A study plan of development of a new device for recapturing free swimming fish

Abstract

Mekong giant catfish is one of the largest freshwater catfish in the world. It is endemic to the Mekong basin, and is endangered species. We have studied the Mekong giant catfish to conserve and enhance its resource by biotelemetry since 2001. In the Mae peum Reservoir in 2003, we found that the catfish vertically moved down only above the thermo cline in the daytime and up to the surface layer in the nighttime daily. This diel vertical movement appears to be related to the foraging behavior. However, the foraging behavior and prey items of the catfish are still unknown. One of the methods to clarify the foraging behavior and the prey items is to examine the stomach contents of the catfish in the daytime and the nighttime respectively. In order to examine the stomach contents transition hourly, we must be able to recapture the catfish at any time. Therefore, we made a plan to develop the new device named an Automatic Fish Recapture System (AFR System) to recapture the free swimming fish at the set time. And we will apply this device to the catfish and examine the stomach contents of the catfish and simultaneously study the migration of the catfish by incorporating with the biotelemetry system. Consequently, we will clarify the foraging behavior and the prey items of the catfish. In this paper, the outline of the AFR System and study plan of the catfish using this system is introduced.