An interesting question about when Salmon pair, I have been fortunate to fish for over 40 years on a small spate river in N.Wales, that, when the water subsides you can often watch the fish in their lies (if you know where to look). I have seen cock fish early in the season (August for our Salmon) "defend" a Hen fish in her lie from other fish parr/brown trout included. As the season progresses this becomes (for obvious reasons) far more apparent often to the point of seeing a good size Hen lying alongside a rock with good number of smaller Cock fish vying for position roundabouts, many bearing the scars of battle! On quite a few occasions I have hooked & played a fish only to be able to see every move of the captive followed by one or more fish, this always results in the caught fish being a Hen. As Aenoon has said it is a fact used by anglers on the river who know where a Hen is lying to either fish a large red fly or cast a simliar spinner to agitate the Cock fish in to attacking. I once had a heart stopping moment as a fish of around 12lb literally tore across a pool in pursuit of a 3" Rapala fished mid water, there was a huge bow wave & a splash & swirl as it struck the Rapala at my feet (I was on a bank a couple of feet above the water). The odd thing about that was, as I could see the whole episode from on high, the fish never opened its mouth to "take" but just seemed hell bent on ramming the plug.
