Over the years I have found stuff in the stomachs of a several dozen different steelhead, both winters and summers.
I also can report finding odd late summers/early winters with the chums eggs (usually a handful in their stomachs). The first couple years that the NF Stilly was open in November (years ago most rivers used to close at the October and re-open December first) the hot bite was the first deep water below the spawning chums - interesting enough the fish would take virtually any fly we showed them.
Other food items I have seen in their stomachs include egg clusters, various pieces of sand shrimp, a whole 6 inch spot shrimp, periwinkles, mayflies, grasshoppers, and a sculpin. The interesting thing about all the food items is that I have never seen anything in the fish's stomach that I could not identify, everything look fresh and whole. When one looks at the contents of most feeding fish's stomachs such as a trout most of the items are in some state of parial digestion - not so with steelhead, at least in my experience.
It appears to me that once the fish are in the river their digestive processes shut down and even if they happen to swallow something they gain little or no benefit from it. This is further support by an experiment at Reiter in the 1980s were the summer brood stock were taught to feed on trout pellets (had to put several trout in with them which seem to teach the steelhead to feed). The thinking was that if the steelhead would feed their condition could be maintained until spawning 6 to 10 months later. Even though they seem to eat with vigor there was no corresponding increase in the condition of the fish at spawing. When the fish were killed at spawning they had no more fat - that to say none then when the fish were not feed. Thus it continues to be my belief that while the fish may occassional swallow an item or two they are not really feeding.
Other items have included various feathers, including a whole water dipper, pebbles, twigs, leaves, and one that had two pearl shirt buttons - how one fish found two different buttons I could never figure out but perhaps a button thread on a leader might be the next hot lure!!
Tight lines
Smalma