Physiological pH values in the digestive tract of perch Perca fluviatilis from different habitats

Physiological pH values are determined in the gastrointestinal tract of the perch Perca fluviatilis from lakes Chany and Baikal. Values of pH are detected to vary significantly along the digestive tract. Such factors as a segment of the digestive tract, presence/absence of food, season of the year, and habitat affect pH values. Environmental temperature is the main factor affecting pH values that is confirmed by the decrease in pH values upon water temperature rise in spring, lower pH values in summer compared to other seasons, and lower pH in fish from the waterbody (Lake Chany) with higher temperature of water.