1National Research Institute of Fisheries Science, Fisheries Research Agency, Ueda, Nagano 386-0031, 2Department of Marine Bioscience, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
An automatic bluegill trap (130 cm×80 cm×80 cm high) was developed to cull the number of bluegill in ponds. The trap has four entrances 10 or 15 cm in diameter for fish and has a space (50 cm×20 cm×80 cm high) in the frontal part of the trap to contain attractants for bluegill. A set of the traps placed in an experimental pond with bluegill and a native Japanese fish Pseudorasbora parva showed that bluegill were attracted to the trap significantly more than Pseudorasbora parva. As an attractant for bluegill into the frontal part, middle- and large-sized bluegill and dead branches were examined, and consequently only dead branches were found to have a positive significant effect. By housing a Far Eastern catfish Silurus asotus, a predator of bluegill in the trap, the predator showed an increase in its body weight. Therefore, the introduction of the trap with dead branches in the frontal part and Far Eastern catfish inside the trap into ponds and lakes is considered as a potential method to cull the number of bluegill efficiently and automatically with little labor effort.