Heh heh, that was over a month ago Mr R, but thank you very much anyway!

I must try and capture some more recent images.
Janne, we are basing this theory on a couple of us witnessing the act of spawning in the aquarium. Indeed, when I saw mine (recently), they rose high up into the water column when they released the eggs/milt. If this is representative of what happens in nature, then the force of the water would no doubt quickly wash the fertilised eggs downstream. As you may have seen, their natural habitat consists of large expanses of flat boulders, so there would be no sensible reason for them to attach the eggs to this sort of surface 'right out in the open' and therefore available to predators. There is probably a greater chance of more of them developing if they are washed into safer areas, perhpas where there is more natural cover?
Emma