Small species such as herring, sardines and anchovies are the cheapest source of nutritious fish found in many low and middle-income countries, and are often caught in large volumes in the waters of nations where people are experiencing malnutrition, researchers have found.Small species such as herring, sardines and anchovies are the cheapest source of nutritious fish found in many low and middle-income countries, and are often caught in large volumes in the waters of nations where people are experiencing malnutrition, researchers have found.