A series of experimental prawn trawling tests with a simple trawl efficiency device (TED) was carried out in the vicinity of Yule Island, Papua New Guinea. The tested TED was designed to have a passive function with an inner funnel net and side windows to exclude finish by-catch, while retaining prawns. The TED windows were closed from time to time to represent an ordinary trawl net without TED. Catches from the two TED conditions, windows closed and opened, were compared in species composition and weight, number of fish, and size distributions of each generic group. Catch of prawn was reduced little when TED windows were opened. Exclusion ratios for finish by the TED varied from species to species, i.e. excluding 75.8% of javelinfish, while no exclusion was observed for ponyfish when the TED windows were opened. A trend of exclusion of larger species and larger individuals of finfish was observed. The different exclusion ratios are conjectured to be attributable to different swimming abilities of fish species due to body forms and sizes. Behavioral differences due to different dwelling patterns may also be a factor.
