Formes d'eutrophisation dans les étangs de cypriniculture
Sevrin-Reyssac, J. (1993). Formes d'eutrophisation dans les étangs de cypriniculture, in: Barnabé, G. et al. (Ed.) Production, environment and quality: Proceedings of the International Conference Bordeaux Aquaculture '92, Bordeaux, France, March 25-27, 1992. EAS Special Publication, 18: pp. 39-50
In: Barnabé, G.; Kestemont, P. (Ed.) (1993). Production, environment and quality: Proceedings of the International Conference Bordeaux Aquaculture '92, Bordeaux, France, March 25-27, 1992. Special Publication European Aquaculture Society, 18. European Aquaculture Society: Gent. 587 pp., meer
In: Special Publication European Aquaculture Society. European Aquaculture Society: Bredene. ISSN 0774-0689, meer
|
| Beschikbaar in | Auteur |
|
Documenttype: Congresbijdrage
|
| Abstract |
In intensive or semi-intensive fish ponds, the water remains a living environment in which plankton has an important effect on physical and chemical conditions. In these ponds, water receives an organic fertilization represented by fish wastes (more stimulating for phytoplankton than when it consumes natural food) and artificial food or cereals. Development of green algae is favoured by elimination (fish predation) of big cladocerans, consumers of important quantities of algae. Except for silver carp (Hypophthalmichtys molitrix), all the species of cyprinids eat large forms of zooplankton and, in consequence, induce phytoplankton blooms. A moderate density of phytoplankton is necessary to mobilize nitrogen, chiefly ammonia, but excessive development can provoke degradations of water conditions: important variations of dissolved oxygen concentration and pH values, mud formation resulting of cells sedimentation. A solution for limiting algal biomass consists in transfering water of fish ponds in another bassin containing big cladocerans where algae are rapidly consumed. The same technique can be used for valorizing less productive ponds. A part of their volume would be used for intensive fish breeding, the other one as an epurative medium; this system working in closed circuit would have the advantage to respect environment and, at the same time, to assure a complete control of the water. |
|
