Just to point out Dennis' post regarding hook size. Not sure if a chosen hook size would make one more or less ethical, but hook size can have some impact on a released fish's mortality. Most likely it has little effect on steelhead unless your hook is extremely big or small, but it can make a difference on the trout/juvenile salmonids that you by-catch. For example, in late spring, summer and early fall, when targeting steelhead, chinook, coho, there are times when you'd come across a juvenile steelhead or small trout. If a larger hook is used (1/0, 2/0), it has a tendency to go directly through the small fish's head and instantly kills it. That has occurred during my outings while targeting coho in September so I have made changes in the hook sizes that I use during certain time of the year. Hooks with a bigger shank can also do more damage, eg. create a larger gash and result in too much bleeding.
Of course, one can always say that if we are so concerned about this, then we should stop fishing totally, but it is just something to consider. Little changes can sometimes make a huge difference IMO.