The fact is, there are so many factors, it may not be possible to pick one out. I was just taking a look at the oregon pink fishery by-catch numbers. They have a 5% by catch rate, which they point out is low. But, consider that this is out of 30 million pounds, meaning around 1.5 million pounds. They filter out a lot of the larger fish, so this leaves mostly small fish. So what are they taking. Are they mostly smelt. What if only a 1/10 a percent are steelhead smolt. That would be 1500 pounds. At 2 per pound, 3000 disappear. Repeat this over and over, and we have death by a thousand cuts.