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1.
Abstract – Larvae and juveniles of perch Perca fluviatilis and bream Abramis brama of Lake Speldrop, a highly eutrophicated gravel-pit lake in the floodplain of the Lower Rhine, were used in laboratory experiments to study predation of perch on bream. In the first series of experiments (control), 0+ perch of 30 mm total length (TL) did not prey on 0+ roach of about 24 mm TL. The perch fed only on zooplankton, resulting in low growth rates of 0.17 mm  ·  day−1. In the second series of experiments, perch (30 mm TL) were combined with 0+ bream with an average TL of 14 and 19 mm at different ratios. As in the first series, even a nine-fold higher amount of zooplankton food had no significant influence on the growth rate of perch, regardless of the perch:bream ratio. At a perch: bream ratio of 7:1 and 4:4 all bream were eaten by the perch and restocked twice daily. At the end of the experiment, the TL of perch at a perch:bream ratio of 7:1 was significantly lower compared to a perch:bream ratio of 4:4 (mean growth rates at 7:1 of 0.16 mm  ·  day−1 and at 4:4 of 0.35 mm  ·  day−1). At the perch:bream ratio of 1:7, perch fed on bream in varying amounts, averaging between 3 and 12 bream per day and per individual. After 20 days, the final length of these fish was always significantly higher than the TL of perch at other perch:bream ratios and increased in correlation to number of bream eaten per day (mean growth rate 1.13 mm  ·  day−1). The results are discussed with respect to the piscivore-dominated fish community of the eutrophied Lake Speldrop. Note  相似文献   

2.
The effects of several feeding levels (1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% and 4.5% of body weight per day, BW day−1) on the growth, feed efficiency and body composition of juvenile Lutjanus argentimaculatus (body weight 27.1 g) were examined. Fish were fed a test diet (40% protein, 18.4% lipid and 13.4 kJ g−1) for 75 days in three equal meals. Weight gain and specific growth rate increased with increasing feeding level up to 2.5% BW day−1, after which no significant improvement in growth was observed. The feed efficiency, protein efficiency ratio, retention of protein and digestibility of nutrients did not differ for fish fed 1–2.5% BW day−1, but decreased significantly when feeding levels were increased above 3% BW day−1. The chemical compositions of whole fish or body organs were significantly affected by the feeding level. The condition factor, mesenteric fat, hepato- and viscerosomatic indices were higher in fish fed 2.5–4.5% BW day−1. The cholesterol, triglycerides and haematocrit values were similar among treatments, except that high levels of plasma lipids were recorded in fish fed at 2.5% BW day−1. Taking into consideration the growth, feed efficiency and body composition data attained in this study, a feeding level of 2.5% BW day−1 is recommended for juvenile L. argentimaculatus weighing between 27 and 140 g.  相似文献   

3.
Abstract –  Tilapia species in East African lakes often form the basis of commercial fisheries, with information on their population biology assisting their management. This study utilised otolith microstructure, with validation by modal progression analysis, to provide growth data for two tilapia species in two Kenyan lakes for the first time. Otolith microstructure revealed the growth rate of Oreochromis niloticus baringoensis , a sub-species endemic to Lake Baringo, was fast compared with populations of Oreochromis niloticus ; mean daily growth rates were >0.50 mm·d−1 in fish between 12 and 53 mm total length. Growth of Oreochromis leucostictus in Lake Naivasha was also relatively fast when compared with the growth rates of other tilapia species, with mean daily growth rates of approximately 0.35–0.48 mm·d−1 in fish between 10 and 56 mm total length. Growth rates of both species were well described by the Gompertz model and were corroborated by modal progression analysis that revealed similar daily growth rates in modes of young-of-the-year fish.  相似文献   

4.
Abstract –  Differences in growth and allocation of energy of young-of-the-year (YOY) perch ( Perca fluviatilis ) were studied in relation to both quantity and quality of food. Feeding on fish and Mysidacea, the mean size of YOY perch after the first growing season in Lake Pfeiffer was 152 mm. In contrast, YOY perch grew to 107 mm in Lake Speldrop and 83 mm in Lake Reeser Meer while mainly feeding on zooplankton. In correlation with food uptake and growth, the lipid content of YOY perch was significantly highest in Lake Pfeiffer and lowest in Lake Reeser Meer, assuming that YOY perch from Lake Pfeiffer should be able to survive starvation periods during their first winter better then those from Lake Speldrop and Lake Reeser. While feeding on fish, mean highest growth rates were 1.31 mm·day−1 in the laboratory. Growth in weight started when food uptake exceeded 66 J·g WW−1·day−1, while an increase of lipid content required food input of 175 J·g WW−1·day−1. Increased growth potential associated with the availability of energetically profitable food is assumed as an important factor that could have far-reaching consequences for the fish community.  相似文献   

5.
This investigation examined the effect of prey condition on the growth and survival of juvenile cuttlefish ( Sepia officinalis ). In the first group, cuttlefish were fed with daily captured live Palaeomonetes varians from the wild [daily prey (DP)], the second group was fed 5 days stocked and starved P. varians [starved prey (SP)], while in the third group, cuttlefish were fed 8 days stocked P. varians fed with an artificial diet [fed prey (FP)]. Mean instantaneous growth rate (IGR) was 2.8±1% body weight day−1 (bw day−1), 3.3±1.1% bw day−1 and 4.9±0.5% bw day−1 for SP, DP and FP respectively. At the end of the experiment, final weight gain ( W g) was 121±21.6%, 153.8±17.3% and 295±29.8% for SP, DP and FP respectively. No significant differences were found ( P >0.05) between growth curves for every group tested, or for the food conversions between those same groups ( P >0.05), but statistical differences ( P <0.05) were found in IGR between DP vs. FP and SP vs. FP. Mortality was 2 and 1 for SP and DP respectively. Results indicate that prey starvation should not be considered when feeding juvenile cuttlefish, as prey can only be stocked if proper artificial diets are provided, to obtain optimal growth.  相似文献   

6.
Abstract— Herbivorous tilapia fish, Oreochrornis niloticus L. (Cichlidae), collected from five Ethiopian lakes were analyzed for lipid and fatty acid contents of the dorsal muscle using spectrophotometry and gas-liquid chromatography. The results showed remarkable variation between the lakes in both the lipid and total fatty acid content of the fish, 1.7–21 and 1.6–9.3% of dry weight (DW), respectively. Most fish from Lakes Haiq and Chamo contained higher levels of fat (≥ 10% DW) compared to fish from Lakes Ziway, Langeno and Awassa which contained ≤ 5% DW fat. A total of 28 fatty acids were identified. The saturated fatty acids ranged from 5.3–30 mg. gg−1 DW, monounsaturated Fatty acids from 1.3–30 and polyunsaturated fatty acids from 6.8–29 mg. g−1 DW. The most abundant fatty acids were palmitic acid, docosahexaenoic acid (DHA), oleic acid, stearic acid, palmitoleic acid, arachidonic acid and eicosapentaenoic acid (EPA). EPA and DHA alone amounted to 2.6–15 mg. g−1 DW. The ω3/ω6 ratios ranged from 1.3–7.6 and L. Haiq fish showed the highest ratios, 5.1–7.6, indicating that the fat was of high nutritional quality. The reason for such variation is probably the varied diet available to the fish in the various lakes, This study, along with previous reports, confirms that the phytoplankton flora constituting the diet of O. niloticus varies greatly between the study lakes. The variation in phytoplankton is also reflected by the fatty acid pattern of net samples taken from the study lakes.  相似文献   

7.
A 6-week growth rate trial of 6.7 mm ± 1.35 SD long blacklip abalone ( Haliotis rubra ) fed one of four graded protein feeds (26%, 32%, 37%, 45% crude protein, CP) resulted in a maximum average growth rate of 81 μm day−1 (percentage daily weight gain of 5.2% day−1) with the 45% CP diet. Based on the results, a new, simple, non-destructive method to calculate the relative utilization efficiencies (RUE) of nutrients is presented to estimate the relative contributions of a nutrient to growth, body maintenance and the excess used for energy. Calculations of RUE of protein estimated that at the maximum growth rate, 59% of the CP was responsible for growth, while 31% was used for body maintenance and an excess of 10% was lost and presumably catabolized for energy and carbohydrate anabolism. At the %CP where the highest proportion of CP was used for growth, i.e. the maximum RUE of protein for growth (slightly higher at 62%), 35% was used for body maintenance and only 3% of the excess was lost to energy.  相似文献   

8.
Juvenile Haliotis rufescens were reared in the laboratory in order to investigate the extent to which fresh kelp and formulated feeds with 250 g kg−1 (25P) and 380 g kg−1 protein content (38P) affected their growth rate, gut residence time (GRT), food consumption ( C ), food conversion ratio (FCR) and digestibility. Abalone from 38P attained the highest growth rate (70.5 ± 4.2 μm day−1; 98.3 ± 6.95 μg day−1), followed by 25P (47.9 ± 2.79 μm day−1; 67.4 ± 2.82 μg day−1) and kelp (23.6 ± 3.36 μm day−1; 28.2 ± 4.11 μg day−1). No significant differences were observed in consumption rate among treatments (0.61–0.68% body weight per day), yet kelp-fed abalone exhibited higher FCR (2.44), protein efficiency ratio (4.42), and apparent digestibility of dry matter (69.5%), protein (69.8%) and gross energy (79.2%) than 38P organisms (59.8, 62.4 and 62.2%, respectively). They also showed longer GRT (23.1 ± 0.93 h). This study demonstrated that formulated diets with 250 g kg−1 and 380 g kg−1 protein inclusion can sustain higher growth rates of juvenile H. rufescens than fresh algae. These differences seem to be due to the amount of dietary protein. Kelp meal appears to improve the consumption and digestibility of balanced diets, and its inclusion in formulated diets is recommended.  相似文献   

9.
Factorial determinations of energy and protein requirements in growing Sparus aurata were carried out at 23–24°C. The energy content in the whole fish was dependent on fish weight and ranged from 5 to 11 MJ kg−1 body mass for 1–250 g fish, whereas the protein content remained constant at 179 g kg−1.
During starvation the fish lost 42.5 kJ body weight (BW) (kg)−0.83 day−1 and 0.42 g protein BW (kg)−0.70 day−1. The maintenance requirement for energy was calculated to be 55.8 kJ BW (kg)−0.83 day−1 and for protein 0.86 g BW (kg)−0.70 day−1. Utilization of digestible energy and digestible crude protein below and at maintenance was determined as 0.72 and 0.51, respectively. Utilization of digestible energy and digestible crude protein for growth above maintenance was determined as 0.46 and 0.28, respectively.
These values allow estimation of requirements for growing Sparus aurata .  相似文献   

10.
An on-farm trial was carried out from February to June 2006 to evaluate the growth and production performance of catla ( Catla catla ) and tilapia ( Oreochromis niloticus ) with freshwater prawn ( Macrobrachium rosenbergii ) and mola ( Amblypharyngodon mola ) in farmer's rice fields. In all treatments, 20 000 mola ha−1 and 20 000 prawn ha−1 were stocked. Besides, stocking included 2500 catla ha−1 in treatment-I, 2500 tilapia ha−1 in treatment-II and catla and tilapia at 1250 ha−1 each in treatment-III . Prawns were fed in the evening with pellets at a feeding rate of 3–8% body weight (initially 8% and gradually decreased to 3%). Catla and tilapia were fed in the morning with a paste of mustard oil cake and rice bran at a feeding rate of 3% body weight. Significantly higher combined production of fish and prawn observed was 2142 kg ha−1 in treatment-I. The benefit:cost ratio was found to be significantly higher in treatment-I than in treatment-II and there were no differences between treatments I and III. From the production and economic point of view, treatment-I was found to be the best proposition for the rotational rice–fish culture systems.  相似文献   

11.
Two feeding experiments were conducted to re-evaluate the total sulphur amino acid (TSAA; methionine and cystine) requirement and determine the replacement value of cystine for methionine of juvenile Nile tilapia ( Oreochromis niloticus ). Semi-purified diets used in both experiments contained 3510 kcal gross energy and 280 g of protein per kilogram diet from casein, gelatin and crystalline amino acids. The basal diet of the first experiment contained 3.1 g methionine and 0.4 g cystine per kilogram. l -methionine was added to the seven remaining diets at 1.0 g kg−1 increment to produce methionine levels ranging from 3.1 to 10.1 g kg−1 diet. Each diet was fed to four replicate groups of juvenile Nile tilapia (1.28 g mean weight) in a recirculation system for 8 weeks. Broken-line regression analysis of weight gain data indicated that the TSAA requirement of juvenile Nile tilapia was 8.5 g kg−1 of the diet or 30.4 g kg−1 of dietary protein. In the second experiment, TSAA level was set at 95% of the requirement value determined in the first experiment. Seven diets were made with different ratios of l -methionine and l -cystine (20 : 80, 30 : 70, 40 : 60, 50 : 50, 60 : 40, 70 : 30 and 80 : 20, based on an equimolar sulphur basis). Each diet was also fed to four replicate groups of juvenile Nile tilapia (4.14 g mean weight) in a recirculation system for 8 weeks. Regression analysis of weight gain data using broken-line model indicated that cystine (on a molar sulphur basis) could replace up to 49% of methionine requirement in semi-purified diets for juvenile Nile tilapia.  相似文献   

12.
This study examined the effect of potential probiotic bacteria on growth and survival of the tilapia Oreochromis niloticus , under high density and suboptimum temperature. Presumptive Bacillus and lactic acid bacteria (LAB) were isolated from tilapia and from their culture system and were characterized for haemolytic and enzymatic activity, and antagonism against Vibrio . Selected strains were included in the diet of juvenile tilapia and evaluated during a 134-day assay. The experiment was conducted with four treatments: (1) fish fed with commercial feed plus Dry Oil®; (2) fish fed with commercial feed plus LAB; (3) fish with bacilli in water; (4) fish with a mixture of treatments 2 and 3. Tilapias in all treatments, including bacteria, grew significantly better than fish fed with commercial feed plus Dry Oil® (control group). Survival was similar in all treatments. The physicochemical parameters of the culture system were maintained within the optimal ranges for the species, with the exception of temperature (19.9–24.82 °C). Animals fed diet supplemented with bacilli and LAB had good survival and the best growth performance, suggesting that bacteria are appropriate growth-stimulating additives in tilapia cultivation.  相似文献   

13.
The feasibility of obtaining a similar growth response from juvenile pink abalone Haliotis corrugata at a research laboratory and a hatchery, when using natural feeds was evaluated. Four macroalgae, Egregia menziesii , Eisenia arborea , Macrocystis pyrifera , Gracilaria sp., and the surfgrass Phyllospadix torreyi were used as feeds. Response patterns of abalone were very similar at both facilities in terms of final length, weight, and survival, varying from 13.0 to 15.50 mm, 0.31 to 0.52 g, and 60.0% to 78.6%, respectively. Better growth was obtained when E. menziesii , M. pyrifera , and Gracilaria sp. were offered. Poor results were obtained with surfgrass. The feed conversion ratio was determined at the laboratory and did not vary significantly, ranging from 42.3 to 199.0; although a significant inverse correlation was observed with growth rate. Growth in length and weight and survival rates varied within 1.6–20.2 μm day−1, 0.123–1.664 mgday−1, 0.4–0.64%day−1, respectively. Mean growth rate in length (14.7μm day−1) and weight (1.18 mg day−1) at the hatchery were significantly higher than that obtained at the laboratory (9.4 μm day−1 and 0.77 mg day−1), which is most likely a consequence of more suitable water temperature at the hatchery. Mean survival rate was significantly higher at the laboratory (53.1%day−1) than at the hatchery (46.1%day−1).  相似文献   

14.
During winter months, a novel overwintering mode of transferring juvenile abalones to open seawaters in southern China rather than keeping them in closed land-based nursery systems in northern China is a popular practice. The initial size, stocking density and sorting are among the first considerations when establishing an abalone culture system. This study aimed to investigate the effects of these factors on the growth of juvenile Pacific abalone, Haliotis discus hannai Ino, during overwintering. Juvenile abalones were reared in multi-tier basket form for overwintering in open seawaters in southern China for 106 days. The daily growth rates (DGRs) in the shell length of all experimental groups ranged from 67.08 to 135.75 μm day−1, while the specific growth rates (SGRs) were 0.2447–0.3259% day−1. Variance analysis indicated that both DGRs and SGRs in shell length were significantly affected by the initial body size and stocking density. Furthermore, the effects of stocking density on DGRs and SGRs varied with the initial size. However, sorting abalones according to their initial sizes may not be necessary in practice as sorting did not alter growth significantly at all densities in this study. Factors potentially affecting abalone growth such as genetic control and intraspecific competition were discussed.  相似文献   

15.
Ethoxyquin (EQ) has been used as an antioxidant in livestock, aquaculture and pet foods. Animal food safety law has established the upper limit of EQ in animal feed at 150 mg kg−1. However, the risk of EQ at the approved level for aquaculture feed (150 mg kg−1) to fish health is unknown. Here, we examine the effect of EQ on the immunity of tilapia ( Oreochromis niloticus ). EQ concentration in the blood reached 0.16 mg L−1 in fish fed EQ at the approved level. This level of EQ inhibited phagocytic activity of leucocytes in vitro and antibacterial activity of whole blood in vivo . Furthermore, pyknosis in the liver was observed throughout the duration of feeding. However, after 30 days of experimental challenge with feed containing 150 mg kg−1 of EQ, no significant difference was observed in mortality. Although EQ at the approved level in feed causes immunosuppression in fish, the severity of immunosuppression does not lead to a lowering of disease resistance for short feeding periods.  相似文献   

16.
Hamre  Næss  Espe  Holm  & Lie 《Aquaculture Nutrition》2001,7(2):123-132
A diet for Atlantic halibut-larvae was formulated taking into account the fact that marine-fish larvae have a limited ability to assimilate protein and lipid. Dietary protein consisted of a free amino-acid premix (7.2% of crude protein), predigested-squid mantle (7.2%), squid mantle (8.6%) and cod-muscle mince (77.0%). Lipid sources were soyabean lecithin (33% of crude lipids), crude phospholipids extracted from cod roe (10%) and sardine oil (57%). Larvae were weaned onto the experimental diet at wet-body weights of 0.07, 0.10 or 0.16 g, respectively. The experimental diet was fed for 31, 25 or 17 days, respectively, and the experiment was terminated on the same calendar day for all groups. A control group was fed with Artemia nauplii enriched with DHA Selco™ from 0.07 g. Survivals ranged from 78% in larvae transferred at 0.10 g to 96% in those transferred at 0.16 g and in the control group. Daily specific-growth rates (SGR) were 3.1 ± 0.07, 3.3 ± 0.11 and 2.2 ± 0.01% day−1 in larvae transferred at 0.07, 0.10 and 0.16 g, respectively, while growth in the control group was 5.1% day−1. It was concluded that weaning of Atlantic-halibut larvae is feasible from 0.7 g (approximately 20 days post first-feeding) when the formulated diet contains predigested protein and ample amounts of phospholipids.  相似文献   

17.
The effects of temperature on growth, food-conversion ratio (FCR) and feeding intensity of juvenile dusky kob Argyrosomus japonicus (23.7±2.6 g fish−1) were assessed over the temperature range 17.5–28.5 °C in a 42-day growth trial. Growth increased with increasing temperature up to an optimum after which it declined. Specific growth rates were 2.05% and 1.2% day−1 for the fastest (25.3 °C) and the slowest (17.5 °C) treatments respectively. Food-conversion ratio peaked at a lower temperature than growth. Optimal (0.72 kg kg gain−1) and least efficient (1.40 kg kg gain−1) FCR were found at 21.7 and 17.5 °C respectively. Feeding intensity was linearly related to temperature within the range of 17.5–28.5 °C. These results corresponded to the thermal preference (25–26.4 °C) and natural temperature distribution (12–28 °C) of South African dusky kob. Determination of the temperature range that does not limit growth is a prerequisite to assess the relationship between growth and environmental variables such as light intensity, feeding regime and stocking density. Consequently, experiments to determine the effects of these environmental variables on growth and aquaculture potential of dusky kob should be conducted at 24–26 °C.  相似文献   

18.
Lactococcus garvieae infection in cultured Nile tilapia, Oreochromis niloticus (L.), and pintado, Pseudoplathystoma corruscans (Spix & Agassiz), from Brazil is reported. The commercial bacterial identification system, Biolog Microlog®, confirmed the identity of L. garvieae . Infectivity trials conducted in Nile tilapia using Brazilian Nile tilapia L. garvieae isolates resulted in a median lethal dose-50 of 1.4 × 105 colony-forming units (CFU)/fish. This is the first evidence of the presence of this pathogen from Brazilian fish. In addition, this is the first report of L. garvieae infection in either Nile tilapia or pintado. Collectively, this evidence expands the geographical range of fish hosts, number of fish hosts harbouring L. garvieae and carbon source utilization by L. garvieae fish isolates. Furthermore, the Biolog system may be an alternative technique to polymerase chain reaction for the identification of L. garvieae and discrimination between closely related bacterial species.  相似文献   

19.
Abstract –  The African big barb ( Barbus intermedius , R.) from Lake Awassa, Ethiopia is an important fish species, especially with the ongoing decline of the Nile tilapia ( Oreochromis niloticus , L.) fishery. Their diet and habitat use was studied using stomach content analyses, stable nitrogen and carbon isotopes, and transect netting. Mercury biomagnification was also determined. The big barb was found to primarily exist in the littoral habitat, with molluscs being their predominant food item. The proportion of small fish ( Barbus paludinosus , P.) in the big barb diet tended to vary somewhat with size, with the largest fish tending to have the most piscivorous diet. Mercury concentrations in the big barb ranged from 0.01 to 0.94 mg·kg−1, and were positively related with size. Fish transects and stable isotope analyses suggest that there may be two feeding forms of big barb in Lake Awassa, with some larger fish preying upon fish (and accumulating higher mercury concentrations). With the declining Nile tilapia fishery in Lake Awassa, the implication of fishermen focusing on large big barb, with its associated higher Hg burdens, is significant with human health ramifications.  相似文献   

20.
Abstract. Two grow-out experiments were conducted to evaluate the functional role of chicken manure for Nile tilapia, Oreochromis niloticus (L.). production in central Thailand. Experiment 1 examined the relationship between chicken manure input and net fish yield (NFY). Experiment 2 determined the value of chicken manure in providing tilapia particulate organic carbon, and/or dissolved inorganic carbon (DIC) for stimulating algal productivity. In both experiments supplemental urea and triple superphosphate (TSP) gave all treatments total nitrogen (N) and phosphorus (P) inputs of 28·0kg/ha/week and 7·0kg/ha/week, respectively.
Addition of chicken manure to inorganic fertilization did not enhance production of Nile tilapia. NFY in experiment 1 increased with decreasing manure loading, which corresponded to increasing TSP input. Regression analysis suggested that chicken manure-P was about 10% effective as TSP-P at increasing NFY. NFY was linearly correlated to net primary productivity (r2= 0·62, P < 0·001), which was linearly correlated to total alkalinity (r2= 0·77. P < 0·001).Treatment differences in alkalinity, community respiration or dissolved oxygen concentrations at dawn were not related to manure input. Simple economic comparisons discourage the purchase of chicken manure as a source of soluble N and P for increasing algal productivity in Thailand.  相似文献   

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