M. Dehasque, T. De Wolf, P. Candreva, P. Coutteau, P. Sorgeloos
Abstract :
Further intensification of production in marine fish hatcheries during recent years has resulted in an increased demand for high quality feeds and more rigorous control of environmental conditions. Stress conditions induced by higher stocking densities and handling in large-scale operations make fish fry more susceptible to infection by opportunistic bacteria. Adequate nutrition and hygienic husbandry procedures are the most important tools of the hatchery operator to protect the early fish stages against disease outbreaks since vaccine development and drug treatment is hampered by biological and legal restrictions.
Especially in larval rearing, the live food is suspected to be a major source of contamination. The rotifer Brachionus plicatilis and the brine shrimp Artemia, which are the prevailing live food used for the early stages of fish, are indeed highly contaminated with bacteria. A major part of this flora is consisting of Vibrio sp. which are potential fish pathogens. Therefore it is of vital importance to culture live food in the most hygienic circumstances. Besides the hygienic aspect, due to the growing demand, intensification becomes a must. Therefore it is important to be able to produce more live food within the same facilities without endangering nutritional and zootechnical aspects. This paper compares various disinfection procedures for rotifer and Artemia production. Till today, no satisfactory procedures have been developed for the disinfection of rotifers and ongoing research is presented. Various innovative products and procedures have been developed recently for the disinfection of Artemia during hatching and/or consequent enrichment, resulting in a 10,000-fold reduction of the Vibrio load compared to traditional methods. Furthermore, the low bacterial load during hatching and enrichment allows higher Artemia densities and reduces the need for oxygen injection and tank volume.
(Inve Technologies NV, Oeverstraat 7, B-9200 Baasrode, Belgium)