Influence of light intensity on feeding, growth, and early survival of leopard coral grouper (Plectropomus leopardus) larvae under mass-scale rearing conditions

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.     

Effects of light intensity on growth,feeding activity and development in common sole (Solea solea L.) larvae in relation to sensory organ ontogeny

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.     

光照强度对紫海胆浮游幼体生长及消化酶活性的影响

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。     

The effect of light intensity on performance of larval pike-perch (Sander lucioperca)

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.     

Light intensity effects on early life stages of black sea bass, Centropristis striata (Linnaeus 1758)

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.     

Rearing temperature affects Senegalese sole (Solea senegalensis) larvae protein metabolic capacity

The present work examined the short- and long-term effects of three rearing temperatures on protein metabolism and growth trajectories of Senegalese sole larvae using ¹⁴C-labelled Artemia protein as feed. A first feeding trial was performed on larvae reared at 15, 18 and 21 °C (at 26, 17 and 14 days post-hatching (dph), respectively) and a second trial conducted on post-larvae after transfer to the same rearing temperature (~20 °C) (49, 35 and 27 dph, in larvae initially reared at 15, 18 and 21 °C, respectively). Temperature greatly influenced larvae relative growth rate (RGR) and survival, since growth at 15 °C was severely depressed. Protein digestibility and retention was highest at 18 °C during the first trial (85.35 ± 1.16 and 86.34 ± 2.33 %, respectively). However, during the second trial, post-larvae from 15 °C had the highest feed intake and protein digestibility (3.58 ± 1.54 and 75.50 ± 1.35 %, respectively), although retention was similar between treatments. Furthermore, after transfer to 20 °C larvae from 15 °C experienced compensatory growth, which was observed until 121 dph, and confirmed by RGR values, which were significantly higher at 15 ºC than at 21 ºC or 18 ºC. Results from the present study show that Solea senegalensis larval development, survival and protein digestion and retention are highly affected by thermal history.     

Growth and Survival of Larval Red Sea Bream Pagrus major and Japanese Flounder Paralichthys olivaceus Fed Microbound Diets

To establish the practical use of microbound diets (MBD) for larval fish in mass seedling production, rearing experiments of larval red sea bream, Pagrus major , and Japanese flounder, Paralichthys olivaeeus , were conducted. A mixture of various protein sources was used, and dietary amino acid patterns were approximated to those of larval whole body protein. Two thousand red sea bream larvae and 1,000 Japanese flounder larvae, all 10 days old, were placed in 100 liter tanks with running sea water under ambient water temperature, which ranged from 18 to 20C. The particle size of MBD was 125 μm at the beginning of the experiment and adjusted as fish size increased thereafter. Employing MBD together with a small amount of live food could sustain the growth and survival of larval red sea bream and Japanese flounder. Thus, data from the present study indicates that substitution of artificial feeds for live foods is possible for larval fish production, although improvements in MBD diets may be necessary before they are adequate for large scale seedling production.     

Effects of light intensity on larval development and juvenile growth of sea cucumber Apostichopus japonicus

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.     

Self-grading of larval pike-perch (Sander lucioperca), triggered by positive phototaxis

The phototactic behavior of pike-perch (Sander lucioperca) larvae from 1 to 50 days post hatch (dph) was evaluated using a channel system with 0 and 700 lx light treatment. The findings of this work show larval pike-perch to be highly positive phototactic during its larval stage with a peak of positive phototactic behavior between 10 and 22 dph. After 22 dph positive phototaxis decreased and pike-perch increasingly preferred the lower light treatment. In a second experiment observed positive phototaxis was used to evaluate the effectiveness of a light triggered self-grading mechanism for pike-perch larvae at 16, 22, 28 and 34 dph. The use of larvae’s positive phototaxis for a gentle self-grading was successful at 16 and 22 dph and decreased the length variability between 14 and 18% at 16 dph and between 18 and 28% at 22 dph. Whereas the grading at 28 and 34 dph led to an insufficient reduction in length heterogeneity. As a result the light triggered self-grading has the potential to be implemented in future rearing protocols and to be applied on pike-perch between 16 to 22 dph. Furthermore, it is suggested to consider a light triggered self-grading mechanism within upcoming tank designs for the rearing of larval pike-perch.     

Vitellus utilization under concurrent variations in temperature and light intensity in Ussuri catfish,Pseudobagrus ussuriensis

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.     

The use of preserved copepods in sea bream small‐scale culture: biometric,biochemical and molecular implications

Considering the well‐known problems arising from the use of rotifers and Artemia as live prey in larval rearing in terms of fatty acid deficiencies, the aim of this study was to evaluate a partial or complete replacement of traditional live prey with preserved copepods during the larviculture of gilthead sea bream (Sparus aurata). Sea bream larvae were randomly divided into 4 experimental groups in triplicates: group A larvae (control) fed rotifers followed by Artemia nauplii; group B fed a combined diet (50%) of rotifers–Artemia and preserved copepods; group C fed rotifers followed by preserved copepods; and group D fed preserved copepods solely. Survival and biometric data were analysed together with major molecular biomarkers involved in growth, lipid metabolism and appetite. Moreover, fatty acid content of prey and larvae was also analysed. At the end of 40 days treatment, a stress test, on the remaining larvae, was performed to evaluate the effects of different diets on stress response. Data obtained evidenced a positive effect of cofeeding preserved copepods during sea bream larviculture. Higher survival and growth were achieved in group B (fed combined diet) larvae respect to control. In addition, preserved copepods cofeeding was able to positively modulate genes involved in fish growth, lipid metabolism, stress response and appetite regulation.     

Effects of culture conditions on feeding response of larval Pacific red snapper ( Lutjanus peru, Nichols & Murphy) at first feeding

Feeding incidence or number of larvae with preys (FIC) and intensity or number of prey per larvae (FIT) at first feeding of Pacific red snapper ( Lutjanus peru) larvae was investigated under different conditions: prey type (rotifer and copepod nauplius) and density, nauplii size, light intensity, water temperature, salinity and microalgae concentration. Rotifers were not consumed at any prey density and FIC increased significantly when a high nauplii density (10 > 1, 0.1 mL^?1) and light intensity (2000 > 1000, 500, 0 lx) were supplied. In a multifactorial experiment where light intensity (2000, 2500, 3000 lx), tank colour (grey and black) and prey type (nauplii and a mixed diet: rotifers and nauplii) were tested, a significant difference was found only for light intensity and prey type with a significant interaction between these factors. FIC was significantly higher with nauplii stage I–III than IV–VI and also at 25 °C than at 28 °C. Green water (0, 0.3 × 10⁶ or 1 × 10⁶ cells mL^?1) and salinity (25, 30, 35 gL^?1) did not affect FIC. FIT was not affected by any variables tested except in the density experiment where it was significantly higher at 10 nauplii mL^?1.     

Early-weaning diets for gilthead sea bream (Sparus aurata L.) and their potential use in Hellenic marine fish hatcheries

The purpose of this experiment has been to evaluate the suitability of commercially available early-weaning microdiets (MDs) for the production of sea bream early juveniles and in comparison with late-weaning protocols already in use by Hellenic marine fish hatcheries. Four sea bream experimental groups were allocated in rearing tanks of a commercial Hellenic marine fish hatchery. Each group represented a different protocol (A, B, CA, and CB) based on the combination of two different early-weaning MDs (A and B) and a late-weaning diet (C). In addition, the late-weaning protocols have received Artemia instar II only and not Artemia instar I. In protocol A, Artemia instar I first feeding and the early-weaning diet A were administered at 17 days post-hatch (17 dph). In protocol B, Artemia instar I first feeding started at 15 dph and the early-weaning diet B was administered at 18 dph. In the C protocols, Artemia instar II first feeding started at 20 dph and the early-weaning diets (A or B) were administered at 25 dph. All protocols have received the late-weaning diet C only after the 50th dph. The experiment lasted for 65 days. By the end of the experiment, early-weaning protocol A and late-weaning protocol CB had similar wet weights, but still lower to the wet weights recorded for the late-weaning protocol CA. These results cannot be explained solely by the nutritional profile of each weaning diet. The larval fatty acid profile of each protocol and at various time intervals reveals the importance that the succession of Artemia, rotifers, and MDs has for each protocol and not just the nutritional profile of the weaning diets, per se.     

Swimbladder inflation,growth and survival of yellowtail kingfish Seriola lalandi (Valenciennes, 1833) larvae under different temperature,light and oxygen conditions

Poor swimbladder inflation leads to low fish survival due to resulting spinal deformities and the inability to feed and develop normally. Failure of swimbladder inflation may be attributed to the inappropriate range of abiotic conditions. This study investigated the effects of temperature, light source and intensity, and oxygen conditions on initial swimbladder inflation, growth and survival of yellowtail kingfish Seriola lalandi larvae. The study consisted of four separate trials including low (21.5°C) and high (24.5°C) temperatures, natural and artificial light sources, low (1000 lux) and high (32 000 lux) light intensities, and ambient and supersaturated dissolved oxygen. Initial swimbladder inflation was only significantly affected by light source, with the highest inflation rate (97.5 ± 3.5%) under artificial light. Fish growth was improved at the higher temperature and at the higher light intensity. Survival was only significantly influenced by light intensity, with the highest survival (11.0 ± 2.3%) at the high intensity (32 000 lux). This study indicates that light source affects swimbladder inflation timing and high artificial light intensity improves larval fish growth and survival.     

Visual thresholds for feeding and optimum light intensity for larval rearing of Asian seabass,Lates calcarifer (Bloch)

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.     

Effects of photoperiod and night‐time aeration rate on swim bladder inflation and survival in Pacific bluefin tuna,Thunnus orientalis (Temminck & Schlegel), larvae

Success of swim bladder inflation (SBI) is crucial for early survival of Pacific bluefin tuna (PBF) larvae, because it reduces larval sinking death by enhancing buoyancy. In Experiment 1, we examined the effect of photoperiod on SBI and survival in PBF larvae by comparing photoperiods of 9L: 15D (9L), 14L: 10D (14L: natural photoperiod), 19L: 5D (19L) and 24L: 0D (24L) during 2–10 days post hatch (dph). In Experiment 2, the combined effects of photoperiod (24L and 14L) and nighttime aeration rate (enhanced night‐time aeration: ENA of 1300 mL min^?1 as a countermeasure for sinking death and 130 mL min^?1) on the survival and SBI were also examined during 2–10 dph. Moreover, in Experiment 3 the effect of photoperiod on vertical distribution of larvae in night‐time was examined on 3–5 dph. Photoperiod of 24L in Experiment 1 significantly inhibited SBI compared with 14L and 19L; nevertheless, it significantly improved survival compared with other photoperiods with a dark period. On the other hand, the shortened light period (9L) showed significantly reduced SBI and also survival. In Experiment 2, the countermeasure for sinking death of ENA under 24L did not further improve the survival; rather it tended to reduce the survival. In Experiment 3, larvae distributed less in the bottom layer in 24L than in 14L, suggesting the reducing effect of 24L on sinking death. The results indicate that 24L without ENA is suitable for survival which is the most serious problem in PBF larviculture.     

Ontogeny of anti-predator behavior in hatchery-reared jack mackerel Trachurus japonicus larvae and juveniles: patchiness formation, swimming capability, and interaction with jellyfish

ABSTRACT:   Laboratory rearing and behavioral observations of larval and juvenile jack mackerel Trachurus japonicus were conducted to elucidate their life-history traits with emphasis on the interaction with the moon jellyfish Aurelia aurita . Jack mackerel were raised from naturally spawned fertilized eggs and they attained 10.3 ± 0.7 (mean ± standard deviation) mm in body length (BL) by 30 days post hatching (dph) and 26.6 ± 1.8 mm BL at 48 dph raised at 19.3–25.0°C. Patchiness (dense aggregation) was confirmed from 5–16 dph (2.9–5.9 mm BL) during the day and from 9–48 dph (4.0–27 mm BL) at night. Cruise and burst swimming speeds were 1.5–1.9 BL/s and 16–24 BL/s, respectively, during larval and juvenile stages, in experimental tanks. Although escape performance from jellyfish was not different between the larvae of jack mackerel and chub mackerel Scomber japonicus , both species showed better survival compared to red sea bream Pagrus major larvae of a similar size. Although jack mackerel were slow in growth, their slow cruise swimming may reduce the chance of encountering predators and fast burst swimming may help escape from gelatinous predators.     

The effect of live feeds bathed with the red seaweed <Emphasis Type="Italic">Asparagopsis armata</Emphasis> on the survival,growth and physiology status of <Emphasis Type="Italic">Sparus aurata</Emphasis> larvae

Larval rearing is affected by a wide range of microorganisms that thrive in larviculture systems. Some seaweed species have metabolites capable of reducing the bacterial load. However, no studies have yet tested whether including seaweed metabolites on larval rearing systems has any effects on the larvae development. This work assessed the development of Sparus aurata larvae fed preys treated with an Asparagopsis armata product. Live prey, Brachionus spp. and Artemia sp., were immersed in a solution containing 0.5% of a commercial extract of A. armata (Ysaline 100, YSA) for 30 min, before being fed to seabream larvae (n = 4 each). In the control, the live feed was immersed in clear water. Larval parameters such as growth, survival, digestive capacity (structural-histology and functional-enzymatic activity), stress level (cortisol content), non-specific immune response (lysozyme activity), anti-bacterial activity (disc-diffusion assay) and microbiota quantification (fish larvae gut and rearing water) were monitored. Fish larvae digestive capacity, stress level and non-specific immune response were not affected by the use of YSA. The number of Vibrionaceae was significantly reduced both in water and larval gut when using YSA. Growth was enhanced for YSA treatment, but higher mortality was also observed, especially until 10 days after hatching (DAH). The mortality peak observed at 8 DAH for both treatments, but higher for YSA, indicates larval higher susceptibility at this development stage, suggesting that lower concentrations of YSA should be used until 10 DAH. The application of YSA after 10 DAH onwards promotes a safer rearing environment.     

Influence of temperature and feeding regimes on growth and notochord deformity in reared <Emphasis Type="Italic">Anguilla japonica</Emphasis> leptocephali

The high mortality rate of reared Japanese eel Anguilla japonica larvae is largely due to lower growth rate and the higher rate of deformed larvae. To establish an effective rearing protocol for this species, we examined the effects of water temperature and feeding regimes on their growth and notochord kyphosis. Larvae at 165 days post hatching were reared for 28 days at mean temperatures of 24, 25 and 27 °C, and were fed 4 or 6 times per day. Larval growth rate was significantly higher in larvae reared at 24–25 °C and fed 6 times per day. However, growth rate was significantly reduced at 27 °C, suggesting a shortage of metabolic energy due to an elevated cost of the higher basal metabolic rate at higher temperatures and low nutritional performance of currently used artificial diet. Notochord kyphosis was promoted by elevated water temperature, and two-way ANOVA showed that water temperature and feeding frequency had combined effects on the deformity. These findings suggest the importance of concurrently manipulating both environmental and nutritional factors to produce healthy eel larvae in captivity.     

Comparison of Two Environmental Regimes for Culture of Australian Snapper, Pagrus auratus, Larvae in Commercial-scale Tanks

The performance of Australian snapper, Pagrus auratus, larvae from 4 to 33 days posthatch (dph) under two environmental rearing regimes was evaluated in 2000‐L commercial‐scale larval rearing tanks (N = 3 tanks/treatment). The treatments were the following: (1) a varying regime of salinity (20–35 ppt), temperature (24 C), and photoperiod (12 light [L] : 12 dark [D] to swim bladder inflation and then 18L : 06D) and (2) a constant regime of salinity (35 ppt), temperature (21 C), and photoperiod (14L : 10D). The final total length (TL) and wet and dry weights (mean ± SEM) of larvae grown in the varying regime were greater (15.6 ± 0.5 mm; 42.4 ± 3.4 mg wet weight; and 7.3 ± 0.6 mg dry weight) than those of larvae grown in the constant regime (11.1 ± 0.2 mm; 12.9 ± 0.8 mg wet weight; and 2.1 ± 0.2 mg dry weight). By 33 dph, larvae in the varying regime were fully weaned from live feeds to a formulated pellet diet and were suitable for transfer from the hatchery to a nursery facility. In contrast, larvae in the constant regime were not weaned onto a pellet diet and still required live feeds. Neither survival (Treatment 1, 14.2 ± 3.0% and Treatment 2, 13.3 ± 1.9%) nor swim bladder inflation (Treatment 1, 70.0 ± 17.3% and Treatment 2, 70.0 ± 11.5%, by 13 dph) was affected by rearing regime. The incidence of urinary calculi at 7 dph was greatest initially in the varying regime; however, by 19 dph, when larvae were 8.0 ± 0.28 mm TL, very few larvae in this treatment had urinary calculi. In contrast, many larvae in the constant regime had developed urinary calculi and this continued until the end of the experiment. The incidence of urinary calculi was not associated with larval mortality. Extrapolation of the snapper larval growth curves for the constant larval rearing regime predicts that a further 15–18 d, or approximately 1.5 times longer, will be required until these larvae attain the same size and development of larvae reared in the varying regime.