David Chalmers' blog has a post which links to 2 papers on the subject of fish consciousness. After skimming both, the article by Rose (which is skeptical about fish experience) appears to be based on a flawed premise, which is that experience in humans is generated by the neocortex. While the distinctively human cognitive apparatus resides in the neocortex, experience itself can be traced to older (in evolutionary terms) structures. As pointed out in the other paper by Chandroo et.al. and importantly buttressed by the papers in the recent issue of Consciousness and Cognition which I linked to in my recent post, areas such as the thalamocortical system are strongly implicated in experience, which supports the idea that it is shared more widely in the animal kingdom.
Since that last post, I read most of the other articles in the Consciousness and Cognition issue. My favorite was "Identifying hallmarks of consciousness in non-mammalian species", which discussed the avian case as well as the possiblity of some conscious awareness in the octopus! This is an interesting potential case of convergent evolution which wouldn't depend at all on the particular neural structures of vertebrates.