Diel and tiday conditions are two important factors that influence fish behavior. Many fisheries, such as the Corvina fishery in the Gulf of Nicoya, Costa Rica, take advantage of these influences. This study applied stationary transducer arrays that allowed complete coverage of the water column while also measuring the velocity of fish movement. The information obtained from this application will provide insight into the efficiencies of the gill nets used in the fishery as well as independent estimates of the fish abundance.