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A feeding trial was conducted to assess the effects of dietary Nannochloropsis sp. as powder or lipid on survival, growth performance and fatty acids content in Kuruma shrimp juvenile. Seven isonitrogenous, isolipidic and isocaloric diets were formulated to contain in first group graded levels of Nannochloropsis powder: 0% (CON, control diet), 4% (A), 7% (B) and 10% (C) dry matter then in second group algae oil proportionally extracted (AE, BE and CE, respectively). The feeding trial was conducted for 50 days. The results showed that the substitution of fish oil (FO) with algae powder diets A, B and C significantly (P

Nannochloropsis is one of the most important microalgae utilized as the feedstuff in aquaculture and is emerging model oleaginous microalgae. Recently, different genetic tools such as RNA interference, gene overexpression and gene editing have been developed in Nannochloropsis. However, the available genetic modification methods based on CRISPR technology are rather limited for modulating gene expression. Here, we firstly explored a transcriptional activation system based on CRISPR/dCas9 in N. oceanica IMET1. The result demonstrated that this construct of CRISPRa system (dCas9 protein fused with transcriptional activator VP64) could alter efficiently gene expression in N. ocanica. The expression of targeted gene (an enzyme responsible for DNA or RNA methylation as a methyltransferase) was increased by ~2–6 fold at the transcriptional level. Moreover, the growth and photosynthetic parameter (Fv/Fm) of mutants was increased by 23% and 12% compared to wild type under air-level CO2 respectively. Thus, this system will open new avenue for genome engineering of Nannochloropsis.

Captive breeding of marine ornamental fish is considered as a sustainable alternative to the current practice of fishing the wild stocks to supply the marine aquarium trade. However, efficient larviculture remains the biggest bottleneck, as many marine ornamentals suffered total mortality or only have extremely low survival at early larval stage. This study investigated the optimal conditions for the rearing of early larvae of a valuable ornamental fish, the orchid dottyback Pseudochromis fridmani, in terms of density and combination of live prey, as well as the application of the “greenwater” technique. In the first experiment, larvae were reared in clearwater and fed rotifers at 2, 5, 15, and 40 mL−1. Although there was no significant difference in larval survival among treatments on 8 days post-hatching (DPH), the larvae fed higher rotifer densities (15 and 40 rotifers mL−1) had significantly better growth. In the second experiment, by 8 DPH, a significant interaction between rearing condition (clearwater vs. greenwater) and live prey combination (rotifers only vs co-feed rotifers and copepods) on larval survival was detected, and the mean survival of larvae co-fed rotifers and copepods in clearwater (18%) was significantly lower than the other treatments (45–64%). Moreover, larvae reared in greenwater, or co-fed rotifers and copepods, grew significantly larger than those reared in clearwater, or fed rotifers only, respectively. In the third experiment, the larval survival was higher cell density of Nannochloropsis paste (NAN) used to make greenwater (0–3.40 × 106 NAN cells mL−1). The larval survival of the highest algae density treatment was the highest on 8 DPH (72 ± 8%), and it was significantly higher than those reared in the treatments of 1.13 × 106 or 0 NAN cells mL−1, but not significantly different from that of 2.27 × 106 cells mL−1 treatment. Overall, the results of this study suggest that co-feeding early P. fridmani larvae with rotifers and copepods, with the complementary use of greenwater comprising of ≥ 2.27 × 106 NAN cells mL−1, can enhance larval survival, growth and development. However, when the algal cell density is below this threshold, using such a co-feeding strategy may compromise the survival of P. fridmani larvae. The results of this study highlighted the importance of optimizing the application of live prey and greenwater for improving the survival of marine fish larvae.

Survival of the swimming crab, Portunus trituberculatus , during the post-larval period from the megalopal to the first crab stage was low compared with successive larval stages in seed production trials conducted in Japan. To clarify the cause for the low survival, we explored whether rotifers, Artemia , or phytoplankton have negative effects during this period. The effects of the causative factor on larval survival and morphology were verified, and measures to overcome low survival were investigated. We conducted three experiments. In experiment 1, larvae were reared with different types of food (rotifers or newly hatched Artemia ) with or without Nannochloropsis oculata supplementation during the late zoeal period (from the third to fourth zoeal stages). After moulting to megalopae, all larvae were fed newly hatched Artemia . The somatic sizes of the last stage (fourth stage) zoeae and megalopae were large, and developmental velocity was faster in the Artemia -fed groups than that in the rotifer-fed groups. However, Artemia feeding induced unviable and morphologically abnormal first-stage crabs with close-set eyes, regardless of Nannochloropsis supplementation. In experiment 2, third stage zoeae were reared to first stage crabs with variously treated Artemia such as newly hatched, 48 h starved, and Artemia enriched with commercially available digestible Nannochloropsis with physically broken cell walls to confirm the negative effects of feeding Artemia . Larvae reared with the newly hatched and starved Artemia containing lower eicosapentaenoic acid (EPA) content exhibited low survival (1.9–3.5%) from the megalopal to the first crab stage, whereas larvae reared with Artemia enriched with digestible Nannochloropsis containing higher EPA content achieved higher survival (40.7%). In experiment 3, newly hatched Artemia were cultured under various conditions such as supplementation with untreated Nannochloropsis , digestible Nannochloropsis , or without phytoplankton to investigate what caused the Artemia to starve. The treatments supplemented with untreated Nannochloropsis and without phytoplankton suppressed Artemia growth and resulted in total mortality 4 days after hatch. Supplementing with digestible Nannochloropsis maintained Artemia growth and resulted in higher survival, suggesting that early Artemia nauplii could not digest Nannochloropsis , which resulted in starvation. Our results indicate that Artemia starve in larval rearing water regardless of supplementation with Nannochloropsis ; however, Nannochloropsis are usually added to seed production tanks. Artemia starvation during the late zoeal period exerted a negative carry-over effect during the post-larval period. We recommend nutritionally enriching Artemia with EPA and supplementing larval rearing water with digestible Nannochloropsis during the late zoeal stage. Statement of relevance Improving larval rearing techniques for producing crablets.

Live microalgal cultures have long been regarded as a bottleneck in the aquaculture industry due to their high cost and labour requirements to maintain, however, feasible alternatives to in-house cultures are limited. Microalgal concentrates, which can be shipped from a central production facility to aquaculture operations, are rising in demand due to this market niche, but they are few in number. To qualify as a viable alternative to fresh cultures, microalgal concentrates kept in basic storage conditions such as refrigeration and freezing should have a shelf life of at least 2 months, demonstrated by a stable biochemical profile over that time period. Consequently, this study tested the effect of storage condition (refrigerator and freezer) on the fatty acid and amino acid profiles of four concentrated species of microalgae: Nannochloropsis sp., Dunaliella tertiolecta, Entomoneis punctulata and Melosira dubia. The most stable products were Nannochloropsis sp. and D. tertiolecta, with no significant change in the fatty acid profile or protein content after 2 month storage in the refrigerator. The two diatoms however, were not as robust; M. dubia showed a steady decline in fatty acid content over the course of 30 days, before a marked decrease at 60 days. Although the fatty acid content of E. punctulata was stable for the first 30 days of storage, a significant decline, particularly in omega-3 content, was seen from 30–60 day storage in both the refrigerator and freezer. The total protein content, however, was stable in both species of diatoms throughout the course of the experiment. These findings suggest that Nannochloropsis sp. and D. tertiolecta concentrates could be used in aquaculture industries as a replacement or supplement to fresh cultures, whilst E. punctulata may be more suited to short-term storage, and M. dubia would perform better as a fresh culture.

In the present study, we investigated the major lipid changes of six important diet microalgae (Chlorella sp., Nannochloropsis oculata, Nannochloropsis sp., Isochrysis galbana, Phaeodactylum tricornutum Bohlin and Chaetoceros calcitrans) during the entire growth phase using UPLC-Q-TOF MS system. Our results suggested that EPA/AA-rich lipids were largely detected in both Nannochloropsis sp. and N. oculata as a component of diacylglyceryl-N,N,N-trimethylhomoserine (DGTS). Moreover, docosahexaenoic acids (DHAs) were detected only in I. galbana mainly as a component of monogalactosyldiacylglycerol (MGDG) and sulphoquinovosyldiacylglycerol (SQDG). Besides, the growth phase of microalgae could be a useful variable for the content enrichment of EFA-rich lipids. A higher content EPA/AA-rich DGTS could be obtained at the end of stationary phase for Nannochloropsis sp. and N. oculata, and a higher content of DHA-rich lipids could be obtained at the end of stationary phase for I. galbana. However, EPA/AA-rich lipids were mainly detected in both P. tricornutum and C. calcitrans mainly as a component of TAG and MGDG, respectively. In addition, a higher content of EPA-rich TAG could be obtained at the end of the stationary phase for P. tricornutum. A higher content of EPA-rich MGDG could be obtained at the end of stationary phase for C. calcitrans. Taken together, considering the high EFA requirement for artificial rearing of marine organisms, Nannochloropsis sp., N. oculata, P. tricornutum, C. calcitrans and I. galbana would be highly recommended to be harvested at the end of the stationary phase. The distribution characteristics of EFA-rich lipids related to 6 microalgae are described in detail.

Probiotics with antimicrobial properties can be used to regulate the microflora, control the pathogenic algae, and improve the mineralization of organic substances in the aquaculture environment. However, the efficacy of the probiotics on the succession of microalgae in the shrimp (Litopenaeus vannamei Boone) culture remains inadequate. A field experiment in mesocosm was performed to explore the impacts of probiotics on the succession of microalgae and nutrient enrichment of the shrimp culture systems. The enormous changes in the microalgae community structure (MCSs) was significantly influenced by probiotic colonization. Probiotics shifted MCSs into three seral phases and their sequential replacements of the dominant taxa were identified by cluster analysis. Moreover, each seral stage of the keystone species turnover in MCSs represents distinguished ecological functions. At the final seral stage probiotics significantly constrained the succession of the most competitive species of Cyanobacteria (Oscillatoria and Anabaena) which was disagreed with the normal seral stage. Similarly, the probiotics increased and maintained the sequel of the nutritional value of Nannochloropsis and Chlorella from Chlorophyta and Oocystics and Navicula from the Bacillariophyta. Furthermore, the probiotic-based ponds had a higher shrimp survival rate compared to the control. Nutrients concentration of nitrite (NO2−) and nitrate (NO3−) were lower in treatments than in the control. Consequently, chemical oxygen demand (COD), nitrite (NO2−), water temperature (WT), total ammonium nitrogen (TAN) and dissolved oxygen (DO) were strongly explanatory variables controlled the sequel of MCSs. These findings imply that the probiotics have potential in the succession, redistribution of beneficial microalgae, inhibit the growth of harmful Cyanobacteria and sustain the MCSs stability in shrimp aquaculture activities.

Microalgae are often used in the culture of the rotifer Brachionus plicatilis, which is widely used as live feed for larval fish. However, the cultivation of large quantities of unicellular microalgae to support rotifer population growth is a heavy burden on many hatcheries. The effects of artificial detritus (detritus) from the macroalgae Ulva pertusa, Undaria pinnatifida, and Chondrus ocellatus, on the population growth and nutritional content (amino acid and fatty acid composition) of B. plicatilis were evaluated as potential substitute diets. We used the microalgae Nannochloropsis sp. as comparative food. The results show that the nutritional value of the detritus from each macroalgal species is not as good as Nannochloropsis in terms of population growth, maximum population density, and population growth rate. However, when Nannochloropsis was mixed with the detritus from the other three macroalgae, for the resulting B. plicatilis populations maintained high levels and attained higher maximum population densities and population growth rates. The nutritional value of B. plicatilis fed U. pertusa detritus, specifically, the free amino acid, polyunsaturated fatty acid, and docosahexaenoic acid (DHA), were better than those fed with other diets. The DHA/eicosapentaenoic acid (EPA) ratio in rotifers fed U. pertusa detritus was the highest at 6.9 times higher than those fed Nannochloropsis. Therefore, the detritus of macroalgae, especially U. pertusa, is an appropriate substitute diet, at least partly, for the culture and dietary enrichment of B. plicatilis.

Nannochloropsis oculata is widely used in grouper larvae hatcheries for the production of green water to stabilize water quality, provide shielding for light-sensitive fish larvae, and breed super-small rotifers (SS-rotifers), the first feed of grouper larvae. However, the practical use of N. oculata is hindered by an insufficient yield of this alga. This study evaluated Picochlorum strain S1b, an indigenous marine microalga capable of cultivation at high growth rates, to determine its suitability as an alternative to N. oculata in grouper larvae hatcheries. Feasibility was evaluated mainly according to two parameters: 1) the nutritive value of the microalga for SS-rotifers; and 2) the nutritive value of SS-rotifers for grouper ( Epinephelus coioides ) larvae. The nutritive value of algae was evaluated by comparing the proliferation rate and egg ratio of SS-rotifers. The nutritive value of SS-rotifers was evaluated by comparing the size and amino acid composition of SS-rotifers feeding on different microalgae. We also examined the “green water effect”, i.e., changes in the vibrio community in the rearing tank following the introduction of microalgae, as well as its influence on the survival and growth rates of grouper larvae. In these experiments, S1b provided the highest nutritive value for SS-rotifers, particularly when grown under mixotrophic conditions (S1b [mixo]). The cultivation of SS-rotifers using S1b [mixo] increased the percentage of small-size organisms, which are highly suitable as first feed for grouper larvae; and cultivation with S1b [mixo] altered the amino acid composition of SS-rotifers to more closely match that of grouper larvae, thereby enhancing their nutritive benefits. Green water produced with either Picochlorum S1b or N. oculata was shown to inhibit the blooming of vibrio, an opportunistic pathogen of fish. Grouper larvae reared in green water produced with Picochlorum S1b had the same survival rate but a higher growth rate than those reared in green water produced with N. oculata . These results demonstrate the potential benefits of replacing N. oculata with Picochlorum S1b for the rearing of grouper larvae.

Experimental diets were processed by supplementing either whole algae or algae fractions to a formulated control diet to test their effects on growth, survival and composition of juvenile shrimp ( Litopenaeus vannamei ). Diatom ( Thalassiosira weissflogii ) and Nannochloropsis cultures were freeze-dried and partially extracted with acetone into a carotenoid fraction and a residue fraction. Seven diets were prepared by individually adding whole diatoms ( T. weissflogii ), whole Nannochloropsis , a combination of the whole diatoms and Nannochloropsis , their carotenoid fraction, or their residue fraction, to a control diet. After the eight-week feeding trial, shrimp fed diets containing either the whole diatoms, whole Nannochloropsis , a combination of the two, or their residue fractions, achieved higher ( P − 1 ) and survival rates (93.8 to 100%) than those fed the control diet (0.46 g week − 1 ; 79.2%). This enhanced growth effect might not be attributable to the macronutrient composition of the microalgae, because their addition reduced the levels of crude protein, crude lipid, and gross energy in the control diet. The growth rate of shrimp fed diets containing the carotenoid fraction of the diatoms and Nannochloropsis (0.54 and 0.47 g week − 1 ) was similar ( P > 0.05) to that of shrimp fed the control diet. The addition of whole algae also increased the fatty acid and astaxanthin contents of shrimp tail muscles. The improved growth rates indicate the potential advantages of using dried algae as a feed additive, and the benefits of developing phytoplankton in shrimp ponds.

The present study investigated the effects of microalgae Nannochloropsis sp. addition and concentration on larval survival, development and growth of an Australian strain of M. rosenbergii (lineage II). Newly hatched larvae were reared to postlarval (PL) stage under the condition of no algae addition (‘clear water’) and four Nannochloropsis concentrations of 2.5, 6.25, 12.5 and 25 × 105 cells/ml. All treatments were in quadruplicate and each replicate had 30 larvae stocked in a 5L vessel. Larvae were fed 3 Artemia/ml throughout with 100% water exchange daily. The results showed that larval survival to PL at the two higher algae concentrations of 12.5 and 25 × 105 cells/ml (70.8 and 63.3%, respectively) were significantly higher (P < 0.05) than those of lower algae concentrations of 2.5 and 6.25 × 105 cells/ml and the ‘clear water’ treatments (26.7, 35.0 and 30.0%, respectively). Meanwhile, the fastest mean development to PL (30.6 days) registered at the highest algal density was 14 days shorter than that of the ‘clear water’ treatment (44.3 days). Larval development at the two higher algal densities were significantly shorter than that of the ‘clear water’ treatment and larval development of the highest algal density was further significantly faster than those of the two lower algal densities (40.1 and 40.0 days) (P < 0.05). The mean dry weights of newly settled PL of the two high algal density treatments were also significantly heavier (P < 0.05) than those of the lowest algal density and the ‘clear water’ treatments. The results have shown that the addition of Nannochloropsis sp. at appropriate levels substantially improved performance of larval culture of the Australian strain of M. rosenbergii, suggesting that the Australian native strain has a promising potential for aquacultural development.

In vitro culture of the ascidian Ecteinascidia turbinata is one possible method for supplying ecteinascidins, compounds that have strong antitumor properties. However, appropriate feeding regimes that maximize both zooid growth and biosynthesis of ecteinascidins need to be determined. In one experiment lasting 51 days, E. turbinata colonies were fed mono- and multispecific diets of three microalgae species, Chaetoceros gracilis , Isochrysis galbana , and Nannochloropsis sp., at an initial concentration of 80,000 cells ml −1 . Growth (zooid number per colony and mean zooid length) was greatest overall for colonies fed a monospecific diet of I. galbana or a mixed diet of C. gracilis and I. galbana , probably because these two diets best met the nutritional requirements of E. turbinata . In a separate experiment lasting 31 days, E. turbinata colonies were fed the two best diets at three cell concentrations: 80,000; 160,000; and 320,000 cells ml −1 . Final zooid number per colony was greatest for E. turbinata fed the two highest food concentrations, while final zooid length was greatest on the mixed diet of C. gracilis and I. galbana . The production of ecteinascidins per colony (μg) was also significantly affected by the feeding regime, being greatest for ascidians fed microalgae at 160,000 and 320,000 cells ml −1 . Ecteinascidin production for ascidians fed at the two highest cell concentrations showed a tenfold increase over 31 days, thus indicating that in vitro culture is one possible method of supplying the antitumor compound. Overall, this study suggests that a mixed diet of C. gracilis and I. galbana at a concentration of 160,000 cells ml −1 is a good feeding regime for the in vitro culture of E. turbinata to supply ecteinascidins.

A flat plate (10 cm light-path), vertical reactor made of 10-mm glass plates glued together to form a 500- to 1000-l unit was developed for outdoor production of Nannochloropsis sp., one of the most promising photoautotrophic producer of eicosapentaenoic acid (20:5ω3, EPA) for aquaculture. The energy inputs required for mixing and cooling the culture were calculated and the harvesting regime yielding the highest areal output of cell mass and EPA was identified. The reactor is practically sealed, facilitating successful maintenance of continuous, monoalgal cultures throughout the year. The optimal cell density fell in the range of 5 to 6×10 8 cells ml −1 , a high cell concentration compared with that reported for other mass production systems of Nannochloropsis . This population density yielded in continuous cultures throughout the year an average of 12 g dry cell mass m −2 day −1 or 650 mg EPA m −2 day −1 , on the basis of the entire illuminated reactor area. An economic appraisal is provided for operating a 2000-l reactor, sufficient to supply all the algal mass for production of the rotifer quantity required by a Seabream hatchery producing 8×10 6 fingerlings annually. The production cost at this rather modest scale shows strong sensitivity to the cost of labor.

Provision of copepod nauplii as food increases larval survival in many fish species that are difficult to rear using standard practices. Gladioferens imparipes is a temperate estuarine calanoid copepod with culture potential. Diets were tested to determine which would maximise copepod production. Copepods were fed five diets: Isochrysis galbana, Chaetoceros muelleri, Dunaliella tertiolecta, Nannochloropsis oculata and baker's yeast. Copepod survival, time to maturity, maturation rate, nauplius production and female length were recorded at 20°C and 25°C. By most criteria, Isochrysis was the most efficacious diet, followed by Chaetoceros and then Dunaliella. Nannochloropsis and yeast resulted in little or no survival. Fatty acid profile of each diet was determined. In general, copepod production was positively related to the ratio of DHA:EPA in their diet. Poor survival on Nannochloropsis was probably a result of the small cell size and poor digestibility of this species.

Four Australian microalgal isolates ( Pavlova pinguis , Rhodomonas salina , Tetraselmis sp. CS-362 and Nannochloropsis -like sp. CS-246) were compared to an overseas isolate ( Isochrysis sp. (T.ISO)) to assess their potential as food for bivalve aquaculture. When fed to Pacific oyster spat, the best growth was observed with a mixed diet comprising the four Australian species plus Isochrysis sp. (T.ISO) (161% increase in organic weight over 21 days). The best growth using the monospecific diets was produced by P. pinguis (111% increase), followed by Isochrysis sp. (T.ISO) and R. salina (85% and 82%); then Tetraselmis sp. CS-362 (51%), and Nannochloropsis -like sp. CS-246 (35%). The growth rates (based on an increase in organic weight) of oysters fed the monospecific diets were correlated to the amounts of protein and carbohydrate they ingested. The gross biochemical composition of the microalgae grown in semicontinuous culture differed significantly. Protein ranged from 48% of the dry weight ( R. salina ) to 17% ( Nannochloropsis -like sp. CS-246); carbohydrate ranged from 41% ( P. pinguis ) to 22% ( R. salina ); and lipid from 16% ( Tetraselmis sp. CS-362) to 26% ( Nannochloropsis -like sp. CS-246). The instantaneous growth rate ( μ ) of Isochrysis sp. (T.ISO) ( μ =0.48 day −1 ) was greater than the Australian strains, the best of which was R. salina ( μ =0.37).

The eustigmatophyte Nannochloropsis is widely used in many aquaculture hatcheries to establish the initial step of an artificial food chain. The advantage of Nannochloropsis over other unicellular algae is primarily its unique fatty acid composition. Rotifers which consume the algae carry these fatty acids to the fish larvae. Cultivation of large quantities of algal biomass to support this food chain is a heavy burden in many hatcheries, and in many other locations it cannot be carried out all year round. In this study we examined the possibility of substituting frozen biomass for fresh Nannochloropsis as a sole food source for rotifer cultures or as an enrichment treatment prior to feeding the rotifers to the larvae. Relatively high reproductive rates were found in rotifers of three strains which were fed frozen Nannochloropsis biomass. Total fatty acid content of these rotifers and fatty acid distribution were related to the chemical composition of the algae. Although seasonal variations in biochemical composition and fatty acid distribution were found in the algal biomass, the quality of the long-term frozen algae was adequate to provide the rotifers with the essential fatty acids almost all year round. No differences were found in the fatty acid composition of rotifers fed with algae stored at − 20 °C or − 70 °C. The thawed algal biomass could be kept at 4 °C for 7 days and be used for rotifer feeding without a significant adverse effect on the fatty acid content and composition in the rotifers. The results of this study suggest that application of frozen Nannochloropsis biomass may promote easier management in biomass production of lipid-enriched rotifers. This provides the artificial food chain with essential fatty acids, which are crucial for the development and cultivation of fish larvae, with a relatively limited effort for algae production on the hatchery site.

The eustigmatophyte, Nannochloropsis sp., contains relatively large amounts of valuable lipids and is commonly grown as food source for commercial application in aquaculture. In this study we evaluated the effect of environmental conditions such as light intensity, nitrogen availability and temperature on cellular chemical composition with special emphasis on fatty acid distribution in cultures of Nannochloropsis sp. continuously grown under laboratory-controlled conditions. Seasonal variations in cellular chemistry were further assessed using large-scale outdoor shallow ponds, aimed at mass production of Nannochloropsis for application in an aquaculture hatchery. The percentage of the polyunsaturated long-chain fatty acid, eicosapentaenoic acid, in the algal biomass varied between 1.6 and 3.8% (w/w). In spite of significant variations in cellular protein content, the amino acid composition of Nannochloropsis biomass remained fairly constant during the different production seasons. Variations in the fatty acid composition of the algal biomass are attributed to differences in seasonal climatic conditions and diurnal cycles in light intensity and temperature. This study demonstrates the feasibility of culturing algal biomass of a high chemical quality for various applications in aquaculture hatcheries.

The rotifer ( Brachionus plicatilis Muller) was cultured on phytoplankton monocultures ( Dunaliella tertiolecta, Tetraselmis suecica, Nannochloropsis sp., Phaeodactylum tricornutum ), natural nanoplankton and baker's yeast. Biochemical composition of rotifers harvested at exponential, stationary and death phases was determined. The moisture content declined in all samples in their stationary phase of growth. Ash levels were highest at the death phase. Lipids and carbohydrates were observed to decline between the exponential and the death phases. Protein levels increased in the stationary phase. Growth rate, doubling time, lipid, carbohydrate and protein content of rotifers fed Phaeodactulum tricornutum and Nannochloropsis sp. indicate that these monocultures are the most suitable diets for the rotifer. Rotifers fed on these algae are expected to satisfy the nutritional demand of fish larvae.

The requirement for dietary ( n −3) PUFA for growth, survival and swim bladder development in gilthead seabream, Sparus aurata , larvae was tested using rotifers with various levels of ( n −3) PUFA. Four rotifer treatments differing in their ( n −3) PUFA content (0.8, 3.2, 5.1 and 8.4 mg/g dry body weight, DBW) were prepared by feeding them combinations of various oil emulsions and dried squid (rich in both EPA (20:5 n −3) and DHA (22:6 n −3)). A fifth treatment consisted of rotifers enriched on the algae Nannochloropsis sp. Regression analyses, from the emulsion treatments, were performed on various relationships between rotifer ( n −3) PUFA levels and larval phospholipid and growth. The equations describing these correlations were then used to examine whether the same parameters in larvae fed Nannochloropsis -enriched rotifers were a result of the dietary ( n −3) PUFA levels they consumed or some other nutritional factor. The results indicate that dietary ( n −3) PUFA significantly ( P n −3) PUFA (8.4 mg/g DBW) showed a four-fold increase in growth (1263% vs. 312%) over larvae offered rotifers with the lowest levels of ( n −3) PUFA (0.8 mg/g DBW). In contrast, there was no compelling evidence that EPA and/or DHA significantly ( P Nannochloropsis treatment was strongly associated with EPA and implies that, despite other sources of nutrition in the algal media, this fatty acid determines the dietary value of these rotifers for growth in Sparus aurata larvae.

Growth and productivity of marine microalgae, Chlorella Strain MFD-1 and Nannochloropsis Strain MFD-2, in an intensive continuous culture system using 200-1 capacity translucent vertical air-lift tubular photobioreactors is described. Using a culture surface irradiance of 330 μE m−2 s−1 and at a controlled pH of 6.5 and 7.0, the productivity varied between 109 and 264 g m−3 d−1 with a mean of 169.7±34.7 g m−3 d−1 for Chlorella Strain MFD-1 and between 32.5 and 95.3 g m−3 d−1 with a mean of 50.6±14.2 g m−3 d−1 for Nannochloropsis Strain MFD-2. The productivity of microalgae in relation to different light intensities is discussed. The fatty acid composition, especially the ω3 Highly Unsaturated Fatty Acids (ω3 HUFA), of these microalgae is species-dependent in the culture system. The total ω3 HUFA and the essential fatty acid eicosapentaenoic acid (EPA) content were significantly higher (P

In order to obtain suitable species of microalgae for mass production for aquaculture in Kuwait, algal isolates from local sea water were studied. During the process of isolation, microalgae belonging to the genera Chlorella and Nannochloropsis were obtained and have been designated as Chlorella strain MFD-1 and Nannochloropsis strain MFD-2. The growth, fatty acid and amino acid composition of these microalgae at temperatures of 15, 20, 25, 30 and 35°C are evaluated and discussed. The investigations show that the instantaneous growth rate, fatty acid and amino acid composition of these algae depend on the temperature utilized in the culture system, and also show variations between different species of microalgae utilized.

An automated intensive continuous culture system, based on the principles of a chemostat, for producing two strains of the rotifer Brachionus plicatilis (L and S-type) has been investigated. Using 1-m3 capacity fiberglass tanks, it was possible to achieve a mean production of 308.75 × 106 individuals m−3 day−1 of S-type rotifers and 186.71 × 106 individuals m−3 day−1 of L-type rotifers in the culture system. The rotifers were fed with a local microalgal isolate Nannochloropsis strain MFD-2 which was produced using algal chemostats. Bakers' yeast was used as a feed supplement. The results show that the rotifer productivity in the continuous culture system is considerably higher than in any of the conventional culture systems described to date for aquacultural purposes. Furthermore, ω3-fatty-acid composition of rotifers in the culture system shows that these rotifers contain adequate quantities of essential fatty acids required for marine fish larvae and no further nutritional enrichment is necessary.