The research on the biological assessment of bangus, shrimp and eel fry in Luzon, Visayas and Mindanao were ushered in by investigations of the physico-chemical conditions that exist in selected fry grounds during the peak fry seasons in 1974.
The survey conducted in the Visayan islands showed that the distribution of the environmental conditions in a given fishing ground has a deep influence on. periodic and seasonal migration and occurrence of fish. The physical and chemical factors influence the abundance of the food indirectly, and the abundance of these species in the fishing areas directly. The results of the survey give us an idea of fish behavior with respect to the environmental conditions.