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1.
The combined effects of temperature and salinity on larval survival and development of the mud crab, Scylla serrata, were investigated in the laboratory. Newly hatched larvae were reared under 20 °C temperature and salinity combinations (i.e. combinations of four temperatures 25, 28, 31, 34 °C with five salinities 15, 20, 25, 30, 35 g L−1). The results showed that temperature and salinity as well as the interaction of the two parameters significantly affected the survival of zoeal larvae. Salinity at 15 g L−1 resulted in no larval survival to the first crab stage, suggesting that the lower salinity tolerance limit for mud crab larvae lies somewhere between salinity 15 and 20 g L−1. However, within the salinity range of 20–35 g L−1, no significant effects on survival of zoeal larvae were detected (P>0.05). The combined effects of temperature and salinity on larval survival were also evident as at low salinities, both high and low temperature led to mass mortality of newly hatched larvae (e.g. 34 °C/15 g L−1, 34 °C/20 g L−1 and 25 °C/15 g L−1 combinations). In contrast, the low temperature and high salinity combination of 25 °C/35 g L−1 resulted in one of the highest survival to the megalopal stage. It was also shown that at optimal 28 °C, larvae could withstand broader salinity conditions. Temperature, salinity and their interaction also significantly affected larval development. At 34 °C, the mean larval development time to megalopa under different salinity conditions ranged from 13.5 to 18.5 days. It increased to between 20.6 and 22.6 days at 25 °C. The effects of salinity on larval development were demonstrated by the fact that for all the temperatures tested, the fastest mean development to megalopa was always recorded at the salinity of 25 g L−1. However, a different trend of salinity effects was shown for megalopae as their duration consistently increased with an increase in salinity from 20 to 35 g L−1. In summary, S. serrata larvae tolerate a broad range of salinity and temperature conditions. Rearing temperature 25–30 °C and salinity 20–35 g L−1 generally result in reasonable survival. However, from an aquaculture point of view, a higher temperature range of 28–30 °C and a salinity range of 20–30 g L−1 are recommended as it shortens the culture cycle.  相似文献   

2.
Succession of phytoplankton dominance was studied in shrimp culture ponds treated with commercial bacterial products. Diatoms were dominant and the cyanobacteria were absent in both treated and control ponds at the beginning of the culture period. After 34 days, the diatoms significantly decreased whereas cyanobacteria increased in both ponds. Chlorophyll a increased from a mean of 35.56 mg m?3 in the first phase to 186.00 mg m?3 in the final phase, and from 42.12 mg m?3 to 242.81 mg m?3 in the treated and control ponds respectively. Cyanobacteria were significantly higher in the control compared with the treated ponds during the final phase of the culture. Algal bioassay showed that the addition of nitrogen either alone or with silica to pond water significantly increased the specific growth rate of Chaetoceros calcitrans. The specific growth rate of Oscillatoria sp. significantly increased when a combination of nitrogen, phosphorus and carbon was added to the pond water. Addition of silica seemed to depress the growth rate of Oscillatoria sp. Nutrient enrichment should be minimized and the supply of nitrogen and silica should be adequate for promoting the growth of beneficial phytoplankton in aquaculture systems.  相似文献   

3.
We determined the effects of 16 wk of storage at low temperature (4 C) in darkness on the viability, growth, photosynthetic parameters, and biochemical composition of four diatom cultures. Significant differences in cell density and proximal composition were observed for all diatoms throughout storage. Cell density increased with time of storage for all diatoms. Protein content increased for Navicula incerta, Nitzschia laevis, and Navicula sp., whereas lipid content increased during storage in only N. incerta. When the stored diatoms were used as inocula in fresh medium, they increased their viability, generating a lag phase for Nitzschia thermalis var. minor, N. incerta, and Navicula sp. cultures. There were noted species‐specific modifications in proximal composition, ash‐free dry weight, and photosynthetic parameters in response to storage. We conclude that N. thermalis, N. incerta, N. laevis, and Navicula sp. can be stored at 4 C for 16 wk and are viable in new cultures.  相似文献   

4.
Due to lack of information on the use of non‐protein energy sources in diets for pacu (Piaractus mesopotamicus), a 2 × 2 × 3 factorial experiment was conducted to evaluate the performance and digestibility of 12 diets containing approximately two crude protein (CP; 220 and 250 g kg−1), two lipid (40 and 80 g kg−1) and three carbohydrate levels (410, 460 and 500 g kg−1). The pacu juveniles‐fed diets containing 220 g kg−1 CP did not respond (P > 0.05) to increased dietary lipid and carbohydrate levels, but the fish‐fed diets containing 250 g kg−1 CP showed a better feed conversion ratio. There were interactions in weight gain (WG), specific growth rate (SGR), crude protein intake (CPI) and feed conversion rate (FCR) dependent on dietary carbohydrate and lipid levels, showing positive effects of increasing carbohydrate levels only for fish‐fed diets containing 80 g kg−1 lipid level. However, when the diets contained 40 g kg−1 lipid, the best energy productive value (EPV) results were obtained at 460 g kg−1 carbohydrate. A higher usage of lipids (80 g kg−1) reduced CPI and was detrimental to protein [apparent digestibility coefficient (ADC)CP] and energy (ADCGE), but did not affect growth. The ADCGE improved proportionally as dietary carbohydrate levels increased (P < 0.05), increasing the concentration of digestible energy. In addition, the WG, CPI, ADCGE results showed best use of the energy from carbohydrates when dietary protein level was 250 g kg−1 CP. The utilization of 250 g kg−1 CP in feeds for juvenile pacu for optimal growth is suggested. Therefore, the optimum dietary lipid and carbohydrate levels depend on their combinations. It can be stated that pacu uses carbohydrates as effectively as lipids in the maximization of protein usage, as long as it is not lower than 250 g kg−1 CP or approximately 230 g kg−1 digestible protein.  相似文献   

5.
The aim of this study was to evaluate the effect of the addition of Chaetoceros calcitrans, Navicula sp. and Phaeodactylum tricornutum (diatoms) on phytoplankton composition and the growth of Litopenaeus vannamei postlarvae reared in a biofloc system . Four treatments were used: BFT (biofloc system without feed and no addition of diatoms); BFT‐F (biofloc system with feed and no addition of diatoms); BFT‐D (biofloc system with the addition of diatoms and no feed); and BFT‐FD (biofloc system with the addition of feed and diatoms), all in triplicate. The shrimp (16 ± 0.02 mg) were stocked at 2500 postlarvae m?3 and fed a commercial feed. Diatoms were added on the 1st, 5th, 10th and 15th day at a density of 5 × 104 cells mL?1 for each species. No significant differences (P > 0.05) between treatments were observed for gross primary production, net ecosystem production and water column respiration rate. However, significant differences (P < 0.05) were observed for nitrite, orthophosphate, alkalinity, final weight, weight gain, yield, feed conversion ratio (FCR), phytoplankton and cyanobacteria composition. The BFT‐FD treatment had better performance parameters for final weight (270 mg), weight gain (254 mg), yield (0.67 Kg m?3) and FCR (0.61), indicating the benefits of the diatoms C. calcitrans, Navicula sp. and P. tricornutum for decreasing cyanobacteria and improving growth of L. vannamei postlarvae reared in biofloc systems.  相似文献   

6.
Cyanophytes are the most ancient photosynthetic organisms. During its evolution, they have developed various ecophysiological adaptation strategies to survive in extreme conditions. The environment prevailing under biofloc cultures provides various conditions appropriate for cyanobacterial proliferation. An outdoor experiment (7 weeks) was performed with a simple random design consisting of four inoculation levels (by triplicate) of Oscillatoria sp. (0.0, 0.1, 0.5 and 1 mg L?1) in saltwater biofloc. The objective was to evaluate the effect of the cyanobacteria inoculation on water quality and tilapia production parameters. The results indicated that the amount of Oscillatoria sp. inoculated significantly affected water quality (pH, chlorophyll a, TSS and NO3‐N) and tilapia parameters (final weight, feed conversion ratio, specific growth rate and survival). No significant effects on dissolved oxygen, total ammonia nitrogen (TAN) or NO2‐N were observed. We recommend identifying the cyanobacteria species that are able to grow in a biofloc system and their possible adverse effects on the system.  相似文献   

7.
A feeding trial of three protein (200, 300 and 400 g kg−1) and two lipid levels (20 and 100 g kg−1) was conducted to determine the proper dietary protein and lipid levels for growth of juvenile sea cucumber Apostichopus japonicus. Dietary protein and lipid levels were adjusted by adding with different levels of soybean meal, squid liver oil and soybean oil, respectively. Three replicate groups of sea cucumbers (average weight of 1.3 g) were fed the experimental diets for 12 weeks. At the end of the feeding trial, survival was not affected by dietary protein and lipid levels (P > 0.05). Weight gain (WG) and specific growth rate (SGR) of sea cucumbers were significantly affected by dietary protein (P < 0.006) and lipid levels (P < 0.001). The highest WG and SGR were observed in sea cucumbers fed the 200 and 400 g kg−1 protein diet with 20 g kg−1 lipid (P < 0.05). WG and SGR of sea cucumbers fed the diet containing 20 g kg−1 lipid were higher than those of sea cucumbers fed the 100 g kg−1 lipid diets (P < 0.05) at each dietary protein level. Apparent digestibility coefficients of dry matter, crude protein, carbohydrate and gross energy of sea cucumbers fed the 20 g kg−1 lipid diets were significantly higher than those of the 100 g kg−1 lipid diets at 200 and 400 g kg−1 protein (P < 0.05). Moisture, crude protein, crude lipid and ash contents were not significantly different among the groups. The results of this study indicate that the diet containing 200 g kg−1 protein (170 g kg−1 digestible protein) with 20 g kg−1 lipid (13 g kg−1 digestible lipid) may be sufficient for optimum growth of juvenile sea cucumber.  相似文献   

8.
To verify the potential of lipids and carbohydrates to spare dietary protein and to understand the intermediary metabolism of interaction of these nutrients in pacu juveniles, an experiment was carried out to evaluate pacu physiological and performance parameters. The experimental design was completely randomized with 12 treatments in a 2 × 2 × 3 factorial arrangement, consisting of diets containing two digestible protein levels (200 and 230 g kg−1 PD), two lipid levels (40 and 80 g kg−1) and three carbohydrate levels (410, 460 and 500 g kg−1). Fish‐fed 230 g kg−1 digestable protein (DP) showed increased glycaemia, decreased hepatic glycogen, as well as a smaller intake index and better feed conversion ratio. The higher dietary lipid level (80 g kg−1) reduced protein intake and serum protein concentration, increased liver and body fat content, but did not affect growth. At a lipid level of 80 g kg−1, the increase in dietary carbohydrate levels promoted greater weight gain (WG), crude protein intake (CPI) and better feed conversion ratio (FCR). For fish fed diets containing 40 g kg−1 lipid, the best energy‐productive values (EPV) were obtained at 460 g kg−1 carbohydrate. Increased levels of the main nutrients in the diets reduced the levels of serum triglycerides, while the increase in energy concentration increased the hepatosomatic (HSI) and glycaemia index values. Pacu used lipids as effectively as carbohydrates in the maximization of protein usage, as long as dietary protein was at a level of 230 g kg−1 DP. The physiological parameters indicated that the best balance between the DP, dietary lipid and carbohydrate levels within the ranged this trial was obtained at 230, 40 and 460 g kg−1, respectively, without lower growth.  相似文献   

9.
Cultures of six benthic diatoms were maintained in the dark to measure their viability and biochemical composition after 8 wk of storage at low temperature (4 C) in darkness by refrigeration. Cell density, growth rate, and viability for each benthic diatom changed significantly after storage. Significant differences were observed with regard to cell size (length and width) of Nitzschia laevis, Navicula sp., and Amphora tenerrima as a result of storage. In general, the proximal composition of the benthic diatom cultures changed after week 1 of storage and decreased after week 4 of storage for all the diatoms. These results demonstrate that under 1–4 wk of storage these diatoms maintain their viability and had changes in their proximal composition in species‐specific responses. Storage of preserved live microalgae cells is an alternative technique that can be used to reduce the need for continuous maintenance of live cultures and can provide live feed stock for aquaculture applications.  相似文献   

10.
The effects of salinity on haemolymph osmolality, oxygen consumption and ammonia excretion were investigated in adult kuruma shrimp, Marsupenaeus japonicus (Bate), at salinities of 20, 25, 30 and 35 g L?1. Haemolymph osmolality showed a positive linear relationship (r2=0.9854) with medium osmolality. The isosmotic point calculated from this relationship was 1039 mOsm kg?1, which corresponds to a salinity of approximately 35 g L?1. The slope of the regression equation was very high (0.81), suggesting that M. japonicus adults are poor osmoregulators compared with the adults of other penaeids and to conspecific young. The difference between haemolymph and medium osmolality (DOP) was lowest at 35 g L?1 and highest at 20 g L?1. Thus, the minimum DOP coincided with the isosmotic point of the shrimp. The respiration rate was significantly lower at 30 g L?1 than at the other salinities. Ammonia excretion rates were inversely related with salinity and therefore were minimal at 35 g L?1. The results of this study suggest that the optimum salinity for adult kuruma shrimp is around 30–35 g L?1 and that even minor (e.g. 5 g L?1) deviations from this optimum cause significant physiological changes. Further, the observed increases in oxygen consumption and ammonia excretion during exposure to low salinities, which indicate higher energy expenditure and amino acid catabolism for osmoregulation, respectively, suggest that the growth efficiency of M. japonicus adults may be severely compromised by hypohaline water inflow into the rearing ponds.  相似文献   

11.
Litopenaeus vannamei (Boone) grown in ponds are exposed to salinities of less than 5 g L?1 during inland shrimp culture or to more than 40 g L?1 from evaporation and reduced water exchange in dry, hot climates. However, dietary requirements for shrimp grown in low or high salinities are not well defined, particularly for fatty acids. Feeding shrimp postlarvae with highly unsaturated fatty acids (HUFA) enhances tolerance to acute exposure to low salinity, as a result of better nutritional status, or/and specific effects of HUFA on membrane function and osmoregulation mechanisms. This study analysed the effect of HUFA supplementation (3% vs. 34%) on L. vannamei juveniles reared for 21 days at low (5 g L?1), medium (30 g L?1) and high salinities (50 g L?1). Juveniles grown at 5 g L?1 had lower survival compared with controls (30 g L?1) or shrimp grown at 50 g L?1, but no significant effect on survival was observed as a result of HUFA enrichment. In contrast, growth was significantly lower for shrimp grown at 50 g L?1, but this effect was compensated by the HUFA‐enriched diet. Osmotic pressure in haemolymph was affected by salinity, but not by HUFA enrichment. Shrimp fed HUFA‐enriched diets had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in hepatopancreas and gills. These results demonstrate that growth at high salinities is enhanced with diets containing high HUFA levels, but that HUFA‐enriched diets have no effect on shrimp reared at low salinities.  相似文献   

12.
Juvenile New Zealand turbot, Colistium nudipinnis (Waite 1910), produced during the first aquaculture development project for this endemic flatfish, were reared at ambient and reduced salinities to determine the effect of salinity on growth and survival and the possible implications for aquaculture. Juveniles aged from 176 days to 17 months showed a high level of salinity tolerance, with minimal mortality attributable to salinity reduction over the range 33–18 g L?1. Growth rate was slightly increased at the slightly reduced salinity of 28 g L?1 (5 g L?1 below ambient) but was significantly decreased at the markedly reduced salinity of 18 g L?1. The growth response at 23 g L?1 was markedly different between ‘new’ water and water that was recycled from a previous set of rearing tanks, with juveniles reared in 23 g L?1‘new’ having a mean growth rate that was 29% lower than that of the control juveniles (in 33 g L?1‘new’ water), whereas juveniles in 23 g L?1‘reused’ water grew 45% faster than the controls. The implications of this novel effect are discussed in relation to the aquaculture potential of the New Zealand turbot.  相似文献   

13.
The brown shrimp, Farfantepenaeus californiensis (Holmes), is a species native to north‐west Mexico, where its culture potential is presently being addressed. Because of the climatic conditions prevailing in the region, salinities over 40 g L?1 is a commonly encountered problem. In the present study, the effect of salinity on the growth and mortality of juvenile F. californiensis is described. The change in short‐term routine metabolism at different salinities was also evaluated in order to define the adaptive capacity of the shrimp and to provide insight into the changes in the pathways of energy distribution. Groups of shrimp were exposed to increasing salinity (25, 35, 45 and 55 g L?1), and growth and survival rates after 75 days were determined in duplicate 1.8‐m3 tanks for each salinity level. Significant differences were found in final weight, growth rate and mortality of shrimp as a result of salinity level. Final mean shrimp weights at increasing salinity levels were 10.0, 9.4, 8.6 and 7.8 g. Corresponding mortality was 24.4%, 15.1%, 33.6% and 55.7%. Oxygen consumption was found to depend significantly on salinity and was equivalent to 0.0027, 0.0037, 0.0043 and 0.0053 mg g?1 min?1 respectively for the increasing salinities. The increased rate of oxygen consumption at high salinities reflects the response of the organism to osmoregulatory and ionic imbalances. Increased energy requirements to fulfil basic metabolic function as salinity increased resulted in a reduction in the energy that could be diverted to growth. Consequently, the culture of the brown shrimp at salinities over 35 g L?1 would probably result in reduced yields.  相似文献   

14.
In the present study, we investigate the short‐term adaptive physiological strategies to polycyclic aromatic hydrocarbon (PAH) of Pacific oysters, Crassostrea gigas, by exposing the oysters to varying levels of PAH (0, 50, 100 and 200 μg L−1) for 7 days with a 3‐day acclimation period under laboratory conditions. The filtration rate (FR) and respiration rate (R) increased significantly at 50 μg L−1 PAH and decreased at 100 and 200 μg L−1 compared with the control. The absorption efficiency (Abs. eff.) was significantly impaired at 200 μg L−1 PAH. Ammonia excretion (E) increased with increasing PAH levels, with a significant elevation at 200 μg L−1. Although a significantly elevated FR was observed, oysters exposed to 50 μg L−1 PAH showed scope for growth (SFG) similar to the control. This indicates that even at nominal levels, PAH contamination is a possible cause of reduced oyster production because of increased food demand. The oysters exposed to 200 μg L−1 PAH showed negative SFG values, which could be a possible cause of growth stagnation or even mortality when the exposure is chronic.  相似文献   

15.
Marbled spinefoot, Siganus rivulatus, is a herbivorous euryhaline teleost widely distributed in the Eastern Mediterranean. It is an economically valuable species and a suitable candidate for warm water aquaculture. Accordingly, understanding the effects of environmental factors on fish metabolism is important to optimize culture conditions. Two experiments were performed to establish standard metabolic rate and study the effect of salinity on metabolism of marbled spinefoot. In the first experiment, a series of flow‐through respirometry experiments was performed at 27°C and 35 g L?1. The standard metabolic rate of marbled spinefoot juveniles was calculated as 0.57 ± 0.02 mg O2 g?1 h?1 (mean ± SE). In the second experiment, fish were maintained at salinities of 25, 30, 35 and 40 g L?1 for 2 weeks. Flow‐through respirometry was performed to measure respiration rates at the various salinities. Respiration rates were similar among fish in salinities of 30, 35 and 40 g L?1 but increased significantly at 25 g L?1. Results suggest that despite the euryhalinity of marbled spinefoot, farmers should maintain salinity within the optimal range of 30–40 g L?1 in order to improve productivity.  相似文献   

16.
In this study, we tested the lower salinity tolerance of juvenile shrimps (Litopenaeus vannamei) at a relatively low temperature (20 °C). In the first of two laboratory experiments, we first abruptly transferred shrimps (6.91 ± 0.05 g wet weight, mean ± SE) from the rearing salinity (35 000 mg L?1) to salinities of 5000, 15 000, 25 000, 35 000 (control) and 40 000 mg L?1 at 20 °C. The survival of L. vannamei juvenile was not affected by salinities from 15 000 to 40 000 mg L?1 during the 96‐h exposure periods. Shrimps exposed to 5000 mg L?1 were significantly affected by salinity, with a survival of 12.5% after 96 h. The 24‐, 48‐ and 96‐h lethal salinity for 50% (LS50) were 7020, 8510 and 9540 mg L?1 respectively. In the second experiment, shrimps (5.47 ± 0.09 g wet weight, mean ± SE) were acclimatized to the different salinity levels (5000, 15 000, 25 000, 35 000 and 40 000 mg L?1) and then maintained for 30 days at 20 °C. Results showed that the survival was significantly lower at 5000 mg L?1 than at other salinity levels, but the final wet weight under 5000 mg L?1 treatment was significantly higher than those under other treatments (P<0.05). Feed intake (FI) of shrimp under 5000 mg L?1 was significantly lower than those of shrimp under 150 00–40 000 mg L?1; food conversion efficiency (FCE), however, showed a contrasting change (P<0.05). Furthermore, salinity significantly influenced the oxygen consumption rates, ammonia‐N excretion rates and the O/N ratio of test shrimps (P<0.05). The results obtained in our work provide evidence that L. vannamei juveniles have limited capacity to tolerate salinities <10 000 mg L?1 at a relatively low temperature (20 °C). Results also show that L. vannamei juvenile can recover from the abrupt salinity change between 15 000 and 40 000 mg L?1 within 24 h.  相似文献   

17.
A series of four trials were conducted on inland saline groundwater of 58 g L?1 diluted to lower salinities up to 10 g L?1 and later manipulating its ionic concentrations to enhance the survival and growth of Penaeus monodon postlarvae (PL). In the first experiment, the survival of PL was tested at several salinities (10, 20, 30, 40, 50 and 58 g L?1), and the survival of PL was studied in comparison with natural sea water of similar salinities. Complete mortality of PL was observed at all salinity levels within 144 h. Longest survival for 96 h followed by 72 h was found at 10 and 20 g L?1 salinity respectively. In the second experiment, survival of PL was tested at 10–20 g L?1 salinity at different concentrations of calcium varying between 100 and 300 mg L?1. The survival of PL could be increased to 7 days at 12.5 g L?1 salinity by reducing the calcium level to 200 from 921.8 mg L?1 with magnesium and potassium levels of 208.5 and 30.03 mg L?1 respectively. In the third experiment, the survival of PL could be further enhanced to 18 days at the same salinity by increasing the magnesium level from 208.5 to 400 mg L?1 with potassium held at 30.03 mg L?1. Survival and growth of PL in inland saline water of 12.5 g L?1 salinity similar to performance in sea water of the same salinity was achieved by increasing the potassium concentration from 30.03 to 200 mg L?1 with calcium and magnesium levels of 199.5 and 199.4 mg L?1 respectively.  相似文献   

18.
This paper reports on experiments conducted to examine the combined effects of salinity and potassium concentration on survival and growth of juvenile mulloway (Argyrosomus japonicus, Temminck and Schlegel) in inland saline groundwater. Three separate experiments were conducted in 20 (±1)°C water. In the first experiment, mulloway were held in 60 L aquaria (triplicate) with salinities of 5, 15, 25 or 35 g L?1 and potassium concentrations of 20%, 40%, 60% or 80% of the concentration present in oceanic water of the equivalent salinity in a 4 × 4 factorial combination for 7 days. Response surface contour diagrams were generated from survival data to estimate optimal conditions. The results showed that maximum survival of juvenile mulloway occurred at salinities of >14 g L?1 and potassium concentrations of >38%. Survival was lowest at salinities of <7 and >33 g L?1 and potassium concentrations of <25%. The second experiment was conducted with mulloway held in 60 L aquaria at salinities of 15, 25 or 35 g L?1 and potassium concentrations of 40%, 60%, 80% or 100% in a 3 × 4 factorial combination for 44 days. Optimal conditions for maximum survival and growth of mulloway were within a salinity range of 15–35 g L?1 and potassium concentration above 40%. The third experiment was conducted in three 500 L tanks to record the survival and growth of mulloway fingerlings held at 20 (±1)°C, 23 g L?1 salinity and potassium concentrations of 50% for 8 months. Survival and growth of mulloway fingerling in inland saline groundwater were similar to those reported from a semi‐intensive floating tank system in inland saline water and sea cage trials in oceanic water.  相似文献   

19.
As part of a project to develop least‐cost diets with low levels of fish meal, silver perch (Bidyanus bidyanus Mitchell) fingerlings (mean weight, 11.8 g) were stocked at a density of 7500 fish ha−1 into 0.1‐ha earthen ponds and fed one of two diets containing 33% digestible protein, 13 MJ kg−1 digestible energy, similar nutrient specifications, but with different levels of fish meal and plant proteins. The reference diet SP35 had 27% fish meal, 28% wheat, 20% soybean and 11% sorghum, while the diet silver perch least‐cost (SPLC) had 10% fish meal, 20% peanut meal, 19% wheat, 17% lupins, 16% canola, 8% soybean and 5% blood meal; there were three replicate ponds for each diet. Fish were fed a restricted ration up to 5% body weight day−1 and cultured for 10 months. Survival ranged from 85.9% to 94.3% and was not affected by diet. The mean weight (550 g), specific growth rate (SGR; 1.28% day−1), absolute growth rate (AGR; 1.9 g fish−1 day−1) and production rate (4.5 tonnes ha−1 year−1) were significantly higher (P<0.05) and feed conversion ratio (FCR=1.8) was significantly lower for fish fed SP35 compared with fish fed SPLC (413 g, 1.18% day−1, 1.4 g fish−1 day−1, 3.3 tonnes ha−1 year−1, 2.4). From October (spring) to March (autumn), turbidity was significantly lower (P<0.05) in SPLC ponds than in SP35 ponds, and fish were observed avoiding or ingesting and then expelling SPLC pellets. In February and March, infestations of the ectoparasitic copepod Ergasilus sp. were found on silver perch fed SPLC, and there was 5% post‐harvest mortality of these fish. The high inclusion levels of plant proteins, particularly peanut meal and canola in SPLC, may have provided anti‐nutritional factors and/or reduced the palatability and intake of the diet, adversely affecting the performance and health of silver perch, and water quality in the ponds. Our study demonstrates the value of evaluating new aquaculture diets under practical conditions over a complete growing period.  相似文献   

20.
First‐feeding halibut larvae (245‐day degrees; 40 days post hatch), reared at 34 g L?1 salinity and 7°C, were subjected to handling and allowed to recover in a range of salinities (0–34 g L?1) and at 10°C. Survival of the unfed larvae was determined daily for 18 days. Mortality rates approached 0 after 4 days in all treatments and presumed starvation‐induced mortality started at about 11 days post handling. By 20 days post treatments, all larvae had died. Salinities in the range of 10–20 g L?1 produced significantly (anova , P<0.01) higher initial survival (71–95%) than salinities above 20 g L?1 (24–48%) or below 10 g L?1 (0–19%) and this survival pattern changed little in unfed larvae for the first 10 days following the stressor. For example, 24 hour post handling, survival of halibut was improved from 28.7±16.5% (mean±standard error, n=3) at 34.0 g L?1 to 95.2±4.8% at 13 g L?1. A second‐order polynomial regression of 4‐day post‐handling survival data (y=?0.002x 2+0.0603x+0.0699, r2=0.3936) predicted a maximum survival at 15.1 g L?1 salinity. These results have important implications for halibut aquaculture and research when handling of larvae is unavoidable. For practical applications, we recommend reducing salinity of receiving waters to 15–20 g L?1 with a slow (3–4 days) reacclimation to ambient conditions.  相似文献   

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