As great diversity of gut anatomy and function occurs in response to the wide variety of foods found in nature, so also is there a great variety of methods to study digestion. This multiple diversity often makes comparisons between species impossible and comparisons within species using different methods difficult. Although the impact of methods on interpretation of results is always important in scientific experiments, the problems of methodology in studying fish digestion seem more severe than in most experimentation. Further, there are significant gaps in information about fish digestion, particularly in the areas of mechanisms controlling the gut, which have probably come about because of the lack of appropriate methods. 5. METHODS OF MEASUREMENT AND ANALYSIS FOR DIGESTION STUDIES