Phenotypic estimates and heritability values of Artemia franciscana

Artemia, in all stages of its life cycle, is suitable food for most diversified groups of aquatic animals. Although its size at different stages restricts its use as a food for some groups of fish, this problem can be overcome using selective breeding techniques. The formulation of any selective breeding programme calls for a proper understanding of the genetic architecture of the economically important traits of the population under study. Thus, heritability for certain important life history and reproductive traits was estimated in Artemia franciscana from the Great Salt Lake, Utah. In the present study, the sexwise heritability values for growth and reproduction traits were estimated using parent–offspring regression. The phenotypic parameters for the same traits are also recorded. The naupliar length was 487.0±2.0 and 490.6±1.8 μm for males and females, respectively, whereas the heritability values for naupliar length were 0.5851±0.2153 and 0.3766±0.1899 respectively. The length at 3 and 6 days of age were 1.87±0.03 and 4.10±0.08 mm, respectively, for males whereas 1.87±0.03 and 4.30±0.08 mm, respectively, for females. The heritability values for length at 3 and 6 days of age for males were 0.3272±0.3651 and 0.4965±0.2466, respectively, whereas the respective values for the females were 0.1167±0.3841 and 0.0222±0.2971. The estimates of length at first brood, pre‐reproductive period and number of offspring in first brood were 10.09±0.23 mm, 16.00±0.23 days and 53.57±1.37 days, respectively, whereas the heritability values for respective traits were 0.0403±0.1078, 0.3234±0.2874 and 0.3404±0.2202.     

4种单胞藻对卤虫生长和生殖影响的比较研究

以亚心形扁藻、小球藻、湛江等鞭金藻、绿色巴夫藻为饵料,卤虫为投喂对象,建立五个实验组分别进行研究,观察不同饵料对卤虫生长和生殖的影响,结果表明:投喂亚心形扁藻的卤虫生长最快,成活率高,生殖量也最多,其次为绿色巴夫藻组,湛江等鞭金藻的饵料效果最差.混合4种单胞藻投喂的效果也较好.     

A comparison of artificial and natural foods and their combinations in the rearing of goldfish, Carassius auratus (L.)

Intensive grow‐out of goldfish, Carassius auratus (L.), larvae and juveniles in closed systems requires the control of environmental conditions and feeding. This study investigates the use of different types of live food and combinations of live food and dry food in a series of four rearing experiments. Juvenile goldfish can be weaned from Artemia onto live food at about 24 days after the onset of feeding without causing a reduction in growth and survival. The replacement of Artemia by Daphnia at day 10 appears feasible, as growth and survival were not significantly affected. Fish fed decapsulated Artemia cysts grew better than fish fed live Artemia. Within the first 14 days, goldfish juveniles should be fed at least 155 cysts per fish per day to achieve fast growth and to minimize size variation.     

Replacement of live food with a microbound diet in feeding Litopenaeus setiferus (Burkenroad) larvae

Microbound feeds have been well accepted by shrimps and farmers in many penaeid shrimp hatcheries. The present study focused on an adequate level of replacement of Artemia nauplii and microalgae by a microbound diet for rearing Litopenaeus setiferus (Burkenroad) larvae. A microbound diet (MBD) consisting of fishmeal, squid meal, shrimp meal, yeast meal and soybean meal was used. The first experiment was designed to obtain the optimum level of MBD to complete the live feeding schedule, from Protozoea (PZ_III) to Mysis (M_III). The experimental levels of the microbound diet tested were 2, 4, 6 and 8 mg MBD L^?1 day^?1. The next step was to determine the Artemia nauplii replacement level from PZ_I to M_III by MBD. These experiments were carried out either in the presence (Experiment 2) or in the absence of algae (Experiment 3). Four replacement levels were tested: 0% (4 mg MBD L^?1 day^?1: 1 Artemia nauplii mL^?1), 40% (5.5 mg MBD L^?1 day^?1: 0.6 Artemia nauplii), 60% (6.5 mg MBD L^?1 day^?1: 0.4 Artemia nauplii) and 100% (8 mg MBD L^?1 day^?1: 0 Artemia nauplii). In all experiments growth, survival, development, quality index (QI) and performance index (PI), were used to determine the optimum concentration of microbound diet. Results showed that 6 mg MBD L^?1 day^?1 can be recommended as a complement to live food for L. setiferus larvae from PZ_III to M_III. In the presence of algae, maximum growth and survival may be obtained in 40–60% (5.5–6.5 mg MBD L^?1 day^?1) of Artemia nauplii replacement levels. In the absence of algae, the Artemia nauplii replacement resulted in slower development, less salinity resistance, lower growth and lower survival than was obtained in larvae fed with algae.     

Infection and mortality by the yeast Metschnikowia bicuspidata var. bicuspidata in chinook salmon fed live adult brine shrimp (Artemia franciscana)

First-feeding chinook salmon were fed either live adult Artemia franciscana or commercial feed over a 15-week period. Unexplained mortality began occurring in the Artemia-fed fish after 35 days on the diets, with cumulative mortality reaching 34.5% in the Artemia-fed fish compared with 4.3% in feed-fed fish. Necropsy examinations revealed systemic fungal yeast infections and the causative agent was cultured from kidneys. Fungal cells were observed in the transport water of Artemia shipments and within the Artemia. The Artemia were purchased from a retail supplier, and originated from salt ponds in San Francisco Bay (SFB), California. Artemia infection rates ranged from 0.5% to 37.5% (mean 16.5±3.59%) in shipments received over a 5-week period. The fungus was characterized by morphological and physiological properties and was identified as Metschnikowia sp., a pathogenic yeast of aquatic invertebrates. The yeast grew at 9–27 °C, and 0–180 ppt NaCl, and could tolerate salinity of at least 270 ppt. Sequence analysis of the divergent D1/D2 domain of ascomycetous yeast 26S ribosomal DNA identified the organism as Metschnikowia bicuspidata var. bicuspidata. The organism was found in water from the salt ponds and probably entered from the bay. Mortality due to the fungal infection stopped after changes were made in the handling of incoming Artemia shipments.     

Growth and lipid composition of phyllosomata of the southern rock lobster, Jasus edwardsii, fed enriched Artemia

Newly hatched phyllosoma larvae of Jasus edwardsii were on‐grown to stage V. Using triacylglycerol‐rich marine oil nutrient sources and microalgae, Artemia were enriched with the major polyunsaturated fatty acids (PUFA) to ratios similar to that of wild‐caught phyllosomata. Artemia enriched by different methods were fed to cultured phyllosomata. At each stage animals were counted, measured and sampled for lipid analyses. Survival was highest from stages II to III (62–86%), with mean total survival at 3–12%. From stages I to V larvae increased in mass (0.2–2.2 mg) and total length (2.1–5.8 mm), and decreased in total lipid. The major lipid class in all phyllosomata was polar lipid, followed by sterol, with no triacylglycerol detected. The main fatty acids were 18:1(n‐9)c, 18:2(n‐6), 16:0, 18:0, eicosapentaenoic acid [EPA; 20:5(n‐3)], 18:1(n‐7)c, arachidonic acid [AA; 20:4(n‐6)] and docosahexaenoic acid [DHA; 22:6(n‐3)]. On‐grown phyllosomata had levels of AA and EPA similar to that of wild phyllosomata, but contained markedly lower levels of DHA. Strategies for enhancement of DHA levels will be needed for culture of rock lobster phyllosomata.     

Use of Cyclop-eeze as a substitute for Artemia nauplii in larval rearing of giant freshwater prawn Macrobrachium rosenbergii (De Man 1879)

Four feeding experiments, replacing 25% (T₁), 50% (T₂), 75% (T₃) and 100% (T₄), by dry weight, of the live feed Artemia nauplii for Cyclop‐eeze, a new larval feed that was claimed to contain the highest known levels of astaxanthin and omega‐3 polyunsaturated fatty acids, were compared against a control that was fed with Artemia and egg custard alone, to the larvae of giant freshwater prawn Macrobrachium rosenbergii (De Man 1879). Analysis of different production characteristics of the larvae revealed that the highest survival up to postlarvae (PL) stage was obtained for T₂ in which 50% of the Artemia nauplii were replaced by Cyclop‐eeze [freeze‐dried (FD) deep frozen (DF)], and the highest astaxanthin content of the larval tissue obtained in T₄ in which the larvae were fed 100% Cyclop‐eeze, although the survival rate was the lowest in this treatment. The costs of different treatments were also compared. The Artemia consumption million⁻¹ larvae was the highest in control (11490 g), followed by T₁ (8240 g), T₂ (4990 g), T₃ (3730 g) and T₄, which completely replaced Artemia from stage 5 onwards (1830 g). The highest consumption of Cyclop‐eeze million⁻¹ larvae was in T₄ (1670 and 10 880 g), followed by T₃ (850 and 5560 g), T₂ (410 and 2690 g) and T₁ (230 and 1490 g) of FD and DF, respectively. The astaxanthin contents of the late‐stage larvae fed under the four treatments were 24.90, 27.40, 28.60 and 35.60 μg g⁻¹ tissue for T₁, T₂, T₃ and T₄, respectively, while that of the control was 23.70 μg g⁻¹. The lowest cost of live feeds million⁻¹ PL was obtained for T₂ (US$ 428.60), followed by T₁ (US$ 490.46), control (US$ 529.07) and T₃ (US$ 583.26), while it was the highest for T₄ (US$ 890.93). The results indicated that Cyclop‐eeze could economically replace Artemia nauplii at 50% level that could significantly improve the survival and carotenoid composition of the larvae of M. rosenbergii.     

Assessment of marine thraustochytrid <Emphasis Type="Italic">Schizochytrium limacinum</Emphasis> OUC88 for mariculture by enriched feeds

ABSTRACT:   In the present study, Schizochytrium limacinum OUC88, a thraustochytrid with high content of docosahexaenoic acid (DHA, 22:6 n −3), was used as feed for rotifer Brachionus plicatilis and Artemia franciscana . The rotifer and Artemia were harvested at 3, 6, 9, 12, 18, and 24-h intervals, analyzed for fatty acid composition, and compared with the control which fed on yeast only. The highest DHA content resulted from an enrichment period of 12 h for both fed organisms, reached 13.4 and 10.9% of the total fatty acids (TFAs) in rotifers and Artemia nauplii, respectively, and the DHA level reduced sharply if enrichment time was longer than 12 h. The pseudoalbinism rate of turbot Scophthalmus maximus juveniles fed enriched rotifers and Artemia nauplii reduced greatly (40% lower than in control group). Thus, enrichment of rotifers and Artemia nauplii by DHA-rich Schizochytrium limacinum OUC88 may provide a practical strategy for feeding fish juveniles in aquaculture.