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1.
A 16‐day experiment was designed to find the best combination of water temperature (27, 30, 33°C) and daily duration of food availability (12, 18, 24 h) for larval tench (Tinca tinca) growth and survival. Larvae with an initial mean size of 5.7 mm total length (TL) and 0.7 mg wet body weight (BW) were stocked at 15 L?1. Larvae were fed in excess with live Artemia nauplii with the period of food availability lasting 12, 18 or 24 h daily. The largest final larval size was recorded at 27 and 30°C in groups fed for 24 h a day (17.7 and 17.9 mm TL, 76.1 and 77.7 mg BW, respectively). The combination of the highest temperature and the longest daily food availability was the only set of conditions under which final larval survival was affected (95.4% survival; 98.7–99.9% under all other conditions). The combination of water temperature of about 28.6°C and continuous food availability is recommended as the optimum combination for rearing T. tinca larvae under controlled conditions. Providing continuous food supply to fish larvae under aquaculture conditions was also advantageous in helping to mitigate the effects of slower growth relative to developmental progress, which can occur at high water temperatures. However, should one wish to limit the daily feeding period to 12 h per day, the use of a water temperature between 27.4 and 27.9°C would be the best solution.  相似文献   

2.
In a laboratory experiment at 28 °C, four commercial starters (Carp Starter, Uni Starter, Perla Plus, Asta) were fed intensively to 11-month-old juvenile tench Tinca tinca of initially 41 mm TL and 0.70 g BW, over a period of 120 days. Frozen chironomid larvae were fed to fish below satiation as a reference diet for comparison of the fish body chemical composition. Final survival rates of 99–100% and satisfactory growth were attained with all dry diets, ranging from 73.3 (Carp Starter) to 84.8 mm TL (Asta) and from 5.39 (Carp Starter) to 8.09 g BW (Perla Plus). External body deformities of up to 96.4% specimens appeared in those fed Uni Starter, Carp Starter and Perla Plus, whereas 0% were recorded for Asta and chironomids. Fish in groups with deformities showed significantly elevated lipid content in their bodies, lower ash content and higher condition coefficient values. Juveniles in groups without deformities did not substantially change lipid content, but the ash content increased. Thus, among four dry diets studied, only Asta starter can be fed effectively and safely to juvenile tench reared intensively under controlled conditions.  相似文献   

3.
The experiment was designed to determine the combined effect of fish diet and water temperature on juvenile tench Tinca tinca (L.). Three diets were used: commercial dry diet for fish Aller Futura (diet F); frozen Chironomidae larvae (diet C); and Aller Futura substituted with Chironomidae at a ratio of 3:2 (dry weight; diet FC). Daily food rations and duration of the experiment were adjusted to temperatures of 20°C, 23°C and 26°C based on a correction factor q equal to 1.000, 0.779 and 0.609 respectively. The experiment lasted 92, 72 and 56 days for the respective temperatures. No mortality occurred. The highest relative growth rates were found at 26°C in diets F and FC. The lowest food conversion ratio of 1.12–1.22 (recalculated for dry weight of feed diet) was determined in fish fed diet F at 23°C and 26°C. A high value of condition index appeared to be the early warning of decreasing biological quality of fish and deformities. The lowest incidence of fish with deformities (IDef) was found in groups fed diet C (<1%), while the highest (90%) in fish fed diet F at 26°C. A lower share of dry diet in the fish food and a lower water temperature led to a lower IDef. Thus, amount of dry feed in fish diet was the major factor inducing body deformities, while water temperature only modified the effects of the dietary factor. Diet C at 23–26°C was the most cost‐effective of the tested combinations of diet and temperature.  相似文献   

4.
A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P > 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P > 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.  相似文献   

5.
Three commercial starters (Carp Starter, Uni Starter and Perla Plus) and one non-commercial, with frozen Chironomidae larvae as a reference diet, were evaluated for the intensive rearing of juvenile lake minnow Eupallasella perenurus, a cyprinid fish that is critically endangered in Poland. The growth, condition, survival, body deformities, and chemical body composition were studied. The 90-day laboratory experiment was performed at 22 °C with fish that were initially 24.6 mm (mean total lenth (TL)) and 0.11 g (mean body weight (BW)). Satisfactory fish growth was attained with all of the diets; however, the largest (p ≤ 0.05) final size (48.5 mm TL, 1.55 g BW) and the lowest condition coefficient (K = 1.34) were noted in fish fed the non-commercial starter. The final survival rates were very high (97.5–100%). Skeletal deformities (in 74 to 92% fish) were recorded exclusively in fish fed commercial starters. All commercial starters resulted in considerably higher lipid content and lower ash content than did the non-commercial starter and the reference diet. This suggests that both these factors might be responsible for body deformities. The present results proved that only the non-commercial starter is suitable for juvenile E. perenurus rearing under controlled condition, and that none of the commercial starters can be recommended.  相似文献   

6.
Five isoproteic (54.8%) and isolipidic (24.1%) microdiets, which varied in their docosahexaenoic acid (DHA) content (0.25%, 0.75%, 1.64%, 1.99% and 3.17%; dw), were manufactured to determine its effects on longfin yellowtail Seriola rivoliana larvae in terms of fish biological performance, whole body fatty acid profile and incidence of skeletal anomalies from 30 dah (11.31 ± 1.79 Total Length, TL) to 50 dah (19.80 ± 0.58 mm TL). The inclusion of dietary DHA up to 3.17% (dw) improved larval resistance to air exposure, although DHA did not significantly affect fish final growth or final survival. Indeed, high levels of dietary DHA (1.99% and 3.17%, dw) tended to increase the incidence of skeletal anomalies in S. rivoliana larvae, albeit no significant differences were observed. Furthermore, the occurrence of severe anomalies such as kyphosis and lordosis, was mainly associated to the larvae fed the highest levels of dietary DHA. In terms of survival, increasing dietary DHA levels did not significantly affect longfin yellowtail survival rate, despite a tendency for enhanced survival. The results of the present study proved that the inclusion of dietary DHA in inert diets up to a 3.17% (dw) and a DHA/EPA ratio above 3.1 increased the final survival and stress resistance in S. rivoliana larvae.  相似文献   

7.
This study aimed to investigate the effects of a superoptimal temperature on growth, body composition, body size heterogeneity, and relationships among these factors in juvenile yellowtail. Fish (mean body weight?=?24 g) were tagged individually and reared for 70 days under two different water temperature regimes [optimal (25 °C) and superoptimal (30 °C)]. After rearing, fish reared at 30 °C showed lower survival, less food, feed and protein utilization, significantly lower growth performance, and a lower hepatosomatic index than fish raised at 25 °C. Variations in body indices among individuals were larger for fish reared at 30 °C than for fish reared at 25 °C. Mean whole body protein content was significantly lower in fish reared at 30 °C than fish reared at 25 °C. In addition, several glucogenic and/or aromatic amino acids were lower in fish reared at 30 °C than in fish reared at 25 °C. Whole body lipid levels tended to be lower in fish with lower body weight reared at 30 °C. These results suggest that fish raised at 30 °C will have lower growth performance, and lower concentrations of specific amino acids. Moreover, heterogeneity in body size and body lipid content is expanded by a superoptimal temperature.  相似文献   

8.
Passing times of two different types of feeds were determined in cases of wels (Silurus glanis) by measuring the body weight at three different temperatures. Fingerlings, 38.03 ± 8.04 g, were fed by an artificial dry feed (commercial catfish feed) or forage fish. The treatments were carried out (11 fish/aquaria) in 3 replicates. Fish were individually tagged by pit tags. Temperatures applied were the following: 15, 20 and 24 °C. The appetite of fish highly depended on temperature. At 15 °C, only 42.4 % of the experimental fish accepted the granulated feed, while this ratio was 90.9 % in the forage fish fed group. At higher temperatures, 100 % of the experimental fish accepted feed in both feeding groups. The daily mean value of consumed feed at 15 °C was 3.20 % of body weight in the case of forage fish and 1.36 % in the case of dry feed. At 24 °C, this ratio was 10.68 % of body weight in cases of forage fish and 4.46 % in cases of artificial feed. At low temperature (15 °C), the quantity of consumed feed met the measurement’s error threshold, which made the determination of passing time uncertain. At 20 °C, the evacuation started 20 h after feeding and lasted for 18 h, while at 24 °C, it started 11 h after feeding and lasted for another 16 h.  相似文献   

9.
The effect of stocking density on the survival and growth of pikeperch, Sander lucioperca (L.), larvae was examined in two consecutive experiments. In experiment I, 4-day-old larvae [body wet weight (BW): 0.5 mg; total body length (TL): 5.6 mm] were reared in 200-l cylindro-conical tanks in a closed, recirculating system (20 ± 0.5°C) at three stocking densities (25, 50 and 100 larvae l−1) and fed a mixed feed (Artemia nauplii and Lansy A2 artificial feed) for 14 consecutive days. At densities of 25 and 100 larvae l−1, growth rate and survival ranged from 2.7 to 1.9 mg day−1 and from 79.2 to 72.3%, and fish biomass gain ranged from 0.6 to 2.0 g l−1, respectively. There were two periods of increased larval mortality: the first was at beginning of exogenous feeding and the second during swim bladder inflation. In experiment II, 18-day-old larvae (BW: 35 mg; TL: 15.6 mm) obtained from experiment I were reared under culture conditions similar to those of experiment I, but at lower stocking densities (6, 10 and 15 larvae l−1). The fish were fed exclusively with artificial feed (trout starter) for 21 consecutive days. At densities of 6 and 15 larvae l−1, the growth rate and fish biomass gain ranged from 28.8 to 23.1 mg day−1 and from 2.0 to 3.3 g l−1, respectively. The highest survival (56.5%) was achieved at a density of 6 larvae l−1. Mortality at all densities was mainly caused by cannibalism II type behaviour (27–35% of total). In both experiments, growth and survival were negatively correlated and fish biomass gain positively correlated with stocking densities. The present study suggests that the initial stocking density of pikeperch larvae reared in a recirculating system can be 100 individuals l−1 for the 4- to 18-day period post-hatch and 15 individuals l−1 for the post-19-day period.  相似文献   

10.
ABSTRACT

The effect of photoperiod (24L:00D, 12L:12D, and 00L:24D) and temperature (22 ± 1°C and 28 ± 1°C) on performance of Clarias gariepinus larvae was tested. Larvae weighing 3.2 ± 0.24 mg were cultured in aquaria at a stocking density of 20 fish L?1 and fed twice a day on catfish starter diet (40% CP) at 10 % BW day?1. Highest mean weight gain (31.00 mg), SGR (7.56% day?1), and survival (83%) were achieved at photoperiod and temperature combination of 00L:24D and 28 ± 1°C. Percent survival of larvae differed significantly (p < .05) among treatments with optimal survival of (83%) in treatment combination of 28 ± 1°C and 00L:24D, while lowest survival (40%) in treatment combination of 22 ± 1°C and 24L:00D.  相似文献   

11.
This study aimed to analyse the effects of different water temperatures on the growth, survival and blood physiological parameters of Lophiosilurus alexandri. Juveniles measuring 12.6 ± 0.5 cm and weighing 30.6 ± 3.6 g were subjected to four water temperature regimes: 23, 26, 29 and 32°C with four replicates. The animals were fed twice daily with formulated diet. The experiment lasted for 35 days. Survival was 100% at all water temperatures, and the best temperature for growth was estimated to be 27.8°C using a quadratic regression model. The estimated temperatures for the best feed conversion and highest feed consumption rates were 26.2 and 28.8°C respectively. The fat visceral‐somatic index was highest at 32°C. The highest haemoglobin and haematocrit values were 29.4 and 32.1°C respectively. For plasma protein and cholesterol, the lowest values estimated were 23.9 and 24.1°C respectively. Glucose and liver nitrogen content increased with rising temperature. Higher values of total ammonia in the water were observed at higher temperatures. No effects of temperature were seen on the amounts of muscle dry matter, nitrogen, energy content and triglycerides or on the hepatosomatic index. Water temperature has an important role in the developmental and blood physiological parameters of juvenile L. alexandri, and the quadratic regression model showed that the appropriate temperature for growth is between 27 and 28°C.  相似文献   

12.
This study tested the effects of constant and varying temperatures on newly hatched yellowtail kingfish Seriola lalandi larvae in two experiments. In Experiment I, four constant temperatures (21, 23, 25, and 27 °C) were tested under fed or unfed conditions with the fish age from the day of hatch to 24 days post hatch (DPH). Temperatures at 25 and 27 °C reduced the time of fish to reach irreversible starvation, but did not affect the percentage of fish that were able to ingest food. Fish survivals at 21 and 23 °C were significantly higher than those at 25 °C by 24 DPH, but all fish died at 27 °C by 24 DPH in the treatment with food. In Experiment II, three constant temperatures (21, 23, and 25 °C) and two varying temperatures (21–23 and 21–25 °C) were compared using fish from hatch to 28 DPH. On 4 DPH, fish ingested more rotifers, but from 6 to 9 DPH, fish ingested fewer rotifers at 25 °C than at other temperatures. On 19 and 23 DPH, fish ingested more Artemia at 25 °C than at other temperatures. At 25 °C, fish selected for Artemia nauplii earlier than at other temperatures. Fish length and survival between constant temperatures (21 and 23 °C) were not significantly different, but fish survival at the constant 21 °C or at the 21–25 °C varying temperature was significantly higher than that at the constant 23 °C or at the 21–23 °C varying temperature. This study indicates that within the range of temperature tested, the optimal temperature for the first feeding larvae is 21–23 °C after hatch and mortality is likely to occur at ≥25 °C in the first 10 DPH, but fish grew faster at 25 °C after they adapted to the increasing temperature.  相似文献   

13.
The present study was undertaken to examine the long-term effect of continuous light and constant temperature and their interaction on growth, feed intake, gill Na+, K+-ATPase (NKA) activity and early sexual maturation in Atlantic salmon pre- and post-smolts. The fish (mean initial weight = 15.9 g ± 0.4 SE) were reared on two photoperiods (continuous light, LL and simulated natural photoperiod, LDN, 60°25′N) and on two constant temperatures (average 8.3 and 12.7 °C) from June to July the following year. This resulted in four experimental groups abbreviated as LL8, LL12, LDN8 and LDN12. Growth in freshwater was highest in the LL12 group and final weight of this group was 70–330 % higher than in the other experimental groups, and our findings further demonstrate that the growth-enhancing effect of continuous light alone corresponds to a 4.5° increase in temperature. Overall, the highest feed intake was registered in the LL12 group, whereas no differences in feed intake or growth were observed between the LL8 and LDN12 groups, and the lowest feed intake and growth in the LDN8 group. Both temperature groups on LL developed peak levels in gill NKA activity in October–November, 4–5 months prior to the natural season for the parr–smolt transformation. Fish at 12 °C showed peak levels in NKA activity 4–6 weeks before the fish on 8 °C. The proportion of mature males was higher at 12.7 °C (66 %) compared to 8.3 °C (11 %). Highest maturation was seen at LL12 (82 %). For the salmon industry, this means that long-term rearing at LL and 12.7 °C will improve growth but also leads to higher maturation proportion. By rearing fish at LL8, it is, however, possible to achieve high growth and low maturation simultaneously.  相似文献   

14.
Temperature influenced the developmental rate, survival and early growth of eggs and embryos of spotted wolffish, Anarhichas minor (Olafsen), an interesting candidate for cold water cultivation. The total incubation period decreased from 220 days at 4 °C (880 daydegrees), to 177 days at 6 °C (1062 daydegrees) and 150 days at 8 °C (1200 daydegrees) in these experiments. The proportion of normal embryos and survival of eggs until hatching were highest when the eggs were incubated at 6 °C. During the incubation period, the embryo and yolk sac size at 280 daydegrees was not significantly different but at 850 daydegrees the embryo size was inversely related to temperature and the remaining yolk sac size positively correlated with the incubation temperature. The transformation of yolk to body mass during incubation appeared to be most efficient at 4 °C, and the embryos hatched with a larger visible yolk sac at 6 and 8 °C. The largest larvae (wet‐weight) hatched from the largest eggs and the egg groups incubated at the lowest temperature (4 °C). There was no effect of temperature on meristic characters. During 6 weeks post‐hatching, all larvae from the three temperature groups were fed formulated dry feed in excess at 8 °C in low water‐level raceway systems. During startfeeding, the larvae from eggs incubated at the lowest temperature (4 °C) showed the highest growth rates (SGR). Best survival of larvae was noted among batches incubated at 6 °C.  相似文献   

15.
ABSTRACT

To determine the minimum age/size at which Southern Flounder, Paralichthys lethostigma, can safely be moved to outdoor rearing facilities in Texas, we examined survival of simulated temperature drops in two distinct life stages: premetamorphic larvae and two size classes of postmetamorphic juveniles (small = 9.8 ± 0.3 mm in TL; large = 19.7 ± 0.6 mm). Temperature was lowered by ?0.33°C/h to 4°C, 7°C, or 10°C, held for 48 h and then raised at +0.33°C/h back to normal rearing temperature. Fish were monitored daily for survival. Larger postmetamorphic flounder had high survival for all temperature treatments (89%–100% survival), whereas both premetamorphic larvae and smaller postmetamorphic juveniles had low survival (<30%) for all temperature treatments.  相似文献   

16.
This study tested a choice feeding model for Nile tilapia that allowed the selection of a higher or lower protein content in the diet depending on water temperature. Nile tilapia were reared in twelve 200-L tanks for 63 days with 12 fish (body weight 38 g/fish at start) per tank. Two temperatures (22 or 30°C) and two color combinations (yellow and red each) for a two-component diet containing 30% (low) and a 38% (high) crude protein content based on dry matter were used. High water temperature (30 vs. 22°C) resulted in a significantly higher feed rate (1.93 ± 0.123 and 1.26 ± 0.100%, respectively), body weight gain (39.3 ± 4.29 and 4.75 ± 0.66 g, respectively), final body weight (70.3 ± 9.31 and 43.0 ± 7.49 g, respectively), and feed efficiency (55.4 ± 6.09 and 14.6 ± 2.86%, respectively), as well as protein efficiency ratio (1.687 ± 0.186 and 0.450 ± 0.087, respectively), regardless of color codes. No significant differences of color codes on growth parameters, body composition, and fatty acid profile were seen. Higher water temperature (30 vs. 22°C) only had an effect on percentage-specific fatty acids of total fatty acids of the whole body (biggest difference: C16:0, 20.5 ± 1.00 and 17.4 ± 1.11%, respectively). Therefore, water temperature clearly influences growth and fatty acid composition of the body.  相似文献   

17.
A 74‐day trial was undertaken to evaluate the effects of temperature (16 and 22 °C) and dietary protein/lipid ratio on the performance of juvenile Senegalese sole (mean body weight: 6.4 g). Four experimental diets were formulated to contain two protein levels (550 g kg?1 and 450 g kg?1) combined with two lipid levels (80 g kg?1 and 160 g kg?1). Growth was higher at 22 °C and within each temperature in fish fed diets 55P8L and 45P16L. Feed efficiency, N retention (% NI) and energy retention (% EI) were higher at 22 and at both temperatures in fish fed diet 55P8L. Temperature affected whole‐body composition, with dry matter, protein, lipid and energy being higher and ash lower in fish kept at higher temperature. Independently of temperature, whole‐body lipid, energy and ash were higher and protein was lower in fish fed the high‐lipid diets. Visceral and hepatosomatic indices were not affected by diet composition but were higher in fish kept at 16 °C. Liver glycogen and lipid contents and activities of glutamate dehydrogenase, alanine and aspartate aminotransferases were not affected by diet or water temperature. Malic enzyme (ME) and glucose 6‐phosphate dehydrogenase activities were higher in fish fed the low‐lipid diets. ME activity was higher at lower temperature. In conclusion, increasing water temperature from 16 to 22 °C improves growth and feed efficiency of Senegalese sole juveniles; regardless of water temperature, the diet with 550 g kg?1 protein and 80 g kg?1 lipid promoted the best growth and feed efficiency.  相似文献   

18.
Duplicate groups of tench (Tinca tinca) juveniles (mean weight 0.69 g) were fed at 28 °C for 70 days either a commercial formulated diet, Futura, or frozen Chironomidae larvae at four levels: below satiation, at about satiation, above satiation and well above satiation. These are represented by the feeding groups F1–F4 and C1–C4, respectively. No mortality was observed throughout the experiment. In groups F2–F4 a considerable incidence of uneaten food (>40% observations), deformities of the caudal penduncle, retarded growth, elevated condition coefficient (>1.2), reduced amounts of minerals in the tissue (<10% dry matter), high C/N ratio (>5) and high caloric value of the tissue (>28 J mg−1 dry matter) (the latter two suggesting excessive fat deposits), were found. The combination of these indices was indicative of overfeeding in fish fed the Futura diet at the daily doses ≥2.7% fish biomass. First symptoms of overfeeding: a considerable incidence of uneaten food, retarded growth, and elevated C/N ratio were observed in the group fed Chironomidae larvae at the highest level, (C4, wet Chironomidae 20.7% of the fish biomass daily, that is, 3.9% of dry chironomids per fish biomass and day). Thus, restricted daily doses of formulated diet not exceeding 2.5% fish biomass are recommended for tench juveniles aged 130–200 days post hatch. Safe daily doses of frozen Chironomidae (in terms of larvae dry weight) remain below 3.5% of fish biomass.  相似文献   

19.
The present work examined the short- and long-term effects of three rearing temperatures on protein metabolism and growth trajectories of Senegalese sole larvae using 14C-labelled Artemia protein as feed. A first feeding trial was performed on larvae reared at 15, 18 and 21 °C (at 26, 17 and 14 days post-hatching (dph), respectively) and a second trial conducted on post-larvae after transfer to the same rearing temperature (~20 °C) (49, 35 and 27 dph, in larvae initially reared at 15, 18 and 21 °C, respectively). Temperature greatly influenced larvae relative growth rate (RGR) and survival, since growth at 15 °C was severely depressed. Protein digestibility and retention was highest at 18 °C during the first trial (85.35 ± 1.16 and 86.34 ± 2.33 %, respectively). However, during the second trial, post-larvae from 15 °C had the highest feed intake and protein digestibility (3.58 ± 1.54 and 75.50 ± 1.35 %, respectively), although retention was similar between treatments. Furthermore, after transfer to 20 °C larvae from 15 °C experienced compensatory growth, which was observed until 121 dph, and confirmed by RGR values, which were significantly higher at 15 ºC than at 21 ºC or 18 ºC. Results from the present study show that Solea senegalensis larval development, survival and protein digestion and retention are highly affected by thermal history.  相似文献   

20.
To develop a feeding strategy for the Australian freshwater fish silver perch (Bidyanus bidyanus Mitchell), a series of eight experiments was done in 1 m3 cages in an aerated, earthen pond to determine the effects of feeding rate (% body weight) and feeding frequency (no. of feeds day?1) on the growth and feed conversion ratio (FCR) of fingerlings and larger fish under ambient water temperatures over the range 13.8–30.6°C. Fish were fed extruded pellets of a silver perch diet containing 34% digestible protein and 14 MJ kg?1 digestible energy. Commercial silver perch farmers were consulted about feeding practices for large fish (>500 g) and at water temperatures below 12°C, and winter feeding practices for other warmwater species were used to complete the strategy. In the feeding experiments, growth and FCR increased with increasing feeding rates to a level above which only FCR increased. Optimal feeding rates and frequencies were those which resulted in maximal growth, while minimizing effort (feeding frequency) and FCR. The highest feeding frequency required for maximal growth, including that of small fingerlings was twice (2 ×) daily, and the optimal feeding rates varied with water temperature and size of fish. The optimal daily regimes were: small fingerlings (initial mean weight, 2.0 g) 7.5% 2 × at a mean temperature of 23.3°C; fingerlings (14.9–27.7 g) 7.5% 2 × at 27.1°C, 5.0% 2 × at 23.7°C and 2.0% 1 × at 16.8°C; and large silver perch (162.5–510.6 g) 0.5% 1 × daily or 1.0% on alternate days at 15.6°C, 1.0% 1 × at 17.3°C, 3.0% 2 × at 24.1°C and 2.0% 2 × at 27.9°C. It is suggested that regimes of 0.5% 1 × daily for fingerlings (<50 g) and 0.5% 1 × on alternate days for larger fish are used at temperatures of 9–12°C, and 0.5% 3 days week?1 and 0.5% 1 day week?1 for fingerlings and larger fish, respectively, at 6–9°C. Feed inputs should not exceed 150 kg ha?1 day?1 in ponds less than 0.3 ha and 100 kg ha?1 day?1 in larger ponds. Our research has established a feeding strategy for silver perch based on restricted rations.  相似文献   

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