The Contribution of Naturally Occurring Food Items to the Diet of 'Bidyanus bidyanus' When Fed Differing Formulated Diets

Fish raised in ponds and fed formulated feed also have access to naturally occurring food items. The contribution of these food items to growth of 'Bidyanus bidyanus' was investigated by assigning fish to four treatments: in diet 1, caged fish were fed a high protein feed (52% CP); in diet 2, caged fish were fed a medium protein feed (30% CP); in diet 3, caged fish received no feed; and in diet 4, uncaged fish received no feed. Survival between caged treatments was similar (88%-96%), and fish performed best when fed a high-protein feed. Modelling of C and N stable isotope ratios showed formulated pellets provided 12% to 84% of the growth of fish fed diet 1 or 2, while invertebrates provided between 4% and 74%. The majority of growth of fish in diet 3 was from zooplankton (54%-76%) and invertebrates for fish in diet 4 (6%-94%). Implications for low intensity production of 'B. bidyanus' are discussed.