Water quality and yields in a polyculture of nonnative cyprinids in Mexico

An experimental polyculture of Asiatic and Chinese cyprinids was carried out for the first time in Mexico in order to compare three kinds of fertilizers: fermented liquid sheep and pig manure and mineral fertilizer (urea plus complex compound). Nine ponds divided in blocks were used; each pond was stocked with five species of carp: grass, silver, bighead, wuchang fish and big belly carp, with a density of 1.5 fish/m2. Water quality parameters were calculated to obtain the yield in each treatment. In all the treatments the temperature, conductivity, sodium, potassium, chloride, total hardness and total alkalinity values were similar and DO, ammonium, nitrites, ortophosphates and net photosynthesis exhibited differences between fermented liquid maure and chemical fertilizer. Phytoplnkton ws represented by 40 genera, 16 of them were found more frequently. Chlorophyta were the dominant group throughout the experiment. No statistical differences were registered in the yields between tretments