Nguyen Van Hoa

Thermal resistance, developmental rate and heat shock proteins in Artemia franciscana, from San Francisco Bay and southern Vietnam.

Cysts (encysted gastrula embryos) of Artemia franciscana collected from salterns in San Francisco Bay, California, USA (SF) were inoculated into much warmer growth ponds in the Mekong Delta region of Vietnam (V) in 1996. V adults arising directly from these cysts during 17 April to 15 May produced their own cysts, which were collected, processed and stored until shipped to the USA for study. Adults grown in the laboratory from SF cysts (those used for the inoculation) were less resistant to high temperature than adults cultured from V cysts. V cysts produced heat-resistant adults, even though cultured under the same laboratory conditions as SF animals, at much lower temperatures than they ever experienced in Vietnam. Differences in thermal performance between SF and V adults were retained in the second generation, cultured from cysts produced in the laboratory by first generation adults, suggesting a genetic basis for the better heat resistance of V adults. We propose that the operation of natural selection in the Vietnam growth ponds produced adults with improved thermal tolerance, and that the basis for this tolerance was incorporated into the developmental program of their cysts. Surprisingly, differences in heat resistance of laboratory reared animals were not reflected in constitutive levels of the hsp70 family which were similar in first generation SF and V adults. A conditioning heat shock (HS, 37 degrees C, 30 min) led to the same level of induced thermotolerance in SF and V first generation adults when evaluated 24 h post-HS. Levels of hsp70 were also up-regulated at that time, but to about the same extent in SF and V adults. Developmental rates of SF cysts used for the inoculation were faster than those of cysts produced in Vietnam when both were incubated at 21+/-1 degrees C, suggesting that V cysts have become adapted to develop at higher temperatures.

Formulated Feeds Containing Fresh or Dried Artemia as Food Supplement for Larval Rearing of Black Tiger Shrimp, Penaeus monodon

Supplementation of microalgae and Artemia nauplii with practical formulated feeds containing fresh or dried Artemia biomass for larval rearing of black tiger shrimp, Penaeus monodon, was assessed. Five feeding treatments were carried out in a recirculating seawater system with fifteen 30-L fiberglass tanks. Shrimp nauplii were stocked at a density of 150 L−1 for 23 days. In the control treatment, live feed was supplemented with commercial formulated feed (Inve Aquaculture NV, Belgium). In two other treatments, live feed was supplemented with a pelleted feed based on either fresh or dried Artemia. In the remaining two treatments live feed was supplemented with a combination of 50% commercial feed and 50% fresh or dried Artemia feeds. Overall, performance of PL in the combination treatments (commercial feed and Artemia diets) were equal to or better than those fed commercial feed alone as seen by the better growth rate and higher resistance to formalin stress. The results indicate that feed containing fresh or dried Artemia biomass can partially supplement live feeds for larval rearing of P. monodon.

Applied Biofloc Technology for Target Species in the Mekong Delta in Vietnam: A Review

BFT (Biofloc Technology) has been currently applied in Cantho University to a number of targeted species from fresh-to marine and saline water species in the Mekong Delta, e.g. striped catfish (Pangasianodon hypophthalmus), white leg shrimp (Litopenaeus vannamei), tiger shrimp (Penaeus monodon) and Artemia Vinhchau strain (Artemia franciscana) for both in the lab-scales or production scales. The best growth and survival rate of striped catfish was obtained in 6‰. For white leg shrimp, the results indicated: (1) C (Carbon) source e.g. rice-flour or molasses supplementary based on the feed provided to promote survival, growth and shrimp biomass harvested; (2) it was fed less than 20% as usual but showed similar to those in the control; (3) combination of rice-flour and molasses at a ratio of 70:30 by weight of C and N (Nitrogen) in a ration of 15:1 enhanced shrimp survival and growth; (4) in intensive culture, shrimp could be against the infection of disease and end up with higher survival, growth in earthen ponds. For tiger shrimp, a set up for larvae till post larvae at different ratios of C and N and C:N of 30 PL15 displayed with better survival rate (49.73 ± 7.07%) and production (74,596 ± 10.608 PL/m). Artemia franciscana was set up at C:N = 10:1 and salinities from 35, 60, 80 and 100 ppt. After two weeks, there were no significant difference among treatment and the control (without biofloc) in term of survival and growth. Moreover, total embryos per female was not significant different with the control and even the number of embryos as cysts tended to be higher. BFT displayed its advantages when applied on culture system of different targeted species and there is no doubt that it could help to sustain aquaculture and save environment in the Mekong Delta in near future.

Microbiota of Salt Lakes as Food for the Brine Shrimp Artemia

The brine shrimp Artemia is often abundantly found in hypersaline environments.The larvae(‘nauplii’)hatching from its dormant embryos(‘cysts’)are a crucial live food item for the larval stages of fish and shrimp in aquaculture