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1.
Feeding performance (intensity and incidence) of first‐feeding yellowtail kingfish larvae was evaluated under a range of light intensities and algal‐induced turbidities. Larvae were fed with varying degrees of success under all light intensities tested (0–17 μmol s?1 m?2), in both clearwater and greenwater (8 × 104 cells mL?1). There was a consistent trend for feeding performance to increase with larval age and light intensity in both clearwater and greenwater conditions, demonstrating that visual proficiency increases with larval age. Feeding intensity remained low over the first 3 days of first feeding across all light intensities tested. Days 6 and 7 post‐hatch larvae showed considerably higher feeding intensities particularly at 8 and 17 μmol s?1 m?2. This improvement indicates an ontogenetic shift in sensory or locomotor competence. First‐feeding larvae performed equally well in both clearwater and greenwater (8 × 104 cells mL?1) conditions, although at the lowest light intensity tested (0.1 μmol s?1 m?2) feeding performance was noticeably reduced. Feeding performance was severely diminished across all larval ages at an algal cell density of 32 × 104 cells mL?1, demonstrating that for this species algal‐induced turbidities >16 × 104 cells mL?1 adversely affect the ability to capture free‐swimming prey during the first‐feeding window.  相似文献   

2.
Initial larval stocking density, prey density, daily prey ration and light conditions (light intensity and photoperiod) were tested for common dentex larval rearing under experimental conditions. Experiments continued until the first peak of larval mortality. The best results in larval survival were obtained with an initial stocking density of between 10 and 40 larvae L?1, fed with at least 10 rotifers mL?1, maintaining ratios of 500–1000 rotifers larva?1, with one or two adjustments of prey density per day. The use of more than 2000 rotifers larva?1 or three daily adjustments of live prey density had negative effects on larval survival. The best light conditions for common dentex larval rearing were found using a photoperiod of 24 h L:0 h D and an intensity of at least 3.4 μmol m?2 s?1.  相似文献   

3.
The optimal conditions for growth of Porphyra dioica gametophytes were investigated in the laboratory, focusing on bioremediation potential. Porphyra dioica is one of the most common Porphyra species along the northern coast of Portugal and can be found year-round. The influence of stocking density and photon flux density (PFD) on the growth, production and nutrient removal was tested. Maximum growth rates, up to 33% per day, were recorded with 0.1 g fw l− 1 at 150 and 250 μmol photons m− 2 s− 1. Growth rate decreased significantly with increasing stocking density. Productivity (g fw week− 1) had an inverse trend, with more production at the higher stocking densities. At 150 μmol m− 2 s− 1 and with 1.5 g fw l− 1, 1.4 g fw week− 1 were produced. At this PFD, there was no significant difference in production between 0.6 to 1.5 g fw l− 1. Nitrogen (N) content of the seaweeds decreased with increasing stocking densities and PFDs. The maximum N removal was recorded at 150 μmol m− 2 s− 1, with 1.5 g fw l− 1 stocking density (1.67 mg N day− 1). However, the N removed by thalli at 50 μmol photons m− 2 s− 1 was statistically equal to that at 150 and 250 μmol photons m− 2 s− 1, at a stocking density of 1.0 g fw l− 1. The influence of temperature and photoperiod on growth and reproduction was also assessed. Growth rates of P. dioica were significantly affected by temperature and photoperiod. In this experiment (with 0.3 g fw l− 1 stocking density), the highest growth rate, 27.5% fw day− 1, was recorded at 15 °C and 16 : 8¯, L : D¯. Male thalli started to release spermatia 21 days after the beginning of the experiment, in temperatures from 10 to 20 °C and with 10, 12 and 16 h of day length. Unfertilized female-like thalli were observed at 10 to 20 °C, under all photoperiods tested. Growth of these thalli declined after 4 weeks. By then, formation of young bladelets in the basal portion of these thalli was observed. After 7 weeks all biomass produced was solely due to these vegetatively propagated young thalli, growing 22.4% to 26.1% day− 1. The results of this study showed that P. dioica appears to be a candidate as a nutrient scrubber in integrated aquaculture systems.  相似文献   

4.
The objective of this study was to compare the effect of six light intensity/photoperiod combinations (2500 lux/18 h, 2500 lux/15 h, 2500 lux/12 h, 500 lux/18 h, 500 lux/15 h and 500 lux/12 h) on seed production in the Nile tilapia Oreochromis niloticus L. Each combination represented a treatment and was triplicated in 0.4‐m3 fibreglass tanks within a recirculating water system. Water temperature was maintained at 29.0 ± 1.0 °C. Males and females with mean body weights of 116.8 and 91.6 g, respectively, were stocked at a rate of eight fish/tank with a male to female ratio of 1:3. Seeds (eggs, sac fry and swim‐up fry) were collected every 2 weeks. The experiment lasted for a total of 120 days. The results showed that the 2500 lux/18 h treatment produced significantly greater (P < 0.05) total seed/tank (4944), seed kg?1 female day?1 (50.9), seed m?2 day?1 (40.3) and seed/ female day?1 (6.7) than treatments with medium or short photoperiods (15 and 12 h day?1 respectively) or lower light intensity (500 lux). The degree of spawning synchrony and percentage of the sac and swim‐up fry stages were significantly higher in the 2500 lux/18 h treatment than in the other treatments. Under the conditions tested in this study, seed production and spawning synchrony in the Nile tilapia may be improved by subjecting breeders to a light intensity of 2500 lux and a photoperiod of 18 h day?1.  相似文献   

5.
A local algal isolate Tetraselmis tetrathele was studied to determine the suitable levels of three growth factors (nutrient medium, light intensity and photoperiod) for mass culture. Significantly higher population cell count (141.92 × 104) were found in 4‐day‐old cultures (exponential phase) enriched with Conwy medium and exposed continuously to 93.31–103.5 μmole photon m?2 s?1 light intensity compared with two other media (F, SEAFDEC/AQD) under the same light conditions. Cultures exposed to higher levels of photosynthetic photon flux density and continuous photoperiod had a significantly higher cell count regardless of nutrient media used. The chemical composition of T. tetrathele varied as the culture aged. Significantly higher crude protein (49.6%) and crude ash (15.9%) were found in cultures harvested at exponential than at stationary phase of growth. In contrast, significantly higher carbohydrate (55.2%) was noted as the culture aged. There was an increase in the percentage of saturated, monoenoic and n‐3 highly unsaturated fatty acids at the stationary phase of growth. Addition of filtrate from various phases of growth and from 10‐day‐old cultures at various concentrations stimulated cell growth of T. tetrathele. This study identified the optimum growth conditions for mass culture of T. tetrathele and demonstrated its change in the chemical composition as the culture aged.  相似文献   

6.
The effects of temperature and light intensity on the growth and toxicity of Heterosigma akashiwo (Hada) were studied in the laboratory. The growth and toxicity of this organism were found to be greatly influenced by temperature and light intensity. The best growth was found at 25 °C where the toxicity was very low. On the other hand, cells were found to be most toxic at 20 °C (0.087 ± 0.005 FU), although the growth was much less than at 25 °C. The lowest toxicity was observed at 30 °C with a toxicity of 0.011 ± 0.005 FU. The toxicity of this species also differed markedly at different light intensities. It gave the maximum toxicity at 200 μE m?2 s?1, but poor growth. The best growth occurred at 100 μE m?2 s?1, but with a marked toxicity drop. In toxin composition studies, the amounts of most of the toxic fractions were lower at 25 °C and 100 μE m?2 s?1 where the growth was most conspicuous.  相似文献   

7.
In two separate experiments, haddock (Melanogrammus aeglefinus) larvae were raised under different photoperiods (24L : 0D or 15L : 9D), or different combinations of tank colour (black or white) and light intensity (1.1 mol s–1 m–2 or 18 mol s–1 m–2). Growth (0.8% day–1 in standard length; 2.9% day–1 in body area) and survival (2%) were not significantly different between photoperiod treatments after 35 days. Larval survival was greater in white versus black tanks after 41 days (2% versus l%, respectively). Growth of larvae was impaired in black tanks at low (1.1 mol s–1 m–2) light intensity (0.8% day–1 in standard length and 2.2% day–1 in body area versus 1.1% day 21 in standard length and 3.1% day–1 in body area, for all other treatments). Transmission and reflection of light was low in black tanks at low incident light, and there was very little upwelling light. The resultant poor prey to background contrast probably resulted in larvae being unable to consume sufficient food to sustain a level of growth comparable to that in other treatments.  相似文献   

8.
Sporeling and tissue propagation of agarophytic seaweed, Gracilaria fisheri, aimed to investigate the optimal shading colour for the preservation. This study was conducted under different shading colours indoor and outdoor experiments. The indoor experiment: tissues and sporelings of the seaweed were cultured in plastic chambers under fluorescent lights and were wrapped with white, green, blue and red colour PVC sheets of light intensity of 20 ± 1 μmol m?2 s?1. The outdoor tissues were cultured in the plastic tanks under different shadings of Saran sheets: white, green, blue and black covering the hoop‐houses with light intensity of 110 ± 10 μmol m?2 s?1. The results showed that different shading colours strongly influenced growth of G. fisheri sporelings and tissues but little effect on pigmentation. After 40 days, the highest growth rates of G. fisheri tissues and sporelings were found under red light with 1.44 and 1.89% day?1 respectively. There was no significant difference (P > 0.05) on pigment content of tissues indoor, whereas it was found that chlorophyll concentration of the sporelings under green light with 416.8 μg g?1 fresh weight was significantly higher (P < 0.05) than those in other treatments. After 8‐week culture, outdoor tissues showed the highest growth rate with 1.71% day?1 in the green hoop‐house. The study has found that G. fisheri cultivation was less influenced by epiphytes in the back hoop‐house with 15%. This study showed the feasibility of successful cultivation of G. fisheri sporelings and tissues.  相似文献   

9.
Light is a key environmental factor that influences the growth, culture and survival of aquatic organisms. This study examined the effects of different light qualities (red, orange, white, blue and green light) and intensities (5 μmol m?2 s?1, 15 μmol m?2 s?1 and 40 μmol m?2 s?1) on the hatching and metamorphosis of larva of Haliotis discus hannai Ino and the growth and survival of juveniles. It was found that under blue and green light, the hatching success rate and metamorphosis of larva were significantly higher than those for any other light quality (P < 0.05), and there was a decreasing trend with an increase in light intensity. Under red and orange light, the abnormality rate of trochophores in each light intensity treatment and the time required for the metamorphosis of larva were significantly higher than those for any other light group (P < 0.05). Both the abnormality and metamorphosis rates significantly increased with light intensity. Under white light, at an intensity of 40 μmol m?2 s?1, the settlement and size of larva at metamorphosis were significantly smaller than those for any other light intensity (P < 0.05). Under red and orange light, the SGR of juvenile abalone in each light intensity treatment was significantly lower than that in any other light group (P < 0.05), but no significant difference was identified (P > 0.05). Therefore, selecting blue and green light and controlling the light intensity to 5–15 μmol m?2 s?1 during fingerling reproduction of abalone should increase the hatching success rate of larva and the yield per water body.  相似文献   

10.
The red alga Chondria crassicaulis has a wide‐ranging bioactive chemical composition and is used as a local foodstuff, representing a potentially new cultivar in Korea. The cultivation techniques were developed by examining the monthly changes in frond weight in a field population of C. crassicaulis from November 2016 to October 2017. For seedling production, temperature and irradiance effects on the attachment and growth of vegetative propagules of C. crassicaulis were evaluated. In addition, effects of day length and salinity on the propagule growth were examined. C. crassicaulis is a year‐round species with a maximum frond wet weight of 817 mg observed in July 2017, as seawater temperature increases to 20°C. The attachment of vegetative propagules was significantly affected by temperature and irradiance, with maximal values detected at 20–25°C and 60 µmol photons m?2 s?1. The relative growth rates of vegetative propagules of C. crassicaulis were the highest at 20–25°C, 60 µmol photons m?2 s?1, and a salinity of 25 psu. In conclusion, due to its tremendous tolerance under variable environmental conditions, the vegetative propagules of C. crassicaulis can be used as seedlings for mass cultivation.  相似文献   

11.
The effects of irradiance and photoperiod on the biomass and fatty acid (FA) composition of Chlorella vulgaris were examined in the exponential growth phase. Results indicated significant differences in biomass and FA at different intensities and photoperiods. Maximum biomass (2.05 ± 0.1 g l−1) was at 62.5 μmol photons m−2 s−1 and 16:8 h light/dark photoperiod. FA composition changed considerably in different light regimes; the maximum percentage of total saturated (SFA) (33.38%) was recorded at 100 μmol photons m−2 s−1 and 16:8 h photoperiod, while monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids decreased with increasing irradiance and light duration. The maximum percentage of total MUFA (15.93%) and PUFA (27.40%) was recorded at 37.5 μmol photons m−2 s−1 and 8:16 h photoperiod.  相似文献   

12.
In a small‐scale culture experiment, larval haddock, Melanogrammus aeglefinus L., were raised under various combinations of light quality [blue (470 nm), green (530 nm) or full‐spectrum white light] and light intensity [low (0.3–0.4 µmol  s?1  m?2) or high (1.7–1.9 µmol  s?1  m?2)], and in total darkness (both fed, and starved). Larval growth (0.9% day?1 in standard length; 2.4% day?1 in body area) was not significantly different between any combination of coloured light. At the time of total mortality in the starved treatment, survival was significantly reduced under low intensity, full‐spectrum white light (13%) vs. all other coloured light treatments (68%). Larvae raised under both continuous dark treatments (fed and starved) exhibited morphological changes associated with irreversible starvation (point‐of‐no‐return). Lack of a pronounced effect of light quality on larval haddock growth probably results from a combination of plasticity in early larval vision, and enhanced encounter rates between larvae and prey at the relatively high prey densities used in aquaculture.  相似文献   

13.
Used as a traditional Chinese medicine, the high mortality rate and slow growth of Whitmania pigra larvae are the most serious bottlenecks for the scale development of artificial breeding. Firstly, five light colour treatments (white, blue, green, red and yellow) were tested to determine effects of light spectrum on the growth of larval W. pigra at the same intensity of 70.00 μmol m?2 s?1. The experiment lasted for 45 days. Under our experimental conditions, the weight gain (WG) and the specific growth rate (SGR) under blue light condition were significantly higher compared with the other treatments (P ≤ 0.05). It is reasonable to conclude that blue light can promote the leech growth. In addition, reared at five blue light intensity treatments (20.00 ± 3.84, 40.78 ± 4.18, 53.67 ± 5.98, 70.00 ± 7.26 and 87.33 ± 5.77 μmol m?2 s?1), the WG and SGR increased with increasing intensity. Meanwhile, they were significantly higher in the 70.00 and 87.33 μmol m?2 s?1 treatments (P ≤ 0.05). In the higher intensity light treatments, the digestive enzymes were higher and antioxidant enzymes were lower. These results suggest that the optimal light spectrum for the culture of W. pigra during the early life stage was blue and the optimal light intensity was higher light intensity (70.00–87.33 μmol m?2 s?1).  相似文献   

14.
The combined effects of temperature (23 and 27 °C), light intensity (1100 and 2 lux or ≈ 21.5 and 0.04 μEinst m?2 s respectively) and photoperiod (10 h light/14 h dark and 14 h light/10 h dark) on ovarian maturation and spawning performance of ablated pond‐reared Penaeus merguiensis were investigated in a 51‐day experiment. The results showed that temperature was the most influential factor, followed by light intensity, whereas the effect of photoperiod was minor. As the maturation process progressed, the effects of temperature and light intensity became stronger while that of photoperiod became less significant. Temperature significantly affected all the reproductive parameters assessed. Prawns in the 27 °C treatments outperformed those in the 23 °C treatments (P < 0.05). The effect of light intensity was found to have a significant effect (P < 0.05) only on the proportion of spawners (prawns that spawned) and spawning rate. More prawns spawned at a higher rate under dim light (2 lux) than under strong light (1100 lux). Photoperiod affected only the proportion of prawns reaching stage III of ovarian development (P < 0.05). There were interactions between temperature and light intensity affecting the proportion of prawns reaching stage III and, although not significantly, the proportion of spawners (P = 0.177), fecundity (P = 0.134) and survival (P = 0.061). Overall, it is recommended that a combination of 27 °C, 2 lux and 10 h light/14 h dark is suitable for the maturation of pond‐reared P. merguiensis. There were indications that temperature can be used to control the rate of ovarian maturation. Also, it is possible to increase light intensity up to 1100 lux in P. merguiensis hatcheries if prawns are ablated.  相似文献   

15.
Suitable culture conditions for Rhodomonas sp. Hf-1 strain were examined for high productivity. Hf-1 strain was grown in an incubator for 7 days. The factorial experimental design investigated the following 19 variables: temperature (12, 16, 20, 24 and 28 °C), salinity (7, 14, 21, 28 and 35 psu), light intensity (20, 35, 50, 65 and 80 μmol m?2 s?1), light color (white, red, green and blue lights), and 3 factorial designs of photoperiod (24L:0D, 16L:8D and 12L:12D light:dark cycle). The cell density and specific growth rates (SGR) were analyzed. The best cell growth was observed under the following culture conditions: temperature of 24 °C, salinity of 21 psu, light intensity of 80 μmol m?2 s?1, and white light. In the photoperiod test, the highest cell density of 4.7?×?106 cells ml?1 was obtained at 24L:0D light:dark cycle, and the SGR was 0.57 μ day?1 at this time. We found that the Hf-1 strain was able to be cultured in extremely wide culture conditions. These results are expected to serve as a baseline study for culturing the Hf-1 strain in the laboratory and for its use in aquaculture.  相似文献   

16.
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   

17.
Photoperiod and stocking density are critical factors influencing the performance of decapod crustaceans in culture, however, their influence on growth; survival and biochemical physiology of crayfish broodstock have rarely been considered. Analysis of biochemical physiology in crayfish broodstock during the non‐breeding season provides information on the energy storage requirements of broodstock for increased survival and reproductive output. Growth rate, moulting frequency, survival and biochemical physiology were measured in Astacus leptodactylus broodstock that were cultured at three different photoperiods (18L:6D; 12L:12D; and 6L:18D) and three stocking densities (10, 20 and 40 individuals m?2) during non‐breeding season. Survival of crayfish was highest at 18L:6D photophase and 10 m?2 (100%) than other treatments. Survival in the high stocking density was high when combined with 18L:6D photophase, but weight gain (WG) and specific growth rate (SGR) were higher at shorter photophase and lower stocking density. Longer photophase (18L:6D) increased stress responses, characterized by increased haemolymph lactate and glucose levels. Stocking density did not affect proximate composition of crayfish; however, individuals cultured at 18L:6D photophase had higher lipid content than other photoperiod treatments. The study demonstrated that culturing A. leptodactylus at 18L:6D photophase and 10 m?2 is critical for increased survival of broodstock.  相似文献   

18.
In order to explore the effects of high temperature (HT) and light on the physiological and biochemical aspects of macroalga Ulva prolifera, we cultured this species under two temperatures (20°C: low temperature, LT; 30°C: HT) and two light intensities (80 μmol m?2 s?1: low light, LL; 400 μmol m?2 s?1: high light, HL) for 5 days. It was found that (a) compared to 20°C, the chlorophyll a (Chl a) content was increased at 30°C under LL conditions, the relative growth rate (RGR) was significantly decreased at 30°C; (b) compared to LL treatment, HL significantly increased RGR but significantly decreased Chl a content; (c) LL‐grown U. prolifera at 30°C showed the highest photosynthetic oxygen evolution rate; however, there were no significant effects of temperature and light on the relative electron transport rate; (d) superoxide dismutase activity was significantly decreased by HL, but no significant effects of temperature were observed; and (e) compared to LL, HL significantly increased the soluble sugar content at 20°C, but significantly reduced at 30°C. These results showed that the inhibitory effects of HT can be offset by HL intensity.  相似文献   

19.
The octcoral Sarcophyton glaucum has a wide Indo‐Pacific distribution and is known for its diverse content of natural products. The aim of the current study was to establish a protocol for rearing miniature cuttings of S. glaucum in a closed seawater system. In order to determine the optimal conditions for rearing, the survival, average dry weight, percentage of organic weight and development of the cuttings were monitored under different temperature, light, salinity and feeding regimes. At 26 °C, the highest dry weight was obtained, and at 20 °C, the highest percentage of organic weight. The dry weight of the cuttings increased with the light intensity, while under 35–130 μE m?2 s?1, survival was high. Salinity did not affect any of the colonies' features. Feeding intervals of 7 and 30 days yielded a better result than of 2 days. A comparison of the colonies derived from the closed system with the colonies reared in a flow‐through system, those reared in the sea and with field‐collected colonies revealed the importance of environmental conditions in determining the features of the colonies. The study emphasizes the advantages of a closed seawater system in controlling the conditions needed for rearing cuttings of S. glaucum for targeted farming.  相似文献   

20.
The effects of temperature, salinity, light intensity and pH on the growth and morphology of Chattonella marina (Subrahmanyan) Hara & Chihara were examined. Optimal growth was observed at temperatures of 20-25°C, salinities of 20-30%o, light intensities of 60-140 μE m?2 s_1 and pH 7.5-8.5. Growth did not occur at temperatures below 15°C or above 30°C, and at salinities below 10%o. The morphology (shape) of the cells was strongly affected by temperature. At 20°C and 25°C, the population occurred mostly in a spindle-like form, whereas at 10°C, 90% of the cells became spherical within 10 days of inoculation and stationary phase cultures consisted entirely of spherical cells. Morphology was also markedly affected at 30°C. The number of spindle-like cells was highest at 20-30%o and was less at lower salinities. Light intensity and pH did not influence morphology markedly under the range of light intensities (20-180 μE m ?2 s-?1) and pH (6.5-8.5) tested.  相似文献   

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