flow. Two weeks after hatching, a significantly higher mean weight was shown in larvae reared in black tanks compared to larvae reared in gray tanks with up‐welling water flow, and after 4 wk, the mean weight was significantly higher than in both of the other treatments. The difference in growth was further enhanced during the last week of the experiment, and the final mean weights were 51.1 ± 1.9 mg in black tanks with up‐welling water flow, 23.8 ± 2.1 mg in gray tanks with up‐welling water flow, and 23.7 ± 2.2 mg in gray tanks without up‐welling water flow. The cumulative mortality at the end of the experiment averaged 75% in all treatment groups. Taken together, the enhanced growth of Eurasian perch larvae in black tanks could be explained by high prey contrast and increased prey consumption. Up‐welling water flow had no impact on growth and survival of the perch larvae in gray tanks, indicating that the availability and consumption of the prey were independent of water movement.  相似文献   

13.
Records of shrimp growth and water quality made during 12 crops from each of 48 ponds, over a period of 6.5 years, were provided by a Queensland, Australia, commercial shrimp farm. These data were analysed with a new growth model derived from the Gompertz model. The results indicate that water temperature, mortality and pond age significantly affect growth rates. After 180 days, shrimp reach 34 g at constant 30 °C, but only 15 g after the same amount of time at 20 °C. Mortality, through thinning the density of shrimp in the ponds, increased the growth rate, but the effect is small. With continual production, growth rates at first remained steady, then appeared to decrease for the sixth and seventh crop, after which they have increased steadily with each crop. It appears that conservative pond management, together with a gradual improvement in husbandry techniques, particularly feed management, brought about this change. This has encouraging implications for the long-term sustainability of the farming methods used. The growth model can be used to predict productivity, and hence, profitability, of new aquaculture locations or new production strategies.  相似文献   

14.
A comparative study was carried out to compare the effect of caging mullet and tilapia in a shrimp polyculture system. In six shrimp tanks (three tanks for each fish species), either mullet, Mugil cephalus (CCT‐SM), or tilapia, Oreochromis niloticus (CCT‐ST), was stocked in cages. In three other tanks, mullets were allowed to roam freely in shrimp tanks (D‐SM). White shrimp, Litopenaeus vannamei (0.50 g), was cultured as the predominant species were distributed randomly into nine fibreglass tanks (5 m3) at a density of 300 shrimp/tank, while fish (1.50 g) were stocked at the same density of 10% of the initial total shrimp biomass. The results showed that water quality parameters were not significantly different among treatments (p > .05), except for total suspended solids (TSSs). System performances based on parameters such as total weight gain (2,808.15 g/tank) and nutrient recovery were higher in D‐SM treatment (39.80% for nitrogen and 27.40% for phosphorus) than in CCT‐SM and CCT‐ST treatments (p < .05). These system performance parameters were significantly affected by the mullet‐holding strategy; however, they were not affected by fish species. The addition of mullet or tilapia in shrimp tanks did not affect shrimp growth differentially. Fish growth performances based on parameters such as final weight (98.43 g/fish) and DGR (1.29 g/day) were significantly higher in D‐SM treatment and were significantly different among D‐SM, CCT‐SM and CCT‐ST treatments (p < .05). It is concluded that in shrimp–fish polyculture with a stocking density of fish at 10% of the initial total shrimp biomass, tilapia is more effective than mullet, when caged. However, under free‐roaming conditions, the use of mullet is more effective in terms of system performances relative to a system holding caged tilapia.  相似文献   

15.
Shrimp pond effluent water can contain higher concentrations of dissolved nutrients and suspended particulates than the influent water. Consequently, there are concerns about adverse environmental impacts on coastal waters caused by eutrophication and increased turbidity. One potential method of improving effluent water quality prior to discharge or recirculation is to use bivalves to filter the effluent. In this study, we examined the effects of the Sydney rock oyster, Saccostrea commercialis (Iredale & Roughley), on the water quality of shrimp pond effluent. Effluent from a shrimp farm stocked with Penaeus japonicus (Bate) was pumped directly into 34-L tanks stocked with different densities of oysters. Combinations of live and dead oysters were used to test the effects of three different densities of live oysters (24, 16 and 8 live oysters per tank). The concentrations of total suspended solids, the proportion of organic and inorganic matter, total nitrogen, total phosphorous, chlorophyll a and the total number of bacteria in the pond effluent water were determined before and after filtration by oysters. The oysters significantly reduced the concentration of all the parameters examined, with the highest oyster density having the greatest effect. Shrimp pond effluent contained a higher proportion of inorganic matter (72%) than organic matter (28%). The organic component appeared to be mainly detritus, with chlorophyll a comprising only a minor proportion. Filtration by the high density of oysters reduced the effluent total suspended solids to 49% of the initial level, the bacterial numbers to 58%, total nitrogen to 80% and total phosphorous to 67%. The combined effects of settlement and oyster filtration reduced the concentration of chlorophyll a to 8% of the initial effluent value.  相似文献   

16.
The objective of this study was to demonstrate the feasibility of four diets formulated to contain increasing levels (0, 50, 100 and 150 g kg?1 of diet) of grain distillers dried yeast (GDDY) in production diets for Litopenaeus vannamei, reared in outdoor tanks or production ponds. The production pond trial was carried out in 16, 0.1‐ha ponds using four replicates per diet. Juvenile shrimp (38.1 ± 4.26 mg, initial weight) were stocked at 30 shrimp m?2 for a 16‐week period. The same four diets and a commercial reference diet were offered to shrimp maintained in outdoor tanks over a 12‐week period. A total of 20 tanks were stocked with juvenile shrimp (3.05 ± 0.22 g, initial weight) obtained from production ponds at a density of 30 shrimp per tank (40 shrimp m?2). At the conclusion of these trials, mean final weight ranged from 19.77 to 23.05 g, yield ranged between 4760 and 5606 kg ha?1, survival ranged from 69.6% to 89.4%, and feed conversion ratio (FCR) was between 1.02 and 1.23. Shrimp reared in the outdoor tanks confirmed the results of the pond trial. Mean final weight ranged between 18.12 and 18.97 g, survival ranged from 93.3% to 98.3%, and FCR was between 1.25 and 1.29. In both trials, there were no significant differences regarding mean final weight, FCR and survival among dietary treatments. Based on this study, GDDY up to 150 g kg?1 of diet can be used in L. vannamei commercial feed formulation.  相似文献   

17.
The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial shrimp (penaeid prawn) pond in subtropical Australia. Physicochemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 μm mesh) varied from 111.7 ind. L?1 (324 μg L?1) to 8.3 ind. L?1 (44.2 μg L?1). Immediately after the ponds were stocked with shrimp postlarvae there was a rapid decline in zooplankton numbers, particularly the dominant larger copepods. We attributed this to predation by the shrimp postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. Changes in abundance and biomass of the zooplankton assemblage were not correlated with physicochemical characteristics. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m?2 and the biomass at 0.8 g m?2. Unlike zooplankton, the peaks in abundance of epibenthos did not correspond to the peaks in biomass. This was due to the large differences in the size of the dominant taxa across the season. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples, with amphipods abundance increasing towards the end of the growout. Negative correlations were found between epibenthos abundance and pH and temperature. These relationships were strongly influenced by the high abundances of amphipods and may reflect an effect on the growth of macroalgae in the pond rather than a direct effect on the epibenthos. No correlations were found between epibenthic fauna biomass and physicochemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities, indicating that this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes in abundances of zooplankton or epibenthos assemblages. Zooplankton clearly contribute to the nutrition of shrimp postlarvae immediately after stocking. The establishment of an abundant assemblage of zooplankton before stocking shrimp postlarvae would appear to be beneficial, if not essential. Later in the season, zooplankton and epibenthos apparently contribute little to shrimp biomass. Owing to their relatively low biomass, the consumption of shrimp feeds by epibenthos is likely to be insignificant compared with that of the shrimp.  相似文献   

18.
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   

19.
Gut bacteria may contribute significantly to the growth and survival of cultured shrimp, although little is known about factors that affect bacterial community structure in shrimp guts. The objective of this study was to determine the abundance and species composition of gut bacteria in juvenile white shrimp Litopenaeus vannamei reared in two different environments. Eight 120-L tanks were stocked at a density of 8 shrimphank. Two treatments were tested for 10 d and consisted of tanks receiving flow-through water from one of two sources: 1) well water pumped from a sea-water aquifer (Well treatment), and 2) pond water pumped from an intensive shrimp pond (Pond treatment). Shrimp mid- and hindguts were excised on days 1, 3, 6, and 10 for enumeration of gram-negative, aerobic bacteria by quantifying colony-forming units (CFU) using standard microbiological plating techniques. Identification of bacterial isolates was made using the Biologa® GN Microplate system. Bacterial numbers were significantly greater ( P > 0.05) in Well shrimp than in Pond shrimp on days 1 and 3. Following day 3, a decrease in bacterial numbers occurred in the Well shrimp, and no significant differences between treatments were observed on days 6 or 10. Guts from Well shrimp were dominated by Vibrio and Aero-monas , and these two genera accounted for 80–851 of the bacteria on each sampling day. Guts from Pond shrimp exhibited a greater bacterial diversity and were dominated by Vibrio, Aeromonas , and Pseudomonas. Flavobacterium were identified in the guts of Pond shrimp on days 3 and 10, but were not identified in any of the Well shrimp. A greater understanding of gut bacteria-shrimp interactions could lead to increased production and profitability for shrimp farmers through the development of more cost-effective feeds and novel disease control strategies.  相似文献   

20.
The use of artificial substrates in shrimp aquaculture may allow for production of shrimp at increased densities while providing a growth medium for microbes that assist with water quality processes and provide supplemental nutrition for shrimp. Greenhouse-based shrimp production systems can extend the shrimp production season in temperate climates while conserving water and energy. For this study, we evaluated the effects of providing extra substrate and shrimp density on water quality and shrimp production in greenhouse-based biofloc systems. Four 11-m3, wood framed, and rubber-lined tanks were constructed in each of four high tunnel greenhouses (for a total of 16 tanks). Four treatments were evaluated: high-density stocking with substrate (HDS), high-density stocking with no substrate (HDNS), low-density stocking with substrate (LDS), and low-density stocking with no substrate (LDNS). Each treatment was randomly assigned to one tank in each tunnel to block for location. No artificial heat was used, and shrimp were grown for 120 days. High-density systems were stocked at 200 shrimp/m³ while low-density tanks had 100 shrimp/m³. Adding substrate increased total in-tank surface area by 13.4%. The addition of substrate had no significant effect on any shrimp production or standard water quality parameters. Shrimp had significantly greater final weight, faster growth rate, and lower feed conversion rate in low-density treatments (P ≤ 0.02 for all). Total shrimp biomass production was significantly higher in high-density treatments (HD: 4.0 kg/m3; LD: 2.3 kg/m3; P < 0.05). There were no significant differences in survival between densities (HD: 91.3%; LD: 94.5%; P = 0.43). Peak and overall mean nitrite levels were significantly higher in high-density treatments compared to low-density treatments. Dissolved oxygen levels and pH over the course of the study were significantly lower in high-density treatments, likely due to increased respiration rates in the water column. This project shows the feasibility of shrimp production in temperate climates with no artificial heat using high tunnel greenhouses, few impacts of added substrate on shrimp production, and increased shrimp density can result in much larger harvests with few negative impacts on production metrics.  相似文献   

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