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1.
Shi drum specimens were maintained under four different photoperiod regimes: a natural photoperiod regime (16L:8D), constant light (24L), equal durations of light and dark (12L:12D) and a reduced number of daylight hours (6L:18D) from hatching until the end of larval metamorphosis. Specimens were then kept under natural photoperiod conditions until 111 days post-hatching. Muscle and body parameters were studied. During the vitelline phase, there was little muscle growth and no photoperiod effects were reported; however, a monolayer of red muscle and immature white muscle fibres were observed in the myotome. At hatching, external cells (presumptive myogenic cells) were already present on the surface of the red muscle. At the mouth opening, some presumptive myogenic cells appeared between the red and white muscles. At 20 days, new germinal areas were observed in the apical extremes of the myotome. At this stage, the 16L:8D group (followed by the 24L group) had the longest body length, the largest cross-sectional area of white muscle and the largest white muscle fibres. Conversely, white muscle hyperplasia was most pronounced in the 24L group. Metamorphosis was complete at 33 days in the 24L and 12L:12D groups. At this moment, both groups showed numerous myogenic precursors on the surface of the myotome as well as among the adult muscle fibres (mosaic hyperplastic growth). The 16L:8D group completed metamorphosis at 50 days, showing a similar degree of structural maturity in the myotome to that described in the 24L and 12L:12D groups at 33 days. When comparing muscle growth at the end of the larval period, hypertrophy was highest in the 16L:8D group, whereas hyperplasia was higher in the 24L and 16L:8D groups. At 111 days, all groups showed the adult muscle pattern typical of teleosts; however, the cross-sectional area of white muscle, white muscle fibre hyperplasia, body length and body weight were highest in the 24L group, followed by the 12L:12D group; white muscle hypertrophy was similar in all groups. Larval survival was higher under natural photoperiod conditions compared to all the other light regimes.  相似文献   

2.
The effects of five different light regimes on growth performance and behaviour of Persian Sturgeon larvae were examined. Larvae were reared under five different photoperiods (24L, 12L:12D, 16L:8D, 8L:16L and 24D), from hatching (25.8 ± 8.1 mg; 12 ± 0.6 mm) to 28 days post‐hatch (dph). Except the last week, there was no significant difference in growth parameters among the experimental groups. Growth performance significantly improved in larvae reared under a continuous light regime. The highest final length (34.5 ± 1.7 mm) was measured in 24L and the lowest one (29.5 ± 0.4 mm) in the constant darkness. Relative to other experimental groups, the continuous darkness had a retarding impact on the yolk sac absorption and swarming behaviour. Among the whole body compositions, the lowest body moisture content was measured in the continuous light group. Persian Sturgeon pre‐larvae and larvae were not completely dependent on light regimes (in 1–21 days), whereas on the basis of measured parameters (total length, wet and dry weight and digestive fullness index) a continuous light regime played a decisive role on growth performance beyond 21 dph.  相似文献   

3.
Caspian roach (Rutilus rutilus caspicus), a spring spawning teleost, were subjected to various photoperiod and temperature regimes to study the feasibility of shifting the timing of spawning for artificial propagation purposes. A total of 650 female reproductively mature R. rutilus caspicus were subjected to different photoperiod and temperature regimes including four light regimes (natural light (NL), 16 hr of light (L):8 hr of darkness (D), 9L:15D, 11L:13D), each affected by three temperature regimes (14, 20 and 24°C) for 70 days. Five fish per tank were randomly sampled on Feb. 10, Feb. 20, March 28, April 15 and April 30 (natural spawning time). Ovarian tissue sections were studied using light microscope and transmission electron microscope (TEM). The levels of 17‐β estradiol (E2) and 17α‐hydroxyprogesterone (OHP) were also measured in the serum samples. In late winter (March 28th), the gonadal maturation and spawning were accelerated in fish treated with the long day length (16L/8D) and warm temperature (20°C). While, the maturation of oocytes and spawning delayed in fish exposed to low temperature (14°C) and short day length (9L/15D and 11L/13D). Photoperiod seems to play a more important role in the ovarian development of the R. rutilus caspicus compared to temperature; since even among the fish treated with the lowest temperature (14°C), those exposed to a longer day length (16L/8D), matured and spawned earlier than the others. Considering that the earliest spawning occurred in R. rutilus caspicus treated with 16L/8D at 20°C and the latest spawning occurred in fish exposed to low temperature and short photoperiod, it can be concluded that temperature and photoperiod play an important role in accelerating oocyte maturation and spawning.  相似文献   

4.
A two‐factor experiment incorporating two photoperiods (16 L:8 D and 24 L:0 D) and four feeding intervals (6, 9, 12 and 24 h) was carried out to determine the most efficient feeding interval and photoperiod for striped knifejaw, Oplegnathus fasciatus. Fish were fed a commercial diet to apparent satiation for 10 weeks. Blood was collected to measure the stress indicators. Both the photoperiod and the feeding intervals had a significant effect on the growth performance of striped knifejaw; however, their interaction did not produce any significant effect. The final body weight, weight gain (%) and feed intake at 6‐, 9‐ and 12‐h feeding intervals under 16 L:8 D were significantly higher than those at the 24‐h interval irrespective of the photoperiod (P<0.05). The specific growth rate at 6, 9 and 12 h intervals of the 16 L:8 D photoperiod was significantly higher than that of the other feeding intervals, except at 12 h of the 24 L:0 D photoperiod (P<0.05). At the end of the experiment, there were no significant differences in the plasma levels of cortisol, glucose and total protein observed in fish exposed to different photoperiods compared with the initial levels. The results suggested that a combination of a 16 L:8 D photoperiod and either of 6‐, 9‐ or 12‐h intervals can be used to stimulate the growth performance in striped knifejaw.  相似文献   

5.
Calanoid copepods, including species of the genus Acartia, are commonly used as larval diets for marine finfish. This study aimed to determine the separate effects of water temperature (18, 22, 24, 28° ± 0.5°C) and photoperiod (24L:0D; 18L:6D; 12L:12D; 8L:18D; 0L:24D) on Acartia grani egg production (EP), hatching rate (EHR) and population growth. Egg production rate was not affected by the two abiotic parameters. A. grani eggs incubated at T24°C and T28°C were the first to achieve 50% hatching rate (23–25 hr), with significant differences at the end of the experiment (48 hr) between T28°C treatment (EHR 88 ± 5%) and T18°C treatment (EHR 65 ± 2%). However, different temperature regimes did not affect final number of individuals in population growth experiment. Still, when eggs were excluded from data, population at lower temperatures (18°C) was mainly composed by the nauplii stage (72%), while at higher temperatures (24°C and 28°C) more than 60% of the population was composed by copepodites and adults. A. grani subjected to long‐day photoperiods had significantly lower EHR (16.7% at 24L:0D; 20.8% at 18L:6D) than at short‐day photoperiods (52.6% at 6L:18D; 50.0% at 0L:24D). In population growth experiment, eggs were the most common life stage after 12‐day culture. Lowest population number was found at constant light conditions (665.0 ± 197.1), suggesting higher metabolic rates and depletion of energy reserves in long‐day conditions. This study expanded knowledge on the biological response of A. grani to separate temperature and photoperiod regimes, and provided ground to improve the culture of this potential life feed species for hatcheries.  相似文献   

6.
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   

7.
This study aimed to evaluate the performance of Pyrrhulina larvae, Pyrrhulina brevis, under different photoperiods and feeding frequencies. A completely randomized design was used, with four replicates in a 5 × 2 factorial, with five photoperiods (6L:18D, 12L:12D, 16L:8D, 20L:4D, 24L:0D) and two feeding frequencies (two or four times a day). Four hundred larvae with an initial length of 4.6 ± 0.09 mm were randomly distributed in 40, 1‐L containers at a density of 10 larvae/L. Feeding was performed with Artemia nauplii in the ratio of 150 Artemia nauplii/larva/feeding. After 15 days, all larvae were euthanized for measurements of length (mm), final weight (mg), survival rate (%) and larvae uniformity in weight an length (%). The data were subjected to analysis of variance and subsequently, in case of significance, a Tukey test was performed to compare means. There was no interaction between photoperiod and feeding frequency on studied variables (P > 0.05). Likewise, there was no influence of feed rate on the same variables (P > 0.05). There was only influence of photoperiod, where the larvae subjected to longest photoperiods (24L:0D and 20L:4D) showed improved weight and length (P < 0.05). Therefore, a photoperiod of 20L:4E, with feeding twice a day is recommended.  相似文献   

8.
Populations of the coconut crab, Birgus latro, have been severely depleted on most inhabited islands throughout the Indo‐Pacific regions because of overharvesting and environmental degradation. To assist in the development of artificial propagation technologies for supportive breeding programmes in conserving this species, this study was designed to elucidate the effect of photoperiod on the survival, developmental period of zoeae and body size of megalopae through laboratory experiments. We tested six light (L) and dark (D) photoperiod regimes times of 0–24 h, thus 0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D. Photoperiod conditions significantly affected larval survival. Survival was lower in the 0L:24D condition than in other photoperiod conditions, reflecting higher mortality during the zoeal stage in the 0L:24D condition. On the other hand, survival rates were high during the periods when larvae metamorphosed into megalopae, regardless of photoperiod conditions. In the 24L:0D condition, larval survival rate was slightly lower than in other conditions containing a light phase. Zoeal duration and megalopal body size were not different in light durations ranging from 0 to 18 h, but they were longer and larger, respectively, in the 24L:0D condition. Thus, continuous dark or continuous light conditions impaired the survival and development of larvae, and such photoperiod regimes should be avoided for culturing larvae of the coconut crab.  相似文献   

9.
There is considerable interest in rearing Southern flounder, Paralichthys lethostigma, for commercial production and for stock enhancement. Both goals depend upon excellent larval nutrition for the production of robust juveniles. The current use of live prey for larviculture is an expensive and time consuming process that can be alleviated by weaning larvae onto dry feed. A study was conducted to assess the potential for early weaning of southern flounder larvae onto a microdiet (MD). In addition, the activity of selected digestive enzymes was measured during ontogeny to evaluate the digestive capabilities of the larvae over time. Pancreatic enzyme activities (U larva− 1) were very low or undetectable at hatching and a marked increase in activity was not observed until the larvae reached 4 mm (~ 11 dph) in standard length for chymotrypsin (24–44,000) and 6 mm (~ 25 dph) for amylase (< 1–24), trypsin (1–18) and bile salt-dependent lipase (0–443). Acid protease activity (~ 1.0) was detected once the larvae were 8.5–9.0 mm (37–39 dph) in length although a sizeable increase in activity (> 10.0) was not observed until after complete metamorphosis (> 11.0 mm; 40–45 dph). Feeding regimes employed for the weaning study consisted of a live feed control (C) and a combination of live feed and MD in which the addition of the MD was initiated on 11 dph and live feed terminated on 17 (T17), 23 (T23) or 29 (T29) dph. At the end of the study (35 dph), mean standard length and the percent of settled fish were significantly greater for fish in the control treatment (8.3 mm; 21.1%) than for fish fed any combination of live prey and MD (6.4 mm; 2.0%). Average survival was 27.7% and no significant differences were noted among treatments. However, the number of fish exhibiting spinal deformities, lordosis, was significantly lower in the control and T29 treatments (1.7%) than the T17 and T23 treatments (25%). The results of this study indicate that southern flounder larvae readily wean onto dry feed prior to the onset of metamorphosis. However, decreased growth and a high incidence of lordosis emphasize the need for the development of a more appropriate MD for this species when digestive enzyme activities are relatively low and gastric digestion is absent.  相似文献   

10.
Adult red sea bream, Pagrus major (body weight, 1.0–2.0 kg) was exposed to three photoperiods [12 h light:12 h dark (12L:12D), 16 h light:8 h dark (16L:8D) and 24 h light:0 h dark (24L:0D)] from 2 months before spawning till the end of the spawning season to investigate growth, spawning and stress response. During the spawning season, tanks were checked every morning for spawned eggs. The growth performance in fish under 24L:0D was stimulated with significantly higher feed intake than those under other photoperiods (P<0.05). The number of eggs and gonadal histology confirmed that three and five females out of six in each of duplicate tanks of the 16L:8D treatment spawned. In contrast, only two out of six females in one tank of the 24L:0D treatment spawned, and no spawns were observed in the 12L:12D treatment. At the end of the spawning period, both 17β‐estradiol and testosterone levels were significantly higher in fish exposed to 16L:8D followed by 12L:12D and 24L:0D photoperiods (P<0.05). Photoperiod manipulation did not cause significant stress response in fish (P>0.05). The results suggest that stimulating the growth performance of red sea bream at reproductive stage with a 24L:0D photoperiod is possible if the fish are subjected to this photoperiod long before the onset of the spawning season.  相似文献   

11.
Systemic granulomatosis is the most frequent disease in juvenile and adult meagre, but studies regarding the first appearance of granulomas in larvae do not exist. In order to evaluate this, meagre larvae were fed four different feeding regimes as follows: RS and RO (rotifer enriched with Easy DHA Selco or Ori‐Green from 3 to 30 dph respectively), RAS and RAO (rotifer enriched with Easy DHA Selco or Ori‐Green from 3 to 21 dph and Artemia enriched with Easy DHA Selco or Ori‐Green from 12 to 30 dph respectively). All treatments were also fed with commercial microdiet from 20 to 30 dph. At 30 dph weight, length, specific growth rate and survival were significantly higher in Artemia‐fed larvae, regardless of the enrichment. Microscopic first appearance of granulomas was observed in 20 dph larvae fed RS and RO. At 30 dph granulomas and thiobarbituric acid reactive substances (TBARS), values were significantly higher in RS and RO‐fed larvae than in RAS and RAO‐fed larvae. The results showed that granulomas first appeared in meagre larvae at 20 dph when fed rotifers only. Conversely, a reduced appearance of granulomas and lipid peroxidation occurs when Artemia is included in the feeding sequence reinforcing the hypothesis of a nutritional origin of the systemic granulomatosis.  相似文献   

12.
The shortfin silverside Chirostoma humboldtianum has been considered for culture in Mexico, but success has been limited by a poor knowledge of its early development. First synthesis of the early development of the shortfin silverside is presented to determine conditions suitable for rearing. Brooder maturation was induced through photothermal cycles. C. humboldtianum ova were fertilized in vitro. The eggs were incubated in reconstituted water (160-180 mg/L CaCO3) at 18 °C and 5 gm of NaCl per litre. During the hatching day, 300 shortfin silversides were stocked and followed up until metamorphosis in order to establish the timing of exogenous feeding, changes in food type, growth and development during critical periods for survival, according to the theory of saltatory ontogeny. Free embryos hatched 12 days after fertilization at 18 °C. First critical point for survival is the beginning of exogenous feeding. Free embryos started mixed feeding on day four of post-hatching (dph), point of no-return was presented towards the end of mixed feeding on 6 dph, larval period began at six (dph) when the anus is opened, and metamorphosis to juvenile was presented at 65 dph with a SL of 19.34 ± 2.28 mm, when scales and fins were well developed. Differences in growth between periods were detected: free embryos growth slower than larvae but mouth size depicted a larger growth rate in the former. Cephalic length and mouth size were negatively related to standard length in embryos and larvae. Mouth size was positively related to cephalic length in free embryos but negative in larvae. Results suggest that during the free embryo phase, growth priorities are directed to the development of apparatuses and systems; whereas, during the larval period, energy is directed to growth in length, mouth size and development of fins, which allows them to increase their swimming velocity, grants them a greater capacity to obtain exogenous food and, in consequence, increases fitness for survival.  相似文献   

13.
Zebrasoma flavescens (Bennett) aquaculture is limited by high mortality during first feeding. Photoperiod, light intensity, turbidity and prey density are culture parameters that have been shown to affect feed incidence and survival in some food fish species, offering a logical starting point to improve first feeding in Z. flavescens. This study aimed to determine the effect of photoperiod, light intensity, turbidity and prey density on feed incidence and survival in larval yellow tang age 3 DPH to 5 DPH (days post hatch). Larvae were reared in four photoperiods (24L:0D, 16L:8D, 12L:12D, 0L:24D), four light intensities (1,500, 3,000, 4,500 and 6,500 lx), three turbidity ranges (0 cells/ml, 100,000–200,000 cells/ml and 400,000–600,000 cells/ml) and four prey densities (1, 3, 6 and 9 per mL). Photoperiod at 16L:8D and 12L:12D significantly increased feed incidence; 16L:8D significantly increased survival. Light intensities at 3,000 and 4,500 lx significantly increased feed incidence. Larvae reared in 400,000–600,000 cells/ml fed and survived significantly better than those in clear water. Larvae in 1 per mL fed and survived significantly less than those fed at 6 per mL.  相似文献   

14.
Seahorse populations throughout the world are vulnerable toexploitation for use in traditional Chinese medicines. Variouscaptive breeding ventures have been established in attempts tomeet the demand and to reduce the pressure on the naturalpopulations. Many of these programmes have relied on the captureof wild pregnant males which then give birth under captiveconditions. This would however limit production during the non-breeding season. In this study Knysna seahorses, Hippocampuscapensis, were bred in captivity during the non-breeding season(winter) using photothermal manipulation. Three constantphotoperiods (20L:4D, 16L:8D & 12L:12D) were tested incombination with three temperatures (22 °C, 25 °C& 28 °C). All combinations tested were successful inextending the breeding season of H. capensis. The frequency ofpregnancies as well as the number of young produced/pregnancy wasnot affected by the different photoperiod/temperaturecombinations. Each male gave birth to 39.38 ± 20.81juveniles every 34.03 ± 17.25 days during a four monthperiod. The mean juvenile weight and length was influenced by thephotoperiod and/or temperature regimes. Juvenile length decreasedwith increasing temperature (p 0.0001), while an increasein the light phase of the photoperiod regime at 20L:4D resultedin a significant increase (p 0.0006) in length whencompared to the 16L:8D and 12L:12D photoperiods. Juvenile weightdecreased with increasing temperature, while the combination ofphotoperiod 16L:8D and the lowest water temperature (22 °C)yielded the highest mean weights. Further studies are necessaryto determine whether mean juvenile weight or length influencesjuvenile survival  相似文献   

15.
The aim of this study was to determine the effect of photoperiod on growth and survival of winter flounder, Pseudopleuronectes americanus, from hatch until metamorphosis. Sixteen 100 L upwelling tanks were stocked with larvae at an initial stocking density of 20 larvae/L. Larvae in eight tanks were provided with continuous light (24 hr light/0 hr dark), while those in the remaining eight tanks were grown under a photoperiod of 14 hr light/10 hr dark. Tanks were sampled for larval standard lengh from 6 to 28 days post‐hatch, and the number of live larvae, live metamorphosed and dead metamorphosed fish were recorded at the termination of the experiment (starting 46 dph). Results indicated that larvae provided with continuous light were larger than those sampled from 14 hr light/10 hr dark treatment. No effect of photoperiod on the number of non‐metamorphosed fish recovered at the end of the experiment was detected. On the contrary, over three times as many fish survived and reached metamorphosis under continuous light. An ANCOVA model showed a significant interaction between light and age. Both regressions were significant and provided the following growth equations: SL24 hr light/0 hr dark = 0.101 × age + 2.55 (r2 = 0.96) and SL14 hr light/10 hr dark = 0.094 × age +2.45 (r2 = 0.97). Using 6.36 ± 0.059 mm SL as the mean size at metamorphosis, larvae experiencing continuous and 14 hr light/10 hr dark photoperiods would reach metamorphosis in 38 and 42 days respectively.  相似文献   

16.
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   

17.
The effectiveness of co-feeding loach ( Misgurnus anguillicaudatus ) larvae with live and microparticle diets on weaning performance was described here. Dry weight, total length, length and weight-specific growth rate (SGR) and survivals were monitored at 23–25 °C from the 4th day post hatching (dph) in different diet regimes, which included: microparticle diets (A), live cladocerans (B), enriched cladocerans (C), half microparticle diets plus half live cladocerans (D) and half microparticle diets plus half enriched cladocerans (E). The SGR (L and W) were significantly lower in treatment A than in other treatments after completing metamorphosis (day 4–20, P <0.05). On 30 dph, dry weight (mg) and total length (mm) were significantly lower in treatment A than in other treatments ( P <0.05). There were no significant differences in growth in treatments B, C, D and E before 30 dph. However, when live feed was withdrawn from 31–60 dph, in metamorphosed fish, there were significant differences ( P <0.05) among the treatments in survival and growth. Metamorphosed fish in treatment E had higher survival than the fish in other treatments at the end of the experiment. The SGR (L and W) of weaned fish in treatments B and C were similar but lower than in treatments A, D and E respectively. However, dry weight and total length in treatment A were significantly lower than in treatments D and E. It is suggested that weaning of M. anguillicaudatus from early development would appear to be feasible and that larval co-feeding improves the growth and the survival.  相似文献   

18.
The growth performance and stress response in striped knifejaw, Oplegnathus fasciatus (body weight 100–300 g) reared under four photoperiods (6L:6D, 12L:12D, 16L:8D and 24L:0D) were investigated. Fish were fed a commercial diet to apparent satiation, two times a day for 8 weeks. A trial of acute handling and confinement stress was also carried out to investigate the stress-induced levels of different stress indicators in O. fasciatus. Blood was also collected from undisturbed fish which was considered as control. Although there were no significant differences in weight gain, specific growth rate (SGR) and feed conversion efficiency (FCE) in fish exposed to 6L:6D, 16L:8D and 24L:0D photoperiods, all parameters in these photoperiods were significantly higher than those of 12L:12D photoperiod (P < 0.05). There was no significant difference in protein retention efficiency (PRE) between fish exposed to 16L:8D and 24L:0D photoperiods, but PRE in both photoperiods was significantly higher than that of 12L:12D photoperiod.Acute stress significantly increased the plasma levels of cortisol (110.3 ng ml− 1) and glucose (195.4 mg dl− 1), and decreased plasma levels of total protein (0.8 g dl− 1); however, all parameters were returned back to the levels indistinguishable from those of control, undisturbed fish within 24 h. The levels of cortisol, glucose and total protein in fish exposed to different photoperiods during the study were far from the stress-induced levels (P < 0.05). The results demonstrated that the growth performance of O. fasciatus reared from 100 to 300 g can be stimulated significantly by using the manipulated photoperiods where feeding time may be playing an important role to increase food intake and feed conversion efficiency. It also revealed that the artificial photoperiods did not cause significant stress response in fish.  相似文献   

19.
Like all poikilotherms, the growth and reproduction of blue crab, Callinectes sapidus depends on temperature and season. Warmer water temperatures in the Chesapeake Bay allow for ovarian development and spawning, while colder water temperatures slow their metabolism and reproduction. The current study aimed to identify optimal environmental conditions for inducing reproduction in animals held in long‐term captivity for year round production in aquaculture through environmental manipulations. Temperature and photoperiod were the main environmental factors tested for 25 weeks: 11°C and 21°C, with the following photoperiods: 0L:24D, 8L:16D, 16L:8D and 24L:0D. At 21°C, the females increased spawning frequency, which was arrested at 11°C. Shorter light exposure at 21°C increased spawning frequency, while constant light inhibited and did not produce spawning. Constant dark (0L:24D) at 21°C produced the most (86%) spawns, but yielded poor larval quality. At 21°C with all photoperiod conditions except constant light, the first spawning took 94.8 ± 32.4 days to occur (n = 17). With females producing multiple spawns, the intervals between the first and second spawns and the second and third spawns were 37.7 ± 8.7 days (n = 6) and 31.0 ± 7.1 days (n = 2) respectively. Analysis of our data using response surface methodology (RSM) predicts the following conditions: at 15–19°C and 0–10 hr darkness for maximal survival and at 19–22°C and 0–8 hr darkness for spawning. The number of larvae produced was positively correlated with size (weight) of the female C. sapidus, suggesting the importance of female size in reproduction.  相似文献   

20.
The goal of this experiment was to examine the effects of different light qualities (red, white, blue) and cycles (12L:12D, 8L:16D, 4L:20D, 0L:24D, 16L:8D) on the survival, growth, metabolism and antioxidant defence system of Haliotis discus hannai Ino. Under red and white light at 4L:20D, the body weight‐specific growth rate of abalones was significantly higher than that of the 0L:24D group (P < 0.05). At 16L:8D, succinate dehydrogenase activity decreased and lactate dehydrogenase and alanine aminotransferase activity and the lactic acid content significantly rose (P < 0.05) in the red and white light groups. Under blue light, reactive oxygen species and malondialdehyde content for each light cycle were significantly higher than those of the red and white groups (P < 0.05). Under blue, white and red light, total antioxidant capacity (T‐AOC), superoxide dismutase (SOD) activity, glutathione peroxidase (GPX) activity and reduced glutathione (GSH) content gradually rose with increased duration of light exposure. Under red light, significant differences in these parameters were detected between the 4L:20D and 16L:8D groups (P < 0.05). Under blue and white light at 16L:8D, values of T‐AOC, SOD, GPX activity and GSH content were significantly lower than those of the 12L:12D group (P < 0.05). Overall, these results indicate that red light at light cycles of 4L:20D and 8L:16D is optimal for the culture and production of H. discus hannai, as these conditions promoted food intake, growth and health maintenance as well as normal physiological metabolism of the organism.  相似文献   

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