Dr. Cathal Gallagher:

It is always a question because, as someone used to say to me, we are not counting cans of beans on a shelf. We are counting all of these fish coming back in 140 rivers. We have counters of various types. Many of them are full cross-river counters, which count all the fish, and then we have some partial counters. In the case of partial counters there is free passage on either side of the counters, with fish going over them in the centre. We do experimental work to look at the proportion that moves to each side to get a count. We have numbers coming back. We also rely on angling returns. The other piece of information we take is that we survey using electrofishing to see how many juveniles are in particular parts of the catchment. This tells us how well the returned adults and their progeny are doing. All of these pieces of information are looked at annually for 144 rivers. This includes anglers' returns. It is not just one piece of information that adds into how things are doing.