Sanitary and bacteriological evaluation of common carp, tench and crucian carp reared in a pond supplied with biologically treated sewage

Abstract

Bacteriological contamination of muscles, skin, and digestive tract content of common carp (1+), tench (1+, 2+), and crucian carp (1+) reared in a pond supplied with biologically treated sewage (sewage treatment plant in Jedwabno, Masurian Lakeland) was studied in 1995 and 1996. Common carp, tench, and crucian carp at the age 1+, examined in 1995, lived in the pond for one season (about 6 months). Tench 2+, and crucian carp 1+, examined in autumn 1996, were obtained from spawning of 1995 and their entire development took place in the pond. Muscles of all 3 fish species contained high numbers of bacteria determined on broth agar, at 20 and 37°C, coliforms, fecal streptococci, and Aeromonas sp. In 1996, also fecal coliforms, and sporadically Pseudomonas aeruginosa and Salmonella sp. were found. In the muscles, skin, and digestive tract content of common carp reared in 1995 and 1996 numbers of coliforms, fecal coliforms, and fecal streptococci were similar. The muscles, skin and digestive tract content of tench and crucian carp contained higher numbers of bacteria in 1996 compared to 1995. Numbers of bacteria determined on broth agar at 20 and 37°C, coliforms, fecal coliforms, and fecal streptococci in the muscles, skin and digestive tract content of fish reared in a sewage-supplied pond reflected their densities in water, often exceeding critical concentration of 5 x 104 CFU per 1 ml of water for TVC 20°C and TVC 37°C.