The microbiological state of fish feed, water, and Silurus glanis L. skin of fry during intensive rearing

摘要

Water, fish feed and fish skin were studied during the pond rearing of European catfish (Silurus glanis L.) fry. The numbers of heterotrophic bacteria cultured on broth agar at a temperature of 22°C and 37°C (TVC 22°C and JVC 37°C), heterotrophicbacteria cultured on TOY medium at a temperature of 25°C (TOY 25°C), total coliforms (TC) at a temperature of 37°C, fecal coliforms (FC) at a temperature of 44.5°C, fecal streptococci (FS) at a temperature of 37°C in the studied water samples variedas follows: 2000-44000, 750-5500, 8600-88000 cfu in 1cm~3, 1-300, 1-65, 1-95 in 100 cm~3. Pseudomonas fluorescens, Aeromonas hydrophila, and Pseudomonas aeruginosa occurred in 100 cm~3 of water at 300-5,000, 10-609, 0-8 cfu, respectively. The numbers ofTVC 22°C, TVC 37°C, TOY 25°C, yeast and mould fungi in 1 g of feed were 2200000-4500000 cfu, 290000-5000000 cfu, 1400000-4400000 cfu, 120-1500 cfu, and 70-1000 cfu, respectively. TC, FC, and FS varied as follows: 40-120 cfu/ 100g, 1-4 cfu/ 100g, 2000-35000 cfu/100 g. Pseudomonas fluorescens was noted at 2-70 cfu/ 100g feed; Pseudomonas aeruginosa and Aeromonas hydrophila were not observed. On 1 cm~2 of skin surface the numbers of TVC 22°C, TVC 37°C and TOY 25°C ranged from 10~3 to 10~4 cfu, whilethe amounts of TC, FC and FS ranged from 1-220 cfu, 1-3 cfu, and 1-80 cfu, respectively. Mould fungi occurred at 10 cfu/lcm~2 and yeast at 8-220 cfu/1 cm~2. Potentially pathogenic bacteria were observed in numbers ranging from several to several dozen cfu/ 1cm~2 of skin surface, depending on the bacteria type. Statistical analysis indicated significant differences (p < 0.05) in the occurrence of TVC 22°C, TVC 37°C, TOY 25°C, FC, Pseudomonas fluorescens, Pseudomonas aeruginosa and Aeromonas hydrophila in the water, fish feed and on the skin of European catfish fry.