|dc.description.abstract||According to Norwegian law it is forbidden to discard dead or dying fish. With recent new information about mortality of pelagic fish species that have been crowded and released from purse seines, the Norwegian authorities have introduced new regulations for “slipping” (i.e. release of catch from purse seines while the fish is still in the water) in late phases of hauling a seine. The main objective of this project has been to develop technologies and methods that reduce the extent of unaccounted mortality after crowding and slipping in purse seine fisheries for mackerel (Scomber scombrus) and herring (Clupea harengus). The project has been guided by a combined steering and reference committee consisting of active purse seine fishermen, personnel from the fishing gear industry and from fisheries management, who have had the mandate to prioritize research tasks within the frames identified by the project plan.
According to recommendations from the steering committee the work has focused on the following two main research areas: 1) To develop methods and equipment for identification of species and catch quality/size in a seine during hauling. The aim was to give the skipper tools to decide whether a catch should be slipped or kept at a stage of hauling where the fish is still viable if released. 2) to develop methods, equipment and procedures for lenient catch regulation from a seine set, with as little stress, physiological load and damage to released fish as possible. The aim was to give the skipper methods and equipment for releasing catch in a responsible manner if slipping is necessary. It is also a goal that the slipping procedure may be approved as a standard method by the authorities.
Initially we tried to develop sampling methods based on permanent installations in the net and devices attached to it (i.e. bags built into the net walls and maneuverable landing nets), but with limited success. More successful is the development of a small sampling trawl that is shot into the seine with a line-thrower during net hauling, which was towed back to the vessel by using a small power block. This method showed a promising potential for use as a handy tool for catch identification, and it has now been developed to a stage where it can be tested by the fishing fleet at a commercial level. UV camera systems to be used as a tool for observing the seine net and the fish inside the net for scientific purposes have also been developed and tested. These systems may also in the future be further developed to commercial products for catch identification, but this has still a long way to go before it reaches a commercial level.
Much effort has been put into developing lenient slipping methods, based on technologies traditionally used by seine fishermen for live storage of pelagic fish. One key feature of a responsible slipping technique is that the net can be rapidly opened to make an escape route that is wide enough for the fish to swim freely out of the net. It is also important that it gives the fishermen the opportunity to shut the net when the desired amount has been released. This project has shown that by minor adjustments to components of the bunt (end section) of the seine, this goal may be achieved. This slipping system has the potential to be further refined into a standardized slipping method that may be accepted both by the authorities and the fishing fleet. The costs of adapting existing seines to the new method are low. The most expensive part will be connected to installing an extra winch for handling the opening ropes, if necessary. Further work on standardizing slipping technology is now being planned.||nb_NO