Ystwyth Goosanders

In reply to the question posed by CB and Tellbirding on the distribution of Goosanders on the Ystwyth - I saw a female with 7 youngsters upstream of Llanfarian yesterday afternoon. In previous years I have seen broods in the Trawscoed area.  This raises a further question as to what is the population size of Goosanders on our local rivers and their effect on the fish numbers?