There was a study published last year about QFASA used to determine the diet that contributed to the stored fat of sampled harbor seals.

My impression was that harbor seals like humans might have individual preferences on what they eat on the seafood menu but that isn’t to say if a convenient free meal showed up the seal wouldn’t hesitate to gobble it down.

Interestingly,” Rockfish were estimated to compose up to 50% of some individual seal diets. Although estimates of harbor seal diet composition varied spatially, demographically, and among individual seals, species of rockfish were estimated to compose a large proportion of the diets of several individual seals.”

The conclusion was “our findings confirmed the importance of salmon species and Pacific Herring in harbor seal diets, but they also revealed that other species, including rockfish species, may contribute more substantially to harbor seal diets than had been realized previously.”

Also, I was sort of surprised about the amount of dogfish that is in the seals diet.

I don’t know if it was unfortunate, insignificant, or intentional that steelhead weren’t mentioned in this paper but hopefully the experiments being done in the first post of this subject-topic by Phoenix 77 will shed some light.

The question shouldn't be if the seals are eating steelhead but the question should be how many.