Ethiopia is endowed with several water bodies that contain a high diversity of aquatic fauna. This book contains the diversity and relative abundance of fish species of the Baro and Tekeze drainage basins, Ethiopia. Fish identification was done to species level by comparing the specimens using meristic and morphometric characters with taxonomic keys. 9 orders, 20 families, 43 genera and 59 species were identified from the two basins. Aplocheilichthys kingii was recorded in the present study; so far it had been recorded only once in Ethiopian water bodies. In addition, the book contains identification keys for each species identified during the study period. The work was done in collaboration with Cornell University (USA). Therefore, this book will give more information for those who wants to study the diversity, relative abundance and biology of fish in any where and especially for African countries.