Marine gammarids (Crustacea: Amphipoda): a new live prey to culture Octopus maya hatchlings

The effects of feeding two alternative live prey Hyalella azteca (freshwater gammarids) and Hyale media (marine gammarids) to Octopus maya hatchlings were compared with feeding adult Artemia sp., traditionally used during the first weeks of the life cycle. Hatchlings were fed ad libitum these three live preys during the first 15 days, and a paste elaborated with fresh squid and shrimp during the next 15 days when hatchling can be fed prepared diets. Weight (g) and specific growth rates (% day^?1) were determined every 15 days. Octopus maya hatchlings fed with marine gammarids grew larger (6.9 ± 0.2% day^?1) compared with hatchlings fed Artemia sp. or freshwater gammarids (4.8 ± 0.2% and 5.0 ± 0.3% day^?1 respectively). Survival was also higher (92.2 ± 6.8%) for hatchlings fed marine gammarids, than for those fed Artemia sp. (74.5 ± 23.8%) or freshwater gammarids (41.2 ± 21.2%). The content of acylglycerides, cholesterol and proteins in O. maya fed marine gammarids suggested a better nutrient assimilation by the hatchlings. Also, polyunsaturated fatty acids levels (EPA and DHA) were more abundant in marine gammarids, possibly contributing to the higher growth rates observed. This is the first study revealing a successful use of marine gammarids as alternative prey for octopus hatchlings culture.     

Effects of feeding live or frozen prey on growth, survival and the life cycle of the cuttlefish, Sepia officinalis (Linnaeus, 1758)

The effects of feeding live or frozen grass shrimp (Palaemonetes varians) to the cuttlefish, Sepia officinalis, were determined in two experiments. During Experiment I, two populations of 30 cuttlefish (aged 90 days old) were fed either live or frozen grass shrimp. Cuttlefish fed live shrimp grew larger, matured earlier, had a shorter life cycle (255 days) than the ones fed frozen shrimp (282 days), and had lower mortality. Females from the group fed frozen shrimp matured a month later but were significantly larger, 130.9 ± 38.5 g, compared to 74.2 ± 16.0 g, laid larger eggs, 0.47 ± 0.11 g, compared to 0.28 ± 0.10 g, and had higher individual fecundity (411 eggs female⁻¹, compared to 150 eggs female⁻¹). Newly born hatchlings from both groups had similar weights. During Experiment II, six replicates of 15 cuttlefish (50 days old) were used, three for each of the two diets tested. The exact same amount of live or frozen shrimp was provided to both populations twice a day. No differences in growth and feeding rates or food conversions were found at the end of the experiment. During the first week, cuttlefish fed frozen shrimp grew larger, and had higher conversion rates, compared to the ones fed live shrimp. Mortality was higher for the group fed live shrimp (36.6%) in Experiment II, mainly occurring during the last week. Mortality for cuttlefish fed frozen shrimp in Experiment II was 2.2%. Results obtained here indicate that freezing the grass shrimp only had a negative effect on the survival of S. officinalis in Experiment I. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of enriched Artemia nauplii on production, survival and growth of the mysid shrimp Mysidopsis almyra Bowman 1964 (Crustacea: Mysidacea)

The effects of enriched Artemia nauplii on larvae production and survival and growth of the mysid Mysidopsis almyra Bowman 1964 are compared. There were no significant differences (P > 0.05) in production between mysids fed the Artemia nauplii (133 ± 69 mysids day⁻¹) and mysids fed the enriched nauplii (139 ± 82 mysids day⁻¹). No differences in size of newly hatched mysids or mysid growth to 15 days (P > 0.05) were found between the two diets. Survival was significantly higher (P < 0.05) for mysids fed the enriched nauplii (59.1%) compared with mysids fed Artemia nauplii (41.4%).     

The effect of unilateral eyestalk ablation and diet on the reproductive performance of wild-caught Farfantepenaeus aztecus (Ives, 1891) using a closed recirculating maturation system

Two studies were conducted to evaluate the effects of unilateral eyestalk ablation and diet on the reproductive performance of wild populations of Farfantepenaeus aztecus. In both studies, females in two treatments were unilaterally ablated while those in the control treatment were not. Shrimp in the non‐ablated treatment and one of the unilaterally ablated treatments received frozen bloodworms (8% BW day⁻¹) and frozen squid (12% BW day⁻¹). The bloodworm component of the diet of the third unilateral ablation treatment was replaced with frozen adult enriched Artemia sp. Ablated female population spawning per night, in both studies, was higher than non‐ablated spawning (8.5 and 8.9 vs. 2.6%; 7.4 and 7.5 vs. 2.7% respectively; P<0.05). Replacement of bloodworms with adult enriched Artemia sp. had no negative effect on the number of eggs spawned per ablated female (124 000 vs. 115 000 eggs spawn⁻¹; 144 000 vs. 151 000 eggs spawn⁻¹ respectively; P>0.05). The life span of ablated females fed adult enriched Artemia sp. was 8 and 40 days longer than ablated females fed bloodworms for the first and second studies respectively. Replacement of bloodworms with adult enriched Artemia sp. resulted in higher hatch and larval survival rates (Nauplius 1 to Zoea 1) (55.0% vs. 46.9% and 44.8% vs. 37.2%), respectively, P<0.05.     

Effects of culture density and live prey on growth and survival of juvenile cuttlefish, Sepia officinalis

The effects of culture density on growth and survival of juvenile cuttlefish were tested. Groups of 1, 3 and 5 hatchlings were placed in small containers with bottom surface of 80 cm², obtaining individual densities of 125, 375 and 625 cuttlefish m^–2, respectively. Additionally, groups of 5 hatchlings were placed in containers with 2 different bottom areas (80 and 240 cm²), providing culture densities of 625 and 42 cuttlefish m^–2, respectively. A total of 120 hatchlings were used and experiments lasted for 40 days. No differences were found in growth between any of the densities tested throughout the experiment until 35 days old. After this, cuttlefish placed in isolation grew significantly larger. A second experiment was conducted in a flow through system, using two rectangular tanks with bottom surface of 0.5 m². Two groups of 25 cuttlefish hatchlings were used in this experiment, which lasted for 40 days. Both groups were fed live juvenile shrimp (Crangon crangon) during the first 5 days. Afterwards, one group was fed live fish fry of different species, while the other continued to be fed shrimp. After day 10 and until the end of the experiment, hatchlings fed shrimp grew significantly larger than those fed fish fry. Survival of hatchlings fed shrimp or fish fry after 40 days was of 100% and 68%, respectively. Total protein content of both prey types was similar. Therefore, the higher polar lipid content, especially due to the higher phosphatidylcholine and phosphatidylethanolamine levels observed in the shrimp, compared to fish fry could possibly be one of the major factor to explain the significantly higher growth rates for S. officinalis juveniles fed shrimp. Also, the percentage of polar lipids in the shrimp (47.4%) was closer to the one of juvenile cuttlefish (38.1%) than the composition of polar lipids in fish fry (10.4%). This could also be an important factor to explain the poor growth and survival obtained when feeding fish fry to the cuttlefish.     

Delivery of HUFA, probionts and biomedicine through bioencapsulated Artemia as a means to enhance the growth and survival and reduce the pathogenesity in shrimp Penaeus monodon postlarvae

One of the major problems in the shrimp culture industry is the difficulty in producing high-quality shrimp larvae. In larviculture, quality feeds containing a high content of highly unsaturated fatty acids (HUFA) and ingredients that stimulate stress and disease resistance are essential to produce healthy shrimp larvae. In the present study, Penaeus monodon postlarvae (PL15) were fed for 25 days on an unenriched Artemia diet (control; A) or on a diet of Artemia enriched with either HUFA-rich liver oil of the trash fish Odonus niger (B), probionts [Lactobacillus acidophilus (C1) or yeast-Saccharomyces cerevisiae (C2)] or biomedicinal herbal products (D) that have anti-stress, growth-promoting and anti-microbial characteristics. P. monodon postlarvae fed unenriched Artemia exhibited the lowest weight gain (227.9 ± 8.30 mg) and specific growth rate (9.95 ± 0.05%), while those fed the HUFA-enriched Artemia (B) exhibited the highest weight gain and specific growth rate (362.34 ± 12.56 mg and 11.77 ± 0.08%, respectively). At the end of the 25-day rearing experiment, the shrimp postlarvae (PL40) were subjected to a salinity stress study. At both low and high (0 and 50‰) salinities, the group fed the control diet (A) experienced the highest cumulative mortality indices (CMI) 935.7 ± 2.1 and 1270.7 ± 3.1, respectively. Those fed diet D showed the lowest stress-induced mortality, and CMI were reduced by 31.1 and 32.3% under conditions of low and high salinity stress, respectively. A 10-day disease challenge test was conducted with the P. monodon postlarvae (PL40–PL50) by inoculating the shrimp with the pathogen Vibrio harveyi at the rate of 10⁵–10⁷ CFU/ml in all rearing tanks. P. monodon postlarvae fed probiont-encapsulated Artemia diets (C1 and C2) exhibited the highest survival (94.3 and 82.3%, respectively) and lowest pathogen load (V. harveyi) in hepatopancreas (5.2 × 10² ± 9.0 × 10 and 4.6 × 10² ± 9.0 × 10 CFU g⁻¹, respectively) and muscle (2.0 × 10² ± 6 × 10 and 1.7 × 10² ± 8.6 × 10 CFU g⁻¹, respectively) tissues. The shrimp that were fed the unenriched Artemia (Control; A) showed the lowest survival (26.33%) and highest bacterial load in the hepatopancreas (1.0 × 10⁵ ± 5 × 10³ CFU g⁻¹) and muscle (3.6 × 10⁴ ± 6 × 10² CFU g⁻¹). The shrimp fed the herbal product (D)-enriched Artemia also exhibited enhanced survival and reduced V. harveyi load in the tissues tested compared to the control diet (A) group. The results are discussed in terms of developing a quality larval feed to produce healthy shrimp larvae.     

Culture of the mysid, Mysidopsis almyra (Bowman), (Crustacea: Mysidacea) in a static water system: effects of density and temperature on production, survival and growth

The effects of animal density and water temperature on the culture of the mysid, Mysidopsis almyra (Bowman), in a static water system were evaluated. An initial set of experiments tested the effects of mysid density on production. Densities of 25, 37.5, 50, 100 and 200 mysids L^–1 were placed in trays with 20 L of sea water. Temperatures were maintained at 26 ± 2 °C. A second set of experiments was conducted in the same system at three different temperatures (18 ± 1, 22 ± 1 and 26 ± 2 °C) using a mysid density of 50 mysids L^–1 (1000 mysids tray^–1). All experiments had a duration of 30 days. The mysids in all trials were cultured at 20 ± 2‰ salinity and fed Artemia nauplii enriched with marine fatty acids. There was a positive correlation between production and mysid densities up to populations of 100 mysids L^–1; maximum production was 273 ± 99 hatchlings day^–1. At a population density of 200 mysids L^–1, high mortality and low production were recorded 4 days after the start of the experiment. The experiments testing different temperatures showed that mysid production was higher at 22 ± 1 °C, although this result was not significant (P > 0.05). Growth rates and hatchling survival after 7 days were significantly higher (P < 0.05) at 26 ± 2 °C compared to survival and growth at 18 or 22 °C.     

Effects of live prey availability on growth and survival in the early stages of cuttlefish Sepia officinalis (Linnaeus, 1758) life cycle

This investigation examined the effects of live prey availability on growth and survival of Sepia officinalis. Two independent experiments, comprising two feed rations each, were performed, using adequate prey size. In the first experiment, cuttlefish hatchlings were fed live mysids, Paramysis nouvelli [(feed ratio I (fr I)], at 15% body weight per day (bw day^?1) (fr I₁₅) and 30% bw day^?1 (fr I₃₀). In the second experiment, juvenile cuttlefish were fed live Atlantic ditch shrimp, Paleomonetes varians (fr II), under the same experimental design. In both experiments, the final mean weight, feeding rate and instantaneous growth rate were higher when animals were fed feed ratio fr II₁₅ and fr II₃₀ (30% bw day^?1). The results indicate that prey availability influenced weight gain, irrespective of the prey used, during the first 2 months of cuttlefish life cycle. This effect seems to be more noticeable when a certain limit of prey is achieved. For cuttlefish fed fr II, the optimal prey density is thought to be under 2.5 g prey L^?1 (i.e. 14 shrimp L^?1). Results indicate that cuttlefish can withstand prey densities up to 120 mysids L^?1 for cuttlefish up to 3 weeks old and 19 shrimps L^?1 for cuttlefish up to 6 weeks old.     

Effect of hot water extracts of brown seaweeds Sargassum spp. on growth and resistance to white spot syndrome virus in shrimp Penaeus monodon postlarvae

An experiment was conducted to evaluate the effect of a hot water extract of brown seaweeds Sargassum duplicatum and Sargassum wightii on the growth and white spot syndrome virus (WSSV) resistance in shrimp Penaeus monodon postlarvae (PL). Artemia nauplii (instar II) were enriched with both seaweed extracts at various concentrations (250, 500 and 750 mg L^?1) and fed to the respective P. monodon (PL15–35) group for 20 days. A control group was also maintained without seaweed extract supplementation. The weight gain of the experimental groups was significantly higher (0.274–0.323 g) than the control group (0.261 g). Similarly, the specific growth rate was also significantly higher (16.27–17.06%) in the experimental groups than in the control group (16.03%). After 20 days of the feeding experiment, the shrimp PL were challenged with WSSV for 21 days. During the challenge test, the control shrimp displayed 100% mortality within 8 days. In contrast, the mortality percentage of the highest concentration (750 mg L^?1) of seaweed extract enriched Artemia nauplii fed shrimp was 54–79%. Comparatively, low mortality was observed in S. wightii extract‐enriched Artemia nauplii fed shrimp. The polymerase chain reaction analysis indicated the concentration‐dependent infection of WSSV in P. monodon PL.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

Frozen mysids as an alternative to live Artemia in culturing seahorses Hippocampus abdominalis

This investigation examined the effects on growth and survival of seahorses Hippocampus abdominalis Leeson 1827 fed a 25% body weight (wet weight) daily ration of live Artemia sp. enriched with Algamac‐3050, frozen mysids Amblyops kempi or a combination of live enriched Artemia and frozen mysids. After 3 months there was no difference in seahorse length, wet weight, condition factor (CF), or food conversion ratios (FCR) between the treatments. Mean daily specific growth rate (SGR) was higher for the Artemia‐only treatment than for the mysid‐only treatment (P<0.05). FCRs ranged from 6.14 g to 8.72 g dry weight of food required to give a 1‐g dry weight increase in seahorses. There was no difference in survival between treatments. Fatty acid analysis revealed that mysids had a higher percentage composition of EPA, 20 : 5n‐3, and DHA, 22 : 6n‐3, but a lower composition of AA, 20 : 4n‐6, than enriched Artemia. Percentage n‐3 highly unsaturated fatty acids (HUFAs) in mysid levels were approximately twice that of Artemia. Proximate analysis revealed mysids to be higher than the enriched Artemia in protein and fats, and lower in water content. This experiment demonstrates that, although no growth advantage was derived from the use of frozen mysids, they can be used successfully as an alternative food to live enriched Artemia for H. abdominalis. The use of frozen mysids is highly recommended in commercial seahorse culture if the seahorses are to be sold into the live aquarium trade, as this may increase their chances of survival after sale.     

Comparison of growth and survival of white shrimp postlarvae (Litopenaeus vannamei) fed dried Artemia biomass versus four commercial feeds and three crustacean meals

The use of dried Artemia biomass meal as an exclusive feed for postlarval white shrimp (Litopenaeus vannamei) was compared with four commercial feeds and three crustacean meals in a series of trials. Postlarvae (PL1–PL6) were stocked at a density of 1.5–2.5/litres in 16 tanks (100 litres volume) and fed, ad libidum, five times a day, over 23–29 days. Feeding postlarval shrimp with dried Artemia biomass resulted in a significantly larger size than feeding with three of the commercial feeds, and the crustacean meals. There was no significant size difference observed in animals fed with Artemia biomass and the commercial 'Golden Pearls' feed for postlarvae, however the coefficient of variation among the size of the 'Golden Pearls' fed animals was significantly higher. The weight increase of animals fed with Artemia biomass was higher than in animals fed with all the tested feeds. The survival rate was not significantly different in animals fed with Artemia flakes from 'Salt Creek', 'Bio-Marine', 'Golden Pearls' and Artemia biomass, however the survival rate was significantly larger in animals fed with Artemia biomass than in animals fed with the crustacean meals and 'Artemac.' Results suggest that dried Artemia biomass is a well-suited feed for postlarval L. vannamei.     

Nutrient composition of fairy shrimp Streptocephalus sirindhornae nauplii as live food and growth performance of giant freshwater prawn postlarvae

Nutritional efficacy of fairy shrimp (Streptocephalus sirindhornae) nauplii, as a live food, was studied for growth performance and survival rate of giant freshwater prawn (Macrobrachium rosenbergii) postlarvae. A feeding experiment was designed with four different feeds: dry commercial feed, fairy shrimp nauplii, Artemia sp. nauplii and adult Moina macrocopa. Results from the nutritional composition revealed that fairy shrimp nauplii had protein and lipid contents of 54.58 ± 2.8 g kg^?1 and 255 ± 2.8 g kg^?1, respectively. The highest value for an individual amino acid in fairy shrimp was lysine (140.7 ± 1.6 g kg^?1). The essential amino acids content in the whole body of the larval prawns was in the range of 66.7–67.5 g kg^?1. Fairy shrimp nauplii had the highest essential amino acid ratio (A/E) of lysine, similarly, in musculature of prawn larvae. Weight gain and specific growth rate of the postlarvae fed with fairy shrimp nauplii were significantly higher than those fed with Artemia nauplii, adult Moina and dry commercial feed. The presented results suggest that S. sirindhornae nauplii can be used as a nutritionally adequate food for freshwater prawn M. rosenbergii postlarvae.     

A diet of fructose‐enriched Artemia improves the response of juvenile Litopenaeus vannamei shrimp to acute low‐salinity challenge

The Pacific white shrimp (Litopenaeus vannamei), as an economically important species, has been reared in low‐salinity water during the last decade. To investigate how juvenile L. vannamei shrimp fed with fructose‐enriched Artemia respond to acute low‐salinity stress, the shrimp were randomly divided into four treatment groups, three groups were fed with Artemia enriched with either 100, 200 and 300 mg L^?1 of fructose and a control group fed with Artemia with no enrichment for 10 days. The results showed that the 300 mg L^?1 fructose group demonstrated the maximum survival rate and glycogen content. Additionally, the 300 mg L^?1 fructose group showed significantly higher Na⁺/K⁺‐ATPase activity, total antioxidant capacity, and expression levels of Na⁺/K⁺‐ATPase α‐subunit, V‐H ATPase α‐subunit, hexokinase, phosphofructokinase, antioxidants (SOD, CAT, GPX) and Hsp70 mRNA when compared with the control group. Furthermore, after exposure to low salinity, the mRNA levels of phosphofructokinase, V‐H ATPase α‐subunit, GPX, p38, JNK and Rac1 stayed constant in shrimp fed with fructose‐enriched Artemia but changed significantly in the control group. Thus, a diet of fructose‐enriched Artemia can improve the osmoregulation and survival of juvenile L. vannamei shrimp exposed to low salinities.     

Successful rearing of whiteleg shrimp Litopenaeus vannamei larvae fed a desiccation‐tolerant nematode to replace Artemia

The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non‐enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso^®, until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA‐enriched or PUFAs‐enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA‐enriched nematodes (5.1 ± 0.5 mm; 33.1%–44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6.     

Maximizing lobster, Homarus gammarus (L.), egg and larval viability

The viability of batches of larvae reared to produce lobsters, Homarus gammarus (L.), for stock-supplementation experiments varied widely and rendered the timing and numbers of juveniles available for release unpredictable. Egg lipid reserves, time of hatching, exposure to low salinity during incubation and the influence of feeding regimes on water quality during larval culture were among the factors judged most likely to have affected viability. There was considerable variation in the lipid content of eggs from different females captured in 1989 and 1990. The proportion of lipid in eggs from females caught in 1990 was higher (10-20%) than that in eggs from females caught in 1989 (6-11%). The fatty acid content of eggs declined 72-80% during development although the overall proportions of fatty acids remained similar. Analysis of eggs and larvae from a single brood showed that rapidly developing eggs and the larvae that hatched from them contained greater triacylglyceride lipid reserves (by 49% and 15% respectively) than those which developed more slowly and hatched later. Exposure to reduced salinity (below 29 psu) prolonged development (by 30%), increased losses (to > 50%) and reduced the ratio of n-3:n-6 fatty acids (from 35-48 to 18-29) of eggs being incubated by captive, wild-caught, female lobsters. Larvae hatching from eggs held in reduced salinity (23 psu) survived less well (3% compared with 15%) than those incubated in sea water of 29 psu. The rate and degree to which fouling organisms became attached to larvae was related to feeding regime but not to development rate. A diet of mysids supplemented with mussel produced most fouling, generally poorer growth and a higher incidence of moulting abnormalities than a diet of mysids supplemented with Artemia nauplii. Among larvae fed Artemia, those developing early were significantly larger at instar 4 than late developers (56.4 mg cf. 49.8 mg, P < 0.05), but such differences in weight were not maintained by juveniles during the following 31 days of culture. The ecological and aquacultural implications of the results are discussed.     

不同卤虫混养比例对生物絮凝系统凡纳滨对虾标粗效果的影响

在生物絮凝凡纳滨对虾养殖系统中,分别以100%、50%、0%的比例投喂活的卤虫幼体(Artemia spp)和饲料(分别记为A组,AF组和F组),研究其对养殖过程中氮素转化途径及转化效率的影响。卤虫以湿质量计算,饲料以干质量计算。试验结果显示,A组亚硝酸盐浓度显著低于另外2组(P<0.05);各组氨氮浓度在养殖第7天时达到峰值,此后迅速降低并维持在1 mg/L以下,3组之间差异不显著(P>0.05);3组硝酸盐浓度均无积累,且略有下降;养殖30 d后,A组对虾存活率(35.67%)显著高于其余两组(均低于30%)(P<0.05);A组对虾终末平均体质量为(1.92±0.96)g,显著低于AF组的(2.99±1.85)g和F组的(3.25±1.23)g(P<0.05),原因可能是卤虫的营养成分相比配合饲料较为单一。     

Rearing techniques and nutritional quality of two mysids from Gran Canaria (Spain)

This paper presents the preliminary results of different trials carried out with two species of mysids from Gran Canaria: Leptomysis lingvura (G.O. Sars, 1866) and Paramysis nouvel. Experiments lasting 21 days showed significantly higher fecundity and survival in L. lingvura than in P. nouveli (P<0.05). We also report the biochemical profile of both species fed 48‐h‐Artemia nauplii enriched with Easy‐DHA‐Selco^® for 7 days. A comparison of our results with those of for Artemia and rotifers, organisms frequently used as live food in aquaculture, showed that mysids have a high percentage of protein per dry mass (73.38% in P. nouveli, and 74.19% in L. lingvura). Furthermore, the percentage of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (AA) in total fatty acids was higher in both species than that reported by Roo and colleagues for rotifers and Artemia. In addition to the content of these fatty acids, their ratios between them are also important for normal growth and larval development. We found that the ratio, DHA:EPA, was 0.85 0.02 and 0.89 0.01; the ratio, DHA: AA, 6.25 0.26 and 4.74 0.14; and the ratio, EPA:AA, 7.32 0.26 and 5.32 0.2, respectively, for P. nouveli and L. lingvura in cultures and these ratios do not significantly differ (P>0.05) from organisms in the wild. Here, we argue that as mysids are prey for many commercially important fish, cephalopods and rays, it is likely that the biochemical composition of mysids in their natural environment is “optimal” for these predators. Therefore, we studied the lipid profile of both species as they naturally occur in their environment. The results indicate that these mysids could be used to develop high quality live fish food.     

Effect of different forms of Artemia biomass as a food source on survival,molting and growth rate of mud crab (Scylla paramamosain)

An experiment was conducted to evaluate the effect of different forms of Artemia biomass as a food source on survival, molting and growth rate of mud crab Scylla paramamosain. Instar 1 crablets with a mean weight of 0.0082 ± 0.0007 g were reared both individually and communally and fed with different diets consisting of fresh shrimp meat (control feed), live Artemia biomass, frozen Artemia biomass and a dried Artemia‐based formulated feed for 40 days. The highest survival was obtained for crablets receiving live Artemia (92.5% and 75.8%) followed by the groups fed with frozen biomass (90.0% and 47.5%), the control feed (72.5% and 24.2%) and the dried Artemia‐based diet (60.0% and 21.7%) for individual and communal cultures, respectively. The intermolt period, the total number of moltings and the growth rate, which were determined on individually reared crabs, showed the same pattern as for survival. The results suggest that crab performance decreased in the following order: live Artemia>frozen Artemia > fresh shrimp meat > dried Artemia‐based formulated feed. Live Artemia biomass proved an ideal feed for nursery of Scylla paramamosain crabs. Frozen Artemia biomass may be an alternative in times of shortage. Our findings illustrate the high potential for local utilization of Artemia biomass in Vietnam for reliable production of mud crab juveniles.     

Nutritional evaluation of decapsulated cysts of fairy shrimp (Streptocephalus dichotomus) for ornamental fish larval rearing

The suitability of decapsulated cysts of the fairy shrimp, Streptocephalus dichotomus as a sole diet was evaluated for the ornamental angelfish Pterophylum scalare larvae. Brine shrimp, Artemia sp., and microworms, Panagrellus redivivus, were used as comparison foods. The results indicate an appreciable weight gain of 15.22±1.69 mg and a growth (length) of 0.876±0.03 cm in experimental fish fed decapsulated fairy shrimp cysts compared with the growth and weight of fish fed other foods. The influence of the experimental diets was further reflected in the composition of fatty acid and amino‐acid profiles of the experimental fish. Angelfish larvae readily consumed the decapsulated cysts and utilized them efficiently during the early days of exogenous feeding.