Potential Consequences of Applying the Wrong Model

The additional nutrients will support other species in the stream (e.g. resident trout and small fish or algae).
These species will prey on fry or compete with juveniles more.
Shift ecosystem from a salmon stream to a stream dominated by resident species.
Raise nutrient levels to point that areas with adequate sunlight grow enough phytoplankton to create severe swings in dissolved oxygen (areas without sunlight could also become low dissolved oxygen due to bacterial utilization of carcass material).

The additional nutrients will support other species in the stream (e.g. resident trout and small fish or algae).