"Handedness" in Fish

Look closely at the two scale-eating cichlid fish Perissodus microlepis above. See how their mouths are slightly asymmetric? For example, the mouth of the fish on the left curves slightly to the right. That, translates to handed foraging behavior:

... an asymmetric ‘left’ mouth morph preferentially feeds on the scales of the right side of its victim fish and a ‘right’ morph bites the scales of the left side. This species has therefore become a textbook example of the astonishing degree of ecological specialization and negative frequency-dependent selection. We investigated the strength of handedness of foraging behavior as well as its interaction with morphological mouth laterality in P. microlepis. In wild-caught adult fish we found that mouth laterality is, as expected, a strong predictor of their preferred attack orientation.

So, despite having no hands, fish can be left- or right-"handed" (or perhaps, left- and right-finned!) Now you know.
Here's the paper  at PLoS ONE by Lee HJ et al.