Critical to the success of any animal rearing technology is a consistent and reliable supply of nutritious and cost-effective feeds. The United States is a world leader in producing and processing feed grains and formulating feed for warm-blooded farm animals. Considerable progress has been made, using similar inputs and technologies, in formulating and manufacturing feeds for catfish and trout in freshwater aquaculture systems. However, little progress has been made on feed formulation for other aquaculture species, particularly marine species. Special challenges and opportunities include marine fish and shrimp diets that are heavily dependent on marine meals (fish, squid, shrimp, etc.), and the growth performance of aquatic species being fed diets high in plant-based ingredients. The objective of this multiyear research and development project, conducted by the Midwest Feeds Consortium (MFC), was to provide appropriate biological and economic information on the effectiveness of grain, oilseed, and animal coproduct-based protein meals common to the United States Midwest as replacements for marine meals in aquatic animals feeds. The quality, cost, and availability of marine meals are generally recognized as growing constraints worldwide. The United States has a substantial competitive advantage in feed grain technology and production, which can be leveraged to strengthen the competitiveness of the U.S. grain and feed industry provided that appropriate marine meal substitutes are found or developed. The work reported here established a basis for advancement in feeds and ingredient technology development for aquatic species as well as an economic assessment of the potential for the U.S. grain and oilseed industries. This project was initiated in September 1994, with approval of a one-year proposal and work plan. This work plan included a workshop held in Des Moines, Iowa, of both industry and project participants that established the framework for consortium activities. In June 1995, a second year of funding was approved to initiate the bulk of the research and development activities. In close cooperation with consortium members and with the approval of the United States Department of Agriculture/Cooperative State Research, Education, and Extension Service (USDA/CSREES), the second year work plan was modified with respect to particular ingredients and processes originally chosen, in light of revised expectations and potential opportunities. A total of one annual and five semiannual reports were submitted to CSREES over the four-year period of this project. This highlight report describes findings and accomplishments of special significance as judged by the investigators. The highlight report includes identification, discussion of priority findings and accomplishments, impact on direction and analysis, overall impact, and research needs and opportunities.