|Intensieve produktie en kwaliteitsonderzoek van Artemia adulten en hun nakomelingen|
Lavens, P. (1989). Intensieve produktie en kwaliteitsonderzoek van Artemia adulten en hun nakomelingen. PhD Thesis. Rijksuniversiteit Gent. Faculteit van de Landbouwwetenschappen. Centrum voor Artemia-onderzoek: Gent. 435 pp.
Parallel with the explosive development of aquaculture interest in Artemia has increased tremendously. However, further optimization of the application of this live food in the culture of fish and crustaceans remains essential. This implies, besides the development of specific technologies, also a better knowledge of this organism, e.g. with regard to factors controlling the hatchability of the cysts or the nutritional characteristics of the nauplii. This type of research requires, however, well defined cyst material which is not available from commercial sources, as the variability among cyst samples is too high. In this regard a culture system was developed for the controlled production and collection of Artemia cysts under specific conditions. Based on a detailed literature review of biological aspects on culturing, feeding, and reproduction, a flow-through installation was developed for the production of adults in a recirculation system. The system basically consists of a culture unit of six 300 1 tanks each provided with a special filter module, a recirculation unit with plate separators, a cross flow-sieve, and an U.V.-installation, and a stock tank. Using this new culture system the following results were obtained: the new filter technique is more efficient in evacuating the polluted water from the culture tanks compared to the traditional nylon screens; in this way culture conditions can be better controlled; water quality can be maintained at acceptable levels of N-components and BOD5; mixed diets consisting of soya bran Kluyveromyces yeast give the highest levels; optimal population culture densities up to 10,000 brine shrimp/1; several Artemia strains can be used as inoculum with this biomass production unit; within a culture period of 14 days survival and growth average 55 % and 5.5 mm respectively, giving yields of about 12 kg wet weight of adults per m³ of tank volume. Using the experimental data the culture procedure has been standardized by the adjustment of flow rates and feeding rates in function of the developmental stage of the Artemia. Only one aspect, i.e. the infection with Leucothrix, can hardly be controlled: contamination may be overcome by applying a salinity stress in combination with higher renewal rates of the culture medium. This concept was adapted under controlled conditions: based on the biomass' wet weight of the opulation a new feeding strategy was established to culture adult Artemia for long periods of time without affecting the reproduction activity; a suitable induction technique was developed resulting in 90 % oviparity without affecting survival, fecundity or culture conditions: from the juvenile stage onwards cyclic oxygen stresses by means of N2-flushing are applied in the presence of Fe³+-ions. If stresses are given from later stages onwards the first brood will be invariably ovoviviparous; a method for continuous harvesting and processing of the cysts was developed: With this installation sufficient quantities of standard cysts were obtained from different strains and produced under specific circumstances of temperature, salinity, and diet in second phase we tried to adapt the above mentioned techniques in order to develop a standard procedure for the continuous production of liveborn nauplii: a culture procedure which assured minimal stress situations or fluctuations in environmental parameters appeared to be the best induction strategy for ovoviviparity; best results in ovoviviparity induction were obtained with baker's yeast or alcohol yeast as food source; an efficient recuperation technique for automatic harvesting of the produced nauplii was established. The different cyst and nauplii collections harvested from our laboratory installations were characterized with regard to the following characteristics:diapause and hatching characteristics: biometric characteristics: biochemical composition - naupliar viability under starvati