Laboratory measurements of digestion rate in 0-group flounder (Platichthys Flesus L.) at two temperatures

Abstract

O-group flounders (Platichthys flesus L.) were allowed to fill their stomachs with live polychaetes (Nereis diversicolor), and to refill them after various periods of time. At both feedings the amount of food eaten was estimated. Assuming that the fish fill their stomachs to the same degree at both feedings, the amount of food eaten at the second feeding is equal to the amount digested between the two feedings, and the stomach content immediately before the second feeding can be calculated as the difference between the amounts eaten at the two feedings. By noting the degree to which the filled stomach expanded the body wall this assumption was found valid. An exponential model was fitted to the results: SC_h = SC₀ · e^-r·h, where SC_h and SC₀ are the stomach contents at time 0 and h, respectively, h is the time in hours and r the rate-constant. At 10 °C r is estimated as 0.14 hour^-1 and at 15 °C as 0.21 hour^-1, which means that 13, respectively 19 % of the stomach content (weight) is digested every hour. The difference is statistically significant, and reflects the effect of temperature on digestion rate.