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1.
White sea bream Diplodus sargus L. is a fish species that develops dominance hierarchies and aggressive behaviour against its conspecifics. On the other hand, stocking density is known to affect social interactions, while an appropriate density for D. sargus efficient farming remains to be elucidated. For this purpose, juvenile D. sargus (14.3 g) were reared in 88.4 L tanks, for 10 weeks, under six rearing densities (10, 15, 20, 25, 30 and 35 fish tank?1). Water quality was not affected by rearing density. Best growth, in terms of final weight, specific growth rate, weight variation and food utilization, was achieved at 10 fish tank?1. At this treatment the lowest body water content, hepatosomatic and splenosomatic indices, higher body and liver lipid content were also observed. Brain neurotransmitter results indicated increased dopaminergic activity in populations held at higher rearing densities, while serotonergic activity was not affected. Moreover, no significant differences were detected for liver fatty acids. Results of the present study, compared with previously reported data, suggest that, within the range tested, the lowest realistic rearing density for juvenile white sea bream would be 10 fish tank?1. Higher rearing densities led to decreased growth, which seemed to be related to changes in intraspecific competition and social behaviour.  相似文献   

2.
The effects of tank color on the growth, stress responses, and skin color of snakeskin gourami (Trichogaster pectoralis) were investigated in this study. Fish with initial body weights of 5.03±0.00 g were reared in five experimental tank colors (white, red, green, blue, and black) for 8 weeks. Each tank color was tested in triplicate with an initial stocking density of 15 fish per tank. Fish were fed with commercial sinking pellets at 4% of the average body weight per day. Growth performance, feed utilization efficiency, stress indicators (hematocrit, blood glucose, plasma cortisol levels), and skin color parameters were investigated. The fish reared in blue tanks had a significantly higher average final body weight (9.73?±?0.14 g) and significantly lower average feed conversion ratio (3.42?±?0.12) than the fish reared in black tanks (P?<?0.05). The fish reared in black tanks exhibited higher average hematocrit (36.63?±?1.11%), blood glucose (48.33?±?1.45 mg dL?1), and plasma cortisol (9.00?±?0.56 μg dL?1) levels than those reared in the other tank colors. However, the blood glucose levels in only the fish reared in black tanks were significantly higher than those in the fish reared in the other tank colors. The fish skin color ranged from very pale (high skin lightness) in the white tanks to very dark (low skin lightness) in the black tanks, and 80% of the variation in skin lightness were explained by the tank lightness. The use of a blue tank resulted in normal skin color; hence, blue tanks will not affect the customer acceptance of the fish. Our study revealed that blue is the most appropriate tank color for culturing snakeskin gourami.  相似文献   

3.
To investigate the influence of stocking density on the growth and non‐specific immune responses of juvenile soft‐shelled turtle, Pelodiscus sinensis, three groups of turtles (initial body weight 74.2±12.2 g) were reared in 80 cm (L) × 40 cm (W) × 30 cm (H) tanks for 35 days at three stocking densities (StD), which were 1 individuals (ind.) tank−1 (3.13 ind m−2) for D1, 4 ind. tank−1 (12.5 ind m−2) for D2 and 6 ind. tank−1 (18.75 ind m−2) for D3 respectively. D1 was the control group. Turtles were weighted individually at the beginning and at the end of the trial. At the end of the rearing trial, non‐specific immune parameters were determined. The results showed that the heterophil:lymphocyte ratio (HLR) increased and the total plasma protein decreased with increasing StD, suggesting a stress response. Specific growth rate (SGR) significantly decreased with increasing StD. Non‐specific immune indicators such as blood cell phagocytic activity, serum haemolytic activity and serum bacteriolytic activity increased clearly at a higher StD, indicating a pattern of immunoenhancement. The results indicated that at StDs of 4 and 6 ind. tank−1, non‐specific immune responses were not suppressed compared with the control, but were inversely enhanced at the cost of growth reduction. A possible energy‐based trade‐off between growth and constitutive immunity may exist in soft‐shelled turtles.  相似文献   

4.
The effects of various environmental parameters on sexual maturation of two sea-winter Atlantic salmon (Salmo salar) were tested in two separate experiments. In the first experiment Atlantic salmon with initial mean individual weight 1.5 kg (smolt 13 months before) were reared for 8 months from June to February at different oxygen levels and stocking densities using continuous light. Oxygen levels of 5–7, 7.5–9.5 and 10–12 mg O2 l−1 and stocking densities starting at about 20, 30 and 40 kg m−3 and increasing as the fish grew to 80–90 kg m−3 for the highest densities were tested in a factorial design. Only male fish matured, and incidence of maturation among males varied from 4.1% to 25% between tanks. The highest percentage of mature males was found in the tanks with low stocking density. No clear effect on oxygen level was found.The second experiment lasted 20 months from seawater transfer in May until the fish weighed 3.3–3.5 kg. Two water current speeds (14–16 and 20–24 cm s−1) and two photoperiod regimes (LD 20:4) and continuous light (LL) were tested in a factorial design. Neither swimming velocity nor photoperiod affected growth rate. Continuous light reduced the incidence of sexual maturation. The average proportion of maturation among males was 8% and 25% under the LL and LD 20:4 regimes respectively. The fish reared under the LD 20:4 light regime had a significant lower condition factor and significant larger hearts than the fish reared under continuous light. Swimming velocity had no significant effect on the incidence of maturation. The results indicate that the swimming velocity must be higher than 0.5 BL s−1 in order to influence the energy stores. An important finding in this study is that light cues are not required for gonadal growth. The results also indicate that environmental factors can affect maturation even after the first sea-winter.  相似文献   

5.
Effects of light and tank colors on stress response of juvenile beluga sturgeon, Huso huso, was investigated by the measurement of some sero-haematological parameters and carcass chemical analysis. The analysis was based on the responses of 64 specimens (initial weight 98.83 ± 1.42 g) reared under white, red, green, or blue light, and 48 specimens reared in white, black, or blue tanks, all for 12 weeks. Blue/green light and black tanks produced positive effects on cortisol that can be related to physiological condition and stress.  相似文献   

6.
A study was carried out to investigate the effects of background colour on the growth performance, skin colour, haematology, physiological condition and non‐specific immune responses of goldfish, Carassius auratus. Goldfish were reared in tanks with four different background colours (white, black, blue and red) for 8 weeks. Fish growth performance markedly rose in white background compared with the other treatments. There was no significant difference in haematological parameters or plasma proteins concentrations between treatments. Plasma cortisol of fish reared in red background was significantly higher than that in black and white backgrounds. Plasma antiprotease and lysozyme activities were more than doubled in white and black treatments compared with the red and blue groups. The other immune parameters tested (plasma peroxidase, complement and bactericidal activities) did not significantly change between treatments. Skin carotenoid content and the intensity of fish skin colour extremely diminished in white background. This study revealed that red and blue backgrounds are chronically stressful and immunosuppressive in goldfish. White backgrounds will preferably be used for the culture of goldfish for best fish growth. However, a way to revert the colour loss of goldfish skin reared in white backgrounds remains to be investigated.  相似文献   

7.
Advanced fry of Indian carps and post-larvae of freshwater prawn were reared for 120?days in 18 small holding tanks using each treatment in triplicate as: (a) non-aerated and (b) aerated fresh human urine (0.01%), (c) cow manure (1.8?kg tank?1), mixed treatment with cow manure and human urine under (d) iso-phosphorus and (e) iso-nitrogenous conditions and (f) control. Examination of water quality, primary productivity of phytoplankton, plankton and fish growth from different treatments revealed that the total fish yield was maximum in the cow manure treatment (621.5?g?tank?1) followed by the mixed treatments under iso-nitrogenous (428?g?tank?1) and iso-phosphorus (333?g?tank?1) conditions. Fish yield in different treatments was the direct function of the gross and net primary productivity of phytoplankton which, in turn, were directly related to the concentrations of nitrate and phosphate levels of water as well as their ratios in different treatments employed.  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.
Striped bass, Morone saxatilis (Walbaum), larvae, although physoclistous as adults, initially need to inflate their swimbladders by passing ingested air through a pneumatic duct to the swimbladder. Failure to inflate the swimbladder results in swimbladder atrophy, dysfunctional buoyancy control, deformities, and poor larval survival and growth. The present investigation studied the effects of light intensity, tank colour and photoperiod on the initial swimbladder inflation success of striped bass. In the first experiment, newly hatched larvae were reared for 2 weeks in black or white 350-L circular tanks exposed to incandescent lighting at 163 or 10 lux. Larvae were fed Artemia from 6 days post-hatching (dph). The standard length, and oil globule and yolk areas were measured. Swimbladder condition and evidence of feeding were recorded. To study the effects of photoperiod on inflation, larvae were reared in black tanks exposed to either 8 h:16 h or 16 h:8 h light:dark photoperiods at 139 lux. Striped bass inflated their swimbladders between 6 and 9 dph at 17 oC. Inflation success was significantly higher in black tanks (65%) compared with white tanks (42%), but light intensity did not significantly affect swimbladder inflation. Larval growth and food consumption were better in black tanks, primarily because this treatment resulted in more larvae with inflated swimbladders, although larvae with uninflated swimbladders in black tanks were longer at 12 dph than larvae with inflated swimbladders in white tanks. Larvae that successfully inflated their swimbladders fed earlier and exhibited better growth than larvae with noninflated swimbladders. Larvae reared at higher light intensities used up yolk reserves faster. Exposing striped bass larvae to 8 h:16 h light:dark photoperiods resulted in higher inflation rates (55%) compared to larvae reared at 16 h:8 h light:dark photoperiods (30%). Therefore, black tanks and short photoperiods are preferable for early rearing of striped bass larvae to maximize swimbladder inflation success.  相似文献   

10.
The effects of aquarium background colour and feed colour on survival, growth rates and feed utilization efficiency of thinlip mullet (Liza ramada) larvae (0.035 g) were investigated in two experiments. In the aquarium background colour trial, 50 larvae were stocked in duplicates in 120 L glass aquaria filled with dechlorinated tap water. The outside walls and bottoms of each pair of the aquaria were covered with coloured paper sheets to achieve one of six colours (white, black, red, green, yellow and blue), while noncoloured aquaria served as a control. The fish were fed an experimental diet (35% crude protein) at a daily rate of 5% of their body weight (BW), twice a day for 8 weeks. The best growth rates, feed efficiency and survival were achieved in larvae reared in light‐coloured aquaria (white, noncoloured and yellow). Fish performance was significantly retarded in larvae reared in dark‐coloured aquaria (red, green, black and blue). Body composition was not significantly affected by aquarium colour. In a feed colour trial, duplicate groups of larvae (0.035 g) were stocked at 50 fish per 120 L aquarium and fed a test diet (35% crude protein) with six different colours [dark blue, red, yellow, light brown (control), light green and dark brown] at a daily rate of 5% BW, twice a day for 8 weeks. The best performance and survival were achieved in fish fed on dark‐coloured diets (red, dark blue and dark brown). Light‐coloured diets (yellow, light green and light brown) resulted in inferior performance. Body composition was not significantly affected by feed colour. These results suggest that light‐coloured tanks should be used for rearing thinlip mullet, L. ramada larvae, while dark‐coloured diets are more preferable to light‐coloured diets.  相似文献   

11.
We assessed the effects of light intensity and spectrum on the growth, development and survival of Dicentrarchus labrax larvae from 30 to 96 days after hatching. Twelve lighting regimes were applied using 0.3, 1 and 2 W/m2 full spectrum white, blue, red and green light. By day 66 of exposure, growth performance was significantly better in larvae reared under green or red light compared with white or blue light (p < 0.05), while it was significantly better at 2.0 W/m2 compared with 1.0 or 0.3 W/m2 (p < 0.05). Larvae reared under white or blue light had significantly more deformities (p < 0.05) than did larvae reared under light of other spectra, while larvae reared under 0.3 W/m2 light intensity had a significantly higher proportion of jaw malformations than reared under 1.0 and 2.0 W/m2 (p ? 0.05). Dicentrarchus labrax larvae subjected to green light showed significantly lower survival compared with the other light spectra (p < 0.05). Moreover, light significantly affected brain aanat1a, aanatt1b, mellc, mt1, mt2, gh, tsh and crf mRNA expression. Therefore, the red and green light groups (or under 2.0 W/m2) could improve the growth performance and enhance secretion of melatonin, gh and tsh, and reduce the proportion of jaw malformations.  相似文献   

12.
This study compared the effects of dietary l ‐carnitine and ploidy on growth performances and fatty acid content in rainbow trout (Oncorhynchus mykiss). Fish [initial body weight (BW) = 30 g] reared under high density (50 kg biomass m?3) were hand‐fed in triplicate (3 tanks treatment?1, 34 fish tank?1) twice a day, with three nutritionally identical diets containing 15, 200 or 530 mg l ‐carnitine kg?1 of diet. No significant growth differences were observed over a 56‐day grow‐out period, during which BWs increased threefold. Growth performances and survival were not significantly affected by either ploidy or dietary l ‐carnitine content, although daily growth index showed an increasing trend (2.52–2.65% day?1) with increasing dietary l ‐carnitine. Body l ‐carnitine content increased significantly with dietary l ‐carnitine content. Diploid fish had higher plasma ammonia (716–725 μmol L?1) and osmolality (297–303 mOsm) levels than triploid trout (523–649 μmol L?1 and 285–291 mOsm, respectively). l ‐carnitine, ploidy and their interaction showed to affect significantly the concentration of several fatty acids. Palmitoleic (16:1), oleic (18:1) and erucic (22:1) acids showed lower concentrations, while the eicosadienoic (20:2n‐6) and arachidonic (20:4n‐6) acids were elevated in liver of triploid fish. Eicosapentaenoic acid (22:5n‐3) was significantly higher in fish fed 200 mg than in fish fed 15 mg l ‐carnitine.  相似文献   

13.
A two‐factor experiment was performed to evaluate the effects of cage colour (black or white 0.5 m3 experiment cages) and light environment (natural sunlight or reduced level of natural sunlight) on the skin colour of darkened Australian snapper. Each treatment was replicated four times and each replicate cage was stocked with five snapper (mean weight=351 g). Snapper exposed to natural sunlight were held in experimental cages located in outdoor tanks. An approximately 70% reduction in natural sunlight (measured as PAR) was established by holding snapper in experimental cages that were housed inside a ‘shade‐house’ enclosure. The skin colour of anaesthetized fish was measured at stocking and after a 2‐, 7‐ and 14‐day exposure using a digital chroma‐meter (Minolta CR‐10) that quantified skin colour according to the L*a*b* colour space. At the conclusion of the experiment, fish were killed in salt water ice slurry and post‐mortem skin colour was quantified after 0.75, 6 and 22 h respectively. In addition to these trials, an ad hoc market appraisal of chilled snapper (mean weight=409 g) that had been held in either white or in black cages was conducted at two local fish markets. Irrespective of the sampling time, skin lightness (L*) was significantly affected by cage colour (P<0.05), with fish in white cages having much higher L* values (L*≈64) than fish held in black cages (L*≈49). However, the value of L* was not significantly affected by the light environment or the interaction between cage colour and the light environment. In general, the L* values of anaesthetized snapper were sustained post mortem, but there were linear reductions in the a* (red) and b* (yellow) skin colour values of chilled snapper over time. According to the commercial buyers interviewed, chilled snapper that had been reared for a short period of time in white cages could demand a premium of 10–50% above the prices paid for similar‐sized snapper reared in black cages. Our results demonstrate that short‐term use of white cages can reduce the dark skin colour of farmed snapper, potentially improving the profitability of snapper farming.  相似文献   

14.
In this study, the physiological response and growth performances of Acipenser ruthenus were investigated after a long‐term background colour adaptation (12 weeks). Twelve groups of 10 individuals with initial mean body weight of 183 g were reared in black, dark blue, grey and white tanks (three replicates for each colour). At the end of the experiments, growth (initial body weight, final body weight, weight gain per cent, food efficiency ratio, protein efficiency ratio, specific growth rate), blood (cortisol, glucose, pO2, pCO2, pH, haematocrit, osmolality, triglycerides, cholesterol, total lipids) and liver (hepatosomatic index, total lipids, glycogen) parameters were analyzed. Plasma cortisol in the dark‐adapted sterlet (21.95 ± 3.9 ng mL?1) was significantly lower than those in white‐adapted fish (39.44 ± 6.5 ng mL?1), whereas there were no significant differences in cortisol levels between the grey‐adapted fish (23.05 ± 4.1 ng mL?1) and dark blue‐adapted fish (24.2 ± 3.6 ng mL?1). A remarkable increase in mean of body weight (%) was detected in dark‐adapted sterlet (45.2 ± 3.2) being 27.67%, 12.1% and 11.8% higher than the white, grey and dark blue‐adapted fish respectively. The obtained results verified that different background colours lead to different growth performances and physiological responses of starlet, depending on rearing conditions.  相似文献   

15.
Background colour influences the growth performance and feed utilization of various fish species. In the current study, the effects of different aquarium backgrounds (transparent, white, black, red, green and blue) on growth performance, feed utilization, digestive enzyme activities, flesh quality, carcass composition and haematological parameters were investigated in Asian seabass (Lates calcarifer). The fish (16.17 ± 0.02 g initial body weight) were distributed into eighteen glass aquaria (6 treatments × 3 replications) with the various background colours and reared for 10 weeks. At the end of the experiment, positive growth performance and feed utilization were observed in fish reared against transparent, white, black or green backgrounds, while negative effects were noted for fish reared on the remaining treatments (p < .05). Modulation of the main digestive enzymes was observed across the six treatments, indicating different strategies for utilizing nutrients by the fish. The activity ratio of trypsin to chymotrypsin was highest in the fish reared against a black background, followed by a white background. Flesh quality, in terms of protein synthesis capacity and protein turnover rate, indicated a significant improvement in the fish reared against white, black and green backgrounds, while the contents of myosin and actin were similar across the six colour treatments. Carcass composition and haematological parameters showed no negative effects in either of the preferred treatments. These findings indicate that the most suitable background colours for rearing Asian seabass are black, followed by white and green, while transparent, red or blue backgrounds are unsuitable.  相似文献   

16.
The aim of this study was to evaluate the effects of hatchery‐tank colours (white, yellow, red, blue, green and black) on the performance of larval culture of Macrobrachium amazonicum. The larvae were fed daily with newly hatched Artemia nauplii. The hatchery‐tank colours affected the light level inside the tanks, the consumption of Artemia nauplii (AN), larval development, survival, mass gain and productivity of postlarvae (PL). The overall consumption of Artemia nauplii per larva during the larval cycle was 30% and 45% higher in the green and red tanks respectively. The significant variation of AN consumption among tank colours (P = 0.0006) indicates that M. amazonicum larvae are visual predators. Survival was higher in the black, blue and green tanks, reaching more than 75%. However, the highest productivity was obtained in the black tanks (80.1 PL L?1). Lighter coloured tanks and excess luminosity (more than 2 μmol s?1 m2 at tank bottom) appear to be important stress factors for larvae, contributing to reduce survival and productivity. The results indicate that rearing M. amazonicum in black tanks will improve larvae condition, ensure greater productivity of postlarvae and lower Artemia consumption, increasing technological and economic viability.  相似文献   

17.
Seedstock‐costs of the freshwater prawn Macrobrachium rosenbergii can represent >50% of the total production costs. The purpose of this study was to evaluate the effect of culture tank colouration on survival, metamorphosis rate, weight and time required to reach the postlarval (PL) stage. Newly hatched prawn larvae were stocked into eighteen 16‐L plastic culture tanks at a density of 30 L?1. Tank colours evaluated were red, black, white, blue, green and yellow. Larval prawns were fed brine shrimp (Artemia franciscana) nauplii and a supplemental diet. Data indicated that larval tank colour had no significant impact (P>0.05) on the final PL size or days required to reach PL stage. However, total survival was significantly higher (P<0.05) in red and green tanks (84% and 78% respectively) than in white and blue tanks (56% and 44% respectively). Survival in the yellow and black tanks (71% in both) was not significantly different (P>0.05) from the red, green or white treatments, but was significantly higher (P<0.05) than the blue treatment. This could have a significant financial impact on commercial hatchery, and growout production, as most larval tanks currently in use are blue or black.  相似文献   

18.
The effects of different tank background colours (green, black and white) on the growth performance and body coloration of juvenile river cafish, Pangasius hypophthalmus, were examined in this study. The experimental fish with an initial body weight (BW) 0.13 ± 0.05 g and total length (TL) 2.54 ± 0.37 cm were used, and groups of 15 fish per tank were randomly distributed. The experiment was conducted for 20 days as a triplicate for each treatment. Survival, growth in BW, body weight gain (BWG), total length (TL), total length gain (TLG), specific growth rate (SGR), condition factor, feed conversion ratio (FCR), swimming speed, body coloration and stress response were evaluated. River catfish reared in white and green tanks attained significantly higher BW, BWG, TL, TLG and SGR compared to the black tank. The white tank attained significantly better FCR compared to the black tank. River catfish showed the most active swimming behaviour in the green tank (5.49 ± 1.32 cm/s) while the least in the white tank (3.37 ± 0.93 cm/s). Body coloration of river catfish in the black tank showed almost pure black body coloration (75.59 ± 9.08), followed by the green tank (126.23 ± 17.46) and the white tank (148.19 ± 10.51). However, there was no significant difference in the stress level of river catfish reared in white and black tanks and insignificant to those reared in the green tank. The findings in this study showed that the white and green background colour tanks can be used for promoting growth of river catfish culture while the black background colour tank can enhance body coloration that is suitable as ornamental fish.  相似文献   

19.
The effect of increasing fish loading (decreasing water exchange rate, while holding fish stocking density constant) on growth, survival and feed conversion ratio was determined for two size groups of the orange‐spotted grouper Epinephelus coioides (Hamilton). Fingerlings (124.3–145.8 g initial body weight) and subadults (990.6–1147.1 g initial body weight) were reared in 1‐m3 circular tanks for 14 weeks. For the fingerlings experiment, three loading rates of 0.5, 2 and 6 kg L?1 min?1 were used, while in the experiment with subadults, the loading rates were 1, 3 and 6 kg L?1 min?1. The mean growth rate of fingerlings ranged from 1.60 to 2.14 g fish?1 day?1, and survival was high (95–100%); however, there were no significant differences (P > 0.05) as a result of the different loading rates. Similar results were obtained in the subadults experiment, in which the growth rate (3.10–4.90 g fish?1 day?1) and survival (86.7–100%) were not significantly (P > 0.05) affected by the different loading rates. In both experiments, the feed conversion ratios were also not affected significantly by the loading rates. These results show that water exchange in aerated, flowthrough tanks can be reduced to as low as 6 kg L?1 min?1 without adversely affecting growth, survival and feed conversion of fingerling and subadult groupers.  相似文献   

20.
Slow growth and losses to bird predation and infectious diseases in winter can compromise the profitability of silver perch farming. To evaluate over‐wintering silver perch (Bidyanus bidyanus) in a recirculating aquaculture system (RAS), fingerlings (38 g) were stocked in either cages in a pond at ambient temperatures (10–21 °C) or tanks in the RAS at elevated temperatures (19–25 °C) and cultured for 125 days. Mean survival (96%), final weight (146 g), specific growth rate (1.07% day?1) and production rate (28.1 kg m?3) of fish in the RAS were significantly higher than for fish over‐wintered in cages (77%, 73 g, 0.53% day?1, 11.1 kg m?3). Fish from both treatments were then reared in cages for a further 129 days. Final mean weight of fish originally over‐wintered in the RAS was 426 g, while fish over‐wintered in cages were only 273 g. To determine optimal stocking densities, fingerlings (11.8 g) were stocked at 500, 1000 or 1500 fish m?3 in tanks in the RAS and cultured for 124 days. Survival was not affected, but growth was significantly slower and feed conversion ratio higher at 1500 fish m?3 compared with 500 or 1000 fish m?3. Results demonstrate that over‐wintering silver perch in an RAS can produce large fingerlings for grow‐out in early spring. This strategy could eliminate bird predation, reduce losses to diseases and shorten the overall culture period.  相似文献   

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