When I was the U.S. Advisor for Enforcement for the North Pacific Anadramous Fisheries Commission in the early 2000's (the high seas drift net bunch) I was amazed to find out that basically no research was done into steelhead catches, or interception. It was all about the salmon. From what little I learned, it looked to me that there was a good likely hood that they were intercepted to a degree in the far western Pacific by high seas drift net illegal fisheries after squid. I was able to make some in roads to make steelhead more of a priority but things changed politically, and new powers to be quit looking at steelhead. Gary Smith of Slade Gorton's Office supported steelhead research, but after Gorton left office, steelhead support disappeared. I don't think anybody really knows where most of the steelhead travel, but there are lots of theories.