That fish in the pic surprises me. It’s a female and at this time should be full of eggs and thus much more plump. It’s unlikely that it spawned already and I further discount that because the caudal fin is in good shape. I can only conclude that it is a female that either is not producing eggs each year due to environmental or health conditions or because it is one of the females that naturally exhibits biennial spawning.
Poor environmental conditions could include warm water, given this past summer’s temps and low flows in the region. It could be that this fish spent part of the summer in the much warmer Lehigh R before entering Saucon Ck.(unless there is a blockage between the river and where this fish was caught).