The giant freshwater prawn Macrobrachium rosenbergii alters background colour preference after metamorphosis from larvae to postlarvae: In association with nature of phototaxis

The giant freshwater prawn Macrobrachium rosenbergii larvae have apposition eyes and are positively phototactic, whereas the postlarvae (PL) have superposition eyes and are negatively phototactic. M. rosenbergii has colour vision as early as larval stage. We discovered that M. rosenbergii alters background colour preference after metamorphosis from larvae to PL in association with nature of phototaxis. The test circular glass aquaria covered with a pair of two‐colour papers contained with a group of 100 larvae or 20 Pl, and the number of individuals in each colour background was recorded five times for each colour pair. The background colours tested were light blue, green, yellow, red, white and black. The numbers of larvae or PL in each colour background of different pairs were analysed by the Thurstone's law of comparative judgment. In the larvae, significant bias towards yellow was evident. In the PL, of the four pairings of black with other colours, all biased to black. The mean z‐scores were highest for yellow in the larvae, and for black in the PL. To determine the possible background brightness preference of the larvae and PL, six different colour backgrounds were presented in pairs. The larvae significantly preferred light blue over dark blue, white over yellow and white over black. The PL exhibited reversed preference. The relationship between z‐scores and light reflectance levels of five colour papers was significantly positive in the larvae and negative in the PL. The observed background colour preference was probably due to relative brightness rather than chromaticity difference.     

Development of phototaxis in the early life stages of Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis>

We investigated the development of phototaxis in larval and early juvenile stages of Pacific bluefin tuna Thunnus orientalis to detail behavior development in relation to light. We observed the distribution of Pacific bluefin tuna in an illumination gradient tank from 1 to 26 days after hatching (DAH). Two long rectangular tanks (100 × 10 × 10 cm) were used for experiments; each tank was divided into four sections for observations and one tank was equally illuminated at 1.0 × 10³ lx as the control tank, and the other was at 4.0 × 10², 1.0 × 10³, 1.0 × 10⁴ and 7.0 × 10⁴ lx as the illumination gradient tank. Laboratory-reared larvae and juvenile were released into each tank and acclimatized for 10 min. Thereafter, the number of individuals in each section was counted for 5 times with 10-min intervals. Until 2 DAH (3.6 ± 0.1 mm BL), larvae distributed homogeneously in each section in both tanks. After 3 DAH (3.7 ± 0.1 mm BL) when the eyes of the larvae were pigmented, most fish moved into the 7.0 × 10⁴ lx section in the illumination gradient tank, while fish in the control tank maintained a uniform distribution during the experimental period (Chi-square test, P < 0.05). The results suggest that the post-larvae and juvenile stages show strong positive phototaxis.     

Improved hatchery‐rearing techniques for juvenile production of blue swimming crab,Portunus pelagicus (Linnaeus, 1758)

The effects of tank colour, larval stocking density, antibiotic administration and water exchange on survival and moulting of blue swimming crab, Portunus pelagicus, were determined. Circular 4‐m³ experimental larval‐rearing tanks were used in triplicate for all treatments. White, dark grey, blue and brown were tested as tank background colours. The stocking densities tested were 10, 20, 40, 60, 80 and 100 larvae L^?1. The effect of oxytetracycline was estimated by comparing a treatment with oxytetracycline to a treatment without oxytetracycline administration. The daily water exchange rates tested were 0%, 25%, 50% and 100% of the tank volume. In all treatments, the larvae were fed with Artemia nauplii, rotifers and encapsulated Spirulina. The highest percentage survival was observed in the dark‐grey tanks when the stocking density of larvae was 20 larvae L^?1. No larva reached the juvenile crab size in white tanks. No significant difference in survival was found between treated and non‐treated larvae with oxytetracycline when the daily water exchange rate was more than 50%.     

Effect of tank colour on larval performance of the Amazon River prawn Macrobrachium amazonicum

The aim of this study was to evaluate the effects of hatchery‐tank colours (white, yellow, red, blue, green and black) on the performance of larval culture of Macrobrachium amazonicum. The larvae were fed daily with newly hatched Artemia nauplii. The hatchery‐tank colours affected the light level inside the tanks, the consumption of Artemia nauplii (AN), larval development, survival, mass gain and productivity of postlarvae (PL). The overall consumption of Artemia nauplii per larva during the larval cycle was 30% and 45% higher in the green and red tanks respectively. The significant variation of AN consumption among tank colours (P = 0.0006) indicates that M. amazonicum larvae are visual predators. Survival was higher in the black, blue and green tanks, reaching more than 75%. However, the highest productivity was obtained in the black tanks (80.1 PL L^?1). Lighter coloured tanks and excess luminosity (more than 2 μmol s^?1 m² at tank bottom) appear to be important stress factors for larvae, contributing to reduce survival and productivity. The results indicate that rearing M. amazonicum in black tanks will improve larvae condition, ensure greater productivity of postlarvae and lower Artemia consumption, increasing technological and economic viability.     

The plasticity of vision and body development of turbot Scophthalmus maximus larvae Under different light spectra

This study was aimed to find out the effect of five light spectra (white, LDW; blue, LDB; green, LDG; red, LDR and yellow, LDY) on the visual development and growth performance of turbot (Scophthalmus maximus) larvae. The number (per 100 μm) of cone cells, outer nuclear cells, ganglion cells, the ratio of outer nuclear to cone and ganglion cells, lens diameter and the minimum separable angle were determined. Variations in growth performance in total length, body mass and body colour were also examined. The results showed that the LDB group underwent metamorphosis faster than did the other groups and attained the greatest total length, body mass and light sensitivity. The LDB group also completed the body colour variation prior to the other groups. The LDG group exhibited a high mortality rate since 25 dph (days post‐hatching). We arrived at the conclusions that the spectra could affect the vision and body development of turbot larvae specifically and the blue light had the enhancing efficiency during this process, followed by the white and yellow light. The red light imposed an inhibiting effect on these variations. Our study highlighted the significance of light condition and provided the reference for the farming.     

Effects of tank color on the growth,stress responses,and skin color of snakeskin gourami (<Emphasis Type="Italic">Trichogaster pectoralis</Emphasis>)

The effects of tank color on the growth, stress responses, and skin color of snakeskin gourami (Trichogaster pectoralis) were investigated in this study. Fish with initial body weights of 5.03±0.00 g were reared in five experimental tank colors (white, red, green, blue, and black) for 8 weeks. Each tank color was tested in triplicate with an initial stocking density of 15 fish per tank. Fish were fed with commercial sinking pellets at 4% of the average body weight per day. Growth performance, feed utilization efficiency, stress indicators (hematocrit, blood glucose, plasma cortisol levels), and skin color parameters were investigated. The fish reared in blue tanks had a significantly higher average final body weight (9.73?±?0.14 g) and significantly lower average feed conversion ratio (3.42?±?0.12) than the fish reared in black tanks (P?<?0.05). The fish reared in black tanks exhibited higher average hematocrit (36.63?±?1.11%), blood glucose (48.33?±?1.45 mg dL^?1), and plasma cortisol (9.00?±?0.56 μg dL^?1) levels than those reared in the other tank colors. However, the blood glucose levels in only the fish reared in black tanks were significantly higher than those in the fish reared in the other tank colors. The fish skin color ranged from very pale (high skin lightness) in the white tanks to very dark (low skin lightness) in the black tanks, and 80% of the variation in skin lightness were explained by the tank lightness. The use of a blue tank resulted in normal skin color; hence, blue tanks will not affect the customer acceptance of the fish. Our study revealed that blue is the most appropriate tank color for culturing snakeskin gourami.     

Growth,development and survival of European sea bass (Dicentrarchus labrax) larvae cultured under different light spectra and intensities

We assessed the effects of light intensity and spectrum on the growth, development and survival of Dicentrarchus labrax larvae from 30 to 96 days after hatching. Twelve lighting regimes were applied using 0.3, 1 and 2 W/m² full spectrum white, blue, red and green light. By day 66 of exposure, growth performance was significantly better in larvae reared under green or red light compared with white or blue light (p < 0.05), while it was significantly better at 2.0 W/m² compared with 1.0 or 0.3 W/m² (p < 0.05). Larvae reared under white or blue light had significantly more deformities (p < 0.05) than did larvae reared under light of other spectra, while larvae reared under 0.3 W/m² light intensity had a significantly higher proportion of jaw malformations than reared under 1.0 and 2.0 W/m² (p ? 0.05). Dicentrarchus labrax larvae subjected to green light showed significantly lower survival compared with the other light spectra (p < 0.05). Moreover, light significantly affected brain aanat1a, aanatt1b, mellc, mt1, mt2, gh, tsh and crf mRNA expression. Therefore, the red and green light groups (or under 2.0 W/m²) could improve the growth performance and enhance secretion of melatonin, gh and tsh, and reduce the proportion of jaw malformations.     

Effects of tank colour and feed colour on growth and feed utilization of thinlip mullet (Liza ramada) larvae

The effects of aquarium background colour and feed colour on survival, growth rates and feed utilization efficiency of thinlip mullet (Liza ramada) larvae (0.035 g) were investigated in two experiments. In the aquarium background colour trial, 50 larvae were stocked in duplicates in 120 L glass aquaria filled with dechlorinated tap water. The outside walls and bottoms of each pair of the aquaria were covered with coloured paper sheets to achieve one of six colours (white, black, red, green, yellow and blue), while noncoloured aquaria served as a control. The fish were fed an experimental diet (35% crude protein) at a daily rate of 5% of their body weight (BW), twice a day for 8 weeks. The best growth rates, feed efficiency and survival were achieved in larvae reared in light‐coloured aquaria (white, noncoloured and yellow). Fish performance was significantly retarded in larvae reared in dark‐coloured aquaria (red, green, black and blue). Body composition was not significantly affected by aquarium colour. In a feed colour trial, duplicate groups of larvae (0.035 g) were stocked at 50 fish per 120 L aquarium and fed a test diet (35% crude protein) with six different colours [dark blue, red, yellow, light brown (control), light green and dark brown] at a daily rate of 5% BW, twice a day for 8 weeks. The best performance and survival were achieved in fish fed on dark‐coloured diets (red, dark blue and dark brown). Light‐coloured diets (yellow, light green and light brown) resulted in inferior performance. Body composition was not significantly affected by feed colour. These results suggest that light‐coloured tanks should be used for rearing thinlip mullet, L. ramada larvae, while dark‐coloured diets are more preferable to light‐coloured diets.     

Combined effects of rearing density and tank colour on the growth and welfare of juvenile white sea bream Diplodus sargus L. in a recirculating water system

Appropriate rearing conditions for successful farming of white sea bream Diplodus sargus L. have not yet been studied in depth, while one of the major problems is the species increased aggressiveness. Given the known effect of density and background colour on fish growth, welfare and social behaviour, the present study aimed to investigate whether the two factors combined could favour D. sargus performance. Juveniles (17.37±0.06 g) were reared in white, light blue and black tanks under low (7 fish tank⁻¹ or 1.96 kg m⁻³) and high (28 fish tank⁻¹ or 7.79 kg m⁻³) density for 87 days. Water quality was not affected by experimental treatments. The best overall performance (growth, food utilization, body protein content, liver fatty acids) was achieved under low density and white or light blue tanks. Increased incidence of social interactions was indicated in fish under high density or when reared in light blue and black tanks. The present results clearly suggested that the use of black tanks should be avoided. On the other hand, stocking D. sargus at a density of up to 7.79 kg m⁻³ may be feasible because productivity was greater even if growth was slower. In this case, however, the use of white tanks is highly recommended.     

Effects of light spectrum and intensity on growth,survival and physiology of leech (Whitmania pigra) larvae under the rearing conditions

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).     

The effects of the tank colour on growth performance and physiological responses in fingerling grouper,Epinephelus coioides

In this study, the effects of different background colours on growth performance and physiological parameters of Epinephelus coioides were investigated. One hundred eighty E. coioides (average weight 18.16 ± 0.07 g) were distributed in black, white and blue 300‐L tanks and fed to satiation for 60 days. The tank colour had no significant effect on the weight gain, condition factor, hepatosomatic index and specific growth rate (p > .05). The lowest amount of viscerosomatic index and the highest carcass protein were recorded in the white tank (p < .05). Daily food intake, feed conversion ratio and plasma glucose were significantly higher in the blue tank (p < .05). The highest levels of haematocrit and plasma triglyceride were observed in the white tank, while the total protein and albumin were higher in the black tank compared to the other tanks. The tank colour had no significant effects on the plasma cortisol level (p > .05). Our findings showed that colours used in this study did not evoke stress and thus had no effect on growth, but some metabolic adaptation occurred in each colour to achieve optimum growth.     

Impact of spectral composition on larval haddock,Melanogrammus aeglefinus L., growth and survival

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.     

Optimum culture conditions of <Emphasis Type="Italic">Rhodomonas</Emphasis> sp. Hf-1 strain as a live food for aquatic animals

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.     

The effect of photoperiod, tank colour and light intensity on growth of larval haddock

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.     

Growth performance and survival of giant freshwater prawn Macrobrachium rosenbergii larvae fed coloured feed

This study examined the behavioural response on the preference and acceptance, growth performance and survival of Marcobrachium rosenbergi larvae fed with isonitrogenous and isolipidic yellow (YCF) and blue (BCF) coloured feed. In the behavioural response test, single and paired feed drop test of YCF and BCF were introduced at the middle of a tank about 15–20 cm from the edge of the white colour tank wall to larvae zoea IV–VI. The number of larvae attracted to each coloured feed was recorded. For the growth and survival performance, each coloured feed was fed to triplicate groups of larvae (zoea V–VI) at stocking density of 30 larvae/L in 12 ppt brackish water for 28 days until they reached postlarval (PL) stage. In the behavioural test, the number of larvae that attracted and accepted the BCF was significantly higher than those fed YCF (p < 0.05). The body weight and length of PL fed BCF was 28% and 5.6% bigger than those fed YCF respectively. However, the survival of the PL was almost similar in both treatments. This study shows that the freshwater prawn larvae were attracted more to the BCF and able to detect and capture the preferred BCF by vision and this contributed to higher growth of the larvae.     

The effect of tank colouration on survival, metamorphosis rate, growth and time to metamorphosis freshwater prawn (Macrobrachium rosenbergii) rearing

Seedstock‐costs of the freshwater prawn Macrobrachium rosenbergii can represent >50% of the total production costs. The purpose of this study was to evaluate the effect of culture tank colouration on survival, metamorphosis rate, weight and time required to reach the postlarval (PL) stage. Newly hatched prawn larvae were stocked into eighteen 16‐L plastic culture tanks at a density of 30 L^?1. Tank colours evaluated were red, black, white, blue, green and yellow. Larval prawns were fed brine shrimp (Artemia franciscana) nauplii and a supplemental diet. Data indicated that larval tank colour had no significant impact (P>0.05) on the final PL size or days required to reach PL stage. However, total survival was significantly higher (P<0.05) in red and green tanks (84% and 78% respectively) than in white and blue tanks (56% and 44% respectively). Survival in the yellow and black tanks (71% in both) was not significantly different (P>0.05) from the red, green or white treatments, but was significantly higher (P<0.05) than the blue treatment. This could have a significant financial impact on commercial hatchery, and growout production, as most larval tanks currently in use are blue or black.     

Dim-light photoreceptor of chub mackerel <Emphasis Type="Italic">Scomber japonicus</Emphasis> and the photoresponse upon illumination with LEDs of different wavelengths

To study the absorption characteristics of rhodopsin, a dim-light photoreceptor, in chub mackerel (Scomber japonicus) and the relationship between light wavelengths on the photoresponse, the rod opsin gene was cloned into an expression vector, pMT4. Recombinant opsin was transiently expressed in COS-1 cells and reconstituted with 11-cis-retinal. Cells containing the regenerated rhodopsin were solubilized and subjected to UV/Vis spectroscopic analysis in the dark and upon illumination. Difference spectra from the lysates indicated an absorption maximum of mackerel rhodopsin around 500 nm. Four types of light-emitting diode (LED) modules with different wavelengths (red, peak 627 nm; cyan, 505 nm; blue, 442 nm; white, 447 + 560 nm) were constructed to examine their effects on the photoresponse in chub mackerel. Behavioral responses of the mackerels, including speed and frequencies acclimated in the dark and upon LED illumination, were analyzed using an underwater acoustic camera. Compared to an average speed of 22.25 ± 1.57 cm/s of mackerel movement in the dark, speed increased to 22.97 ± 0.29, 24.66 ± 1.06, 26.28 ± 2.28, and 25.19 ± 1.91 cm/s upon exposure to red, blue, cyan, and white LEDs, respectively. There were increases of 103.48 ± 1.58, 109.37 ± 5.29, 118.48 ± 10.82, and 109.43 ± 3.92 %, respectively, in the relative speed of the fishes upon illumination with red, blue, cyan, and white LEDs compared with that in the dark (set at 100 %). Similar rate of wavelength-dependent responses was observed in a frequency analysis. These results indicate that an LED emitting a peak wavelength close to an absorption maximum of rhodopsin is more effective at eliciting a response to light.     

Effects of light intensity, tank colour and photoperiod on swimbladder inflation success in larval striped bass, Morone saxatilis (Walbaum)

Striped bass, Morone saxatilis (Walbaum), larvae, although physoclistous as adults, initially need to inflate their swimbladders by passing ingested air through a pneumatic duct to the swimbladder. Failure to inflate the swimbladder results in swimbladder atrophy, dysfunctional buoyancy control, deformities, and poor larval survival and growth. The present investigation studied the effects of light intensity, tank colour and photoperiod on the initial swimbladder inflation success of striped bass. In the first experiment, newly hatched larvae were reared for 2 weeks in black or white 350-L circular tanks exposed to incandescent lighting at 163 or 10 lux. Larvae were fed Artemia from 6 days post-hatching (dph). The standard length, and oil globule and yolk areas were measured. Swimbladder condition and evidence of feeding were recorded. To study the effects of photoperiod on inflation, larvae were reared in black tanks exposed to either 8 h:16 h or 16 h:8 h light:dark photoperiods at 139 lux. Striped bass inflated their swimbladders between 6 and 9 dph at 17 ^oC. Inflation success was significantly higher in black tanks (65%) compared with white tanks (42%), but light intensity did not significantly affect swimbladder inflation. Larval growth and food consumption were better in black tanks, primarily because this treatment resulted in more larvae with inflated swimbladders, although larvae with uninflated swimbladders in black tanks were longer at 12 dph than larvae with inflated swimbladders in white tanks. Larvae that successfully inflated their swimbladders fed earlier and exhibited better growth than larvae with noninflated swimbladders. Larvae reared at higher light intensities used up yolk reserves faster. Exposing striped bass larvae to 8 h:16 h light:dark photoperiods resulted in higher inflation rates (55%) compared to larvae reared at 16 h:8 h light:dark photoperiods (30%). Therefore, black tanks and short photoperiods are preferable for early rearing of striped bass larvae to maximize swimbladder inflation success.     

Effects of LED light quality on the growth,survival and metamorphosis of Haliotis discus hannai Ino larvae

Light is a key environmental factor influencing the growth, development and survival of aquatic organisms. We examined the effects of different light qualities (red, orange, white, blue, green or no light) and developmental stage at initial lighting [fertilized egg (FE), trochophore larva (TL), or eye‐spot larva (EL)] on the growth, development, and survival of larvae of the Pacific abalone Haliotis discus hannai Ino. Larva‐hatching success was significantly higher under blue, green, or no light compared with red, orange or white light (P < 0.05). Larval abnormalities were significantly increased under red, orange or white light compared with all other light qualities (P < 0.05). The incidence of metamorphosis in larvae illuminated from the TL stage was significantly higher under blue compared with other light qualities. Irrespective of the stage at initial illumination, the incidence of metamorphosis was lower in larvae cultured under red, orange or no light compared with other light qualities, but the differences were not significant (P > 0.05). Juvenile survival was significantly higher under blue or green compared with other light qualities (P < 0.05), with no significant effect of stage at initial illumination (P > 0.05). Larval size at completion of the shell was unaffected by stage at initial illumination, but was greater under blue or green light, while size at metamorphosis was greatest following illumination with blue or green light since the TL or EL stage (P < 0.05). Metamorphosis time was shortest with blue or green light and in cultures illuminated from the FE or TL stage (P < 0.05). Larval development from the FE to formation of the fourth tubule on the cephalic tentacles was fastest in larvae exposed since the FE or TL stage to blue or green light, compared with other light qualities (P < 0.05). However, there was no difference in terms of the rate of development from the FE to the TL stage between cultures lit or unlit since the FE egg stage (P > 0.05). These results suggest that a blue or green light source applied from the TL stage can increase the hatching and yield of H. discus hannai Ino, with important implications for the development of the aquaculture industry.     

Effect of diet and rearing conditions on growth and survival throughout developmental stages of larvae and juveniles of dusky grouper <Emphasis Type="Italic">Epinephelus marginatus</Emphasis> (Lowe 1834)

Two rearing conditions, tank light-dimensions and diet, were tested in dusky grouper—larvae and juveniles—in order to improve larval rearing techniques for this species. Larvae reared in high-volume and fluorescent tubes showed the highest survival rate at 18 dph (17.67%, 16%). This might be due to a higher depth and less trapping area during surface death in high-volume tanks than in low volume. Besides, a 500-lx evenly distributed light with fluorescent tubes might improve survival rate at early stages rather than illumination with energy-efficient light bulbs (4.68%, 9.64%). Light bulbs created shaded areas with less illumination inducing low larval activity. First feeding was performed with minimum rotifer lorica width of 102?±?10.2 μm. No mixed diet was supplied. Throughout metamorphosis, stress shock syndrome appeared to be the main cause of mortality. Diet A showed best growth and survival (4.1–7.36%) during this period probably due to its high HUFA content (9.5%). Contrary to what was observed during first stages, groupers showed best performance with lower illumination. Cannibalism was observed during this period in all culture conditions.