In his poem Fish, D.H. Lawrence captured the essence of what it might feel like to be a fish: "Your life a sluice of sensation along your sides". If Lawrence were alive today, he’d learn that fishes’ sensations also include emotions. A new study led by Lynne Sneddon of the University of Liverpool has identified different personalities in rainbow trout [http://www.vetscite.org/publish/items/003369/index.html]. By observing the behavior of fishes in the face of novelty or social confrontation, some individuals were very confident, and others shy and fearful.

That may not be too surprising; after all, individual variation is an indispensable tool in evolution’s workshop. Sneddon’s key revelation was that fish personalities are labile. Bold fish who had won fights tended to be even bolder when later presented with a novel food item, whereas losing a fight tended to promote future cautiousness. Perhaps the most compelling finding involved a sort of social contagion: bold fish watching a shy fish investigate a mystery object showed much greater caution than usual when subsequently presented with a novel item.

In the same week that this study was published, another appeared which documents cooperation in two species of predatory reef fish. In the red sea, groupers recruit the help of moray eels to assist in hunting and catching smaller fish prey. Because each species can pursue prey where the other cannot (open water and crevices, respectively), by working together the complementary pair reduces a fleeing fish’s escape options. The arrangement is far from passive; check out the video clip at this link to see a grouper soliciting a moray eel by giving a distinctive head shake signal [http://www.eurekalert.org/pub_releases/2006-12/plos-fc120406.php].

These studies add to a growing body of evidence that fishes are nothing like the thoughtless, unfeeling automatons they were once thought to be. That’s no comfort to anyone concerned about humankind’s voracious plundering of the world’s fish populations, but nature has her own agenda, and easing humanity’s conscience isn’t on the list.