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.
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   

2.
The results of two stocking density trials on the nursery and grow-out stages of Epinephelus tauvina (Family: Serranidae), in PVC-lined raceways are presented.
At the nursery stage, fry of 17.1 g initial mean weight showed no significant differences in growth rate, survival rate and condition factor when stocked at densities of 200 and 400 fish/m3 over a period of 52 days. Fish grew to mean weights of 61.7 and 63.7 g, giving growth rates of 0.86 and 0.90 g/fish/day and final biomasses of 12.1 and 2S.2 kg/m3 for densities of 200 and 400 fish/m3, respectively. Survival rates were excellent for both treatments at 98percnt; or greater. Food conversion efficiency was slightly improved at the higher density.
At the grow-out stage, E. tauvina of mean weights ranging from 150-170 g cultured for a period of 215 days grew better at a density of 5 fish/m3 than at densities of 20 and 60 fish/m3 (final size: 770, 560 and 450 g with growth rates of 2.8, 1.8 and 1.4 g/fish/day, respectively). Survival rates were higher at the two lower densities. Overall, total biomass increased with stocking density (3.9, 11.1 and 23.4 kg/m3, for 5, 20 and 60 fish/m3, respectively). These results indicate that hamoor has potential to be successfully cultured in raceways.  相似文献   

3.
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   

4.
Abstract— Australian red claw crayfish Cherax quudricarinurus were cultured in monoculture and in polyculture with male Nile tilapia Oreochromis niloricus in nine 0.02-ha earthen ponds. Red claw with an average weight of 7 g were stocked in all ponds at 2/ m2. Tilapia with an average weight of 19 g were stocked in six ponds at either 0.5 or 1/m2. A sinking 32% fish diet and dry alfalfa hay was provided to all ponds as feed and forage. After 135 d, red claw survival was similar (19–24%) in all treatments while average weights were 76 g in monoculture and 48 g in both polyculture treatments. Lower than expected survival was a result of stress caused by poor shipping conditions. Tilapia survivals were similar (84–90%) in all ponds and had an average weight of 403 g when stocked at 1/m2 and 444 g when stocked at 0.5/m2. Red claws are generally considered non-aggressive, especially when compared with other clawed crustaceans. This lack of aggressiveness is suggested as a cause for decreased growth in polyculture with tilapia.  相似文献   

5.
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   

6.
This present study was designed to investigate the effects of stocking density and water exchange on the growth rate, survival and performance index of L. setiferus postlarvae under controlled laboratory conditions. The experiment was done with postlarvae (PL10 to PL40) at densities of 50, 150, 250 and 350 shrimp/m2 and various different water exchanges rate per day (0, 6, 12 and 18%). The maximum growth rate was obtained for shrimp with 12% water exchange per day at all densities. A reduction of the maximum growth rate was observed in relation to density with the highest values in shrimp stocked in a density of 50 and 150 shrimp/m2 (mean value of 0.53 mg/d) and the lowest in shrimp stocked in a density of 350 shrimp/m2 (0.24 mg/d). The multiple regression equation obtained to relate performance index (growth rate* survival : PI), shrimp density (X1) and water exchange (X2) was: PI = 0.31 + (0.001) X1+ 0.039 X2+ 2.28 × 10−6 X12+ (−0.0017) X22+ (0.000026)X1X2, R 2= 0.78; P > 0.03. According to this equation the optimum shrimp density-water exchange comhination was between 5 to 12% of water exchange at stocking density of between 50 and 150 shrimp/m2. Salinity, ammonia-N and nitrite-N increased according to the time spent in tanks without water exchange. With no (0%) water exchange, water quality parameters measured were outside the optimum for L. setiferus postlarvae. The use of optimum density and water exchange in a nursery system for L. setiferus with optimum variables established is proposed.  相似文献   

7.
Abstract. The effect on the growth of freshwater angelfish, Pterophyllum scalare (Lichtenstein) (Pisces; Cichlidae), of different densities of population and diet compositions was studied. The results show that increasing the population density from 50 fish/m2 to 200/m2 significantly decreased the rate of growth of fingerlings, and that this effect is correlated to the size of fish. No significant differences were observed in growth between diets containing 37%, 41% or 47% protein. However, the addition of live food (artemia) to the diet significantly raised the growth rate, especially in the higher protein diets.
Body composition shows no changes during the growth periods, with a mean of 64·68% body protein, 35·47% dry weight fat and no significant differences in the percentage of residual ash through the growth period.
The food conversion rate was very low, ranging from 1·15 to 1·31. Total production increased with density, from 4·0g/m2/day (50 fish) to 13·7g/m2/day (200 fish) over a period of 60 days.  相似文献   

8.
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   

9.
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   

10.
ABSTRACT:   We investigated the effects of specific light wavelengths from light-emitting diodes (LEDs) on the growth of the dinoflagellate Heterocapsa circularisquama , which kills bivalves, and the diatom Skeletonema costatum , which is an important food source for bivalves. Growth of H. circularisquama was obviously inhibited at 590 nm and a photon flux density less than 75 μmol quanta/m2/s. However, growth of S. costatum was not suppressed by irradiance from any LEDs tested from near-ultraviolet to near-infrared wavelengths at 75 μmol quanta/m2/s. The growth rate of H. circularisquama in an experimental treatment group with irradiance provided by both cool-white fluorescent lamps (12:12 h L : D cycle) and a 590-nm LED (continuous irradiance) was 0.43/day. In the control group with irradiance provided only by cool-white fluorescent lamps (12:12 h L : D cycle), the growth rate was 0.63/day, indicating that growth of H. circularisquama was suppressed by 590 nm (less than 75 μmol quanta/m2/s) irradiance from the LED and the continuous irradiance. The use of 590-nm LEDs in bivalve culture at irradiance levels less than 75 μmol quanta/m2/s might encourage the growth of the useful diatom S. costatum without stimulating growth of the harmful dinoflagellate H. circularisquama .  相似文献   

11.
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   

12.
Abstract. Arctic charr, Salvelinus alpinus (L.), from the same full-sib family were reared under two different densities for 97days at 10°C. In one treatment density was adjusted every 2 weeks by means of a tank enclosure to a density of 50kg/m3. In the other treatment the density was allowed to increase as fish biomass increased to 50kg/m3. Density had no significant effect on the variation observed in individual fish weights over the course of the growth trial. Density had a significant effect on the relationship between fish weight and specific growth rate. The increasing density treatment had an overall higher mean specific growth rate of 0·1%/day.  相似文献   

13.
Australian red claw crayfish Cherax quadricarinatus were cultured in nine 0.02-ha earthen ponds at densities of l/m2, 3/m2 and 5/m2 for 158 d. Average weight at stocking was 3.2 g. All ponds were provided with a combination of hay and corn silage at a rate of 500 kg/ha per month and a commercial crayfish ration fed at 5%, decreasing to 2% of estimated biomass/d during the growing season. Overall survival rate was 72%, and did not differ among treatments. Final yields and average weights varied significantly with stocking density. Red claw averaged 67 g with an average pond yield of 475 kg/ha at l/m2. At 3/m2 and 5/m2, red claw averaged 48 g and 38 g, respectively, and yielded 1,020 kg/ha and 1,422 kg/ha, respectively.  相似文献   

14.
Effects of water temperature on red claw crayfish Cherax quadricarinatus spawning rates was evaluated for 3 mo at 22, 26 and 30 ± 1 C. A 20/m2 stocking density and a 1:2 M: F sex ratio was used. Spawning rate increased as temperature increased, with 30 C providing the highest spawning rate ( P < 0.05). Effects of stocking density and sex ratio on the reproduction of red claw crayfish were also evaluated at densities of 10.15 and 20/m2, with a sex ratio of 1:1, and at three sex ratios (1:1. 1:3 and 1:5 M: F) at a density 10/m2. Water temperature was maintained at 28 ± 1 C and photoperiod was maintained at 14L: 10D for 6 mo during the density and sex ratio experiments. Spawning rates were not significantly different ( P > 0.05) within the three stocking densities at a sex ratio of 1:1, nor were they different ( P > 0.05) for the three sex ratios at a density of 10/m2. Results revenled that densities as high as 20/m2 and sex ratios of 1 male to 5 females can be used to increase spawning per tank. Also, high temperature (28 ± 1 C) and long day lengths (14L: 10D) can be utilized to stimulate peak spawning rates, but high spawning rates cannot be maintained for more than about 3 mo.  相似文献   

15.
This study utilized enclosures (cylindrical, 5-mm wire mesh, O.5 m2 bottom surface area) placed over rice-forage substrates in experimental crawfish ponds to contain crawfish under typical pond culture conditions. Juvenile Procambarus clarkii were stocked at six densities (2, 4, 6, 10, 14, and 18 crawfish/m2) for 12-wk growth trials in October and again in February. Crawfish relied solely on the detrital food system for their nutritional needs. Supplemental feed was supplied to crawfish in additional enclosures at two of the test densities (2 and 10 crawfish/m2). The commercially formulated feed (25% crude protein) was fed (2.02 g dry feed/m2) 3 d/wk (Monday, Wednesday, Friday). All treatments were replicated with six enclosures. Crawfish growth was inversely correlated to culture density. Mean final weights for crawfish feeding from the detrital-system only were 15.3, 13.8, 11.2, 7.9, 7.2, and 5.8 g for crawfish densities of 2, 4, 6, 8, 10, 14, and 18/m2, respectively. Mean final weights for crawfish receiving supplemental feed were 20.7 and 12.4 g for densities of 2 and 10 crawfish/m2. When compared with density as a factor influencing growth, feed influenced growth less than density abatement. Supplemental feeding improved crawfish growth in detrital systems an average of 46%, while decreasing initial density improved growth an average of 80.5%.  相似文献   

16.
An experiment was conducted to investigate growth, survival and feed conversion of Florida red tilapia reared in floating cages in seawater under different feeding regimens. Twenty-four cages (1 m3) were anchored in a sea pass on Great Exuma, Bahamas, and each was stocked with 300 juvenile, monosex males (10 g mean weight). Growth was monitored every 14 days for 84 days. Fish were fed daily a floating pelletized diet (32% protein) at 4 programed rates representing 50, 70, 90, and 110% of the estimated satiation rate, ad libitum , and by demand feeders, with each treatment comprised of 4 replicate cages.
Final mean weight was significantly lower for the 50% treatment (94.1 g) than for all other treatments (range = 121.8–155.7 g). Final mean biomass per cage ranged from 24.2 to 39.4 kg/m3, and survival ranged from 98.2 to 99.8%.
Mean specific growth rate was significantly lower under the 50% programed feeding treatment (2.42%/day) than for all other treatments (range = 3.15–3.56%/day) while feed conversion ratios (dry weight/wet weight) were significantly lower under the 50% (1.57) and 70% (1.68) programed feeding treatments than under all other treatments (range = 1.98–2.26). Thus, maximum growth was achieved at feeding rates near satiation while feed conversion was improved at lower feeding rates. Under demand feeding, growth and feed conversion were not significantly different than those of the ad libitum , 100%, and 90% treatments.  相似文献   

17.
The paper reviews recent progress in larviculture of Atlantic cod and Atlantic halibut in different experimental enclosed seawater systems in Norway. More than 240,000 cod juveniles have been produced in a 270,000 m3 seawater pond. However, very promising production results of cod have been achieved in plastic enclosures with volumes > 100 m3. Halibut juveniles have been successfully produced in plastic enclosures and tanks by using natural zooplankton as food. The enclosure technique could be adapted to commercial scale production of juvenile halibut. However, scaling up experiments are necessary.  相似文献   

18.
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   

19.
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   

20.
Commercial-scale production of Florida red tilapia ( Oreochromis sp.) seed (eggs, sacfry, and fry) under methods that minimized freshwater usage was studied on Lee Stocking Island, Bahamas. Comparisons of seed production by broodstock held in low-salinity (LS = 5 ppt; mixed rain and ground water) and brackish-salinity (BS = 18 ppt; mixed ground and sea water) tanks (34 m2) showed that seed production over an 8 month period was significantly greater in LS (77.7 seed/m2/ day) than in BS tanks (47.4 seed/m2/day), with average proportion of brooding females and number of seed per clutch being greater in LS (26.9% and 763) than in BS tanks (19.8% and 643). While LS seed production was among the highest reported values for tilapias, BS production was within reported ranges for fresh and low-salinity tilapia hatcheries. Seed production per unit of low-salinity water (i.e., rain and/or groundwater) consumed in both LS (7,262 seed/m3) and BS (5,337 seed/ m3) tanks exceeded reported values. The results support the feasibility of commercial-scale production of Florida red tilapia seed under intensive methods and of salinities as high as 18 ppt in regions where fresh or low-salinity water resources are limited.  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