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1.
This study investigated the effect of continuous temperature decrease on hemocyte apoptosis of the white shrimp Litopenaeus vannamei. In the stress group, water temperature decreased from 26 to 17 °C at a rate of 1 °C/h. Shrimp kept at 26 ± 0.5 °C were used as control group. Total hemocyte count (THC), reactive oxygen species (ROS) production, cytoplasmic free-Ca2+ (CF-Ca2+) concentration, mitochondrial membrane potential (MMP), apoptotic cell ratio, and caspase-3 activity of L. vannamei hemocytes were determined when water temperature decreased to 23, 20, and 17 °C, respectively. Increased ROS production in hemocytes was observed when water temperature decreased to 20 and 17 °C. Decreased THC and cellular MMP, increased CF-Ca2+ concentration, apoptotic cell ratio, and caspase-3 activity were shown when water temperature decreased to 17 °C. These results indicate that water temperature decrease can induce oxidative stress on shrimp hemocytes and then cause mitochondria and caspase-3 mediated hemocyte apoptosis and THC reduction, when water temperature decreased to an unconformable level.  相似文献   

2.
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   

3.
The aim of this study was to reveal possible interactive effects of temperature and photoperiod on somatic and skeletal growth, feed conversion, organ indexes and blood chemistry in Atlantic salmon postsmolts. A total of 1140 (initial mean weight 96.0 g ± 3.1 SEM) juvenile Atlantic salmon reared in seawater were in duplicates exposed to six different combinations of temperatures (4.3, 6.5 or 9.3 °C) and photoperiods (continuous light, LL or simulated natural photoperiod (69ºN), LDN) for 124 days. An interactive effect of photoperiod and temperature on somatic growth was found as the fish exposed to low temperature and continuous light regime (4LL) had a significantly higher growth (30 % gain in overall SGR) than the 4LDN group, corresponding to the effect of approx. 1.2 °C temperature increase. Fish in the 6 and 9 °C groups did not show any significant growth benefit of continuous light. Compared to the 4LDN group, the 4LL group showed higher total feed conversion efficiency, lower levels of blood Na+ and lower hepato-somatic and cardio-somatic indexes. In the skeleton, cervical vertebra were largest in the 4LL group, while the length of the head was largest in the 4LDN group, continuous light promotes growth at lower temperatures while supporting a normal development. It is suggested that a considerable growth benefit may be achieved by exposing juvenile Atlantic salmon to continuous light when reared at low (in this trial 4.3 °C) water temperature during winter.  相似文献   

4.
We have used the cyclopoid copepod Paracyclopina nana to understand responses to the temperature shift. To determine the changes of molecular mechanisms, which would lead to physiological changes in P. nana, we investigated mRNA expression involved in lipogenesis, the area of lipid droplets, the ratio of fatty acids, and life parameters (growth and fecundity) in response to temperature changes (15, 20, and 30 °C) with comparative control at 25 °C. Setting the temperature 25 °C as a standard point, there were increases in mRNA expression, the area of the lipid droplets, and fatty acid composition at temperatures below the standard (15 °C), while all the markers mentioned above significantly decreased at higher temperatures than the standard (25 °C). Through fecundity and growth rate experiments, daily nauplii production was reduced and growth retardation was observed at both 15 and 20 °C, but no noticeable differences in the two parameters were observed at 30 °C compared to the control (25 °C). This study provides a better understanding of the effects of temperature on lipogenesis in copepods.  相似文献   

5.
In this study, two experiments were conducted to test the effect of high temperature on survival, behavior, oxygen consumption, ammonia-N excretion, and enzyme activities related to oxidative stress of the Japanese scallop Mizuhopecten yessoensis. In the first test, we abruptly transferred scallops from the rearing temperature (15 °C, control temperature) to 20, 22, 24, and 26 °C. Scallops exposed to 26 °C were significantly affected by temperature, with 100 % mortality after 12 h. The 8-, 12-, 24-, 48-, and 96-h lethal temperatures for 50 % mortality (LT50) were 27.5, 24.4, 24.3, 24.2, and 23.8 °C, respectively. The activities of CAT and SOD and the T-AOC in the coelomic fluid of M. yessoensis changed significantly after high-temperature stress (P < 0.05). They reached to the highest levels after 8 h of stress in the 22, 24, and 26 °C treatment groups then returned to the control group level. The content of MDA reached the highest level after 12 h in each temperature treatment. In the second test, scallops were acclimatized to the different temperature levels (20, 22, 24, and 26 °C) and then maintained for 30 days. Survival was significantly lower at 26 °C than at the other temperatures, and the highest survival occurred in the 15 °C treatment. High temperature also significantly influenced the oxygen consumption rates and ammonia-N excretion rates (P < 0.05). As the temperature increased, the CAT and SOD activities and the T-AOC in the coelomic fluid of M. yessoensis declined significantly, whereas the MDA content increased. These results illustrate that high temperature can significantly affect the survival, behavior, oxygen consumption, ammonia-N excretion, and enzyme activities related to oxidative stress of M. yessoensis.  相似文献   

6.
Abstract – The persistent effects of embryonic temperature stress and individual parentage on fry swimming performance were examined in a cross‐fertilisation experiment using sockeye salmon (Oncorhynchus nerka). A fixed‐velocity test of burst swimming was used to assess the endurance capacity and behavioural performance of individual fry from 10 offspring families incubated at 12, 14 or 16 °C to hatch and then reared through yolk absorption and exogenous feeding stages in a common posthatch environment (average 6.9 °C). Fry burst swim time (BST) was influenced by an interaction between incubation temperature and family identity. Average BST was longer for fry from the 12 °C prehatch treatment compared to 14 and 16 °C, although differences were largely attributable to temperature effects on average fry size. Behavioural observations revealed that fish incubated at 16 °C performed more poorly, having a larger proportion of individuals that required stimulation to swim, fatigued more frequently or were classified as ‘nonswimmers’. Within all three incubation temperature treatments, mean BST varied significantly among offspring families, independent of fry mass and length. An interesting relationship was observed within the 16 °C treatment, whereby families with higher survivorship were characterised with lower mean BSTs. Collectively, these findings demonstrate that exposure to high temperatures in early sockeye salmon development can result in persistent, parentally mediated effects on fry performance. As such, these results provide important insight into how elevated temperature events during egg incubation may affect early life history selection processes and survival in stages beyond when the stressor is experienced.  相似文献   

7.
A series of experiments were conducted to evaluate the effect of temperature and the microalgae Isochrysis sp. concentration on the copepod Pseudodiaptomus euryhalinus cultured in laboratory conditions. First, the ingestion rate of P. euryhalinus was evaluated with different concentrations of Isochrysis sp. [2.74, 5.47, 8.21, 10.94 and 16.41 µg mL?1 organic dry weight (ODW)] during 24 h, at a temperature of 24.3 ± 0.3 °C. The ingestion rate increased in direct proportion to microalgae concentration, reaching an asymptotic point at 16.41 µg mL?1. P. euryhalinus was then cultured for 11 days at 24.4 ± 0.3 °C with different concentrations of Isochrysis sp. (5.47, 8.21, 10.94 and 16.41 µg mL?1 ODW) in order to quantify the optimal food density. It was observed that food concentration did not have a significant effect on the development, growth, maturity, fecundity and survival of P. euryhalinus. The effect of different temperatures (19.4 ± 0.5, 21.9 ± 1.0, 24.2 ± 0.3, 27.8 ± 0.5 and 30.1 ± 0.8 °C) on the development, growth, survival and sex ratio of P. euryhalinus fed with Isochrysis sp. at 5.47 µg mL?1 ODW was evaluated for 11 days of culture. The temperature had an inversely proportional effect on the time of development, and highest survival and growth were observed at 24.2 ± 0.3 °C. Finally, the effects of different temperatures (21.7 ± 0.5, 24.2 ± 0.3, 27.2 ± 0.3 and 30.7 ± 0.6 °C) in nauplii production of adult copepods were evaluated during 11 days. Nauplii production increased in direct proportion with the temperature. These results suggest that the optimum temperature and food concentration for P. euryhalinus culture are 24.2 ± 0.3 °C and 5.47 µg mL?1 ODW of Isochrysis sp., respectively.  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 effects of acclimation temperature (15, 20, 25 °C) on routine oxygen consumption and post-exercise maximal oxygen consumption rates (MO2) were measured in juvenile shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818). The routine MO2 of shortnose sturgeon increased significantly from 126.75 mg O2 h?1 kg?1 at 15 °C to 253.13 mg O2 h?1 kg?1 at 25 °C. The temperature coefficient (Q 10) values of the routine metabolic rates ranged between 1.61 and 2.46, with the largest Q 10 values occurring between 15 and 20 °C. The average post-exercise MO2 of all temperature groups increased to a peak value immediately following the exercise, with levels increasing about 2-fold among all temperature groups. The Q 10 values for post-exercise MO2 ranged from 1.21 to 2.12, with the highest difference occurring between 15 and 20 °C. Post-exercise MO2 values of shortnose sturgeon in different temperature groups all decreased exponentially and statistically returned to pre-exercise (resting) levels by 30 min at 15 and 20 °C and by 60 min at 25 °C. The aerobic metabolic scope (post-exercise maximal MO2-routine MO2) increased to a maximum value ～156 mg O2 h?1 kg?1 at intermediate experimental temperatures (i.e., 20 °C) and then decreased as the temperature increased to 25 °C. However, this trend was not significant. The results suggest that juvenile shortnose sturgeon show flexibility in their ability to adapt to various temperature environments and in their responses to exhaustive exercise.  相似文献   

10.
Groups of Atlantic salmon (Salmo salar) eggs were incubated at 12, 10 and 8° C. At 12° C mortality was high and fry averaged little more than half the weight of those hatched at 10 or 8° C. Development of alevins to the ‘swim-up’ stage was also abnormal at 12° C. The results suggest that 10° C is optimal for incubating Atlantic salmon eggs. For the period between hatching and swim-up, the most favourable temperature varies according to the temperature used during incubation. Mortality rate during the first 6 weeks of feeding was correlated with mortality during earlier development. Total numbers of day-degrees required by the eggs and fry to reach the eyed, hatching, and swim-up stages of development were significantly less at 12° C than at 10 or 8° C. However, total day-degrees required to reach an average weight of 0.5 or 0.6 g were almost the same regardless of temperature during hatching.  相似文献   

11.
Five pairs of paternal half-sib families of pink salmon (Oncorhynchus gorbuscha) were transferred from fresh to 28‰ salt water 1, 7, and 28 days after button-up of the fry and reared for 51 days at 13°C. In another experiment, pink salmon from three populations were also reared in fresh and salt water at 9.5°C for 49 days after fry button-up. Juvenile growth and survival rates were greater when juveniles were reared for a period of time in fresh water after button-up. Juveniles transferred to salt water 1 day after button-up had the lowest growth and survival rates. Juveniles reared at 13°C grew up to five times faster than those reared at 9.5°C. There was evidence of genetic differences in juvenile growth and survival among half-sib families.  相似文献   

12.
Two feeding trials were conducted to determine the effects of feeding rates in juvenile Korean rockfish, (Sebastes schlegeli) reared at 17 and 20 °C water temperature. Fish averaging 5.5 ± 0.2 g (mean ± SD) at 17 °C and 5.5 ± 0.3 g (mean ± SD) at 20 °C water temperature were randomly distributed into 18 indoor tanks. At each water temperature, triplicate tanks were randomly assigned to one of six different feeding rates: 2.8, 3.8, 4.1, 4.4, 4.7 % and satiation (4.99 % BW day?1) at 17 °C and 2.8, 3.8, 4.1, 4.4, 4.7 % and satiation (5.0 % BW day?1) at 20 °C. After 4 weeks of feeding trial, weight gain (WG) and specific growth rate of fish fed groups at satiation and 4.7 % (BW day?1) were significantly higher than those of fish fed groups at 2.8, 3.8 and 4.4 % (BW day?1) in both 17 and 20 °C temperature. Feed efficiency and protein efficiency ratio of fish fed group at 2.8 % (BW day?1) was significantly lower than those of fish fed groups at 3.8, 4.1, 4.4 and 4.7 % (BW day?1) in both experiments. Hematocrit was significantly higher in fish fed group at 4.4 % (BW day?1) at 17 °C, and there was no significant difference in hemoglobin content amongst all fish fed groups at 20 °C. Glutamic oxaloacetic transaminase and glutamic pyruvic transaminase of the fish fed group at 2.8 % (BW day?1) were significantly higher than those of all other fish fed groups in both experiments. Broken line regression analysis of WG indicated that the optimum feeding rate of juvenile Korean rockfish was 4.48 % (BW day?1) at 17 °C and 4.83 % (BW day?1) at 20 °C. Therefore, these results indicated that the optimum feeding rate could be >4.1 % but <4.48 % at 17 °C and >4.4 % but <4.83 % at 20 °C. As we expected, current results have indicated that 5 g of juvenile Korean rockfish perform better at 17 °C than at 20 °C water temperature.  相似文献   

13.
A study was conducted to investigate the potential of purified lignin and hemicellulose as prebiotics in diets for Atlantic salmon, Salmo salar L., postsmolt in seawater (30 ppt) at 14.9 ± 1.2°C. Triplicate groups of fish (initial individual body mass of 101.6 ± 1.2 g) were fed either the fishmeal-dense (32% of fishmeal) control diet (A) or one of the nine diets (15% fishmeal) supplemented with lignin:hemicellulose ratios (% diet:% diet) of 0.05:0 (B), 0.25:0 (C), 0.50:0 (D), 1.00:0 (E), 0:0.05 (F), 0:0.25 (G), 0:0.50 (H), 0.05:0.25 (I), and 0.25:0.50 (J) for 12 weeks in a complete randomized experimental design. At the end of the experiment, the thermal-unit growth coefficient (TGC) was significantly lower in salmon fed diets with 0.50% and 1.00% purified lignin than those fed the control diet, while there was no significant difference between the other treatments and the control diet (P < 0.05). The feed efficiency (FE) was significantly lower in salmon fed diets with 0.50% and 1.00% purified lignin and 0.05% hemicellulose than those fed the control diet, while there was no significant difference between the other treatments and the control diet (P < 0.05). The hepatosomatic index (HSI), intestinal villus length, and apparent digestibility coefficient (ADC) of nutrients in diets were similar (P > 0.05) among all the diets. This study demonstrated that inclusions of up to 0.25% of dietary purified lignin alone, and 0.25%–0.50% of dietary hemicellulose alone or in combination with dietary lignin can be considered as candidate prebiotics in Atlantic salmon nutrition.  相似文献   

14.
The present study evaluated the difference in the sex ratio (the genotypic and phenotypic female ratios) and the growth parameters between normal male offspring and neomale offspring under tank culture conditions. The phenotypic female ratio of normal male offspring (20.46–63.79 %) in four families and three stocks was remarkably higher than that of neomale offspring (5.21–10.53 %) in three neomale families and three neomale stocks (p < 0.01), while there was no significant difference between normal male offspring (30.41–70.60 %) and neomale offspring (29.7–70.83 %) in the genotypic female ratio (p > 0.05). The sex reversion ratio (SRR) was analyzed based on the genotypic and phenotypic female ratios. In neomale offspring, the SRR ranged from 84.25 to 92.53 %, while in normal offspring the SRR ranged from 9.65 to 34.60 %. There was a significant difference between normal male offspring and neomale offspring in the SRR (p < 0.01). The weight and length were measured at the ages of 300, 600, and 720 days. The growth rate was analyzed by the statistics, and there was a significant higher growth rate in the normal family than the neomale family (p < 0.05). The results suggest that the slower growth in the neomale offspring is responsible for the high SRR.  相似文献   

15.
A 30-day acclimation trial was conducted using Tor putitora to elucidate its thermal tolerance, oxygen consumption, haemato-biochemical variables and selected enzymatic activities at five acclimation temperatures (AT). Juveniles of T. putitora were randomly distributed among five treatment groups (20, 23, 26, 29 and 32 ± 0.5 °C). There was a significant curvilinear increase in critical thermal maxima (CTmax) (y = ?0.0693x 2 + 1.7927x + 34.628, R 2 = 0.996) and lethal thermal maxima (LTmax) (y = ?0.1493x 2 + 2.3407x + 35.092, R 2 = 0.991) with increasing AT. The oxygen consumption rate increased significantly with increasing AT. The Q 10 values were 1.16 between 20 and 23 °C, 3.09 between 23 and 26 °C, 1.31 between 26 and 29 °C and 1.76 between 29 and 32 °C of AT. The acclimation response ratios were ranged between 0.37 and 0.59. Catalase, superoxide dismutase and ATPase activities were increased linearly in liver, gill and kidney, while brain acetylcholine esterase activity decreased linearly with increasing AT. Blood glucose remained unchanged up to AT of 26 °C and increased significantly at AT of 29 and 32 °C. Haemoglobin content was increased linearly with increasing AT. The highest WBC count was observed at 20 °C, and no significant changes found till AT of 26 °C and significantly decreased at 32 °C. Total serum protein and globulin were significantly decreased with increasing AT. Highest values were observed at 20 °C and remained consistent till 26 °C, then decreased significantly. There was no significant change in A/G ratio through the AT 20–29 °C and increased significantly at 32 °C. The increase in CTmax, LTmax and oxygen consumption rate with increasing AT may suggest that the thermal tolerance of T. putitora is dependent on its prior thermal exposure history, and it could adapt to higher AT by altering its haemato-biochemical variables.  相似文献   

16.
This study was designed to assess the potential effects of Astragalus membranaceus (AM) on the growth performance and antioxidative stress response in bluegill sunfish (Lepomis macrochirus) exposed to challenging cold water temperature conditions. In this regard, fish with an average weight of 43 ± 1 g were divided into four groups and fed daily with an AM-free diet (control), and 1.5, 3, and 4.5 % (w/w) AM-incorporated diets for an 8-week period. Oxidative stress response, biochemical, and growth parameters were measured, and subgroups of fish were exposed to the outside challenging cold pond water temperature (1.6–9.9 °C) with an average of 7.0 ± 0.1 °C beyond the optimal temperature. The results showed that incorporating AM in the diet significantly improved growth performance parameters (body mass gain, specific growth rate, length, condition factor, and feed conversion ratio) and biochemicals (aspartate aminotransferase and alanine transaminase activities, and glucose and cortisol concentrations). In addition, markedly up-regulated superoxide dismutase, glutathione peroxidase, and catalase activities were observed in AM-treated fish groups over the control. Conclusively, feeding AM diets significantly increased (P < 0.05) growth performance and antioxidative stress profiles throughout the entire experiment, and this increase was much more pronounced at 8 weeks after the water temperature began to rise, which can be related to the nature of Bluegill fish as it is known to be a warm water fish. These findings are considered to be of great importance for sustainable aquaculture.  相似文献   

17.
An experiment was conducted to study the stress mitigation and growth enhancing role of dietary l-tryptophan (TRP) under thermal stress in rohu, Labeo rohita fingerlings for 45 days. Seven hundred and twenty fishes were distributed in three major groups that are ambient temperature (26 °C), 34 and 38 °C in triplicate following a complete randomized design. Acclimation of fishes to 34 and 38 °C over average ambient temperatures were carried out at 1 °C/day. Each group was fed with a diet supplemented with 0, 0.36, 0.72 or 1.42 % l-TRP. Results showed that blood glucose and serum cortisol level were found to be significantly higher (p < 0.05) in the higher temperature groups than the ambient temperature group. Similarly, aminotransferase, lactate dehydrogenase, malate dehydrogenase, CAT, superoxide dismutase activities were found to be significantly higher (p < 0.05) in the control groups (0 % l-TRP) and decreasing activities of these enzymes were observed with the increasing level of dietary l-TRP. In different temperature groups, l-TRP-supplemented groups were found to have higher (p < 0.05) growth, RGR and PER. The results obtained in the present study indicate that dietary l-TRP mitigates thermal stress and enhances growth. From the present study, we can conclude that dietary supplementation of l-TRP at the 0.72 % level in the diet is found to be optimum to reduce thermal stress even up to 38 °C in rohu, L. rohita. The baseline data obtained here could be useful for the farmers to formulate feeds to culture the fish in different agro-climatic zones.  相似文献   

18.
This study examined the effects of acclimation temperature (10, 15, 20, or 25 °C) and an acute exposure to various temperatures on the routine metabolism of juvenile (~11 g) shortnose sturgeon (Acipenser brevirostrum). For the acclimation experiment, the minimum, mean, and maximum routine metabolic rates were established for sturgeon at each temperature. Mean routine metabolic rates for 10, 15, 20, and 25 °C were 134, 277, 313, and 309 mg O2 kg?1 h?1, respectively, with significant differences occurring between 10 and 15, 10 and 20, and 10 and 25 °C. For the acute exposure, similar patterns and significant differences were observed. Temperature quotient (Q 10) values indicate that the greatest effect of temperature occurred between 10 and 15 °C for both the acclimation and acute temperature experiments. In addition, the effect of temperature on the metabolic rate of sturgeon was nearly negligible between 15 and 25 °C. These results suggest that juvenile shortnose sturgeon are sensitive to temperature changes at the lower end of the range, and less sensitive in the mid-to-upper temperature range.  相似文献   

19.
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   

20.
The relationship between the level of the intestinal mucosa amylolytic activity (AA) of juvenile goldfish Carassius auratus, carp Cyprinus carpio, roach Rutilus rutilus and perch Perca fluviatilis and the rate of water temperature increase was studied. Increase in water heating rate significantly influences AA and the level of upper lethal temperatures defined by critical thermal maximum (CTM) during different seasons. At a low rate of water temperature increase, 0.04 °C/h, AA and the level of CTM are maximal during all seasons. More rapid rates of heating, 4–50 °C/h, increase the AA during the summer and usually decrease it by 2- to 7.5-fold during other seasons. Rapid increase in ambient temperature in the autumn–winter period, unnatural for seasonal dynamics, produces a negative impact upon the fish’s carbohydrate hydrolysis rate and thermal resistance.  相似文献   

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