Behavioral Observations of White Spotted Conger Eel Conger myriaster in Baited Traps in Tokyo Bay

Abstract

Fishing equipment has improved considerably based on the experience fishermen. However, most of these developments have not considered actual observations of fish and their interactions with fishing gear. In the conge reel tube fishery in Tokyo Bay, fishermen have increased the size of escape holes in the tubes to 13 mm in order to reduce by catch of conger eels that are too small for sale. However, the effect of these escape holes on the effectiveness of the trap has not yet been clarified. We developed an underwater video camera system capable of recording approximately 12 hand used this system to observe the behavior of white spotted conger-eel Conger myriaster caught in conge reel tube traps in a conge reel fishery. Field experiments were conducted once a month from over a 6 month period from June 2011 to December 2011. The video camera successfully captured the following aspects of conge reel behavior: approaching the tube, entering the tube, feeding, escaping from the entrance, escaping from escape holes, and stealing bait. In addition, the video-camera also captured other fish species in the traps. The following responses were obtained when the footage was shown to fishermen: 'Just as I thought', 'Solved the mystery of how bait is stolen' and 'Fish are intelligent 'The results clarified how the traps work and provided useful information on how the traps could be improved.