硫酸钡
A promising gillnet that is effective in reducing bycatch for harbor porpoises contains barium sulfate. These nets are detected at a greater distance than conventional nets because the barium sulfate reflects the echolocation signal, and also renders the nets more visible. Barium sulfate makes the nets stiffer if it is added at high concentration. All three factors: echo reflectivity, stiffness, and visibility may be important in reducing bycatch. Fish takes in the Bay of Fundy were normal, except for haddock takes, which were down by 3-5%. The advantage of this approach is that it is passive and thus does not require batteries, and there is no “dinner bell" effect. The potential advantage of these nets is greatest in the artisanal fishery. NOAA would like further testing to verify the effectiveness of the nets.