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1.
This study investigated the effect of different light intensities on feeding, growth and survival of early stage leopard coral grouper Plectropomus leopardus larvae. Four different light intensities (0, 500, 1000 and 3000 lx) were used and larvae were kept under constant light conditions from 0 day after hatching (DAH) to 5 DAH. The larvae were fed a small S-type of Thai strain rotifers at a density of 20 individuals/mL from 2 DAH. The number of rotifers in larval digestive organ and total length of larvae were examined at 3 h intervals between 04:00 and 22:00 h on 3 DAH, and thereafter at 6 h intervals until the end of the experiment (5 DAH). Four experimental trials of the larval rearing were repeated using by 60 kL mass-scale rearing tanks. The results indicate that coral grouper larvae are visual feeders and their food intake increases with increasing light intensity. Food intake of larvae reared at 3000 lx was significantly higher than those reared at 0–1000 lx on 3 DAH despite being the first-feeding day (P < 0.01). On 4 DAH, total length of larvae reared at 3000 lx was significantly larger than those reared at the lower light intensities (0, 500 and 1000 lx), and thereafter light intensity significantly influenced larval feeding and growth until the end of the experiment. Survival on 5 DAH did not show a significant difference between light intensities, but survival rate at 3000 lx and 1000 lx had a tendency to be higher than those reared at the lower light intensities (0 and 500 lx). In contrast, larvae reared at 0 lx exhibited stagnant and/or negative growth. These results indicate that light intensity is significantly the factor affecting larval feeding, growth, and survival in coral grouper larvae under the rearing conditions.  相似文献   

2.
The effects of four light intensities (1000 lx, 500 lx, 50 lx, 3 lx) on growth, survival and feeding activity in common sole (Solea solea L.) larvae were studied from 4 to 51 days post hatching (dph). During the pelagic larval stage (4–12 dph), larvae reared at 3 lx showed a lower growth. From 19 onwards, the larvae reared under 3 lx displayed a significant (P ≤ 0.05) higher SGR than the other treatments and a higher final weight compared to 1000 lx and 500 lx. Survival rate was higher under intermediate light intensities (500 and 50 lx). Larvae reared at 3 lx displayed a significant delay in the degree of metamorphosis compared to the other treatments, while at 33 dph metamorphosis was completed under all treatments. Histological examination revealed the importance of vision and light in the first feeding of this species, while after metamorphosis, the full development of other sensory organs indicated that feeding activity is also mediated by chemosensory perception. Results indicate that high light intensity seems to be more suitable during the pelagic larvae, while the opposite would ensure better growth from the onset of metamorphosis to the benthic phase.  相似文献   

3.
The growth rate, survival rate, development and setting rate of larval sea cucumber Apostichopus japonicus were measured under four light intensities (0, 50, 500 and 2,000 lx), and the growth rate and metabolism of the juvenile sea cucumbers were investigated under four light intensity treatments (0, 100, 1,000 and 2,500 lx). The light requirements (i.e. intensity) of the sea cucumber changed as they grew. Better growth performance, development and survival rate were observed in embryos and larvae under 500 lx treatment. However, reduced light intensity (50 lx) increased the settlement rate of the larvae. The highest specific growth rate occurred in juvenile sea cucumbers under 1,000 lx. The sea cucumbers in this group also had the lowest oxygen consumption rate and ammonia excretion rate, but the highest O:N ratio, indicating that the optimal light intensity for the juvenile sea cucumber culture was 1,000 lx. Therefore, appropriate light intensities were suggested to provide larval and juvenile sea cucumbers with better growth and development conditions.  相似文献   

4.
This study investigated the optimal timing of day to promote initial swimbladder inflation (ISI) for improved Pacific bluefin tuna (PBT), Thunnus orientalis, larval survival. Larval swimbladder inflation frequency was compared based on three experiments using different time schemes of surface film removal (SFR) from 3 to 9 days post hatch (dph). SFR was conducted from 05:00 to 19:00 hours (light period: S.5–19), 19:00 to 05:00 hours (dark period: S.19–5), 08:00 to 19:00 hours (S.8–19) and the entire day (S.24) in Experiment 1; from 08:00 to 19:00 hours (S.8–19‐E2), 08:00 to 13:00 hours (S.8–13), 13:00 to 19:00 hours (S.13–19) in Experiment 2; and from 13:00 to 16:00 hours (S.13–16), 16:00 to 19:00 hours (S.16–19), 18:00–19:00 hours (S.18–19) in Experiment 3. The swimbladder inflation frequency at the experiment termination (9 dph) was significantly higher (P < 0.001) in S.24 (91.1 ± 5.7%), S.5–19 (92.2 ± 5.1%) and S.8–19 (93.3 ± 3.4%) than in S.19–5 (11.1 ± 5.1%) in Experiment 1, and remarkably higher in S.8–19‐E2 (81.7%) and S.13–19 (88.3%) than in S.8–13 (0.0%) in Experiment 2, and significantly higher (P < 0.001) in S.16–19 (84.4 ± 5.1%) and S.18–19 (70.0 ± 12.0%) than in S.13–16 (7.8 ± 3.9%) in Experiment 3. These results suggest that the optimal timing to promote larval ISI by SFR is a few hours before the end of light period (16:00–19:00 hours) from 3 to 9 dph.  相似文献   

5.
Land‐based cultured juvenile Pacific bluefin tuna Thunnus orientalis (PBT) have high mortality rates due to collisions or contacts with tank walls after about 30 days of hatching. To determine the effect of night‐time lighting on their survival, juvenile PBT were reared under four different night‐time light intensities (0, 5, 15 and 150 lx) for 9 days, followed by a 3‐day observation period. High‐intensity, night‐time lighting (150 lx) significantly improved the survival rate (75.8%; P < 0.001) compared with the unlit control group (0 lx, 64.3%). The survival rate in the high‐intensity group decreased after the end of the lighting period. Lighting did not influence whole‐body cortisol levels, glucose levels, or diel changes in plasma cortisol levels. In contrast, the survival rates of fish exposed to light intensities between 5 and 15 lx were slightly lower than that of the unlit control group. These results suggest that providing night‐time lighting of 150 lx or higher is an effective method for reducing the mortality of cultured PBT.  相似文献   

6.
Six light intensities (50, 100, 200, 400, 800, and 1500 lx) were used under a photoperiod of 16 h light : 8 h dark (16L : 8D) to investigate the growth performance and stress response of striped knifejaw, Oplegnathus fasciatus. Forty juveniles of mean weight approximately 27 g were randomly distributed into each of eighteen 300 L tanks, fed to apparent satiation two times a day for 8 wk. At the end of the rearing trial, there were no significant differences in final mean weight, weight gain, specific growth rate, condition factor, and survival among the treatments (P > 0.05). Although there was no significant difference in feed intake, fish exposed to 50–200 lx showed significantly higher feed efficiency (FE) compared to that of other treatments (P < 0.05). There was a decreasing trend in retention efficiency of protein and lipid with increasing light intensities (400–1500 lx), but there were no significant differences among the treatments. There were no significant differences in plasma levels of cortisol, glucose, and total protein among the treatments (P > 0.05). To consider the FE and given the fact that an intensity of 50 lx is insufficient to monitor fish activity during feeding, light intensity of 100–200 lx would be better for rearing of striped knifejaw.  相似文献   

7.
Concentrating methods generally affect the vitality of the microalgae and may alter its feeding and environmental effect. This article studied the concentrating methods (centrifugation and settlement) on primary productivity of the microalgae Cylindrotheca fusiformis. The effects of free settled C. fusiformis, centrifuged C. fusiformis and macroalgae Sargassum polycystum on growth of the sea cucumber, farming water and sediment quality under two light intensities (1500 lx and 500 lx) were studied by a six‐week rearing experiment. The results showed that the primary productivity of free settled C. fusiformis was 3–4 times higher than that of those centrifuged, indicating centrifugation inhibited the photosynthesis process. In the rearing experiment, feed, light intensities and their interactions significantly affected the specific growth rate (SGR) of the animals (P < 0.01). The animals reared in higher light intensity also had higher SGR, but only those fed free settled C. fusiformis reached a significant level (P < 0.05). The group also had the highest SGR (P < 0.05), suggesting that the photosynthesis ability of C. fusiformis directly contributed to the growth of the animals. During the experiment, the soluble inorganic nitrogen, reactive phosphorus in farming water, total nitrogen and total organic carbon in the sediment gradually increased in all treatments. The S. polycystum group had slightly higher level of nutrients in water and sediment at the end of the experiment for its high organic content. These results provide evidence that the harvesting methods of C. fusiformis directly affect its vitality, which consequentially alter the feeding and environmental effect, especially under higher light densities.  相似文献   

8.
本研究以紫海胆(Anthocidaris crassispina)为研究对象,通过水槽实验方法,模拟分析了自然光周期条件下光照强度对紫海胆浮游幼体生长、存活以及体内消化酶活性的影响,旨在为紫海胆苗种的规模化繁育提供必要的生物学参数。研究发现,在实验设计的光照强度梯度(0、500、1000、2000、3000 lx)内,光照强度对紫海胆浮游幼体的体长、躯干部骨针长度和口后腕骨针长度的影响趋势一致,影响程度由高到低为500 lx>0 lx>1000 lx>2000 lx>3000 lx。在500 lx条件下,紫海胆浮游幼体的体长、躯干部骨针长度和口后腕骨针长度都达到最高,且显著优于其他实验组(P<0.05),此时脂肪酶和淀粉酶活性最强;在2000 lx条件下,紫海胆的胃蛋白酶活性最强;在3000 lx条件下,紫海胆浮游幼体发育到11 d已全部死亡。研究表明,在500 lx光照强度下,紫海胆浮游幼体可保持最佳的生长速度、消化酶活性以及存活率,500 lx为紫海胆浮游幼体生长发育的最佳光照强度。  相似文献   

9.
To investigate the effect of scheduled meal timings on growth performance in Cirrhinus mrigala fingerlings, two experiments were conducted. The first experiment was conducted under laboratory conditions and the fish were submitted to schedule meal timings (at 08:00, 12:00,16:00, 20:00, 00:00 and 04:00). A control on continuous feeding was also maintained. ANOVA had revealed a significant (p < .05) increase in live weight gain (g), growth per cent gain in body weight, specific growth rate, PER, GPR, GER and APD (%) values in fingerlings fed between 12:00 and 16:00 hours. A decline in growth parameters, nutrient retention and an increase in FCR values were observed in the group fed at 20:00, 00:00 hours and also in the control group. Studies have further revealed that meal timings had also significantly (p < .005) affected protein digestibility, nitrogen retention and excretion of metabolites . Fish carcass composition had significantly (p < .05) higher accumulation of protein (14.82 ± 0.032), fat (5.51 ± 0.006) and energy (5.95 ± 0.004) in the group fed at 16:00 hours. The second experiment was conducted under field conditions and the fish were submitted to schedule meal timings (at 08:00, 12:00, 16:00 and 20:00). A control on continuous feeding was also maintained. Significantly (p < .05) higher values in growth parameters were observed in the group fed at 16:00 hours and lower values in the group fed at 20:00 hours and also in controls. Water quality, nutrients and productivity status of ponds revealed favourable levels and appears to have been affected by meal timings. Thus, in C. mrigala, timings of food intake can serve to optimize the utilization of ingested calories.  相似文献   

10.
Light intensity during the early life stages of fish can have profound effects on their survival, developmental rate, yolk utilization efficiency and body size. Here, these aspects were analysed during two separate experiments (with or without exogenous food) on two distinct progenies of African sharptooth catfish, at five different light intensities (<0.1, 70, 500, 2500 and 8000 Lx; 24L:0D, 27.2°C). The duration of the egg incubation period (from 1.01 to 1.25 days post fertilization, dPF) was inversely proportional to light intensity, as hatching took place at more precocious developmental stages with increasing light intensity, i.e. at significantly (P < 0.05) shorter body length and slightly more abundant remaining yolk at 8000 Lx in comparison to <0.1 Lx. At the start of exogenous feeding (4 dPF), most of these differences had vanished. During the period of mixed feeding (until the end of yolk absorption, 11 dPF), growth decreased significantly with increasing light intensity. Daily mortality rates after hatching varied very little between light intensities. Mortality during egg incubation increased significantly (P < 0.05) with increasing light intensity, whereas it varied very little between light intensities thereafter, with the best survival rates since fertilization until the end of yolk absorption obtained at intermediate light intensities (70–2500 Lx). These results could be useful for improving the performance of African sharptooth catfish hatcheries.  相似文献   

11.
In this work performance parameters of larval pike-perch (Sander lucioperca) reared under four different light intensities (100, 500, 1000 and 2500 lx) until 21 days post hatch (dph) were investigated. As performance parameters change in length and weight, swim bladder inflation, feed consumption, natural mortality, stress induced mortality and RNA-DNA ratio were measured. Aim was to investigate the influence of light intensity on pike-perch performance during the first three weeks of larval rearing. Significant differences were found in natural and stress induced mortality as well as in weight growth. No single light exposure level combined optimal performance of all tested performance parameters. Highest light intensity of 2500 lx showed good weight growth but an increase in stress induced mortality. Bright light of 500 and 1000 lx intensity was found to improve growth and stress mortality whereas dim light conditions of 100 lx showed significantly lower natural mortality. Thus data suggested that most favorable illumination during larval pike-perch rearing comprise a tradeoff between optimal natural mortality under dim light conditions (100 lx) or optimal larval growth and stress resistance under bright light conditions (500 and 1000 lx). It is shown that high light intensities during larval rearing can be beneficial for pike-perch rearing if offspring supply is not limited.  相似文献   

12.
The effect of stocking density and photoperiod on Hippocampus abdominalis was examined in this study. Stocking densities of 45, 30, 15 and 5 seahorses 3 L?1 were tested on newborns. Growth and survival were independent of stocking density. A second stocking‐density experiment aimed to remove the effect of an early mortality experienced in experiment 1 using older juveniles at 25, 15 and 5 seahorses 3 L?1. There were no differences in the parameters measured. Also, the effect of photoperiod was investigated on seahorses cultured under 24:00, 16:08 and 08:16 (L:D) photoperiods. A single Artemia meal was delivered at 10:00 hours. Survival and body growth in 16:08 and 08:16 hours were higher than in 24:00 hours. In a second experiment, seahorses were cultured in the photoperiods and conditions described for experiment 1, except they were fed twice the amount in two meals delivered at 10:00 and 16:30 hours. The seahorses in 16:08 hours showed better growth than the other treatments, but there were no differences in survival. These results suggest that early juvenile H. abdominalis can be cultured at higher stocking densities than previously reported, without compromising growth and survival, and when feeding was not limiting, grew better in an extended photoperiod (16:08) but not in 24:00 hours.  相似文献   

13.
This study examined the retinomotor responses and prey ingestion rates of 10‐, 15‐, 20‐ and 30‐day‐old Asian seabass Lates calcarifer under different light intensities from 0 to 1000 lx to determine the visual thresholds. Subsequently, two age groups of seabass larvae were reared under light intensities of 10, 100 and 1000 lx to determine the optimum illumination in hatchery tanks. Retinomotor response was absent in 10‐day‐old larvae, but quite marked in 15‐ and 20‐day‐old seabass at 1 lx and higher. Ingestion of Artemia nauplii by 10‐day‐old larvae was almost zero at <1 lx, increased significantly at 1 lx, and was maximal at 10–100 lx. Artemia ingestion under dim light <1 lx improved with age, and older larvae took more prey in complete darkness due to the presence of rod cells (and also free neuromasts). Larvae from 13 to 26 days group had similar survival and growth at 10–1000 lx, however, from 5 to 10 days group showed similar survival rate with highest weight gain at 100 lx. Therefore, we recommend that hatchery rearing tanks be illuminated such that the larvae in the water are exposed to approximately100 lx.  相似文献   

14.
The diel feeding rhythm and ontogenesis during early life stage of loach Misgurnus anguillicaudatus were investigated under experimental conditions (light: L 06:00–18:00, D 18:00–06:00 h). Morphological and behavioral developments of loach from newly hatched to 40 days after hatching were observed. Larvae were able to prey on daphnia 3–4 days after hatching at 23 ± 0.5°C. As the larvae grew, they showed an increasing feeding capacity and a distinct feeding rhythm. Feeding intensity and incidence for day-4 larvae were highest at 10:00 and 16:00 h. The highest levels of feeding intensity for day-12 larvae occurred at 08:00, 12:00, and 18:00 h as did feeding incidence. By day 20, when the larvae metamorphosed, the highest levels of feeding intensity occurred at 06:00, 18:00, and 24:00 h and were concurrent with the highest feeding incidence. After metamorphosis, feeding capacity had again increased considerably and, in contrast to the earlier stages before day 20, feeding intensity for day-30 juveniles peaked at 05:00 and 20:00 h, about 1–2 h after the maximum feeding incidence. The feeding rhythm of loach juveniles at day 40 was almost the same as the day-30 juveniles. The estimated maximum daily feeding rates were 43.1%, 33.4%, 19.0%, 12.8%, and 5.8% of body weight on days 4, 12, 20, 30, and 40, respectively. Thus, loach was found to have different feeding rhythms in the pre- and post-metamorphosis stages, with the highest feeding activity in daytime during the larval planktonic stage before metamorphosis, and intensely nocturnal feeding behavior during the juvenile benthic stage after metamorphosis.  相似文献   

15.
Eight light‐intensity treatments (natural light, continuous darkness, and 15, 30, 60, 125, 250 and 500 lx under LD 12:12 cycle) were used to investigate the effects of light intensity on the daily activity of 30.27±3.08 g sea cucumber Apostichopus japonicus (Selenka). Cyclic nocturnal activity patterns of behaviour were observed at different light intensities in the range of 15–500 lx under LD 12:12 cycle. And an ongoing nocturnal cycle persisted in DD cycle for up to 8 days, but longer feeding time and less marked rhythm occurred at continuous darkness. Under poor light conditions (I<5.18 lx), the daily activity rhythm of A. japonicus was governed by an innate biological clock and the effect of light intensity was not significant among different treatments. And more individuals tended to retreat to shelters (from 56.04% to 91.83%) with the increase of light intensity within the weak light condition (from 5.18 to 278 lx). However, the daily behaviours of A. japonicus were influenced under strong light conditions (>278 lx). Less than 8.17% individuals kept actively feeding and the proportion was not decreased with the increase of light intensity.  相似文献   

16.
Survival rates of the larvae of sutchi catfish Pangasianodon hypophthalmus are reported to be three times higher under dim conditions (0.1 lx) than those under 100 lx. In this study, larval behaviour of sutchi catfish was examined under various light intensities (<0.01, 0.1, 1, 10 and 100 lx) using a CCD camera to understand why survival rates vary under different light intensities. Five‐day‐old larvae showed significantly higher swimming activity under <0.01, 0.1 and 1 lx than those under 10 and 100 lx. On the other hand, the larvae showed significantly higher aggressive behaviour under 10 and 100 lx; swimming larvae attacked resting individuals more frequently under 10 and 100 lx than those under 0 and 0.1 lx. Aggressive behaviour was considered to induce lesions, inflicted by the sharp teeth of attacking larvae, on larval skin surfaces. It is considered that the chemical substances would generate from injured skin surfaces then acted as stimuli, causing the cannibalistic behaviour in other fish around the injured fish. This study provided evidence that the observed higher survival rates depended on lower frequency of aggressive behaviour under dark or dim conditions. It is therefore recommended that larval rearing of sutchi catfish be conducted under dim (less than 1 lx) conditions.  相似文献   

17.
The effects of four light intensities on growth and survival of first‐feeding stage black sea bass larvae Centropristis striata were investigated in a controlled‐environment laboratory. Fertilized eggs, obtained from LHRHa‐induced spawning of captive broodstock, were stocked (72 eggs L?1) into twenty 15 L black tanks under light intensities of 100, 500, 1000 and 1500 lx, with five replicate tanks per treatment. The photoperiod was 12L:12D, the temperature was 20°C and the salinity was 35 g L?1. Larvae were fed rotifers Brachionus rotundiformis from day 2 post‐hatching (d 2ph) at 5–10 rotifers mL?1. Microalgae Nannochloropis oculata and Isochrysis sp. were added (1:1) daily to maintain a density of 300 000 cells mL?1. Hatching success and larval growth and survival from d 2ph through d 15ph were monitored. Hatching success was 28–38% under all light intensities, and notochord length at hatching ranged from 2.8 to 3.0 mm, with no significant differences among treatments. By d 15ph, growth (mg wet weight) was significantly higher in the 1000 lx (0.914) and 1500 lx treatments (0.892) than in 100 lx (0.483), and a highly significant trend (P<0.01) towards increased survival with increasing light intensities was observed, from 1.3% at 100 lx to 13.9% at 1500 lx. Higher light intensities within the range of 100–1500 lx improved growth and survival of early larval black sea bass, suggesting that even higher light intensities may improve culture performance. This is consistent with conditions in shallow, near‐shore locations where eggs and larvae are distributed in nature.  相似文献   

18.
An 8‐week feeding trial was conducted to quantify the dietary l ‐lysine requirement of juvenile Chinese sucker with an initial weight of 1.81 ± 0.04 g reared in indoor flow‐through and aerated tanks. Six isonitrogenous and isoenergetic practical diets were formulated to contain graded levels of lysine (1.23%, 1.80%, 2.39%, 2.98%, 3.56% and 4.18% dry matter) at 0.6% increments from dietary ingredients and crystalline l ‐lysine. Each diet was randomly assigned to triplicate groups of 30 fish each and was fed to apparent satiation by hand three times a day (09:00, 13:00 and 17:00 hours) for 8 weeks. There were significant differences in growth performance and feed utilization among the treatments. Weight gain (WG), specific growth rate and protein efficiency ratio (PER) significantly increased with increasing lysine levels up to 2.39% of diet (P < 0.05) and remained nearly the same thereafter (P > 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (P < 0.05) and showed no significant differences when dietary lysine level increased from 2.39% to 4.18%. The N retention (% N intake) significantly increased with dietary lysine level but did not attain a plateau (P < 0.05). Survival could not be related to dietary treatments. Whole body protein increased (P < 0.05) and whole body lipid decreased (P < 0.05) with increasing dietary lysine level. The condition factor and hepatosomatic index were significantly affected by dietary lysine levels, however, viscersomatic index, whole body moisture and ash did not differ significantly among dietary treatments. Broken‐line analysis on the basis of WG and PER showed that dietary lysine requirements of juvenile Chinese sucker were 2.43% and 2.40% dry diet (5.52% and 5.45% dietary protein) respectively. Based on the ideal protein approach and the A/E ratios determined from muscle amino acid profile an estimation of the EAA requirements of Chinese sucker juveniles were calculated.  相似文献   

19.
The combined effects of temperature (18–34°C) and light intensity (100–1,800 lx) on the vitellus utilization, duration of vitelline absorption and larval growth in Pseudobagrus ussuriensis were studied under laboratory conditions using a central composite design and response surface methodology. The results showed that the first‐ and second‐order effects of temperature and light intensity were significant (p < 0.05), the interactive effect between temperature and light intensity was non‐significant (p > 0.05) and the effects of light intensity were greater than that of temperature. Predicated on the reliable models of vitelline utilization regarding temperature and light intensity, the optimal rearing environment shaped by a temperature/light intensity of 25–26°C/1,030 lx (12.98 μmol m?2 s?1) was obtained via model optimization. Verification results attained under laboratory conditions showed that vitelline utilization was most efficient at these optima. The application of the environmental optima would contribute to refining the seed quality in the larviculture of this species.  相似文献   

20.
We evaluated the effect of light intensity on survival rate and zootechnical performance in matrinxã larvae (Brycon amazonicus) that is an important species for fish farming in the Amazon region. For this, the larvae were submitted to three experimental stages : Stage I—10–72 hr after hatching (HAH), Stage II—72–168 HAH and Stage III—168–288 HAH. The animals were submitted to three treatments of different light intensities: low (±20 lx), intermediate (±200 lx) and high (±2,000 lx). The low light intensity increased the survival rate in 24, 48, 72, 120, 168 and 288 HAH. The size of the animals was homogeneous in 72 and 168 HAH in the low and intermediate treatments. The high light intensity increased the zootechnical parameters in 288 HAH. We suggest the use of low light intensity in the initial periods of observation (24 and 48 HAH) to reduce aggressiveness and increase the survival and homogeneity of the animals. On the other hand, it is possible to suggest an increase in the light intensity in the final period of observation (288 HAH), as the increase in intensity stimulated growth and affected the survival rate of the matrinxã larvae.  相似文献   

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