Every year flatfish fishermen are required to discard halibut that are caught along with their target fisheries. All halibut caught are counted against a cap and once the cap of halibut for a fishery is caught, the fishery closes. In past years most trawl fisheries for flatfish closed before the target catch quota was met because they reached their halibut cap. Therefore, there were large incentives to reduce halibut bycatch through avoidance of areas with high bycatch rates and through gear innovations that avoid halibut catches. To extend fishing seasons, fishermen developed programs to avoid areas where halibut bycatch was high and worked on a program to allow halibut to be deck sorted to increase their viability.
Thus far, no gear had been developed that selectively excluded all or even most halibut without reducing target flatfish. Such gear would be valuable to fishermen since less halibut caught meant longer seasons and better utilization of the resources. Halibut excluders that had been tested formally by NMFS and other agencies were shown to be ineffective. Many captains of trawling vessels came up with their own designs that they believed were effective, but were never tested scientifically to verify their performance. The experiment that Groundfish Forum proposed convened a panel of gear experts to review the designs that fishing companies developed on their own, selected the design that showed the most promise, and tested its effectiveness in an experiment designed to approximate normal fishing conditions.
Groundfish Forum invited every trawl company that fished for groundfish in Alaska to submit designs of halibut excluders to the panel. Four boats applied for the experiment and were reviewed by the panel on August 10th. F/T Legacy submitted the design that was selected for the experiment and the F/T Alliance was selected randomly from the remaining applications to participate in the field trial.
In September of 1998, the excluder was tested in the Gulf of Alaska deep water flatfish fishery. The vessels made a series of paired tows, one tow with the excluder and one without. The captain of the vessel selected an area for towing, and then the observer announced whether the tow would be carried out with the excluder or not. The first tow was made, and then a second tow similar in towing speed, depth, area and length.
The tow was sampled for species composition and amount of halibut. To ensure accuracy, a census of halibut was conducted on deck rather than the normal basket sample. Once the halibut was counted and measured they were released. By deck sorting the halibut, they spent less time out of the water and therefore had a greater chance of survival.
The results of the experiment were analyzed to determine if a significant reduction in halibut or target catch occurred. The analysis of the performance data and design for the excluder are public domain.