Comparison of ship and aerial surveys of sardine schools

Field tests were made to compare estimates of sardine schools resulting from simultaneous ship and aerial observations. The aeriallship observations were performed around an area where large catches of sardine have been taken. In the surveyed area, the sardine schools can be sighted from the air and counted easily, making direct counting very advantageous. The schools are distinguished by their dark color against the lighter background of the ocean. A comparison of density estimated with the two types of survey are discussed here. Aerial counts of schools were 16.5% of those from the ship. This may be caused by the differences in visibility afforded by the two methods. Direct detection of schools and counting may be used more widely in the future.