Productivity improvement of Lysmata seticaudata (Risso, 1816) larval rearing protocol through modelling

The Monaco shrimp Lysmata seticaudata (Risso, 1816) is a marine ornamental species whose ecology and biology, as well as its larval culture has previously been addressed. The objective of the study was to predict and improve productivity of this species rearing protocol through modelling. The models developed intend to help aquaculturists to maximize survival to postlarva, decrease larval duration and increase synchronism of metamorphosis and newly metamorphosed postlarvae size by manipulating temperature, diet, first feeding period and stocking density.The models developed allow us to conclude that the L. seticaudata rearing protocol productivity can be improved by raising larvae at a density of 40 larvae L^− 1 and fed newly hatched Artemia nauplii since hatching to zoea V, and with Algamac 2000™ enriched Artemia metanauplii from zoea V to metamorphosis to postlarvae.By providing more productive protocols to aquaculturists, destructive practices and wild collection may be reduced.     

The effect of dietary n-3 HUFA levels and DHA/EPA ratios on growth, survival and osmotic stress tolerance of Chinese mitten crab Eriocheir sinensis larvae

The effect of varying levels of dietary n-3 highly unsaturated fatty acid (HUFA) and docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) ratios on growth, survival and osmotic stress tolerance of Eriocheir sinensis zoea larvae was studied in two separate experiments. In experiment I, larvae were fed rotifers and Artemia enriched with ICES emulsions with 0, 30 and 50% total n-3 HUFA levels but with the same DHA/EPA ratio of 0.6. In experiment II, larvae were fed different combinations of enriched rotifers and Artemia, in which, rotifers were enriched with emulsions containing 30% total n-3 HUFA, but different DHA/EPA ratio of 0.6, 2 and 4; while Artemia were enriched with the same emulsions, but DHA/EPA ratio of 0.6 and 4. In both experiments, un-enriched rotifers cultured on baker's yeast and newly-hatched Artemia nauplii were used as control diets. Larvae were fed rotifers at zoea 1 and zoea 2 stages; upon reaching zoea 3 stage, Artemia was introduced.Experiment I revealed no significant effect of prey enrichment on the survival of megalopa among treatments, but higher total n-3 HUFA levels significantly enhanced larval development (larval stage index, LSI) and resulted in higher individual dry body weight of megalopa. Furthermore higher dietary n-3 HUFA levels also resulted in better tolerance to salinity stress. Experiment II indicated that at the same total n-3 HUFA level, larvae continuously receiving a low dietary DHA/EPA ratio had significantly lower survival at the megalopa stage and inferior individual body weight at the megalopa stage, but no negative effect was observed on larval development (LSI). The ability to endure salinity stress of zoea 3, zoea 5 and megalopa fed diets with higher DHA/EPA ratio was also improved.     

Bacterial flora associated with the giant freshwater prawn Macrobrachium rosenbergii, in the hatchery system

The objective of this study was to understand the microbial flora associated with the hatchery system of giant fresh water prawn, Macrobrachium rosenbergii during an entire rearing cycle. Bacteriological and physico-chemical analysis was done for different samples of water, larvae, and Artemia. The total bacterial load in well water, seawater and inlet water varied from 10¹ to 10⁵ cfu ml^− 1 with higher counts seen in larval rearing tank (LRT) water. The Vibrio count ranged between 10¹ to 10³ cfu ml^− 1. Larval samples harboured a bacterial load of 10⁶ to 10⁷ cfu/10 larvae. The bacterial load in Artemia hatching water ranged from 4.90 × 10⁴ to 5.63 × 10⁶ cfu ml^− 1 while Artemia had a load ranging from 1.08 × 10⁷ to 2.09 × 10⁹ cfu g^− 1. Vibrio count in the LRT water ranged from 10¹-10³ cfu ml^− 1 while the count in larvae ranged from 10² to 10⁴ cfu/10 larvae. The bacterial genera were predominantly Gram-negative and comprised of Aeromonas spp., Pseudomonas spp., Vibrio spp. and Bacillus spp. and non-spore formers (NSF) were the dominant Gram-positive bacteria. This study documents the bacterial flora associated with Macrobrachium hatchery system during a regular normal run. Knowledge of the qualitative and quantitative aspects of bacterial flora in the hatchery would help to understand disturbances, if any, brought about during disease outbreaks.     

Successful culture of larvae of Litopenaeus vannamei fed a microbound formulated diet exclusively from either stage PZ2 or M1 to PL1

In three separate experiments, harpaticoid copepods Tisbe monozota (alive and dead) and a microparticulate microbound diet were evaluated as alternatives to live Artemia nauplii as food, beginning at either stage PZ2 or M1, in the larval culture of Litopenaeus vannamei. Larvae were cultured in 2 L round bottom flasks at a density of 150 L^− 1 (Experiment 1) and 100 L^− 1 ( 3.2 and 3.3) at 28 °C, 35‰ salinity and 12:12 LD photoperiod, and fed 4×/day^- 1. Larvae were initially fed a mixture of phytoplankton to stages PZ2 or M1 and then fed either live Artemia, live or dead copepods, or a microparticulate microbound diet. The experiments were terminated and all larvae were harvested when more than 80% of larvae had molted to postlarvae 1 (PL1) within any flask representing any of the treatments. The comparative value of the different diets and feeding regimes was determined by mean survival, mean dry weight and total length of individual larva, and percentage of surviving larvae that were PL1. Trypsin activity of samples of larvae from each treatment was also determined. The microparticulate microbound diet effectively served as a complete substitute for Artemia nauplii when fed beginning at stage M1. When fed at the beginning of the PZ2 stage, survival was comparable to that of larvae fed Artemia, but mean dry weight, mean total length, and percent of surviving larvae that were PL1 generally were significantly less. Responses to the feeding of copepods, whether fed dead or live, as a substitute were generally significantly less than those of larvae fed either the Artemia nauplii or the microparticulate diet. Values of trypsin activity (10^− 5 IU/μg^- 1 dry weight) corresponded to the relative proportions of the different larval stages within a treatment, with higher activity being characteristic of early stages. Previously demonstrated successful results with another species of crustacean suggest that the microparticulate microbound diet has characteristics that should be effective in the culture of the carnivorous stages of other crustacean and fish larvae that are currently fed live Artemia nauplii.     

Feeding early larval stages of fire shrimp Lysmata debelius (Caridea, Hippolytidae)

An important constraint to the commercial rearing of the marine ornamental shrimp Lysmata debelius is high larval mortality during early stages due to inappropriate procedures of larval collection and not feeding a live prey before one day elapsed after hatching. This incorrect feeding practice is commonly adopted in larval rearing of L. debelius and other ornamental marine shrimps because it is wrongly assumed that reserves of the newly hatched are enough for the first 24 h of life. Present work demonstrates that captive newly hatched L. debelius larvae ingest microalgae within minutes after hatching. When fed solely with Artemia nauplii, they have acceptable survival rates with stocking densities at or below 50 larval L^–1; but when nauplii are combined with microalgae, survival is further improved to zoea 2 as initial mortality is reduced, and higher stocking densities are supported (up to 75 larvae L^–1). The microalgae used were Rhinomonas reticulata, Skeletonema costata and Tetraselmis chuii. Higher survival through metamorphosis to zoea 2 was always observed for groups fed combinations of microalgae including Tetraselmis chuii. It is recommended that, larval collection methods ensure that larvae are fed microalgae within 2–3 h of release.     

Dietary mannan oligosaccharide enhances salinity tolerance and gut development of larval cobia

The potential beneficial effects of supplementing live feeds with mannan oligosaccharide (MOS; BioMos®) upon cobia Rachycentron canadum larval performance were examined. Characteristics of fish examined included survival to weaning, growth, ability to withstand osmotic stress and the degree of development of the brush border of the intestine. Live feeds included rotifers (Brachionus plicatilis) and Artemia which were enriched for 24 h with a commercial enrichment media alone or in combination with 0.2% (dry weight basis) MOS. Salinity challenges were performed at 6 days post-hatch (dph) and at 7, 13, and 14 dph (0 and 65 g L^− 1 for 6 dph; 0 and 55^− 1 7+ dph) corresponding to transitions in feeding, to examine the ability of larval cobia to survive stress. Differences (P < 0.05) in survival, favoring cobia receiving MOS-supplemented feeds were discerned at 6 and 7 days post-hatch (dph) when fish were challenged at 0 g L^− 1 and at 13 dph when challenged with 55 g L^− 1 salinity water. Electron microscopy of the mid-intestine of developing larvae revealed that MOS-supplemented diets enhanced (P < 0.05) the height of microvilli while reducing (P < 0.05) the occurrence and size of supranuclear vacuoles. Supplementation of diets with MOS could assist cobia larvae in maintaining allostasis especially when reared at sub-optimal salinities.     

Effect of feeding scheme and prey density on survival and development of Chinese mitten crab Eriocheir sinensis zoea larvae

The effect of feeding scheme and prey density on survival and development of Eriocheir sinensis zoea larvae was studied in three experiments. Different combinations and densities of rotifers (Brachionus rotundiformis) and newly hatched Artemia nauplii were fed to zoea larvae. Average survival at each stage, larval development (larval stage index, LSI), duration of zoeal stage and individual megalopa dry weight were compared among treatments. This study revealed that, under the experimental conditions, rotifers should be replaced with Artemia between the zoea 3 (Z3) and the zoea 4 (Z4) stage. The optimal rotifer feeding densities for zoea 1 (Z1) and zoea 2 (Z2) were 15 and 20 mL^?1 respectively, while the optimal Artemia feeding density for Z3, Z4 and zoea 5 (Z5) was 3, 5 and 8 mL^?1 respectively. Further trials in production scale are recommended.     

Suitability of the copepod, Acartia clausi as a live feed for Seabass larvae (Lates calcarifer Bloch): Compared to traditional live-food organisms with special emphasis on the nutritional value

Though artificial propagation of Asian seabass Lates calcarifer (Bloch) in captivity through induced breeding techniques is standardized under Indian conditions, larval and nursery rearing techniques including suitable nursery feeds have to be standardized to obtain better survival and growth. Feeding experiments in triplicate were conducted to evaluate the suitability of the marine copepod Acartia clausi as live prey for fourteen day-old seabass larvae (6.53 ± 0.06 mm; 8.58 ± 0.33 mg) and compared with the traditional live prey, rotifers and Artemia nauplii. While A. clausi and rotifers were mass produced using algae Isochrysis galbana, Chaetoceros affinis and Chlorella marina, Artemia nauplii were produced using cysts. Nutritional quality of cultured copepods was evaluated based on the proximate composition, amino acid and fatty acid composition, and compared with that of rotifers and Artemia nauplii. Proximate composition varied significantly (P < 0.05) among the different live feeds. A. clausi showed higher protein (63.12%) and lipid (16.65%) content than Artemia nauplii and rotifers. Total essential amino acids content was 2% lower in A. clausi compared to that in Artemia nauplii. Fatty acid profiles of the live feed organisms showed that A. clausi is a rich source of n − 3 fatty acids. The total n − 3 fatty acid content of A. clausi was 33.94%. Length, weight overall weight gain and survivorship were significantly (P < 0.05) different among the dietary treatments, and weight gain was comparatively higher in A. clausi fed larvae. Survival of seabass larvae fed A. clausi was obtained highest as 58.13% against the lower values of 39.93% and 41.62% in larvae fed rotifer and Artemia nauplii respectively. Final carcass composition of the larvae of L. calcarifer fed different live-food organisms showed significant differences (P < 0.05) among the dietary treatments. The fatty acid composition of the dietary treatments was reflected to a certain extent in the fatty acid composition of the seabass larvae. The present investigation revealed the nutritional value of calanoid copepod and thus underlining its usefulness as a suitable live-food organism for rearing larvae of the commercially valuable Asian seabass.     

Effect of different enrichment products rich in docosahexaenoic acid on growth and survival of meagre,Argyrosomus regius (Asso, 1801)

Live prey used in aquaculture to feed marine larval fish – rotifer and Artemia nauplii – lack the necessary levels of n‐3 polyunsaturated fatty acids (n‐3 PUFA) which are considered essential for the development of fish larvae. Due to the high voracity, visual feeding in conditions of relatively high luminosity, and cannibalism observed in meagre larvae, a study of its nutritional requirements is needed. In this study, the effect of different enrichment products with different docosahexaenoic acid (DHA) concentrations used to enrich rotifers and Artemia metanauplii have been tested on growth, survival, and lipid composition of the larvae of meagre. The larvae fed live prey enriched with Algamac 3050 (AG) showed a significantly higher growth than the rest of the groups at the end of the larval rearing, while the larvae fed preys enriched with Multigain (MG) had a higher survival rate. DHA levels in larvae fed prey enriched with MG were significantly higher than in those fed AG‐enriched prey. High levels of DHA in Artemia metanauplii must be used to achieve optimal growth and survival of meagre larvae.     

First feeding of Octopus vulgaris Cuvier, 1797 paralarvae using Artemia: Effect of prey size, prey density and feeding frequency

Different assays related to the first feeding of Octopus vulgaris Cuvier, 1797 are compiled in this paper. They include: age at initial feeding age, prey size selection and optimal density, attack timing after feeding, and effect of dose number on the number of captures. Prey capture and ingestion processes were also analysed. Food supplied was cultured Artemia sp. Each assay lasted 15 min.Although paralarvae already start to feed on the hatching day (day 0), it is during day 2 when a greater number of attacks is recorded (81.7 ± 14.7% paralarvae attack). They mainly prefer (significance level α = 0.05) large Artemia, 1.4 ± 0.4 mm (77.0 ± 5.6% of the total attacks) than small Artemia, 0.8 ± 0.1 mm (23.0 ± 5.6%). There is also a slight predilection for the lowest Artemia concentration (33.3 ±12.6% paralarvae attack in a 0.1 Artemia ml^− 1 density, opposite 16.7 ± 7.6 and 18.3 ± 7.6% in densities of 0.5 and 1 Artemia ml^− 1 respectively). The greatest predatory activity is recorded during the first 5 min after food is supplied (72.2 ± 25.5%). An increase in the predatory activity was also observed when food was distributed in several doses instead of a single dose (75.0 ± 10.0% and 46.7 ± 17.6% respectively). It was proved for the first time that paralarvae completely ingest their preys (including their exoskeletons), in this case Artemia. Time needed for their total ingestion ranges between 4 and 10 min.     

The effects of supplemental dietary cholesterol on growth, development and survival of mud crab, Scylla serrata, megalopa fed semi-purified diets

The effects of varying levels of dietary cholesterol on growth, development time and survival of mud crab, Scylla serrata megalopa were investigated using semi-purified microbound diets (MBD). Five iso-energetic diets containing different level of cholesterol ranging from 0.14% to 1% of dry weight of the diet were tested. Fifteen megalopa were reared individually for each dietary treatment, and development time and survival were recorded on a daily basis. More than 25% of megalopa from all treatments were able to metamorphose into the first crab stage, suggesting that the endogenous level of cholesterol in the basal diet (0.14%) was sufficient to support development of the megalopa stage of this species. Widest mean carapace width (3.53 ± 0.08 mm) and highest mean dry weight (2.11 ± 0.22 mg) were recorded for juveniles that molted from megalopa fed live Artemia, whereas no megalopa in the unfed control treatment metamorphosed into crabs. The average development time from megalopa to the juvenile crab stage varied between the treatments, where megalopa fed live Artemia or MBD containing 0.2%, 0.4% or 0.8% total cholesterol showed the most synchronized molting (between 8.0 and 9.9 days). Longest development time was recorded for the megalopa fed diets containing 0.14% or 1% total cholesterol (both 11 days). Highest survival (74.3%) was recorded for the megalopa fed a diet containing 0.8% cholesterol. The results of this study are valuable in research to develop formulated diets for mud crab larvae as a replacement for live food in hatchery culture.     

Effect of starvation during late megalopa stage of Mithraculus forceps (Brachyura: Majidae) on larval duration, synchronism of metamorphosis, survival to juvenile, and newly metamorphosed juvenile size

Larval resistance to temporary starvation is considered a key factor for successful development in the wild. Subjecting larvae to temporary starvation during early and/or late development is occasionally used in larviculture to reduce production costs.Mithraculus forceps is a popular species in the marine aquarium industry for their ability to control nuisance algae in aquarium tanks; a larval culture methodology was previously proposed in order to avoid collection from the wild. In an attempt to reduce production/feeding costs of M. forceps larval culture (two zoea stages and a megalopa), larvae (megalopa stage) were starved after 7 and 8 days post-hatch (DPH); starvation treatments were compared with those of the control treatment where larvae were fed continuously. No differences were found in survival to juvenile, metamorphosis synchronism or larval duration between the treatments, which suggest that at least by day 7 DPH, megalopae have already achieved the point-of-reserve-saturation (PRS) and are able to successfully metamorphose to crab stage without feeding (facultative lecithotrophic); newly metamorphosed juveniles are slightly smaller (particularly the ones starved after 7DPH). This flexible way of development might be very advantageous in the wild and might allow the reduction of costs of larval culture in captivity.     

Improved techniques for rearing mud crab Scylla paramamosain (Estampador 1949) larvae

A series of rearing trials in small 1 L cones and large tanks of 30–100 L were carried out to develop optimal rearing techniques for mud crab (Scylla paramamosain) larvae. Using water exchange (discontinuous partial water renewal or continuous treatment through biofiltration) and micro‐algae (Chlorella or Chaetoceros) supplementation (daily supplementation at 0.1–0.2 million cells mL⁻¹ or maintenance at 1–2 millions cells mL⁻¹), six different types of rearing systems were tried. The combination of a green‐water batch system for early stages and a recirculating system with micro‐algae supplementation for later stages resulted in the best overall performance of the crab larvae. No clear effects of crab stocking density (50–200 larvae L⁻¹) and rotifer (30–60 rotifers mL⁻¹) and Artemia density (10–20 L⁻¹) were observed. A stocking density of 100–150 zoea 1 (Z1) L⁻¹, combined with rotifer of 30–45 mL⁻¹ for early stages and Artemia feeding at 10–15 nauplii mL⁻¹ for Z3–Z5 seemed to produce the best performance of S. paramamosain larvae. Optimal rations for crab larvae should, however, be adjusted depending on the species, larval stage, larval status, prey size, rearing system and techniques. A practical feeding schedule could be to increase live food density from 30 to 45 rotifers mL⁻¹ from Z1 to Z2 and increase the number of Artemia nauplii mL⁻¹ from 10 to 15 from Z3 to Z5. Bacterial disease remains one of the key factors underlying the high mortality in the zoea stages. Further research to develop safe prophylactic treatments is therefore warranted. Combined with proper live food enrichment techniques, application of these findings has sustained a survival rate from Z1 to crab 1–2 stages in large rearing tanks of 10–15% (maximum 30%).     

The larval rearing of the marine ornamental crab, Mithraculus forceps (A. Milne Edwards, 1875) (Decapoda: Brachyura: Majidae)

The goal of this study is to develop a larviculture protocol for Mithraculus forceps, a popular marine aquarium species. Different temperatures (25±0.5°C and 28±0.5°C), stocking densities (10, 20, 40 and 80 larvae L^?1), prey densities (newly hatched Artemia of 1, 4, 7 and 12 nauplii mL^?1) and metamorphosis to crab conditions (Systems A and B) were tested. The best survivorship and faster development were obtained when the larvae were reared at a density of 40 larvae L^?1 for 7 days post hatching (DPH) in System A, at 28°C and fed with 7 mL^?1 of newly hatched Artemia nauplii. After 7 DPH all the megalopa were moved to System B and the same temperature and prey density were maintained. At the end of the experiment, 12 DPH, survivorship of 74.1±4.8% was obtained.     

Brachionus vs Artemia duel: Optimizing first feeding of Upogebia pusilla (Decapoda: Thalassinidea) larvae

Larval rearing of many marine organisms is dependent on the availability of live food. The aim of this study was to optimize larval first feeding for the mud shrimp Upogebia pusilla, by comparing the effectiveness of the two most commonly used live feeds: Brachionus plicatilis and Artemia sp. nauplii. Survival, larval duration, molt synchronism and megalop size were compared using five feeding treatments: Artemia from zoea I to IV (B0), Brachionus during zoea I and Artemia from zoea II to IV (B1), Brachionus during zoea I and II and Artemia during zoea III and IV (B2), Brachionus from zoea I to III and Artemia during zoea IV (B3) and Brachionus from zoea I to IV (B4). The proportion of larvae that reached the megalop stage was 0.00% in treatment B0, 3.33% in treatment B1, 33.33% in treatment B2, 66.67% in treatment B3 and 76.67% in treatment B4. Larvae fed on rotifers until zoea III or zoea IV stages had a higher survival but no differences were found either in time to reach megalop or in megalop size. This study demonstrates that rotifers are essential for the survival and development of U. pusilla early larval stages but that rotifers can be successfully replaced by Artemia nauplii in the zoea IV stage.     

Predation and energetics of Penaeus indicus (Decapoda: Penaeidae) larvae feeding on Brachionus plicatilis and Artemia nauplii

Brachionus plicatilis and Artemia nauplii were fed to a number of larval stages of the penaeid prawn Penaeus indicus to determine ingestion rates, larval energy requirements and to establish at which stage larval predation commenced. The raptorial feeding rates were then contrasted on an energy basis with filter feeding rates for P. indicus larvae to compare the relative efficiency of these two feeding mechanisms. Brachionus was first eaten as early as protozoea 1 to protozoea 2, while the maximum ingestion rate of 300 rotifers larva^?1 d^?1 (1.06 J larva^?1 d^?1) was obtained during protozoea 3 to mysis 1. Artemia were effectively ingested by P. indicus protozoea 3 (4.1 J larva^?1 d^?1) to post-larva (8.2 J larva^?1 d^?1). Daily energy intake rate from filter feeding increased from 1.1 J larva^?1 d^?1 during protozoea 1 to reach a peak of 5.32 J larva^?1 d^?1 during mysis 3 after which it declined to 2.66 J larva^?1 d^?1 during the post-larval stage. This decline in energy intake from filter feeding with a concomitant increase in energy intake from Artemia predation demonstrates a predominant feeding mode changeover point during mysis 3. Energy intake was consistently low with Brachionus, indicating that it may be unnecessary for commercial culture purposes.     

Evaluation of frozen Umbrella‐stage Artemia as first animal live food for Litopenaeus vannamei (Boone) larvae

An alternative larval shrimp feeding regime, in which umbrella‐stage Artemia were constituting the first zooplankton source was evaluated in the culture of Litopenaeus vannamei. In a preliminary experiment, umbrella‐stage Artemia were fed to larvae from zoea 2 (Z2) to mysis 2 (M2) stages to identify the larval stage at which raptorial feeding starts and to determine daily feeding rates. The following experiment evaluated the performance of two feeding regimen that differed during the late zoea/early mysis stages: a control treatment with frozen Artemia nauplii (FAN), and a treatment with frozen umbrella‐stage Artemia (FUA). The ingestion rate of umbrella‐stage Artemia increased from nine umbrella per larvae day^?1 at Z2 stage to 21 umbrella per larvae day^?1 at M2. A steep increase in ingestion and dry weight from Z3 to M2 suggests a shift to a raptorial feeding mode at the M1 stage. Treatment FUA exhibited a significantly higher larval stage index (P < 0.05) during the period that zoea larvae metamorphosed to the mysis stage, and a higher final biomass, compared with treatment FAN. Based on these results and on practical considerations, a feeding regime starting with umbrella‐stage Artemia from Z2 sub‐stage can be recommended for L. vannamei larvae rearing.     

Development of lipid microbeads for delivery of lipid and water-soluble materials to Artemia

Lipid spray beads (LSB) containing high concentrations of phospholipids were produced in order to improve their dispersion in both fresh and saltwater. The beads were developed to deliver both fat-soluble and water-soluble micronutrients to Artemia and other suspension feeders. LSB were prepared by spraying molted lipid into a chamber that was cooled with liquid nitrogen in order to solidify the lipid beads. Addition of soy lecithin to LSB did not affect retention of glycine when the beads were suspended in distilled water. There was an initial loss of 80% incorporated glycine after LSB were suspended in water for 20min. Artemia readily ingested riboflavin-containing LSB and their full guts were evident within 30min of feeding. The riboflavin content of Artemia could be increased from 55 ±  0.6 mg kg^− 1 (dw) to 329 ± 62 mg kg^− 1 (dw) after 1h enrichment. LSB prepared with phospholipids are promising vehicles for enrichment of suspension-feeding organisms used as feed for larval marine fish and crustaceans as well as other suspension feeders.     

Effect of larval and prey density, prey dose and light conditions on first feeding common dentex (Dentex dentex L.) larvae

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.     

Survival of blue king crab Paralithodes platypus Brandt, 1850, larvae in cultivation: effects of diet, temperature and rearing density

Blue king crab (Paralithodes platypus) larvae were cultivated to test the effects of diet, temperature and rearing density. Dietary treatments included no feeding (unfed), Artemia nauplii enriched with diatoms Thalassiosira nordenskioeldii (THAL), unenriched Artemia fed in addition to Thalassiosira (A+THAL) and a control diet of Artemia enriched with frozen Isochrysis paste (ISO 6). Trials were conducted at 6 °C, and a rearing density of 10 zoea L^?1, with six replicates per treatment. The ISO 6 diet was also tested at 3 °C (ISO 3) and 9 °C (ISO 9), and at densities of 20 (ISO 20) and 40 (ISO 40) zoea L^?1. Survival of zoea larvae fed the A+THAL diet (91.7%) was significantly higher than all others, whereas unfed zoea larvae died within 2 weeks. Temperature and rearing density had no significant effects on survival. Time required to reach stage C1 was significantly greater at 3 °C (109 days) than at 6 °C (70 days), but did not decrease further at 9 °C. After reaching the postlarval (glaucothoe) stage, half of the replicates in the ISO 20 and ISO 40 treatments were fed continuously, but survival did not differ significantly from unfed glaucothoe. We conclude that blue king crab larvae are not lecithotrophic and can be cultivated with high survival using the proper diet. These techniques can be used to produce large numbers of juvenile crab for laboratory research, or could be modified for use in stock‐enhancement programmes.