Dear Dmitry,

Please check the attached links.

Best,

Tharindu.

http://link.springer.com/article/10.1007/BF00157583

http://onlinelibrary.wiley.com/doi/10.1002/jez.1996/full

I don´t know about the climbing perch but in case of glass eels (Anguilla anguilla), climbing behavior during their upstream migration seems to be linked with increased cognitive abilities (increased expression of cognition-related genes in brain), which in turn could be explained by a switch in the perception of environemental cues. Indeed, those fish rely a lot on the olfactory cues in the water, but they could be prone to use other (visual?) cues once out of the water. How do they choose the direction? They could follow the same climbing path than the previous ones: each fish leave a bit of mucus while climbing the wall. How do the first fish choose the direction? Probably by the trial/error process, led by high motivation to migrate upstream (thyroid hormones) or to explore the new environment (boldness/ risk-taking behavior). The whole process by which the "best" climbing direction in group is established and maintained could be similar to the one in ants (shortest way->more attractive and volatile pheromones remaining on the path-> their "run towards the strongest pheromone"  closing the loop).

Thank you Tomasz! You are absolutely right concerning fish orientation in the water. Fish migrations in general is a very interesting and extremely popular topic. Unfortunately the specificity of terrestrial (and air) conditions for fish behavior, physiology and, ultimately, orientation is not clearly understood.

Thank you Tharindu Ranasinghe! I know this paper but I can't find answers there.