New approaches for Artemia pond culture.

A project for intensive culture of Artemia in Vinhchau solar saltwork was funded by Soctrang Authority. The aim of this project is to increase the average cyst yield of 50kg.ha-1.crop, and to build up a stable culture technique with a better yield for local farmers. Multiple laboratory experiments were set up with inert food including fermented rice bran, tiger shrimp feed (PL15), as well as their combination with live algae (Chaetoceros). Results showed that, under laboratory conditions, fermented rice bran and tiger shrimp feed can be used as supplemental food sources. The shrimp feed alone or in combination with algae always gave better cyst production compared to the others, but should not account for more than 50% of the diet. In the field trials, aeration of Artemia ponds also increased cyst yields (from 195.8+/-44.2 to 207+/-46.1kg.ha-1.crop with 6 and 12 aeration a day, respectively) compared to ponds with no aeration (88.2+/-27.5kg.ha-1.crop), however the returns on investment (ROI=2.73-2.71 with aera tion vs. 2.24 without) are not significantly different. Utilization of fermented rice bran (20kg.ha-1.day) and shrimp feed (6kg.ha-1.day) as a supplementary feed during pond production in combination with greenwater supplies (10% of pond volume daily) resulted in higher yields (96.0+/-15.9 and 157.2+/-15.0kg.ha-1.crop, respectively) than traditional culture; Shrimp feed as a supplemental feed supported the cyst yield but their negative effect was at a high cost vs. traditional culture and use of fermented rice bran. Based on the cyst yield and ROI, fermented rice bran should be a promising item for poor farmers.

SNP detection in Na/K ATP-ase gene α1 subunit of bisexual and parthenogenetic Artemia strains by RFLP screening.

In order to find a marker for differentiating between a bisexual and a parthenogenetic Artemia strain, Exon-7 of the Na/K ATPase α(1) subunit gene was screened by RFLP technique. The results revealed a constant synonymous SNP (single nucleotide polymorphism) in digestion by the Tru1I enzyme that was consistent with these two types of Artemia. This SNP was identified as an accurate molecular marker for discrimination between bisexual and parthenogenetic Artemia. According to the Nei's genetic distance (1973), the lowest genetic distance was found between individuals from Artemia urmiana Günther 1890 and parthenogenetic populations, making the described marker the first marker to easily distinguish between these two cooccurring species.

Life cycle characteristics of six Artemia populations from Iran.

The present study was conducted to achieve the life cycle characteristics of six Artemia populations (one bisexual and five parthenogenetic) from Iran. The cysts of parthenogenetic strains were collected from Maharlu, Incheh, Varmal and Qom salt lakes and Lagoons at the periphery of Lake Urmia. Cysts of the bisexual Artemia urmiana were collected from the Lake Urmia. All cysts strains were hatched using the standard procedures and the nauplii from all populations were reared at 80 g L(-1) at laboratory conditions. Survival and total length of the Artemia were measured on days 8, 11, 14, 17, 20 and 23 of culture. Randomly selected adult animals were studied for eight reproductive and four life span characteristics. The findings showed that parthenogenetic Artemia from Maharlu, Incheh lakes and from Lagoons at the vicinity of the Lake Urmia had significantly highest (p < 0.05) values of survival rate (73 and 62.8%, respectively) compared to bisexual A. urmiana and parthenogenetic strains from Qom and Varmal lakes (49.6, 29.2 and 23.2%). No significant differences were observed in all growth strain populations when cultured under similar laboratory conditions. Artemia populations from Maharlu, Qom lakes and from Lagoons in many occasions had significantly highest (p < 0.05) reproductive values compared to other three populations including the bisexual A. urmiana. The results showed the highest heterogeneity and intrapopulation variations among parthenogenetic population strains.

Effects of salinity on survival, growth, reproductive and life span characteristics of Artemia populations from Urmia Lake and neighboring lagoons.

This study deals with effects of different salinities on the survival, growth, reproductive and lifespan characteristics of three Artemia populations from Urmia Lake and small lagoons at the vicinity of the lake under laboratory conditions. Experimental salinities ranged from 75 to 175 g L(-1). Salinity was proved to have significant impact on the majority of the characters studied in this survey. Growth and survival in bisexual A. urmiana and parthenogenetic Artemia from Lake Urmia were significantly higher with respect to the parthenogenetic Artemia from lagoons at most of the salinities tested. Reproductive characteristics such as total number of broods, total offspring number of offspring in each brood and number of offspring at each day of reproductive period reduced with increasing salinity. Moreover higher salinity prolonged the prereproductive period but shortened the total reproductive period. Higher salinities also affected the percentage of encystment and post-reproductive period, showing significantly higher values in parthenogenetic populations in comparison to bisexual A. urmiana.

A standard experimental diet for the study of fatty acid requirements of weaning and first ongrowing stages of the European sea bass Dicentrarchus labrax L.: comparison of extruded and extruded/coated diets.

The stability of the coated lipid fraction of a standard weaning diet was verified by comparing growth and fatty acid incorporation for European sea bass fed diets with an identical formulation but prepared either by extrusion/coating or extrusion only. For each type of experimental diet, a (n-3) HUFA level of 1 and 2.5% of the dry diet was evaluated. European sea bass Dicentrarchus labrax L. were weaned and consequently reared for 23 days on the experimental diets in a recirculation system. A commercial weaning diet served as a control. Final individual dry weight of sea bass larvae weaned and ongrown for a total period of 30 days on the various diets did not differ significantly. The (n-3) HUFA content of the fish tissue was a reflection of the dietary (n-3) HUFA requirements of European sea bass during and immediately after weaning did not exceed 1% of the dry diet. The combined technique of cooking-extrusion of a basal diet followed by coating of a lipid emulsion proved to be a valid technique to prepare diets for studying quantitative fatty acid requirements of weaning and first ongrowing stages of marine fish. A standard diet with open formulation is proposed.