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1.
This research was conducted to investigate the effect of stocking density on the growth performance and yield of Oreochromis niloticus in cage culture in Lake Kuriftu. The treatments had stocking densities of 50 (50F), 100 (100F), 150 (150F), and 200 (200F) fish per m?3. All treatments were in duplicate. Juveniles with an average weight of 45. 76±0.25 g were stocked in the treatments. The fish were fed a composite mixture of mill sweeping, cotton seed, and Bora food complex at 2% of their body weight twice per day using feeding trays for 150 days in powdered form. The growth performance of O. niloticus was density dependent. The final mean weight of O. niloticus ranged 147.76±0.28–219.71±1.42 g and the mean daily weight gain was 0.69±0.01–1.15±0.02 g day?1. Fish held in cages with lower density were heavier than the ones held at higher densities, and showed higher weight gain and daily weight gain. The most effective stocking density, in terms of growth parameters, was 50 fish m?3. The gross yield (4.5–20.55 kg cage?1) showed a significant difference with increasing stocking density (P<0.05). Moreover, the apparent food conversion ratio (2.48–7.22) was significantly affected by stocking density (P<0.05). However, survival rate was not affected by stocking density (P>0.05). It can be concluded that the most effective stocking densities were at 50 fish m?3 cage for larger size fish demand in a short period and 200 fish m?3 for higher gross production with supplementary feed.  相似文献   

2.
The purpose of this study was to evaluate the resistance to vibriosis, growth, survival and tolerance to stress of the selected prawn, second generation, compared to a non‐selected control. The first generation of selected giant freshwater prawn, which has 10.4% higher of resistance, was used to attain disease resistant freshwater prawn (Macrobrachium rosenbergii) generation through challenge test‐based selection. Resistance test was conducted by infecting the prawn (mean body weight of 10.29 ± 1.40 g) with pathogenic Vibrio harveyi (5 × 105 cfu prawn?1). The growth and survival of the prawn were evaluated by rearing the two populations of prawn in both nursery and grow‐out phases. Stress tolerance test was done by evaluating the viability of postlarvae exposed to environmental stressors, i.e. temperature, salinity, NH3 and formaldehide. Post‐challenge survival of the selected prawn (55.0 ± 5.0%) was about 46% higher than that of the control (37.5 ± 7.5%). The survival of the selected prawn in nursery culture (77.16 ± 0.841%) was significantly higher (p < .05) than that of the control (51.31 ± 2.938%), while the survival in grow‐out culture was similar (p > .05). The growth of selected prawn (4.99 ± 0.03% day?1) was significantly higher than that of the control (4.81 ± 0.05% day?1). There was no difference between treatments on the tolerance level against the tested environmental stressor. Overall data suggested that the selected prawn showed better performance in growth and resistance against vibriosis.  相似文献   

3.
The compensatory growth response of the European sea bass (Dicentrarchus labrax) that faced cycling starvation and restricted ration was assessed. Juveniles (10.5 g) were stocked into 15 tanks at a density of 25 fish per tank. Five different feeding regimes were tested on triplicate groups of fish: CSatiation: control fed for 60 days without deprivation, CRestricted: 25% restricted feeding, S‐R: 1 day starvation then 4 days CRestricted feeding, R‐F: 1 day CRestricted feeding then 4 days CSatiation feeding, and, finally, S‐F: 1 day starvation then 4 days CSatiation feeding. The specific growth rate of fish in the CSatiation (2.5 ± 0.06% day?1), S‐F (2.5 ± 0.11% day?1) and R‐F (2.4 ± 0.18% day?1) were significantly higher than that of CRestricted (2.2 ± 0.05% day?1) or S‐R (2.0 ± 0.01% day?1). Fish in S‐F group were able to achieve catching up with the CSatiation. There was no significant difference in feed conversion rates but R‐F and S‐F consumed approximately 34% more feed than CSatiation following the first re‐feeding day. Although, the highest lipid content was observed in CSatiation (14.4%), S‐R (33.3% dry matter) had the highest water content compared with the CSatiation and CRestricted (37.8% and 36.9% dry matter respectively). In conclusion, it may be concluded that sea bass has rapid response to cycling starvation/re‐feeding and that a 25% restricted feeding ratio is insufficient to invoke a compensatory growth response in sea bass.  相似文献   

4.
Oyster seed production in hatchery and nursery systems has relied on the production of microalgae, which is cost effective, but often unpredictable. The development of a satisfactory substitute diet would greatly reduce production costs of hatchery operations. Single cell detritus (SCD) production from seaweed (Porphyra haitanensis) may have great potential as a partial substitute for microalgae. In this experiment, a technique for producing SCD was developed and the product was used as a partial substitute for microalgae for the nursery culture of juvenile tropical oysters (Crassostrea belcheri) in a hatchery setting. A reverse osmosis technique was used on ground seaweed (particle size <200 μm) immersed in freshwater and placed on a shaker at 100 rpm for 2 h before being returned to seawater. This technique was shown to be highly effective for SCD production with a density of 33.7 ± 7.0 × 104 cell mL?1 and the percentage of SCD particle diameter <20 μm was 89.2%. A partial replacement of microalgae with SCD was found to be unsuitable for nursing oyster larvae. For juvenile oysters (shell width 1.85 ± 0.03 mm and shell length 1.78 ± 0.06 mm) substituting 75% of microalgae with SCD showed lower absolute shell growth, and lower daily yields and survival rates when compared to rates substituting 50% or lower substitution with SCD, or 100% microalgae (P < 0.05). It was found that substituting 50% of the traditional microalgae with SCD produced from seaweed (P. haitanensis) can be used as a partial microalgae substitute for the nursery culture of the juvenile tropical oyster.  相似文献   

5.
Two feeding trials were carried out to determine the optimum feeding rates in juvenile olive flounder, Paralichthys olivaceus, at the optimum rearing temperature. Fish averaging 5.0 ± 0.11 g (mean ± SD) in experiment 1 and 20.2 ± 0.54 g (mean ± SD) in experiment 2 were fed a commercial diet at the feeding rates of 0%, 3.0%, 4.0%, 4.25%, 4.5% and 4.75% body weight (BW) day?1 and satiation (5.52% BW day?1) in experiment 1 and 0%, 1.0%, 2.0%, 3.0% and 3.5% BW day?1 and satiation (4.12% BW day?1) in experiment 2 at 20 ± 1 °C. Both feeding trials lasted for 2 weeks. Results from experiment 1 indicated that weight gain (WG) and specific growth rate (SGR) of fish fed to satiation were significantly higher than those of fish fed at other feeding rates while feed efficiency (FE) and protein efficiency ratio (PER) of fish fed at 4.25% BW day?1 were significantly higher than those of fish fed to satiation and fish fed at 3.0% BW day?1 (P < 0.05). In experiment 2 WG, SGR and PER leveled out after the feeding rate of 3.5% BW day?1 whereas FE reached a plateau at 3.0% BW day?1. anova of FE indicated that the optimum feeding rates in 5.0 and 20 g juvenile olive flounder could be 4.25% and 3.0% BW day?1, respectively. Broken line analysis of WG suggested the optimum feeding rates of 5.17% and 3.47% BW day?1 in 5.0 and 20 g fish, respectively. Therefore, these results indicated that the optimum feeding rates could be >4.25 but <5.17% BW day?1 for 5.0 g, and it could be >3.0 but <3.47% BW day?1 for 20 g size of juvenile olive flounder at the optimum rearing temperature.  相似文献   

6.

The Catarina scallop Argopecten ventricosus is a highly valued resource. Although its hatchery spat production has already been reported, the effects of initial larval stocking density have never been reported for production purposes. This study evaluates A. ventricosus growth and survival in triplicate using three stocking densities: low (LD; 2 larvae mL?1), medium (MD; 4 larvae mL?1), and high (HD; 6 larvae mL?1). Three-day old larvae were reared in 18-L plastic carboy at 25.6?±?0.5 °C and fed with a microalgal blend of Isochrysis galbana and Chaetoceros calcitrans (1:1 cell number ratio) for 7 days, equivalent to 10 post-fertilization days (PFD). Higher specific growth rate was recorded at LD (15.8?±?0.2%) after 8 PFD of culture compared to MD (1.6?±?0.5%) and HD (4.1?±?1.8%) densities. The least time required for 60% of the larvae to reach the pediveliger stage was recorded at LD condition (10 PFD). Higher survival was recorded at HD (58.8?±?3.1%) at 8 PFD compared to MD (53.5?±?3.1%) and LD (43.9?±?3.0%). After 8 PFD, stocking density was highly related to larval growth and survival. To increase production and growth, and reduce the time required to reach pediveliger stage, stocking density should start with 6 larvae mL?1 and be reduced to 2 larvae mL?1 at 7 PFD.

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7.
In this study, we aimed to investigate the effects of water temperature and stocking density on the survival, feeding and growth of the juveniles of the hybrid yellow catfish from Pelteobagrus fulvidraco (♀) × Pelteobagrus vachelli (♂) using the parameters as follows: survival rate (%), feeding rate (% day?1), feed conversion ratio, specific growth rate (% day?1), coefficient of variation (%), productivity (P, g m?3 day?1) and condition factor. We reared the juvenile fish (3.25 ± 0.21 g) at 12 water temperature levels and six stocking density levels (each level included three aquaria in two batches of experiments). The results showed that all groups survived at a temperature range of ≤35°C during a 46‐day experimental period, and they could achieve a high growth at a water temperature range of 26–32°C. The optimal temperature for growth was 29.8°C. Productivity peaked at a stocking density of 1.9 kg m?3. Our results indicated that the hybrid is very suitable for commercial aquaculture.  相似文献   

8.
The fingerling‐rearing experiment of the threatened catfish, Mystus cavasius was carried out at different stocking densities in earthen nursery ponds. Twelve‐day‐old fry were stocked at 200 000 ha?1 in treatment‐1 (T1), 250 000 ha?1 in treatment‐2 (T2) and 300 000 ha?1 in treatment‐3 (T3) respectively. The mean length and weight of fry at stocking was 1.24 ± 0.25 cm and 0.11 ± 0.04 g respectively. Fry in all the experimental ponds were supplemented with SABINCO nursery feed for the first 14 days and starter‐I feed for days 15–56. The physico‐chemical parameters and plankton population of pond water were within the suitable level for fish culture. Growth in terms of final weight, final length, weight gain, length gain and specific growth rate and survival of fingerlings were significantly higher in T1 than those in T2 and T3. Feed conversion rate was significantly lower in T1 followed by T2 and T3 in that order. Significantly higher number of fingerlings was produced in T3 than that in T2 and T1. Even then, consistently higher net benefits were obtained from T1 than those from T3 and T2. Among the treatments evaluated, 200 000 fry ha?1 was the best stocking density considering the highest growth, production and net benefits of fingerlings of M. cavasius in nursery ponds.  相似文献   

9.
Stock density is one among the most important factors in aquaculture that directly influences the growth of organisms; however, there is limited information about the effects of stocking density on growth performance of sea cucumber Holothuria tubulosa (Gmelin, 1788) that has a commercial potential and represents a new species for aquaculture. In this study, we investigated the effect of stocking densities on the growth performance of juvenile H. tubulosa (40.3 ± 3.34 g) in laboratory conditions. Stocking densities were selected as 6, 15 and 30 ind m?2 with total biomass 253.3 ± 0.18, 601.2 ± 0.11 and 1201.4 ± 0.15 g m?2 respectively. We monitored the growth by wet weights and calculated the growth performance through weight gain, growth rate, specific growth rate, relative weight gain, coefficients of variation and survival rate during 8 weeks of research period. We found that individual mean weight gain in 6 ind m?2 group was approximately 29.53 g while it was 3.03 g and ?4.36 g for 15 ind and 30 ind m?2 groups respectively. Results have shown that the specific growth rate tends to decrease as the number of individuals in unit area increases. The final mean weight, growth rate, specific growth rate, relative weight gain and coefficients of variation were significantly different among treatment groups. In conclusion, a density of 6 ind m?2 is recommended for stocking juvenile H. tubulosa under rearing conditions. Stocking density of 15 ind m?2 is not favourable for long term as the growth rate is negligible where 30 ind m?2 should be avoided in tank‐based rearing units.  相似文献   

10.
The feasibility of co‐culturing the sea cucumber Holothuria leucospilota Brandt in a subtropical fish farm was investigated in a field study. Sea cucumbers were cultured in the fish farm in cages suspended at 4 m deep (suspended culture) and directly on the seafloor (bottom culture). The survival and growth of the sea cucumbers were monitored twice during the 3‐month, summer experimental period (May 26–August 14, 2010). Results showed that the suspension‐cultured sea cucumbers exhibited excellent survival rate (100%) during the whole study period. There also occurred no mortality in the bottom‐cultured sea cucumbers during the first culture period (May 26–July 13); but all these died from anoxia caused by water column stratification during the second culture period (July 14–August 14). The specific growth rate of the bottom‐cultured sea cucumbers (1.05 ± 0.21 % day?1) was nearly double that of the suspended culture animals (0.57 ± 0.21 % day?1) during the first culture period, and the growth rates of the suspended culture sea cucumbers in the second culture periods (0.46 ± 0.24 % day?1) was only a little lower than that of the first period. The sea cucumbers H. leucospilota could ingest and assimilate sediment with high organic matter content with an average assimilation efficiency of 14.9 ± 3.9%. This study indicated that fish farm detritus can be effectively used as a food source for the sea cucumber and that it can be turned into a valuable secondary crop in the form of the sea cucumber biomass.  相似文献   

11.
Columnaris disease is an important bacterial disease of commercially grown channel catfish, Ictalurus punctatus. Copper sulphate (CuSO4) has been shown to be therapeutic and prophylactic as a water treatment for columnaris disease. Copper is an essential dietary component in animal feeds and CuSO4 is typically included in base diets; a study was conducted to evaluate whether fish feed supplemented with additional CuSO4 at 0, 40 and 80 mg kg?1 of diet and fed at a daily rate of 3% body weight would affect survival to columnaris disease. Results indicate fish fed the copper‐supplemented diet for 2 weeks significantly increased survival following F. columnare challenge. This increase appeared to be dose‐dependent. The mean per cent survival (±SEM) for fish fed the base diet (unsupplemented) for 2 weeks and then challenged was 2.0% ± 1.1. Fish fed the base plus 40 mg CuSO4 kg?1 had a mean survival of 22.0% ± 11.0. Fish fed the base plus 80 mg CuSO4 kg?1 had a mean survival of 29.3% ± 13.4. The mean per cent survival for fish fed the base diet for 4 weeks and then challenged was 28.3% ± 9.0. Fish fed the base plus 40 mg CuSO4 kg?1 for 4 weeks had a mean survival of 12.5% ± 6.3. Fish fed the base plus 80 mg CuSO4 kg?1 for 4 weeks had a mean survival of 40.5% ± 8.1. There was a significant effect after 4 weeks with fish fed the base plus 80 mg CuSO4 kg?1 mg not with 40 mg kg?1.  相似文献   

12.
This study was conducted to assess the optimum clam size and substratum type for the culture of Galatea paradoxa. The experiment was conducted over a 90‐day period at the Volta Estuary, Ghana. Three size classes of G. paradoxa categorized as small (27.6 ± 0.4 mm), medium (36.8 ± 0.4 mm) and large (50.0 ± 0.6 mm), were used to ascertain the effect of a sandy and muddy substratum on growth performance and survival. Growth increased from the small‐sized clams to the large‐sized clams at 2.54, 3.03 and 3.43 g, respectively, over the experimental period. Growth was higher (P < 0.05) in the muddy substratum (3.58 g) compared with sandy (2.41 g). Similarly, the specific growth rate increased from 0.99% day?1 in the small‐sized clams to 1.36% day?1 in the large‐sized clams. Survival rates were significantly higher (99.4%) for the large‐sized clams compared with the medium (78.8%) and the small‐size clams (74.1%). There was significant interaction between the size class and the substratum type with a trend towards increasing survival rate from the small to the large size clams in both substrata. The survival rate was lower in the muddy substratum (71.4%) compared with the sandy substratum (96.7%). The yield was significantly higher in the muddy (2.01 kg m?2 90 day?1) compared with sandy substratum (1.87 kg m?2 90 day?1). The results of this study indicate that the culture of small‐sized clams is best practiced on sandy substratum due to their elevated survival rates, whereas the muddy substratum appears most suitable for the culture of larger clams (>40 mm) because of their relatively higher survivorship and better growth performance.  相似文献   

13.
Harvesting practices of the clam Chionista fluctifraga show a decline in commercial size and densities, but no strategies have been developed to maintain clam beds. Aquaculture represents an alternative for preserving this resource. Adult clams from commercial grounds were used as broodstock. Conditioning, induction of spawning, cultivation of larvae, settlement of eyed larvae and nursing of postlarvae were performed in the hatchery for producing spat. Larvae and postlarvae were used to measure increase in shell height and data were fitted to exponential growth models. Spat were placed in floating trays and maintained in off‐bottom cultivation for 9 months. Samples of clams and tissues were collected monthly to measure absolute growth, shell height increase and a condition index. Larvae, postlarvae and juveniles showed exponential growth patterns. Mean shell height increased about 0.030 mm day?1 during larval and post‐larval stages and 0.049 mm day?1 during field cultivation. Pediveligers (height 215 ± 83 μm) entered metamorphosis at days 9–13 after fertilization, and postlarvae reached 3011.7 ± 325.5 μm (height) at day 60. After field cultivation, survival was about 95%; juvenile shell height was 20.6 ± 2.2 mm, and total weight was 5.3 ± 0.7 g. Growth rates were superior to natural conditions and the condition index was high throughout the study. Our results show that spat of C. fluctifraga can be produced in the hatchery, and that field production can be maintained in off‐bottom trays until reaching commercial size. Aquaculture activities for this species need to be established and evaluated.  相似文献   

14.
Feeding copepods during early larval culture stages of marine fish has proven to be advantageous for growth and survival of marine finfish larvae. However, commercial availability of most copepods is limited; thus, there is an impetus to evaluate promising copepod species to meet the diverse dietary demands of various marine fish. The marine cyclopoid copepod, Oithona colcarva, was isolated out of zooplankton samples taken from waters within Tampa Bay, Florida. Once isolated, trials were conducted to determine the appropriate culture parameters for producing nauplii to feed marine fish larvae. The effects of temperature (22°C, 26°C and 30°C), salinity (15, 20, 25, 30 and 35 g L?1), stocking density (0.5, 1.0, 2.0, 4.0 and 8.0 individuals mL?1) and diet (Nanno 3600 microalgae paste, Colurella adriatica, Rhodomonas lens, Tisochrysis lutea, Chaetoceros gracilis and/or Tetraselmis chuii) on nauplii production during a single life cycle of reproducing individuals were examined. Results of those trials indicated that a culture temperature of 30°C and a salinity of 30 g L?1 were advantageous for maximum nauplii production. Furthermore, a diet containing a 1:1:1 mixture of T. lutea, C. gracilis and T. chuii and a stocking density of at least 8 individuals mL?1 were identified as beneficial. The results of these trials, the potential for large‐scale culture and observations on the performance of marine fish larvae fed Oithona colcarva nauplii are discussed.  相似文献   

15.
With the objective to develop an indoor tank seed rearing system for pearlspot (Etroplus suratensis), effects of three stocking densities in presence or absence of soil base were evaluated on growth, weight variation, survival and body composition in a 60‐day trial. The experiment had a 3 × 2 factorial design with three levels of stocking density (150, 300 and 450 fish m?3) and two levels of soil base (with and without) in triplicates. Pearlspot fry (27.5 ± 0.5 mm/0.39 ± 0.02 g) were stocked in experimental tanks (Length×Breadth×Height: 0.65 × 0.50 × 0.48 m) and fed with a formulated diet containing 29.85% crude protein. Increasing the stocking density from 150 to 450 fish m?3 significantly decreased the growth (average body weight and total length), daily weight gain, specific growth rate and survival (P < 0.001) and increased the feed conversion ratio (P < 0.01). Significantly lower growth and survival were observed in treatment having soil base compared with that of without soil base (P < 0.001). However, coefficients of variation at harvest weight and body composition of fingerlings were independent to stocking density and presence or absence of soil base (P > 0.05). A significant positive interaction effect of stocking density and presence or absence of soil base was observed on average body weight (P < 0.05) and survival (P < 0.001) of pearlspot fingerlings. This study suggests that stocking density of 150 fish m?3 without soil base in tanks would be appropriate for raising pearlspot fingerlings in brackishwater indoor seed rearing system.  相似文献   

16.
An 8‐week feeding trial was conducted to assess dietary protein and lipid levels on growth performance, feed utilization and body composition of juvenile red‐spotted grouper (7.85 ± 0.03 g fish?1). Nine semi‐purified diets were formulated containing varying protein levels (440–520 g kg?1, dry matter) and lipid levels (60–120 g kg?1, dry matter). The weight gain of juvenile Epinephelus akaara was affected by dietary protein (p = .005) and its interaction with dietary lipid (p = .020). Viscerosomatic index, intraperitoneal fat ratio and whole‐body lipid level increased with increasing dietary lipid level (p < .001). Nitrogen retention was not affected by dietary protein and lipid, while lipid retention decreased with increasing dietary lipid level (p < .001). The plasma blood urea nitrogen increased with increasing dietary protein level (p = .003). This study showed that diet with 520 g kg?1 protein and 60 g kg?1 lipid with 30.58 mg kJ?1 P:E provided a maximal growth for this species. Moreover, an increase in dietary lipid levels (from 60 to 90 g kg?1) could reduce the protein requirement (from 520 to 480 g kg?1) without affecting the growth performance, while higher fat deposition was observed in fish fed high‐lipid diets.  相似文献   

17.
Commercially valuable sea cucumbers are potential co‐culture species in tropical lagoon environments, where they may be integrated into established aquaculture areas used for seaweed farming. In the current study, wild‐caught juvenile sea cucumbers, Holothuria scabra, and red seaweed Kappaphycus striatum were co‐cultured on Zanzibar, United Republic of Tanzania. Sea cucumbers (97 g ± 31 SD, n = 52) were cultured in mesh enclosures at initial cage stocking densities of 124 ± 21 SD and 218 ± 16 SD g m?2 under seaweed culture lines. Over 83 days, individual growth rate (1.6 g d?1 ± 0.2 SD) of sea cucumbers at low stocking density was significantly higher (χ2 = 8.292, d.f. = 1, P = 0.004) than at high‐stocking density (0.9 g d?1 ± 0.1 SD). Seaweed individual growth rates [6.27 (±0.3 SE) g d?1] were highest in co‐culture with sea cucumber at low density but did not differ significantly from high sea cucumber density or seaweed monoculture treatments (χ2 = 3.0885, d.f. = 2, P = 0.2135). Seaweed growth varied significantly (χ2 = 35.6, d.f. = 2, P < 0.0001) with sampling period, with the final sampling period resulting in the highest growth rate. Growth performance for seaweed and sea cucumbers (χ2 = 3.089, d.f. = 2, P = 0.21 and χ2 = 0.08, d.f. = 1, P = 0.777 respectively), did not differ significantly between monoculture and co‐culture treatments, yet growth in co‐culture was comparable with that reported for existing commercial monoculture. Results indicate H. scabra is a highly viable candidate species for lagoon co‐culture with seaweed. Co‐culture offers a more efficient use of limited coastal space over monoculture and is recommended as a potential coastal livelihood option for lagoon farmers in tropical regions.  相似文献   

18.
We evaluated the effect of intensification on Macrobrachium rosenbergii hatchery in clear water recirculating system. Larvae were raised in 120‐L cylindrical tanks coupled with 30‐L biofilters. We performed two experiments in randomized blocks. In the first, we tested the stocking densities of 50, 70 and 90 newly hatched larvae L?1. Survival did not differ by anova (P = 0.343), but productivity increased with the intensification (P = 0.038). In the second experiment, we tested the stocking densities of 80, 100, 120 and 140 newly hatched larvae L?1. Survival decreased (P = 0.039) as density increased, but productivity did not differ (P = 0.317). The period of culture ranged from 22 to 23 days. The intensification did not influence water quality parameters or larval development. Survival decreased with the intensification and the space showed to be a limiting factor on tanks stocked with 90 larvae L?1 or more. Productivity curve shows an increase from 50 to 100 larvae L?1 and tended to reach plateau on stocking densities higher than 100 larvae L?1. In addition, the intensification improved the use of Artemia cysts by decreasing the superfluous feeding. Thus, we recommend stocking of 80 to 100 newly hatched larvae L?1 as the best option for M. rosenbergii hatchery in clear water recirculating system.  相似文献   

19.
First feeding success is critical to larval marine finfish and optimization of live feed densities is important for larval performance and the economics of commercial hatchery production. This study investigated various rotifer feeding regimes on the prey consumption, growth and survival of yellowtail kingfish Seriola lalandi larvae over the first 12 days post hatch (dph). The common practice of maintaining high densities of rotifers (10–30 ind. mL?1) in the rearing tank was compared to a low density feeding technique, where 5–8 ind. mL?1 of rotifers were offered. A ‘hybrid’ feeding regime offered rotifers at the high density treatment until 5 dph and the lower feeding densities thereafter. There was no significant difference in larval survival (hybrid: 28.9 ± 7%, low density: 17.3 ± 5% and high density: 17.2 ± 9%) or growth (hybrid: 6.12 ± 0.18 mm, low density: 6.03 ± 0.10 mm and high density: 6.11 ± 0.23 mm) between treatments. Rotifer ingestion was independent of rotifer density throughout the trial and increased with larval age, with larvae at 4 dph ingesting 22 ± 1.5 rotifers larvae?1 h?1 and by 11 dph ingesting 59 ± 1.6 rotifers larvae?1 h?1. These data demonstrate that from first feeding, yellowtail kingfish larvae are efficient at capturing prey at the densities presented here and consequently significant savings in rotifer production costs as well as other potential benefits such as facilitation of early weaning and improved rotifer nutritional value may be obtained by utilizing lower density rotifer feeding regimes.  相似文献   

20.
Garlic, Allium sativum L., extract administered as a therapeutic bath was shown to have antiparasitic properties towards Neobenedenia sp. (MacCallum) (Platyhelminthes: Monogenea) infecting farmed barramundi, Lates calcarifer (Bloch). The effect of garlic extract (active component allicin) immersion on Neobenedenia sp. egg development, hatching success, oncomiracidia (larvae) longevity, infection success and juvenile Neobenedenia survival was examined and compared with freshwater and formalin immersion. Garlic extract was found to significantly impede hatching success (5% ± 5%) and oncomiracidia longevity (<2 h) at allicin concentrations of 15.2 μL L?1, while eggs in the seawater control had >95% hatching success and mean oncomiracidia longevity of 37 ± 3 h. At much lower allicin concentrations (0.76 and 1.52 μL L?1), garlic extract also significantly reduced Neobenedenia infection success of L. calcarifer to 25% ± 4% and 11% ± 4%, respectively, compared with 55% ± 7% in the seawater control. Juvenile Neobenedenia attached to host fish proved to be highly resistant to allicin with 96% surviving 1‐h immersion in 10 mL L?1 (15.2 μL L?1 allicin) of garlic extract. Allicin‐containing garlic extracts show potential for development as a therapy to manage monogenean infections in intensive aquaculture with the greatest impact at the egg and larval stages.  相似文献   

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