During the period from 1981 to 1986, Campylobacter and Salmonella were isolated from healthy dogs and cats by the Nagano Prefecture Dog Pound Office. Campylobacter was isolated from 35 (7.0%) dogs out of 497 and 14 (10.1%) cats out of 138. Salmonella was isolated from 38 (7.6%) dogs out of 497, but not isolated from cats. The frequency of the isolation of Salmonella in puppies (under one year old) was about 2 times higher than that of adult dogs. A total of 42 strains of Salmonella was isolated from the dogs, and it was typed into 15 serovars. S. infantis, S. agona, S. anatum and S. paratyphi B, d- tartrate(+) were the most frequent serovars. Isolated Campylobacter strains were identified as C. jejuni (48 strains) and C. colt (1 strain). Considering these results, we were suggested that dogs and cats may act as possible sources of Campylobacter and Salmonella infection in human.

For the purpose of determining the effect of dredging on nutrients releasing from the sediment at the bottom of Lake Suwa after some of its sediment has been dredged, an experiment was performed to find out how much ammonium and phosphate would release from different depths of the sediment. Lake Suwa's sediment contains a lot of nitrogen and phoshorus down to its lower layers. The results of the experiment were as follows: The speed at which ammonium released from was faster as the depth of sediment increased. The speed at which ammonium was generated in the sediment showed the highest of 2.58N micro g/g dry sediment d in a 0-10cm layer. However, ammonium showed a generation speed of 1.3-1.4N micro g/g dry sediment-d at the depth of 10cm and more, indicating that ammonium easy to release from is generated even in lower layers. The speed at which phosphorus released from was 1.3-1.7Pmg/square m d in a 0-20cm deep layer, and 0.14-0.31Pmg/square m d at the depth of 20cm and more. The speed of Phosphorus releasing from lower layers of the sediment decreased to 1/4-1/10 of that in upper layers, and it was indicated that very little phosphorus flows out of the sediment at the depth of 20cm and more.