首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The effects of open‐water and caged fish density on growth, feed utilization, water quality and profitability were investigated to assess the feasibility of a small‐scale rotational system for production of Oreochromis niloticus (L.) in fertilized ponds. Hand‐sexed male fingerlings averaging 18.6 and 29.9 g were stocked in open water and cages, respectively in four treatments with open‐pond:caged tilapia ratios of 300:0 (control), 150:150 (L), 300:150 (H1) and 300:300 (H2). The ponds in L and H1 contained one cage, two cages in H2, and the control ponds had no cages. Each cage contained 150 fish, which were fed daily at 1.5% body weight for 125 days. All fish in the open water except the control fish were not fed. Growth of open water tilapia was significantly (P<0.05) higher in L than in control. Feed utilization, dawn DO and economic returns were significantly better (P<0.05) in caged than control ponds. Growth of tilapia in L was significantly lower (P<0.05) in cages than in open water. Fingerling production was significantly lower (P<0.05) in L than in other treatments. In conclusion, cage‐cum‐open‐pond integrated treatment (L) was optimal for O. niloticus production in fertilized ponds. However, the system could not rotate and needed further fine‐tuning to rotate.  相似文献   

2.
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   

3.
The effects of different densities of caged Nile tilapia, Oreochromis niloticus, on water quality, phytoplankton populations, prawn, and total pond production were evaluated in freshwater prawn, Macrobrachium rosenbergii, production ponds. The experiment consisted of three treatments with three 0.04‐ha replicates each. All ponds were stocked with graded, nursed juvenile prawn (0.9 ± 0.6 g) at 69,000/ha. Control (CTL) ponds contained only prawns. Low‐density polyculture (LDP) ponds also contained two cages (1 m3; 100 fish/cage) of monosex male tilapia (115.6 ± 22 g), and high‐density polyculture (HDP) ponds had four cages. Total culture period was 106 d for tilapia and 114 d for prawn. Overall mean afternoon pH level was significantly lower (P ≤ 0.05) in polyculture ponds than in CTL ponds but did not differ (P > 0.05) between LDP and HDP. Phytoplankton biovolume was reduced in polyculture treatments. Tilapia in the LDP treatment had significantly higher (P ≤ 0.05) harvest weights than in the HDP treatment. Prawn weights were higher (P ≤ 0.05) in polyculture than prawn monoculture. These data indicate that a caged tilapia/freshwater prawn polyculture system may provide pH control while maximizing pond resources in temperate areas.  相似文献   

4.
Abstract.— A 12‐wk feeding trial was conducted in cages with juvenile Nile tilapia Oreochromis niloticus to evaluate distillers grains with solubles (DDGS) as a direct feed, the effects of pelleting on its utilization, and the compatibility of caged tilapia and prawns in polyculture. Nine 1.0‐m3 cages were stocked with 200 juvenile (26 ± 0.9 g) tilapia. Cages were suspended in a 0.2‐ha pond stocked with juvenile freshwater prawns Macrobrachium rosenbergii at 40,000/ha. Three replicate cages were randomly assigned to each dietary treatment. In one dietary treatment DDGS was fed as an unpelleted loose grain ration (26% protein). In a second dietary treatment fish were fed DDGS that had been steam‐pelleted (23% protein). Fish in a third dietary treatment were fed a commercial catfish diet (31% protein) for comparison. After 12 wk, individual weight, individual length, and specific growth rate were significantly higher (P < 0.05) and feed conversion ratio was significantly lower (P < 0.05) for fish fed the commercial catfish diet than for fish fed either unpelleted or pelleted DDGS. Specific growth rate was significantly higher (P < 0.05) for fish fed pelleted DDGS than for fish fed unpelleted DDGS. Survival did not differ significantly (P > 0.05) among treatments (>95%). Although growth was increased in fish fed the commercial diet, their cost of production (<0.66/kg gain) was significantly higher (P < 0.05) than in fish fed unpelleted and pelleted DDGS (<0.26/ kg gain and <0.37/kg gain, respectively). The costs of gain in fish fed unpelleted DDGS was significantly lower (P < 0.05) than in fish fed the pelleted DDGS. Prawn production was 1,449 kg/ha and addition of tilapia in polyculture increased total pond productivity approximately 81 %. These data suggest that DDGS provides economical growth in tilapia when fed as a direct feed and that polyculture of tilapia may improve overall pond efficiency in freshwater prawn production ponds, even at temperate latitudes.  相似文献   

5.
Channel catfish (lctalurus punctatus) fingerlings stocked at a rate of 450 fish/0.04 ha pond were simultaneously cultured with fingerlings stocked in 1.25 m3 cages (0, 250, 350, or 450 fishlcage; one cage/pond). The fish in the cages were cultured and harvested for a 90–330 g (whole fish) market. The fish in the open ponds were cultured and harvested for a 490–1,140 g market. Harvest weights of open pond fish in all treatments were similar indicating that the presence of the caged fish and the associated higher daily pond feeding rates did not affect open pond production. Ninety-five to 99% of the caged fish and 96 to 98% of the open pond fish were of marketable size at harvest. Survival and food conversion ratios were similar among treatments. Results of this study indicate that total pond production can be increased (in this case up to 19%) by using a combination of open pond and cage techniques and by simultaneously producing fish for two markets.  相似文献   

6.
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   

7.
Five pond management strategies for Nile tilapia Oreochromis niloticus L. production were evaluated in 0.1‐ha earthen ponds in Egypt during a 145‐day production cycle. Pond management strategies developed by the Pond Dynamics/Aquaculture Collaborative Research Support Programme (PD/A CRSP) were compared with a traditional and a modified Egyptian pond management strategy. Young‐of‐year Nile (mixed‐sex or sex‐reversed) tilapia were stocked into ponds at 20 000 fish ha?1. Sex‐reversed tilapia were stocked into chemical fertilization, organic fertilization plus formulated feed and feed only treatment ponds, whereas mixed‐sex tilapia were stocked into organic fertilization plus formulated feed and chemical plus organic fertilization plus formulated feed treatment ponds. Nile tilapia yields ranged from 1274 to 2929 kg ha?1. Nile tilapia yields in organic fertilization plus formulated feed treatments were significantly greater than the yield from chemical fertilization ponds. PD/A CRSP pond management strategies did not produce significantly greater Nile tilapia yields than the traditional Egyptian system, but a larger percentage of harvested tilapia in the organic fertilization plus feed treatments were classified in the first and second class size categories compared with the traditional Egyptian system. Organic fertilization plus formulated feed pond management strategies had the highest net returns, average rate of return on capital and the highest margin between average price and break‐even prices to cover total variable costs or total costs.  相似文献   

8.
Growth and survival of hatchery‐bred Asian catfish, Clarias macrocephalus (Günther), fry reared at different stocking densities in net cages suspended in tanks and ponds were measured. The stocking densities used were 285, 571 and 1143 fry m?3 in tanks and 114, 228 and 457 fry m?3 in ponds. Fish were fed a formulated diet throughout the 28‐day rearing period. Generally, fish reared in cages in ponds grew faster, with a specific growth rate (SGR) range of 10.3–14.6% day?1, than those in cages suspended in tanks (SGR range 9–11.3% day?1). This could be attributed to the presence of natural zooplankton (copepods and cladocerans) in the pond throughout the culture period, which served as additional food sources for catfish juveniles. In both scenarios, the fish reared at lower densities had significantly higher SGR than fish reared at higher densities. In the pond, the SGR of fish held at 228 and 457 m?3 were similar to each other but were significantly lower than those of fish held at 114 m?3. The zooplankton in ponds consisted mostly of copepods and cladocerans, in contrast to tanks, in which rotifers were more predominant. Per cent survival ranged from 85% to 89% in tanks and from 78% to 87% in ponds and did not differ significantly among stocking densities and between rearing systems. In conclusion, catfish nursery in cages suspended in tanks and ponds is density dependent. Catfish fry reared at 285 m?3 in tanks and at 114 m?3 in ponds had significantly faster growth rates than fish reared at higher densities. However, the desired fingerling size of 3–4 cm total length for stocking in grow‐out culture can still be attained at stocking densities of 457 m?3 in nursery pond and 571 m?3 in tanks.  相似文献   

9.
To assess the compensatory growth, a 10‐month pond experiment was conducted in which three species of Indian major carps, viz. Catla catla, Labeo rohita and Cirrhinus mrigala (1 : 1 : 1), were stocked at 7500 ha?1 and the fish were subjected to different restricted feeding and refeeding protocols, viz. Control (C): Continuously fed for 10 months; Treatment‐1 (T‐1): Initial supplementary feeding for 2 months+ No supplementary feeding for 1 month + Refeeding for 7 months; Treatment‐2 (T‐2): Initial supplementary feeding for 2 months + No supplementary feeding for 2 months + Refeeding for 6 months; and Treatment‐3 (T‐3): Initial supplementary feeding for 2 months + No supplementary feeding for 3 months + Refeeding for 5 months in triplicate ponds. At the end of experiment, 100% growth compensation was achieved in T‐2 for all the three carp species. Among all treatments, higher weight gain, PER and PPV and lower AFCR were also recorded in T‐2, resulting in maximum fish production. The restricted feeding had significant effect (P < 0.05) on whole body chemical composition of fish. From this study, it is concluded that in 10‐month pond culture of carp in fertilized pond, the T‐2 would be the best and most economic feeding strategy.  相似文献   

10.
Reported maximum carrying capacities of Tilapia nilotica reared in cages are Iow ranging from 10 to 70 kg/m3. This may be related to total numbers of caged fish reared in a body of water and not simply density per cage volume. An experiment was conducted to demonstrate such effects.
Sixteen cages in a 0.77 ha pond were stocked with T. nilotica at either 250, 500, 750, or 1,000 fish/cage for a total of 12,987 fish/ha. One cage in each of four 0.13 ha ponds was stocked with either 250 or 1,000 fish/cage for a total of 1,923 or 7,692 fish/hectare, respectively. Fish were fed a 32% protein diet at equal rates for 169 days. In the 0.77 ha pond, yield per cage was positively correlated with stocking density, while individual mean weights were negatively correlated with stocking density. However, among equal densities per cage between ponds, fish in the 0.13 ha ponds gained about 26% more than in the 0.77 ha pond. An interaction of the effects of density per cage volume and per pond area may have occurred.  相似文献   

11.
Nile tilapia (Oreochromis niloticus L.) was fed rice bran (RB), wheat bran (WB) and maize bran (MB) at 1.5% body weight. Fingerlings averaging 14 g were stocked at 19 462 fish ha?1 in three treatments with six replicates per treatment. Clarias gariepinus was stocked at 250 fish ha?1 to reduce the density of tilapia fry. Growth and economic performance were compared for 250 days in 0.08 ha fertilized ponds. Fish growth was highest (P < 0.05) in MB and least in RB treatment. Growth in WB treatment was intermediate. Feed conversion ratio in MB and WB treatments was similar (P > 0.05), but significantly higher (P < 0.05) than in RB treatment. Water quality parameters were similar (P > 0.05) among treatments. At retail price of US$ 1.28 kg?1 fish, returns above both variable and total costs from MB and WB treatments were positive, while those from RB were negative. However, at US$ 1.79 kg?1 fish, all test‐feeds had positive returns above variable and total costs. In conclusion, MB treatment produced the highest growth, but the highest profitability was obtained in the WB treatment. Under present study conditions, RB was not cost‐effective in the production of O. niloticus. A selling price of US$ 1.79 kg?1 fish is recommended.  相似文献   

12.
An experiment was conducted to evaluate the effect of using different types of organic manure on the plankton abundance, and growth and survival of Tilapia rendalli juveniles in ponds. Fish weighing 18.15±0.44 g were stocked into 12, 20 m2 ponds at 2 fish m?2 (40 fish pond?1). There were three replicate ponds per treatment (chicken manure, cattle manure, pig manure, and no‐manure as a control). After 84 days the T. rendalli in the chicken manure treatment were significantly larger and had higher net annual yields than those in the cattle manure, pig manure and no‐manure treatments. The survival rates were not significantly different across the treatments. Significantly higher amounts of chlorophyll a and higher numbers of zooplankton were found in ponds fertilized with the chicken manure treatment. The overall results obtained in this study suggest that the use of chicken manure produces better results than cattle and pig manure treatments on unfertilized ponds.  相似文献   

13.
A 117‐day feeding trial was conducted in ponds with juvenile Australian red claw crayfish (Cherax quadricarinatus) to evaluate the effects on growth, survival, body composition, and processing traits when fed diets containing three different protein levels (22%, 32%, and 42%), and the effects of feeding these diets on pond water quality. Juvenile crayfish (mean weight of 4.6±2.2 g) were randomly stocked into nine 0.02‐ha ponds at a rate of 500 per pond (25 000 ha?1), and each diet was fed to three ponds. There were two feedings per day, each consisting of one‐half of the total daily ration. At harvest, there were no significant differences (P>0.05) in the individual weight, percentage weight gain, or specific growth rate among treatments, which averaged 75.3 g, 1535%, and 2.38% day?1 respectively. Red claw fed the 42% crude protein diet had significantly higher (P<0.05) feed conversion ratio (7.34) compared with crayfish fed diets containing 22% (5.18) or 32% (5.13) crude protein, and had significantly lower percentage survival (46.1%) compared with red claw fed diets with 22% (61.1%) or 32% (58.2%) protein. Total yield was significantly lower (P<0.05) in red claw fed the 42% protein diet (640 kg ha?1) compared with red claw fed diets containing 22% (920 kg ha?1) or 32% (904 kg ha?1) protein. Mean total ammonia nitrogen (TAN) levels were significantly higher (P<0.05) in ponds with red claw fed the 42% protein diet (0.55 mg L?1) compared with ponds with red claw fed diets containing 22% (0.32 mg L?1) or 32% (0.38 mg L?1) protein. Mean total nitrite concentrations in ponds with red claw fed the 42% protein diet was significantly higher (0.05 mg L?1) compared with red claw fed diets containing 22% (0.01 mg L?1) or 32% (0.02 mg L?1) protein. These results indicate that a practical diet containing 22% (as fed basis) protein may be adequate for pond production of red claw when stocked at the density used in this study, and that a diet containing 42% protein adversely affected levels of TAN and nitrite, possibly reducing overall survival of red claw. Use of a diet with 22% protein may allow red claw producers to reduce diet costs and thereby increase profits.  相似文献   

14.
Four different fertilization frequencies, namely twice per week, once per week, twice a month and once a month, were used in ponds to assess their effects on nutrient release, pond productivity and fish biomass. All ponds received the same total fertilizer inputs during the experimental period of 60 days (cow dung 208.3 kg ha?1 week?1, TSP 9.8 kg ha?1 week?1, urea 6.0 kg ha?1 week?1). Studies have revealed that the highest values of fish biomass, specific growth rate (SGR), net primary productivity (NPP), plankton population and nutrients were observed in the ponds that were fertilized twice a month. A strong and significant correlation of fertilization frequency was observed with dissolved oxygen, biochemical oxygen demand (BOD), alkalinity, nutrient release, NPP, plankton density (no. L?1), fish biomass and SGR. The linear relationship between NPP and fish biomass/SGR for all the ponds was strong (r2= 0.88). Sediment chemistry revealed that O‐PO4, NO3‐N, organic carbon and electrical conductivity (EC) increased significantly (P<0.05) with a decrease in the frequency of fertilization, while alkalinity and calcium were high in ponds that were fertilized twice a month.  相似文献   

15.
An 18‐week study was conducted in 12, 0.1 ha ponds to evaluate the impacts of cyclic feeding regimes on hybrid striped bass (HSB) foodfish production and pond water quality. Approximately 840 HSB [mean weight (std.); 91.08 g (8.18)] were stocked into each pond (8400 fish ha?1; 3360 fish acre?1) and fed according to one of three feeding regimes. The three feeding regimes included a control (fed twice daily to apparent satiation), and cycles of 3 weeks feed deprivation followed by 3 or 6 weeks of feeding to apparent satiation (3/3 and 3/6 respectively). Compensatory growth (CG) was observed in both cyclic feeding treatments; however, the response was insufficient for the fish to completely regain lost weight. Final mean weight of control fish (477.9 g) exceeded (P<0.05) that of fish receiving the two cyclic treatments: 3/6 (404.7 g) and 3/3 (353.8 g). Specific growth rate (SGR) of fish in the 3/3 treatment increased during all three refeeding periods, and was significantly greater than controls during weeks 9–12 and weeks 15–18, which represent the refeeding phase of the second and third feeding cycles. Specific growth rate for fish in the 3/6 treatment was significantly higher than controls only during the first 3 weeks of the first feeding cycle. Hepatosomatic index and condition factor were highly responsive measures that closely followed the metabolic state of fish on the feeding cycle. Of the water quality variables measured, total phosphorus was 32% lower in ponds receiving cyclic feeding versus control ponds. Soluble reactive phosphorus was 41% and 24% lower in ponds offered the 3/3 and 3/6 cyclic feeding treatments, respectively, although, significant differences (P<0.10) were only observed between control and 3/3 treatment ponds. Overall, CG was observed in HSB foodfish grown in ponds, although 3 weeks of feed deprivation was excessive and did not allow for complete growth compensation. Weight loss during feed deprivation was influenced by pond water temperatures. Early season feed deprivation did not cause as much weight loss as during the second cycle later in the season. Further studies on shorter deprivation periods applied during moderate to low water temperatures are needed to identify feeding regimes that minimize weight loss and result in a complete CG response.  相似文献   

16.
The role of offering a commercial pelleted diet has been characterized as both an expensive organic fertilizer and as a selected food item for larval hybrid striped bass (palmetto), Morone saxatilis × Morone chrysops, culture operations. In this study, we examined the effects of providing a commercial diet on fish production and zooplankton dynamics during phase I culture in plastic‐lined ponds. We also sought to estimate relative dietary contribution of a commercial fish feed relative to natural pond biota using stable isotope tissue analysis. Palmetto bass were stocked into six 0.04‐ha plastic‐lined ponds at a rate of 125,000/ha. During the 31‐d culture period, ponds were fertilized with alfalfa pellets at a rate of 112 kg/ha/wk. At 14 d post‐stock (dps), Silver Cup Trout Fry diet was offered at a rate of 13.6 kg/ha/d and fertilization was discontinued in three ponds. Although mean final fish length was significantly greater within the fed treatment, no other production parameters were found to be different (P < 0.1). Following feed application, copepod concentrations within the fed ponds were greater in magnitude by 24 dps. Through stable isotope tissue analysis, we found a significant enrichment in both 13C and 15ν of fish, zooplankton, and Chironomidae larvae within the fed ponds (P < 0.10). Using a three‐source mixing model, the mean (±SE) percent composition of feed in the fish's isotopic signature increased from 5% ±2 to 20% ±6 within 16 d. Although fish production was not greatly affected through the addition of a commercial fish feed, enriched 13C and 15ν of fish tissue indicate that palmetto bass fingerlings increasingly utilized the prepared diets over time. However, based on the isotopic values of fish and potential food sources, it can be estimated that natural pond biota likely accounted for up to 80% of nutrient assimilation in the hybrid striped bass.  相似文献   

17.
Diets containing 28% and 32% crude protein were compared for pond‐raised channel catfish Ictalurus punctatus stocked at densities of 14,820, 29,640, or 44,460 fish/ha. Fingerling channel catfish with average initial weight of 48.5 g/fish were stocked into 30 0.04‐ha ponds. Five ponds were randomly allotted for each dietary protein ± stocking density combination. Fish were fed once daily to satiation for two growing seasons. There were no interactions between dietary protein concentration and stocking density for any variables. Dietary protein concentrations (28% or 32%) did not affect net production, feed consumption and weight gain per fish, feed conversion ratio, survival, processing yields, fillet moisture, protein and ash concentrations, or pond water ammonia and nitrite concentrations. Fish fed the 32% protein diet had slightly but significantly lower levels of visceral and fillet fat than fish fed the 28% protein diet. As stocking density increased, net production increased, while weight gain of individual fish, feed efficiency, and survival decreased. Stocking densities did not affect processing yield and fillet composition of the fish. Although highly variable among different ponds and weekly measurements, ponds stocked at the highest density exhibited higher average levels of total ammonia‐nitrogen (TAN) and nitrite‐nitrogen (NO2‐N) than ponds stocked at lower densities. However, stocking density had no significant effect on un‐ionized ammonia‐nitrogen (NH3‐N) concentrations, calculated based on water temperature, pH, and TAN. By comparing to the reported critical concentration, a threshold below which is considered not harmful to the fish, these potentially toxic nitrogenous compounds in the pond water were generally in the range acceptable for channel catfish. It appears that a 28% protein diet can provide equivalent net production, feed efficiency, and processing yields as a 32% protein diet for channel catfish raised in ponds from advanced fingerlings to marketable size at densities varying from 14,820 to 44,460 fish/ha under single‐batch cropping systems. Optimum dietary protein concentration for pond‐raised channel catfish does not appear to be affected by stocking density.  相似文献   

18.
Production characteristics of channel catfish (Ictalurus punctatus) reared in cages and open ponds were compared. Fish reared in open ponds had significantly better growth and food conversion ratios than fish reared in cages. Cages and open ponds stocked with fish which were closely graded in size produced fish with less size variability at harvest compared to ponds and cages stocked with nongraded and coarsely graded fish. The decrease in size variability at harvest was reflected in a greater proportion of marketable fish.  相似文献   

19.
The influence of fertilization and of fry stocking density on production of fingering walleye, Stizostedion vitreum, was evaluated in earthen ponds at North Platte State Fish Hatchery, North Platte, Nebraska. In 1990, five 0.4-ha ponds were fertilized with alfalfa pellets, and five were fertilized with soybean meal; four unfertilized ponds served as controls. All ponds were stocked with D2 (Dl = the day at hatch) walleye fry at 250.000ha. Differences in yield, number of fingerlings harvested, mean length, and mean weight amone treatments were not statistically significant (P> 0.05). In 691, two fertilization schedules (no fertilizer and fertilization with alfalfa pellets) and two fry stocking rates (250.000 and 375,000 fry/ha) were evaluated. Four ponds were used for each treatment. Statistically significant treatment differences were found in yield, number of fingerlings harvested/ha, average length, and average weight. Yield was higher in fertilized ponds compared with yield from unfertilized ponds at both stocking densities, but yield did not differ significantly between stocking density treatments given the same fertilizer treatment. Survival did not differ between density treatments, but total number of fish harvested was significantly greater from ponds stocked at the higher density. Fingerlings with the largest average weight were raised in fertilized ponds that were stocked at 250,00O/ha, while the smallest fingerlings were from unfertilized ponds that were stocked at 375,000ka. Days in culture interval, which varied among ponds by 9 days in 1990 and 10 days in 1991, was significantly correlated with most production variables in 1990 and with all production variables in 1991. Means of water quality variables were not significantly different between fertilized and unfertilized ponds in either year, but significant differences were found in means of three water quality variables between 1990 and 1991. Yield in both fertilized and unfertilized ponds in 1991 was less than in 1990.  相似文献   

20.
Four practical diets containing 2% of crude protein (CP) (180 and 280 g kg?1), with or without menhaden fish meal (FM), were fed to Australian red claw Cherax quadricarinatus during a 97‐day feeding trial. Growth, survival, body composition and processing traits of pond‐cultured red claw were determined. Juvenile red claw (mean individual weight of 5.75 ± 3.3 g) were randomly stocked into twelve 0.04‐ha ponds at a rate of 1000 per pond (25 000 ha?1), and each diet was fed to three ponds. At harvest, the final mean weight of red claw fed Diet 4 (0 g kg?1 FM and 280 g kg?1 CP) and Diet 3 (113 g kg?1 FM and 280 g kg?1 CP) was significantly (P < 0.05) higher (62.4 and 58.5 g, respectively) than red claw fed Diet 1 (73 g kg?1 FM and 180 g kg?1 CP; 51.7 g) and Diet 2 (0 g kg?1 FM and 180 g kg?1 CP; 53.0 g). Red claw fed diets containing 280 g kg?1 CP, with or without FM, had significantly higher percent weight gain (894 and 959%, respectively) compared to red claw fed 180 g kg?1 CP, with or without FM (778 and 799%, respectively). Feed conversion ratio, percent survival, and total yield among treatments, which averaged 3.55, 65.2%, and 724 kg ha?1 overall, were not significantly different. Results from this study indicate that pond‐cultured red claw stocked at 25 000 ha?1 can be fed a practical diet containing 280 g kg?1 CP with 0 g kg?1 FM if a combination of plant‐protein ingredients (soybean meal, distillers’ dried grains with solubles, and milo) is added; however, if the percentage of dietary protein level is 180 g kg?1, growth is reduced even if FM is added at 73 g kg?1 of the diet. Use of diets containing plant‐protein sources may help reduce diet costs to producers and thereby, increase profits.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号