In my opinion the fish in the fraser typically are not affected as much by the rain,the river is much bigger and carries a higher volume of water,the main thing that pushes the fish up the river is the changing of the tides,they typically move up river on an incoming tide which not only gives them more water to move upstream in but it also allows them easier access moving with the tide change rather than swimming agianst it,while smaller streams are more affected by the rains it really only makes a big differance when the water in the stream is very low,this is when most of the fish will wait for rains to raise the water levels to give them easier access up river.