I had my first confirmed contact with a salmon on Saturday the bugger however got away after running five times

However I when I'm fishing I always think if the line goes tight its just a rock or a bit of weed because there is no feel of a fish moving like there is when you get a bite in a still water. But when I hooked into the fish the line went dead tight with no feeling of a fish moving and then started taking line, at which point I realised it was a fish and not the rock I had just pulled free from. Is this normal that the line tightens sharly and then just does slack or cna you normally feel it is a fish moving?
cheers
'
Mark