Entrance shape of fish trap and fishing efficiency

The ingress and escape behavior for a fish trap was studied through experiments in the laboratory using green fish Girella punctata. The fish behavior for a simplified funnel set in the aquarium was recorded on video tape. An index of structure for various sizes of funnel-shape entrances was introduced as a means of analyzing the entrapping difficulty. The following results were obtained: The number of fish entrapped was constant when the index was less than 1.0, but decreased when the index increased above 1.0, while the number of escaped fish decreased slightly as the index increased.