Determination of a Plant Protein Diet for a Marine Fish

Cobia are carnivorous marine fish that do not school in the wild and therefore are not hunted by most fisheries. This lack of market competition as well as very high feed and growth efficiency make cobia a great aquaculture species. Many common commercial aquaculture diets, and some diets for terrestrial animals, are made largely from fish meal. This is however not ecologically sound and may not be sustainable in the future as fishing pressures increase. Plant protein can greatly reduce if not eliminate need for fish meal in marine aquaculture. The goal of this study is to formulate a completely plant based diet for a carnivorous marine fish. Digestibility of plant protein components was done first by using a 100% fish meal diet as a control and a non-digestible marker as a normalizer. Known proportions of components of a plant based diet formulated for trout were mixed with fish meal and fed to juvenile cobia. The cobia remained on each diet until enough feces was collected to analyze apparent digestibility of each component. Feces were collected using the stripping method. Fillet samples, whole fish, diet components as well as the trout custom diet and a Zeigler marine grower diet were bombed to determine the total energy. The results show that fish fed the custom diet grew faster and had more energy in their body than fish fed the Zeigler diet. (P=.0010) Techniques such as lipid extraction, amino acid analysis and microwave digestion will be employed to determine the proportion of each dietary component in the final, tailored plant protein diet.