Nutrition in the Carp with Special Reference to the Morphology of the Gastro-Intestinal Tract and to the Effects of Temperature

Abstract

An enclosed recirculating aquarium system was constructed to hold carp which were subjected to variations in feeding regimes and water temperatures. The digestive tracts of these fish were examined for changes, by histological, histochemical and biochemical methods. These carp were considered to be derived from varied stocks, therefore, from previous experience on the histology of wild fish, and the variables which could occur, a sample of the carp were examined histologically to provide base line data for the experimental samples, also the techniques for sampling and biochemical enzyme analysis were investigated. There was no significant differences detected in the digestive tracts of carp fed two diets containing different protein levels, nor were there significant differences detected in fish which had been fed or starved at a temperature of 17°c. However, when the temperature was raised to 27°c significant changes were recorded. These were increased cellular activity, more mucin production, a greater fluctuation in liver glycogen levels and a higher enzyme activity of the digestive tracts. A further study also showed the total serum proteins were increased at the higher temperature. The overall conclusion was that when the temperature was raised sufficiently, the metabolic rate was increased, thus enabling the carp to absorb proteins more efficiently, and this was particularly evident when carp were starved at the higher temperature and tissue degeneration and depletion occurred.