Here we gave loaches the opportunity to climb a waterfall over a glass sheet.

They were enthusiastic and climbed the sheet without any interference from us. We had been thinking of activities to avoid boredom in captive fish – but that’s another story – here we embedded a small hole in the glass sheet and measured the suction as the fish moved over the hole and we could then observe how the suction changed under the body of the fish – it was very interesting.

I wrote a GUI to analyse the videos. Here you can see the target, where the pressure sensor was on the fish body on the bottom right, coloured to indicate suction pressure, and, along the top, the pressure measurement itself, over time.