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.     

Effects of delayed first feeding on larval growth,survival and development of the sea cucumber Apostichopus japonicus (Holothuroidea)

The time of first feeding is an important factor for establishing successful exogenous feeding in aquaculture hatcheries as it is crucial for larval survival and growth. The effects of delayed first feeding by the sea cucumber Apostichopus japonicus larvae were investigated. Groups of larvae were fed immediately after completion of the digestive tract (fed control) or starved for 24, 48, 72, 108 and 120 h post fertilization. The growth rates of A. japonicus larvae were the same as those of the control group when first feeding was delayed for less than 72 h. When the period of starvation was beyond 72 h, growth rates were reduced. The fed control group had the highest percentage of late auricularia larvae (70.0%) on day 11, followed by the groups starved for 24, 48, and 72 h, respectively, which had 35.00%, 43.48% and 41.67% of late auricularia larvae. When larvae were starved for more than 72 h, the percentage of late auricularia larvae never exceeded 12.0%. Most larvae halted in development and were deformed before reaching metamorphosis when starved for 108 and 120 h. Prolonged exposure to starvation (more than 48 h) resulted in a significant decrease in percentage of larvae reaching settlement. The point‐of‐no‐return (PNR) of A. japonicus larvae was calculated 110.4 h. Ratios of stomach length to total length, stomach width to total width were more sensitive to starvation than other larval morphometrics. To avoid mortality and obtain adequate growth and development, A. japonicus larvae in commercial culture should be fed within 48 h of the completion of the digestive tract.     

Effects of starvation on larval growth,survival and metamorphosis of Ivory shell Babylonia formosae habei Altena et al., 1981 (Neogastropoda: Buccinidae)

The impact of starvation on larvae of Ivory shell Babylonia formosae habei was studied in a laboratory experiment. Newly hatched veligers showed considerable tolerance to starvation due to their endogenous yolk material, and time to the point-of-no-return (PNR; the threshold point during starvation after which larvae can longer metamorphose even if food is provided) was calculated to be 104.5 h. However, starvation still affected larval growth, survival, and metamorphosis. Mean shell length of larvae increased 49.77 μm day⁻¹ for nonstarved, but only 11.13 μm day⁻¹ for larvae starved for 108 h. After larvae began feeding, their growth rates rapidly recovered to the level of the nonstarved following short periods of starvation (less than 48 h), but were inhibited and unable to ever reach the level of the nonstarved when being starved beyond 48 h. Percent metamorphosis was 53.75% for the nonstarved, but all larvae died before 10 days for those starved for 108 h. Starvation not only affected larval time to reach metamorphosis, but also caused the delay in the time to metamorphosis. For the nonstarved, larvae took only 11.5 days to reach spontaneous metamorphosis, but they took 20 days to reach spontaneous metamorphosis when starved for 96 h, and this duration of delayed metamorphosis reached 8.5 days. Furthermore, the importance of yolk material for maintaining larval survival of B. formosae habei during starvation periods is also discussed.     

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.     

Effects of Starvation and Feeding on Lipid Class and Fatty Acid Profile of Late Stage Mud Crab,Scylla serrata,larvae

Lipid class and fatty acid (FA) analysis were conducted on newly molted, fed, and starved zoea V and megalopa of the mud crab, Scylla serrata (S. serrata). Larvae starved for 4 d showed a substantial decrease in total FA content, from 49.67 μg/mg to 13.94 μg/mg ash‐free dry weight (AFDW) at the zoea V stage, and from 38.47 μg/mg to 10.40 μg/mg AFDW at the megalopa stage. This depletion indicates that S. serrata larvae effectively utilize stored lipid reserves for energy during periods of food deprivation. Megalopa subjected to longer starvation periods, however, did not utilize lipid as the major energy source after day 4, suggesting increased reliance on protein catabolism during prolonged starvation. At both larvae stages the major FAs were 18:1n‐9, 16:0, 20:5n‐3 (eicosapentaenoic acids, EPA), 18:3n‐3 (linolenic acid, LNA), 18:0 and 22:6n‐3 (docosahexaenoic acid, DHA) and this FA profile persisted in both fed and starved larvae. The highly unsaturated fatty acids (HUFA), EPA, DHA, and arachidonic acid (20:4n‐6, AA) were not conserved in tissue during starvation, indicating that HUFA requirements might be lower for S. serrata larvae than shown for other crustaceans. Similarly, a high level of LNA in newly molted zoea V and megalopa were rapidly depleted in unfed larvae, indicating that this FA had an important role as an energy reserve. Throughout the study, FAs from the polar lipid fraction dominated larvae tissues, while FAs from the neutral lipid constituted the largest accessible energy reserve during starvation (depleted from 23.05 to 1.23 μg/mg AFDW in zoea V, and from 19.00 to 1.27 μg/mg AFDW in megalopa). The results of this study provide new insight into lipid utilization of S. serrata larvae during development, an important step toward development of formulated diets for use in mud crab hatcheries.     

Survival and growth of instar 1 phyllosoma of the western rock lobster, Panulirus cygnus, starved before or after periods of feeding

Adequate nutrition is a principal factor in controlling survival and growth in crustacean larval culture. The present study examined the effects of starvation before or after feeding on survival, total intermoult period and postmoult size of phyllosoma of the western rock lobster, Panulirus cygnus. Individually held instar 1 larvae were reared at 25 °C and submitted to initial periods of starvation to determine the 50% level of the point-of-no-return (PNR₅₀), and initial periods of feeding to determine the 50% level of the point-of-reserve-saturation (PRS₅₀). As the initial starvation periods before feeding increased, the total intermoult period for instar 1 larvae that survived increased. The PNR₅₀ was 4.6 days. The different initial feeding periods before starvation resulted in a difference in postmoult size of larvae after moulting to instar 2, but had little effect on the total intermoult period. Larvae fed for the shortest periods were significantly smaller than those fed longer. The PRS₅₀ was 3.6 days. For both treatments, limited effects of the starvation or feeding regimes were apparent for larvae that moulted to instar 2 and continued development to instar 3. When larvae were fed before PNR₅₀, there were no delayed effects of the initial starvation period. Initial feeding periods longer than 5–6 days did not significantly affect larval survival or growth. This information will be useful in the design of feeding regimes in phyllosoma culture.     

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.     

First Record of Captive Larval Culture and Metamorphosis of the Pacific Blue Tang,Paracanthurus hepatus

The Pacific blue tang, Paracanthurus hepatus, is consistently among the top 20 marine ornamental species imported into the USA, with all specimens presently sourced from wild stocks. Captive culture of this species through metamorphosis has not been previously documented and fundamental information regarding reproduction, larval culture, and production techniques is scarce. This study aimed to elucidate methods that would advance our understanding and success with captive propagation of this species. A total of 50,000 eggs were collected from a single broodstock population and stocked in a 1000‐L tank. Beginning at 3 d posthatch (DPH), larvae were fed three times daily a diet comprised exclusively of copepod nauplii. At 12 DPH, enriched rotifers were first fed followed by powdered feed (20 DPH) and first instar Artemia (21 DPH). Large mortality events were observed at 7 and 20 DPH, corresponding with starvation and flexion, respectively. By 41 DPH, the majority of the remaining larvae began associating with the bottom of the culture tank. On Day 50, the first signs of blue pigmentation marked the beginning of metamorphosis. A total of 27 juvenile blue tangs were cultured during this trial. This effort represents the first successful culture of this species in captivity.     

Quality assessment of newly hatched mud crab,Scylla serrata,larvae

Starvation and exposure to formalin were investigated as possible stress tests for evaluating the quality of mud crab, Scylla serrata, larvae. For the starvation stress test, newly hatched zoeae stocked in 150‐ml containers were either starved or fed rotifers. Similarly, newly hatched zoeae were stocked in containers with seawater of 0 (control), 20, 30 and 40 mg/L formalin for the formalin stress test. The zoeae from the same batches were used for seed production to monitor their performance and validate the results of stress tests. Starvation was found to be unsuitable for larval quality evaluation. However, the impact of initial food deprivation on the newly hatched larvae indicates that feeding immediately after hatching is necessary for mud crab larvae. Exposure of larvae to 40 mg/L formalin for 3 hr appeared to be a reliable and practical method for larval quality assessment as the survival of larvae in the mass production tanks validated the classification of good and poor quality batches in the stress tests. On this basis, a hatchery operator can decide which batch should be cultured further. Finally, there appears to be a link between the quality of larvae and the performance at the megalopa and early juvenile crabs.     

The effects of starving and feeding on Dover sole (Solea solea,Soleidae, Linnaeus, 1758) stress response and early larval development

In the view of an urgent necessity to improve the quantity and the quality of farmed fish species, there is a strong need to improve our basic knowledge on the effects of first feeding during the developmental stages of fish larvae. High mortality, mainly due to food deprivation or inappropriate food quality, has been observed in many larval fish species, but knowledge about the morphological, biochemical and molecular processes related to this topic is still poorly understood. The understanding of the early larval ontogeny as well as the larval nutritional requirements and the molecular and cellular mechanisms elicited by fish larvae during food deprivation and starvation are thus of primary importance. At this regard, this study investigates, in Dover sole larvae, the effects of starvation and starving/re‐feeding procedures at a morphological, histological, biochemical and molecular level. The results evidenced that starved larvae progressively decrease in growth, lipid content, affected their gastrointestinal tract and muscle development and increased cortisol and heat shock protein 70 levels. On the contrary, starved and re‐fed larvae showed, after the restoration of a favourable feeding condition, a compensatory growth. In conclusion, this is the first study analysing through a multidisciplinary approach the effects of food deprivation on the development of an important economic species, the Dover sole.     

Ontogenetic development of digestive functionality in golden pompano Trachinotus ovatus (Linnaeus 1758)

Ontogenetic development of the digestive system in golden pompano (Trachinotus ovatus, Linnaeus 1758) larvae was histologically and enzymatically studied from hatch to 32 day post-hatch (DPH). The development of digestive system in golden pompano can be divided into three phases: phase I starting from hatching and ending at the onset of exogenous feeding; phase II starting from first feeding (3 DPH) and finishing at the formation of gastric glands; and phase III starting from the appearance of gastric glands on 15 DPH and continuing onward. The specific activities of trypsin, amylase, and lipase increased sharply from the onset of first feeding to 5–7 DPH, followed by irregular fluctuations. Toward the end of this study, the specific activities of trypsin and amylase showed a declining trend, while the lipase activity remained at similar levels as it was at 5 DPH. The specific activity of pepsin was first detected on 15 DPH and increased with fish age. The dynamics of digestive enzymes corresponded to the structural development of the digestive system. The enzyme activities tend to be stable after the formation of the gastric glands in fish stomach on 15 DPH. The composition of digestive enzymes in larval pompano indicates that fish are able to digest protein, lipid and carbohydrate at early developmental stages. Weaning of larval pompano is recommended from 15 DPH onward. Results of the present study lead to a better understanding of the ontogeny of golden pompano during the larval stage and provide a guide to feeding and weaning of this economically important fish in hatcheries.     

Ontogenetic development of digestive enzymes in larval and juvenile crimson snapper Lutjanus erythopterus (Bloch 1790)

Ontogenetic development of digestive system in crimson snapper (Lutjanus erythopterus Bloch 1790) larvae was histologically and enzymatically (alkaline phosphatase, amylase, lipase, pepsin, trypsin) examined from hatching to 36 days post hatching (DPH). The ontogenetic development of crimson snapper larval fish ontogeny was divided into three distinct phases: phase I starting from hatch to the onset of exogenous feeding, phase II starting from first feeding (2–3 DPH) until the formation of gastric glands (13–14 DPH) and phase III beginning from the appearance of gastric glands and continuing onwards. The specific activities of amylase, lipase, trypsin showed sharp increase and reached to the maximum from hatch to 4 DPH, 10 DPH, 20 DPH, respectively, followed by a declining trend with irregular fluctuation. In contrast to other enzymes, the specific activities of alkaline phosphatase showed a gradual increase from hatch to 29 DPH, followed by a sharp increase towards 36 DPH. The specific activity of pepsin was firstly detected on 17 DPH and gradually increased towards the end of this study. The total activities of these five enzymes showed a gradual increase till 29 DPH, followed by a sharp increase towards 36 DPH except for amylase and lipase reaching maximum at 32 DPH. The present study provides better understanding of the digestive ontogeny of crimson snapper during the larval stage and a guide to feeding and weaning of this economically important fish in hatcheries.     

不同循环饥饿投喂模式对尼罗罗非鱼补偿生长的影响

为了探讨尼罗罗非鱼对不同循环饥饿投喂模式的补偿生长效应,本实验分别采用每天投喂(S0)及饥饿1 d+投喂3 d(S1F3)、饥饿1 d+投喂5 d(S1F5)、饥饿1 d+投喂7 d(S1F7)、饥饿2 d+投喂3 d(S2F3)、饥饿2 d+投喂5 d(S2F5)和饥饿2 d+投喂7 d(S2F7)6种不同的循环投喂模式,用含33%蛋白质和8%脂肪的饲料饲养尼罗罗非鱼(均重13.50 g),饲喂期为43 d。结果显示,S0组的增重率(806.74%)最高,与S1F3、S1F5和S1F7组差异不显著,但分别比S2F3、S2F5和S2F7组显著提高40.3%、33.6%和10.4%;S0组的特定生长率最低(5.36%),显著低于其他各组;与对照组相比,采用循环投喂模式没有改善饲料转化率和蛋白质效率,但却能明显提高日摄食率;各实验处理组肝体比、脏体比、肥满度、鱼体灰分含量、肌肉RNA/DNA比值及血清总胆固醇、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇和尿素氮含量与对照组差异不显著;S1F3、S1F5和S1F7组鱼体蛋白质和脂肪含量、血清甘油三酯含量及血清谷丙转氨酶和谷草转氨酶活性与S0组差异不显著,但S2F3、S2F5和S2F7组鱼体蛋白质和脂肪含量及血清甘油三酯含量显著低于S0组,血清谷丙转氨酶和谷草转氨酶活性显著高于S0组。研究表明,尼罗罗非鱼在S1F3、S1F5和S1F7模式下获得了完全补偿生长,而在S2F3、S2F5和S2F7模式下仅获得了部分补偿生长,且均是通过提高恢复投喂期间的摄食量来实现补偿生长。在获得完全补偿生长的3组中,S1F3组的实际投喂天数最短,仅为33 d,比每天投喂模式缩短了23.3%,因此在本实验条件下,饥饿1 d+投喂3 d是最佳的循环饥饿投喂模式。     

Effect of the lipid droplet adherence on growth and survival of the European hake (Merluccius merluccius) larvae

The effect of the adherence of the lipid droplet in the yolk‐sac on the growth and survival of the European hake (Merluccius merluccius) larvae was studied under starved and feeding conditions. Recently hatched hake larvae with adhered and non‐adhered lipid droplet (ALD and non‐ALD) were maintained during 8 days under starvation conditions. The adherence of the lipid droplet positively affected larval survival during starvation. At the end of the yolk consumption period (7–8 days after hatching), 90% of the surviving larvae had an ALD, while 10% of the survivors had a non‐ALD and showed a higher mortality rate. In a month feeding experiment, results show that the presence of non‐ALD in newly hatched hake larvae negatively affected their growth and survival. Dry weight and length (TL) of 20‐days‐old larvae with ALD were significantly higher than those with non‐ALD. Furthermore, lifespan of those larvae with non‐adhered lipid droplet was shorter, with most of them dying during the first 15–20 days of culture. As conclusion, the percentage of the lipid droplet adherence at hatching could be used as an indicator of ‘quality’ for European hake larvae: the greater the number of larvae with adhered lipid droplet, the better larval growth and survival.     

A closed water recirculation system for ecological studies in marine fish larvae: growth and survival of sea bass larvae fed with live prey

This paper describes the suitability of a closed recirculation system to study the development of fish larvae in a strictly controlled environment, where only feeding was varied (fed, starved, delayed and late fast treatments). The system served both as an incubator and hatchery. The time variation of physical and chemical parameters together with survival and growth of reared sea bass larvae (Dicentrarchus labrax) were studied over the first month of life. The recirculation design allowed for the maintenance of levels of ammonia, nitrite and nitrate below those cited as responsible for mortality or decreased feeding ability in other marine fish larvae. Almost no larval mortality occurred in the fed larvae from day 9 after hatching. The starved group of larvae showed a sharp decline in survival after 16 days of food deprivation. Larvae for which feeding was delayed until day 13 ceased dying 4 days after food was supplied. Fast feeding on days 24 and 25 had no effect on larval survival. Growth in length was similar during the first 2 weeks of larval life regardless of feeding treatment. Two days of late fast had no effect on larval growth. Growth patterns of fed larvae in this study were similar to those reported for larvae reared in flow through systems. We believe that survival and growth of the reared larvae was a direct function of diet, and that the type of rearing system did not adversely affect these parameters. The rearing design and the results obtained suggest that future nutritional studies of field-collected larvae will benefit from this kind of rearing experiment.     

Dynamics of yolk sac and oil droplet utilization and behavioural aspects of swim bladder inflation in burbot, Lota lota L., larvae during the first days of life, under laboratory conditions

The study concerns investigation of early larval development of burbot, Lota lota. As part of a two-year study, the first 15 days (until the end of yolk sac resorption) of burbot larvae development under controlled conditions were examined. The aim of the study was to observe the moment of swim bladder inflation and the behavioural aspects of this process, as well as the analysis of yolk and oil droplet resorption and the beginning of exogenous nutrition. It was observed that larvae began to inflate their swim bladder on the 3rd day post-hatch. On 5 DPH, none of the larvae without an inflated bladder was able to swim up the distance separating it (10 cm) from the water surface. Since 9 DPH, 50 % of larvae started exogenous feeding, and the absence of yolk was observed on 13 DPH and oil droplet on 14 DPH, while on 15 DPH, 100 % of feeding larvae were observed. The presented results indicate that the analyzed period is critical for burbot, and it is characterized by a high mortality rate (over 60 %). Additionally, the results suggest that, under controlled conditions, the latest moment when burbot larvae should be given exogenous food is 9–10 DPH and until the moment of the swim bladder inflation, larvae should be kept in tanks with a low water depth (up to 10 cm). The data presented in this study could have a significant influence on the efficiency of larvae rearing, both for aquaculture and for restocking purposes.     

Ozonation of seawater improves the survival of larval southern rock lobster, Jasus edwardsii, in culture from egg to juvenile

Phyllosoma larvae of the southern rock lobster, Jasus edwardsii, were cultured from egg to juvenile. For larvae reared from hatch to Stage III, survival was highest and bacterial contamination was lowest in seawater ozonated at low and moderate levels (400 and 500 mV oxidation-reduction potential, ORP). By contrast, at high ozonation (600 mV), all larvae suffered deformities at the moult to Stage II and terminally starved, while in unozonated water (about 300 mV), all larvae died at Stage III probably as a consequence of Vibrio bacteria proliferation. In a second experiment between Stages VI to VIII, larval survival was highest in ozonated water that had been filtered through activated charcoal and coral sand, compared to ozonated water with no filtration or filtered only through activated charcoal. Ozonated water with the combined filtration was used subsequently but there were ongoing deformities, so the level was progressively reduced from 400 mV at Stage VIII to 330 mV at Stage X, at which time ozonation was discontinued. Larvae were then cultured in unozonated water to metamorphosis of eight pueruli at 377 to 437 days after hatch, of which two survived to juvenile. Ozonation was thus effective up to Stage IX in improving culture water to minimise bacterial disease without problems of larval deformities.     

Effect of an experimental microparticulate diet on the growth, survival and fatty acid profile of gilthead seabream (Sparus aurata L.) larvae

In recent years, a great deal of interest has emerged in the development of microdiets as an economic alternative to live food, in the larval culture of marine fish species. The ability to grow Sparus aurata larvae on a prototype microparticulate diet was examined. To achieve this objective, four feeding regimes differing in the time when the microdiet was introduced (3, 7 or 12 days) and one based exclusively on an inert diet were tested, during the first 22 days of larval life. Significant differences in larval growth were found between the experimental feeding regimes and their corresponding controls (enriched rotifers during the whole experimental period); the larvae in the co-feeding regimes and with an exclusive microparticulate diet were always significantly smaller than larvae fed on rotifers alone. However, the difference was minimised by introducing the inert diet at a later date. A lower survival was found in larvae with a co-feeding regime, in comparison with the control treatments and the survival was significantly lower in larvae fed exclusively on a microparticulate diet. The fatty acid analysis revealed that the experimental microencapsulated diet and the rotifers enriched with Protein Selco® presented relatively similar fatty acid content. In spite of the slightly higher (n?3)/(n?6) and Docosahexaenoic acid (DHA)/Eicosapentaenoic acid (EPA) ratios and somewhat lower highly unsaturated fatty acid (HUFA) content found in the inert diet, the fatty acid composition of the diets cannot explain the differences found in larval performance. The results revealed that the complete replacement of live prey with the tested microparticulate diet is still not possible in S. aurata larval rearing. Nevertheless, better growth and survival results and a substantial reduction in the daily supply of live food can be achieved with a combination of microdiet and live prey.     

Growth, survival and biochemical composition of spider crab Maja brachydactyla (Balss, 1922) (Decapoda: Majidae) larvae reared under different stocking densities, prey:larva ratios and diets

The spider crab Maja brachydactyla is overexploited on the NW coast of Spain. Aquaculture of this species can be the solution to the problem, and consequently, several attempts of intensive larval rearing have been conducted. However, most of the studies already published do not provide enough zoo technical data, especially in terms of larval and prey densities or the nutritional quality of diets used for rearing.Three experiments were carried out to evaluate the conditions for intensive larval rearing of M. brachydactyla. Larval stocking density (10, 50 and 100 larvae L^− 1), prey:larva ratio (15, 30 and 60 enriched Artemia larva^− 1) and diet (enriched Artemia, non-enriched Artemia and polychaete supplement) effects on growth and survival of this species were studied. For larval culture nine, 35 L, 150 μm mesh-bottomed PVC cylinders (triplicates for each treatment and larval stage) connected to a recirculation unit, were used. Temperature and salinity were kept constant at 18 °C and 36‰ respectively. A 12 to 18 day trial was conducted for each experiment and samples of larvae were collected at each larval stage (zoea I, zoea II, megalopa) in the inter-molt phase and at first juvenile. Survival, carapace length and width, dry weight (DW), and proximate biochemical content (protein, carbohydrates and total lipid) as well as lipid class composition were determined.Stocking densities of 100 larvae L^− 1 resulted in higher growth in DW and higher content in lipids and protein for zoea I (ZI) and zoea II (ZII) than 10 larvae L^− 1. However, survival decreased with increasing stocking density.The use of 60 preys larva^− 1 produced larvae with significantly higher DW and protein content, especially at ZII stage, than lower prey densities. Survival rate obtained feeding 60 preys larva^− 1 up to the megalopa stage was almost two-fold (42.2%) the rate obtained using 15 preys larva^− 1 (24.8%).Larvae fed on enriched Artemia (EA) showed an increase in weight up to megalopa (518.9 ± 26.5 μg) in contrast to larvae fed on non-enriched prey (A) (467.9 ± 6.9 μg). Variation in DW correlated with the total lipid content (L) of the larvae (L_EA = 70.1 ± 37.5 μg ind^− 1; L_A = 28.9 ± 3.2 μg ind^− 1) especially in terms of neutral lipids. The use of an initial density of at least 50 larvae L^− 1 and 60 enriched Artemia larva^− 1 can be considered the most adequate rearing parameters in order to obtain good results in growth and survival of M. brachydactyla.     

Effects of different diets on larval development in a peppermint shrimp (Lysmata sp. (Risso))

Currently, only a handful of marine ornamental species are commercially produced through aquaculture. In order for the marine aquarium industry to continue to grow, a diverse selection of cultured animals is required to offset wild collections. Long and variable larval durations are the major bottleneck for mass production of marine ornamental shrimp. Improving larval diet may reduce the larval duration and enhance the prospects of commercial aquaculture. A laboratory study was conducted to examine the effect of different diets on larval development and survival of the peppermint shrimp, Lysmata (gulf coast variety), a popular aquarium shrimp. The effect of three feeding regimes [Artemia alone (ART), ArteMac? alone (COMM) and Artemia in combination with ArteMac? (ART/COMM)] on survival and development were tested. Survival to zoea 5 for both ART and ART/COMM treatments was 99%, but only 62.5% for COMM treatment. ArteMac? alone treatment shrimp only survived to zoea 7. Survival to postlarvae for ART treatment (72.5%) was significantly lower (P<0.01) than those of treatment ART/COMM (80.5%). Larvae fed ART/COMM had significantly (P<0.01) shorter larval duration than larvae fed ART. Fourteen days after the first postlarva appeared, the rates of settlement (85.4% and 67.5% respectively) and survival (68.8% and 49.0% respectively) were significantly greater (P<0.01) for larvae fed the ART/COMM than those fed ART.