Comparison of Growth and Fatty Acids Composition of Freshwater Rotifer, Brachionus calyciflorus Pallas, Fed with Two Types of Microalgae at Different Concentrations

As algae and their concentrations are important factors for mass culture of rotifer, two experiments were conducted to find the effects of two types of algae, Chlorella sp. and Scenedesmus obliquus, and three concentration of chosen algae (0.1 × 10⁶, 1 × 10⁶, and 10 × 10⁶ cells/mL) on growth and fatty acid composition of freshwater rotifer, Brachionus calyciflorus. The result of the first experiment showed that the maximum density of rotifer was significantly higher when fed with Chlorella sp. (478 individuals/mL) than fed with S. obliquus (328 individuals/mL). Mean population growth rate (r) was 0.61 and 0.44 for rotifer fed with Chlorella sp. and S. obliquus, respectively. The amount of highly unsaturated fatty acid (HUFA) in rotifer fed with Chlorella sp. (3.32%) was relatively more than those fed with S. obliquus (2.65%). Then, Chlorella sp. was selected based on better performance. In the second experiment, the maximum rotifer density of 108 ± 8, 489 ± 47, and 493 ± 51 individuals/mL was reached after 5 d for the respective Chlorella sp. concentrations; at concentration of 10 × 10⁶ cells/mL, the maximum density of 1820 ± 47 individuals/mL was obtained. Mean growth rate at mentioned concentrations was 0.18, 0.42, and 0.51/d, respectively. Increase in algal concentration was associated with a relative increase in HUFA and decrease in monounsaturated fatty acid.     

Effects of Microalgae and Alfalfa Meal on Population Growth and Production of a Freshwater Rotifer,Euchlanis dilatata (Rotifera: Mongononta)

Population growth and production of the freshwater rotifer, Euchlanis dilatata, were determined after being fed 1 of 12 diets: Scenedesmus quadricauda (S), Chlorella vulgaris (C), baker's yeast (Saccharomyces cerevisiae) (Y), alfalfa meal (Medicago spp.) (A), and eight combinations of S+C, S+Y, C+Y, S+C+Y, S+A, C+A, S+C+A, and Y+A (mixture in the same ratio by equal nitrogen weight). Results showed that both microalgal and alfalfa meal alone and in combination with Y had a significantly higher (P < 0.05) population growth and production compared with Y alone. The mean maximum E. dilatata population density fed on S, S+Y, C, C+Y, S+C, S+C+Y, Y, A, S+A, C+A, S+C+A, and Y+A diets were 65 ± 7.5 (mean ± SE), 124.6 ± 17.2, 115.8 ± 7.9, 41.5 ± 7.9, 131 ± 14.1, 93.5 ± 8.7, 14.5 ± 7.6, 129.5 ± 18.5, 255.0 ± 20.5, 180 ± 30.5, 124.5 ± 25.4, and 61.5 ± 24.5 individuals/mL, respectively. Correspondingly, the mean population growth rates (K) through the 16‐d culture period were 0.29, 0.40, 0.45, 0.27, 0.34, 0.41, 0.26, 0.51, 0.58, 0.59, 0.39, and 0.45/d, respectively. Results indicated that alfalfa meal in combination with microalgae and yeast could be used as primary diets for E. dilatata culture. This may reduce the costs of rotifer production.     

Production and Nutritional Quality of Two Small-Sized Strains of the Rotifer Brachionus plicatilis1

The rotifer Brachionus glicatilis, strain-S (from Japan) and strain-S1 (Pozuelo 1975) were mass cultured using Chlorella and bakers' yeast. Under the same feed regime, a significant increase (P < 0.001) in rotifer strain-S production (44.19 ± 8.50 individuals/mL/d) was observed compared with strain-S1 (29.64 ± 9.38 individuals/mL/d). The population growth rate was significantly higher (P> 0.001), and doubling time was significantly lower (P> 0.0001) in rotifer strain-S than in strain-S1. There was a significant decline (P> 0.001) in birth rate of strain-S rotifers in the culture system compared with strain-S1, suggesting short longevity and deterioration of the culture system while using strain-S. In general, no significant difference (P< 0.05) in the presence of ω3 polyunsaturated fatty acids (ω3 PUFA) in different strains of rotifers was observed.     

Fundamental studies on the physiology of rotifers in mass culture—V. Dry Chlorella powder as a food for rotifers

The dietary value of dried, commercial Chlorella was compared with that of living marine Chlorella, and yeast, in relation to growth of the rotifer Brachionus plicatilis raised individually and by batch culture methods.A concentration of 50 μg/ml of dried Chlorella powder is near an optimal density for rotifer growth. The dried material in suspension is less effective for growth than living marine Chlorella, although it is much more effective than a suspension of yeast at the same density (50 μg/ml).In batch culture (12-l glass vessel), the rotifers grew from an initial inoculation of 13.2 individuals/ml to a density of 434 individuals/ml by the 16th day. About 10⁷ rotifers could be removed from one batch culture in five harvests in the 41-day experimental period.The results indicate that dried Chlorella powder is an effective food for the rotifer Brachionus plicatilis.     

Evaluation of First-Feeding Regimens for Larval Nassau Grouper Epinephelus straitus and Preliminary, Pilot-Scale Culture through Metamorphosis

Two 10-day hatchery experiments were conducted to evaluate s-type (Hawaiian strain) and ss-type (Thailand strain) rotifers Brachionus plicatilis and cryogenically preserved oyster Crassostrea gigas trochophores as first feeds for larval Nassau grouper Epinephelus striatus. Newly hatched grouper larvae were reared at densities of 11.2–20.8/L in 500-L tanks at 36–38 ppt salinity, 25–26 C, and under a 11-h light: 13-h dark photoperiod. Beginning on day 2 posthatching (d2ph), prey were maintained at a density of 20 individuals/mL, while phytoplankton (Nanochloropsis oculata) was maintained at 500 × 10³ cells/mL. In experiment 1, survival and growth were higher (P < 0.05) for fish fed small s-type rotifers (mean lorica length = 117 μm; fish survival = 7.96%) selected by sieving than for fish fed non-selected rotifers (mean lorica length = 161 μm; fish survival = 2.13%). These results demonstrated the advantage of small prey size and suggested that super-small (ss-type) rotifer strains would be beneficial. In experiment 2, three feeding regimens were compared: 1) ss-type rotifers (mean lorica length = 147 μm); 2) oyster trochophores (mean diameter = 50 μm) gradually replaced by ss-type rotifers from d5ph; and 3) a mixed-prey teatment of 50% oyster trochophores and 50% ss-type rotifers. Survival was higher (P < 0.05) for larvae fed mixed prey (15.6%) than for those fed rotifers (9.73%) or trochophores and rotifers in sequence (2.55%), which also showed the slowest growth. Oyster trochophores, although inadequate when used exclusively, enhanced survival when used in combination with rotifers, possibly by improving size selectivity and dietary quality. In a pilot-scale trial, larvae were cultured through metamorphosis in two 33.8-m³ outdoor tanks. Fertilized eggs were stocked at a density of 10 eggs/L and larvae were fed ss-type rotifers from d2ph-d20ph, newly hatched Artemia from d15ph-d18ph, 1-d-old Artemia nauplii from d18ph-d62ph. Survival on d62ph was 1.17%, with a total of 5,651 post-metamorphic juveniles produced.     

Growth, filtration and ingestion rate of the rotifer Brachionus plicatilis fed with large (Asteromonas gracilis) and small (Chlorella sp.) celled algal species

The rotifer Brachionus plicatilis was fed in experimental conditions with a small celled (2–5 μm) Chlorella sp. and a large celled (16–22 μm) Asteromonas gracilis algae. The specific growth rate (SGR) of rotifers fed Asteromonas (maximum 0.79) was statistically higher than that for rotifers fed Chlorella (maximium 0.61). The filtration and ingestion rates using different rotifer and algal densities exhibited certain maxima depending on the species, the cell density and the condition of the rotifers. The filtration rate was higher with Asteromonas and, although ingestion rate was lower than with Chlorella, the ingestion in terms of cell volume was 10‐fold higher. It seems that B. plicatilis ingests the larger cell diameter algal species more efficiently than the smaller species that is usually used for its mass culture.     

Effects of astaxanthin on Brachionus manjavacas (Rotifera) population growth

Astaxanthin is a red secondary carotenoid and powerful antioxidant that is used in aquaculture to enhance colour and improve fish health. Brachionid rotifers are often used as a live feed for larval fish, but do not contain endogenous carotenoids. However, they can be enriched with astaxanthin through their diet and transfer it to larval predators. When supplemented with 2 μg/ml astaxanthin oleoresin extracted from the green alga Haematococcus pluvialis, Brachionus manjavacas rotifer cultures reached significantly higher population densities and maintained them for longer. Furthermore, data are presented that exposure to oleoresin or pure astaxanthin enhances rotifer resistance to oxidative stress, a common cause for the collapse of rotifer mass cultures. Astaxanthin can be visualized in the gut of the rotifers, allowing the time course of uptake to be estimated by image analysis. Using this method, it was found that accumulation of astaxanthin in the rotifer gut saturates after 1.5 hr of exposure. The bioactive dose of astaxanthin oleoresin for rotifers was found to be 1–20 μg/ml. Astaxanthin concentration in rotifer tissues was measured using absorbance spectrophotometry. It was found that treating rotifers with 20 μg/ml for 24 hr; the concentration of astaxanthin absorbed into rotifer tissues was 2.6 mg/g. Overall, these experiments indicate that astaxanthin extracted from H. pluvialis can be used to improve the productivity and stability of rotifer mass cultures by increasing oxidative stress resistance and enhance the nutritional content of rotifers for larval fish.     

Effect of different algae used for enrichment of rotifers on growth, survival, and swim bladder inflation of larval amberjack Seriola dumerili

The effect of algae with different DHA contents used for the enrichment of rotifers on the growth performance, survival, and swim bladder inflation of larval amberjack Seriola dumerili was investigated. Rotifers were enriched with freshwater Chlorella vulgaris containing three levels of DHA (rotifer containing DHA 0.04, 0.60, 1.32?g DHA 100?g^?1 DM) and Nannochloropsis (0.04?g DHA 100?g^?1 DM; 2.54?g EPA 100?g^?1DM). The larvae were fed the enriched rotifers in triplicate from 3?days post-hatch for 7?days in static condition. The same algae used for rotifer enrichment were supplied to the larval tanks. Growth and survival rate of fish fed the rotifers enriched with Nannochloropsis were higher than those of fish fed the rotifers enriched with all three Chlorella treatments. Swim bladder inflation was lowest in fish fed the rotifers enriched with Nannochloropsis. The proportion of EPA was higher in fish fed the rotifers enriched with Nannochloropsis, while that of DHA increased proportionally with the DHA levels in the rotifers enriched with Chlorella. These results suggest that rotifers enriched with Nannochloropsis (EPA-rich rotifers) are effective to enhance growth and survival, but DHA instead of EPA is essential to improve the swim bladder inflation in amberjack larvae.     

维生素B12对圆型臂尾轮虫种群增长、繁殖和个体大小的影响

为了解维生素B 12 对海水圆型臂尾轮虫( Brachionus rotundiformis )种群增长、繁殖和个体大小的影响,采用四种不同浓度的维生素B 12 (0、0.3、0.6、1.2 μg/mL)强化培养轮虫7 d。每天测定轮虫的种群密度和怀卵率,每隔一天测定轮虫背甲长和宽。试验结果显示:0.3 μg/mL维生素B 12 组轮虫的种群增长、怀卵率显著高于其他组( P<0.05);0.3 μg/mL维生素B 12 组轮虫的背甲长和宽均显著小于其他三组( P>0.05),而其他三组差异不显著。试验结论:在本试验条件下,维生素B 12 对圆型臂尾轮虫种群增长、繁殖和个体大小影响的最适浓度为0.3 μg/mL。     

Enhancing rotifer Brachionus calyciflorus population growth with commercial probiotics

The effect of a commercial probiotic (NanoCrusta, Altacrusta, Mexico City, Mexico) on the growth performance of Brachionus calyciflorus Pallas, 1766, was evaluated. In a first approach, probiotics were supplied in four densities (2.0 × 10³, 1.1 × 10⁵, 2.1 × 10⁵ and 2.1 × 10⁶ cells/ml), alone and in combination with Chlorella vulgaris (1 × 10⁶ cells/ml). The test rotifer did not grow on the probiotic alone. However, when probiotics + C. vulgaris were added, the maximum densities (D_max; ind/ml) and population growth rates (r) observed were higher. In the second experiment, probiotics were supplied at five higher densities (2.1 × 10⁶, 4.2 × 10⁶, 8.5 × 10⁶, 1.7 × 10⁷ and 3.4 × 10⁷ cells/ml) with C. vulgaris and a control treatment with only C. vulgaris (probiotic‐free). Treatments supplied with probiotics between 2.1 × 10⁶ and 1.7 × 10⁷ cells/ml showed significantly higher D_max and r than the control treatment. The results showed a positive effect of probiotic bacteria when supplied with C. vulgaris. The best outcome showed a D_max 2.16 times and an r 1.63 times higher than the density of the control treatment. Growth rates were higher in the treatments with probiotics compared to the control. We conclude that application of NanoCrusta is feasible to improve B. calyciflorus production, but the effects need to be tested in larger scales.     

Intensive Rotifer Production in a Pilot‐scale Continuous Culture Recirculating System Using Nonviable Microalgae and an Ammonia Neutralizer

A study was conducted to test the performance of a high‐density (>3000 individuals/mL) continuous recirculating system for rotifers (B. rotundiformis) fed nonviable Nannochloropsis oculata and using sodium hydroxymethanesulfonate to neutralize ammonia. Three different microalgae feed rates (g of N. oculata [68 × 10⁹ cells/mL] per million rotifers/d) were tested in successive trials. In Trial 1 (feed rate = 1.5), during a 30‐d period, rotifers were harvested daily to 3000 individuals/mL, for an average yield of 178 million/d. Feed efficiency (million rotifers/g/d) was 0.33. In Trial 2 (feed rate = 1.1), during a 32‐d period, an average of 106 million rotifers were harvested daily, and feed efficiency was 0.26. In Trial 3 (feed rate = 1.3), during a 30‐d period, an average of 107 million rotifers was harvested daily, and feed efficiency was 0.23. An economic analysis based on a feed rate of 1.5 showed that production cost was 40% lower than the traditional batch culture method (US$ 0.29 vs. 0.46 per million rotifers/d). The continuous culture system tested reliably produced large quantities of rotifers on a daily basis without the use of a biofilter and with a lower production cost than a batch culture system.     

Channel Catfish,Ictalurus punctatus,Immunity to Saprolegnia sp.

ABSTRACT

The Japanese flounder, Paralichthys olivaceus, is one of the most common finfish cultured in Japan and Korea. Despite the relatively high production of fingerlings, some problems remain, mainly related to the larval feeding and cost of maintaining microalgae and rotifers. In order to determine the effects of different diets on the Japanese flounder larval growth and survival, a series of experiments was carried out related to the size and nutritional value of different live feeds. The larvae culture conditions were at 10 or 20 larvae/L in 50 to 2,000 L tanks, with aeration and with or without “green water,” and a temperature range of 18.5 to 22.5°C. The live foods used were microalgae (Chlorella ellipsoidea and Nannochloris oculata), baker's yeast, experimental n-yeasts, oyster trochophore larvae, three strains of rotifer Brachionus plicatilis (L-type, S-type and U-type) and Artemia nauplii. Variations were detected in size, dry weight, and chemical composition of the three strains of rotifers used. The maximum number of rotifers ingested by flounder larvae increased steadily from 7 individuals, at first feeding (3.13 mm), to 42 individuals at 5.25 mm of total length (6 days after first feeding). There was a relationship between larval total length and size of the rotifers ingested. The effect of rotifer size on larval growth and survival appeared to be limited to the first two days of feeding. Of the diets tested in the growth and survival of larval flounder during 14 days after hatching, rotifers fed on C. ellipsoidea and raised in green-water gave the best results. Rotifers cultured on enriched N. oculata and n-yeasts did not support larval growth and caused higher mortalities. The n-yeasts used as rotifer enrichment appeared to satisfy, partially, the nutritional requirement of 7-day-old flounder larvae, as did n-yeast squid wintering oil the requirements of 14-day-old larvae. From 7-9-days after hatching and throughout the second 14-day period, rotifers and Artemia cultured on N. oculata improved the survival of flounder compared with those fed on rotifers cultured on C. ellipsoidea. Moreover, the larval growth did not vary significantly between both microalgae-rotifer feedings. No clear relation was found between total protein, lipid, amino acids and fatty acids of live feeds with the growth and survival of flounder larvae, although the total lipid was higher in C. ellipsoidea than in N. oculata. The Artemia nauplii San Francisco strain appeared to be more suitable for the growth and survival of flounder larvae, than the Utah strain. The nutritional value of Artemia nauplii (Utah strain) for flounder larvae remained unchanged despite the use of either microalgae as nauplii enrichment.     

Waste‐grown phototrophic bacterium supports culture of the rotifer,Brachionus rotundiformis

The present and commonly used batch culture system (BCS) as adopted by many small‐scale tropical hatcheries is beset by poor rotifer production and sudden crashes. This study aimed to produce nutritive rotifers and evaluate their performance based on the BCS by using phototrophic bacteria (PB) that can be easily and cheaply cultured from palm oil mill effluent (POME), an agro‐industrial byproduct usually discarded as waste. Brachionus rotundiformis given a sole diet of POME‐grown PB (Rhodovulum sulfidophilum) grew as well as on the commercially produced microalgae, Nannochloropsis. Production, growth rate and fecundity of rotifers fed condensed bacterial cells (bPB) and culture broth of bacteria grown in POME (cPB) were evaluated. The best performance in terms of the stated parameters was obtained for rotifers fed 200 mL of cPB in 3 L of culture water; this media sustained a mean rotifer density of 600–900 individuals mL^?1 after 3–6 days of culture. The biochemical composition of rotifers fed PB was comparable to those fed microalgae, except that the former contained more polyunsaturated fatty acids.     

Nutritional value and production of three species of purple non‐sulphur bacteria grown in palm oil mill effluent and their application in rotifer culture

Three species of purple non‐sulphur bacteria (PB), Rhodopseudomonas palustris, Rhodobacter sphaeroides and Rhodovulum sulfidophilum, grown in palm oil mill effluent (POME) were successfully used for the first time as feed for rotifers (Brachionus rotundiformis). Rp. palustris cultured in both POME and synthetic medium gave the highest rotifer density (332–395 individuals mL⁻¹) from 3 to 5 days at 10 g L⁻¹ salinity. Other PB cultured in synthetic medium generally support higher rotifer density than PB cultured in POME. Rb. sphaeroides had the highest biomass (1.91–3.34 g L⁻¹) and growth rate (0.64–1.11 g day⁻¹) in both types of culture medium. Nevertheless, only Rv. sulfidophilum grown in POME contained both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), indicating its ability to biosynthesize them from POME nutrients. Rotifers fed Rv. sulfidophilum grown in POME had significantly higher amounts of protein, arachidonic acid, EPA and DHA than rotifers fed Rv. sulfidophilum grown in synthetic medium. The nutritional profile of lipid‐deficient PB can be improved by growing them in POME, and these enriched PB produced at an estimated cost of USD 8.71–35.35 kg⁻¹ dry biomass, depending on species, can support rotifer production in a batch culture system.     

Isolation and culture of the marine rotifer, Colurella dicentra (Gosse, 1887), from a Mississippi Gulf Coast estuary

Few marine rotifer species (e.g. Encentrum linheii and Synchaeta cecilia) have been cultured successfully besides Brachionus plicatilis and B. rotundiformis, commonly used to rear larvae of many marine fish species. The development of culture techniques for marine rotifers smaller in size than the Brachionus species may be useful for rearing fish species for which the currently used prey are too large. We evaluated the possibility of culturing Colurella dicentra isolated from a Mississippi Gulf Coast estuary. An experiment was conducted to determine the effects of salinity (10–35 g L^?1) on its population growth rate. Rotifers were fed Nannochloropsis oculata at a density of 100 000 cells mL^?1 for 15 days. Colurella dicentra survived in water with a salinity of 10–47 g L^?1. Densities of up to 300 rotifers mL^?1 were sometimes attained in cultures. Salinity influenced C. dicentra production (P<0.001). The mean rotifer numbers at 10 g L^?1 (22 840±2604 SD), 15 g L^?1 (25 980±7071 SD) and 20 g L^?1 (19 780±1029 SD) at the end of the experiment were similar (P>0.05), but were higher (P=0.05) than numbers at 25 g L^?1 (4240±1783), 30 g L^?1 (1300±264 SD) and 35 g L^?1 (100±101 SD). The population growth rate (r) of the rotifers was the highest at 15 g L^?1 (0.37–0.42 day^?1), and the lowest at 35 g L^?1 (?0.33–0.06 day^?1). This is the first report of C. dicentra in the estuarine waters of the Gulf of Mexico, and also the first time it has been cultured successfully.     

Elimination of the associated microbial community and bioencapsulation of bacteria in the rotifer Brachionus plicatilis

The bioencapsulation of live bacteria in the rotifer Brachionus plicatilis was determined under monoxenic conditions. The first objective was to evaluate the microbiota of the rotifer during intensive production and to obtain sterile rotifer cultures starting from adult females or amictic eggs using PVP-Iodine, Hydrogen peroxide or antibiotic mixtures. In the rotifers, the proportion of vibrios increased significantly during the mass production, displacing other unidentified marine bacteria. Rotifers, in the absence of culturable bacteria were obtained starting from amictic eggs and using Trimetroprim-sulfametoxasole (Bactrim Roche®) at 10 ml l^–1. The effect of members of Vibrionaceae on the survival and growth rate of rotifers was determined under monoxenic conditions. The survival of rotifers was not affected in the presence of different isolates, while amictic egg formation occurred and the populations increased when the strains Vibrio proteolyticus C279 and Aeromonas media C226 were tested. All isolates were successfully incorporated in the rotifers, since there was no significant difference between the numbers of bioencapsulated cells of different strains of isolates. The results show that it is possible to replace the microbial community in rotifer cultures, started from disinfected amictic eggs, with selected bacterial strains. This could be used as a tool for future studies to reveal the role of specific bacteria on first larval stages of marine fish species.     

Effect of prey type and size on the growth,survival and pigmentation of cod (Gadus morhua L.) larvae

The aim of this study was to investigate the effect of natural zooplankton versus rotifers and the effect of prey size on the growth and survival of cod larvae. At 20 days post hatch (DPH) myotome height, standard length and dry mass were significantly higher in larvae fed zooplankton compared to those fed rotifers. The dry mass at age 25 DPH was 135 μg (±45), 331 μg (±114), 391 μg (±121) for larvae fed rotifers, small size and large size plankton, respectively. At 25 days post hatch, the survival rates were 41.8% (±10.5), 90.7% (±2.3) and 91.4% (±1.7) for larvae reared on rotifers, small size and large size plankton, respectively. The limited growth and survival of cod larvae reared on rotifers were not mainly caused by the small size of rotifers. Large differences in skin coloration between larvae in the rotifer group and the two zooplankton groups were observed, probably caused by the large difference in astaxanthin levels in rotifers and natural zooplankton. We suggest that the nutritional composition of rotifers is a limiting factor for cod larvae growth and survival.     

Replacement of fresh algae with commercial formulas to enrich rotifers in larval rearing of yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

This study compared the efficacy of four products that are commonly used in hatchery for nutritional enhancement of rotifer Brachionus plicatilis as the starter food for yellowtail kingfish Seriola lalandi larvae. This experiment consisted of one fresh algae and three enrichment products: (1) Fresh algae were a mixture of Nannochloropsis and Isochrysis at 2:1 on a cell concentration basis; (2) S.presso, (Selco S.presso ^®, INVE Aquaculture); (3) Algamac 3050^® (Aquafauna, USA); (4) Nutrokol ^® (Nutra‐Kol, Australia). Survival rates of the fish fed rotifers enriched with fresh microalgae (40.69%) and S.presso (31.21%) were higher than those fed Algamac 3050 (10.31%). On 3 day post hatch (DPH), fish feeding incidence in the fresh algae treatment was significantly higher than that in other treatments. On 6 DPH, fish showed the lowest feeding incidence in the Algamac 3050 treatment. The methods of enrichment did not affect total lipid levels in either rotifer or fish larvae, but Algamac 3050 enrichment achieved the highest DHA/EPA ratio and lowest EPA/ARA ratio in both rotifers and fish larvae. This study indicates that fresh algae can be replaced by S.presso, but Algamac 3050 is not as good as other formula for rotifer enrichment in rearing yellowtail kingfish larvae in this system.     

Comparison of rotifer culture quality with yeast plus oil and algal-based cultivation diets

The culture quality of rotifers, Brachionus plicatilis, was compared for yeast and algal-based cultivation diets. The rotifer quality was evaluated based on factors which may affect survival and growth of marine fish larvae, including individual length and biomass, nutritional value, bacterial content, and rotifer viability. The diets used were monocultures of Tetraselmis sp., Isochrysis galbana, Pavlova lutheri, and baker's yeast plus capelin oil.Rotifers grown to early stationary phase with equal food rations exhibited equal length distribution, but the rotifer individual biomass was 10–25% higher for yeast-grown rotifers than for algal-grown rotifers.All diets gave equal protein content of individual rotifers. The lipid content was slightly higher and the ratio of protein to lipid was slightly lower with yeast plus capelin oil than with algae. The fatty acid composition of the rotifers was closely related to that of their dietary lipids and the 3 fatty acid content was not systematically different for the two types of diets.Use of yeast plus capelin oil resulted in considerably higher numbers of both suspended and rotifer-associated bacteria than with use of algal diets. No differences were found for the algal species involved. The viability of the rotifers in a temperature and salinity test was far better in groups fed algae than in groups fed yeast plus capelin oil.The results indicated an overall better quality of rotifers cultivated with algae than for rotifers cultivated with yeast and oil. Questions related to proteins and the microflora of rotifers should be further emphasized in future research.     

Feeding sequences (rotifer and dry diet), survival, growth and biochemical composition of African catfish, Clarias gariepinus Burchell (Pisces: Clariidae), larvae

The suitability of the freshwater rotifer Brachionus calyciflorus as starting food for the larviculture of African catfish, Clarias gariepinus Burchell, was investigated through studies of growth and fatty acid profiles in relation to different feeding sequences combining live food and dry diet in various proportions and during different mixed feeding periods. The best results for survival were observed when rotifers were supplied during the first week of feeding, i.e. sequences R₂ (exclusive supply of rotifers, then dry diet from day 8, onwards) and R₅ (50% rotifers+50% dry diet until day 7, then dry diet 100%), reaching 99.2% and 96.3%, respectively. The specific growth rate of larvae was largely dependent on the duration of preliminary feeding with the rotifers. A feeding with rotifers as a unique food source did not produce satisfactory growth during the first week of feeding. A precocious weaning showed that the highest growth rate and protein efficiency ratio (PER) can be obtained by feeding the larvae rotifers in association with a dry diet. The best PER and protein productive value (PPV) were recorded with feeding sequences R₂ and R₅. On the other hand, the series of polyunsaturated fatty acids was characterized by a relatively constant concentrations, and represented about 11.6% of the total fatty acids in sequence R₂ because of the presence of the acids of the linoleic series, which apparently originated from the food. The R₅ regime provided larvae with significant amounts of highly unsaturated fatty acids, such as linolenic acid C18:3n-3.