"It's no fish ye're buying-it's men's lives." This study makes effort to clarify the causes of collisions with the Pair Trawlers, inter alia, collisions with their gears, and considers amendment of Municipal Avoidance Rules and the International Regulations for Preventing Collisions at Sea in order to lower the incidence of such accidents. The Pair Trawlers towing a net can cover larger water column than other fishing boats and can scoup up larger quantity of fish. Their good coverage increases the danger of being collided by other ships while fishing and their delicate operation requires a well-developed technique and mutual understanding among their seamen. To make matter worse, it is quite difficult for vessels in a head-on situation with the pair trawlers to discern wether they are towing a net between them. As for pair trawling, collision avoidance rules provide only that each vessel engaged in pair trawling may exhibit, by night, a searchlight directed forward and in the direction of the other vessel of the pair. Inappropriateness of these provions was illustrated by the accident on the 13th of January 1997 south of the Saishu Island where a Panamanian cargo vessel went through between F/Vs the 17th and 18th Choun-maru registered in Japan and dragged their net and sank one of them to involve the death of ten drowned fishermen. Seriousness of this kind of accidents suggests that inappropriateness of the avoidance rules amounts to lacune du droit on this point. Besides, the UN-LOS, by its article 97, reserves criminal and disciplinary jurisdiction to the offender's State or the flag State in all incidents of navigation leaving the victim's state no power to investigate, prosecute or punish offenders and offenders' vessel. To stop buying fishermen's lives in the form of fish, we propose for the starboard-side vessel, during night time, to shed green searchlight directed forward and in the direction of the other vessel of the pair and for the port-side vessel red searchlight so that they can show, at the same time, their engagement in fishing, their towing fishing gear between them and their heading direction. Laser light may be made use of, if it could be practicable and effective. During day time, green and red flags should be hoisted respectively by the starboard-side vessel and the port-side vessel as some Japanese fishing vessels are already practising. The two trawlers may have to mark their masts in the same way to show their operation in a pair. Floating buoys fastened to the net of pair trawlers may be obliged to have reflectors and to be painted in green on the sarboard-side and red port-side. These proposals should be incorporated into collision avoidance rules to bring the principle ignorantia juris nocet into operation. As British regulations, after the sinking of the Antares, ordered that submarines should keep 4, 000 yards away from fishing boats when underwater and 1, 500 yards when operating at periscope depth, so states can limit the licenced sea fishing grownds and fishing time of a day or even prohibit pair trawl fishing on the congested sea area. Large ships with restricted manoeuvrability, should inform their position to international authority through satellite whose surveillance should be enhanced throughout the world.